Research Activities
in
NTT Basic Research Laboratories
Volume 14
Fiscal 2003

June 2004
NTT Basic Research Laboratories,
Nippon Telegraph and Telephone Corporation (NTT)http://www.brl.ntt.co.jp

Electron microscope image of the globe

World’s smallest globe (Nano-globe) made using electron beam
We made the world’s smallest globe as a demonstration of a new three-dimensional
nanofabrication technique using electron-beam lithography. A sphere sample was rotated, andthe map of the world was written on it. The minimum linewidth is 10 nm, which corresponds
to 2 km. Our technique significantly improves the resolution of 3D fabrication. (Page 19)

NTT-original High-Tc MBE

Superconducting bandpass filters

High-Tc Superconducting Filters for Wireless Communication
Superconducting microwave devices can realize future wireless communication systems withhigher selectivity, higher sensitivity and smaller power consumption. We firstly fabricatedmicrowave bandpass filters of a high-temperature superconducting oxide NdBa2Cu3O7, which
is superior to the widely-used superconductor YBa2Cu3O7 in various properties including thesuperconducting transition temperature Tc and the surface resistance Rs. The filters were
fabricated using high-quality films obtained by NTT-original thin film-growth technique formolecular-beam epitaxy (MBE) of high-Tc superconducting oxides. Improving theperformance of the new filters, we may realize application of superconducting filters fortransmitting parts in wireless systems, which is supposed to give remarkable reduction in sizeand power consumption of the systems.

Averaged number of electrons

0

e-

e-

1.0

z

0 −i 1

e-

2

0 +i1
2

θ

e-

e-

0.5

y

x
e0.0
0.0

0.5

Beff
1.0

1.5

e-

2.0

Pulse length (ns)

Coherent charge oscillation (inset: sample set-up)

1

Bloch sphere (rotation gate operation)

Semiconductor charge qubit
Coherent charge oscillation in a semiconductor double quantum dot is induced by voltage
pulse, which corresponds to rotation gate operation on the charge qubit. In the Bloch sphere
representation of the qubit, the pseud spin rotates along the effective magnetic field. (Page28)

sapphire
SiO2/ZrO2 mirror←

InGaN QWs

bonding←bonding

AlGaN
SiC

SiO2/ZrO2 mirror

selective
dry etching

sapphire

Cross-sectional SEM imageof fabricated VCSEL

Fabrication procedure of III-Nitride VCSELs

GaN-Based Vertical Cavity Surface Emitting Lasers
A serious problem with GaN-based vertical cavity surface emitting lasers (VCSEL) is that the
crystal quality of the cavity layer is degraded by the large lattice mismatch between the
GaN-based mirror layers. A high quality GaN-based VCSEL was fabricated and its lasing
action at room temperature demonstrated by using a wafer bonding technique with a
GaN-based cavity layer and oxide-based mirrors that were prepared separately. (Page 33)

From Science to Innovative Technology
We sincerely appreciate your interest in NTT Basic
Research Laboratories.
Basic Research Laboratories (BRL) was established in
1998, when the former BRL was divided into theCommunication Science Laboratories and laboratories
devoted to basic research in the area of hardware.
BRL’s mission is to 1) discover novel concepts in
network technology that will overcome present
limitations in speed, capacity, and size and 2) pioneer
basic technology that will become a foundation for
future business.
Two of our most promising projects are quantum
information processing and the nano-bio project.
The main topics of research in quantum information
processing are quantum computation and quantum
cryptography. Taking advantage of our ability to run projects ranging in scope from small to huge,
NTT BRL’s research on quantum bits using solid-state components has achieved world-class success.
In quantum cryptography, we are accelerating research using single photons. The nano-bio projectfuses neuroscience, bio-molecular science, and nanotechnology in the search for hybrids ofcomprising molecular and protein-based devices.
While promoting these projects, we are also conducting exploratory research in the following
fields: quantum correlation within low-dimensional electron systems, systems that use the spin ofindividual electrons as an information carrier, material design that uses quantum dots as building
blocks, electrical properties of carbon nanotubes, and MEMS (microelectromechanical systems)
related to superconductivity. As we research these fields, we emphasize the need for goodcommunication between researchers and managers as a way to judge whether or not they will bear
fruit in the future.
Alongside such exploratory research, we are putting effort into creating innovative technology.
For instance, in the field of diamond semiconductors, whose ability to handle high power andhigh-frequency waves make them promising for various applications, we have developed technologythat produces diamond thin films of high quality and succeeded in operating a diamond transistor at
80 GHz. In addition, we are engaged in research on single-electron devices for their extremely low
power consumption, photonic crystal for use as active optical circuits, and optical devices using
wide-bandgap semiconductor materials. We see these as innovative technologies that will
overcome the limitations of the present network.
To maintain fruitful research activities, we believe it is essential to have an open research policy.
We not only keep in close touch with other NTT Laboratories, but also run various scientificexchange programs with institutes inside and outside Japan. Our collaborative work on quantum
dots and quantum bits with Delft University and Stanford University has led to several interesting
discoveries, and nano-bio research with the University of Tokyo has also been producing promising
results. Moreover, we hold International Symposiums, Summer Schools, and International
Advisory Board Meetings to disseminate our research information worldwide and encourage greater
understanding of it.
This brochure provides annual review of our research activities and achievements in 2003.
hope it will contribute to the promotion of scientific exchange throughout the world.
June 2004

Dr. Hideaki Takayanagi
Director
NTT Basic Research Laboratories
3-1 Morinosato-Wakamiya, Atsugi-shi,
Kanagawa 243-0198, Japan
Phone: +81 46 240 3300
Fax: +81 46 270 2358
Email: takayanagi@nttbrl.jp

We

Contents
page

Member List .............................................................................................................................................. 1
I. Research Topics◆Overview of Device Physics Research................................................................................................... 17♦ Effect of the Si/ SiO2 Interface on Si diffusion in SiO2
♦ World’s Smallest Globe (Nano-Globe) made using electron beam
♦ Nano-four-point-probe systems♦ Semiconductor Nanowires◆Overview of Material Science Research ................................................................................................ 22♦ Carrier Injection and Transport of Conductive Polymer-Based Devices♦ Discovery of non-doped superconductors in lanthanum based copper oxide♦ Multiphoton absorption observed in a superconducting flux qubit♦ Control of magnetization states in micro-structured ferromagnetic rings◆Overview of Quantum Physics and Electronics Research...................................................................... 27♦ Semiconductor Charge Qubit♦ Microwave Performance of Diamond Field-Effect Transistor♦ Nitride Heterojunction Bipolar Transistors for High-Power Applications◆Overview of Quantum Optics and Optical Materials Research ............................................................. 31♦ Differential-Phase-Shift Quantum Key Distribution♦ GaN-Based Vertical Cavity Surface Emitting Lasers♦ Penrose-lattice Photonic Quasicrystal Laser

II. Data◆International Symposium on Mesoscopic Superconductivity and Spintronics--- In the light of Quantum Computation --- .......................................................................................... 35◆International Symposium on Functional Semiconductor Nanosystems (FSNS2003) ............................ 36◆Science Plaza 2003................................................................................................................................. 37◆Award Winner’s List............................................................................................................................... 38◆In-house Award Winner’s List................................................................................................................ 39◆List of Visitor’s Talks ............................................................................................................................. 40◆Research Activities of Basic Research Laboratories in 2003 ................................................................. 44◆List of Invited Talks at International Conferences ................................................................................. 46

Member List
As of March 31, 2004(*/ left NTT BRL in the middle of the year)

NTT Basic Research Laboratories
Director, Dr. Hideaki Takayanagi
Dr. Sunao Ishihara (~ June 30, 2003)

Research Planning Section

Senior Research Scientist, Supervisor,

Dr. Itaru Yokohama

Senior Research Scientist, Supervisor,

Dr. Yasuyuki Kobayashi

Senior Research Scientist,

Dr. Yuichi Harada

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

NTT Research Professor
Prof. Nobuyuki Imoto(The Graduate University for Advanced Studies)Prof. Masahito Ueda
(Tokyo Institute of Technology)
Prof. Seigo Tarucha(The University of Tokyo)
Dr. Fujio Shimizu(The University of Electro-Communications)
Prof. Yoshihisa Yamamoto(Stanford University, U.S.A)-1-

Device Physics Laboratory

Executive Manager,

Dr. Yasuo Takahashi
Dr. Koji Sumitomo
Takeshi Karasawa

Silicon Nanodevices Research Group:
Dr. Yasuo Takahashi (Group Leader)Dr. Hiroshi Inokawa
Dr. Seiji Horiguchi*
Dr. Yukinori Ono
Dr. Akira Fujiwara
Dr. Hiroyuki Teramae
Dr. Katsuhiko Nishiguchi
Nanostructure Technology Research Group:
Dr. Hideo Namatsu (Group Leader)
Dr. Masao Nagase
Dr. Kenji Yamazaki
Toru Yamaguchi
Surface Science Research Group:
Dr. Yoshikazu Homma (Group Leader)
Dr. Yoshihiro Kobayashi
Dr. Yoshio Watanabe
Hiroki Hibino
Dr. Tomoaki Kawamura
Dr. Hiroo Omi
Dr. Satoru Suzuki
Akio Tokura
Dr. Satyaban Bhunia*-2-

Dr. Masashi Uematsu
Dr. Hiroyuki Kageshima
Dr. Nicolas Clement

Junzo Hayashi

Dr. Fumihiko Maeda
Dr. Prabhakaran Kuniyil
Dr. Kenichi Kanzaki

Materials Science Laboratory

Executive Manager,

Dr. Masao Morita
Dr. Kazuhiro Igeta

Molecular and Bio Science Research Group:
Dr. Keiichi Torimitsu (Group Leader)
Dr. Keisuke Ebata
Dr. Yasuhiko Jimbo*
Dr. Katsuhiro Ajito
Dr. Nahoko Kasai
Dr. Yoshiaki Kashimura
Dr. Hiroshi Nakashima
Dr. Chunxi Han
Dr. Wenping Hu*
Superconducting Thin Films Research Group:
Dr. Masao Morita (Group Leader) Dr. Michio Naito*
Dr. Hideki Yamamoto
Dr. Hiroyuki Shibata
Dr. Shin-ichi Karimoto
Dr. Kenji Ueda
Dr. Akio Tsukada
Superconducting Quantum Physics Research Group:
Dr. Kouichi Semba (Group Leader)
Dr. Azusa Matsuda
Dr. Tatsushi Akazaki
Dr. Hiroyuki Tamura
Dr. Tetsuya Mukai
Dr. Shiro Saito
Dr. Andreas Richter*
Dr. Taro Eichler
Dr. Alexander Kasper
Spintronics Research Group:
Dr. Junsaku Nitta (Group Leader)
Dr. Yoshiaki Sekine
Dr. Yiping Lin-3-

Dr. Kazuaki Furukawa
Akiyoshi Shimada
Touichiro Goto

Dr. Hisashi SatoDr. Jose Kurian

Dr. Hayato Nakano
Hirotaka Tanaka
Dr. Masumi YamaguchiPhysical Science Laboratory

Executive Manager,

Dr. Yoshiro Hirayama
Masami Kumagai

Quantum Solid State Physics Research Group:
Dr. Yoshiro Hirayama (Group Leader)Dr. Hiroshi Yamaguchi
Dr. Toshimasa Fujisawa
Dr. Kiyoshi Kanisawa
Dr. Satoshi Sasaki
Dr. Kyoichi Suzuki
Dr. Toshiaki Hayashi
Dr. Takeshi Yusa
Dr. Lionel Houlet
Wide-Bandgap Semiconductor Research Group:
Dr. Toshiki Makimoto (Group Leader)
Dr. Makoto Kasu
Dr. Takashi Matsuoka
Yoshiharu Yamauchi
Dr. Tetsuya Akasaka
Dr. Yoshitaka Taniyasu
Dr. Chengxin Wang*
Quantum Optical State Control Research Group:
Dr. Yasuhiro Tokura (Group Leader)
Dr. Kyou Inoue
Dr. Kaoru Shimizu
Dr. Hiroki Takesue
Dr. Fumiaki Morikoshi
Dr. Itakura Toshifumi*
Dr. Tao Hong*
Dr. Michael Wong Jack*
Ultrafast Optical Physics Research Group:
Dr. Hidetoshi Nakano (Group Leader)
Dr. Tadashi Nishikawa
Dr. Ryuzi Yano
Dr. Atsushi Ishizawa
Dr. Tsuneyuki Ozaki*-4-

Dr. Koji Muraki
Dr. Akihito Taguchi
Dr. Norio Kumada
Dr. Kei Takashina

Dr. Toshio Nishida*
Dr. Kazuhide Kumakura

Dr. Makoto Yamashita
Toshimori Honjo
Dr. Akira Kawaguchi

Katsuya Oguri

Optical Device Physics Research Group:
Dr. Tadashi Saitoh (Group Leader)
Dr. Tetsuomi Sogawa
Hidehiko Kamada
Dr. Takehiko Tawara
Dr. Takeshi Kutsuwa

Dr. Hideki Gotoh
Dr. Stephen Hughes

Photonic Nano-Structure Research Group:
Dr. Yoshiro Hirayama (Group Leader)
Dr. Masaya Notomi
Dr. Atsushi Yokoo
Dr. Hideaki Taniyama
Dr. Kouta Tateno
Dr. Satoshi Mitsugi
Dr. Han-Youl Ryu*

Eiichi Kuramochi
Dr. Akihiko Shinya
Dr. Tetsu Ito-5-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 molecularbeam 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) since 2001. He is a member of the Japan society of Applied Physics and the
Physical Society of Japan.

