Research Activities
in
NTT Basic Research Laboratories
Volume 16
Fiscal 2005

September 2006
NTT Basic Research Laboratories,
Nippon Telegraph and Telephone Corporation (NTT)http://www.brl.ntt.co.jp/

DrainSource Source
Two-dimensional holechannel
0.1 µmDrain

Gate (Al)
SourceAu

Au
500 µmHigh-quality CVD Diamond Thin Layer
HPHT Diamond Single-Crystal Substrate

ドレイン

Gate

Diamond FET structure

Diamond FET（Gate width; 1mm）

Fine lines transferred to
SiO2 film.
Diamond FET（3mm x 3mm）

High-Power Operation of Diamond FETs in Gigahertz Range
Diamond semiconductor possesses exceptional properties for high-frequency high-power
characteristics. NTT fabricated diamond FET (field-effect transistor), which showed theworld’s highest RF output power density of 2.1 W/mm at 1 GHz. (Page 18)

SamplePeltier device
Filter
Air pump
N2 gas
Mist
Resist solution
Nebulizer

Setup.

Patterns formed on a cube.

Three-Dimensional Resist-coating Technique Using Fine Mist
and Nanopatterning on a Si Cube
We have developed a new technique for coating resist on a three-dimensional (3D) substrate
for 3D nanofabrication of various materials. A quasi-static ambient of a very fine mist ofresist solution is produced using a ultrasonic nebulizer. By putting a 3D substrate in theambient, resist film was successfully coated on it with good uniformity and small surface
roughness. 3D electron beam lithography on a SiO2/Si cube produced similar patterns on eachface of the cube. Moreover, a resolution 50 nm or less was confirmed by fine lines transferredto the SiO2 film. (Page 32)

Center part of device

Semiconductor chipon IC packageantenna gatehigh-frequency current
insulator

cmbarrierchannelGaAs

69,71Ga and 75As in a nanoscale area are used

Pulse current duration (ms)oscillating magnetic-field

5

3
2
1

4

4

2

5

3

1

backgatefrequency (MHz)Controlled Quantum Coherences of Nuclear Spins in a Nanoscale Device
Controlled quantum coherence of nuclear spins has been demonstrated by using asemiconductor point contact device. These figures show the semiconductor chip used in theexperiment, schematic diagram of the nanodevice incorporated inside, and color plot of thevariation in the resistance of the nanodevice measured near the NMR resonance frequency of
As. Various quantum-mechanical transitions between four states, which are typical of As, arecontrolled with high precision, and clear oscillation is observed.(Page 36)(a) Schematic and microscope image of nanocavity. (b) Calculated electromagnetic field
distribution. (c) Experimental resonant spectrum.

Ultrahigh-Q Photonic Crystal Nanocavity Realized with Locally
Modulated Line DefectIt is known that a “point defect” in a photonic crystal acts as an optical cavity and a “linedefect” acts as an optical waveguide. We found that a local weak width modulation of a line
defect can form an ultrasmall, ultrahigh-Q nanocavity. In the Si photonic crystal nanocavity
sample shown in the above figures, some of the holes surrounding the line defect are shiftedaway by several nanometers (too small to see in the figures) to create the cavity. The
nanocavity has overcome the experimental one million Q barrier for the first time. This was
believed to be impossible to achieve with photonic crystal cavities only a few years ago.
(Page 48)

From Science to Innovative Technology
We at NTT Basic Research Laboratories (BRL)
are extremely grateful for your interest and support
with respect to our research activities.
The missions of BRL are 1) to create newconcepts and guiding principles for network andinformation-processing technologies that will allow
us to overcome capacity and security related
limitations, and 2) to extend our knowledge of thescience and technology that will lead to medium andlong-term innovations. We believe that this willboth contribute to the success of NTT's business andpromote advances in science that will ultimately
benefit all mankind. To achieve these goals, wemust continuously deliver research output in atimely and well-directed manner. To this end, we
adopt a three-tier research theme classification withappropriate management strategies tailored for each:High-priority research: Work where speed is critically important and that is generally
pursued as strategic projects in collaboration with in-house or outside partners.



Exploratory research: Exploratory work that is likely to evolve into high-priority
research projects.

Innovative research: Work that goes beyond conventional technology to achieve
fundamental and innovative breakthroughs.

BRL's high-priority research themes are currently focused on quantum information
processing and nano-bio research. The former aims at clarifying the nature of electrons andphotons, which are the basis for the quantum mechanics of light and matter. The goal is todevelop practical applications such as quantum cryptography and quantum computing toovercome capacity and security limitations. By exploiting our expertise in quantum optics,
quantum solid-state physics, nano-fabrication, and other key technological areas, BRL has
achieved remarkable successes in unraveling the mysteries that lie behind a variety of systems
including quantum dots, superconducting devices, and cold atoms. Based on these achievements,
we are examining the practical viability of quantum cryptography and quantum computers incollaboration with many research institutes, both in Japan and overseas. The aim of ournano-bio research is to create a new area of science through the fusion of neuroscience,
biomolecular science, and nanotechnology. This should enable the realization of novel devices
that integrate molecular structures, proteins, and artificial nanostructures.
As an example of exploratory research, one project is investigating quantized mechanicalmotion in nanometer scale structures together with their quantum electronic properties. BRL
researchers are also undertaking exploratory work on techniques that will allow us tomanipulate nanostructures at will. These techniques include a method for cutting carbon
nanotubes at desired points. Researchers working on spintronics are seeking better

understanding and control of electron spin states with a view to achieving revolutionary
developments.
Lastly, we are also pursuing highly innovative research that has the groundbreaking potential
to overturn conventional technologies in the near future. The great progress made on
wide-bandgap semiconductors, single-electron devices, and photonic crystals convinces us thatthey will ultimately displace existing technologies.
To conduct these research activities, BRL is collaborating with many universities andresearch institutes in Japan, US, Europe, and Asia as well as other NTT laboratories. BRL also
regularly organizes international symposia and conferences at NTT Atsugi R&D Center. In
February 2006, we hosted the International Symposium on Mesoscopic Superconductivity andSpintronics, which attracted the participation of more than 100 researchers from around theworld. In October 2005, we sponsored the BRL School dedicated to students from abroad, witha special theme of Decoherence and Noise in Quantum Systems. We invited seven distinguishedresearchers as lecturers, giving young researchers from 17 countries the opportunity to learn
from the foremost authorities in these fields and share ideas with them. It gives us immense
pleasure to fulfill our mission of being an open laboratory in this way, and to disseminate ourresearch output throughout the world.
This report highlights the main achievements and research activities of NTT Basic ResearchLaboratories in 2005. We hope that it will help to promote awareness of the work undertaken at
NTT BRL, and enhance future collaboration.

Junji Yumoto
Director
NTT Basic Research Laboratories
3-1 Morinosato-Wakamiya, Atsugi,
Kangawa, 243-0198, Japan
Phone: +81 46 240 3300
Fax

: +81 46 270 2358

Contents
page

Member List ............................................................................................................................................... 1
I. Research Topics◆Overview of Research in Laboratories ................................................................................................... 17◆Materials Science Laboratory................................................................................................................. 18♦ High-Power Operation of Diamond FETs in Gigahertz Range♦ BGaN Micro-Islands for Growth of High-Quality GaN Films♦ High-Quality Hexagonal Boron Nitride Heteroepitaxial Layers Grown by Flow-Rate
Modulation Epitaxy♦ High-Temperature Operation of Nitride-Based HBTs
♦ Metal-Semiconductor Transition in Carbon Nanotubes Induced by Low-Energy Electron
Irradiation♦ Diameter-Controlled Growth of Carbon Nanotube Using Ferritin Catalysts♦ Strain Analysis of Si Nanolayers by Ultra-Small-Angle Grazing Incidence X-ray Diffraction♦ Electronic State of Molecular Devices at Room Temperature♦ Real Time H2O2 Imaging and Neuronal Cell Death♦ Static and Dynamic Structural Analysis of Biomolecules Using Atomic Force Microscopy♦ New Function of IP3 Receptor Binding Protein that Regulates pH♦ Single Molecule Photonics◆Physical Science Laboratory .................................................................................................................. 30♦ Theoretical Study on Material Dependence of Nano-Capacitance♦ Room-Temperature-Operating Digital-Analog Converter with Silicon Nanodevices♦ Three-Dimensional Resist-Coating Technique Using Fine Mist and Nanopatterning on a Si
Cube
♦ Force and Displacement Sensing Using the Superconducting Proximity Effect♦ Selective Spin Relaxation in a Quantum Dot♦ Two-Dimensional Electron Spin System Investigated by Nuclear Spin Measurements♦ Controlled Quantum Coherences of Nuclear Spins in a Nanoscale Device♦ Vacuum Rabi Oscillations in a Macroscopic Superconducting Qubit LC Oscillator System♦ Parametric Control of a Superconducting Flux Qubit♦ Trapping Atoms with a Superconducting Atom Chip
♦ Measurements of Magnetic-Domain-Wall Velocity Using Local Hall Effect♦ Gate Control of Electron Density and Electric Field in GaAs Quantum Well
◆Optical Science Laboratory .................................................................................................................... 42♦ Fast and Long-Distance Quantum Key Distribution Using Up-Conversion Detectors♦ Generation of Energy-Time Entangled Photon Pairs in 1.5-µm Band
♦ Coherent Single Electron Spin Control in a Slanting Zeeman Field♦ Optical Nonlinearity by Exciton-Biexciton Coherent Effects in Quantum Dots
♦ Nanoholes Formed by Reverse VLS Mechanism♦ Direct Measurement of the Carrier-Envelope Phase of a Few-Cycle Laser Pulse byInterference between Surface Harmonics♦ Ultrahigh-Q Photonic Crystal Nanocavity Realized with Locally Modulated Line Defect♦ All-Optical Flip-Flop Circuit Using Photonic Crystal Resonators♦ Adiabatic Wavelength Conversion via Dynamic Tuning of a Cavity

II. Data◆ Science Plaza 2005Fall .......................................................................................................................... 51◆ 3rd NTT-BRL School ............................................................................................................................ 52◆ International Symposium on "Mesoscopic Superconductivity and Spintronics 2006".......................... 53◆ Award Winners’ List .............................................................................................................................. 54◆In-house Award Winners’ List ................................................................................................................ 55◆List of Visitors’ Talks ............................................................................................................................. 57◆Research Activities of Basic Research Laboratories in 2005 ................................................................. 62◆List of Invited Talks at International Conferences ................................................................................. 64◆List of Research Papers Published in International Journals.................................................................. 72

Cover photograph:
Coherent Control of Nuclear Spins in a Semiconductor Nano-scale Device.
Nuclear spins in a nano-structure fabricated in gallium arsenide are controlled and detected all electrically.
Our approach enables the direct detection of (otherwise invisible) multiple quantum coherences between
levels separated by more than one quantum of spin angular momentum.
The color plot shows the time evolution of As spins under a radio-frequency irradiation.

Member List
As of March 31, 2006(*/ left NTT BRL in the middle of the year)

NTT Basic Research Laboratories
Director, Dr. Junji Yumoto (April 1, 2006 ~)Dr. Hideaki Takayanagi*

Research Planning Section

Senior Research Scientist, Supervisor,

Dr. Itaru Yokohama

Senior Research Scientist, Supervisor,

Dr. Akira Fujiwara

Senior Research Scientist,

Dr. Tadashi Nishikawa

NTT R&D Fellow
Prof. Yoshihisa Yamamoto(Stanford University, U.S.A)
Dr. Hideaki Takayanagi(Director, Bacic Research Laboratories)

NTT Research Professor
Prof. Masahito Ueda
(Tokyo Institute of Technology)
Dr. Fujio Shimizu(The University of Electro-Communications)
Prof. Yoshihisa Yamamoto*(Stanford University, U.S.A)
Prof. Shintaro Nomura(University of Tsukuba)Prof. Kyo Inoue(Osaka University)－ 1 －Materials Science Laboratory

Executive Manager,

Dr. Keiichi Torimitsu
Dr. Hisashi Sato
Dr. Katsuhiro Ajito Dr. Yuko Ueno
Dr. Isao Tomita
Dr. Rakchanok Rungsawang

Thin-Film Materials Research Group:
Dr. Toshiki Makimoto (Group Leader)
Dr. Makoto Kasu
Dr. Yasuyuki Kobayashi
Dr. Hiroyuki Shibata
Dr. Shin-ichi Karimoto
Dr. Kazuhide Kumakura
Dr. Kenji Ueda
Dr. Haitao Ye*
Dr. Atsushi Nishikawa
Low-Dimensional Nanomaterials Research Group:
Dr. Yoshihiro Kobayashi (Group Leader)
Dr. Fumihiko Maeda
Dr. Hiroki Hibino
Dr. Prabhakaran Kuniyil*
Dr. Hiroo Omi
Dr. Kenichi Kanzaki
Akio Tokura
Molecular and Bio Science Research Group:
Dr. Keiichi Torimitsu (Group Leader)
Dr. Keisuke Ebata
Dr. Kazuaki Furukawa
Dr. Nahoko Kasai
Dr. Akiyoshi Shimada
Dr. Hiroshi Nakashima
Touichiro Goto
Dr. Mime Kobayashi
Dr. Tobias Nyberg－ 2 －Dr. Hideki Yamamoto*Dr. Tetsuya Akasaka
Dr. Yoshitaka Taniyasu
Dr. Alexandre Tallaire

Dr. Kawamura Tomoaki
Dr. Satoru Suzuki
Dr. Jeong Goo-Hwan

Dr. Koji Sumitomo
Dr. Yoshiaki Kashimura
Dr. Chunxi Han*

Physical Science Laboratory

Executive Manager,

Dr. Yoshiro Hirayama
Dr. Hiroyuki Tamura
Takeshi Karasawa

Nanodevices Research Group:
Dr. Hiroshi Inokawa (Group Leader)
Dr. Masashi Uematsu
Dr. Yukinori Ono
Dr. Katsuhiko Nishiguchi
Dr. Nicolas Clement*

Dr. Hiroyuki Kageshima
Dr. Kazuyuki Uchida

Nanostructure Technology Research Group:
Dr. Hiroshi Yamaguchi (Group Leader)
Dr. Masao Nagase
Dr. Kenji Yamazaki
Junzo Hayashi
Dr. Hajime Okamoto

Toru Yamaguchi
Dr. Imran Mahboob

Quantum Solid State Physics Research Group:
Dr. Yoshiro Hirayama (Group Leader)
Dr. Toshimasa Fujisawa
Dr. Koji Muraki
Dr. Satoshi Sasaki
Dr. Akihito Taguchi*
Dr. Toshiaki Hayashi
Dr. Norio Kumada
Dr. Kei Takashina
Dr. Vincent Renard

Dr. Kiyoshi Kanisawa
Dr. Kyoichi Suzuki
Dr. Go Yusa*
Dr. Paula Giudici

Superconducting Quantum Physics Research Group:
Dr. Kouichi Semba (Group Leader)Dr. Hayato Nakano
Dr. Tetsuya Mukai
Dr. Shiro Saito
Dr. Kousuke Kakuyanagi
Dr. Alexander Kasper－3－

Hirotaka Tanaka
Dr. Taro Eichler*Spintronics Research Group:
Dr. Tatsushi Akazaki (Group Leader)
Dr. Yuichi Harada
Dr. Yoshiaki Sekine
Toshiyuki Kobayashi
Dr. Yuan-Liang Zhong－4－

Dr. Masumi YamaguchiOptical Science Laboratory

Executive Manager,

Dr. Yasuhiro Tokura
Dr. Masao Morita*
Dr. Makoto Yamashita

Quantum Optical State Control Research Group:
Dr. Yasuhiro Tokura (Group Leader)
Dr. Kaoru Shimizu
Kazuhiro Igeta
Dr. Hiroki Takesue
Dr. Fumiaki Morikoshi
Dr. Kiyoshi Tamaki
Dr. Akira Kawaguchi*
Quantum Optical Physics Research Group:
Dr. Hidetoshi Nakano (Group Leader)
Dr. Tetsuomi Sogawa
Hidehiko Kamada
Dr. Kouta Tateno
Dr. Takehiko Tawara
Dr. Atsushi Ishizawa
Dr. Haruki Sanada
Dr. Yasuaki Okano
Dr. Nicholas Cade
Photonic Nano-Structure Research Group:
Dr. Masaya Notomi (Group Leader)
Dr. Satoki Kawanishi
Dr. Atsushi Yokoo
Dr. Hideaki Taniyama
Dr. Akihiko Shinya
Dr. Masao Kato
Dr. Tetsu Ito*

－ 5 －Masami Kumagai
Toshimori Honjo
Dr. Jens Tobiska

Dr. Hideki Gotou
Katsuya Oguri
Dr. Stephen Hughes

Dr.Eiichi Kuramochi
Dr. Takasumi Tanabe

Distinguished Technical Member

Hiroshi Yamaguchi was born in Osaka on October 30, 1961. He received the B.E., M.S. inphysics and Ph.D. degrees in engineering from the Osaka University in 1984, 1986 and 1993,
respectively. He joined NTT Basic Research Laboratories in 1986. He was a visiting research
fellow in Imperial College, University of London, UK during 1995-1996. Since 1986 he has
engaged in the study of compound semiconductor surfaces prepared by molecular beam
epitaxy mainly using electron diffraction and scanning tunneling microscopy. His current
interests are mechanical and elastic properties of semiconductor low dimensional structures.
He is a research coordinator of NEDO international joint research project (Nano-elasticity)during 2001-2004, and also a guest professor in Department of Physics, Tohoku University
since 2005. He is a member of the Japan Society of Applied Physics and the Physical Societyof Japan. He was awarded the paper awards of the Japanese Society of Applied Physics in1989 and 2004.

Distinguished Technical Member

Toshimasa Fujisawa was born in Tokyo on May 23, 1963. He received the B.E., M.S. and Ph.D. degrees inelectrical engineering from Tokyo Institute of Technology in 1986, 1988 and 1991, respectively. He
joined NTT Basic Research Laboratories in 1991. He was a guest scientist in Delft University ofTechnology, Delft, the Netherlands during 1997-1998. Since 2003, he is also a guest associate professor atTokyo Institute of Technology. Since 1991 he has engaged in the study of semiconductor fine structuresfabricated by focused-ion-beam technique and electron-beam lithography technique, transportcharacteristics of semiconductor quantum dot. His current interests are single-electron dynamics inquantum dots, and their application to quantum information technologies. He received Sir Martin Wood
Prize in 2003 and JSPS (Japan Society for the Promotion of Science) Award in 2005. He is a member of theJapan Society of Applied Physics, and the Physical Society of Japan.
－6－

Distinguished Technical Member

Masaya Notomi was born in Kumamoto, Japan, on 16 February 1964. He received his B.E., M.E.
and Dr. Eng. degrees in applied physics from University of Tokyo, Tokyo, Japan in 1986, 1988,
and 1997, respectively. In 1988, he joined NTT Optoelectronics Laboratories. Since then, his
research interest has been to control the optical properties of materials and devices by using
artificial nanostructures, and engaged in research on semiconductor quantum wires/dots andphotonic crystal structures. He has been in NTT Basic Research Laboratories since 1999, and iscurrently working on light-propagation control by use of various types of photonic crystals. From
1996-1997, he was with Linköping University in Sweden as a visiting researcher. He is also aguest associate professor of Tokyo Institute of Technology (2003- ). He received 2006/2007
IEEE/LEOS Distinguished Lecturer Award. He is an associate editor of Japanese Journal ofApplied Physics. He is a member of the Japan Society of Applied Physics, the American PhysicalSociety, and IEEE/LEOS.

Distinguished Technical Member

Makoto Kasu was born in Tokyo on May 30, 1961. He received the B.E., M.S. and Ph.D. degrees
in Electrical Engineering from Kyoto University in 1985, 1987 and 1990, respectively. He joined
NTT Basic Research Laboratories in 1990. He was a guest scientist in University of Ulm,
Germany from 2002 to 2003. Since 1990 he has engaged in scanning tunneling microscope(STM)-based nanostructure fabrication, widegap semiconductors such as aluminum nitride (AlN)
and diamond. He received Electronic Materials Symposium (EMS) award for his nitride works.
He is a member of the Japan Society of Applied Physics, and the Institute of Electronics,
Information and Communication Engineers of Japan, the Surface Science Society of Japan. He is
the leader of SCOPE project "Diamond RF Power Devices for Microwave, Millimeter-Wave
Range Power Amplifiers" (from 2006 to 2011) of the Ministry of Internal Affairs andCommunications, Japan.

－ 7 －Advisory Board (2005 Fiscal Year)
Name

Title
Affiliation

Dr. Boris L. Altshuler

Professor
Department of Physics
Princeton University, U.S.A.

Dr. Michel H. Devoret

Professor
Department of Applied Physics
Yale University, U.S.A.

Dr. Serge Haroche

Professor
Department de Physique
De l’Ecole Normale Superieure, France

Dr. Mats Jonson

Professor
Department of Applied Physics
Chalmers University of Technology, Sweden

Dr. Anthony J. Leggett

Professor
Department of Physics
University of Illinois at Urbana-Champaign
U.S.A.

Dr. Johan E. Mooij

Professor
Department of Applied Physics
Delft University of Technology, The Netherlands

Dr. Klaus H. Ploog

Director
Paul-Drude-Institut für Festkörperelektronik
Germany

Dr. John F. Ryan

Professor
Clarendon Laboratory
University of Oxford, U.K.

Dr. Klaus von Klitzing

Professor
Max-Planck-Institut für Festkörperforschung
Germany－8－

Invited / Guest Scientists(2005 Fiscal Year)

Name

Affiliation
PeriodDr. Hiroshi Yaguchi

Kyoto University, Japan
December 03 – December 05

Dr. Jan Johansson

Japan Science and Technology Agency (JST), Japan
February 04 – January 06

Dr. Tobias Bergsten

Japan Science and Technology Agency (JST), Japan
April 04 – March 06

Dr. Satoshi Mitsugi

Tokyo Institute of Technology, Japan
April 05 – July 05

Dr. Hidetoshi Miyashita

University of Tokyo
April 05 – March 06

Dr. Shirou Kawabata

National Institute of Advanced Industrial Science andTechnology (AIST), Japan
April 05 – May 05

Dr. Stefan Fölsch

Paul Drude Institute for Solid-State Electronics, Germany
April 05

Prof. Rui-Rui Du

Rice University, U.S.A.
July 05 – August 05

Prof. Jian Chen

Nanjing University, R.O.C.
July 05 – August 05

Dr. Takaaki Koga

Hokkaido University, Japan
August 05 – July 06

Dr. Akio Tsukada

Tokyo University of Agriculture and Technology, Japan
June 05 – March 06

Dr. Chandra Ramanujan

University of Oxford, U.K.
October 05 – November 05－9－Dr. Go Yusa

Japan Science and Technology Agency (JST), Japan
October 05 – September 08

Dr. Yasuyoshi Miyamoto(Interchange Researcher)

NHK Science & Technical Research Laboratories, Japan
December 05 – November 06

Dr. Masaya Kataoka

University of Cambridge, U.K.
January 06

Prof. Yong-Hang Zhang

Arizona State University, U.S.A.
January 06 – July 06

Prof. Alexey Ustinov

University of Erlangen-Nürnberg, Germany
January 06 – March 06

Prof. Mats Jonson

Göteborg University, Sweden
February 06 – March 06

Prof. Eleanor Campbell

Göteborg University, Sweden
February 06 – March 06

Dr. Christopher Bäuerle

CNRS-CRTBT, France
February 06 – March 06

Dr. Fabio Taddei

Scuola Normale Superiore, Italy
February 06 – March 06－10－

Trainees(2005 Fiscal Year)

Name

Affiliation
PeriodFrank Deppe

Technische Universität München, Germany
May 02 – July 05

Simon Perraud

University of Paris 6 / CNRS, France
October 04 – September 07

Huang-Ming Lee

National Chiao Tung University, Taiwan R.O.C.
November 04 – November 05

Yueh-Chin Lin

National Chiao Tung University, Taiwan R.O.C.
November 04 – August 05
October 05 – January 06

Arnaud Valeille

SUPAERO (École Nationale Supérieure de L’aéronautiqueet de L’espace), France
January 05 – August 05

Wouter Naber

Delft University of Technology, The Netherlands
January 05 – June 05

Shih-Chieh Huang

National Chiao Tung University, Taiwan R.O.C.
February 05 – February 06
March 06 – September 06

Taryl Leaton Kirk

Universität Stuttgart, Germany
Max-Planck-Institut für Festkörperforschung, Germany
March 05 – April 05

Samir Etaki

Delft University of Technology, The Netherlands
April 05 – September 05

Rémi Rivière

INSA (Institut National des Sciences Appliquées deToulouse), France
May 05 – September 05－11－

Na Young Kim

Stanford University, U.S.A.
June 05 – June 05

Andreas Winkler

Darmustadt University of Technology, Germany
July 05 – December 05

Jennifer Chan

University of Oxford, U.K.
July 05 – August 05

Carole Planchette

ESPCI (Ecole Supérieure de Physique et de Chimine
Industrielles), France
July 05 – December 05

Pierrick Balestriere

ESPCI (Ecole Supérieure de Physique et de Chimine
Industrielles), France
July 05 – December 05

Rebeca Alonso“Miguel Hernández’’ University of Elche, Spain
January 06 – August 06

François Chabrol

University of Newcastle Upon Tyne, U.K.
January 06 – February 06

Jean-François Morizur

ENS (Ecole Normale Supérieure), France
February 06 – July 06

Raphael de Gail

ENS (Ecole Normale Supérieure), France
February 06 – August 06

François Parmentier

ENS (Ecole Normale Supérieure), France
February 06 – July 06

Benjamin Gaillard

INSA (Institut National des Sciences Appliquées deToulouse), France
February 06 – September 06

Wan-Cheng Zhang

Chinese Academy of Sciences, R.O.C.
February 06 – August 06－12－

Lars Tiemann

Max-Planck-Institut für Festkörperforschung, Germany
March 06 – June 06－13－

Japanese Students(2005 Fiscal Year)

Name

Affiliation (Period)

Yuichi Igarashi

University of Tokyo, Japan (Apr. 05 – Mar. 06)

Tomohiro Inoue

Osaka University, Japan (Jan. 06)

Shoko Utsunomiya

University of Tokyo, Japan (Jun. 05, Oct. 05－Mar. 06)

Kuniaki Endo

Tokyo University of Science, Japan (Apr. 05 – Mar. 06)

Akira Oiwa

University of Tokyo, Japan (Apr. 05 – Mar. 06)

Yohei Okubo

Hokkaido University, Japan (Aug. 05 – Sep. 05)

Satoru Ohno

Keio University, Japan (Apr. 05 – Mar. 06)

Hiroshi Okutani

Hokkaido University, Japan (Aug. 05 – Sep. 05)

Junya Ono

University of Tsukuba, Japan (Apr. 05 – Mar. 06)

Tatsuaki Orihara

Keio University, Japan (Jul. 05 – Aug. 05)

Kang Sunggu

University of Tsukuba, Japan (Apr. 05 – Mar. 06)

Koya Kitagawa

Tokyo University of Science, Japan (Apr. 05 – Mar. 06)

Yosuke Kitamura

University of Tokyo, Japan (Apr. 05 – Mar. 06)

Shuichiro Kihara

Waseda University, Japan (Jun. 05 – Mar. 06)

Tatsuya Kutsuzawa

Tokyo University of Science, Japan (Apr. 05 – Mar. 06)

Marika Gunji

Keio University, Japan (Apr. 05 – Mar. 06)

Tetsuo Kodera

University of Tokyo, Japan (Apr. 05 – Mar. 06)

Shingo Kondo

Tokai University, Japan (Apr. 05 – Mar. 06)

Kouta Sakakibara

Toyohashi University of Technology (Jan. 06 – Feb. 06)

Yosuke Sasaki

Tokyo Institute of Technology, Japan (Apr. 05 – Mar. 06)

Go ShinkaiTokyo Institute of Technology, Japan (Apr. 05 – Mar. 06)

Jun Sugawa

University of Tokyo, Japan (Apr. 05 – Mar. 06)

Hiroyuki Suzuki

University of Tokyo, Japan (Apr. 05 – Mar. 06)

Akihiro Souma

University of Tokyo, Japan (Apr. 05 – Mar. 06)

Atsushi Sogabe

Shonan Institute of Technology, Japan (Apr. 05 – Mar. 06)－14－

Toshitake Takahashi

Keio University, Japan (Apr. 05 – Mar. 06)

Masaya Tazawa

Tokyo University of Science, Japan (Apr. 05 – Mar. 06)

Shinya Tanaka

Toyohashi University of Technology (Jan. 06 – Feb. 06)

Masashi Tanaka

Nagaoka University of Technology (Oct. 05 – Feb. 06)

Daniel Ioan Moraru

Shizuoka University (Oct. 05 – Feb. 06)

Masaru Tsuchiya

Keio University, Japan (Apr. 05 – Aug. 05)

Katsuhiko Degawa

Tohoku University, Japan (Apr. 05)

Ritsuya Tomita

Tokyo Institute of Technology, Japan (Apr. 05 – Mar. 06)

Hiromasa Nakano

Tokyo University of Science, Japan (Apr. 05 – Mar. 06)

Tomohiro Nakamura

Shonan Institute of Technology, Japan (Apr. 05 – Mar. 06)

Masumi Noda

Tokyo University of Science, Japan (Apr. 05 – Mar. 06)

Junichi Hashimoto

Yokohama National University (Aug. 05 – Mar. 06)

Kenichi Hidachi

University of Tokyo, Japan (Aug. 05 – Mar. 06)

Yusuke Furukawa

University of Tokyo, Japan (Apr. 05 – Mar. 06)

Rumiko Horie

University of Tokyo, Japan (Apr. 05 – Sep. 05)

Munekazu Horikoshi

The University of Electro-Communications, Japan(Apr. 05 – Mar. 06)

Takahiro Horiguchi

Kyoto University (Nov. 05)

Kazuomi Masuhara

University of Tokyo, Japan (Oct. 05 – Mar. 06)

Tetsunori Matsumoto

Tokyo University of Science, Japan (Apr. 05 – Mar. 06)

Yuki Maruta

University of Tokyo, Japan (Oct. 05 – Mar. 06)

Kenji Miyakoshi

Tokyo University of Science, Japan (Apr. 05 – Mar. 06)

Hiroshi Miyazaki

Waseda University, Japan (Jun. 05 – Mar. 06)

Tetsuya Miyawaki

Tohoku University (Feb. 06 – Mar. 06)

Masakazu Morita

Tokyo Institute of Technology, Japan (Apr. 05 – Mar. 06)

Shin Yabuuchi

Keio University, Japan (Apr. 05 – Mar. 06)

Takao Yamaguchi

Tokai University (Aug. 05 – Mar. 06)

Michihisa Yamamoto

University of Tokyo, Japan (Apr. 05 – Mar. 06)－15－

Kazuhiro Watanabe

Osaka University (Oct. 05)－16－

Ⅰ．Research Topics

Research Activities in NTT Basic Research Laboratories Vol. 16 (September 2006)

Overview of Research in Laboratories
Materials Science Laboratory
Keiichi Torimitsu
The Materials Science Laboratory (MSL) aims at producing new functional materials anddesigning of advanced device based on novel materials and biological function. Controllingthe configuration and coupling of atoms and molecules is our approach to accomplish thesegoals. Bio-nano research is set as our principle research in this laboratory.
We have three research groups covering from inorganic materials, such as semiconductors,
to organic materials, such as neurotransmitters. The characteristic feature of MSL is theeffective sharing of the unique nanofabrication and measurement techniques of each group.
This enables fusion of research fields and techniques, which leads to innovative material
research for the IT society.
We set up European laboratory in UK for bio-nano research, our principal research, in lastyear and strengthen our research activities. We promote collaborations with internationalorganizations to develop a firm basis of basic science.
Physical Science Laboratory
Yoshiro Hirayama
We are studying solid-state quantum systems and nanodevices, which will have
revolutionary impact on communication and information technologies in the 21st century. In
particular, we are making firm and steady progress in the pursuit for solid-state qubits, andrelated physics and technology for future quantum information processing. We maintain an
open-door policy and engage in collaborations with many outside organizations to enhance
our basic research.
The five groups in our laboratory are working in the following areas: quantum coherent
control of semiconductor and superconductor systems, carrier interactions in semiconductor
hetero- and nanostructures, spintronics manipulating both electron and nuclear spins, precise
and dynamical control of single electrons, nanodevices operating at ultimately low power
consumption, atom traps, and novel nanomechanics based on compound semiconductors.
These studies are supported by cutting-edge nanolithography techniques, well-controlled
nanofabrication processes, high-quality crystal growth, and theoretical studies including firstprinciple calculations.
Optical Science Laboratory
Yasuhiro Tokura
This laboratory aims the development of core-technologies that will innovate in opticalcommunications and optical signal processing, and also seeks fundamental scientific progress.
The three groups in our laboratory are working for the quantum state control of light, thequantum state control of materials using light, the analysis of high speed phenomena using
very short pulse laser, the optical properties of semiconductor nano-structures, and very small
optical integrated circuit realized with two-dimensional photonic crystals.
This year, we made great strides in the speed of quantum cryptography, generation ofquantum entangled photon pairs, absolute control of carrier envelope phase, time-resolved
absorption spectrum with wide-band x-ray pulse, and realizing very low-loss wave-guide andvery high Q-value point-defect resonators.

－17－

Research Activities in NTT Basic Research Laboratories Vol. 16 (September 2006)

High-Power Operation of Diamond FETs in Gigahertz Range
Makoto Kasu and Kenji Ueda
Materials Science Laboratory
The data transfer rate in communications is increasing very rapidly. Therefore, electronic
devices that can operate in the gigahertz (GHz) range with higher output power are urgently
needed. Among semiconductor materials, diamond has the highest thermal conductivity andthe highest breakdown electric field. It also offers extremely high carrier mobility andsaturation drift velocity. Therefore, diamond electronic devices are expected to exhibit thebest performance in high-frequency and high-power operation.
Diamond films formed by the currently available growth techniques contain high-density
crystalline defects and impurities, so that it has been very difficult to obtain high-purity
diamond. Recently, we have developed technologies for the pre-growth treatment of thesubstrate surface and for CVD growth using highly pure methane source gas.
Figure 1 shows the diamond field-effect transistor (FET) structure. A diamondhomoepitaxial layer was grown by CVD on high-temperature high-pressure (HTHP)synthesized diamond substrate, and then a hole channel was formed near the surface byhydrogen surface passivation. Finally, using electron-beam lithography and self-alignment
technologies, a submicron-long Al gate was formed. Recently, by improving thesetechnologies, we were able to reduce the gap between the source and gate contacts to ~0.5 µm
and the gate length to 0.1 µm, which results in improvement of FET RF characteristics.
Figure 2 shows input-output power characteristics obtained at 1 GHz in the class-A
operation for a diamond FET with gate length (Lg) of 0.1 µm and gate width (Wg) of 100 µm.
The maximum output power density (Pout) was 2.1 W/mm, which is seven times higher thanthe highest value we reported previously and two times higher than that of GaAs FETs
commonly used in present systems. The linear power gain of 10.94 dB for a wide input power
range and the power-added efficiency (PAE) of 31.8% are similar to those of devices inpresent systems.
We are studying ways to boost the operating frequency and output power and, at the sametime, devoting much effort to improving the reliability of diamond FETs.
[1] M. Kasu, K. Ueda, H. Ye, Y. Yamauchi, et al., Electronics Letters 41 (2005) 1249.
[2] M. Kasu, K. Ueda, H. Ye, et al., Diamond and Related Materials 15 (2006) 783.

H-terminatedsurfaceO-terminatedsurfaceO-terminatedsurface

Gate (Al)
SourceAu
Holechannel

0.1 µmDrain
Au

CVD diamond homoepitaxial layer
HTHP (001) diamond substrate

Fig. 1. Cross section of diamond FET.

Fig. 2. RF power characteristics at 1 GHz.

－18－

Research Activities in NTT Basic Research Laboratories Vol. 16 (September 2006)

BGaN Micro-Islands for Growth of High-Quality GaN Films
Tetsuya Akasaka, Yasuyuki Kobayashi and Toshiki Makimoto
Materials Science Laboratory
Sapphire is attractive for a substrate of GaN growth, because it is inexpensive and has alarge area, compared with alternatives, such as SiC and GaN substrates. However, a large
number of crystal defects (threading dislocations) are formed in GaN films because of thelarge mismatches in the lattice constants and thermal expansion coefficients between GaN
and sapphire. In addition, GaN films grown on sapphire generally contain many residual
carriers and have low carrier mobilities. The techniques normally used to reduce crystal
defects in GaN or improve its electronic properties are complicated. A novel simple methodthat can solve these problems simultaneously is therefore highly desired. We have obtained
GaN films with low threading dislocation density (TDD) as well as with few residual carriers
and high mobility using BGaN micro-islands as novel buffers for the first time [1].
The BGaN (B~2%) formed micro-islands as shown in Fig. 1, because BGaN caused thephase separation due to the low solubility of B atoms in GaN. Such a three-dimensional
structure is not favorable for device application. However, epitaxial lateral overgrowth (ELO)of a GaN film on the BGaN micro-islands resulted in the smooth and continuous surface.
Figure 2 shows a cross-sectional transmission electron micrograph (X-TEM) for a GaN filmgrown using double layers of BGaN micro-islands. ELO of GaN reduced the TDD by twoorders of magnitude and the TDD near the GaN surface became 2x108 cm-2. Threading
dislocations were annihilated by bending and lateral propagation and by the formation of halfloops and fused dislocations. We confirmed that the residual carrier concentration in the GaN
film was very low. Using BGaN micro-islands, we fabricated an AlGaN/AlN/GaN
heterostructure, which is a basic component of GaN-based transistors. This heterostructure
exhibited two-dimensional electron gas mobility of 1910 cm2/Vs at room temperature, whichis among the highest ever reported for heterostructures on sapphire.
The present technique can grow GaN films with smooth surfaces, low TDD, and excellent
electronic properties on sapphire in just a single crystal growth process. Therefore, it is very
promising as a core technology for reducing the fabrication costs and prolonging the lifetimesof GaN-based transistors and light emitting devices.
[1] T. Akasaka and T. Makimoto, Jpn. J. Appl. Phys. (JJAP Express Letter) 44 (2005) L1506.

GaN

BGaN
BGaN

3 µm
Fig. 1. Scanning electron micrograph of
BGaN micro-islands.

3 µm

Sapphire

Fig. 2. X-TEM of a GaN film grown using BGaN
micro-islands.

－19－

Research Activities in NTT Basic Research Laboratories Vol. 16 (September 2006)

High-Quality Hexagonal Boron Nitride Heteroepitaxial Layers Grown by Flow-Rate
Modulation Epitaxy
Yasuyuki Kobayashi, Tetsuya Akasaka and Toshiki Makimoto
Materials Science Laboratory
Hexagonal boron nitride (h-BN) is one of the promising material systems for opticaldevice applications in the ultraviolet spectral region and for exciton-based quantum
information processing because of its wide bandgap and large exciton binding energies of
5.97 eV and 149 meV, respectively. However, a high-quality h-BN epitaxial layer on an
appropriate substrate has not been reported. Only a few papers have described the growth of
BN by conventional metalorganic vapor phase epitaxy (MOVPE), and there are many
unsolved fundamental problems.
One of the problems is the occurrence of gas phase parasitic reactions between group III
and V sources. It is expected that flow-rate modulation epitaxy (FME) is the most efficientmethod for reducing the parasitic reaction because the group III and V sources are alternately
supplied to the growing surface. The use of Ni (111) substrate could provide a high-quality hBN layers because the lattice constant of Ni (111) substrate is very close to the in-plane
constant of h-BN. Here, we demonstrated heteroepitaxial growth of h-BN on Ni (111)substrates for the first time using FME.
Figure 1 shows the growth-rate of BN grown by MOVPE and FME as a function ofammonia (NH3) flow-rate. For BN growth by MOVPE, the growth rate decreased
monotonically with increasing NH3 flow-rate. The growth rate of BN by FME decreased insmall steps with increasing NH3 flow-rate. However, the degree of the decrease in FME
growth was much smaller than that in MOVPE. These results indicate that FME can reduce
the parasitic reaction effectively [1]. Figure 2 shows the X-ray diffraction (XRD) patternobtained in a normal 2θ/ω configuration for h-BN on Ni (111) substrates grown by FME.
Apart from the substrate Ni (111) peak, the distinct sharp h-BN (0002) and weak (0004)
peaks from the (0001) planes of h-BN can be clearly observed, indicating that the film is puresingle-phase (0001) h-BN with the c axis normal to the Ni (111) surface [2].
The present results pave the way for future optical device applications.
[1] Y. Kobayashi and T. Makimoto, Jpn. J. Appl. Phys. 45 (2006) 3519.
[2] Y. Kobayashi et al. Abstracts of 13th International Conference on Metal Organic Vapor
Phase Epitaxy, Th-A1.1 (2006).

3
2.5

300

FME
200
100
0

3.5

2
1.5
1

MOVPE
0

0.5

0
100 200 300 400 500 600 700 800

Ni(111)
Intensity (arb. units)

Growth-rate (nm/h)

1ML/cycle
400

Growth-rate (A/cycle)

4

500

h-BN
(0002)

h-BN(0004)

20 25 30 35 40 45 50 55 60
2 Theta (Deg.)

NH3 flow-rate (ccm)Fig. 1. Growth-rate of BN films by MOVPE and
FME as a function of NH3 flow rate.

Fig. 2. XRD patterns of h-BN.

－20－

Research Activities in NTT Basic Research Laboratories Vol. 16 (September 2006)

High-Temperature Operation of Nitride-Based HBTs
Kazuhide Kumakura and Toshiki Makimoto
Materials Science Laboratory
Nitride-based semiconductors are promising materials for high-temperature or highvoltage operation devices because of their wide band gap. Heterojunction bipolar transistors(HBTs) are normally-off devices and can be operated with large current densities. Therefore,
nitride-based HBTs are expected to operate at high temperature and with high power.
However, dislocations or process-induced damage in nitride-based HBTs results in large
leakage current and low breakdown voltage.
We have developed a buffer layer for the growth of high-quality nitride-based
semiconductors on sapphire substrates [1]. Using the buffer layer and a low-damage etchingprocess, we have succeeded in the first operation of Pnp AlGaN/GaN HBTs with a commonemitter configuration. In order to clarify the transport mechanism at high-temperature, weinvestigated the current-voltage (I-V) characteristics of the Pnp HBTs at temperatures ranging
from room temperature (RT) to 590 °C.
We deposited Al2O3/graded-AlON/AlN/Al2O3 as a buffer layer on sapphire substrates byelectron cyclotron resonance (ECR) plasma sputtering at RT. The total layer thickness was 20
nm. Figure 1 shows the layer structure of the Pnp AlGaN/GaN HBTs grown on the substrateby metalorganic vapor phase epitaxy. Emitter and base mesas were defined by lithography
and ECR plasma etching. Pd/Au and Al/Au were used as the ohmic contact metals for the ptype and n-type layers, respectively.
Figure 2 shows the common-emitter I-V characteristics of the Pnp AlGaN/GaN HBT at
550 °C [2]. Good saturation properties were observed at this high-temperature and the leakage
current was less than 1 µA without the base current. The operation temperature is the highest
among semiconductor devices. The reason for this high-temperature operation is ascribed toour techniques for high-quality growth of nitride-based semiconductors and the low-damage
process. These results indicate that nitride-based HBTs are promising for high-powerelectronics.
[1] K. Kumakura, M. Hiroki, and T. Makimoto, Int. Workshop on Nitride Semiconductors
2004, P5.1, Pittsburgh, USA, 2004; J. Crystal Growth 292 (2006) 155-158.
[2] K. Kumakura and T. Makimoto, 2005 Int. Conference on Solid State Devices andMaterials, Kobe, Japan, I-6-2, 2005.
emitter electrodebase electroden-GaN base
GaN collector

collector
electrode

p-AlGaN/GaN SLs subcollector
GaN

Collector current (mA)p-AlGaN/GaN SLs
emitter-0.8

Al2O3/graded-AlON/AlN/Al2O3 bufferbase current = -20µA steps
550 °
C
-0.6

-0.4

-0.2

c-face sapphire substrate

00Fig. 1. Layer structure of the HBT.

Fig. 2. I-V characteristics at 550 °C.

-10

-20

-30

Collector-emitter bias (V)

－21－

-40

Research Activities in NTT Basic Research Laboratories Vol. 16 (September 2006)

Metal-Semiconductor Transition in Carbon Nanotubes Induced by Low-Energy Electron
Irradiation
Satoru Suzuki, Kenichi Kanzaki and Yoshihiro Kobayashi
Materials Science Laboratory
A carbon nanotube can be metallic or semiconducting depending on its chirality. The band
gap of semiconducting nanotubes strongly depends on their diameter. No technique has yet
been established for controlling the chirality and diameter. This is a big problem in terms ofnanotube applications for nanoelectronics. For example, a metallic nanotube does not work as
a field effect transistor (FET).
Recently, we have developed a simple technique for converting the electric properties of ametallic nanotube to semiconducting [1]. The gate characteristics of a single-walled carbon
nanotube (SWNT) FET at 28 K are shown in Fig. 1. The SWNT was originally metallic, sothat there was no off-region in the gate characteristics [panel (a)]. The oscillation of the
conductivity is caused by a Coulomb blockade specific to such a low temperature
measurement. When the device was irradiated by electrons of 1 keV up to a dose of ∼10-4
C/cm2, an off-region appeared [panel (b)]. Such gate characteristics are specific tosemiconducting SWNTs. Further irradiation widened the off-region [panel (c)]. The
irradiation-induced change of the gate characteristic is, in appearance, similar to the changethat would be caused by changing the chirality and diameter. Moreover, as shown in Fig. 2,
intensive irradiation finally makes a SWNT almost completely insulating [2]. These results
show that the electric properties of SWNTs can be widely changed from metallic to insulatingby controlling the irradiation dose. Defects created in the SWNTs by the irradiation play anessential role in the irradiation-induced electric property change [3,4].
[1] A. Vijayaraghavan et al., Nano Lett. 5 (2005) 1575.
[2] S. Suzuki et al., Jpn. J. Appl. Phys. 44 (2005) L1498.
[3] S. Suzuki et al., Jpn. J. Appl. Phys. 43 (2004) L1118.
[4] S. Suzuki et al., Jpn. J. Appl. Phys. 44 (2005) L133.
(a)
-6

10

SEM obs.

-7

10

(b)

line scan

-8

20 kV
290 pA

ID (A)

10

-9

10
10

-10

10

-11

10

-12

stop

(c)

0

50

100

150

Time (s)Fig. 1. Gate characteristic of the SWNT device
before and after the first and second
irradiation.

Fig. 2. Results of in-situ electric measurement of
the SWNT device during electron irradiation.

－22－

Research Activities in NTT Basic Research Laboratories Vol. 16 (September 2006)

Diameter-Controlled Growth of Carbon Nanotube Using Ferritin Catalysts
Goo-Hwan Jeong, Satoru Suzuki and Yoshihiro Kobayashi
Material Science Laboratory
The electrical properties of carbon nanotubes (CNT) are highly dependent on theirgeometric structures, such as their diameter or chirality. Thus, for the application of CNTbased nanoelectronics, it is essential to develop growth methods in which diameter orchirality can be controlled. Here, we introduce our recent work for diameter-controlled CNT
growth, in which we used catalytic nanoparticles instead of a thin-film catalyst [1].
As the catalyst source, we used ferritins, which are covered with protein shell and contain
Fe (ferritin) or Co clusters (Co-ferritin) in their core (6-8 nm in diameter). We also used Dps
protein, which contains Fe clusters in its core (4-nm in diameter). Catalytic nanoparticles
were obtained by calcination of ferritin-family molecules. We grew CNTs on flat or pillarpatterned substrates by means of ferritin-casting, calcination, and successive methane CVD.
Figure 1 shows a result of atomic force microscopy (AFM) measured after CNT growthusing ferritins and Co-ferritins [2]. Considering that the nanoparticles are 2-7 times larger
than the CNT diameter, we can suppose that thin CNTs grow from the large catalytic
nanoparticles. The inset is schematic illustration of the base-growth mechanism. Fe-catalyst
embedment in SiO2 substrates was confirmed by transmission electron microscopy.
The Raman profile and a scanning electron microscopy (SEM) image of a suspended CNT(inset) grown from Dps are shown in Fig. 2. From the Raman spectra, we know that the CNT
diameter is about 1 nm and that structural quality of the CNT is very high.
The results of size changes of ferritin-family catalysts and resultant CNT diameters are
summarized in Fig. 3. The ferritin-family molecules (10.2-4.0 nm) are changed to catalytic
nanoparticles (5.3-2.4 nm) by calcination and finally give rise to thin CNT (1.6-1.1 nm). We
found that the diameter differences between catalysts and CNT become smaller as the catalyst
size decreases. Further, the CNT diameter itself becomes smaller. These suggest that smaller
catalysts than those used in the present work will provide critical clues for diameter control of
CNTs. Investigating not only the catalyst behavior during CVD growth [3] but also the sizerelationship between catalysts and CNT is critical for diameter-controlled CNT growth.
[1] G. H. Jeong et al., J. Am. Chem. Soc. 127 (2005) 8238.
[2] G. H. Jeong et al., J. Appl. Phys. 98 (2005) 124311.
[3] G. H. Jeong et al., Chem. Phys. Lett. 422 (2006) 83.

Fig. 1. Size relationship between
catalysts and CNTs. Inset:
Schematic drawing of thegrowth feature.

Fig. 2. Raman profile of suspended
CNT grown from Dps. Inset:
SEM image of a suspended
CNT.
－23－

Fig. 3. Size changes of ferritinfamily catalysts and resultant
CNT diameters.

Research Activities in NTT Basic Research Laboratories Vol. 16 (September 2006)

Strain Analysis of Si Nanolayers by Ultra-Small-Angle Grazing Incidence
X-ray Diffraction
Hiroo Omi and Tomoaki Kawamura
Materials Science Laboratory
Nanoscale ultra-thin Si films exhibit quantum size effects when their thickness becomes
smaller than several nanometers. In order to control nanoscale silicon devices based on thequantum size effect, it is essential to achieve high-quality silicon nanolayers without strain
distribution. Ultrathin silicon nanolayers are usually fabricated by thermal oxidation and HF
etchback processes on silicon-on-insulator wafers. In this method, the silicon layers are
subjected to strain due to the difference in the thermal expansion coefficients between Si and
SiO2 during the thermal silicon oxidation. As a result, the strain significantly increases as thesilicon nanolayers become thinner, as has been observed by X-ray diffraction and Raman
spectroscopy. However, with these conventional apparatuses, we can only detect information
about the average lattice strain in the silicon nanolayers; it is difficult to detect information
about the localized strains existing on the surface of the thin silicon nanolayers or at the
Si/SiO2 interfaces.
We developed a new apparatus for grazing incidence X-ray diffraction (GIXD) using the
syncrotron radiation source at SPring-8 (Fig. 1) and established a method for evaluating suchspatially localized strain on a surface. The new apparatus can be used at the incident angle
below the critical angle of Si (0.18°). Consequently, for the first time, we succeeded in
detecting small strain localized on the surface of silicon nanolayers with this apparatus.
We probed in depth the strain on the surface of the Si nanolayers by changing the incident
angle of GIXD. The diffraction patterns obtained at the incidence angles of 0.01º and 0.1º are
originated from 2 nm and 6 nm in depth from the lattice of surface region (Fig. 2(a)). From theintensity analysis based on the two-layered-strain model (two layers with different states ofstrain), we found that the surface region of the silicon nanolayers has finite strain domains andthat the degree of the strain is on order of 10-4 (Fig. 2(b)). Moreover, by applying this method
to a thermally annealed sample, we found that a high annealing temperature of 1000ºC is
required in order to obtain uniform silicon nanolayers on which strain does not localize.
[1] H. Omi, et al., Appl. Phys. Lett. 86 (2005) 263112.

Fig. 1. Schematics of ultrasmall-angle GIXD.

Fig. 2. (a) Si(220) Bragg diffraction, (b) Two layer strain model.