Toshimasa Fujisawa was born in Tokyo on May 23, 1963. He received the B.E., M.S. and
Ph.D. degrees in electrical engineering from Tokyo Institute of Technology in 1986, 1988 and1991, respectively. He joined NTT Basic Research Laboratories in 1991. He was a guest
scientist in Delft University of Technology, Delft, the Netherlands during 1997-1998. Since
2003, he is also a guest associate professor at Tokyo Institute of Technology. Since 1991 hehas engaged in the study of semiconductor fine structures fabricated by focused-ion-beamtechnique and electron-beam lithography technique, transport characteristics ofsemiconductor quantum dot. His current interests are single-electron dynamics in quantum
dots, and their application to quantum information technologies. He is a member of the Japan
Society of Applied Physics, and the Physical Society of Japan.
-6-

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 Nippon Telegraph and Telephone
Corporation, NTT Optoelectronics Laboratories, Atsugi, Japan. Since then, his researchinterest has been to control the optical properties of materials and devices by using artificial
nanostructures, and engaged in research on semiconductor quantum wires/dots and photonic
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 a guest associate professor of Tokyo Institute of Technology (2003- ). He is a member of
the Japan Society of Applied Physics, and the American Physical Society.

Toshiki Makimoto was born in Tokyo on January 16, 1960. He received the B.E., M.S. and
Ph.D. degrees in electrical engineering from the University of Tokyo in 1983, 1985 and 1993,
respectively. He joined NTT Basic Research Laboratories in 1985. He was a visiting
researcher in University of California, Santa Barbara, USA during 1993-1994. Since 1985, he
has engaged in epitaxial growth of III-V compound semiconductors using metalorganic vapor
phase epitaxy (MOVPE) and flow-rate modulation epitaxy (FME), in-situ monitoring of
epitaxial growth using surface photo-absorption (SPA), heterojunction bipolar transistors(HBTs), and so on. His current interests are epitaxial growth of nitride semiconductors andnitride semiconductor devices. He is an associate editor of Japan Society Applied Physics and
JSAPI, and a member of the Japan Society of Applied Physics, the Institute of Electronics,
Information and Communication Engineers, and Materials Research Society.

-7-Invited / Guest Scientists(2003 Fiscal Year)

Name

Affiliation
PeriodDr. Takaaki Koga

Japan Science and Technology Agency (JST), Japan
December 2001 – March 2004

Prof. Thierry Martin

Université de la Méditerranée, France
April – May 2003

Dr. Michael Thorwart

Delft University of Technology, The Netherlands
June – July 2003

Prof. Emilio Mendez

State University of New York at Stony Brook, U.S.A.
June – August 2003

Dr. Vesselin Tonchev

Institute of Physical Chemistry, Bulgarian Academy of
Sciences, Bulgaria
July – September 2003

Prof. Rosario Fazio

Scuola Normale Superiore, Italy
October – November 2003

Dr. Hiroshi Yaguchi

Kyoto University, Japan
December 2003 – November 2004

Dr. Tobias Nyberg

University of Tokyo, Japan
January – December 2004

Dr. Jan Johansson

Japan Science and Technology Agency (JST), Japan
February 2004 – January 2005

Prof. Wu Peiheng

University of Nanjing, China
February – March 2004

Prof. Tord Claeson

Chalmers University of Technology, Sweden
February – April 2004

Dr. Giuseppe Falci

Università di Catania, Italy
February – March 2004
-8-

Prof. David Haviland

KTH – The Royal Institute of Technology, Sweden
February – March 2004

Prof. Frank Hekking

Joseph Fourier University, France
February – March 2004-9-

Advisory Board(2003 Fiscal Year)

Name

Title
Affiliation

Dr. Johan E. Mooij

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

Dr. C. Tord Claeson

Professor
Physics Department
Chalmers University of Technology, Sweden

Dr. Klaus von Klitzing

Professor
Max-Planck-Institut für Festkörperforschung
Germany

Dr. Klaus H. Ploog

Director
Paul-Drude-Institut für Festkörperelektronik
Germany

Dr. Michel H. Devoret

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

Dr. Christos Flytzanis

Professor
Physics of Condensed Matter Laboratory
Ecole Normale Supérieure, France

Dr. Chung L. Tang

Professor
School of Electrical Engineering
Cornell University, U.S.A-10-

Trainees(2003 Fiscal Year)

Name

Affiliation (Period)

Frank Deppe

Technische Universität München, Germany(May 2002 – May 2005)

Oliver Regenfelder

Technische Universität Graz, Austria(Sep. 2002 – Aug. 2003)

Yoshiharu Krockenberger

Technische Universität München, Germany(Nov. 2002 – Jun. 2003)

Marcus Steiner

Universität Hamburg, Germany(Jan. 2003 – Jun. 2003)

Sung Woo Jung

Pohang University of Science and Technology, Korea(Jan. 2003 – Jan. 2004)

Sandrine Buhours

INSA (Institut National des Sciences Appliquées), France(Feb. 2003 – Jun. 2003)

Antonio Ballestrazzi

Università degli Studi di Modena e Reggio Emilia, Italy(Mar. 2003 – May 2003)

Nicolas Gaillard

Ecole Nationale Supérieure de Physique de Grenoble, France(Mar. 2003 – Jul. 2003)

Sang-jin Kim

Chungbuk National University, Korea(Mar. 2003 – Mar. 2004)

Sreejeesh S. G.

L.B.S. College of Engineering, India(May 2003 – Oct. 2003)

Jennifer Chan

University of British Columbia, Canada(Jun. 2003 – Dec. 2003)

Jeff Liu

Simon Fraser University, Canada(Jun. 2003 – Apr. 2004)-11-

Joyce Yat-Ling Wong

University of Toronto, Canada(Jul. 2003 – Jun. 2004)

Gael Robert

ESPCI (École Supérieure de Physique et de Chimie
Industrielles), France(Jul. 2003 – Dec. 2003)

Elise Laffosse

INSA (Institut National des Sciences Appliquées), France(Jul. 2003 – Sep. 2003)

Niti Goel

University of Oklahoma, U.S.A.
(Jul. 2003 – Aug. 2003)

Guk-Hyun Kim

KAIST (Korea Advanced Institute of Science andTechnology), Korea(Aug. 2003 – May 2004)

Nicolas Thillosen

Aachen University of Technology (RWTH) / ResearchCenter Jülich, Germany(Nov. 2003 – Apr. 2004)

Christopher Schierholz

Universität Hamburg, Germany(Jan. 2004 – Jul. 2004)

Julien Duvernay

INSA (Institut National des Sciences Appliquées), France(Feb. 2004 – Sep. 2004)-12-

Japanese Students(2003 Fiscal Year)

Name

Affiliation (Period)

Mami Asaka

Tokai University, Japan (Jun. 2003 – Mar. 2004)

Shinich Amaha

University of Tokyo, Japan (Apr. 2003 – Mar. 2004)

Tomohiro Amemiya

University of Tokyo, Japan (Jul. 2003 – Aug. 2003)

Yuichi Igarashi

University of Tokyo, Japan (Apr. 2003 – Mar. 2004)

Taishi Ishihara

The University of Electro-Communications, Japan(Apr. 2003 – Mar. 2004)

Yasuaki Iwai

University of Tokyo, Japan (Apr. 2003 – Mar. 2004)

Yasuhiro Uchiyama

Meiji University, Japan (Apr. 2003 – Mar. 2004)

Miyuki Oshita

Toyohashi University of Technology, Japan(Jan. 2004 – Feb. 2004)

Keji Ohno

University of Tokyo, Japan (Apr. 2003 – Mar. 2004)

Yasuaki Okano

Tokyo Institute of Technology, Japan(Feb. 2004 – Mar. 2004)

Hajime Okamoto

Waseda University, Japan (Apr. 2003 – Mar. 2004)

Masahiro Kashiwa

Shonan Institute of Technology, Japan(Apr. 2003 – Mar. 2004)

Akira Kawaguchi

Osaka University, Japan (Apr. 2003 – May 2003)

Yoshiyuki Kawata

Tokyo Institute of Technology, Japan (Jul. 2003 – Aug. 2003)

Koya Kitagawa

Tokyo University of Science, Japan (Nov. 2003 – Mar. 2004)

Takatoshi Kido

Shonan Institute of Technology, Japan(Apr. 2003 – Mar. 2004)

Go KiraUniversity of Tokyo, Japan (Jun. 2003 – Mar. 2004)

Tatsuya Kutsuzawa

Tokyo University of Science, Japan (Apr. 2003 – Mar. 2004)

Tetsuo Kodera

University of Tokyo, Japan (Apr. 2003 – Mar. 2004)-13-

Naofumi Kobayashi

Meiji University, Japan (Apr. 2003 – Mar. 2004)

Shingo Kondo

Tokai University, Japan (Apr. 2003 – Mar. 2004)

Seiji Saito

Shonan Institute of Technology, Japan(Jul. 2003 – Mar. 2004)

Daisuke Sato

University of Tsukuba, Japan (Apr. 2003 – Mar. 2004)

Masafumi Shimizu

University of Tokyo, Japan (Apr. 2003 – Mar. 2004)

Yoshihiro Sugio

University of Tokyo, Japan (Apr. 2003 – Mar. 2004)

Daisuke Takagi

Meiji University, Japan (Apr. 2003 – Mar. 2004)

Akio Takahashi

University of Tokyo, Japan (Apr. 2003 – Mar. 2004)

Yoshiyuki Takahashi

Hokkaido University, Japan (Jul. 2003 – Aug. 2003)

Izumi Takesue

Aoyama Gakuin University, Japan (Apr. 2003 – Dec. 2003)

Kazunori Tawaraya

Hokkaido University, Japan (Mar. 2004)

Yoshifumi Nishi

University of Tokyo, Japan (Apr. 2003 – Mar. 2004)

Jiro Nishinaga

Waseda University, Japan (Apr. 2003 – Mar. 2004)

Aihiko Numata

University of Tokyo, Japan (Apr. 2003 – Mar. 2004)

Masumi Noda

Tokyo University of Science, Japan (Nov. 2003 – Mar. 2004)

Shigeto Fukatsu

Keio University, Japan (Apr. 2003 – Mar. 2004)

Shinya Fukuba

Meiji University, Japan (Apr. 2003 – Mar. 2004)

Seiji Fujikawa

Himeji Institute of Technology, Japan(Jul. 2003 – Aug. 2003)

Naoki Funagayama

Toyohashi University of Technology, Japan(Jan. 2004 – Feb. 2004)

Yusuke Furukawa

University of Tokyo, Japan (Feb. 2004 – Mar. 2004)

Munekazu Horikoshi

The University of Electro-Communications, Japan(Jun. 2003 – Mar. 2004)

Motonari Honda

University of Tokyo, Japan (Apr. 2003 – Mar. 2004)

Tetsunori Matsumoto

Tokyo University of Science, Japan (Apr. 2003 – Mar. 2004)

Jun Mizubayashi

Aoyama Gakuin University, Japan (Sep. 2003 – Dec. 2003)-14-

Shinichiro Miyadai

Aoyama Gakuin University, Japan (May 2003 – Dec. 2003)

Takuya Mouri

Tokyo University of Science, Japan (Apr. 2003 – Mar. 2004)

Ryusuke Morita

The University of Electro-Communications, Japan(Apr. 2003 – Mar. 2004)

Shin Yabuuchi

Keio University, Japan (Oct. 2003 – Mar. 2004)

Shimpei Yamaguchi

University of Tokyo, Japan (Apr. 2003 – Mar.2004)

Akira Yamazaki

Meiji University, Japan (Apr. 2003 – Mar. 2004)

Michihisa Yamamoto

University of Tokyo, Japan (Apr. 2003 – Mar. 2004)

Tomoo Yokoyama

Yokohama National University, Japan(Apr. 2003 – Mar. 2004)

Hiroyasu Yokoyama

University of Tokyo, Japan (Apr. 2003 – Mar. 2004)-15-

Ⅰ．Research Topics

Research Activities in NTT Basic Research Laboratories Vol. 14 (June, 2004)