－24－

Research Activities in NTT Basic Research Laboratories Vol. 16 (September 2006)

Electronic State of Molecular Devices at Room Temperature
Touichiro Goto and Yoshiaki Kashimura
Materials Science Laboratory

0.5
0.4
0.3
0.2
0.1
0
-0.1
-0.2
-0.3
-0.4
-0.5

OC6H13O

20
On/Off ratio:9 (Vd=0.1V)

H3C

0
HS

O
S

S
C6H13O

n=24

CH3

SH

Vg=-3VVd [V]

Id/Vd [nS]

Molecular devices with a few molecules have attracted considerable attention as next
generation electronic devices because of their high-density and low-power nature. The
characteristics of molecular devices can be tuned by controlling molecules. However, there
have only been a few reports about molecular devices operating at room temperature. In
addition, the instability of the junctions between electrodes and molecules has prevented
research on the characteristics of molecular devices.
In this study, we fabricated gold nanogap electrode devices with conjugated molecules.
Conjugated molecules have a functional group at each end, which selectively chemisorbs togold. First, we measured the electronic properties of molecular devices with terphenyldithiol(TPDT), which is 1.5 nm long. We observed a Coulomb diamond, i.e. the single-electron
charging effect, at room temperature [Fig. 1]. A simulation based on single-electron circuits
showed that the device characteristics can be explained on the basis of a multi-metallic-island
system. We consider that gold islands between the electrodes work as single-electron islands,
and TPDT bridging metallic islands and the electrodes work as tunnel junctions [1](Incooperation with Nanodevices Research Group).
Next, we synthesized rigid conjugated polymer poly(p-phenylene-ethynylene)s (PPEs)
with thioacetyl end groups (TA-PPE). TA-PPE self assembled in the gold nanogap electrodes(18-nm gap) and we measured its electronic properties. The room temperature current-voltage(conductance-voltage) characteristics exhibited periodic, repeatable, and identical stepwisefeatures [Fig. 2]. First-principle calculations based on the resonant tunneling effect suggestthat the equidistant steps result from the opening of different conducting channels that
correspond to the unoccupied molecular orbitals of TA-PPE [2].
It is intriguing that molecular devices show Coulomb diamond and quantized electronic
structures at room temperature. As the next stage, we will study the characteristics of
biomolecules in nanodevices.
[1] T. Goto et al., Jpn. J. Appl. Phys. 45 (2006) 4285.
[2] W. Hu et al., Phys. Rev. Lett. 96 (2006) 027801.

-6

-4

-2

0
Vg [V]

2

4

0
6 12
Id/Vd [nS]

Fig. 2. TA-PPE structure and current-voltage
characteristics at room temperature. The
solid lines are experimental results andthe broken lines are calculations.

Fig. 1. Conductance coutour plot of TPDT atroom temperature. The inset shows the
TPDT structure.

－25－

Research Activities in NTT Basic Research Laboratories Vol. 16 (September 2006)

Real Time H2O2 Imaging and Neuronal Cell Death
Nahoko Kasai, Chunxi Han, Akiyoshi Shimada, Tobias Nyberg and Keiichi Torimitsu
Materials Science Laboratory
Hydrogen peroxide (H2O2) has been recognized in association with the pathology ofneurological diseases because it is a by-product of a degenerative reaction of reactive oxygen
species, one of the major causes of oxidative stress in mammalian cells. Because it is relatively
stable comparing to the other reactive oxygen species, it has been used as a target molecule fordetecting oxidative stress.
Hippocampus has widely been examined and it is well understood that the epilepsy relates
to the cell death in its specific regions. We have recently found that by bicuculline (Bic),
GABAA receptor antagonist, also causes neuronal cell death in specific regions inhippocampus [1]. However little has been investigated on its details.
We have recently established a multichannel H2O2 monitoring system to monitor the realtime H2O2 distribution in a tissue. In this study, we examined the cell death caused by Bic interms of the oxidative stress [2].
We fabricated the sensor array, and we monitored the real time H2O2 distribution in a
cultured rat hippocampal slice placed on the array. When we introduced bicuculline into thesolution as a stimulant, in the presence of a catalase inhibitor, we could observe a distinct
increase in the H2O2 concentration (B) and increase in calcium influx (C) at the same regions
as neuronal cell death (D). This implies that the Bic causes cell death through oxidative stress.
This real time H2O2 distribution monitoring system will be a powerful tool with which to
explore the neuronal cell death mechanism in biological systems and to manage the neuronal
disorders.
[1] C. Han, N. Kasai, K. Torimitsu, NeuroReport 16 (2005) 333-336.
[2] N. Kasai, C. Han, K. Torimitsu, Sens. Act. B 107 (2005) 746-750.

Fig. By Bic application to a hippocampal slice (A), H2O2 release (B) and increase in Ca influx(C) were observed at the same region of the cell dearh (D).

－26－

Research Activities in NTT Basic Research Laboratories Vol. 16 (September 2006)

Static and Dynamic Structural Analysis of Biomolecules
Using Atomic Force Microscopy
Koji Sumitomo1, Mime Kobayashi1, Hiroshi Nakashima1, C. S. Ramanujan2, Keiichi
Torimitsu1, and J. F. Ryan2
1
Materials Science Laboratory, 2University of Oxford
To make a novel bio-nanodevice, uniting nanotechnology with biotechnology, it is vital toinvestigate individual biomolecular structures and dynamics at molecular-scale inphysiological conditions. Only then can we hope to understand how to control the functionsof such a device. Atomic force microscopy (AFM) is one of the most powerful tools toobserve the biomolecules in their native liquid environment. In this study, we successfully
visualized the static crystalline structures of membrane proteins and the dynamic molecularmotion of DNA by liquid-state AFM measurements.
Fig. 1(a) shows topographic AFM image of purple membrane patches on mica. We candistinguish either extracellular (EC) side or cytoplasmic (CP) side of purple membrane fromtheir surface morphology such as the smoothness and from the mechanical characteristics likethe stiffness. High-resolution AFM imaging clearly exhibits the 2D crystal ofbacteriorhodopsin (bR) protein in the purple membrane, as shown in Fig.1 (b). Recently, we
have succeeded in imaging the suspended membrane over artificially fabricated, nano-scale
cells on a silicon substrate (Fig. 1(c)). In its native cell membrane, the bR proteins functions
as a channel that opens by irradiation of light and pumps protons out of the cell through themembrane. This proton gating function, working on the nano-scale cell, has promising
applications in optoelectronic nanodevices [1]. We are now exploring the detailed correlation
between the conformational change and optical function of bR on the cell by AFM.
On the other hand, by using a high-speed AFM that is capable of catching video-rate
images, we have succeeded in observing biotinylated DNA binding to/dissociating from a
streptavidin protein [2]. High-speed imaging enables us to visualize the short DNA strands inmotion. We successfully captured real-time images of a biotin of the DNA end binding to a
streptavidin. The results indicate that high-speed scanning of AFM is potentially available forthe observation of biomolecular dynamic events such as chemical reaction or response toexternal stimuli in liquid.
Based on the combination of the static and dynamic analysis by AFM with electrochemical
approach, we are aiming to design and fabrication novel bio-nanodevices.
[1] K. Sumitomo et al., NTT Technical Review (in press).
[2] M. Kobayashi et al., Ultramicroscopy (in press).

(a) AFM image of purple membrane (b) High-resolution image of 2D
crystal of bR in purple
on mica.
membrane.
Fig. 1.
－27－(c) Nano-scale cell on silicon
substrate covered by purple
membrane.

Research Activities in NTT Basic Research Laboratories Vol. 16 (September 2006)

New Function of IP3 Receptor Binding Protein that Regulates pH
Ichiro Fujimoto1, Kyoko Shirakabe1, Hidetoshi Miyashita1, Katsuhiko Mikoshiba1,2,
and Keiichi Torimitsu1,31Divisions of Neural Signal Information NTT-IMSUT and 2Molecular Neurobiology, The
Institute of Medical Science, University of Tokyo, 3Materials Science Laboratory
The pH in the cell changes dynamically and the pH balance is regulated by carbon dioxide
in vivo. It is converted into bicarbonate and transported through the transmembrane, and thecellular pH is adjusted. Bicarbonate is mainly secreted from gland cells of pancreas and works
as an acid neutralizer in the stomach. Kidney cells control arterial blood pH. Several diseases
or conditions such as, glaucoma, cataract, cornea disease, stunted growth, and mental
retardation have been associated with the collapse of the pH balance.
Inositol 1,4,5-trisphosphate (IP3) receptors (IP3Rs) are IP3-gated Ca2+ channels located on
intracellular Ca2+ stores. We previously identified an IP3R binding protein, termed IRBIT(IP3R binding protein released with inositol 1,4,5-trisphosphate). Since IRBIT is released
from IP3R by physiological concentrations of IP3, we hypothesized that IRBIT is a signaling
molecule that is released from IP3R and regulates downstream target molecules in response to
the production of IP3. We therefore attempted to identify the target molecules of IRBIT in thisstudy and succeeded in identifying Na+/HCO3- cotransporter 1, NBC1, as an IRBIT binding
protein. Of the two major splicing variants of NBC1, pancreas-type NBC1 (pNBC1) andkidney-type NBC1 (kNBC1), IRBIT was found to specifically bind to pNBC1 and not to bindto kNBC1 at all. IRBIT binds to the N-terminal pNBC1-specific domain, and its binding isdependent on the phosphorylation of multiple serine residues of IRBIT.
Furthermore, an electrophysiological analysis in Xenopus oocytes revealed that pNBC1
requires co-expression of IRBIT to manifest substantial activity comparable to that of kNBC1,
which displays substantial activity independently of IRBIT. These results strongly suggestthat pNBC1 is the target molecule of IRBIT and that IRBIT plays an important role in pH
regulation through pNBC1.
In addition, our findings raise the possibility that the regulation through IRBIT enables
NBC1 variants to play different physiological roles.
[1] K. Shirakabe et al., Proc Natl Acad Sci USA 103 (2006) 9542-9547.

Fig. 1. New concept of signal information.

Fig. 2. Activation in Xenopus oocytes.

－28－

Research Activities in NTT Basic Research Laboratories Vol. 16 (September 2006)

Single Molecule Photonics
Katsuhiro Ajito1, Rakchanok Rungsawang1, Yuko Ueno2, and Isao Tomita3
1
Materials Science Laboratory,
2
NTT Microsystem Integration Laboratories, 3NTT Photonics Laboratories
Terahertz (THz, 1012 Hz) spectroscopy is used in the field of biological molecule analysis.
This is because information on weak inter- and intra-molecular interactions can be obtained as
low frequency vibration modes in the THz range. We showed that THz time-domain
spectroscopy (THz-TDS) using THz wave pulses has a wide spectral range and exhibits
sufficient sensitivity to molecules to be used as a tool in analytical chemistry. Furthermore,
we successfully characterized amino acids using the low frequency vibration modes thatappear in THz spectra.
Figure 1 shows the pulse width dependence of the THz absorption spectra of tryptophan, anessential amino acid, pumped by ultra-short pulse lasers. Since a mode-locked Ti:sapphirelaser is usually used to pump photoconductive dipole antennas for emitting and detecting THz
electromagnetic pulses in a THz-TDS system, the upper limit of the spectral range is related
to the pulse width of the pump laser. The use of ultrashort pulse lasers with pulse widths of 10
femtoseconds (fs) or less enables us to measure the spectral region expanded up to 5 THz andobtain more molecular information. Furthermore, we showed that THz spectroscopy isadvantageous for determining molecular orientation and molecular interaction by employing
the angle dependent THz-TDS spectroscopy of amino acid single crystals [1].
Moreover, when dried myoglobin was measured as a typical protein, there was anabsorption increase in the THz range corresponding to the myoglobin concentration as shownin Fig. 2 [2]. We can expect to acquire information about the hydrogen bonds related to thehigh order structure of proteins by controlling the protein water content. Moreover, further
development of a semiconductor THz-wave source employing difference frequency
generation [3] will be applied to the analysis of single biological molecules and imaging
measurement.
[1] R. Rungsawang, K. Ajito, Y. Ueno, I. Tomita, Extended Abstracts: International
Workshop on Terahertz Technology, Nov. 16-18, 199-200, 2005
[2] R. Rungsawang, Y. Ueno, H. Takenouchi, I. Tomita, K. Ajito, Proceedings of IRMMWTHz2005, Sep 19-23, Williamsburg (2005) 211-212.
[3] I. Tomita, H. Suzuki, H. Ito, H. Takenouchi, K. Ajito, R. Rungsawang, and Y. Ueno, Appl.
Phys. Lett. 88 (2006) 071118.

Fig. 1. Pulse-width dependence of THz absorption
spectra of tryptophan.

－29－

Fig. 2. Concentration dependence of THz spectraof myoglobin.

Research Activities in NTT Basic Research Laboratories Vol. 16 (September 2006)

Theoretical Study on Material Dependence of Nano-CapacitanceKazuyuki Uchida, Hiroyuki Kageshima and Hiroshi Inokawa
Physical Science Laboratory
It is expected that novel physics appear in nano-scale devices, while many studies areneeded to clarify such physics. For example, it is not clear what happens on the capacitancecharacteristics, one of the fundamental characteristics of FETs (field effect transistors), when
the device size is decreased in nano-scale. We developed a new method, the EFED (enforced
Fermi-energy difference) method, with which we can calculate the capacitance characteristics
from first principles if only we provide the atomic distribution and the element type for eachatom. We then applied the method for nano-capacitors and discussed physics in the nanocapacitance dependence on the material.
Since only the most stable electronic states are calculated in usual first-principles methods,
electrons distributed extensively in the system to screen the positive charges of the atomic
nucleus. To calculate capacitance characteristics, the electrons should be localized. We
divided the system’s space into two, and applied external virtual work on the two spaces toredistribute electrons. We minimize the total free energy for the electrons with this additional
work and obtained a Schrödinger equation for the electrons to polarize in the system. This is
the principle of our EFED method.
We applied this method on a nano-capacitor and calculated the dependence of thedifferencial capacitance on the Fermi energy difference. The system consists of repeatedparallel-planes with 3-atomic-layers films of SrTiO3(001). The inverse of the differencial
capacitance is shown in the vertical axis of Fig. 2. Classical capacitance of parallel planes iswritten as C = eS/d, which means that it depends only on the distance of the electrodes, d, andthe dielectric constant of the material between the electrodes, e. In nano-structure capacitors,
however, the electronic states of each electrode prefer to be discretized because of spacequantization and the Coulomb interaction between the electrons. Therefore, the capacitancestrongly depends on the difference of the Fermi energies as well as on the distance of theelectrodes and the material between the electrodes.
[1] K. Uchida, et al., e-J. Surf. Sci. & Nanotechnol. 3 (2005) 453.

Ti

Sr
total

O
anode

C–1 [HR/e2]

cathodeelectrostatic part1
anode part

∆ρ

anode

2

0

cathode
part
0

0.1

0.2

∆EF [HR]
Fig.1 SrTiO3 nano-capacitor.

Fig.2 Capacitance characteristics.

－30－

0.3

Research Activities in NTT Basic Research Laboratories Vol. 16 (September 2006)

Room-Temperature-Operating Digital-Analog Converterwith Silicon Nanodevices
Katsuhiko Nishiguchi1, Yukinori Ono1, Akira Fujiwara1,
Hiroshi Inokawa1* and Yasuo Takahashi2
1
Physical Science Laboratory, 2Hokkaido University
The single-electron turnstile, which transfers electrons one by one, is promising for ultralow-power-consuming circuits that treat one electron as 1 bit of information. As a step
towards to realize such a circuit, we have successfully demonstrated precise control ofelectron movement and detection of single electrons at room temperature using silicon
nanodevices [1]. In this work, we demonstrated a new data information circuit using thisdevice.
On a silicon-on-insulator wafer, we fabricated the silicon nanodevice, which can transfer anddetect single electrons (Fig. 1) [2]. The single-electron turnstile is composed of two wire-FETs.
A single-electron box (SEB) is electrically defined between the FETs. By turning on FET1 andFET2 alternately, the single electron is transferred to the memory node (MN) through the SEB(inset of Fig. 2). By repeating this transfer cycle, the electrons are transferred one by one. The
single electrons transferred into the MN are detected by an electrometer capacitively coupled to
the MN. The electrometer is carefully positioned close to the MN so that the sensitivity of theelectrometer is high enough to detect single electrons in the MN.
The size reduction of the SEB and optimization of the operating conditions provided
single-electron transfer with high speed (<10 ns) and precise detection (0.005 e/Hz0.5) at room
temperature. When the number of electrons with one transfer cycle is adjusted to be 0, 1, 2, or
4, this device serves as a digital-analog converter, in which binary 3-bit signals are converted
to the number of electrons in the MN and then to eight-level electrometer current. This is ademonstration of a new application using a single-electron-based architecture and means thatthe fabricated device is a basic component that can act as a bridge between conventional
binary signals and single-electron-based ones.
[1] K. Nishiguchi, et al., International Electron Devices Meeting (IEDM) (2004) 199.
[2] K. Nishiguchi, et al., Appl. Phys. Lett. 88 (2006) 183101.
[3] A. Fujiwara, et al., Appl. Phys. Lett. 84 (2004) 1323.
Present address: Shizuoka university（a） FET1 FET2Electrometer

Electron電子

Output Input

Transfer cycle(Electron)(Binary)Single-electron
turnstile 100nm(a) SEM image.

（b）

FET1 FET2
2nd
bit

1st
bit

Single-electron box Memory node
(SEB)
(MN)

0 1

(b) Schematic view of the single-electron turnstile.
Fig. 1.

2 3

7
6
5
4
3rd
bit 3
2
1
0

4 5 6
Time [s](111) 0.28
(110) 0.30(101)(100) 0.32(011)(010) 0.34(001) 0.36
(000)
0.38

Fig. 2. Single-electron digital-analog converter.
－31－

Electrometer current [nA]*Research Activities in NTT Basic Research Laboratories Vol. 16 (September 2006)

Three-Dimensional Resist-Coating Technique Using Fine Mist
and Nanopatterning on a Si Cube
Kenji Yamazaki and Hideo Namatsu*
Physical Science Laboratory
Creating three-dimensional (3D) structures with resolutions on the order of nanometers(i.e., 3D-nanofabrication) has been focused for various nanotechnology applications such as
NEMS (nano-electromechanical systems). We have already achieved 3D nanofabrication/
nanopatterning of resist material using electron beam lithography (EBL) and obtained aresolution as high as 10 nm and reasonable speed [1]. We have recently succeeded indeveloping a new resist-coating technique that enable us to apply the 3D technique to various
materials. In addition, we obtained good results on patterning and etching of a 3D-resistcoated Si cube.
Figure 1 shows the setup for our resist-coating technique. The ultrasonic nebulizer
produces a mist of resist solution, and only fine particles in the mist are transported to thesample chamber using N2 gas, resulting in quasi static ambient of very fine mist there.
Coating PMMA (polymethylmethacrylate) resist on a Si cube of 1 mm was investigated. We
found that the solvent of the resist solution, the temperature of the sample, and the flow rateof the transportation gas are important factors for uniformly coating resist with small surface
roughness on each face. For example, we found that methyl isobutyl ketone, which has lower
solubility for PMMA and thus provides smaller surface/interface energy, is a good solvent,and that careful adjustment of the temperature to around the dew point resulting in a thin filmof resist solution on the substrate. Errors of less than 50-60% in resist film thickness among
faces and within a face were obtained after optimizing the conditions [2]. Figure 2 (left)
shows the patterns delineated by EBL on different faces of a Si cube. It is clear that similar
patterns were fabricated on each face. Moreover, the patterns were transferred to SiO2 layer
by dry etching, and the resulting micrograph [Fig. 2 (right)] shows a resolution 50 nm or less.
This resist-coating technique enables us to coat resist on various 3D substrates, and thus
makes possible 3D nanofabrication with a high degree of freedom, combined with 3D EBL
and etching. Therefore, it promises to become a key technique for 3D nanotechnology.
[1] K. Yamazaki et al., Jpn. J. Appl. Phys. 43 (2004) L1111-L1113.
[2] K. Yamazaki and H. Namatsu, Tech. Digest 19th IEEE Conf. MEMS (2006) 254-257.
[3] K. Yamazaki and H. Namatsu, Jpn. J. Appl. Phys. 45 (2006) L403-L405.
*Present address: NTT-AT

SamplePeltier device
Filter
Air pump
N2 gas
Mist
Resist solution
Nebulizer

Fig. 1. Setup.

Fig. 2. Patterns formed on a cube (left) and fine lines transferred to SiO2 film(right).

－32－

Research Activities in NTT Basic Research Laboratories Vol. 16 (September 2006)

Force and Displacement Sensing Using the Superconducting
Proximity EffectHajime Okamoto, Tatsushi Akazaki and Hiroshi Yamaguchi
Physical Science Laboratory
Techniques for detecting small forces and displacements using semiconductor cantilevers
are being applied to various sensing tools, such as acceleration sensors, gas detectors, andatomic force microscopes. The detection is based on either optical or electrical methods. The
latter needs no external detectors like laser optics, which makes it very advantageous forminiaturization and integration. A notable self-sensor based on a purely electric method is thepiezoresistive cantilever, which detects its deflection as a change in the electrical resistance.
We have reported that piezoresistive cantilevers using semiconductor low-dimensional
structures enable highly sensitive detection of force and displacement due to the enhancementof piezoresistance caused by the quantum mechanical effect [1]. Recently, we fabricated a
new type of piezoresistive cantilever that integrates a superconductor-semiconductorsuperconductor junction [2]. Here, we describe mechanical sensing using the superconducting
proximity effect in this junction.
Figure 1a shows a scanning electron microscope image of the fabricated cantilever. The
cantilever is 200-µm long and 60-µm wide and contains a junction formed by thesuperconductor (Nb) and semiconductor (InAs) (Figs. 1b and 1c). At low temperature, asupercurrent flows between the Nb electrodes via the InAs layer, which is the superconducting
proximity effect. We found that the maximum supercurrent (the superconducting criticalcurrent) is modulated by the deflection of the cantilever. This indicates that, when the bias
current is set to the critical current value, the deflection of the cantilever induces a transition
between the superconducting state and the resistive state, providing a large resistance change,i.e., large piezoresistance. Low temperature measurements using a dilution refrigerator
revealed that the piezoresistance around the critical current (~327 mA) is larger than that in theresistive state by more than a factor of ten (Fig. 2). This suggests that small forces anddisplacements can be detected by using the transition between the superconducting state andresistive state.
[1] H. Yamaguchi, et al., Phys. Rev. Lett., 93 (2004) 036603.
[2] H. Okamoto, et al., Physica E, 32 (2006) 512.

Fig. 1. (a) SEM image of the fabricated cantileverand (b) a magnified view of the Nb-InAsNb junction. (c) Schematic of the crosssection of the junction.

Fig. 2. Dependence of the resonance characteris-tics(resistance change) on the bias current at 30 mK.
The quality factor (Q) is about 10,000.

－33－

Research Activities in NTT Basic Research Laboratories Vol. 16 (September 2006)

Selective Spin Relaxation in a Quantum Dot
Satoshi Sasaki, Toshimasa Fujisawa, Toshiaki Hayashi and Yoshiro Hirayama
Physical Science Laboratory
Coulomb interaction between electrons produces spin singlet and triplet states in asemiconductor quantum dot hosting an even number of electrons. We have measured the spin
relaxation time from a triplet excited state to a singlet ground state by applying fast pulse
signals to the gate electrode (electrical pump-and-probe), which reveals a selection rule forthe spin-orbit interaction.
Figure 1(a) shows the spin relaxation time, τs, as a function of the singlet (S)- triplet (T)energy difference, ∆ST, when the spin relaxation occurs via spin-orbit interaction followed byphonon emission. For ∆ST = 300 µeV, the number of tunneling electrons, nt, decays
exponentially as a function of the wait time, th, after an electron is injected to the triplet state,
as shown in the upper panel of Fig.1(b). The spin relaxation time is determined to be τs =160
µs for this case. When ∆ST is changed to 400 µeV by adjusting magnetic field, the triplet statecrosses another singlet state (S’) as schematically shown in the inset to Fig.1(a). Then, theinitial relaxation time drops to 60 µs and the decay characteristics is given by a double
exponential function as shown in the lower panel of Fig.1(b). This double exponential
behavior reflects the selection rule for the spin-orbit interaction which allows transition only
from SZ (z component of the spin) = ±1 states out of the three triplet sublevels. Then, theforbidden SZ = 0 triplet state involving opposite spins in two different orbitals can beextracted by waiting long enough time, th. This scheme could be utilized to obtain spin
entanglement state by separating the two electrons composing the SZ = 0 state.
[1] S. Sasaki et al., Phys. Rev. Lett. 95 (2005) 056803.
(b)(a) 600

Single exponential

400

160µs

τs(µs)

200
Energy
T
50

∆ST

S’
Level crossing

Double exponential

S
Magnetic field

200

60µs

810µs

400

∆ST (µeV)

Fig. 1. (a) Energy dependence of the spin
relaxation time.

－34－(b) Double exponential decay characteristics at
T-S’ crossing point compared with thenormal single exponential decay.

Research Activities in NTT Basic Research Laboratories Vol. 16 (September 2006)

Two-Dimensional Electron Spin System Investigated by
Nuclear Spin Measurements
Norio Kumada1, Katsushi Hashimoto2*, Koji Muraki1 and Yoshiro Hirayama1
1
Physical Science Laboratory, 2SORST-JST
Nuclear magnetic resonance (NMR) is a powerful technique to detect dynamic and static
properties of electron spins, and is commonly used not only in physics, but also in chemistry,
biology and medicine. For two-dimensional electron systems (2DESs) realized insemiconductor heterostructures, however, a small number of nuclei in contact with the 2DESand the overwhelming background due to the thick substrate have restricted thoseexperiments to multiple layer samples with fixed electron densities. To carry out nuclear spinmeasurements in a single density-tunable 2DES, we use a specific electronic state in aquantum Hall (QH) system, which allows for the current-induced nuclear spin polarization
and, at the same time, facilitates its resistive detection. With this new experimental technique,we can investigate various electronic states. Followings are recent results.
In a bilayer system consisting of two closely separated 2DESs, we investigate νtot=1 QH
state, which can be viewed as a superfluid of interlayer excitons. Nuclear spin-lattice
relaxation rate, which probes electron spin fluctuations, changes around the bilayer νtot=1 QH
state [Fig. 1(a)]. This result demonstrates that, as opposed to common assumption, theelectron spin degree of freedom is not completely frozen in the QH state [1]. Furthermore, weshow that the current-induced nuclear spin polarization in semiconductor heterostructures isstrongly modified by their potential inversion asymmetry (Fig. 2). This finding strongly
suggests that even a very weak spin-orbit interaction can play a dominant role in determining
the electron-nuclear spin coupling [2].
The experimental technique for the high-sensitive nuclear spin measurement established inthis work, and the new findings obtained by using the technique are important for future lowdimensional electric devices.
[1] N. Kumada et al., Phys. Rev. Lett. 94 (2005) 096802.
[2] K. Hashimoto et al., Phys. Rev. Lett. 94 (2005) 146601.
*

Present address: Hamburg University

Fig. 1. Nuclear spin relaxation rate around (a) bilayerνtot=1 and (b) single-layer ν=1/2 systems.

－35－

Fig. 2. Effects of potential asymmetry on thecurrent-induced nuclear spin polarization.

Research Activities in NTT Basic Research Laboratories Vol. 16 (September 2006)

Controlled Quantum Coherences of Nuclear Spins in a Nanoscale Device
Go Yusa*, Koji Muraki, Kei Takashina, Katsushi Hashimoto† and Yoshiro Hirayama
Physical Science Laboratory
The analytical technique of nuclear magnetic resonance (NMR) is based on coherent
quantum mechanical superposition of nuclear spin states. Recently, NMR has received
considerable renewed interest in the context of quantum computation and information
processing, which require controlled coherent qubit operations. However, standard NMR isnot suitable for the implementation of realistic scalable devices, which would require allelectrical control and the means to detect microscopic quantities of coherent nuclear spins.
Here we present a self-contained NMR semiconductor device that can control nuclear spins ina nanometer-scale region.
We has verified that strong interactions between electron and nuclear spins are produced
under certain conditions where two-dimensional electrons enclosed in GaAs quantum well hasa degenerate state between spin polarized and unpolarized n=2/3 states. This phenomenon has
been successfully applied to precision control of nuclear spins in a nanoscale semiconductor
device. The compactly integrated structure has opened the way for nuclear spin control with
unprecedented precision. The quantum-mechanical superposition between four separated
states peculiar to the nuclei of gallium (Ga) and arsenic (As) can be fully controlled in our
device.
The successful control of nuclear spin with a nanoscale device, which is notably an allelectrical control, is a significant step forward towards scalable nuclear spin quantum
computers. Our approach also enables the direct detection of (otherwise invisible) multiple
quantum coherences between levels separated by more than one quantum of spin angularmomentum. This microscopic high sensitivity NMR technique is thus especially suitable forprobing materials whose nuclei contain multiple spin levels, and may attractive as a nanoscale
NMR technology using an extremely small volume of material.
[1] G. Yusa, K. Muraki, K. Takashina, K. Hashimoto, and Y. Hirayama, Nature 434 (2005)
1001.
†

Present address: *Tohoku University, Hamburg University

Fig. 1. Color plot of resistance change DR as a function of pulse duration tP for 75As at three different intensities
B1, which is proportional to the square root of the output power Pr.f. from an r.f. generator. The
measurement was performed at B0=5.5T at 0.1K. DR, which is proportional to the magnetization of nuclear
spins, is color coded on a logarithmic scale for clarity. a: Pr.f.= 0 dBm, b: 13 dBm and c: 20 dBm.

－36－

Research Activities in NTT Basic Research Laboratories Vol. 16 (September 2006)

Vacuum Rabi Oscillations in a
Macroscopic Superconducting Qubit LC Oscillator System

1

Jan Johansson1, Shiro Saito1, Hayato Nakano1, Masahito Ueda2 and Kouichi Semba1
Physical Science Laboratory, 2Tokyo Institute of Technology/NTT Research Professor

Superconducting circuit containing Josephson junctions is one of the promising candidates
as a quantum bit (qubit) which is an essential ingredient for quantum computation [1]. A
three-junction flux qubit [2] is one of such candidates. On the basis of fundamental qubit
operations [3,4], the cavity QED like experiments are possible on a superconductor chip by
replacing an atom with a flux qubit, and a high-Q cavity with a superconducting LC-circuit(Fig.1). By measuring qubit state just after the resonant interaction with the LC harmonic
oscillator, we have succeeded in time domain experiment of vacuum Rabi oscillations,exchange of a single energy quantum (photon), in a superconducting flux qubit LC harmonic
oscillator coupled system [5]. The observed vacuum Rabi frequency 140 MHz is roughly 3×
103 (1×107) times larger than that of Rydberg (ordinary) atom coupled to a single photon in ahigh-Q cavity [6]. This is a direct evidence that a strong coupling condition can be rather
easily established in the case of macroscopic superconducting quantum circuit. It is explainedby the reasons that the circuit is huge compared with the atomic scale and also the supercurrent of µA order flows in the qubit. We have also obtained evidence of level quantizationof the superconducting LC circuit by observing the change in the quantum oscillation
frequency when the LC circuit was not initially in the vacuum state (Fig.2). We are also
considering this quantum LC oscillator as a quantum information bus by sharing it with many
flux qubits, then spatially separated qubits can be controlled by a set of microwave pulses justlike the method used in the quantum optics.
[1] F. Wilhelm and K. Semba, in "Physical Realizations of Quantum Computing: Are theDivincenzo Criteria Fulfilled in 2004?", (World Scientific Publishing Company; April, 2006)[2] J. E. Mooij et al., Science 285 (1999) 1036.
[3] T. Kutsuzawa et al., Appl. Phys. Lett. 87 (2005) 073501.
[4] S. Saito et al., Phys. Rev. Lett. 96 (2006) 107001.
[5] J. Johansson et al., Phys. Rev. Lett. 93 (2006) 127006.
[6] J. M. Raimond, M. Brune, and S. Haroche, Rev. Mod. Phys. 73(2001) 565.

Fig. 1. (a) Scanning Electron Micrograph of thesample (qubit, SQUID, and an on-chip LC
harmonic oscillator). (b) close-up view of aqubit and a SQUID detector (c) Equivalentcircuit of the sample.

Fig. 2. Rabi oscillations as a function of theduration of the flux bias shift pulse and theamplitude of an LC-oscillator weak resonant
pulse. The lowest two quantized Rabi
periods are observed.

－37－

Research Activities in NTT Basic Research Laboratories Vol. 16 (September 2006)

Parametric Control of a Superconducting Flux Qubit
1

Shiro Saito1, Masahito Ueda2, Hirotaka Tanaka1 and Kouichi Semba1
Physical Science Laboratory, 2Tokyo Institute of Technology/NTT Research Professor

350

(a)
VMW1 = 71.0 mV

Psw [%]

56.3
44.9
35.8
25.5
10

Fig. 1. Electron microscope image ofsuperconducting flux qubit.

20 30
t P [ns]40

VMW2 = 124.7 mV

(b)

300

MW1

ΩRabi / 2π [MHz]20

Quantum state engineering has become one of the most important areas in quantum
physics. In particular, the coherent control of quantum two-state systems, which areapplicable to quantum bits (qubits), has attracted increasing interest in the context of quantum
computing and quantum information processing. Of the recently realized solid-state qubits,
the superconducting flux qubit has the advantages of scalability and a long coherence time.
Multiphoton transitions have been demonstrated in the flux qubit [1]. In this study, weachieved the parametric control of a flux qubit by using two-frequency microwave pulses [2].
We observed Rabi oscillations stemming from parametric transitions between the qubit states
when the sum of the two microwave frequencies or the difference between them matched thequbit Larmor frequency fqb.
Our device is fabricated by lithographic techniques that define the structure of an inneraluminum loop forming a qubit and an outer enclosing dc-SQUID loop for the readout (seeFig. 1). Two currents circulationg in opposite directions in the qubit loop correspond to theground state |g〉 and an excited state |e〉 of the qubit. First a qubit operation is performed byapplying a two-frequency (fMW1 = 11.1 GHz, fMW2 = 18.5 GHz) microwave pulse of length tp
to the qubit (fqb = 7.4 GHz). After the operation, we immediately apply a dc readout pulse to
the dc-SQUID and measure whether or not the SQUID switches to a voltage state. By
repeating the measurement 8000 times, we obtain the SQUID switching probability Psw,
which is directly related to the probability with which we find the qubit in |e〉. Figure 2(a)shows the microwave amplitude of the MW1 VMW1 dependence of Rabi oscillations when the
microwave amplitude of the MW2 VMW2 is fixed at 50.1 mV. Figure 2(b) shows Rabi
frequencies WRabi/2p at various VMW1 and VMW2 values, which are well reproduced by Rabi
frequencies derived by using a semiclassical model.
By utilizing the parametric processes, we can control a qubit with much higher
frequencies than the qubit Larmor frequency. This implies that we can filter out the noisearound and lower than the qubit frequency from the microwave line by using a high-pass filter.
This will greatly improve qubit coherence.
[1] S. Saito, et al., Phys. Rev. Lett. 93 (2004) 037001.
[2] S. Saito, et al., Phys. Rev. Lett. 96 (2006) 107001.

250 e

79.1
MW2

200

62.9

g

150
50.1

100
50
0

Experiment
Theory020

40
60
VMW1 [mV]80

Fig. 2. (a) Rabi oscillations observed in the flux qubit. (b) Microwave
amplitude dependence of Rabi frequency. Inset is schematic ofparametric control.

－38－

Research Activities in NTT Basic Research Laboratories Vol. 16 (September 2006)

Trapping Atoms with a Superconducting Atom Chip
Tetsuya Mukai1, Alexander Kasper1 and Fujio Shimizu2
1
Physical Science Laboratory
2
University of Electro-Communications/NTT Research Professor
Neutral atoms have specific features suitable for realizing quantum computers/gates, e.g.
quantized internal states, indistinguishability, controllability of the atom-atom and atomphoton interactions, and very small influence from the environment. A promising approach isusing a pair of internal states of the atom as a unit of quantum computation (qubit). To realize
this "internal-state-qubit", making confinement of single atoms in 2- or 3-dimensional arrays
will be a key technique. In the world of atom optics experiments, making single atom traps isa challenging job because of the influence from a surface and current noise.
We are trying to achieve the atomic arrays with two different approaches: using lasers toform an optical lattice (3D) and employing magnetic micro traps formed by wires, i.e. atom
chip (2D). With the optical lattice approach, we have two original schemes: (i) double opticallattices [1], which is using two different atomic species trapped in independent optical lattices
with the same lattice constant, and (ii) an all optically controlled "lattice-in-cavity", whichuses a cavity mode as a bus for all qubits. With these methods we will be able to achieve auniversal set of gates with more than 1,000 qubits.
The atom chip approach is using our fine processing technique for making a 2-dimensional
array of atoms. An advantage of the atom chip, which is not possible with optical lattices, isthat we can control and address specific lattice sites, which is essential for future applications.
Our approach in addition allows us to overcome for example current noise problem by using
superconducting materials. We have constructed an apparatus combining two functions: aflux cryostat to cool a superconducting atom chip (Fig.1) and a laser/magnetic trap system topre cool and trap atoms. With this apparatus we have for the first time demonstrated thetrapping of atoms with magnetic potential generated by a superconducting current. Figure 2
represents the absorption images of atoms (a) before and (b) after trapping with a magnetic
potential (the brighter represents the higher atomic density). With this superconducting atom
chip technique we are going to make single atom traps in the vicinity of a surface as aresource for quantum computations.
[1] F. Shimizu, Jpn. J. Appl. Phys. 43 (2004) 8376.
a)Fig.1. MgB2 atom chip.

b)

Fig.2. Images (a) before and (b) after loading atoms on chip.

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Research Activities in NTT Basic Research Laboratories Vol. 16 (September 2006)

Measurements of Magnetic-Domain-Wall Velocity Using Local Hall EffectYoshiaki Sekine1 and Junsaku Nitta2,3Device Physics Laboratory1, Tohoku University2, CREST JST3The velocity of a magnetic domain wall (DW) in a NiFe wire has been obtained measuring
the time dependence of the stray fields from both ends of the wire. Logic devices utilizing
the motion of a DW were recently demonstrated and intensive investigations on the dynamics
of a DW have been carried out. In this study, we focus on the local Hall effect (LHE) todeduce the velocity of a DW because the LHE method has the advantages of large signal,
independency of the shapes of magnet, and flexibility of changing temperature. Using this
LHE method, the DW velocity of 250 m/s at 77 K has been obtained and these results areuseful for DW devices.
In the magnetization reversal process of a NiFe wire, a DW nucleates at one end of the wireand displaces to the other end. Then, the DW and annihilates at the other end. The
nucleation and annihilation of the DW result in the reverse of the direction of the stray field.
Therefore, time in which the DW passes through the wire corresponds to a period between
times when the directions of the stray fields from both ends of the wire change. Figures 1(a)and (b) shows a schematic cross-view and an optical microscopy image of the sample,
respectively. The stray fields from both ends of the wires with different length weredetected by the local Hall probes. We used an InGaAs two-dimensional electron gas and an
external field was applied parallel both to the wire and the 2DEG. Figure 2(a) shows thetime dependence of the Hall voltages, VH1 and -VH2, at 77 K. The rapid increase of VH
corresponds to the reverse of the stray field direction caused by the nucleation andannihilation of the DW. With increasing the length of the wire, the period between the
nucleation and annihilation times increases. The period (∆t) as a function of the wire length(L) is plotted in Fig. 2(b). The dotted line represents the velocity of 250 m/s. From thisrelation between ∆t and L, the DW velocity of 250 m/s is deduced. These results show the
LHE method is attractive for investigating the DW dynamics that is a key to DW devices.
[1] Y. Sekine and J. Nitta, in Narrow Gap Semiconductors, Inst. Phys. Conf. Ser. No 187,
edited by J. Kono and J. Léotin (Taylor & Francis, New York, 2006), p. 461.
(a)
NiFe

(a)
1.5

2DEG
(b)

1.0

VH1+

I+

VH1-

30 µm

150

∆t [nsec]+

VH [mV]-(b) 200

20 µm

100

0.5
10 µm

Hex
5 µm
VH2+

0
-600 -300

I-

VH2-

Fig. 1(a) a schematic cross-view(b) an optical microscopy
image of the sample. The
stray field is detected with
the InGaAs local Hall probe.

50

VH1
-VH2

0

t [nsec]

300

600

0

0 10 20 30 40 50

L [µm]

Fig. 2(a) the time dependence of VH. Rapid increases of VH correspondto the nucleation and annihilation of the DW. With increasing L,∆t increases. (b) ∆t as a function of L. The dotted line represents
the velocity of 250 m/s. From these results, the velocity of 250
m/s on NiFe is obtained.
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Research Activities in NTT Basic Research Laboratories Vol. 16 (September 2006)

Gate control of Electron Density and Electric Field in GaAs Quantum Well
Masumi Yamaguchi
Physical Science Laboratory
Producing an artificial crystal based on gate-confined semiconductor quantum dots requires
the ability to control the electron density and electric field. The electron density of the twodimensional electron system (2DES) formed at a semiconductor hetero-interface can bechanged by applying a front- or back-gate bias [1]. The change in the electron density isaccompanied by a change of the effective electric field since 2DES has a finite width along
the confinement direction. Although the transport properties are usually sensitive only to theelectron density, optical properties, such as the photoluminescence (PL), are sensitive to theelectric field as well as to the electron density. It is expected that the electron density andelectric fields of a semiconductor quantum well (QW) can be controlled independently byapplying front- and back-gate biases.
In this research, PL from an acceptor-delta-doped GaAs QW was measured while the gateelectric field was changed by applying front- and back-gate biases [2]. The sample structure isshown in Fig. 1. The open circles in the left panel of Fig. 1 denote the radiation energy of the
PL peak in changing the front-gate bias. The panels A, B, and C on the right show thesimulated conduction band profiles of the QW and the electron density. The front-gate bias
dependence of the radiation energy has three regimes, which reflect the situation of A, B, andC. A: The conduction electrons accumulate at both sides of the QW when positive high biases
are applied to both the front and back gates. In this case, the electric field in the middle part of
the QW is screened by the accumulated electrons and thus the PL peak energy weakly depends
on the gate biases. B: When the front-gate bias becomes small, the front-side electrons
disappear and electrons exist only at the rear side. In this case, the effective electric fieldchanges with changing the front-gate bias and the PL energy shifts largely. C: When the front
gate bias is decreased further, the QW becomes empty. The simulated energy shift (solid curvein the left panel) is in good agreement with the experimental results. In addition, we found thatthe electric field can be changed by keeping the electron density constant in the B regime.
[1] M. Yamaguchi, et al., Suf. Sci. 583 (2005) 94.
[2] M. Yamaguchi, et al., J. Appl. Phys. (to be published).

Fig. 1. PL energy shift and simulated results.

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Research Activities in NTT Basic Research Laboratories Vol. 16 (September 2006)

Fast and Long-Distance Quantum Key Distribution
Using Up-Conversion Detectors
Hiroki Takesue1, Toshimori Honjo1 and Kyo Inoue2
1
Optical Science Laboratory, 2Osaka University/NTT Research Professor
The differential phase shift quantum key distribution (DPS-QKD) protocol has been
attracting attention in recent years because of its robustness against strong attacks including aphoton number splitting attack [1]. Here we report a fast and long-distance DPS-QKD
experiment using single photon counters based on frequency up-conversion in periodicallypoled lithium niobate (PPLN) waveguides [2].
Fig. 1 (a) shows the experimental setup. A continuous lightwave from a laser is modulated
into pulses with a width of 100 ps and a 1-GHz repetition frequency using an intensity
modulator. Each pulse is randomly phase-modulated by {0,π} with a phase modulator, andattenuated by an optical attenuator to give an average photon number per pulse of around 0.2.
The pulse train is then transmitted over fiber spools and input into a 1-bit delayed MachZehnder interferometer based on planar lightwave circuit technology, whose two output ports
are connected to up-conversion detectors. The configuration of the up-conversion detector isshown in Fig. 1 (b). A 1.5-µm photon is combined with a 1.3-µm pump lightwave and theninput into a PPLN waveguide, where the 1.5-µm photon is converted into a 0.7-µm photon.
The converted photon are transmitted through an optical filter system to suppress noise
photons, and received by a silicon avalanche photodiode (Si-APD). Since an Si-APD can be
operated in a non-gated mode, we can significantly increase the key generation rate byemploying the up-conversion detectors in a fast clock QKD system.
We first set the quantum efficiency (QE) and the combined dark count rate (DC) at 9% and
26 kHz, respectively. The obtained secure key rates as function of fiber length are shown bysquares in Fig. 2. We have generated secure keys at a rate of 455 kbit/s over 20 km of fiber,
and also achieved 1-Mbit/s sifted key rate over 30 km of fiber. We then reduced the QE and
DC to 2% and 2.7 kHz, respectively, to improve signal to noise ratio. As a result, we havesuccessfully generated secure keys at a rate of 209 bit/s over 105 km fiber (the circle). The
triangles show the secure key rate of a BB84 QKD system reported in [3]. Thus, we havesignificantly increased both secure key rate and distribution distance.
This result is an important step toward realization of long-distance QKD systems.
[1] K. Inoue et al., Phys. Rev. Lett. 89 (2002) 037902.
[2] H. Takesue et al., New J. Phys. 7 (2005) 232.
[3] C. Gobby et al., Electron Lett. 40 (2004) 25.

Fig. 1. Experimental setup.

Fig.2. Secure key rate.

－42－Research Activities in NTT Basic Research Laboratories Vol. 16 (September 2006)

Generation of Energy-Time Entangled Photon Pairs in 1.5-µm Band1

Toshimori Honjo1, Hiroki Takesue1 and Kyo Inoue2
Optical Science Laboratory, 2Osaka University/NTT Research Professor

The generation of entangled photon pairs in the 1.5-µm telecom band is essential for
quantum communication over optical fiber networks[1, 2]. In this paper, we report thegeneration of 1.5-µm band energy-time entanglement using a periodically poled lithium
niobate (PPLN) waveguide and a two-photon interference experiment using a planar
lightwave circuit (PLC) [3].
Figure 1 shows the experimental setup. A continuous wave light from a laser diode with awavelength of 780 nm was used as a pump light. The light was polarization controlled andthen launched into a PPLN waveguide. Frequency degenerated photon pairs were generated in
the PPLN at around 1560 nm by the spontaneous parametric down conversion process. Afterthe PPLN, the light was filtered to suppress the 780-nm pump light and was also filtered by a1560-nm band pass filter to reduce the dispersion in the PLC interferometer. The entangled
photon pairs were launched into a 3-dB fiber coupler, which separated the signal and idler
with 50% probability. The signal and idler photons were launched into a planar lightwave
circuit (PLC) Mach-Zehnder interferometer. The phase difference between the two paths was
precisely adjusted by controlling the temperature of the interferometer and stable operation
was possible. Photon detectors based on an InGaAs APD were set at each output of the MachZehnder interferometer. The output signals of the photon detectors were input into a timeinterval analyzer (TIA) to measure the coincidence. We used this setup to perform a twophoton interference experiment. In this experiment, we fixed the temperature of the PLC
interferometer for the signal and changed that for the idler, and measured the coincidence.
Figure 2 shows the experimental results. The triangles indicate the experimentally obtainedcoincidence rate per detected signal photon for each temperature. The count rate of eachdetector was ~1700 cps throughout the measurement. Although the count rates remained, we
observed a deep modulation of the coincidence rate as we changed the temperature. We
obtained coincidence fringes with 77.3% visibilities without subtracting the accidental
coincidences. Considering both the estimated average number of photon pairs per gate of 0.12
and their Poisson distribution, the visibility of the setup was theoretically estimated to be
77.4%, which means energy-time entanglement was confirmed and very few noise photons
were generated by the pump light.
[1] I. Marcikic et al., Phys. Rev. Lett. 82 (1999) 2594.
[2] H. Takesue et al., Phys. Rev. A 72 (2005) 041804(R).
[3] T. Honjo et al., CLEO/QELS 2006 (2006) JTuA5.
780-nmBand
Pass
FilterCoincidence rate per signal countLaser(780nm)780-nmSuppression
PPLN Filter(*)
Polarization
Controller

Detector1
50:50
Splitter

Time
Interval
Analyzer(*)
1560-nm
Band
Pass
Filter

Detector2
PLC
Mach-ZehnderInterferometer

0.00100.00050.0000Fig. 1. Experimental setup.

24

25
Temp. (deg.)

Fig.2. Coincidence fringe.

－43－

26

Research Activities in NTT Basic Research Laboratories Vol. 16 (September 2006)

Coherent Single Electron Spin Control in a Slanting Zeeman Field
Yasuhiro Tokura
Optical Science Laboratory
Stimulated by electron-spin-based proposals for quantum computation, a growing interest
has emerged in realizing the coherent manipulation of a single electron spin in a solid-state
environment. The application of the electron’s spin—rather than its charge—as a quantum bit(qubit) is motivated by its potentially long coherence time in solids and the fact that itcomprises a natural two-level system. Single electron spin resonance (SESR) plays a key role
in realizing electron-spin-qubit rotation, however had not been detected in semiconductor
quantum dots (QDs) so far, because of the necessary high-frequency (10 GHz) selective
magnetic field in a cryogenic (100 mK) setup. Waveguides and microwave cavities as used inconventional ESR cause serious heating, limiting the operation temperature to 1 K.
We propose a new SESR scheme that eliminates the need for an externally applied acmagnetic field, and with the potential of very high and tunable quality factors. An ac voltage
is applied to let an electron in a QD oscillate under a static slanting Zeeman field. Thiseffectively provides the electron spin with the necessary time-dependent magnetic field. Notethe analogy with the Stern-Gerlach experiment, where the spin and orbital degrees of freedom
are coupled by employing an inhomogenous magnetic field. The spatial oscillation of theelectron within the QD involves the hybridization of orbital states.
We estimated expected coherence time of this qubit and demonstrated that single-qubit
rotation and the controlled-NOT operation are possible. This qubit is easier to manipulate
than a spin qubit and has a better quality factor than a charge qubit. The concept is generaland can be applied to a range of systems, such as single wall carbon nanotubes, GaAs, andSiGe QDs. This scheme also allows for the measurement ofthe intrinsic single electron spin
coherence time.
[1] Y. Tokura et al., Phys. Rev. Lett. 96 (2006) 047202.

Fig. 1. Model: Ferromagnetic gate electrodes are located at either end of the
dot and are magnetically polarized in the plus or minus x direction,
creating a magnetic field gradient bSL. A uniform magnetic field B0
is applied in the z direction. The spin in the dot is controlled byapplying an oscillating voltage Vac between the two gates.
Fig. 2. (a) Relaxation rate 1/T1 in a GaAs QD as function of external
magnetic field B0 due to different phonon scattering mechanisms:
deformation potential (dashed line), longitudinal (dotted line) andtransversal (dash-dotted line) piezoelectric. The solid line is thetotal. (b) B0 dependence of the quality factor Q for a single-qubit
operation.

－44－

Research Activities in NTT Basic Research Laboratories Vol. 16 (September 2006)

Optical Nonlinearity by Exciton-Biexciton Coherent Effects
in Quantum Dots
Hideki Gotoh and Hidehiko Kamada
Optical Science Laboratory
Quantum dots have been attracting much attention because of their distinctive excitonbiexciton physics and important contribution to quantum information processes. In quantum
dots, excitons and biexcitons (combined two excitons) stably exist due to the confinement
effects in nanometer-scale structures. The stable excitons can induce coherent interactions
with biexcitons. These coherent interactions provide quantum correlation effects as well as
strong nonlinear optical effects like electromagnetically induced transparency (EIT), which
are very useful in quantum information processing and conventional optical devices.
We found the strong optical nonlinearity in exciton absorption in zero-dimensional
InGaAs quantum dots by using single-dot photoluminescence excitation (PLE) spectroscopy.
This nonlinearity was caused by a coherent interaction between an exciton (X) and abiexciton (XX) [1, 2].
Figure 1 shows PLE spectra of X and XX for different excitation intensities. PLEs
correspond to absorption spectra. With a low excitation, peak-shaped spectra can be seen in X
and XX. With a high excitation, XX PLE spectrum exhibits usual peak-shaped with abroadened linewidth. In contrast, the X PLE has an unusual spectral shape with dip-shaped
structure. The PLE almost disappears at the exciton resonance. A large coherent effectbetween X and XX yielded this unusual PLE. These coherent effects can be interpreted interms of EIT. To examine the coherent effects for optical nonlinearities, we performed apump and probe measurement. PL signals from an X and a XX were detected with two beams
through an interferometer. Figure 2 shows the X and XX PL intensities as a function of
excitation intensity. The XX PL increases with pump power and saturates above 300 µW. In
contrast, the X PL increases up to 100 µW and decreases with pump power. This decreasing
region reflects large coherent effects between the X and XX states. Our results reveal that an
EIT-like optical nonlinearity is achieved by the coherent interaction.
Our results constitute an important milestone for the quantum computing and will assist
the development of novel optical device functions.
[1] H. Gotoh et al., Phys. Rev. B71 (2005) 195334.
[2] H. Gotoh et al., Appl. Phys. Lett. 87 (2005) 102101.
∆ PL Intensity (arb. unit)

1mW
Intensity (arb.unit)

XX

X
0.05
X
XX

Pump

200
100

XX

Probe
Sample

0
X
-100
500
1000
Pump Power (µW)

1.665
1.670
1.675
Photon Energy (eV)Fig. 1. PLE spectra for two excitation powers.