Overview of Device Physics Research
Yasuo Takahashi
Device Physics Laboratory
Nanotechnology will be a key role in achieving the future multimedia society. Although
recent progress in information technology has been supported by the progress in Si LSI
technologies, energy dissipation in small Si chips has become a critical issue because of theincreasing number of transistors. For personal information tools, it is important to develop
new compact hardware that operates on new principles and consumes extremely low power.
The Device Physics Laboratory conducts research on single electronics, which enable us tomake small and ultimately low-power devices. For nanostructure fabrication, we are working
to refine lithographic techniques (top-down approach), and investigating self-assembly basedon the atomic structures of the substrate (bottom-up approach). We are also examining othermethods to create various nanostructures, such as carbon nanotubes.
The Si Nanodevice Research Group is investigating the operation mechanism of Si singleelectron transistors (SETs) and their circuit applications and seeking to establish fabrication
principles. SETs have special features that conventional transistors do not have. One is thecapability of attaching many input gates to them, and another is their applicability tomultiple-valued operation. By using these features, we have demonstrated effective arithmetic
circuits operating based on multiple-valued logic and showed their rather high-speed and lowpower consumption nature. We have also demonstrated multiple valued memory by using
one-by-one electron transfer and a highly sensitive single-electron detection device. A key
issue in making Si SETs is the oxidation reaction. To clarify their fundamental mechanisms
we have conducted experimental and theoretical investigation considering atomic levelprocesses, and performed simulations of the oxidation rate based on the newly proposedmechanisms.
The Nanostructure Technology Research Group is investigating top-down nanofabrication
techniques based on electron-beam lithography. One of the important issues fornanofabrication is pattern fluctuation. We have clarified the basis of ultrafine-patternformation by using new resist materials and have established a new supercritical-fluid drying
process to make high-aspect-ratio patterns. This led to the demonstration of high-temperature
operating SETs. Recently, we have expanded these two-dimensional nanofabrication
technologies to three-dimensional ones by using a specially designed sample-rotation systeminserted into an electron-beam lithography apparatus. As a demonstration of this newtechnology, we have created a nano-globe by a world map on a 60-µm sphere with 10-nm
resolution. We have also succeeded in making four-point-probe nano-system for conductancemeasurement of small structures by using focused-ion-beam technology.
The Surface Science Research Group is investigating wafer-scale control of ordered
nanostructure formation based on the bottom-up approach. We have conducted experimental
and theoretical studies of the flow of surface atomic steps on the Si surface to control the selfassembled nanostructures. We have also developed the method for the real time observationof the atomic reformation on the surface by using low energy electron microscopy (LEEM).
Our research on carbon nanotubes has led to a new low temperature growth technique. We
have succeeded in controlling the diameter of the grown nanotubes and established themethod to evaluate the electrical states and structures of nanotubes by using Raman
spectroscopy, photoluminescence, and photoelectron spectroscopy. We have also succeeded
the vertically aligned InP nanowire growth by using the vapor-liquid-solid mechanism withgold nanoparticles as a catalyst.
The details of some of our achievements are shown in the following four pages.
-17-Research Activities in NTT Basic Research Laboratories Vol. 14 (June, 2004)

Effect of the Si/ SiO2 Interface on Si diffusion in SiO2
Masashi Uematsu, Hiroyuki Kageshima, and Yasuo Takahashi
Device Physics Laboratory
With the scaling-down of Si devices, the bulk materials of interest are closer to materialinterfaces. Therefore, even phenomena in bulk materials, such as diffusion, are more likely
to be affected by interfaces, such as the Si/SiO2 interface. In this report, we investigated theeffect of the interface on Si self-diffusion in SiO2 by using isotopically enriched Si.
An isotopically enriched 28Si single crystal epi-layer was thermally oxidized to form
28
SiO2 of thicknesses of 200, 300, and 650 nm. The samples were implanted with 30Si anddiffusion-annealed at temperatures between 1150 and 1250 ºC. Si self-diffusion in SiO2 wasinvestigated using the implanted 30Si as makers. As shown in Fig. 1, we found that the Si
self-diffusivity increases with decreasing 28SiO2 thickness, i.e., the distance between the
diffusing 30Si species and 28Si/28SiO2 interface [1]. In order to explain this thickness
dependence, we constructed a model in which SiO molecules generated at the interface via Si+ SiO2 → 2SiO and diffusing into SiO2 enhance Si self-diffusion in SiO2 [2]. The
thickness dependence arises because the SiO diffusion is so slow that the 28SiO concentration
at the 30Si region critically depends on the distance from the interface, where the SiO isgenerated, as shown in Fig. 2. We propose a mechanism of Si self-diffusion in SiO2
enhanced by the existence of SiO via the reaction such that 30Si(s) + 28SiO(i) ⇔ 28Si(s) +30
SiO(i), where substituted (s) Si atoms diffuse via the kick-out reaction with diffusing
interstitial (i) SiO molecules. Based on this mechanism, we simulated and fitted the
diffusion profiles of 30Si (simulation in Fig. 1).
Furthermore, the simulation predicts that the self-diffusivity would increase for a longer
annealing time because more SiO molecules should be arriving from the interface. As
predicted, the time-dependent diffusivity was experimentally observed, and this confirms our
diffusion model. The diffusion length of SiO estimated from the present results is 0.4 nm
for 10-second annealing at 1100 ˚C. The present study suggests that the effect of the
Si/SiO2 interface may arise during silicon processes when the material thickness is down to 1nm.
[1] S. Fukatsu et al., Appl. Phys. Lett. 83 (2003) 3897.
[2] M. Uematsu et al., Appl. Phys. Lett. 84 (2004) 876.

10

30

30

10

20

10

19

28

Si

30

300 nm

200 nm28

650 nm

18

0

50

SiO2

24 h

SIMS ( Si)As-impla

10

28

Si

Si - Simulation
1250 ℃

30

Si concentration (cm-3)

interfacesurface

21

100

150

200

Depth (nm)Fig. 1. Dependence of 28SiO2 thickness
on 30Si diffusion in 28SiO2.

Si/SiO2
interface

SiO

28

Fig. 2. Model.
-18-

Si

Research Activities in NTT Basic Research Laboratories Vol. 14 (June, 2004)

World’s Smallest Globe (Nano-Globe) made using electron beam
Kenji Yamazaki and Hideo Namatsu
Device Physics Laboratory
We have devised a new electron-beam (EB) lithography system for three-dimensional
nanofabrication (3D-NANO) with a 10-nm resolution. As a demonstration of 3D
nanopatterning using this system, we made the world’s smallest globe (nano-globe) by
writing the world map on a sphere sample. This technology promises to become a newimportant basis of many fields of nanotechnology.
Electron beam lithography has been used for two-dimensional patterning in LSI
manufacturing, and now has a resolution on the order of 5 nm. On the other hand, theresolution or fabrication speed of conventional 3D fabrication methods is too low or too slow
for 3D nanotechnology. That is, methods using an optical or X-ray beam have micron-orderresolutions, and deposition using an ion beam cannot accomplish fabrication at a reasonable
speed. Our 3D-NANO technique using EB lithography solves these problems.
Our technique features a two-axis-of-rotation drive that works in the EB lithography
apparatus. With this drive any surface of a 3D sample can be exposed to an EB [1]. Since an
EB has a much larger depth of focus as well as a higher resolution than an optical or X-ray
beam, an EB is convenient for writing three-dimensionally on a sample. 3D-NANO wasachieved by the additional development of 3D positioning techniques for written patterns [2].
On the nano-globe, which is made of polymethylmethacrylate, the minimum size of thepatterns is 10 nm. This is several ten times as small as than that for conventional methods
using an optical or X-ray beam. The exposure time for the whole world map was only about 2
min. This means that the technique can be applied to fast fabrication with large-scalecomplicated structures. Our 3D-NANO will enable us to make novel nanodevices and will
open up new fields in nanotechnology.
[1] K. Yamazaki and H. Namatsu, Microelectron. Eng., in printing.
[2] K. Yamazaki and H. Namatsu, Proc. IEEE MEMS 2004, 609.

60 µm

PMMA
spheree-beam

R-axis10 nm

SampleT-axis

100 nmElectron microscope images of the nano-globe.
Unlabeled scale bars indicate 3 µm.

-19-

Illustration showing how
a sample rotates.

Research Activities in NTT Basic Research Laboratories Vol. 14 (June, 2004)

Nano-four-point-probe systems
Masao Nagase
Device Physics Laboratory
We have developed nanotools for measuring the electrical properties of nanomaterials.
The conventional probe used in scanning probe microscopy (SPM) has only one tip on the
single cantilever. If we can integrate a functional device on a SPM cantilever, it will be a
powerful and useful nanoelectromechanical system or nanotool for evaluating the propertiesof nanomaterials. However, it is very difficult to integrate the fabrication process of thefunctional device and that of the SPM cantilever. The recent advancement in ion optics offocused ion beam (FIB) technology has enabled us to fabricate micro- and nano-order
structures. Measurement systems are integrated on a Si cantilever of SPM using newly
developed fabrication methods based on nanopatterning technology. In this section, we
introduce two kinds of nano-probe systems.
Measurement of electrical resistivity using a four-point-probe is a fundamental technologyof electronic devices. However, the distance between the probes of an existing four-pointprobe is a few micrometers. It is too large for evaluation of nano-order electrical properties ofnanomaterials, such as CNT and DNA. We try to fabricate nano-four point probes for SPM
using FIB technology. Fig. 1 shows a micrograph of the nano-four-point probes fabricated by
FIB milling [1]. The thin Pt film deposited on the tip of the lever is divided into 4 parts using
ion beam milling. The pitch of the probes is about 500 nm. The width is about 200 nm. To
miniaturize the probes, nano-four-point probes are fabricated by electron beamnanolithography. Fig. 2(a) shows Si nanoprobes with 60-nm-pitch and 20-nm-width on asilicon-on-insulator substrate. This nanodevice is cut out from the substrate by FIB millingand is transferred to the tip of a Si cantilever with four Al electrodes. W interconnections
deposited by FIB deposition (FIB-W) are formed between the Si electrodes and the Al
electrodes. As a result, a nanodevice system is realized on an SPM microcantilever as shownin Fig. 2(b) [2]. FIB technology brings us a new solution for assembling nanodevices. The
abilities of FIB, milling and handling of micro-scale structures and direct wiring of metalelectrodes are very useful for nano- and micro-electromechanical systems.
With further miniaturization of the nanoprobe, the SPM cantilever system fabricated by
FIB technology will become a useful evaluation tool for nanodevices and molecular science.
[1] M. Nagase et. al., Jpn. J. Appl. Phys. 42 (2003) 4856.
[2] M. Nagase and H. Namatsu, Jpn. J. Appl. Phys. 43 (2004), to be published.

Fig. 1. Nano-four-point-probe fabricatedby FIB milling.

Fig. 2. Nano-four-point-probe assembled
by FIB technology.
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Research Activities in NTT Basic Research Laboratories Vol. 14 (June, 2004)

Semiconductor Nanowires
Yoshio Watanabe, Satyaban Bhunia, and Tomoaki Kawamura
Device Physics Laboratory
One-dimensional nanomaterials are expected to play a key role in fabricating nanoscale
devices of the next generation. However, miniaturization in electronic and optoelectronic
devices through improvements in conventional “top-down” technologies is approaching thelimits of lithographic and etching processes. In contrast, bottom-up approaches tonanodevices, where the nanomaterials are assembled from basic building blocks, such as
semiconductor nanowires and carbon nanotubes, have the potential to go far beyond theirlimits. Recently, we have successfully grown the surface mounted and vertically aligned InP
nanowires by metal organic vapor phase epitaxy [1]. The nanowires were grown by thevapor-liquid-solid mechanism with Au nanoparticles acting as the catalyst. The Au
nanoparticles were used as the seed to control the nanowire diameter in the nanoscale range.
Figure 1 shows a typical scanning electron microscopic (SEM) picture of the nanowires
grown on InP(111)B taken at an oblique angle of 40o. Both scanning and transmission
electron microscopic studies showed highly dense nanowires with homogeneous diameter
along their length axis, and had zinc-blende structure with <111> growth direction, and mostof them had diameter in the range of 20 – 25 nm. Photoluminescence measurements at room
temperature showed significant blueshift in the peak position compared to bulk InP due to thequantum confinement of the carriers in the nanowires. Furthermore, heteroepitaxial InP
nanowires were also successfully grown on GaP(111)B substrates [2]. Figure 2 shows atypical SEM picture of the nanowires grown on GaP(111)B. Highly dense, vertically aligned
nanowires with uniform diameters along the vertical axis are visible. Very recently, the sitecontrolled InP nanowires were successfully grown at the positions where Au nanoparticles
have been arranged through liquid Au migration and followed Au nanoparticle formation at aparticular position on the patterned Si substarte [3].
[1] S. Bhunia, T. Kawamura, Y. Watanabe, S. Fujikawa, and K. Tokushima, Appl. Phys. Lett.
83 (2003) 3371.
[2] Y. Watanabe, et al., Proceedings of the Twelfth International Workshop on the Physics of
Semiconductor Devices (IWPSD-2003), Chennai India, December 2003.
[3] Y. Watanabe, et al., Proceedings of Fifth International Workshop on Epitaxial
Semiconductors on Patterned Substrates and Novel Index Surfaces (ESPS-NIS), Stuttgart
Germany, October 2003.

Fig. 1. SEM image of the InP
nanowires grown on InP(111)B.
-21-

Fig. 2. SEM image of the InP nanowires
grown on GaP(111)B.