－45－

Fig. 2. Nonlinear PL intensity.

1500

Research Activities in NTT Basic Research Laboratories Vol. 16 (September 2006)

Nanoholes Formed by Reverse VLS Mechanism
Kouta Tateno, Hideki Gotoh and Hidetoshi Nakano
Optical Science Research Laboratory
There are several kinds of nanohole fabrication techniques suitable for nano-scale devices.
Anodic oxidation of aluminum produces an elegant array of highly ordered nanoholes with ahigh aspect ratio. For semiconductors in nanohole fabrication, electron beam lithography
and reactive ion etching (RIE) have been researched, especially for silicon-on-insulator (SOI)
substrates for two-dimensional photonic crystals. Here, we report a new nanohole
fabrication method using Au particles. This method is based on the reverse VLS (vaporliquid-solid) mechanism.
The VLS mechanism is well known as the growth mechanism for free-standing
semiconductor nanowires. The point of the VLS growth is to use the liquid-state metal alloy
particles as catalysts at low temperature around 400 - 500˚ C. In the case of GaAs using Au
particles as catalysts, the liquid Au particles maintain constant Ga and As concentrations in athermodynamically balanced vapor-liquid-solid system so that the growth occurs when Ga
and As are supplied and super-saturation occurs in the Au alloy particles. The concept of
the reverse VLS process (etching) as follows: Ga and As are removed from the particles bysupplying an etching source gas, at the boundary between the Au particle and the substrate,
Ga and As dissolve continuously from the substrate to maintain their concentrations in theparticle, and it turns out that Au particles dig into the substrate to make holes. We were able
to successfully demonstrate smooth holes in GaAs and InP substrates by the reverse VLS
mechanism for the first time [1].
The etching was carried out in a low-pressure (76 Torr) horizontal MOVPE reactor. Carbon
tetrabromide (CBr4) was the etching source (5×10-6 mol/min). AsH3 and PH3 were thegroup-V sources (2×10-3 mol/min) and were supplied around the etching temperature. Audeposited GaAs and InP substrates were used for etching. For the InP samples, PH3 wasalso supplied during the etching to reduce the etching rate.
The nanohole formation tends to proceed in the [111]B direction. For GaAs, straightholes sometimes appear in the [011] (as shown in Fig. 1) and [211]B directions. This is dueto the stable {111}B facets, which block the etching. For InP, many straight holes are seenin the [111]B direction as shown in Fig. 2. For both materials, direct etching of the surface
also occurs. It is therefore necessary to find the optimum etching conditions for highselectivity to fabricate nanoholes. This hole-fabrication method is very promising for
application to various types of nano-devices and is expected to contribute to nano-science and-technology.
[1] K. Tateno et al., Jpn. J. Appl. Phys. 44 (2005) L428.

200 nm[011]

1000 nm

200 nmFig. 1. Cross-sectional SEM images of [011]oriented hole in GaAs (111)A.

Fig. 2. Cross-sectional SEM images of [111]B
oriented hole in InP (111)A.
－46－

Research Activities in NTT Basic Research Laboratories Vol. 16 (September 2006)

Direct Measurement of the Carrier-Envelope Phase of a Few-Cycle Laser Pulse byInterference between Surface Harmonics
Atsushi Ishizawa and Hidetoshi Nakano
Optical Science Laboratory
The carrier-envelope phase (CEP) is the phase of the carrier wave at the maximum of theenvelope. The timing of the oscillation cycles within a light pulse plays a role in theinteraction of light with matter when the duration of the pulse becomes comparable to thelight oscillation period. Therefore, it is necessary to control the CEP of few-cycle laser pulses
in order to apply nonlinear spectroscopy.
To date, it has been observed that high-order harmonic generation [1] and above-thresholdionization are sensitive to the CEP. Almost all previous direct measurements of the CEP haverelied on strong-field processes using 100-µJ amplified laser pulses, which are available only
at low repetition rates in a vacuum chamber equipped with a specialized detector. Therefore,
only a few laboratories have been able to measure the CEP.
We demonstrated a measurement that provides direct information about the CEP of a fewcycle laser pulse. In any f -to-2f or 2 f -to-3f spectrum interferogram method using a nonlinear
crystal, there is a certain unknown phase shift in the measured value because of the linear
dispersion in the SHG crystal. We have devised a way of directly measuring the CEP using
the interference between the second and third harmonics from the surface of a solid. Bothharmonics have a π/2 phase shift relative to the fundamental optical field when they are
generated from the surface of a solid. This means the interference signals do not include a
constant offset phase component and can therefore be used to measure the CEP directly. Thismethod uses pulses with a low energy of less than 1 µJ, and it’s very easy to set up theequipment and perform the measurement in air. The spectrum of the laser pulse is shown in
Fig. 1. In this experiment, a 5-fs 1-µJ laser pulse was focused on a glass target at the incident
angle of 45° . Even and odd harmonics were generated due to the broken symmetry of aninterface. The second and third harmonic spectrums overlap in the ultra-violet region. Figure
2 shows a series of interference signals of different phases. The signals cyclically move up
and down with the CEP, which has a period of 2 π rad. We will be able to achieve
stabilization of the CEP of a few-cycle amplified laser pulse by detecting it using this method.
[1] A. Baltuška, et al., Nature. 421 (2003) 611.
[2] A. Ishizawa and H. Nakano, Jpn. J. Appl. Phys. 45 (2006) 4087.
CEP (rad)

1000

100

π

2π

1.0
Intensity (a.u.)

Intensity (a.u.)0

500 600 700 800 900 1000
1/2 Wavelength (nm)
1/3

0.8
0.6
0.4
0.2
0.0

Fig. 1 Measured spectrum of a few-cycle
laser pulse.

0

200
400
600
800
Wedge displacement (µm)

Fig. 2 Dependence of the CEP on the interference
intensity.

－47－

Research Activities in NTT Basic Research Laboratories Vol. 16 (September 2006)

Ultrahigh-Q Photonic Crystal Nanocavity Realized with Locally Modulated Line DefectEiichi Kuramochi, Takasumi Tanabe, Akihiko Shinya and Masaya Notomi
Optical Science Laboratory
An advantage of photonic crystal (PC) nanocavities is compatibility of a high quality
factor (Q) with an ultra-small mode volume (V) [1].. A higher Q has been demanded in orderto enhance device performance [2,3] and decrease the device insertion loss resulting from thereduction in transmittance caused by cavity-waveguide coupling. Although intensive studies
have raised the theoretical Q value to 106 [1], a further increase will be difficult to achieveusing conventional approaches.
A new scheme for realizing a higher Q PC nanocavity involves a Fabry-Perot cavity
composed of a loss-less line-defect mode and two mode-gap mirrors [4]. The use of a modegap mirror instead of a photonic bandgap (PC) mirror greatly reduces the out-of-plane loss
from the cavity because of the smooth and gradual decay of the electromagnetic field in themode-gap barrier region. We have found that such a mode-gap can be generated bymodulating the line-defect width [1]. In this study, we designed a nanocavity in which holes
around the cavity center were shifted away from a line defect. In addition, we employed atapered shift structure (this 3-stage structure is shown in Fig. 1) in which a gradual change ofline-defect width enhanced the advantage of the mode-gap mirror. Numerical studies with the
3D finite difference time domain method revealed that the 3-stage structure can achieve an
ultrahigh-Q (108) with an ultrasmall V (1.7 (λ/n)3 ). Next, we fabricated this structure in a Si
PC slab by using electron beam lithography [5]. The intensity spectrum of the cavity resonantmode is shown in Fig. 2. The ultranarrow linewidth (1.5 pm) corresponded to a Q of 1.0×106.
In summary, our newly designed cavity has increased the theoretical Q value by twoorders of magnitude and we achieved an experimental Q of one million for the first time as aPC-based nanocavity [6]. The Q achieved here is sufficiently high for many device
applications and this report is a first step towards adding new functions (optical buffering andoptical delay) to PC-based devices.
[1] M. Notomi et al., Opt. Express 12 (2004) 1551.
[2] M. Notomi et al., Opt. Express 13 (2005) 2678.
[3] T. Tanabe et al., Opt. Lett. 30 (2005) 2575.
[4] E. Kuramochi et al., Appl. Phys. Lett. 88 (2006) 041112.
[5] E. Kuramochi et al., Phys. Rev. B72 (2005) 161318(R).
[6] E. Kuramochi et al., LEOS2005, PD1.1 (2005).
B
B

C
B

A

108

C
B

A

C
B

C

Line defect
C

B

A
B

C
C

A
B

C

B
B

C

C

Hole shift
A x
B 2x/3
C x/3

C
C

107

106

105

0

Fig. 1. Schematic and SEM image.

Intensity (a. u.)CCCTheoretical Q

C

1.5pm
Q=1.0x106

1558.20 1558.21 1558.22 1558.23
Wavelength (nm)

6

12

18

Shift x [nm]2430Fig. 2. Theoretical Q and resonant spectrum.

－48－

Research Activities in NTT Basic Research Laboratories Vol. 16 (September 2006)

All-Optical Flip-Flop Circuit Using Photonic Crystal Resonators
Akihiko Shinya, Takasumi Tanabe, Eiichi Kuramochi, Satoki Kawanishi and Masaya Notomi
Optical Science Laboratory
An all-optical flip-flop circuit will be needed in future all-optical high-speed signal
circuits. A flip-flop circuit is a digital circuit that temporarily memorizes past input/output
information, and processes it with present input signals. These functions are indispensable interms of achieving all-optical regeneration functions. One of the most important functions isto synchronize the output pulses with the system clock. Although several successful alloptical circuits have already been proposed, their operating speed is not very fast due to theirlarge circuit size.
To overcome this problem, we used a two-dimensional photonic crystal (PhC), which has
attracted attention as a platform on which to construct devices with dimensions of a few
wavelengths of light. Figure 1 shows the schematic structure of our flip-flop circuit based on
a 2D-PhC with a triangular air-hole lattice [1]. The lattice constant a is 400 nm, and the airhole diameter is 0.55a. The two resonators (C1, C2) have one identical resonant wavelength(λ2) and two different resonant wavelengths (λ1 and λ3 for C1 and C2, respectively). The
waveguides (WG1, WG2) are tuned so that the λ1 and λ3 lights can propagate in both WG1and WG2, and the λ2 light can propagate only in WG1.
Here, we consider a situation where the input data (DATA: λ2 = 1548 nm) with a nonreturn-to-zero (NRZ) format deviates from the internal system clock. In order to synchronize
the data and the clock, we set all the input powers of the λ1, λ2 and λ3 lights at 60 mW to
employ the bistable operation of C1 and C2, and used two signals as internal system clocks( CLOCK : λ3 = 1463 nm, CLOCK : λ1 = 1493 nm). We simulated our system with the 2DFDTD method taking account of the Kerr effect of the PhC material (AlGaAs).
Figure 2 shows the calculated time charts of our system. This figure shows that our system
outputs the AND signal between the ideal DATA (dotted line) and the CLOCK. That is, thissystem can synchronize the DATA with the CLOCK and regenerate the ideal DATA with areturn-to-zero format. The system response time is about 10 ps, which means our system canoperate with a 50 GHz clock.
The result is the first step towards all-optical digital processing.
[1] A. Shinya, S. Mitsugi, T. Tanabe, M. Notomi, I. Yokohama, H. Takara, and S. Kawanishi,
Optics Express 14 (2006) 1230

Fig. 1. Schematic structure of flip-flop circuit.

Fig. 2. Time chart of our system.

－49－

Research Activities in NTT Basic Research Laboratories Vol. 16 (September 2006)

Adiabatic Wavelength Conversion via Dynamic Tuning of a Cavity
Masaya Notomi
Optical Physics Laboratory"Wavelength" is one of the most important characteristics of light, which has been
employed in various optical technology, such as wavelength-demultiplexing communication.
Though it is not so difficult to generate light with a particular wavelength using a tunable laser,
it is not easy to change the wavelength after generated. Usually, we make use of high-order
optically-induced electronic polarization in some special crystals to convert the wavelength.
However, this nonlinear process requires high optical intensity. Very recently, we found that
we can linearly convert the wavelength of light by a fundamentally different mechanism.
This novel conversion process is described as follows: First, we prepare a light pulse in ahigh-Q cavity, and then we dynamically change the resonant wavelength of the cavity withina time scale shorter than the photon lifetime of the cavity. As a result of the dynamic
parameter tuning process, the wavelength of light in the cavity follows the changed resonant
wavelength of the cavity. We have confirmed this phenomenon by numerical experiments forrealistic Si photonic crystal high-Q cavities, as shown in Fig. 1. This phenomenon is purely
linear, thus it does not depend on the optical intensity of the signal light, and 100%
conversion efficiency is possible regardless of the intensity, which are quite different fromconventional nonlinear wavelength conversion. In fact, this process is equivalent to aparameter tuning process in a classical oscillator, such as a guitar (suppose that plucking a
guitar code and then screwing a peg before the sound is dying out). Although the process isvery simple, it has been difficult to realize in the optical regime because the light velocity is
generally too fast and the decay time is too short. And only recently this becomes meaningful
after the recent rapid technical advance in high-Q microcavities. We have also confirmed that
so-called adiabatic invariant (the energy divided by the frequency) is preserved all throughthis process, proving that it is a adiabatic tuning process.
In future, we plan to experimentally demonstrate some of important characteristics of thiswavelength conversion process, such as wavelength conversion of few photons.
[1] M. Notomi and S. Mitsugi, Phys. Rev. A73 (2006) 051803(R).

Fig. 1. (a) Schematic of Si photonic crystal cavity assumed for the calculation. (b) Dynamic change of therefractive index as a function of time. (c) Calculated wavelength spectra with and without dynamic
tuning.

－50－

Ⅱ．DataResearch Activities in NTT Basic Research Laboratories Vol. 16 (September 2006)

Science Plaza 2005Fall"Science Plaza 2005Fall" was held at NTT Atsugi R&D Center on Friday, October 28th,
2005. Entitled "Nanoscience Opens Up the Quantum World", the Science Plaza symposiums
have been implemented with the aim of bringing together various people from inside andoutside of NTT while gathering diverse opinions through discussions on our latest researchaccomplishments.
At Science Plaza 2005Fall, following an opening address from the laboratory chief, Dr.
Takayanagi, brief summaries of each exhibited poster were given in the form of shortpresentations. After lunch, symposium lectures were given by three distinguished technicalmembers of NTT Basic Research Laboratories. The lecture topics and respective presenterswere "Current status and outlook for diamond FETs as high-frequency power devises" by
Makoto Kasu, "Micro/nanotechnology and quantum effects" by Koji Yamaguchi, and"Single-electron dynamics" by Toshimasa Fujisawa. Each lecture was well-attended and was
followed by enthusiastic question-and-answer sessions.
As regards the poster exhibits, 27 posters presenting our latest research accomplishments
were displayed. While explaining the originality and impact—as well as the future
prospects—of our research accomplishments in detail, these poster sessions generated pretty
intense discussions on the research topics, and many meaningful opinions were received. At
the video screening, promotion videos summarizing some typical research topics were shownin a short, easy-to-understand manner along with footage from some previously hosted
international symposiums. This year’s "Lab tour"—an inspection of the research facilities at
NTT BRL that has been highly appraised over the years—took in four destinations and was
repeated a total of five times during the day. Care was taken to ensure that anybody wishing toattend the tour could do so. After all the lectures, presentations, and exhibitions werecompleted, a banquet was held in the research center’s dining room, becoming a place for themeaningful discussions during which the various guests could deep their mutual relations.
More than 200 people from research institutes, universities, and general industries, as well
as from NTT Group, attended Science Plaza 2005Fall, and thanks to the efforts of all those
who attended, the conference could end on a high note. We would thus like sincerely express
our gratitude to all the attendees.

－51－

Research Activities in NTT Basic Research Laboratories Vol. 16 (September 2006)

3rd NTT-BRL School
The third NTT-Basic Research Laboratories (BRL) school was held during the period of
October 31-November 4, 2005, at the NTT Atsugi R&D Center. The aim of the NTT-BRL
school is to foster young researchers in the field of physics field and to promote theinternational visibility of NTT BRL. This year the theme selected was "Noise andDecoherence in Quantum Systems", which is closely related to the research on quantum
information processing that NTT BRL is now conducting intensively. Seven prestigious
professors were invited to the school as lecturers. Thirty-four participants, mainly Ph. D
students, gathered from seventeen countries.
On the first day, after the director and the managers of NTT BRL presented an overview
of NTT BRL, Prof. Boris Altshuler (Columbia University, USA) gave a lecture entitled"Introduction to Theory of Mesoscopic Systems". On the second day, there were two lectures,"Quantum Transport and Electron Dephasing in Diffusive Metal Wires" by Prof. Norman
Birge (Michigan State University, USA) and "Decoherence in the Josephson Charge Qubits"
by Dr. Oleg Astafiev (NEC, Japan), both including the recent topic of the experimental
research. Following them, Prof. Yuri Galperin (University of Oslo, Norway) gave a talk on"Decoherence in Metallic Conductors and Mesoscopic Devices (theory)". In the morning of
the third day, a laboratory tour was conducted so that the students could enjoy looking at the
research facilities and activities at NTT BRL. After the afternoon lecture by Prof. Leonid
Levitov (MIT, USA) "Quantum Noise and Counting Statistics", the poster session was held in
the evening, where each student gave a presentation about his/her research at university.
On the last two days, we had three lectures: "Quantum Shot Noise Probing Interactions
and Magic Properties of the Fermi Sea" by Prof. Christian Glattli (ENS, France),"Mesoscopics in Quantum Dots" by Prof. Charles Marcus (Harvard University, USA), and"Transport in Arrays of Quantum Dots" by Prof. Valerii Vinokur (Argonne National
Laboratories, USA). In the final talk, thedirector of NTT-BRL, Hideaki Takaynagi
talked about "Readout of Superconducting
flux quits". At the farewell party, bestposter prizes were awarded to the students
who gave prominent presentations. The
students were able to network and build
friendships while exchanging their contact
addresses. NTT BRL will continue toprovide these kinds of occasions to foster
young researchers and build human
networks in the field of physics.

－52－

Research Activities in NTT Basic Research Laboratories Vol. 16 (September 2006)

International Symposium on"Mesoscopic Superconductivity and Spintronics 2006"
From February 27 to March 2, NTT Basic Research Laboratories (NTT BRL) andCREST-JST held an international symposium on physics entitled "Mesoscopic
Superconductivity and Spintronics" (MS+S2006) at NTT Atsugi R&D Center. These fields
have recently been attracting considerable attention from scientific researchers and engineers
because they are fundamental areas that may lead to the physical realization of quantum
information processing and computation. Many distinguished researchers in these fields fromall over the world have joined every event of this series of symposium and given importantpresentations. It is now recognized as an important international symposium on mesoscopic.
MS+S2006 included 46 oral presentations and approximately 80 poster presentations.
At the symposium this year, we were impressed by the fact that mesoscopic
superconductivity is attracting attention in terms of applications in addition to the academic
interest. Professor J. Martinis, Professor F. W. J. Hekking, Professor D. Esteve, Professor J.
Clark, Professor C. J. P. M. Harmans, Dr. K. Semba, Dr. Y. Nakamura, Dr. Wallraff, andProfessor A. Ustinov gave talks on new results in their superconducting qubits(SQubits)
experiments. These people represent almost all the research groups throughout the world that
actually have SQubits in operation. In particular, Professor J. Martinis's group in UCSB has
had a greatest success. They observed two-quantum-bit entanglement and provided thequantum tomography charts of their system. On the other hand, the Yale Univ. group showed
the entanglement between their SQubit and a transmission line resonator, and the NTT BRL
group demonstrated entanglement manipulation of their SQubit and a sub-millimeter LC
resonance circuit coupled system, which is known as "vacuum Rabi oscillation". These twostudies are the first clear demonstrations of entanglement in macroscopic quantum objects.
We also found that rapid progress is being made in spintronics. In particular, electricalways of manipulating spins in semiconductor systems generated great interest in this
symposium. A talk on the generation and detection of spin entanglement in double quantum
dots was presented by Professor C. Marcus of Harvard University. Dr. S. Sasaki of NTT BRL
described a gate-controlled RKKY interaction in a double quantum dot-quantum wire coupledsystem. Much attention has focused on the spin-orbit interaction in semiconductors. Professor
D. Awschalom of UCSB demonstrated optical detection of the spin Hall effect in GaAs and
InGaAs. Gate control of spin precession in InGaAs 2DEGs (two-dimensional electron gases)
was reported by Professor J. Nitta of Tohoku University. Professor H. Ohno of Tohoku Univ.
observed current-induced domain wall motion in GaMnAs.
Midway through the symposium, a special lecture on entanglement manipulations withtrapped ions was given by Dr. H. Haffner of Innsbruck. Most participants were surprised by
the admirable skill shown in manipulating ions although they were not very familiar with thesystem.
The symposium welcomed
approximately 200 participants,of whom a quarter were fromoverseas. They have now returned
home with the dream of fruitfulinteraction between fundamental
physics and information sciences,which will become common in
the near future.

－53－

Research Activities in NTT Basic Research Laboratories Vol. 16 (September 2006)

Award Winners’ List (Fiscal 2005)

International
Symposium on
Photonic andElectromagnetic
Crystal Structures(PECS-VI)
Best Paper Award

E. Kuramochi
M. Notomi
S. Hughes
G. KiraL. Ramunno
A. Shinya
T. Watanabe"Optical Properties of Photonic
Crystal Slab Components: Role ofDisorder"Jun. 24,2005

Young Scientist Awardfor the Presentation of
Excellent Paper

K. Oguri"For Time-resolved EXAFS
Measurement of Ultrafast
Laser-melted Si Using a Sub-10-ps
Soft-x-ray Pulse"

Sep. 7,2005

Medal with purple
RibbonY. Yamamoto"Quantum Optioncs"

Nov. 3,2005

The Surface Science
Society of JapanThe Best Poster Prize
ISSS-4(International
Symposium on Surface
Science andNanotechnology)

K. Uchida"First-Principles Study ofField-Effect Doping in Nano-Scale
Systemsby the Enforced Fermi-Energy
Difference Method"

Nov. 15,2005

The Surface Science
Society of JapanSSSJ Review Paper
Award

T. Ogino
Y. Homma
K. Sumitomo
H. OmiD. Bottomley
Z. Zhang"Nanostructure Self-Organization
by Controlling Surface andInterface Strain"

Nov. 17,
2005

－54－

Research Activities in NTT Basic Research Laboratories Vol. 16 (September 2006)

In-house Award Winners’ List (Fiscal 2005)

NTT Technical
Review
Selected Papers

Y. Hirayama
H. Takayanagi
K. Inoue
K. Shimizu
H. KamadaT. Fujisawa
M. Notomi
E. Kuramochi
A. Shinya
T. Tanabe
K. Yamada"Toward Quantum Information
Technology"

Dec.14,
2005"Realization of Ultrasmall
Photonic-Crystal Optical Components"

Dec.14,2005

NTT R&D Award

K. Kumakura
M. Hiroki
T. Makimoto
H. Yokoyama
T. Kobayashi"Substrate for nitride semiconductor
growth"Dec.14,2005

NTT R&D Award

T. Honjo
H. Takesue
Y. Tokura
A. Sahara
H. Takahashi"Quantum cryptography"

Dec.14,
2005

Award forAchievements by
Director of Basic
Research
Laboratories

S. Suzuki
D. Takagi
K. Kanzaki
Y. Homma
Y. Kobayashi"Suspended architecture formation andfunctionalization by low-energy
electron irradiation of carbon
nanotubes"

Mar. 16,
2006

Award forAchievements by
Director of Basic
Research
Laboratories

W. Hu
H. Nakashima
Y. Kashimura
K. Furukawa"Fabrication and characterization of
conductive polymer based moleculardevice combined with nano-gap
electrodes"

Mar. 16,
2006

Award forAchievements by
Director of Basic
Research
Laboratories

K. Yamazaki
H. Namatsu"Three-dimensional electron beamlithography"

Mar. 16,
2006

Award forAchievements by
Director of Basic
Research
Laboratories

K. Oguri
Y. Okano
T. Nishikawa
H. Nakano"Development of ultrafast absorption
spectroscopy using femtosecondlaser-based ultrashot x-ray source"

Mar. 16,
2006

NTT R&D Award－55－

Research Activities in NTT Basic Research Laboratories Vol. 16 (September 2006)

Award for
Excellent Papers by
Director of Basic
Research
Laboratories
Special Award by
Director of Basic
Research
Laboratories

G. Yusa
K. Muraki"Controlled multiple quantum
coherences of nuclear spins in a
nanometre-scale device" Nature Vol.
434, 1001 (2005)

Mar. 16,
2006

T. Fujisawa
K. Suzuki
H. Tamura
M. Kumagai"Significant cost reduction andimproved management for the heliumliquefier and the recovery system"

Mar. 16,
2006

－56－

Research Activities in NTT Basic Research Laboratories Vol. 16 (September 2006)

List of Visitors’ Talks (Fiscal 2005)

l. Materials Science
Date

Speaker

Affiliation"Topic"May 25

Prof. Tom Lemberger

July 21

Dr. Krishna G. NathAug.

Prof. Shigeya Naritsuka

Ohio State University, USA"Pairing symmetry of electron- and hole-doped
cuprates from the magnetic penetration depth
measurements"
INRS-EMT, Univ. of Quebec, Canada"Supramolecule-Nanopattering for Future Medical
and Biological Application"
Meijo University"Beam Induced Lateral Epitaxy of GaAs on GaAs
substrates"
Northeastern University, USA"Tailoring Carbon Nanotube Structure andBuilding Nanotube based system"
Rigaku Corp.
"Small Angle X-ray Scattering for Nano-strucure
Analysis"
Universität Ulm, Germany"Liquid Junctions to Wide Bandgap
Semiconductors"

4

Sep. 29

Prof. Yung Joon Jung

Jan. 17

Dr. Kazuhiko Omote

Jan. 23

Prof. Erhard Kohn

lI. Physical Science
Date

Apr.

6

Speaker

Affiliation"Topic"Prof. David Haviland

Kungliga Tekniska Högskolan, Sweden"Spin Transport and Superconducting
Nano-Circuits"－57－

Research Activities in NTT Basic Research Laboratories Vol. 16 (September 2006)

Apr. 15

May 27June

2June 16

June 28

July

8

July 15

July 28

Aug.

1

Aug.

1

Aug.

3

Aug.

9

Dr. Stefan Fölsch

Paul-Drude-Institut, Germany"Assembly and spectroscopy of atomic-scalesurface structures by low-temperature STM: Frommonatomic chains to single-molecule/quantum
wire contacts"
Dr. Tetsuo Kishimoto
PRESTO, JST, The University of Tokyo"Electric trapping of Neutral atoms and its on-chip
application"
Dr. Yosuke Takasu
Kyoto University"Quantum Degenerate Gases of Ytterbium Atoms"
Ms. Irina Stefana Ionica
Institut de Microelectronique, France"Coulomb Blockade and Field Effect for Silicon
Nanostructures Fabricated by Atomic ForceMicroscope on Ultrathin SOI Substrates"
Prof. A. R. Hamilton
University of New South Wales, Australia"Quantum Interference and Interaction Effects in
2D Quantum Wells and 1D Quantum Wires"
Dr. Tom Stace
University of Cambridge, UK"Population inversion in driven quantum dots withan unstructured phonon bath"
Prof. Richard A. Kiehl
University of Minnesota, USA"Information Processing by Assemblies of
Molecules: Directed Self-Assembly, Nonlinear
Behavior, Array Architectures"
Ms. Claire Marrache-Kikuchi Centre de Spectrométrie Nucléaire et deSpectrométrie de Masse, France"Dimensionality effects in NbSi thin films"
Prof. Rui-Rui Du
Rice University, USA"New aspects of microwave-induced
zero-resistance states in high-mobility 2DEG"
Dr. K.-J. Friedland
Paul-Drude-Institut, Germany"Intrinsic planar Hall effect in Fe and Fe3Si films
on GaAs(001) and GaAs(113) substrates"
Prof. Daniel E. Prober
Yale University, USA"Quantum Shot Noise of a Tunnel Junction and a
Diffusive Wire: Third Moment and Driven
Response"
Dr. Lieven Vandersypen
Delft University of Technology, Netherlands"Single-shot read-out, relaxation and decoherenceof single spins in GaAs quantum dots"－58－

Research Activities in NTT Basic Research Laboratories Vol. 16 (September 2006)

Sep.

6

Prof. Andrew Briggs

Sep. 28

Dr. Guy Austing

Sep. 30

Dr. Adam Micolich

Oct.

7

Prof. Jonathan FinleyOct. 24

Mr. Daisuke Akamatsu

Oct. 26

Prof. Amnon Aharony

Oct. 26

Prof. Ora Entin-Wohlman

Nov.

Dr. Alexandre Blais

7

Nov. 22

Prof. Giuseppe Iannaccone

Dec. 19

Dr. Yasuhiro Utsumi

Jan. 12

Dr. Pawel Hawrylak

Jan. 16

Dr. Kazuhito Tsukagoshi

Jan. 23

Dr. Masaya Kataoka

Feb. 15

Prof. Mikio Nakahara

Feb. 16

Prof. Mats Jonson

University of Oxford, UK"Carbon nanomaterials for quantum information
processing"
National Research Council Canada, Canada"Recent research topics on vertical quantum dot
structures and carbon nanotubes"
University of New South Wales, Australia"Fractal Conductance Fluctuations in
Semiconductor Billiards" and "Superconductivity
in Metal-mixed Ion-implanted Polymer Films"
Walter Schottky Institut, Germany"Semiconductor quantum dots, molecules andtheir coupling to light"
Tokyo Institute of Technology"Preserving squeezed vacuum withelectromagnetically induced transparency (EIT)"
Tel Aviv University, Israel"Old and new results on phase measurements in
Aharonov-Bohm interferometers"
Tel Aviv University, Israel"Spin-Hall effect of localized electrons"
Yale University, USA"Quantum optics and quantum information
processing with superconducting circuits"
Universita' di Pisa, Italy"Modeling of Nanoelectronic Devices as aStrategic Tool in Semiconductor Technology"
RIKEN"Full Counting Statistics in Quantum Dots"National Research Council Canada, Canada"Electronic Correlations in Quantum Degenerate
Systems"
RIKEN"Nano-scale fabrication and materials transport"
University of Cambridge, UK"Charge Transport using Surface Acoustic Wave"
Kinki University"Artificial generation and suppression of
decoherence in NMR quantum computer"
Chalmers/Goteborg University"Mechanically assisted single electronics"－59－

Research Activities in NTT Basic Research Laboratories Vol. 16 (September 2006)

Feb. 17

Prof. Eleanor
E.B. Campbell

Feb. 20

Dr. Andrew Watt

Feb. 22

Prof. Christopher Bäuerle

Feb. 22

Mr. Yuji Kurotani

Mar. 20

Prof. Wilfred G.
van der Wiel

Gothenburg University, Sweden"Taming Carbon Nanotubes for Use as
Nanoelectronics and NEMS Devices"
Oxford University, UK"Spin Active Fullerene Superlattices"Centre de Recherches sur les Très BassesTempératures, France"Dimensional crossover in quantum networks:
from macroscopic to mesoscopic"
Tokyo Institute of Technology"Theoretical circuit analysis of quantum
measurement processes"
Universiteit Twente, Nederlands"NanoElectronics: More than Moore"lII. Optical Science
Date

Speaker

Affiliation"Topic"Apr. 21

Dr. Yuki Kawaguchi

Apr. 27

Dr. Shiro Kawabata

July 27

Mr. Wouter Wetzels

Aug. 10

Dr. Ulrich Zuelick

Sep.

Dr. David Poulin

Tokyo Institute of Technology"Splitting process of a quadruply charged vortex
in a Bose-Einstein condensate with alkali-metal
atoms"
Nanotechnology Research Institute AIST
"Macroscopic Quantum Tunneling in High-Tc
Superconductor Josephson Junctions: Theory andExperiment"
Delft University of Technology, Netherlands"Non-collinear single electron spin-valve
transistors"
Massey University, New Zealand"Spin interferometry and entanglement generation
with Rashba spin splitting"
The University of Queensland, Australia"Robust quantum key distribution: Putting
quantum error correction theory to work on small
systems"

1－60－

Research Activities in NTT Basic Research Laboratories Vol. 16 (September 2006)

Nov. 11

Mr. Brig Elliott

Dec.

Dr. Alessandro Pioda

8

Dec. 22

Dr. Parisa Fallahi

Jan.

6

Prof. Shun Lien ChuangJan. 19

Prof. Yong-Hang Zhang

Feb. 16

Dr. Koji Hatanaka

Mar.

3

Prof. Vlatko Vedral

Mar. 16

Dr. Wataru Izumida

BBN Technologies, USA"Introduction of BBN and BBN’s Quantum
Network test bed"
Eidgenössische Technische Hochschule Zürich,
Switzerland"Local spectroscopy on quantum dots"
Harvard University, USA"Coulomb Blockade Imaging of electrons in
Few-Electron Quantum Dots"
University of Illinois, USA"Slow Light Using Quantum Devices"
Arizona State University, USA"Electroluminescence refrigeration in
Semiconductors"
Tohoku Univ.
"Interaction between intense laser and solutions:
Pulsed x-ray emission from aq. solutions whenirradiated by femtosecond laser"
University of Leeds, UK"Entanglement in the Solid State"
Tohoku University"Phonon-assisted tunneling in interacting
suspended single wall carbon nanotubes"－61－

Research Activities in NTT Basic Research Laboratories Vol. 16 (September 2006)

Research Activities of Basic Research Laboratories in 2005
The numbers of research papers, presentations at the international conferences and applied
patents amounted to 165, 257, and 75 in Basic Research Laboratories as a whole. All numbers
according their research areas are as follows.

Research Papers Published in International Journals(2004.1 - 2004.12)
Materials Science

Physical Science

Optical Science

0

10

20

30

40

50

60

70

120

140

30

35

Number of Papers

Presentations at International Conferences(2004.1 - 2004.12)
Materials Science
Physical Science
Optical Science
0

20

40

60

80

100

Number of Presentations

Applied Patents (2004.1 - 2004.12)

Materials Science
Physical Science
Optical Science
0

5

10

15

20

25

Applied Patents
Domestic－62－

International

Research Activities in NTT Basic Research Laboratories Vol. 16 (September 2006)

The major journals and the number of published papers are shown below.
General Science Journals
nameNatureSpecialized Journals
nameJapanese Journal of Applied Physics
Applied Physics Letter
Physical Review B
Physical Review Letter
Physical Review A
Journal of Applied Physics
Physica E
Optics Letter
Surface Science
Physica C
Optics Express
Journal of the Physical Society of Japan
Molecular Cell
Journal of the American Chemical Society
The Journal of Biological Chemistry
Nano Letters*IF2003: Impact factor 2003 （Journal Citation Reports, 2003）(IF2003)*(30.979)

numbers
1(IF2003)*
1.171
4.049
2.962
7.035
2.589
2.171
0.93
3.395
2.063
1.192
3.219
1.903
16.835
6.516
6.482
6.144

numbers
34
18
14
11
9
6
5
4
4
4
3
3
1
2
1
1

The average impact factor for individual research papers from all NTT Basic ResearchLaboratories is 2.79.
The major international conferences and their number of presentation are shown below.
Conferences

numbers

International Conference on Nanoelectronics, Nanostructures and Carrier Interactions (NNCI2005)
IQEC and CLEO-PR
International Conference on Solic State Devices and Materials (SSDM)
Electronic Properties of Two-Dimensional Systems and Modulated Semiconductor Structures (EP2DS)
CLEO/QELSAnnual APS Meetiong
International Symposium on Surface Science and Nanotechnology
International Conference on Low Temperature Physics
International Conference on Nitride Semiconductors (ICNS)International Symposium on Superconductivity
LEOS
Seventh International Conference on New Phenomena in Mesoscopic Structures / Fifth International
Conference on Surfaces and Interfaces of Mesoscopic Devices (NPMS-7 / SIMD-5)
International Conference on Defects in Semiconductors
International Conference on Si Epitaxy and Heterostructures
Silicon nanoelectronics workshop
International School and Conference on Semiconductor Spintronics and Quantum Information Technology
Materials Research Society meetings (MRS)International Symposium on Compound Semiconductors (ISCS)ACS National Meeting
International Conference on Electron, Ion, Photon Beam Technology and Nanofabrication (EIPBN)
Gordon Research Conference
International Workshop of Photonic and Electromagnetic Crystal Structures (PECS)

－63－

32
21
16
12
9
9
8
7
5
5
5
5
4
4
4
4
3
2
1
1
2
1

Research Activities in NTT Basic Research Laboratories Vol. 16 (September 2006)

List of Invited Talks at International Conferences (2005)
I. Materials Science Laboratory(1)

T. Matsuoka, H. Okamoto, M. Nakao, and, T. Makimoto, "Temperature Dependence of
Optical Bandgap of Wurtzite InN", Air Force Office of Scientific Research (AFOSR)
Indiumu Nitride Workshop, Hawaii, USA (Jan. 2005).

(2)

K. Torimitsu, "Effect of magnesium on neural activities and its analysis using
micro-electrode array-based measurement", 9th Gordon Research Conference on
Magnesium in Biochemical Processes and Medicine, Gordon Research Conference,
Ventura, USA (Feb. 2005).

(3)

H. Omi and Y. Homma, "Stiffness of step bunches on Si(111)", Crystalization andelectrocrystalization: Fundamentals and applications (CEFA), Varna, Bulugaria (Mar.
2005).

(4)

K. Torimitsu, "Information processing in neuron and molecular function", 3rd
Sweden/Japan Workshop on Nanobiotechnology, Lund, Sweden (Mar. 2005).

(5)

A. Shimada and K. Torimitsu, "Nano-Bio Science: Neuronal Functions and Nano-Bio
Devices", The 20th UK-Japan High Technology Industry Forum, LIFE SCIENCES, Kyoto,
Japan (May 2005).

(6)

K. Torimitsu, N. Kasai, A. Shimada, Y. Furukawa, C. Han, T. Nyberg, "Functional
analysis of neuron and its application to nanobio device", Workshop on Neural Networks:
Measurement and Adaptive Properties, Newcastle, UK (May 2005).

(7)

N. Kasai, C. Han, A. Shimada, T. Nyberg, K. Torimitsu, "Multichannel electrochemicalmeasurement for neurotransmitter distribution in a rat hippocampal slice", Workshop on
Neural Networks: Measurement and Adaptive Properties, Newcastle, UK (May 2005).

(8)

T. Nyberg, N. Kasai, A. Shimada, Y. Furukawa,K. Torimitsu, "Conducting polymer
electrodes for interfacing to neural networks", Workshop on Neural Networks:
Measurement and Adaptive Properties, Newcastle, UK (May 2005).

(9)T. Makimoto and K. Kumakura, "Npn-type Nitirde Heterojunction Bipolar Transistor",
3rd International Conference on Materials for Advanced Technologies (ICMAT-2005),
J-6-IN13, Singapore (Jul. 2005).

(10) K. Torimitsu, Y. Furukawa, N. Kasai, A. Shimada, Distinguished Lecturer, International－64－

Research Activities in NTT Basic Research Laboratories Vol. 16 (September 2006)

Conference on Composites/Nano Engineering, ICCE/12, Tenerife, Spain (Aug. 2005).
(11) H. Sato, M. Naito, and A. Tsukada, "Difference in Tc for La-214 strained thin films
grown by molecular beam epitaxy: assessment on the factors determining Tc", 18th
International Symposium on Superconductivity (ISS2005), PC-12-INV, Tsukuba, Japan(Oct. 2005).
(12) M. Kasu, K. Ueda, H. Ye, Y. Yamauchi, S. Sasaki, and T. Makimoto, "Diamondfield-effect transistors for RF power application", 1st International Diamond Conference,
D-1, Barcelona, Spain (Oct. 2005).
(13) K. Torimitsu, K. Furukawa, H. Nakashima, Y. Kashimura, N. Kasai, A. Shimada and Y.
Furukawa, "Neural Functions and Nanobio-interface", Japan-UK Symposium on
Promotion of Regional Partnerships on Nanotechnology Development, Sapporo , Japan(Oct. 2005).

II. Physical Science Laboratory(1)

N. M. Zimmerman, A. Fujiwara, Y. Ono, H. Inokawa, Y. Takahashi, and E. Hourdakis,"The physics of Coulomb blockade in tunable barrier Si wires", International Conference
on Nanoelectronics, Nanostructures, and Carrier Interaction (NNCI2005), Atsugi, Japan(Jan. 2005).

(2)

T. Fujisawa, "Dynamics of single-electron charge and spin in semiconductor quantum
dots", Nanometer-Scale Quantum Physics(nanoPhys'05), Tokyo, Japan (Jan. 2005).

(3)

K. Semba, "Coherent control of superconducting flux qubits", 10th International Vortex
Workshop, TIFR-Mumbai, India (Jan. 2005).

(4)

H. Takayanagi, "Control and detection of electron and hole states in double-gatedquantum wells", 2005 RCIQE International Seminar for 21C COE Program, Hokkaido,
Japan (Feb. 2005).

(5)

H. Takayanagi, "Advances in Science and Technology for Quantum Computing", 3rdInternational Symposium on Nanotechnology (JAPAN NANO 2005), Tokyo, Japan (Feb.
2005).

(6)

H.
Yamaguchi,S.
Miyashita,
andY.
Hirayama,"Low-dimensional
Micro/Nanomechanical Systems", The International Conference on Nanotechnology:
Science and Application (Nano Tech Insight 2005), Luxor, Egypt (Feb. 2005).

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Research Activities in NTT Basic Research Laboratories Vol. 16 (September 2006)(7)

Y. Hirayama, "Coherent control in semiconductor
Japan-Germany Colloquium, Dresden, Germany (Feb. 2005).

nanostructures",

JSPS

(8)

Y. Ono, A. Fujiwara, Y. Takahashi, and H. Inokawa (invited), "Silicon single-electron
pump and turnstile; Interplay with crystalline imperfection", Material Research Society
Spring Meeting (2005 MRS Spring meeting), San Francisco, USA (Mar. 2005).

(9)

G. Yusa, K. Muraki, K. Takashina, T. Saku, K. Hashimoto, and Y. Hirayama"Self-sustaining resistance oscillations: Electron-nuclear spin coupling in mesoscopic
quantum Hall devices", The American Physical Society Meeting, Los Angels, USA (Mar.
2005).

(10) T. Fujisawa, "Dynamics of single-electron charge and spin in semiconductor quantum
dots", ESF-JSPS Frontier Science Conference Series (Quantum Information and Quantum
Physics), Shonan, Japan. (Mar. 2005).
(11) G. Yusa, K. Muraki, K. Takashina, T. Saku, K. Hashimoto, and Y. Hirayama"Self-sustaining resistance oscillations: Electron-nuclear spin coupling in mesoscopic
quantum Hall devices", The American Physical Society, Los Angels, USA (Mar. 2005).
(12) H. Takayanagi, "Readout of flux qubits", Workshop "Physics of Superconducting Phase
shift Devices", Ischia, Italy (Apr. 2005).
(13) H. Takayanagi, "Japanese Policy", NSIT(Forward look in nanosciences and thelong-term evolution of information technology), Paris, France (Apr. 2005).
(14) M. Uematsu, H. Kageshima, S. Fukatsu, K. M. Itoh, and K. Shiraishi, "Enhanced Si and
B Diffusion in Semiconductor-Grade SiO2 and the Effect of Strain on Diffusion", The
Fourth International Conference on Silicon Epitaxy and Heterostructures (ICSI-4), Awaji,
Japan (May 2005).
(15) Y. Takahashi, Y. Ono, A. Fujiwara, K. Nishiguchi, and H. Inokawa, "Silicon-based
single-electron devices", Fourth International Conference on Silicon Epitaxy andHeterostructures (ICSI-4), Awaji Island, Japan (May 2005).
(16) S. Nomura, M. Yamaguchi, T. Akazaki, H. Tamura, H. Takayanagi and Y. Hirayama,"Eectron-Hole complexes in a back-gated quantum well in the fractional quantum Hall
regime", 351-WE-Heraeus-Seaminar, Electron-Exciton Interaction in Semiconductor
Nanostructure, Bad Honnef, Germany (May 2005).
(17) H. Takayanagi, "Nanotechnology Research Activities at NTT BRL", Conference on
nanotechnology and new materials (NANOMAT), Trondheim, Norway (June 2005)－66－

Research Activities in NTT Basic Research Laboratories Vol. 16 (September 2006)(18) H. Takayanagi, "Readout of flux qubits (Beijing)", "Recent progress in mesoscopic
superconductivity"(Nanjing), 5th ICQS(International Center for Quantum Structures)
Annual Workshop, Beijing & Nanjing, China (June 2005).
(19) Y. Hirayama, "Quantum information technology", Spin and Qubits 2005, Copenhagen,Denmark (June, 2005).
(20) T. Fujisawa, "Counting statistics of single-electron transport" Spin&Qubit-2005,
Copenhagen, Denmark (June 2005)(21) T. Hayashi, "Decoherence and energy relaxation in a double quantum dot", RIKENInternational Nanoscience and Technology Conference, Nagano, Japan (June 2005).
(22) K. Takashina, Y. Ono, A. Fujiwara, Y. Takahashi and Y. Hirayama, "Control of valley
and spatial subbands in double-gate SOI MOSFETs", Asia-Pacific Workshop on
Fundamental and Application of Advanced Semiconductor Devices (AWAD 2005), Seoul,
Korea (June 2005).
(23) H. Tanaka, "Superconducting flux qubits", Spin and Qubit 2005, Symposium at theNiels Bohr Institute, Copenhagen, Denmark (June 2005).
(24) M. Uematsu, "Self-diffusion and impurity diffusion in silicon dioxide", 1st International
Conference on Diffusion in Solids and Liquids (DSL-2005), Aveiro, Portugal (July 2005).
(25) H. Yamaguchi, "InAs/GaAs (111)A Heterostructures", 3rd Vacuum and Surface
Sciences Conference of Asia and Australia (VASSCAA-3), Singapore (July 2005).
(26) S. Hosoi, K. Nakajima, M. Suzuki, K. Kimura, Y. Shimizu1, S. Fukatsu, K. M. Itoh, M.
Uematsu, H. Kageshima, and K. Shiraishi, "Oxidation of Si(001) studied byhigh-resolution RBS in combination with stable isotope tracing", The 17th International
Conference on Ion-Surface Interactions (ISI-2005), Zvenigorod, Russia (Aug. 2005).
(27) Y. Hirayama, G. Yusa and K. Muraki, "Coherent control of nuclear spins in amesoscopic fractional-quantum-Hall device", Awaji-island, Japan (Aug. 2005).
(28) H. Takayanagi, "Readout of flux qubits", ESF Research Conferences - Fundamental
Problems of Mesoscopic Physics, Entanglement and Coherence in Nanoelectronics-,
Maratea, Italy (Sep. 2005).
(29) H. Takayanagi, "Readout of supercondcuting flux qubits", VORTEX IV (VORTEX
MATTER IN NANOSTRUCTURED SUPERCONDUCTORS), Crete, Greece (Sep.
2005).

－67－

Research Activities in NTT Basic Research Laboratories Vol. 16 (September 2006)(30) Y. Hirayama, "Qubits and nuclear spin polarization", 32nd Int. Symp. on Compound
Semiconductors (ISCS2005), Rust, Germany (Sep. 2005).
(31) H. Nakano, "Superconducting qubits and their interaction", in International Symposium"Quantum computing 2005 Algorithms, Physical Realizations and Beyond",
Higashi-Osaka, Japan (Sep. 2005).
(32) H. Takayanagi, "A Flux Qubit coupled with an external LC-Cavity", 2005 Deutschland
in Japan -Tokyo Workshop Frontier Sciences-, Tokyo, Japan (Oct. 2005).
(33) H. Inokawa, Y. Ono, A. Fujiwara, K. Nishiguchi, and Y. Takahashi, " Single-Electron
Devices and Circuits Based on MOS Processes," 2005 Tera-level NanoDevices (TND)
Technical Forum, Seoul, Korea (Oct. 2005).
(34) Y. Ono, A. Fujiwara, Y. Takahashi, and H. Inokawa, "Single-electron manipulation
Interplay with crystalline imperfection", 2nd International Symposium on Point Defectand Nonstoichiometry (ISPN-2), Kaoshiung, TaiwanSession (Oct. 2005).
(35) G. Yusa, K. Muraki, K. Takashina, K. Hashimoto, and Y. Hirayama, "Controlled
multiple quantum coherences of nuclear spins in a nanometer-scale Device", 50th
Magnetism and Magnetic Materials Conference (MMM2005), San Jose, USA (Oct. 2005).
(36) G. Yusa, K. Muraki, K. Takashina, K. Hashimoto, and Y. Hirayama, "Controlled
multiple quantum coherences of nuclear spins in a nanometer-scale Device", 50th
Magnetism and Magnetic Materials Conference, San Jose, USA (Oct. 2005).
(37) H. Tamura, "RKKY interaction and Kondo effect in double quantum-dot devices",
International Workshop on Spins and Quantum Transport, Sendai, Japan (Oct. 2005).
(38) Y. Ono, "Single-electron manipulation in silicon; Towards single-dopant electronics",
7th International Conference on New Phenomena in Mesoscopic Structures and 5thInternational Conference on Surfaces and Interfaces of Mesoscopic Devices(NPMS-7/SIMD-5), Maui, USA (Nov. 2005).
(39) H. Yamaguchi, "Micro/Nanomechanical Quantum Electron Transport", Second Joint
International Conference on New Phenomena in Mesoscopic Systemsand Surfaces andInterfaces of Mesoscopic Devices (NPMS7/SIMD5), Maui, USA (Nov. 2005).
(40) Y. Ono, A. Fujiwara, Y. Takahashi, and H. Inokawa, "Single-electron transfer in silicon",International Workshop on the Physics semiconductor devices (IWPSD 2005), Delhi,
India (Dec. 2005).
(41) T. Fujisawa, "Counting statistics of single-electron transport through quantum dots",－68－Research Activities in NTT Basic Research Laboratories Vol. 16 (September 2006)

International Semiconductor Device Research Symposium (ISDRS2005), Washinton DC,
USA (Dec. 2005).

III. Optical Science Laboratory(1)

H. Nakano, K. Oguri, and T. Nishikawa, "Time-resolved measurements using ultrafast
soft x-ray sources based on femtosecond laser", International Symposium on Atoms,
Molecules, and Clusters in Intense Laser Fields 2 (ISAMCILS2), Tokyo, Japan (Jan.
2005).

(2)

M. Notomi, A. Shinya, E. Kuramochi, S. Mitsugi, T. Tanabe, "PBG
Resonator-Waveguide Coupled Systems for Optical Integration", SPIE Photonics West2005, San Jose, USA (Jan. 2005).

(3)

A. Shinya, S. Mitsugi, E. Kuramochi, T. Tanabe, G. Kim, G. Kira, S. Kondo, K. Yamada,T. Watanabe, T. Tsuchizawa, and M. Notomi, "Ultrasmall resonant tunneling/dropping
devices in 2D photonic crystal slabs", SPIE Photonics West 2005, San Jose, USA (Jan.
2005).