Research Activities in NTT Basic Research Laboratories Vol. 14 (June, 2004)

Overview of Material Science Research
Masao Morita
Materials Science Laboratory
The Materials Science Laboratory (MSL) aims at producing new materials by controllingarrangement of atoms and bonding of molecular for new functions using quantum phenomena
and so on. To accomplish these goals from different perspectives the following four MSL
groups are formed and are studying many kinds of materials ranging from inorganic matter,such as semiconductors, to organic matter, such as neurotransmitters. The characteristicfeature of MSL is the effective 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.
Molecular and Bio-Science Research Group
Create new organic materials by manipulating single molecules, and investigate information
processing devices based on neural functions.
Superconducting Thin Films Research Group
Study high-Tc superconductors by fabricating top quality samples through the molecularbeam epitaxy(MBE) method and develop its applications to microwave communication.
Superconducting Quantum Physics Research Group
Investigate theoretical and experimental research on a quantum computers superconductors
and new magnetic devices using quantum dot arrays.
Spintronics Research Group
Aim to control the spin degrees of freedom in semiconductors to achieve new device
functions for the next generation electronics.
The following are four major results obtained in the fiscal year 2003.
1. The carrier transport and injection properties of conductive organic polymer withdifferent dimensions and configurations were studied, and it was found that the carrier
injection is dominated by the tunneling process at the nano-gap electrode.
2. Non-doped superconductors in lanthanum based copper oxide were discovered, though it
has been believed that the non-doped parent materials of high-Tc superconductors are
Mott insulators.
3. Multiphoton transitions between the superposition states in the superconducting flux qubit
were observed. The microwave power dependences of the half width at half maxima of
the resonant dips were well reproduced by Bloch equations based on a dressed-atom
description. From this analysis, the qubit coherence time is estimated to be 5 ns.
4. The magnetization processes of micro-structured ferromagnetic rings were investigatedusing the local Hall effect device and it was found that the magnetic transition strongly
depends on the inner diameter of the ring.

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Research Activities in NTT Basic Research Laboratories Vol. 14 (June, 2004)

Carrier Injection and Transport of Conductive Polymer-Based Devices
Kazuaki Furukawa, Wenping Hu, Hiroshi Nakashima, Yoshiaki Kashimura, Katsuhiro Ajito,
and Keiichi Torimitsu
Materials Science Laboratory
Organic molecules attract much interest recently as electronic materials. Research anddevelopment for flexible display and thin-film-transistor applications are vital today. In
addition, molecular scale device, the device comprising single or small number of molecules,
is considered for future organic electronic devices, not only because it has advantage in size
but also it is expected to show novel phenomenon originated from single molecule. In thisstudy, we prepared and observed carrier transport properties of organic electronic devices
with different electrode sizes and configurations [1].
Figure 1 shows device structures. Nanogap electrodes (gap ~100 nm) and conventional
sandwich type thin film device (with 2mm × 2mm area) were fabricated. The material ispoly(p-phenyleneethynylene) derivative (TA-PPE, Fig.1) [2], which is know as a rigid πconjugated polymer.
The remarkable difference between two types of devices was observed for the temperaturedependence of current density-voltage (J-V) curves. Although the well known Arrhenius
type temperature dependence was observed for the sandwich device, temperature dependence
was not clearly observed for the nanogap device. Moreover, after the treatment of the
nanogap device exposed in THF vapor, which is a good solvent for TA-PPE, the temperaturedependence almost disappeared (Fig. 2). This result suggests that the carrier injection andtransport is dominated by the tunneling process. During the exposure of the nanogap device
in the vapor of its good solvent, TA-PPE became somewhat fluid, and thus the nanostructureof TA-PPE changed. The increase of the number of bonds between TA-PPE ends and Au
electrodes at the interface made the tunneling process through Au-S bond superior.
The present results indicated that the molecular conformations as well as configurations
contribute to the characteristics of molecular scale devices. The device design involving thecontrol of molecular conformations is currently under consideration.
[1] W. P. Hu, et al., Phy. Rev. B (accepted).
[2] H. Nakashima, et al., Polym. Prepr. 44(1) (2003) 482.
TA-PPE
H3C

OC 6H13SSn

C6H13OAu
Au
Au

100 nm-9
CH 3

TA-PPE

5.0 V
4.0 V

100 nmSandwichdevice

-12

3.0 V
2.0 V

-15
1.0 V

TA-PPESiO2

SiO

ln (J, A/m)

O

-18
0.0033

Nanogap
device0.00360.0039

1/T (1/K)

Au

Fig. 1. Molecular structure of TA-PPE andsandwich and nanogap device structures.
-23-

Fig. 2. ln(J) plotted vs. 1/T at different
applied voltage for TA-PPE nanogap
device after exposed in THF vapor.

Research Activities in NTT Basic Research Laboratories Vol. 14 (June, 2004)

Discovery of non-doped superconductors
in lanthanum based copper oxide
Akio Tsukada, Hideki Yamamoto, and Michio Naito*
Materials Science Laboratory*Tokyo University of Agriculture and Technology
It has been believed that the non-doped parent materials of high-Tc superconductors are
Mott insulators, and superconductivity emerges only after n-type or p-type doping. Against
this belief, we found that superconductivity is achieved in non-doped La2CuO4 with Nd2CuO4(T’) structure by substitution of La3+ by “isovalent” rare earth ions (RE3+) having a small
ionic radius. This substitution is intended mainly to stabilized the T’ phase of La2CuO4
instead of T (K2NiF4) phase [1], so it is presumed not to cause effective doping. Therefore,
our observation appears to contradict the general belief.
The new superconductors T’-La3+2-xRE3+xCuO4 (RE3+ = Sm3+, Eu3+, Gd3+, Tb3+, Lu3+, Y3+)
were prepared by molecular beam epitaxy (MBE) and showed superconducting transition at ~21 K [2]. Figure 1 shows the temperature (T) dependence of resistivity (ρ) for the films of
La2-xYxCuO4 with various x. Superconductivity appears at x = 0.09 and 0.15 with Tc ~ 20 K.
Superconductivity was also observed in other RE substitution except for Pr and Nd
substitution. Figure 2 summarizes the RE concentration dependence of T c inT’-La2-xRExCuO4. Regarding the origin of superconducting carriers in T’-La2-xRExCuO4,
one can think of two possible scenarios. One is that the oxygen deficiencies are a source ofeffective electron carriers. The other is that the T’-La2CuO4 is not a Mott insulator, and has
intrinsic carriers, as predicted by the band calculation for Nd2CuO4. If the latter scenario iswell-established, it will urge a reexamination of the early controversy on the “doped Mottinsulator scenario”, which is now widely accepted as a starting viewpoint for high-Tc
superconductivity.
[1] A. Tsukada, et al., Phys. Rev. B 66 (2002) 184545.
[2] A. Tsukada, et al., Physica C, in press.

Fig. 1. ρ-T curves for La2-xYxCuO4.

Fig. 2. Tc for La2-xRExCuO4.

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Research Activities in NTT Basic Research Laboratories Vol. 14 (June, 2004)

Multiphoton absorption observed in a superconducting flux qubit
Shiro Saito, Michael Thorwart1, Hirotaka Tanaka, Hayato Nakano, Kouichi Semba,
Masahito Ueda2, and Hideaki Takayanagi
Materials Science Laboratory, Heinrich-Heine-Universität Düsseldorf1,
NTT Research Professor and Tokyo Institute of Technology2

Fig. 1.
Superconducting
flux qubit (innerloop) and dc-SQUID
for readout (outerloop)
1 photon
2
3

300

10
5
0
-5
-10
-15

|↓>

2

200
100
0

(a)

15

dIsw [nA]

HWHMn [MHz]400

Energy level [GHz]Of the recently realized solid-state quantum bits (qubits), the superconducting flux qubit
has advantages because its scalability and long coherence time. The qubit consists of asuperconducting loop with three Josephson junctions (see Fig. 1). The two states of the qubit
correspond to clockwise |0〉 and counterclockwise |1〉 superconducting current in the loop.
The current involves millions of Cooper pairs, which means that the two states aremacroscopically distinct. Hence, this system can realize a superposition between two such
macroscopic states. For the first time, we observed multiphoton transitions between the
superposition states in the superconducting flux qubit [1].
Figure 2(a) shows the magnetic flux dependence of the qubit energy levels, where Φ qubit
is the flux through the qubit loop and Φ 0 (= h 2e ) is the flux quantum. The arrows in the
figure represent a microwave with an energy of 9.1 GHz. The qubit can be excited from theground state to the first excited state by absorbing multiple photons. We remark that theexistence of the energy gap at the degeneracy point Φ qubit Φ 0 =1.5 is strong evidence forthe superposition between the macroscopically distinct states.
The qubit was read out by measuring the switching current of a superconducting quantum
interference device (dc-SQUID) (see Fig. 1). Figure 2(b) shows the change dI sw in theswitching current as a function of the magnetic flux under the microwave irradiation. The dcSQUID detected the change in the qubit state from |0〉 to |1〉 induced by magnetic flux.
Furthermore, resonant peaks and dips were observed at the expected operating points in Fig.
2(a). The microwave power dependences of the half width at half maxima of the resonant
dips were well reproduced by Bloch equations based on a dressed-atom description (see Fig.
3). From this analysis, we found the qubit coherence time to be 5 ns, which is consistent withthat obtained from another experiment using a microwave pulse.
[1] S. Saito, et al., cond-mat/0403425.

T = 30 mK

1
0

1
3

-1
-2

0

1

10

P/20

2

3

(arb. units)

4

(b)

2

1.490

2

|↑>
1

1.495

1.500

Φ qubit / Φ 0

1.505

1.510

Fig. 3. Microwave power dependence ofFig. 2. (a) Energy diagram of qubit.
HWHM of resonant dips. Solid curves(b) Magnetic field dependence ofrepresent theoretical simulations.
qubit readout.
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Research Activities in NTT Basic Research Laboratories Vol. 14 (June, 2004)

Control of magnetization states in micro-structured ferromagnetic rings
Marcus Steiner and Junsaku Nitta
Materials Science Laboratory
It is difficult to detect the magnetization of a single micro-magnet even by using a highsensitive susceptibility-meter; therefore, ensemble averaged magnetization processes ismeasured in an array including several thousand micro-structured magnets. We have shownthat a fringe-field-induced local Hall effect (LHE) device can detect the magnetization
process of a single micro-structured magnet [1]. It has been predicted that a flux closure state(vortex state) is stable in ferromagnetic small ring structures. In the vortex state, almost no
stray field is generated, that offers a potential application for high integration of themagnetoresistive random access memory (MRAM). We have investigated the magnetization
processes of micro-structured ferromagnetic rings using the LHE device and have found thatthe magnetic transition strongly depends on the inner diameter of the ring.
The inset of Fig. 1 shows an SEM image of a fabricated sample. A cross-shape is asemiconductor Hall device. A NiFe micro-structured ferromagnetic ring is placed near theHall cross to detect a fringe field. An external magnetic field is applied in parallel to thesemiconductor two-dimensional electron gas in order that it does not affect the Hall resistance.
Figure 1 shows hysteresis loops of the Hall resistance. The outer diameter of the rings is fixed
to 2.0 µm, and the inner diameter is varied from 0 (Disk) to 1.6 µm in steps of 0.4 µm. We
observed a systematic change in the hysteresis loops by increasing the inner diameter. For
narrow rings, sharp transitions from the so-called “onion” state to the “vortex” state wereobserved. In rings with smaller inner diameter, the transitions are broad and more complex[2]. A comparison between the hysteresis loop of the Hall resistance of a 0.4 µm-diameterring and numerical calculation is shown in Fig. 2. Starting from the onion state (i), the ring
reversibly enters a wave-like state (ii). The global vortex state (iii) is then irreversibly reached
and forms a stable configuration that produces a plateau in the hysteresis. Via an irreversible
transition into a single local vortex state (iv), the saturation configuration is reached again.
The measured Hall resistance loop is well reproduced by the numerical simulation.
These results indicate that the transition field to the vortex state can be controlled by the
inner diameter.
[1] J. Nitta, et al. Jpn. J. Appl. Phys. 41 (2002) 2479.
[2] M. Steiner and J. Nitta, Appl. Phys. Lett. 84 (2004) 939.

Fig. 1. Local Hall resistance measurements.

Fig. 2. Measured and simulated hysteresis loops.

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Research Activities in NTT Basic Research Laboratories Vol. 14 (June, 2004)

Overview of Quantum Physics and Electronics Research
Yoshiro Hirayama
Physical Science Laboratory
Our research in the fields of quantum physics and electronics, which is based on
semiconductor nano-structures fabricated by high-quality semiconductor crystal growth andadvanced device fabrication techniques, focuses on quantum coherent control, carrierinteractions and wide-bandgap semiconductor physics. Our aim is the development ofinnovative semiconductor devices. Quantum Solid State Physics Research Group and WideBandgap Semiconductor Research Group are working in the following areas.
Quantum Solid State Physics Research Group(1) Carrier interactions in semiconductor heterostructures (carrier interractions in bilayer
systems, interactions between nuclear-spin and conduction electrons).
(2) Quantum electronic state control in quantum dot systems (spin/charge control, carrier
dynamics of quantum nanostructures, fundamental properties of solid-state quantum
computers).
(3) Semiconductor nano-mechanical systems (fabrication and characterization).
(4) Direct nano-scale imaging of electronic states by low-temperature STM.
Wide-Bandgap Semiconductor Research Group(1) Optical device physics in ultra-violet LEDs and optical devices using micro-facets.
(2) Electronic device physics, such as carrier transport in nitride FETs and HBTs.
(3) Impurity doping into wide-bandgap semiconductors and its characterization.
(4) High-quality diamond epitaxial growth and its application to electronics devices.
(5) Developing new semiconductor materials such as InN.

Major results obtained this fiscal year 2003 are reported in the following pages.
We have successfully applied electrical pump and probe technique to control a single
electron motion in a coupled quantum dot coherently. We have demonstrated one qubit
operation, i.e. arbitrary rotation on the Bloch sphere, for the semiconductor charge qubit. Thisis the first step towards physical realization of electrically-controlled semiconductor quantum
computer.
In a high magnetic field, electron interactions in the two-dimensional electron gases resultin the fractional quantum Hall effects. In this regime, two different electron spin states
energetically degenerate in a certain condition. We have found that a novel interaction
between electron and nuclear spins occurs in such condition and this interaction is very
sensitive to the electron spin state. We have also shown a possibility to control nuclear spinpolarization in a mesoscopic scale.
By using high-quality diamond films grown by MOCVD, we have fabricated a diamondfield-effect transistor (FET) in collaboration with Ulm University. The fabricated FET
exhibited the highest cut-off frequencies among diamond FETs and showed the first
amplification in the millimeter-wave range (30～300 GHz).
We have also successfully fabricated an npn-type GaN/InGaN heterojunction bipolartransistor (HBT) using the base regrowth technique. The fabricated HBTs show high current
gains and super-high-power density of 230,000 W/cm2.

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Research Activities in NTT Basic Research Laboratories Vol. 14 (June, 2004)

Semiconductor Charge Qubit
Toshiaki Hayashi and Toshimasa Fujisawa
Physical Science Laboratory
The study of quantum computing has attracted great attention because it is more efficientat some specific calculations than classical computing. The elementary unit of quantum
computing (qubit) has two quantum states which are taken as a set of basis states (|0> and|1>). Unlike a classical bit, any state of a qubit which represents quantum information can be
described as a linear combination of the two basis states. Quantum information processing
devices are required to perform universal unitary gate operations within the decoherence timeof the qubits. Although much effort has been invested, the experimental realization ofquantum computing is still challenging.
We have studied a charge qubit in a semiconductor double quantum dot (QD) because allparameters we need for unitary gate operations can be controlled electrically [1]. The double
QD consists of two QDs coupled to each other via a tunnel barrier and electrons can flip backand forth between the two QDs. For simplicity, we consider that we have one electron in the
double QD. The two states of the charge qubit are the states in which the electron occupies
one of the two QDs.
We employed a lateral double QD fabricated from a GaAs / AlGaAs heterostructure, as
shown in Fig. 1. A voltage pulse is applied to the drain electrode to modify the electronic
state of the double QD abruptly. This non-adiabatic transition allows us to perform
initialization, coherent manipulation, and read-out operations of the qubit state. We have also
demonstrated rotation gate operation [1] and phase-shift gate operation [2] on the charge
qubit at 20 mK.
Figure 2 shows the normalized current through the device, which can roughly be taken as
the averaged number of electrons in the right QD at measurement operation. This shows an
oscillating behavior as a function of pulse length, which corresponds to rotation gate
operation. We also showed that it was possible to change the oscillation frequency, which isrelated to the coupling energy between the two QDs, by changing the gate voltages.
The present result is the first step towards physical realization of quantum computing.
[1] T. Hayashi et al., Phys. Rev. Lett. 91 (2003) 226804.
[2] T. Fujisawa et al., Physica E, in press.

Fig. 1. Schematic diagram ofdouble QD sample.

Fig. 2. Averaged number of electrons as a function ofpulse length.
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Research Activities in NTT Basic Research Laboratories Vol. 14 (June, 2004)

Microwave Performance of Diamond Field-Effect Transistor
Makoto Kasu
Physical Science Laboratory
At present the data transfer rate in communications is increasing very rapidly. Therefore,
electronic devices that can operate at higher frequencies with higher output power are eagerly
needed. Diamond has the highest thermal conductivity among materials and therefore offers
the highest heat dissipation efficiency during high-power operation. Diamond exhibits a very
high breakdown electric field, which means diamond devices can operate at extremely highvoltage. These properties are important for high-output-power devices. In addition, thecarriers in diamond have a high mobility and a high saturation drift velocity, which makehigh-frequency and high-speed operation possible. In fact, from device figures of meritcalculated from the physical properties of high-frequency high-power devices diamond is thebest among semiconductors and can therefore be called “ultimate semiconductor.” However,until now, the growth of high-quality diamond thin film had been impossible because of theformation of numerous crystalline defects and impurities during growth.
We have developed a CVD growth technology for high-quality diamond thin films with alow density of defects and impurities [1] and, using those thin films, have, in collaboration
with the University of Ulm, Germany, fabricated diamond field-effect transistors (FET) [2],as shown in Fig. 1. In the FET, a quasi two-dimensional hole channel formed as a result ofhydrogen surface termination, and we formed a 0.2 µm-long short gate contact using
electron-beam lithography and self-aligned technology. As shown in the frequency
dependence of power gains (Fig. 2), the FET exhibited the transition frequency (fT) for |h21|2
of 25 GHz, and the maximum oscillation frequency (fMAX) for the maximum available gain(MAG) and unilateral power gain (U) of 63 and 81 GHz, respectively. These values are thehighest ever for diamond, and show the first amplification in the millimeter-wave range.
The power characteristics of the diamond FET for A-class operation at 1 GHz showed alinear power gain of 14 dB for a wide input power range, and the maximum output power(PMAX) of 0.35 W/mm. The PMAX is the highest ever for diamond, and will be increased by
one order by optimizing the device structure. The microwave noise measurements of the FET
showed that the minimum noise figure (Fmin) was only 0.72 dB at 3 GHz. This Fmin is better
than that of Si MOSFET and comparable with those of p-GaAs HEMT and n-GaN HEMTwith the same gate length. This means that a diamond FET is very promising for microwave
receivers as well as transmitters.
[1] M. Kasu, M. Kubovic, et al., Diamond and Related Materials 13 (2004) 226.
[2] M. Kubovic, M. Kasu, et al., to be published in Diamond and Related Materials (2004).
40
LG=0.2 µm, WG= 200 µm

Power gain (dB)

35
30

U

25
20

MAG

15
10

Ih21I250-5fMAX(U) =81 GHzfT = 25 GHz
1

fＭＡＸ(MAG) = 63 GHz

10

100

Frequency (GHz)

Fig. 1. Overview of diamond FETs.

Fig. 2. Frequency dependence of power gains.
-29-Research Activities in NTT Basic Research Laboratories Vol. 14 (June, 2004)

Nitride Heterojunction Bipolar Transistors for High-Power Applications
Toshiki Makimoto, Yoshiharu Yamauchi and Kazuhide Kumakura
Physical Science Laboratory

10

-2

10

-4

10

-6

10

-8

10

M axim um Co llecto r
C urrent (A)Diode Current (A)Compared with Si and GaAs, nitride semiconductors have high breakdown voltage
because of their wide bandgap. On the other hand, one of the characteristics of aheterojunction bipolar transistor (HBT) is high current density. Therefore, a nitride HBT is apromising electronic device in terms of both materials and device types. However, there are
two issues for the nitride HBT. One is a relatively low current gain and the other is a highoffset voltage in the common-emitter current-voltage (I-V) characteristics. As a result, highpower characteristics of a nitride HBT have not been reported, though they are theoretically
expected.
We have developed a GaN/InGaN HBT. Our GaN/InGaN HBT uses a low-resistivity pInGaN layer as a base layer instead of the conventional p-GaN [1] and has a double
heterostructure for a high breakdown voltage [2]. To improve current gain and reduce theoffset voltage, we used a base regrowth technique. The current gain increased 100 fold andthe offset voltage was reduced to 1/10 compared with the previous record [3]. This time, wehave investigated the high-power characteristics of these GaN/InGaN HBTs.
The base-collector junction is reverse-biased and the HBT power increases withincreasing reverse voltage. Figure 1 shows typical I-V characteristics of a base-collector
diode. The leakage current is small even at the reverse bias voltage of –50 V because of thewide bandgap of the GaN collector. On the other hand, the output power depends on thecollector current in the common-emitter I-V characteristics. Figure 2 shows the maximum
collector current as a function of the emitter size. As shown in this figure, the maximum
collector current is proportional to the emitter size. Since the breakdown voltage isindependent of the emitter size, the output power is proportional to the emitter size. Up tonow, we have obtained a maximum output power exceeding 10 W for a 90 µm x 50 µm
emitter. The maximum power density is as high as 270,000 W/cm2 [4]. This is the first
demonstration of high-power characteristics in a nitride HBT.
[1] K. Kumakura et al., Jpn. J. Appl. Phys. 39 (2000) L337.
[2] T. Makimoto et al., Appl. Phys. Lett. 79 (2001) 380.
[3] T. Makimoto et al., Appl. Phys. Lett. 83 (2003) 1035.
[4] T. Makimoto et al., Appl. Phys. Lett. 84 (2004) 1964.

-10-50 -40 -30 -20 -10 0 10
Applied Voltage (V)Fig. 1. Typical I-V characteristics of abase-collector diode.

1

Slope = 1

0.1
-5

-4

10
10
Emitter Size (cm 2 )Fig. 2. Maximum collector current as afunction of the emitter size.
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Research Activities in NTT Basic Research Laboratories Vol. 14 (June, 2004)

Overview of Quantum Optics and Optical Materials Research
Yoshiro Hirayama
Physical Science Laboratory
In the fields of quantum optics and optical materials we pursue our studies for thedevelopment of core-technologies that will innovate optical communications and opticalsignal processing as well as for the scientific progress of the field. Optical State Control
Research Group, Ultrafast Optical Physics Research Group, Optical Device Physics ResearchGroup and Photonic Nanostructure Research Group are engaged in the subjects listed below.
Quantum State Control Research Group(1) Experimental and theoretical studies for quantum cryptography/computing/protocols.
(2) Quantum transport theory and electron/spin entanglement.
Ultrafast Optical Physics Research Group(1) High-irradiance, short-pulse soft X-ray generation from femtosecond laser-produced
plasma and its application to materials science.
(2) Ultrafast laser pulse induced terahertz radiation and its application.
Optical Device Physics Research Group(1) Coherent control of excitonic and spin states in quantum dots & wires.
(2) Optical properties in nitride-semiconductors and their device applications.
(3) Single/entangled photon emitters and detectors.
Photonic Nanostructure Research Group(1) Two-dimensional photonic crystal optical circuits (ultra-low loss waveguide, resonator,
filter)(2) Interaction between photonic nanostructures and materials (negative refraction,
extremely-large group velocity dispersion, photonic quasicrystal laser).
(3) Nanoprint lithography

Major results obtained this fiscal year 2003 are reported in the following pages.
We have demonstrated a long-distance quantum key distribution by using a single
photon emitter based on quantum dots. We have also proposed and demonstrated a novel
quantum cryptography scheme called differential-phase-shift quantum key distribution. This
scheme will provide stable and high-speed quantum cryptography.
Efficiency of water-widow x-ray pulse conversion from femtosecond laser plasma was
successfully improved by using a carbon nanotube target. The result indicates that carbon
nanotubes are attractive as fs-laser plasma target for realizing single-shot x-ray microscopy.
Sampling measurement of femtosecond soft x-ray pulse, which is based on optical-field
induced ionization dynamics, has been demonstrated.
We combined GaN quantum wells with oxide-based distributed Bragg reflectors byusing a wafer bonding technique. The VCSEL (vertical cavity surface emitting laser)
operation was successfully demonstrated for the fabricated structures. We also started a new
project for single and entangled photon emitters and detectors in collaboration with TAO(Telecommunications Advanced Organization of Japan).
We have demonstrated ultra-low-loss photonic bandgap waveguide and developed ultrasmall and high-Q filter based on SOI (silicon on insulator) photonic crystal systems. We havealso fabricated photonic quasicrysytal lasers with organic dye and confirmed clear lasing
action for the first time. Our experimental results indicate that lasing occurs by delocalized
coherent modes inside the quasicrystal.
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Research Activities in NTT Basic Research Laboratories Vol. 14 (June, 2004)

Differential-Phase-Shift Quantum Key Distribution
Kyo Inoue
Physical Science Laboratory
Quantum cryptography, which provides an unconditionally secured secret key based on
quantum mechanics, is extensively studied. Although several schemes have been proposed,
each has problems with respect to suitability for fiber transmission, or operation stability, ordata rate. This study proposes and demonstrates a novel quantum cryptography scheme,
called differential-phase-shift quantum key distribution, which can realize a stable high-speed
system.
Fig. 1 shows the configuration of the proposed system. The transmitter (called Alice)
randomly phase-modulates a coherent pulse train and sends out it with a power level of 0.1
photon/pulse. The receiver (called Bob) detects the pulses after a one-bit delayedinterferometer. In the detection, DET1 clicks for 0 phase difference between two sequential
pulses, and DET2 clicks for π phase difference. Here, the click occurs once in ten time-slots(Detection time is probabilistic) since the transmitted power is 0.1 photon/pulse. After thetransmission, Bob discloses detection instances to Alice, who can identify, from her
modulation data, which detector clicked at corresponding instances. Provided that the DET1
click represents “0” and the DET2 click “1”, Alice and Bob share an identical bit string,which can be a secret key because the bit information itself has not been leaked to the outside.
The system consists of a simple phase modulation scheme and a passive interferometer, andthus can realize stable operation at a high data rate.
We carried out an experiment to demonstrate the above scheme. A 0.8-µm LD light wasphase-modulated, attenuated, and then was photon-detected after an open-spaceinterferometer. The result is shown in Fig. 2. Proper correlation between Alice and Bob was
obtained, which confirmed the operation.
[1] K. Inoue, E. Waks, and Y. Yamamoto, Phys. Rev. Lett. 89 (2002) 037902.
[2] K. Inoue, E. Waks, and Y. Yamamoto, Phys. Rev. A 68 (2003) 022317.