(4)

H. Nakano, K. Oguri, and T. Nishikawa, "High-order harmonic pulse characterization
by femtosecond ionization dynamics of singly charged ions from rare gas", The First
Asian Workshop on Generation and Applications of High-Order Harmonics, Daejeon,
Korea (Feb. 2005).

(5)

H. Gotoh and H. Kamada, "Exciton and Biexciton Coherent Optical Properties in
Semiconductor Nanostructures", The 1st International Symposium on Nanovision Science,
Hamamatsu, Japan (Feb. 2005).

(6)

H. Nakano, K. Oguri, and T. Nishikawa, "Picosecond time-resolved XAFS
measurements using femtosecond laser-produced plasma soft x-rays", COAST
Symposium on Laser Based Ultrashort VUV and X-ray Sources and Their Applications,Tokyo, Japan (Mar. 2005).

(7)

Y. Tokura, "Scattering and manipulation of electron spins in one dimensional structures",2nd International Workshop on Spin-FET Based Quantum Information Processing(Spin_FET-QIP), Julich, Germany (Mar. 2005).

(8)

A. Yokoo, "Nanoimprint technology and organic material", Third International
Conference on Molecular Electronics and Bioelectronics (M&BE3), Tokyo, Japan (Mar.
2005).

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Research Activities in NTT Basic Research Laboratories Vol. 16 (September 2006)(9)

M. Notomi, "Dynamic Nonlinear Control of Resonator-Waveguide Coupled System in
Photonic Crystal Slabs", CIPS Annual Meeting 2005, Cambridge, USA (May 2005).

(10) T. Tawara, "InGaN Cavity Polaritons", The Fifth International Conference on the
Physics of Light Matter Coupling in Nanostructures," (PLMCN5), Glasgow, Scotland(June 2005).
(11) M. Notomi, T. Tanabe, A. Shinya, E. Kuramochi, S. Mitsugi, "Dynamic Nonlinear
Control of Photonic Crystal Resonator-Waveguide Coupled System", International
Symposium on Photonic Electromagnetic Structures (PECS-VI), Crete, Greece (June2005).
(12) M. Notomi, T. Tanabe, A. Shinya, E. Kuramochi, S. Mitsugi, "Dynamic Nonlinear
Control of Resonator-Waveguide Coupled System in Photonic Crystal Slabs", CLEO
Pacific Rim 2005, Tokyo, Japan (July 2005).
(13) M. Notomi, H. Suzuki, T. Tamamura, K. Edagawa, "Organic Photonic Quasicrystal
lasers: lasing action due to quasiperiodicity", SPIE Optics & Photonics 2005, San Diego,
USA (July 2005).
(14) M. Yamashita and M. W. Jack, "Decoherence of spin-one bosonic atoms via linear loss",
International Laser Physics Workshop (LPHYS'05), Kyoto, Japan (July 2005).
(15) H. Nakano, K. Oguri, and T. Nishikawa, "Picosecond time-resolved XAFS
measurements of optically excited silicon by using femtosecond-laser-plasma soft x-rays",
14th International Laser Physics Workshop (LPHYS'05), Kyoto, Japan (July 2005).
(16) A. Yokoo, "Photonic crystal with organic functional material", The 5th International
Symposium on Advanced Organic Photonics (ISAOP-5), Jena, Germany (Oct. 2005).
(17) M. Notomi, A. Shinya, E. Kuramochi, S. Mitsugi, T. Tanabe, M. Morita, "Dynamic
Nonlinear Control of Resonator-Waveguide Coupled Systems in Photonic Crystals", The
18th annual meeting of the IEEE Lasers and Electro-Optics Society (LEOS 2005), Sydney,
Australia (Oct. 2005).
(18) A. Shinya, S. Mitsugi, T. Tanabe, K. Kuramochi, S. Kondo, M. Notomi, I. Yokohama, H.
Takara, S. Kawanishi, "All-Optical Digital Circuits using Coupled Resonator-Waveguide
System in 2D Photonic Crystal Slab", The 18th annual meeting of the IEEE Lasers andElectro-Optics Society (LEOS2005), Sydney, Australia (Oct. 2005).
(19) Y. Tokura, "Electron spin resonance and two qubit operation in a slanting Zeeman field",International Argonne Fall Workshop on Nanophysics V: Nanoscale Superconductivity
and Magnetism, Argonne, USA (Nov. 2005).
－70－

Research Activities in NTT Basic Research Laboratories Vol. 16 (September 2006)(20) M. Notomi, A. Shinya, E. Kuramochi, S. Mitsugi, T. Tanabe, M. Morita, "Dynamic
Nonlinear Control of Resonator-Waveguide Coupled Systems in Photonic Crystals",
Workshop on Photonic Crystals and Nano-Photonics, Taipei, Taiwan (Nov. 2005).
(21) H. Nakano, K. Oguri, and T. Nishikawa, "Picosecond time-resolved XAFS
measurements using femtosecond laser-produced plasma soft x-rays", 2005 International
Chemical Congress of Pacific Basin Society (PACIFICHEM 2005), Honolulu, USA (Dec.
2005).

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Research Activities in NTT Basic Research Laboratories Vol. 16 (September 2006)

List of Research Papers Published in International Journals

Materials Science LaboratoryThin-Film Materials Research Group1.

T. Akasaka and T. Makimoto, "BGaN micro-islands as novel buffers for GaN
hetero-epitaxy",
Jpn. J. Appl. Phys. Part 2 - Lett. Express Lett. 44 (50-52), L1506-L1508 (2005).

2.

T. Akasaka, H. Gotoh, H. Nakano, and T. Makimoto, "Blue-purplish InGaN quantum
wells with shallow depth of exciton localization",
Appl. Phys. Lett. 86 (19), 191902 (2005).

3.

M. Kasu, K. Ueda, H. Ye, Y. Yamauchi, S. Sasaki, and T. Makimoto, "2W/mm output
power density at 1 GHz for diamond FETs",
Electron. Lett. 41 (22), 1249-1250 (2005).

4.

K. Kumakura and T. Makimoto, "High-voltage operation with high current gain of pnp
AlGaN/GaN heterojunction bipolar transistors with thin n-type GaN base",Appl. Phys. Lett. 86 (2), 023506 (2005).

5.

K. Kumakura, T. Makimoto, N. Kobayashi, T. Hashizume, T. Fukui, and H. Hasegawa,"Minority carrier diffusion length in GaN- Dislocation density and dopoing
concentration dependence",
Appl. Phys. Lett. 86 (5), 052105 (2005).

6.

K. Kumakura, Y. Yamauchi, and T. Makimoto, "High power operation of Pnp
AlGaN/GaN heterojunction bipolar transistors",
Phys. Stat. Sol. (c), 2 (7), 2589-2592 (2005).

7.

J. Kurian, H. Sato, T. Makimoto, and M. Naito, "Silver-assisted growth of
NdBa2Cu3O7-delta thin films: An approach for the growth of superior quality ceramicoxide films",
Appl. Phys. Lett. 87 (2), 022501 (2005).

8.

J. Kurian and M. Naito, "MBE growth of large area RE-123 superconductor thin films
for microwave applications",
IEEE Trans. Appl. Supercond. 15 (2), 2966-2969 (2005).

9.

H. S. Lee, H. J. Kim, H. J. Kim, M. H. Jung, Y. Jo, S. I. Lee, A. Tsukada, and M. Naito,"Three-dimensional superconductivity of the structurally two-dimensional
superconductor La1.87Y0.13CuO4: study of an angle-dependent critical current density",
Supercond. Sci. Technol. 18 (7), 944-947 (2005).
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Research Activities in NTT Basic Research Laboratories Vol. 16 (September 2006)

10.

N. Maeda, T. Makimura, T. Maruyama, C. X. Wang, M. Hiroki, H. Yokoyama, T.
Makimoto, T. Kobayashi, and T. Enoki, "DC and RF characteristics in Al2O3/Si3N4
insulated-gate AlGaN/GaN heterostructure field-effect transistors",
Jpn. J. Appl. Phys. Part 2 - Lett. Express Lett. 44 (20-23), L646-L648 (2005).

11.

N. Maeda, T. Makimura, C. X. Wang, M. Hiroki, T. Makimoto, T. Kobayashi, and T.
Enoki, "Al2O3/Si3N4 Insulated Gate Channel-doped AlGaN/GaN Heterostructure
Field-Effect Transistors with Regrown Ohmic Structure: Low Gate Leakage Current
with High Transconductance",
Jpn. J. Appl. Phys. Part 1 – Regul. Pap. Short Notes Rev. Pap. 44 (4B), 2747-2750,(2005).

12.

N. Maeda, C. X. Wang, T. Enoki, T. Makimoto, and T. Tawara, "High drain current
density and reduced gate leakage current in channel-doped AlGaN/GaN
heterostructure field-effect transistors with Al2O3/Si3N4 gate insulator",Appl. Phys. Lett., 87 (7), 073504 (2005).

13.

T. Makimoto, Y. Yamauchi, T. Kido, K. Kumakura, Y. Taniyasu, M. Kasu, and N.
Matsumoto, "Strained Thick p-InGaN Layers for GaN/InGaN Heterojunction Bipolar
Transistors on Sapphire Substrates",
Jpn. J. Appl. Phys. Part 1 – Regul. Pap. Short Notes Rev. Pap. 44 (4B), 2722-2725(2005).

14.

T. Matsuoka, "Progress in nitride semiconductors from GaN to InN - MOVPE growthand characteristics",
Superlattices Microstruct. 37 (1), 19-32 (2005).

15.

T. Mitate, S. Mizuno, H. Takahata, R. Kakegawa, T. Matsuoka, and N. Kuwano, "InN
polarity determination by convergent-beam electron diffraction",
Appl. Phys. Lett. 86 (13), 134103 (2005).

16.

A. Nishikawa, K. Kumakura, T. Akasaka, and T. Makimoto, "Current-voltage
characteristics of p-InGaN/n-GaN vertical conducting diodes on n+-SiC substrates",Appl. Phys. Lett. 87 (23), 233505 (2005).

17.

M. Noda, A. Tsukada, H. Yamamoto, and M. Naito, "Origin of superconducting
carriers in "non-doped" T'-(La,RE)(2)CuO4 (RE = Sm, Eu, Gd, Tb, Lu, and Y)
prepared by molecular beam epitaxy",Physica C 426, 220-224 (2005).

18.

H. Oyanagi, N. L. Saini, A. Tsukada, and M. Naito, "Lattice anomalies in(La,Sr)(2)CuO4 under epitaxial strain probed by polarized X-ray absorption
spectroscopy",
J. Supercond. 18 (5-6), 731-735 (2005).

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Research Activities in NTT Basic Research Laboratories Vol. 16 (September 2006)

19.

H. Sato and J. Kurian, "Superconducting bandpass filters on thin films of
NdBa2Cu3O7",
Physica C 426, 1616-1621 (2005).

20.

A. Tsukada, H. Yamamoto, and M. Naito, "Ce doping in T-La2CuO4 films: Broken
electron-hole symmetry for high-T-c superconductivity",
Physica C 426, 454-458 (2005).

21.

A. Tsukada, M. Noda, H. Yamamoto, and M. Naito, "Role of impurity oxygen insuperconductivity of "non-doped" T '-(La, RE)(2)CuO4",
Physica C 426, 459-463 (2005).

22.

A. Tsukada, Y. Krockenberger, M. Noda, H. Yamarnoto, D. Manske, L. Alff, and M.
Naito, "New class of T '-structure cuprate superconductors",
Solid State Commun. 133 (7), 427-431 (2005).

23.

K. Ueda, S. Saito, K. Semba, T. Makimoto, and M. Naito, "All-MgB2 Josephson
tunnel junctions", Appl. Phys. Lett. 86 (17), 172502 (2005).

24.

C. X. Wang, N. Maeda, M. Hiroki, T. Tawara, T. Makimoto, T. Kobayashi, and T.
Enoki, "Comparison of AlGaN/GaN insulated gate heterostructure field-effecttransistors with ultrathin Al2O3/Si3N4 bilayer and Si3N4 single layer",
Jpn. J. Appl. Phys. Part 1 - Regul. Pap. Short Notes Rev. Pap. 44 (4B), 2735-2738(2005).

25.

H. T. Ye, H. X. Yan, and R. B. Jackman, "Dielectric properties of single crystal
diamond",
Semicond. Sci. Technol. 20 (3), 296-298 (2005).

Low-Dimensional Nanomaterials Research Group1.

P. Finnie, Y. Homma, and J. Lefebvre, "Band-gap shift transition in thephotoluminescence of single-walled carbon nanotubes",
Phys. Rev. Lett. 94 (24), 247401 (2005).

2.

S. Fujikawa, T. Kawamura, S. Bhunia, Y. Watanabe, K. Tokushima, Y. Tsusaka, Y.
Kagoshima, and J. I. Matsui, "Real-time observation of fractional-order x-rayreflection profiles of InP(001) during step-flow growth",
Jpn. J. Appl. Phys. Part 2 - Lett. Express Lett. 44 (1-7), L144-L146 (2005).

3.

H. Hibino, Y. Watanabe, C. W. Hu, and I. S. T. Tsong, "Thermal decay of superheated
7 x 7 islands and supercooled "1 x 1" vacancy islands on Si(111) ",Phys. Rev. B 72 (24), 245424 (2005).

4.

H. Hibino and Y. Watanabe, "Arrangement of Au-Si alloy islands at atomic steps",－74－Research Activities in NTT Basic Research Laboratories Vol. 16 (September 2006)

Surf. Sci. 588 (1-3), L233-L238 (2005).
5.

H. Hibino and Y. Watanabe, "Growth of twinned epitaxial layers on Si(111)root 3xroot 3-B studied by low-energy electron microscopy",
Jpn. J. Appl. Phys. Part 1 - Regul. Pap. Short Notes Rev. Pap. 44 (1A), 358-364(2005).

6.

Y. Homma, D. Takagi, S. Suzuki, K. Kanzaki, and Y. Kobayashi,"Electron-microscopic imaging of single-walled carbon nanotubes grown on siliconand silicon oxide substrates",J. Electron Microsc. 54, I3-I7 (2005).

7.

Y. Homma, "Summary of ISO/TC 201 standard: X ISO 17560: 2002 - Surface
chemical analysis - Secondary ion mass spectrometry - Method for depth profiling ofboron in silicon",
Surf. Interface Anal. 37 (1), 90-91 (2005).

8.

G. H. Jeong, S. Suzuki, Y. Kobayashi, A. Yamazaki, H. Yoshimura, and Y. Homma,"Effect of nanoparticle density on narrow diameter distribution of carbon nanotubes
and particle evolution during chemical vapor deposition growth",
J. Appl. Phys. 98 (12), 124311 (2005).

9.

G. H. Jeong, A. Yamazaki, S. Suzuki, H. Yoshimura, Y. Kobayashi, and Y. Homma,"Cobalt-filled apoferritin for suspended single-walled carbon nanotube growth withnarrow diameter distribution",
J. Am. Chem. Soc. 127 (23), 8238-8239 (2005).

10.

A. Kaneko, Y. Homma, H. Hibino, and T. Ogino, "Ultrahigh vacuum scanning electron
microscope system combined with wide-movable scanning tunneling microscope",
Rev. Sci. Instrum. 76 (8), 083709 (2005).

11.

T. Kawamura, S. Bhunia, Y. Watanabe, S. Fujikawa, J. Matsui, Y. Kagoshima, and Y.
Tsusaka, "High-resolution x-ray diffraction analysis of epitaxially grown indium
phosphide nanowires",
J. Appl. Phys. 97 (8), 084318 (2005).

12.

T. Matsumoto, Y. Homma, and Y. Kobayashi, "Bridging growth of single-walledcarbon nanotubes on nanostructures by low-pressure hot-filament chemical vapor
deposition",
Jpn. J. Appl. Phys. Part 1 - Regul. Pap. Brief Commun. Rev. Pap. 44 (10), 7709-7712(2005).

13.

H. Omi and Y. Homma, "Self-ordering on vicinal Si(111) during molecular beam
epitaxy",
Phys. Rev. B 72 (19), 195322 (2005).

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Research Activities in NTT Basic Research Laboratories Vol. 16 (September 2006)

14.

H. Omi, Y. Homma, V. Tonchev, and A. Pimpinelli, "New types of unstable step-flow
growth on Si(111)-(7 x 7) during molecular beam epitaxy: Scaling and universality",
Phys. Rev. Lett. 95 (21), 216101 (2005).

15.

H. Omi, T. Kawamura, S. Fujikawa, Y. Tsusaka, Y. Kagoshima, and J. Matsui,"In-plane strain distribution in the surface region of thin silicon overlayers on
insulator",Appl. Phys. Lett. 86 (26), 263112 (2005).

16.

V. Peano, M. Thorwart, A. Kasper, and R. Egger, "Nanoscale atomic waveguides withsuspended carbon nanotubes",
Appl. Phys. B-Lasers Opt. 81 (8), 1075-1080 (2005).

17.

S. Suzuki and Y. Kobayashi, "Conductivity decrease in carbon nanotubes caused by
low-acceleration-voltage electron irradiation",
Jpn. J. Appl. Phys. Part 2 - Lett. Express Lett. 44 (46-49), L1498-L1501 (2005).

18.

S. Suzuki, Y. Watanabe, Y. Homma, S. Y. Fukuba, A. Locatelli, and S. Heun,"Photoemission electron microscopy of individual single-walled carbon nanotubes",
J. Electron Spectrosc. Relat. Phenom. 144, 357-360 (2005).

19.

S. Suzuki, H. Yamamoto, F. Maeda, Y. Watanabe, K. Yamada, and T. Kiyokura,"Beamline for angle-resolved photoemission spectroscopy at low-temperature
constructed at NTT Atsugi R&D Center",J. Electron Spectrosc. Relat. Phenom. 144, 1109-1112 (2005).

20.

S. Suzuki, D. Takagi, Y. Homma, and Y. Kobayashi, "Selective removal of carbon
nanotubes utilizing low-acceleration-voltage electron irradiation damage",
Jpn. J. Appl. Phys. Part 2 - Lett. Express Lett. 44 (1-7), L133-L135 (2005).

21.

D. Takagi, Y. Homma, S. Suzuki, and Y. Kobayashi, "Vertical growth of individual
single-walled carbon nanotubes on silicon and SiO2 substrates",
Jpn. J. Appl. Phys. Part 1 - Regul. Pap. Short Notes Rev. Pap. 44 (4A), 1564-1568(2005).

22.

A. Vijayaraghavan, K. Kanzaki, S. Suzuki, Y. Kobayashi, H. Inokawa, Y. Ono, S. Kar,and P. M. Ajayan, "Metal-semiconductor transition in single-walled carbon nanotubes
induced by low-energy electron irradiation",
Nano Lett. 5 (8), 1575-1579 (2005).

23.

T. Yamazaki, S. Ohmi, S. Morita, H. Ohri, J. Murota, M. Sakuraba, H. Omi, and T.
Sakai, "Separation by bonding Si islands (SBSI) for advanced CMOS LSI
applications",
IEICE Trans. Electron. E88C (4), 656-661 (2005).

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Research Activities in NTT Basic Research Laboratories Vol. 16 (September 2006)

24.

T. Yamazaki, S. Ohmi, S. Morita, H. Ohri, J. Murota, M. Sakuraba, H. Omi, Y.
Takahashi, and T. Sakai, "Separation by bonding Si islands (SBST) for LSI
applications",
Mater. Sci. Semicond. Process 8 (1-3), 59-63 (2005).

Molecular and Bio Science Research Group1.

I. Bosanac, H. Yamazaki, T. Matsu-ura, T. Michikawa, K. Mikoshiba, and M. Ikura,"Crystal structure of the ligand binding suppressor domain of type 1 inositol
1,4,5-trisphosphate receptor",
Mol. Cell 17 (2), 193-203 (2005).

2.

A. Fontes, K. Ajito, A. A. R. Neves, W. L. Moreira, A. A. de Thomaz, L. C. Barbosa, A.
M. de Paula, and C. L. Cesar, "Raman, hyper-Raman, hyper-Rayleigh, two-photon
luminescence and morphology-dependent resonance modes in a single opticaltweezers system",Phys. Rev. E 72 (1), 012903 (2005).

3.

C. X. Han, N. Kasai, and K. Torimitsu, "Apoptosis induced by bicuculline involves the
P/Q-type voltage-dependent calcium channel in rat hippocampal slice cultures",
Epilepsia 46, 11-11 (2005).

4.

C. X. Han, N. Kasai, and K. Torimitsu, "CA2: the most vulnerable sector tobicuculline exposure in rat hippocampal slice cultures",
Neuroreport 16 (4), 333-336 (2005).

5.

W. P. Hu, H. Nakashima, K. Furukawa, Y. Kashimura, K. Ajito, Y. Q. Liu, D. B. Zhu,
and K. Torimitsu, "A self-assembled nano optical switch and transistor based on arigid conjugated polymer, thioacetyl-end-functionalized poly(para-phenylene
ethynylene)",J. Am. Chem. Soc. 127 (9), 2804-2805 (2005).

6.

M. Iwai, Y. Tateishi, M. Hattori, A. Mizutani, T. Nakamura, A. Futatsugi, T. Inoue, T.
Furuichi, T. Michikawa, and K. Mikoshiba, "Molecular cloning of mouse type 2 andtype 3 inositol 1,4,5-trisphosphate receptors and identification of a novel type 2
receptor splice variant",
J. Biol. Chem. 280 (11), 10305-10317 (2005).

7.

N. Kasai, C. X. Han, and K. Torimitsu, "Hydrogen peroxide distribution and neuronalcell death in a rat hippocampal slice",Sens. Actuator B-Chem. 108 (1-2), 746-750 (2005).

8.

H. Nakashima, K. Furukawa, K. Ajito, Y. Kashimura, and K. Torimitsu, "Selective
chemisorption of end-functionalized conjugated polymer on macro- andnanoscale-surfaces",－77－Research Activities in NTT Basic Research Laboratories Vol. 16 (September 2006)

Langmuir 21 (2), 511-515 (2005).
9.

Z. H. Zhang, K. Sumitomo, and F. Lin, "Observation of B segregation on Si(113) byscanning tunneling microscopy",
Ultramicroscopy 105 (1-4), 16-21 (2005).

10.

Z. H. Zhang and K. Sumitomo, "Boronizing structures of Si(113) surfaces",
Surf. Sci. 576 (1-3), 83-88 (2005).

Physical ScienceLaboratory
Nanodevices Research Group1.

T. Akiyama, H. Kageshima, M. Uematsu, and T. Ito, "Theoretical investigation ofoxygen diffusion in compressively strained high-density alpha-quartz",
Jpn. J. Appl. Phys. Part 1 - Regul. Pap. Brief Commun. Rev. Pap. 44 (10), 7427-7429(2005).

2.

T. Akiyama and H. Kageshima, "Reaction mechanisms of oxygen at SiO2/Si(100)interface",
Surf. Sci. 576 (1-3), L65-L70 (2005).

3.

Z. A. Burhanudin, R. Nuryadi, Y. Ishikawa, M. Tabe, and Y. Ono, "Thermally-induced
formation of Si wire array on an ultrathin (111) silicon-on-insulator substrate",Appl. Phys. Lett. 87 (12), 121905 (2005).

4.

N.
Clement
andH.
Inokawa,"Foundrymetal-oxide-semiconductor
field-effect-transistor electrometer for single-electron detection",
Jpn. J. Appl. Phys. Part 1 - Regul. Pap. Brief Commun. Rev. Pap. 44 (7A), 4855-4858(2005).

5.

Y. Ono, K. Nishiguchi, H. Inokawa, S. Horiguchi, and Y. Takahashi, "Charge-state
control of phosphorus donors in silicon-on-insulator metal-oxide-semiconductor
field-effect transistor",
Jpn. J. Appl. Phys. Part 1 - Regul. Pap. Short Notes Rev. Pap. 44 (4B), 2588-2591(2005).

6.

Y. Ono, A. Fujiwara, K. Nishiguchi, H. Inokawa, and Y. Takahashi, "Manipulation anddetection of single electrons for future information processing",
J. Appl. Phys. 97 (3), 031101 (2005).

7.

M. Tsuda, H. Arai, M. Takahashi, H. Ohtsuka, Y. Sakurai, K. Sumitomo, and H.
Kageshima, "Electrode performance of layered LiNi0.5Ti0.5O2 prepared by ion
exchange",－78－

Research Activities in NTT Basic Research Laboratories Vol. 16 (September 2006)

J. Power Sources 144 (1), 183-190 (2005).
8.

K. Uchida, H. Kageshima, and H. Inokawa, "Charge-injection effects in a single 4,4''-terphenyldithiol molecule",
Jpn. J. Appl. Phys. Part 1 - Regul. Pap. Brief Commun. Rev. Pap. 44 (12), 8759-8763(2005).

9.

M. Uematsu, H. Kageshima, and K. Shiraishi, "Effect of nitrogen on diffusion insilicon oxynitride",
Jpn. J. Appl. Phys. Part 1 - Regul. Pap. Brief Commun. Rev. Pap. 44 (11), 7756-7759(2005).

10.

M. Uematsu, "Self-diffusion and impurity diffusion in silicon dioxide",
J. Phase Equilib. Diffus. 26 (5), 547-554 (2005).

11.

M. Uematsu, "Unified simulation of diffusion in silicon and silicon dioxide", inDiffusion In Materials: Dimat 2004, Pt 1and 2, Defect And Diffusion Forum Vol.
237-240 (Trans Tech Publications Ltd, Zurich-Uetikon, 2005), pp. 38-49.

Nanostructure Technology Research Group1.

Y. Furukawa, K. Hoshina, K. Yamanouchi, and H. Nakano, "Ejection of triatomic
hydrogen molecular ion from methanol in intense laser fields",
Chem. Phys. Lett. 414 (1-3), 117-121 (2005).

2.

M. Nagase, K. Nakamatsu, S. Matsui, and H. Namatsu, "Carbon multiprobes withnanosprings integrated on Si cantilever using focused-ion-beam technology",
Jpn. J. Appl. Phys. Part 1 - Regul. Pap. Brief Commun. Rev. Pap. 44 (7B), 5409-5412(2005).

3.

K. Nakamatsu, M. Nagase, J. Y. Igaki, H. Namatsu, and S. Matsui, "Mechanicalcharacteristics and its annealing effect of diamondlike-carbon nanosprings fabricatedby focused-ion-beam chemical vapor deposition",
J. Vac. Sci. Technol. B 23 (6), 2801-2805 (2005).