0.1 photon/pulse

Aliceattenuator

coherent
pulse source

・・

Bob

・・

phase
modulation(0, π)DET1
DET2

Fig. 1. Configuration.
・・

detection
rate (%)

30

・・

20
10
0

(0,0)
(0,π) (π,0)
Alice

(π,π)

DET1
DET2

Fig. 2. Experimental result.
-32-

Bob

・・
・・

Research Activities in NTT Basic Research Laboratories Vol. 14 (June, 2004)

GaN-Based Vertical Cavity Surface Emitting Lasers
Takehiko Tawara, Hideki Gotoh, Tetsuya Akasaka, Naoki Kobayashi, and Tadashi Saitoh
Physical Science Laboratory
Optical devices based on III-nitride quantum wells (QWs) have been actively studied.
However, the refractive index contrasts between III-nitride and air are relatively small
compared with those in GaAs-based semiconductors and the reflectivity is about 18%. This
leads to an increase in the driving current needed for optical devices [1]. With lasers, one way
to reduce the lasing threshold is to use the vertical cavity surface emitting laser (VCSEL)
structure. If the cavity size is of the order of the emission wavelength, the spontaneousemission rate can be controlled and the lasing threshold can be reduced.
VCSEL structures usually consist of a cavity with active layers and distributed Braggreflectors (DBRs), which are formed by monolithic growth with the same kind of
semiconductor. When a high reflectivity DBR is constituted from GaN-based semiconductors,
however, the large lattice mismatch between each layer of the DBR generates surface
roughening and cracking of the cavity layer.
We prepared a GaN-based cavity layer including InGaN QWs on a SiC substrate andoxide-based DBRs separately. The VCSEL structure was formed by using a wafer bonding
technique after removing the SiC substrate by selective dry etching. We realized high quality
VCSEL structures without cracking or surface roughening (Fig. 1). The spectral linewidth ofthe cavity mode at the InGaN emission wavelength of 400 nm was less than 1 nm, and thisindicates that we realized a microcavity with low optical loss. Moreover, we measured theluminescence intensity from the fabricated VCSELs for different optical excitation powers atroom temperature (Fig. 2). A clear nonlinear characteristic was observed, and this shows that
the VCSEL is lasing. Furthermore, the spontaneous emission factor (the coupling efficiencyof the spontaneous emissions to the lasing mode) was about 0.01, and this is 1000 times more
efficient than in a typical edge-emitting laser [2].
In such a structure, there is an advantage in that the reflectivity and the stopband width of
the DBR can be chosen freely while maintaining the crystal quality of the cavity layers.
Moreover, the realization of strong exciton-photon coupling at room temperature will bepossible by using such high quality microcavities, because the exciton oscillator strength andbinding energy of III-nitride semiconductors are large compared with GaAs-based
semiconductors.
[1] H. Wang, et al., Appl. Phys. Lett. 81 (2002) 4703.
2.3E[2] T. Tawara, et al., Appl. Phys. Lett. 83 (2003) 830.
Intensity

Emission Intensity (a.u.)th

0.2 nm

370

380

390

400

410

Wavelength (nm)

Eth

0

10

20

30

40

50

Excitation Energy (nJ/pulse)

Fig. 1. Cross-sectional image of the VCSEL.
-33-

Fig. 2. Lasing characteristics.

Research Activities in NTT Basic Research Laboratories Vol. 14 (June, 2004)

Penrose-lattice Photonic Quasicrystal Laser
Masaya Notomi1, Hiroyuki Suzuki2, Toshiaki Tamamura3, and Keiichi Edagawa4
Physical Science Laboratory1, NTT Photonics Labs. 2, NTT Electronics3, Univ. of Tokyo4
Crystals have periodicity and translational symmetry. But there exist a certain class ofstructures called quasicrystals that do not posses periodicity nor translational symmetry, buthave long-range order and rotational symmetry. Quasicrystals have bandgap and density ofstates in a similar way to crystals, but some important concepts such as band structures, Blochtheorem, Brillouin zone cannot be defined. Concerning crystals, it has been known that lasing
action is possible in photonic crystals having optical gain because of some standing wave
formation at the photonic band edges. Then, what happens if we introduce gain into photonic
quasicrystals that do not have periodicity? Is coherent lasing possible?
From these backgrounds, we have fabricated photonic quasicrystal lasers with organic dyefor the first time. [1] Our quasicrystals have so-called Penrose lattice (shown in Fig. 1(left))
exhibiting 10-fold rotational symmetry which is inhibited in periodic crystals. By opticalpumping, we observed clear lasing action, and peculiar 10-fold rotationally symmetric spot
patterns shown in Fig. 1(right). Both of lasing wavelengths and spot patterns sensitively
depend on the quasilattice constant, indicating that lasing is due to the quasiperiodicity. Sharp
spot patterns also indicate that lasing occurs by delocalized coherent modes inside thequasicrystal.
Since we cannot use conventional band theory for quasicrystal, we instead used theirreciprocal lattice to analyze the lasing action, and successfully explained the observed lasing
wavelengths and spot patterns quantitatively. The reciprocal lattice of quasicrystals are very
unique comparing to crystals one. The reciprocal lattice of crystals have a Brillouin zone andany points outside it are equivalent to some points inside it. In the case for quasicrystals, allof them are basically non-equivalent, and thus a wide variety of lasing modes can exist. This
uniqueness of the reciprocal lattice is most distinguishable feature of quasicrystal lasers. In
fact, lasing action in periodic photonic crystals is restricted from the limitation of periodicity,
but quasicrystal lasers are free from those restrictions.
[1] M. Notomi, H. Suzuki, T. Tamamura, K. Edagawa, Phys. Rev. Lett. 92 (2004) 123906.

Fig. 1. Electron microscope image of the Penroselattice photonic quasicrystals (left). The
observed 10-fold rotationally symmetric spot
pattern for photonic quasicrystal lasers (right).
-34-

Fig. 2. Reciprocal lattice of thefabricated Penrose-latticephotonic quasicrystals(calculation).

Ⅱ．DataResearch Activities in NTT Basic Research Laboratories Vol. 14 (June, 2004)

International Symposium on Mesoscopic Superconductivity andSpintronics --- In the light of Quantum Computation --The symposium MS+S2004 was held during March 1-4, 2004, at NTT Atsugi R&D
Center in collaboration with Core Research for Evolutional Science and Technology - Japan
Science and Technology Agency (CREST-JST), Research and Development Association for
Future Electron Devices (FED), NTT Basic Research Laboratories, and NTT Communication
Science Research Laboratories.
Recently, mesoscopic superconductivity and spintronics have attracted much interest
because of their potential ability to produce novel and revolutionary devices, such as scalable
solid-state quantum computer. In this symposium, setting a key-word as “quantum
computation”, we NTT Basic Research Laboratories together with NTT Communication
Science Research Laboratories have invited the leading scientists in these fields and havepromoted active discussions including up-to-date topics. This biannual symposium was first
held in the year of 2000, and this is the third symposium.
On the 1st day, after the opening and welcome address by Dr. Hideaki Takayanagi, R&D
Fellow and the Director of NTT Basic research Laboratories, Dr. John. Martinis (NIST
Fellow) gave a plenary lecture with the title “Coherence in Josephson Phase Qubits”.
Including a lecture about superconducting flux qubit by prof. J. E. Mooij (Delft Univ.), there
were 11 oral presentations concerning qubit. After a short laboratory tour to SOR facility andqubit facilities, the 45 posters were presented in the evening session.
On the 2nd day, the 5 oral presentations discussed on quantum information theory andquantum algorithm including an exciting lecture by prof. Seth Lloyd (MIT). There were 5 oralpresentations discussed on spintronics The first demonstration of gate control of electron spin
was shown by NTT. The tunable magnetism in quantum dot device was also proposed by NTT.
In the evening session, the 40 posters were presented.
On the 3rd day, in the morning session, there were 6 oral presentations on spintronics. In
the afternoon, the excursion to Lake Ashi in Hakone was carried out and the banquet party
was held in Gotenba.
On the 4th day, Chalmers Univ., NTT-BRL, Kansas Univ., D-Wave Systems, CNRS
Grenoble, RIKEN-NEC, CEA-Saclay group presented quantum oscillations and coherent
control of superconducting qubit. There were 14 oral presentations.
The total number of participants was 203 (133 from outside of NTT). During theconference, participants were strongly impressed by high-quality presentations andstimulating discussions.

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Research Activities in NTT Basic Research Laboratories Vol. 14 (June, 2004)

International Symposium on Functional Semiconductor Nanosystems(FSNS2003)
The International Symposium on Functional Semiconductor Nanosystems (FSNS2003)
was held from 12 (Wed.) through 14 (Fri.) of November, 2003, at the NTT Atsugi R&D
Center in collaboration with New Energy and Industrial Technology Development
Organization (NEDO) and Japan Science and Technology Corporation (JST).
Ultra-small “nano-scale” materials with semiconducting properties have been attracting a
lot of attention for many years. Recently, the field has been largely advanced by coupling,interconnecting and integrating novel structures such as nanotubes, nanowires, and molecules,
and by introducing new properties such as mechanics, elasticity and magnetism. These novel“nanosystems” are expected to lead to new functionality that cannot be provided byconventional structures in semiconductor science and technology.
The purpose of FSNS2003 was to provide an international forum dedicated to the latest
progress related to these novel kinds of nanostructures. The symposium covered all aspects offabrication and characterization of semiconductor nanosystems - including growth andprocessing, and optical, electrical, elastic, structural, and mechanical properties - and theirapplications and dealt with all kinds of semiconductors, carbon nanotubes, and organic
materials. Papers were solicited on a wide variety of topics.
The opening and welcoming remarks were given by Dr. Hideki Takayanagi, Director of
NTT Basic Research Laboratories. On the second day, in his plenary talk, Prof. von Klitsing,
Max-Planck Institute, reviewed about the distinctive features of the quantum transport that
occurs in two-dimensional systems of high mobility electrons under microwave radiation.
There were 27 oral presentations, including 17 invited talks, and 43 poster presentations.
Totally, there were 71 presentations, which were categorized into three areas: transport andmechanical properties in nanostructures, advancement in the research of the carbon nanotube,
and self-organization of nanostrucutres and their characterization.
The participants were totally 164 people. All participants thoroughly enjoyed thehigh-quality presentations and discussions. They especially enjoyed the opportunity to talkwith researchers from different areas, which certainly led to many valuable suggestions andinsights. By organizing these interdisciplinary areas under the banner “semiconductor
nanosystems” and hosting conference like FSNS, we hope to advance the discussion of
nano-science and thereby accelerate the development of nanotechnology.

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Research Activities in NTT Basic Research Laboratories Vol. 14 (June, 2004)

Science Plaza 2003
Science Plaza 2003, the annual open house event of NTT Basic Research Laboratories, washeld on August 22, 2003 at the NTT Atsugi R&D Center. The purpose of Science Plaza 2003
was to introduce the latest research results both inside and outside of NTT Basic ResearchLaboratories and obtain feedback and opinions through discussions.
After opening remarks by Dr. Hideaki Takayanagi, Director of NTT Basic ResearchLaboratories, the symposium session began. The symposium featured three talks, “SiliconSingle Electron Devices and Their Application”, “Nanobioscience – Fusion of a Nerve
Function and Nanotechnology” and “New Materials Changing Optical Technology – Photonic
Crystal”, which were selected from the fields of device physics, materials science, andphysical science, respectively. In the afternoon session, Prof. Reiko Kuroda, Professor of the
Graduate School of Arts and Science at the University of Tokyo, gave a special lecture
entitled “Chiromorphology”, in which she spoke about molecule morphology and therecognition and invention of chirality.
The Poster Session, featured thirty-one of the latest research developments and provided
forum for lively debate among the participants. In addition, major research findings were
presented as a movie in the Video Theatre. We also conducted Lab tours. The tours gave
participants an opportunity to see the equipment used in NTT Basic Research Laboratories,
where are normally not open to the public. After the program was completed, a social
gathering was held in the evening in the dining room, where participants could continue theirproductive discussion.
Approximately 300 people from the research departments of universities, businessorganizations, and NTT groups attended Science Plaza 2003, which was an increase from lastyear’s event. The symposium was a huge success, and we sincerely thank all those who
participated.

Symposium session

Laboratory tour

-37-Research Activities in NTT Basic Research Laboratories Vol. 14 (June, 2004)

Award Winner’s List (Fiscal 2003)

Award onSuperconductivity
Science and Technology,
Forum ofSuperconductivity
Science and Technology

Japanese Journal ofApplied Physics
Paper Award

H. Takayanagi“Suggestion and demonstrationof a concept for devices with
control of superconductivity
coherence”

June 24,
2003

A. Fujiwara
Y. Takahashi“Mechanism of Single-Charge
Detection using Electron-Hole
System in Si-wire Transistors”

Aug. 30,
2003“Study of single-electron
dynamics in quantum dot”

Nov. 26,
2003

The 5th Sir Martin Wood
T. Fujisawa
prize

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Research Activities in NTT Basic Research Laboratories Vol. 14 (June, 2004)

In-house Award Winner’s List (Fiscal 2002)

NTT R&D Award

K. Inoue“Quantum Cryptography using
Single Photon Sources”

Feb. 12,2003

NTT R&D Award

M. Kasu“Diamond Semiconductors”

Feb. 12,
2003

Award forAchievements by
Director of Basic
Research
Laboratories

H. Inokawa“Pioneering Study for Single-electron Mar. 22,
Multiple-valued Logic Devices”
2004

Award forAchievements by
Director of Basic
Research
Laboratories

T. Koga
Y. Sekine
J. Nitta“Spin Control in Semiconductors
with Gate Electrodes”

Mar. 22,
2004

Award forAchievements by
Director of Basic
Research
Laboratories

M. Kasu“Study for High-frequency Diamond
FETs”

Mar. 22,2004

Renewal of He Liquefaction System

Mar. 22,
2004

Award forDistinguished Services
K. Igetaby Director of Basic
Y. Harada
Research
Laboratories
Award for
Excellent Papers by
Director of Basic
Research
Laboratories
Award for
Excellent Papers by
Director of Basic
Research
Laboratories

T. Hayashi“Coherent Manipulation ofElectronic States in a Double
Quantum Dot” Phys. Rev. Lett. Vol.
91, 226804 (2003)

Mar. 22,
2004

T. Makimoto“High current gain (> 2000) of
GaN/InGaN double heterojunction
bipolar transistor using baseregrowth of p-InGaN” Appl. Phys.
Lett. Vol. 83, 1035 (2003)

Mar. 22,
2004

-39-

Research Activities in NTT Basic Research Laboratories Vol. 14 (June, 2004)

List of Visitor’s Talks (Fiscal 2003)

l. Device Physics
Date

SpeakerMay

5 Prof. F. Rosei

May

29 Prof. S. MasudaJune

16 Prof. M. Watanabe

July

15 Dr. V. Tonchev

Sept.

9 Prof. S. Stoyanov

Sept. 19 Dr. V. Tonchev

Affiliation"Topic"Universite du Quebec, Canada“Organic Molecules on a Metal Surface:Fundamentals and Applications”
University of Tokyo“Local electronic states at a solid surface andchemical reactions studied by metastable atomelectron spectroscopy”
Tokyo Institute of Technology“Present status and future prospects of surface
studies by LEEM and PEEM”
Bulgarian Academy of Science, Bulgaria“Models of Step Bunching: “Classical” and New
Results”
Institute of Physical Chemistry, Bulgaria“Electromigration induced bunching of steps - a key
to understanding the processes at the Si crystal
surface”
Bulgarian Academy of Science, Bulgaria“Step Bunching on Vicinal Crystal Surfaces: From
Models to Experiments and Back”

ll. Materials Science
Date

April

Speaker

9 Prof. T. Martin

Affiliation"Topic"Universite de la Mediterranee, France“Bell inequalities and entanglement innormal-superconductor junctions and in carbon
nanotubes”“Electron spin teleportation with a quantum dot
array”-40-

Research Activities in NTT Basic Research Laboratories Vol. 14 (June, 2004)

July

3 Dr. M. Thorwart

July

22 Prof. J. Kono

July

23 Dr. M. Thorwart

July

25 Dr. M. C. Geisler

July

30 Prof. E. Mendez

Nov.

18 Prof. J. E. Mooij

Dec.

22 Prof. S.-IK Lee

Feb.

25 Prof. G. Falci

Feb.

26 Prof. W. PeihengMar.

8 Prof. A.D. Zaikin

Mar.

10 Dr. F. Pistolesi

Mar.

15 Prof. D. B. Haviland

Mar.

15 Prof. F. W. J. Hekking

Delft University of Technology, Netherlands“Decoherence in superconducting flux qubits
coupled to a SQUID detector”
Rice University, USA“Ultrafast Optical Control of Band Structure andFerromagnetism in Semiconductors”
Delft University of Technology, Netherlands“Multi-photon transitions in superconducting flux
qubits”
Max-Planck-Institute for Physics, Germany“Experimental Evidence for a Landau Level
Coupling Induced Rearrangement of the Hofstadter
Butterfly”
State University of New York at Sony Brook, USA“An Overview of Recent Research in Stony Brook's
Qunatum Structure Group”
Delft University of Technology, Netherlands“Measurements on Flux Qubits”
Pohang University of Science and Technology,
Korea“Is electron doped infinite layer superconductivity
similar to hole doped cuprate superconductivity?”
Universit a di Catania, Italy“Interaction of Josephson qubits with strong QED
cavity modes:dynamical entanglement transfer andnavigation”
Nanjing University, China“Intrinsic Josephson Junctions in High Temperature
Superconductors and their Possible Electronic
Applications”
Forschungszentrum Karlsruhe, Germany“Transport of interacting electrons in metallic
quantum dots and diffusive wires”
LPMMC-CNRS Grenoble, France“Energy dependence of current noise insuperconducting/normal metal structures”
The Royal Institute of Technology, Sweden“Quantum Josephson Junctions at KTH”
LPMMC-CNRS Grenoble, France“Coherent oscillations in a current-biased
dc-SQUID”-41-

Research Activities in NTT Basic Research Laboratories Vol. 14 (June, 2004)

lll. Quantum Electron Physics
Date

SpeakerJune

4 Prof. V. P.-Solorzano

June

4 Prof. F. Habel

July

23 Mr. Y. KatoJuly

24 Dr. T. D. Mishima

Nov.

18 Prof. P. Lindelof

Nov.

26 Prof. C. Manfredotti

Nov.

27 Prof. R. Nicholas

Mar.

9 Prof. E. Munoz

Mar.

25 Dr. D. J. ReillyMar.

25 Dr. A. Denisenko
Dr. E. Kohn

Affiliation"Topic"University of Stuttgart, Germany“Comparison of the material properties of GaInN
structures grown with ammonia and DMHy as
nitrogen precursors”
University of Ulm, Germany“Determination of dislocation density in epitaxiallygrown GaN using an HCl etching process”
University of California, Santa Barbara, USA“Gigahertz electron spin manipulation using
G-tensor modulation resonance”
University of Oklahoma, USA“TEM Study of InSb Reconstructed
Surfaces/Quantum Wells and InGaAs Quantum Dots
& SDR Study of Si/SiO2 Interface Defects”
University of Copenhagen, Denmark“Electronic Transport through Carbon Nanotubes”
University of Torino, Italy“Blue light sensitization of CVD diamond detectors”
University of Oxford, UK“Quantum box superlattice transport in InAs/GaSb
superlattices”“Optical properties of carbon nanotubes”
University Politecnica de Madrid, Spain“Photodetectors and HEMT devices based on
nitrides”
University of New South Wales, Australia“The 0.7 Conductance Feature above the Kondo
Temperature”“Phosphorus in Silicon Quantum Computation”
University of Ulm, Germany“Theoretical study of a projected RF-performance of
sub-µm lateral field emitting structures based oncarbon nanotubes”-42-Research Activities in NTT Basic Research Laboratories Vol. 14 (June, 2004)

lV. Quantum Optics & Optical Materials
Date

Speaker

April 25 Dr. M. Ono

July

10 Dr. T. Yamashita

July

14 Prof. K. Yamauchi

Aug. 19 Prof. J. H. Wolter

Oct.

21 Prof. J. Limpouch

Nov.

14 Prof. M. Mitsunaga

Dec.

12 Prof. J. Zi

Jan.

19 Prof. R. MorandottiMar.

16 Prof. M. Kristensen

Affiliation"Topic"University of Tokyo“Gigantic optical nonlinearity in one-dimensional
strongly-correlated electron systems”
Georgia Institue of Technology, USA“Active and Emissive Photonic Crystal
Nano-Architectures”
University of Tokyo“Control of Molecules in Intense Laser Fields”
Eindohoven University of Technology, Netherlands“Photonic Integration: Challemges for Material
Research”
Czech Technical University in Prague,
Czech Republic“Simulations of femtosecond K-alpha emission fromshort-pulse laser-target interactions”
Kumamoto University“Quantum Interference Effects: Principles andApplications”
Fudan University, China“Liquid surface waves and negative refraction”
Universite du Quebec, Canada“Optical discrete solitons”
Technical University of Denmark, Denmark“Planar PBG Pipes at COM”

-43-

Research Activities in NTT Basic Research Laboratories Vol. 14 (June, 2004)

Research Activities of Basic Research Laboratories in 2003
The numbers of research papers, presentations at the international conferences and applied
patents amounted to 190, 264, and 40 in Basic Research Laboratories as a whole. All numbers
according their research areas are as follows.
Research Papers Published in International
Journals (2003. 1 - 2003. 12)
Device Physics
Material Science
Materials
Science
Quantum Electron
Physics
Quantum Optics &Optical Materials
0

10

20

30

40

50

60

70

Number of Papers

Presentations at International
Conferences (2003. 1 - 2003. 12)
Device Physics
Materials Science
Science
Material

Quantum Electron
Physics
Quantum Optics &Optical Materials
0

20

40

60

80

100

120

Number of Presentations

Applied Patents (2003. 1 - 2003. 12)

Device Physics

Materials
Science
Material Science
Quantum Electron Physics
Quantum Optics &Optical Materials
0

2

4

6

8

10

12

Number of Applied Patents

-44-

14

16

18

Research Activities in NTT Basic Research Laboratories Vol. 14 (June, 2004)

The major journals and the number of published papers are shown below.
General Science Journals
Name(IF2002)*Nature(30.432)

Numbers2

Specialized Journals
NameJapanese Journal of Applied Physics
Applied Physics Letters
Physical Review B
Journal of Applied Physics
Physica E(IF2002)*(1.280)(4.207)(3.327)(2.281)(1.107)(2.986)(7.323)(2.140)(3.751)(23.672)(15.901)(6.801)(5.033)

Physical Review A
Physical Review Letters
Surface Science
Macromolecules
Review of Modern Physics
Account of Chemical Research
Advanced Materials
Nano Letters

Numbers
20
14
14
8
8
7
5
4
2
1
1
1
1

*IF2002: Impact factor 2002 （Journal Citation Reports, 2002）

The average impact factor for individual research papers from all NTT Basic ResearchLaboratories is 2.87.
The major international conferences and their number of presentation are shown below.
Conferences

Numbers

International Symposium on Functional Semiconductor Nanosystems(FSNS 2003)

22

Carrier Interactions and Spintronics in Nanostructures (CISN 2003)
7th International Conference on Atomically Controlled Surface andInerfaces and Nanostructures (ACSIN-7)
5th International Conference on Nitride Semiconductors (ICNS-5)
The 15th International Conference on Electronic Properties of
Two-Dimensional System (EP2DS-15)
2003 Material Research Society Meeting
The 2003 International Conference on Solid State Devices andMaterials
The 16th International Symposium on Superconductivity (ISS)
Conference on Laser and Electro-Optics/Quantum Electronics andLaser Science Conference
The 5th Laser Cooling Workshop
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15
13
11
9
8
6
5
4
4

Research Activities in NTT Basic Research Laboratories Vol. 14 (June, 2004)

List of Invited Talks at International Conferences (2003)

I. Device Physics(1) Y. Takahashi, Y. Ono, S. Fujiwara, and H. Inokawa, “Development of silicon
single-electron devices”, The 4th International Symposium on Nanostructures andMesoscopic Systems (NanoMES2003), Tempe, USA (Feb. 2003).
(2) Y. Homma, “In situ observations using ultrahigh vacuum scanning electron microscopy”,
Microscopy and Microanalysis, San Antonio, USA (Aug. 2003).
(3) Y. Homma, “Self-assembled nanotube networks for nano-device applications”, 4thInternational Symposium on Atomic Level Characterizations for New Materials andDevices (ALC’03), Hawaii, USA (Oct 2003).
(4) S. Suzuki, Y. Watanabe, Y. Homma, T. Ogino, S. Heun, L. Gregoratti, A. Brinov, B.
Kaulich, and M. Kiakinova, “Photoemission spectromicroscopy and spectroscopy ofcarbon nanotubes”, AVS international Symposium, Baltimore, USA (Nov 2003).
(5) Y. Takahashi, S. Fujiwara, and S. Horiguchi, “Silicon nano-wire and quantized
conductance”, International workshop on smart interconnects, Atami, Japan (Nov. 2003).
(6) H. Hibino, Y. Homma, C.-W. Hu, M. Uwaha, T. Ogino, and I. S. T. Tsong, “Structuraland morphological changes on surface with multiple phases studied by low-energy
electron microscopy”, 7th International Conference on Atomically Controlled Surfaces,
Interfaces and Nanostructures (ACSIN-7), Nara, Japan (Nov. 2003).
(7) Y. Takahashi, Y. Ono, S. Fujiwara, K. Nishiguchi, and H. Inokawa, “Silicon
single-electron devices operating with MOSFETs”, Sixth International Conference on
New Phenomena, Maui, USA. (Dec. 2003).
(8) Y. Watanabe, S. Suzuki, Y. Homma, and T. Ogino, “Spectromicroscopy of carbon
nanotubes”, 2nd Int. Conf. on Materials for Advanced Technology, Singapore (Dec.
2003).
(9) Y. Takahashi, Y. Ono, S. Fujiwara, K. Nishiguchi, and H. Inokawa, “Silicon nano-devices
and single-electron devices”, 2003 International Semiconductor Device Research
Symposium (ISDRS2003), Washington D.C., USA (Dec. 2003).
(10) Y. Homma, “Suspended carbon nanotube architectures: growth control and opticalproperties”, 12th International Conference on Advanced Materials and Devices 2003,
Jeju island, Korea (Dec. 2003).
(11) Y. Watanabe, B. Satyaban, T. Kawamura, S. Fujikawa, and N. Yamamoto, “Growth andCharacterization of Vertically Aligned InP Nanowires on Semiconductor Substrates”,
12th Int. Workshop the Physics of Semicond. Dev., Chennai, India (Dec. 2003).
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Research Activities in NTT Basic Research Laboratories Vol. 14 (June, 2004)(12) Y. Watanabe, “InP nanowire growth on semiconducting materials by metal organic vapor
phase epitaxy”, Int. Conference on Nano Science and Technology, Kalkata, India (Dec.
2003).