4.

K. Nakamatsu, M. Nagase, H. Namatsu, and S. Matsui, "Mechanical characteristics of
diamond-like-carbon nanosprings fabricated by focused-ion-beam chemical vapor
deposition",
Jpn. J. Appl. Phys. Part 2 - Lett. Express Lett. 44 (37-41), L1228-L1230 (2005).

5.

K. Nakamatsu, K. Watanabe, K. Tone, H. Namatsu, and S. Matsui, "Nanoimprint andnanocontact technologies using hydrogen silsesquioxane",
J. Vac. Sci. Technol. B 23 (2), 507-512 (2005).

6.

H. Namatsu and M. Sato, "Supercritical improvement of resist patterns by introducing－79－Research Activities in NTT Basic Research Laboratories Vol. 16 (September 2006)

functional molecules",Jpn. J. Appl. Phys. Part 2 - Lett. Express Lett. 44 (1-7), L227-L229 (2005).
7.

K. Nishiguchi, O. Crauste, H. Namatsu, S. Horiguchi, Y. Ono, A. Fujiwara, Y.
Takahashi, and H. Inokawa, "Back-gate effect on Coulomb blockade insilicon-on-insulator trench wires",Jpn. J. Appl. Phys. Part 1 - Regul. Pap. Brief Commun. Rev. Pap. 44 (10), 7717-7719(2005).

8.

Y. Ohminami, S. Suzuki, N. Matsudaira, T. Nomura, W. J. Chun, K. Ijima, M.
Nakamura, K. Mukasa, M. Nagase, and K. Asakura, "Preparation and characterizationof a microfabricated oxide-on-oxide catalyst of alpha-Sb2O4/VSbO4",
Bull. Chem. Soc. Jpn. 78 (3), 435-442 (2005).

9.

H. Okamoto, T. Yamada, H. Miyazaki, T. Nakanishi, K. Takeda, K. Usui, I. Obataya,
H. Mihara, H. Azehara, W. Mizutani, K. Hashimoto, H. Yamaguchi, and Y. Hirayama,"Difference in self-assembling morphology of peptide nanorings",
Jpn. J. Appl. Phys. Part 1 - Regul. Pap. Brief Commun. Rev. Pap. 44 (11), 8240-8248(2005).

10.

H. Okamoto, T. Akazaki, M. Ueki, and H. Yamaguchi, "Strongly enhanced sensitivityof piezoresistive cantilevers by utilizing the superconducting proximity effect",
Jpn. J. Appl. Phys. Part 2 - Lett. Express Lett. 44 (28-32), L893-L895 (2005).

11.

T. Sakata, H. Ishii, Y. Okabe, M. Nagase, T. Kamei, K. Kudou, M. Yano, and K.
Machida, "Anti-sticking effect of organic dielectric formed by electrodeposition in
microelectromechanical-system structures",Jpn. J. Appl. Phys. Part 1 - Regul. Pap. Brief Commun. Rev. Pap. 44 (7B), 5732-5735(2005).

12.

T. Shimura, K. Yasutake, M. Umeno, and M. Nagase, "X-ray diffraction measurements
of internal strain in Si nanowires fabricated using a self-limiting oxidation process",
Appl. Phys. Lett. 86 (7), 071903 (2005).

13.

H. Yamaguchi, A. K. Das, A. Ney, T. Hesjedal, C. Pampuch, D. M. Schaadt, and R.
Koch, "From ferro- to antiferromagnetism via exchange-striction of MnAs/GaAs(001)",
Europhys. Lett. 72 (3), 479-485 (2005).

14.

H. Yamaguchi, S. Miyashita, and Y. Hirayama, "Force/displacement detection using
quantum effects in InAs/Al0.5Ga0.5Sb two-dimensional electron systems", inCompound Semiconductors 2004, Proceedings, Institute Of Physics Conference SeriesVol. 184 (Iop Publishing Ltd, Bristol, 2005), pp. 187-192.

15.

H. Yamaguchi, Y. Hirayama, S. Miyashita, and S. Ishihara, "Force/displacement
detection using quantum transport in InAs/AlGaSb two-dimensional heterostructures",－80－Research Activities in NTT Basic Research Laboratories Vol. 16 (September 2006)

Appl. Phys. Lett. 86 (5), 052106 (2005).
16.

T. Yamaguchi and H. Namatsu, "Graphoepitaxy of diblock copolymer on
micropatterned substrates",J. Photopolym Sci. Technol. 18 (3), 421-423 (2005).

Quantum Solid State Physics Research Group
1.

D. G. Austing, R. J. A. Hill, A. Patane, P. C. Main, M. Henini, L. Eaves, and S.
Tarucha, "Transport properties of gated sub-micron mesas incorporating InAs
self-assembled quantum dots that conduct near zero bias",
Physica E 26 (1-4), 482-485 (2005).

2.

W. R. Clarke, A. P. Micolich, A. R. Hamilton, M. Y. Simmons, K. Muraki, and Y.
Hirayama, "Fabrication and characterization of a 2D hole system a in novel (311)A
GaAsSISFET",Microelectron. J. 36 (3-6), 327-330 (2005).

3.

N. Goel, J. Graham, J. C. Keay, K. Suzuki, S. Miyashita, M. B. Santos, and Y.
Hirayama, "Ballistic transport in InSb mesoscopic structures",Physica E 26 (1-4), 455-459 (2005).

4.

K. Hashimoto, K. Muraki, N. Kumada, T. Saku, and Y. Hirayama, "Effects ofinversion asymmetry on electron-nuclear spin coupling in semiconductor
heterostructures: Possible role of spin-orbit interactions",
Phys. Rev. Lett. 94 (14), 146601 (2005).

5.

H. Ishizaki, T. Akiyama, K. Nakamura, K. Shiraishi, A. Taguchi, and T. Ito,
"Theoretical investigation of phase transition on GaAs(001)-c(4 x 4) surface",Appl. Surf. Sci. 244 (1-4), 186-189 (2005).

6.

T. Ito, K. Asano, T. Akiyama, K. Nakamura, K. Shiraishi, and A. Taguchi, "An abinitio-based approach to Ga adatom migration on GaAs(n 1 1)A-(001) non-planar
surfaces",
Appl. Surf. Sci. 244 (1-4), 178-181 (2005).

7.

K. Iwata, M. Morino, M. Suzuki, A. Fukuda, A. Sawada, Z. F. Ezawa, N. Kumada, and
Y. Hirayama, "Anisotropic magnetotransport around the v=1 bilayer quantum Hall
state",
J. Phys. Chem. Solids 66 (8-9), 1556-1559 (2005).

8.

N. Kumada, K. Muraki, K. Hashimoto, and Y. Hirayama, "Spin degree of freedom in
the nu=1 bilayer electron system investigated by nuclear spin relaxation",
Phys. Rev. Lett. 94 (9), 096802 (2005).

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Research Activities in NTT Basic Research Laboratories Vol. 16 (September 2006)

9.

H. W. Liu, T. Fujisawa, T. Hayashi, and Y. Hirayama, "Pauli spin blockade incotunneling transport through a double quantum dot",
Phys. Rev. B 72 (16), 161305 (2005).

10.

K. Onomitsu, H. Fukui, T. Maeda, Y. Hirayama, and Y. Horikoshi, "Spatially separated
Mn and Be doping for high hole concentration in GaMnAs by using MEE",
J. Cryst. Growth 278 (1-4), 699-703 (2005).

11.

S. Sasaki, T. Fujisawa, T. Hayashi, and Y. Hirayama, "Electrical pump-and-probe
study of spin singlet-triplet relaxation in a quantum dot",
Phys. Rev. Lett. 95 (5), 056803 (2005).

12.

S. Sasaki and S. Tarucha, "The Kondo effect enhanced by state degeneracy",
J. Phys. Soc. Jpn. 74 (1), 88-94 (2005).

13.

A. Taguchi, "First-principles investigations of Ga and As adsorption properties on a
GaAs(110) surface", in Compound Semiconductors 2004, Proceedings, Institute Of
Physics Conference Series Vol. 184 (Iop Publishing Ltd, Bristol, 2005), pp. 345-348.

14.

A. Taguchi, "First-principles investigations of surface reconstructions of an
InAs(111)B surface",
J. Cryst. Growth 278 (1-4), 468-472 (2005).

15.

A. Taguchi, H. Kageshima, and K. Wada, "First-principles investigations of
nitrogen-doping effects on defect aggregation processes in Czochralski Si",
J. Appl. Phys. 97 (5), 053514 (2005).

16.

A. Taguchi and K. Shiraishi, "Surface reconstructions and stabilizing mechanism of
the GaAs(311)A surface",
Phys. Rev. B 71 (3), 035349 (2005).

17.

D. Terasawa, S. Kozumi, A. Fukuda, A. Sawada, Z. F. Ezawa, N. Kumada, and Y.
Hirayama, "Pseudospin domain of v=1 double-layer quantum Hall state nearcommensurate-incommensurate transition",
J. Phys. Chem. Solids 66 (8-9), 1560-1562 (2005).

18.

G. Yusa, K. Hashimoto, K. Muraki, T. Saku, and Y. Hirayama, "Resistance oscillations
by electron-nuclear spin coupling in microscopic quantum Hall devices",
Jpn. J. Appl. Phys. Part 1 - Regul. Pap. Short Notes Rev. Pap. 44 (4B), 2669-2671(2005).

19.

G. Yusa, K. Muraki, K. Takashina, K. Hashimoto, and Y. Hirayama, "Controlled
multiple quantum coherences of nuclear spins in a nanometre-scale device,"
Nature 434 (7036), 1001-1005 (2005).

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Superconducting Quantum Physics Research Group1.

P. Bertet, I. Chiorescu, G. Burkard, K. Semba, Cjpm Harmans, D. P. DiVincenzo, and J.
E. Mooij, "Dephasing of a superconducting qubit induced by photon noise",Phys. Rev. Lett. 95 (25), 257002 (2005).

2.

B. Chesca, M. Seifried, T. Dahm, N. Schopohl, D. Koelle, R. Kleiner, and A. Tsukada,"Observation of Andreev bound states in bicrystal grain-boundary Josephson junctionsof the electron-doped superconductor La2-xCexCuO4-y",Phys. Rev. B 71 (10), 104504 (2005).

3.

T. Kutsuzawa, H. Tanaka, S. Saito, H. Nakano, K. Semba, and H. Takayanagi,"Coherent control of a flux qubit by phase-shifted resonant microwave pulses",Appl. Phys. Lett. 87 (7), 073501 (2005).

Spintronics Research Group1.

T. Akazaki, H. Nakano, J. Nitta, and H. Takayanagi, "Observation of enhanced thermal
noise due to multiple Andreev reflection in ballistic InGaAs-based superconducting
weak links",
Appl. Phys. Lett. 86 (13), 132505 (2005).

2.

Y. Asari, K. Takeda, and H. Tamura, "New shell structures and their ground electronic
states in spherical quantum dots (II) under magnetic field",
Jpn. J. Appl. Phys. Part 1 - Regul. Pap. Short Notes Rev. Pap. 44 (4A), 2043-2052(2005).

3.

T. Bauch, E. Hurfeld, V. M. Krasnov, R. Delsing, H. Takayanagi, and T. Akazaki,"Correlated quantization of supercurrent and conductance in a superconducting
quantum point contact",
Phys. Rev. B 71 (17), 174502 (2005).

4.

B. R. Choi, A. E. Hansen, T. Kontos, C. Hoffmann, S. Oberholzer, W. Belzig, C.
Schonenberger, T. Akazaki, and H. Takayanagi, "Shot-noise and conductancemeasurements of transparent superconductor/two-dimensional electron gas junctions",
Phys. Rev. B 72 (2), 024501 (2005).

5.

M. Kawamura, H. Yaguchi, N. Kikugawa, Y. Maeno, and H. Takayanagi, "Tunnelingproperties at the interface between superconducting Sr2RuO4 and a Ru
microinclusion",
J. Phys. Soc. Jpn. 74 (2), 531-534 (2005).

6.

V. M. Krasnov, T. Bauch, S. Intiso, E. Hurfeld, T. Akazaki, H. Takayanagi, and P.
Delsing, "Collapse of thermal activation in moderately damped Josephson junctions",
Phys. Rev. Lett. 95 (15), 157002 (2005).

－83－Research Activities in NTT Basic Research Laboratories Vol. 16 (September 2006)

7.

Y. P. Lin, T. Koga, and J. Nitta, "Effect of an InP/In0.53Ga0.47As interface on spin-orbit
interaction in In0.52Al0.48As/In0.53Ga0.47As heterostructures",Phys. Rev. B 71 (4), 045328 (2005).

8.

F. E. Meijer, A. F. Morpurgo, T. M. Klapwijk, and J. Nitta, "Universal spin-induced
time reversal symmetry breaking in two-dimensional electron gases with Rashba
spin-orbit interaction",
Phys. Rev. Lett. 94 (18), 186805 (2005).

9.

A. K. M. Newaz, W. Song, E. E. Mendez, Y. Lin, and J. Nitta, "Shot-noisecharacteristics of triple-barrier resonant-tunneling diodes",Phys. Rev. B 71 (19), 195303 (2005).

10.

J. Nitta and M. Steiner, "Magnetization properties of microstructured NiFe rings
investigated using semiconductor/ferromagnet hybrid structures",J. Supercond. 18 (3), 331-334 (2005).

11.

J. Nitta and M. Steiner, "Semiconductor/ferromagnet hybrid devices to probemagnetisation states in microstructured NiFe rings",
IEE Proc.-Circuit Device Syst. 152 (4), 297-300 (2005).

12.

J. Ohe, M. Yamamoto, T. Ohtsuki, and J. Nitta, "Mesoscopic Stern-Gerlach spin filterby nonuniform spin-orbit interaction",
Phys. Rev. B 72 (4), 041308 (2005).

13.

A. Richter, K. Matsuda, T. Akazaki, T. Saku, H. Tamura, Y. Hirayama, and H.
Takayanagi, "Transport properties of a lateral semiconductor quantum dot defined by asingle connected metallic front-gate",
Physica E 25 (4), 472-478 (2005).

14.

H. Tamura and L. Glazman, "Tunable Kondo screening in a quantum dot device",
Phys. Rev. B 72 (12), 121308 (2005).

15.

M. Yamaguchi, S. Nomura, D. Sato, T. Akazaki, H. Tamura, and H. Takayanagi,"Photoluminescence measurements in Be-delta-doped back-gated quantum well",
Surf. Sci. 583 (1), 94-99 (2005).

16.

M. Yamamoto, J. Ohea, T. Ohtsuki, J. Nitta, and B. Kramer, "Spin-polarization in a
3-terminal conductor induced by Rashba spin-orbit coupling",
Physica E 29 (3-4), 490-494 (2005).

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Research Activities in NTT Basic Research Laboratories Vol. 16 (September 2006)

Optical Science Laboratory
Quantum Optical State Control Research Group1.

E. Diamanti, H. Takesue, T. Honjo, K. Inoue, and Y. Yamamoto, "Performance ofvarious quantum-key-distribution systems using 1.55-mu m up-conversion
single-photon detectors",
Phys. Rev. A 72 (5), 052311 (2005).

2.

T. Honjo and K. Inoue, "Plug & play quantum key distribution using modulation
sidebands for shifting frequency",
Jpn. J. Appl. Phys. Part 1 - Regul. Pap. Brief Commun. Rev. Pap. 44 (9A), 6550-6552(2005).

3.

K. Inoue and T. Honjo, "Robustness of differential-phase-shift quantum key
distribution against photon-number-splitting attack",
Phys. Rev. A 71 (4), 042305 (2005).

4.

K. Inoue, "Quantum key distribution using a series of quantum correlated photon
pairs",
Phys. Rev. A 71 (3), 032301 (2005).

5.

A. Ishizawa and H. Nakano, "Fluctuation of the carrier-envelope phase of a few-cycle
laser pulse from a chirped-pulse amplification system with the gas pressure in ahollow fiber",
Jpn. J. Appl. Phys. Part 1 - Regul. Pap. Brief Commun. Rev. Pap. 44 (8), 6039-6041(2005).

6.

Y. Katagiri, H. Takesue, and E. Hashimoto, "Wavelength-scanning optical bandpass
filters based on optomechatronics for optical-frequency sweepers",
IEEE Trans. Ind. Electron. 52 (4), 992-1004 (2005).

7.

T. Kubo and Y. Tokura, "Electron transport in magnetic-field-induced
quasi-one-dimensional electron systems in semiconductor nanowhiskers",
Physica E 29 (3-4), 525-529 (2005).

8.

T. Kubo and Y. Tokura, "Many-body effects on tunneling of electrons inmagnetic-field-induced quasi-one-dimensional electron systems in semiconductor
nanowhiskers",
J. Phys. Soc. Jpn. 74 (2), 519-522 (2005).

9.

M. W. Jack and M. Yamashita, "Maximal entanglement of two spinor Bose-Einsteincondensates",
Phys. Rev. A 71 (3), 033619 (2005).

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Research Activities in NTT Basic Research Laboratories Vol. 16 (September 2006)

10.

M. W. Jack and M. Yamashita, "Bose-Hubbard model with attractive interactions",
Phys. Rev. A 71 (2), 023610 (2005).

11.

C. Langrock, E. Diamanti, R. V. Roussev, Y. Yamamoto, M. M. Fejer, and H. Takesue,"Highly efficient single-photon detection at communication wavelengths by use of
upconversion in reverse-proton-exchanged periodically poled LiNbO3 waveguides",Opt. Lett. 30 (13), 1725-1727 (2005).

12.

K. Maruyama, F. Morikoshi, and V. Vedral, "Thermodynamical detection ofentanglement by Maxwell's demons",
Phys. Rev. A 71 (1), 012108 (2005).

13.

H. Oberst, Y. Tashiro, K. Shimizu, and F. Shimizu, "Quantum reflection of H* onsilicon",Phys. Rev. A 71 (5), 052901 (2005).

14.

H. Oberst, D. Kouznetsov, K. Shimizu, J. Fujita, and F. Shimizu, "Fresnel diffraction
mirror for an atomic wave",
Phys. Rev. Lett. 94 (1), 013203 (2005).

15.

H. Takesue, E. Diamanti, T. Honjo, C. Langrock, M. M. Fejer, K. Inoue, and Y.
Yamamoto, "Differential phase shift quantum key distribution experiment over 105km
fibre",New J. Phys. 7, 232 (2005).

16.

H. Takesue and K. Inoue, "Generation of 1.5-mu m band time-bin entanglement using
spontaneous fiber four-wave mixing and planar light-wave circuit interferometers",
Phys. Rev. A 72 (4), 041804 (2005).

17.

H. Takesue and K. Inoue, "1.5-mu m band quantum-correlated photon pair generationin dispersion-shifted fiber: suppression of noise photons by cooling fiber",
Opt. Express 13 (20), 7832-7839 (2005).

18.

H. Takesue, K. Inoue, O. Tadanaga, Y. Nishida, and M. I. Asobe, "Generation ofpulsed polarization-entangled photon pairs in a 1.55-mu m band with a periodicallypoled lithium niobate waveguide and an orthog onal polarization delay circuit",
Opt. Lett. 30 (3), 293-295 (2005).

19.

Y. Tokunaga, T. Yamamoto, M. Koashi, and N. Imoto, "Simple experimental schemeof preparing a four-photon entangled state for the teleportation-based realization of alinear optical controlled-NOT gate",
Phys. Rev. A 71 (3), 030301 (2005).

20.

B. Y. Zhang, G. S. Solomon, M. Pelton, J. Plant, C. Santori, J. Vuckovic, and Y.
Yamamoto, "Fabrication of InAs quantum dots in AlAs/GaAs DBR pillar－86－

Research Activities in NTT Basic Research Laboratories Vol. 16 (September 2006)

microcavities for single photon sources",
J. Appl. Phys. 97 (7), 073507 (2005).

Quantum Optical Physics Research Group
1.

N. I. Cade, H. Gotoh, H. Kamada, T. Tawara, T. Sogawa, H. Nakano, and H. Okamoto,"Charged exciton emission at 1.3 µm from single InAs quantum dots grown bymetalorganic chemical vapor deposition",
Appl. Phys. Lett. 87 (17), 172101 (2005).

2.

H. Gotoh, T. Akasaka, T. Tawara, Y. Kobayashi, T. Makimoto, and H. Nakano,"Efficient observation of narrow isolated photoluminescence spectra from spatiallylocalized excitons in InGaN quantum wells",
Jpn. J. Appl. Phys. Part 2 - Lett. Express Lett. 44 (42-45), L1381-L1384 (2005).

3.

H. Gotoh, H. Kamada, H. Nakano, T. Saitoh, H. Ando, and J. Temmyo, "Opticalnonlinearity induced by exciton-biexciton coherent effects in InGaAs quantum dots",
Appl. Phys. Lett. 87 (10), 102101 (2005).

4.

H. Gotoh, H. Kamada, T. Saitoh, H. Ando, and J. Temmyo, "Exciton absorption
properties of coherently coupled exciton-biexciton systems in quantum dots",
Phys. Rev. B 71 (19), 195334 (2005).

5.

T. Hattori, T. Yogi, Y. Hama, N. Watanabe, and R. Yano, "Chirp control of free carrier
injection in GaAs using femtosecond optical pulses",
Jpn. J. Appl. Phys. Part 1 - Regul. Pap. Brief Commun. Rev. Pap. 44 (8), 6101-6104(2005).

6.

S. Hughes, "Modified spontaneous emission and qubit entanglement from
dipole-coupled quantum dots in a photonic crystal nanocavity",
Phys. Rev. Lett. 94 (22), 227402 (2005).

7.

S. Hughes, "Quantum emission dynamics from a single quantum dot in a planar
photonic crystal nanocavity",
Opt. Lett. 30 (11), 1393-1395 (2005).

8.

S. Hughes, L. Ramunno, J. F. Young, and J. E. Sipe, "Extrinsic optical scattering loss
in photonic crystal waveguides: Role of fabrication disorder and photon groupvelocity",
Phys. Rev. Lett. 94 (3), 033903 (2005).

9.

A. Nakamura, J. Ishihara, S. Shigemori, K. Yamamoto, T. Aoki, H. Gotoh, and J.
Temmyo, "Zn1-xCdxO/ZnO heterostructures for visible light emitting devices",
Jpn. J. Appl. Phys. Part 2 - Lett. Express Lett. 44 (1-7), L4-L6 (2005).

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Research Activities in NTT Basic Research Laboratories Vol. 16 (September 2006)

10.

K. Oguri, Y. Okano, T. Nishikawa, and H. Nakano, "Transient observation of extended
x-ray absorption fine structure in laser-melted Si by using femtosecond
laser-produced-plasma soft x-ray",Appl. Phys. Lett. 87 (1), 011503 (2005).

11.

K. Tateno, H. Gotoh, and H. Nakano, "Nanoholes formed by Au particles digging into
GaAs and InP substrates by reverse vapor-liquid-solid mechanism",
Jpn. J. Appl. Phys. Part 2 - Lett. Express Lett. 44 (50-52), L1553-L1555 (2005).

12.

K. Tateno, H. Gotoh, and Y. Watanabe, "Nanoholes in InP and C-60 layers on GaAs
substrates by using AlGaAs nanowire templates",
Jpn. J. Appl. Phys. Part 2 - Lett. Express Lett. 44 (12-15), L428-L431 (2005).

13.

R. Yano and H. Gotoh, "Tunable terahertz electromagnetic wave generation using
birefringent crystal and grating pair",Jpn. J. Appl. Phys. Part 1 - Regul. Pap. Brief Commun. Rev. Pap. 44 (12), 8470-8473(2005).

14.

R. Yano, H. Gotoh, Y. Hirayama, S. Miyashita, Y. Kadoya, and T. Hattori, "Terahertz
wave detection performance of photoconductive antennas: Role of antenna structureand gate pulse intensity",
J. Appl. Phys. 97 (10), 103103 (2005).

Photonic Nano-Structure Research Group1.

E. Kuramochi, M. Notomi, S. Hughes, A. Shinya, T. Watanabe, and L. Ramunno,"Disorder-induced scattering loss of line-defect waveguides in photonic crystal slabs",
Phys. Rev. B 72 (16), 161318 (R)(2005).

2.

M. Notomi, A. Shinya, S. Mitsugi, G. Kira, E. Kuramochi, and T. Tanabe, "Opticalbistable switching action of Si high-Q photonic-crystal nanocavities",
Opt. Express 13 (7), 2678-2687 (2005).

3.

A. Shinya, S. Mitsugi, E. Kuramochi, and M. Notomi, "Ultrasmall multi-channel
resonant-tunneling filter using mode gap of width-tuned photonic-crystal waveguide",
Opt. Express 13 (11), 4202-4209 (2005).

4.

T. Tanabe, M. Notomi, S. Mitsugi, A. Shinya, and E. Kuramochi, "All-optical switches
on a silicon chip realized using photonic crystal nanocavities",
Appl. Phys. Lett. 87 (15), 151112 (2005).

5.

T. Tanabe, M. Notomi, S. Mitsugi, A. Shinya, and E. Kuramochi, "Fast bistableall-optical switch and memory on a silicon photonic crystal on-chip",Opt. Lett. 30 (19), 2575-2577 (2005).

－88－Research Activities in NTT Basic Research Laboratories Vol. 16 (September 2006)

6.

H. Taniyama, M. Notomi, and Y. Yoshikuni, "Propagation characteristics of
one-dimensional photonic crystal slab waveguides and radiation loss",
Phys. Rev. B 71 (15), 153103 (2005).

7.

A. Yokoo and S. Sasaki, "Oxidation patterning of GaAs by nanoelectrodelithography",
Jpn. J. Appl. Phys. Part 1 - Regul. Pap. Short Notes Rev. Pap. 44 (2), 1119-1122(2005).

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Editorial Committee
Hiroo Omi
Hisashi Sato
Atsushi Yokoo
Kazuaki Furukawa
Hirotaka Tanaka
Kiyoshi Kanisawa
NTT Basic Research Laboratories
3-1 Morinosato Wakamiya, Atsugi-shi
Kanagawa 243-0198 Japan
Phone: +81-46-240-3312
URL: http://www.brl.ntt.co.jp/
E-mail: katsudou-mail@will.brl.ntt.co.jp