II. Materials Science(1) H. Takayanagi, S. Saito, H. Tanaka, and H. Nakano, “Readout of the qubit state with a
SQUID”, First International International Conference on Nanoelectronics
Ferromagnetism in quantum-dot-array systems, Lancaster, UK (Jan. 2003).
(2) H. Takayanagi, S. Saito, H. Tanaka, and H. Nakano, “Readout of the qubit state with adc-SQUID”, Int. Symp. On Advanced Physical Fields 8, Tsukuba, Japan (Jan. 2003).
(3) J. Nitta, “Rashba spin-orbit interaction and spin-interference in nano-structures”,
International Workshop “Coherence in Nanosystems” Spin-related transport insemiconductors, Soul, Korea (Feb. 2003).
(4) Y. Jimbo,“ Plasticity in cultured neuronal network”, Int. Workshop on “Biology andPhysics at Interfaces”, Julich, Germany (May 2003).
(5) K.Torimitsu, “Nanobioscience-molecular device and neural functions”, Workshop on
nanotechnology and postgenomics, New Castle, UK (Jun. 2003).
(6) K. Torimitsu, “On Bio and Nano Technology”, International Conference on Composites
Engineering, ICCE/10, New Orleans, USA (Jul. 2003).
(7) A. Matsuda, “Inhomogeneity in the electronic state of Bi-2212 - from the insulating tosuperconducting state -”, Self Organized Strongly Correlated Electron Systems, Santorini,
Greece (Aug. 2003).
(8) K. Ajito, “Nanometer-scale Raman Spectroscopy of Neurons”, Microscopy andMicroanalysis 2003, Quebec Convention Center, San Antonio, USA (Aug. 2003).
(9) K. Semba, “Single Shot Readout of the Flux-Qubit”, Hot Topics in Quantum Statistical
Physics: q-Thermodynamics, q-Decoherence and q-Motors, Leiden University, Holland(Aug. 2003).
(10) J. Nitta and T. Koga, “Gate Control of Electron Spin in Semiconductor Nanostructure”,
Photonics and Spintronics in Semiconductor Nanostructures toward Quantum
Information Processing, Kyoto, Japan (Nov. 2003).
(11) H. Takayanagi, “ Single-shot measurement of the qu-bit state with a dc-SQUID”, The 9th
Japan-US Joint seminar Quantum Correlations and Coherence, Yatsugatake, Japan (Sep.
2003).
(12) M. Naito, “Search for new high-Tc superconductors by molecular beam epitaxy”, The
8th IUMRS International Conference on Advanced Material (IUMRS-ICAM2003),
Yokohama, Japan (Oct. 2003).
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Research Activities in NTT Basic Research Laboratories Vol. 14 (June, 2004)(13) M. Naito, “Large-area RE-123 thin films for microwave applications”, The 16th
International Symposium on Superconductivity (ISS2003), Tsukuba, Japan (Oct.
2003).
(14) K. Totimitsu, “Neural Functions and Nano-Bio Device”, Sweden-Japan Workshop on
Bionanotechnology, Kyoto, Japan (Nov. 2003).
(15) M. Naito, “MgB2 thin films”, Program committee of The European Network For
Superconductivity, Spain (Nov. 2003).

III. Quantum Electron Physics(1) K. Kanisawa, Y. Tokura, H. Yamaguchi, and Y. Hirayama, “Direct probing of
local-density-of-states in semiconductor nanostructures”, Photonics West, San Jose, USA(Jan. 2003).
(2) K. Kanisawa, Y. Tokura, H. Yamaguchi, and Y. Hirayama, “Scanning tunnelingspectroscopy study of zero-dimensional structures at the InAs surface”, 30th Conf. on
Phys. and Chem. of Semicond. Interfaces (PCSI-30), Salt Lake City, USA (Jan. 2003).
(3) H. Yamaguchi, S. Miyashita, and Y. Hirayama “Fabrication and Characterization of
InAs-based Electromechanical Systems”, 2003 RCIQE International Seminar on
Quantum Nanoelectronics for Meme-Media-Based Information Technologies, Sapporo,
Japan (Feb. 2003).
(4) T. Fujisawa, “Single electron dynamics in quantum
Nanotechnology Colloquium, Lund, Sweden (Mar. 2003).

dots”,

Sweden-Japan(5) T. Makimoto, K. Kumakura, and N. Kobayashi, “npn-Type Nitride Heterojunction
Bipolar Transistors”, 2003 Asia-Pacific Workshop on Fundamental and Application ofAdvanced Semiconductor Devices (AWAD2003), Busan, Korea (Jun. 2003).
(6) M. Kasu and N. Kobayashi, “Influence of epitaxy on the surface conduction of diamondfilm”, 2003 European Materials Research Society Spring Meeting (E-MRS2003),
Strasbourg, France (Jun. 2003).
(7) Y. Hirayama, “Quantum Hall Effects at Landau Level Crossings”, Int. Symp. on
Quantum Hall Effects: Past, Present, and Future, Stuttgart, Germany (Jul. 2003).
(8) T. Fujisawa, “Single electron dynamics in quantum dots”, The 11th International
Conference on Modulated Semiconductor Structures (MSS11), Nara, Japan (Jul. 2003).
(9) T. Nishida, T. Ban, and N. Kobayashi, “Nitride UV emitters”, 30th Int. Symp. Compound
Semicond. (ISCS2003), San Diego, USA (Aug. 2003).
(10) Y. Hirayama, “Electronic States and Their Control in Semiconductor Quantum Dots”,
Trends in Nanotechnology (TNT2003), Salamanca, Spain (Sep. 2003).
(11) T. Matsuoka, H. Takahata, T. Mitate, S. Mizuno, and T. Makimoto, “Polarity of GaN-48-

Research Activities in NTT Basic Research Laboratories Vol. 14 (June, 2004)

grown on a several substrates by MOVPE”, 8th Wide-Bandgap Ⅲ-Nitride Workshop,
Richmond, USA (Sep. 2003).
(12) T. Matsuoka and H. Okamoto, “MOVPE Growth of InN and its Band-Gap Energy”, 8th
Wide-Bandgap Ⅲ-Nitride Workshop, Richmond, USA (Sep. 2003).
(13) T. Matsuoka, H. Okamoto, M. Nakao, H. Harima, H. Takahata, T. Mitate, S. Mizuno, Y.
Uchiyama, and T. Makimoto: “MOVPE Growth of Wurtzite InN and its Optical
Characteristics”, 2003 Int. Conf. on Solid State Devices and Materials (SSDM2003),
Tokyo, Japan (Sep. 2003).
(14) H. Yamaguchi, K. Kanisawa, S. Miyashita, and Y. Hirayama, “InAs/GaAs(111)A
Heteroepitaxial System”, 5th International Workshop on Epitaxial Semiconductors on
Patterned Substrates and Novel Index Surfaces (ESPS-NIS2003), Stuttgart, Germany(Oct. 2003).
(15) T. Fujisawa, “Coherent charge oscillations in a semiconductor double quantum dot”, Int.
Workshop on Correlation, Decoherence and Spin Effects in Simple and Complex
Quantum Dot Systems, Bad Honnef, Germany (Oct. 2003).
(16) T. Nishida, “GaN-free Transparent Structure for Ultraviolet Light Emitting Diodes”,
Phys. of Light-Matter Coupling in Nanostructures (PLMCN3), Sicily, Italy (Oct. 2003).
(17) Y. Hirayama and T. Fujisawa, “Carrier Dynamics and Coherent Oscillation in Quantum
Dots”, 6th Int. Conf. New Phenomena in Mesoscopic Structures and The 4th Int. Conf.
Surface and Interfaces in Mesoscopic Devices (NPMS-6/SIMD-4), Hawaii (Nov. 2003).
(18) T. Matsuoka, H. Okamoto, M. Nakao, H. Takahata, T. Mitate, S. Mizuno, Y. Uchiyama,
H. Harima, and T. Makimoto, “MOVPE Growth of Wurtzite InN and Experimental
Consideration of its Optical Characteristics”, ONR Indium Nitride Workshop (ONR),
Fremantle, Australia (Nov. 2003).
(19) T. Fujisawa, “Dynamics of single-electron charge and spin in semiconductor quantumdots”, Int. Conf. Quantum Information (ICQI), Kyoto, Japan (Dec. 2003).
(20) T. Fujisawa, “Dynamics of single electron charge and spin in semiconductor quantumdots” Solid State Quantum Information Processing Conference, Amsterdam, The
Netherland (Dec. 2003).

IV. Quantum Optics & Optical Materials(1) H. Kamada, H. Gotoh, H. Ando, T. Takagahara, and J. Temmyo, “Quantum gate
operation of exciton qubits in semiconductor quantum dots”, Photonics West 2003, San
Jose, USA (Jan. 2003).
(2) A. Shinya, M. Notomi, E. Kuramochi, T. Shoji, T. Watanabe, T. Tsuchizawa, K. Yamada,and H. Morita, “Functional Components in SOI Photonic Crystal Slabs”, SPIE Photonics
West, Optoelectronics 2003, San Jose, USA (Jan. 2003).
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Research Activities in NTT Basic Research Laboratories Vol. 14 (June, 2004)(3) H. Kamada, H. Gotoh, H. Ando, and T. Takagahara, “Quantum dot exciton Rabi
oscillation and quantum gate operation”, 8th Int. Symp. on Advanced Physical Fields,(APF8), Tsukuba, Japan (Jan. 2003).
(4) H. Kamada, “Quantum Computation with Quantum Dot Excitons”, Int. Conf. on
Non-equilibrium Carrier Dynamics in Semicond., Modena, Italy (Jul. 2003).
(5) H. Kamada, “Quantum Computation with Quantum Dot Excitons”, FST2003, Chiba,
Japan (Jul. 2003).
(6) M. Yamashita, “Dynamics of evaporative cooling and growth of a Base-Einsteincondensate”, 12th International Laser Physics Workshop Hamburg, Germany (Aug.
2003).
(7) Y. Tokura, “Spin Structures in Quantum Dot System”, Workshop on Computational
Approaches Towards the Electronic Properties of Quantum Dots, Chicago, USA (Sep.
2003).
(8) H. Nakano, T. Nishikawa, and K. Oguri, “Time-resolved absorption spectroscopy using
ultrashort soft x-ray pulse from femtosecond laser-produced plasma”, 9th Conference on
Laser Optics (LO2003), St. Petersburg, Russia (Sep. 2003).
(9) H. Nakano, T. Nishikawa, K. Oguri, and N. Uesugi, “Femtosecond laser plasma x-ray fortime-resolved spectroscopy”, 7th International Conference on Optics (ROMOPTO2003),
Constantza, Romania (Sep. 2003).
(10) H. Nakano, “Time-resolved absorption spectroscopy using ultrashort soft x-ray pulses
generated by femtosecond laser pulse”, International Symposium on Ultrafast Intense
Laser Science 2: Technology, Trends, Propagation and Interaction (ISUILS2), Quebec,
Canada (Sep. 2003).
(11) M. Notomi, “Photonic-Band-Gap Waveguides and Resonators”, Intl. Photonics Technol.
Conf. 2003 (IPTC2003), Soul, Korea (Sep. 2003).
(12) M. Notomi, “Photonic-Band-Gap Waveguides and Resonators”, Annual Meeting of IEEE
Lasers and Electro-Optics Society (LEOS2003), Tucson, USA (Oct. 2003).
(13) M. Notomi, “Lasing action in organic photonic crystal and quasicrystal”, The 5th Pacific
Rim Conf. on Lasers and Electro-Optics CLEO/Pacific Rim2003), Taipei, Taiwan (Dec.
2003).

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Editorial Committee
Koji Sumitomo
Hiroo Omi
Hisashi Sato
Ryuzi Yano

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: kensui@will.brl.ntt.co.jp