bluuebunny/crossref_metadata_2025 huggingface dataset:
Monte-Carlo Simulation on Moderation of Positrons in Rare-Gas Solids
Authors: Toshinori Michishita Toshinori Michishita
Published: October 2002

A Monte-Carlo code is newly developed and is used for studying the
moderation of positrons in rare-gas solids.
The mechanisms included are the interactions with excitons and phonons
as well as the elastic and inelastic collisions.
The analyses give the cross sections for the rare-gas solids of Ne, Ar and Xe.
The simulation results give the implantation profiles for positrons incident onto the rare-gas solid and the energy dependence of the average depth.
The fraction of positrons emerging from the incident surface is ∼40% even without any contribution from the implanted positrons.
The exciton effect plays a predominant role in determining the behavior of the positrons in the rare gases, resulting in a decreased implantation depth and large backscattering fraction.
A brief comparison between the simulation results and available experimental ones is performed.
One Bond-Type Migration of Phosphorus in Silicon by Interstitialcy Mechanism
Authors: Yoshida Masayuki , Kamiura Yoichi , Tsuruno Reiji , Takahashi Manabu , Tomokage Hajime
Published: October 2002

It is assumed that an interstitial phosphorus atom and a self-interstitial, Pi and I,
are of the interstitialcy type. One bond-type migration is applied to their migration. It
is concluded that there is essentially no difference between the migrations of a P-I pair,
(PI), and Pi by the interstitialcy mechanism and between the chemical processes for the
formation-dissociation of (PI) and the kick-out mechanism of Pi.
Confinement of Nonneutral Spheroidal Plasmas in Multi-Ring Electrode Traps
Authors: Akihiro Mohri Akihiro Mohri , Hiroyuki Higaki Hiroyuki Higaki , Hitoshi Tanaka Hitoshi Tanaka , Yohei Yamazawa Yohei Yamazawa , Masayuki Aoyagi Masayuki Aoyagi , Tetsumori Yuyama Tetsumori Yuyama , Toshinori Michishita Toshinori Michishita
Published: October 2002

A nonneutral spheroidal plasma can be settled in a rigid rotor equilibrium inside a closed conducting cell independently of induced image charges on the cell wall if the electrostatic potential distribution on the wall surface is set equal to the sum of the external hyperbolic potential (r
2 - 2z
2) and the self-potential produced by the plasma. A confinement system equipped with a train of properly biased ring electrodes can approximately generate any axisymmetric potential, including the above field. Experiments on confinement of electron spheroids in such a system showed that the confinement time became the longest when the condition to diminish the image charge effects was satisfied. The observed frequency of the centre-of-mass harmonic oscillation of the plasma in this configuration was in good agreement with the estimated one.
Energy Distribution of Field Emitted Charged Particles during Beam Propagation
Authors: Cho Guangsup , Kim Young-Guon , Kim Young-Sam , Choi Eun-Ha
Published: October 2002

The energy distribution during beam propagation in a diode space has been calculated quantitatively for cold
cathode electrons and liquid metal ions. Especially, the energy spread and the peak energy shift dependence on the
emission surface temperture for liquid gallium ions are verified to be the order of 1 eV even for a temperature
increment of ∼100 K.
Impact of Metallization Films on Scattered-Light Alignment for X-Ray Lithography
Authors: Miyatake Tsutomu , Hirose Masaoki , Shoki Tsutomu , Ohkubo Ryo , Yamazaki Kuniaki
Published: October 2002

The degradation of overlay accuracy due to metallization (i.e., aluminum copper physical
vapor deposition (PVD) process) on electronics devices is reported. In a video-based scattered-light alignment (SLA) system for X-ray lithography, the metal layer on the alignment mark
structure affects the alignment signal quality. In this paper, we specifically focus on the
significant effects of aluminum (AL) metallization on the performance of the scattered-light
alignment (SLA) system. The SLA system demonstrated an overlay accuracy of 10.1 nm or less smaller (mean + 3σ) for Al films of 0.1, 0.2, 0.3 and 0.4 µm thickness. Only the 1-µm-thick
Al-sputtered wafer showed a significantly poor performance of 44.4 nm error (mean + 3σ). The
SLA system employs two different types of alignment marks: one type uses narrow edges,
while the other types uses wide edges. We estimated the mark-related alignment error using the
two different types of alignment marks. The results showed that the narrow edges of the
alignment marks had the advantage of smaller mean shift error compared to the wide edges of
the alignment marks. Furthermore, we discuss an asymmetry-induced error in thick Al
metallization.
Synthesis of Silicon-Containing Photoresists for ArF Excimer Laser Lithography
Authors: Kim Young-Dae , Park Sang-Jin , Lee Haiwon , Kim Eung-Ryul , Lee Sang-JunChoi
Published: October 2002

Two new positive-type photoresists which are terpolymers of
methyl methacrylate (MMA), 1,3-bis(trimethylsilyl)isopropyl
methacrylate (BPMA) and either methacrylic acid (MAA) or maleic
anhydride (MA) have been synthesized for ArF excimer laser
lithography. Terpolymers have a silicon containing acid labile
protecting group which can be deprotected by photo acid generator
(PAG). Terpolymers have a good thermal stability up to 140°C
and the glass transition temperature (T
g) of
poly(MMA
x
-BPMA
y
-MA
z
) was 119°C. The minimum
feature resolution with 0.17 µm L/S pattern was achieved with
poly(MMA5.9-BPMA2.1-MAA2.0) by using an ArF exposure
system with 17 mJ/cm2 energy dose.
Silylation and Dry Development of Chemically Amplified Resists SAL601*, AZPN114*1, and Epoxidised Resist (EPR*1) for High Resolution Electron-Beam Lithography
Authors: Tegou Evangelia , Gogolides Evangelos , Argitis Panagiotis , Raptis Ioannis , Meneghini Giancarlo , Cui Zheng
Published: October 2002

A comparative study of high resolution positive imaging obtained after liquid-phase silylation and dry development
with two commercial and one experimental electron-beam chemically amplified resists (CARs), namely SAL601, AZPN114,
and EPR (EPoxidised Resist) is presented. 150 nm lines and spaces are obtained for all resists, while 100 nm lines are
achieved with AZPN114 and EPR at 50 kV exposures. The exposure doses for AZPN114 and SAL601 are 10 µC/cm2 and 20 µC/cm2,
respectively, while EPR is considerably faster (1.5 µC/cm2). Chlorosilanes are used for EPR silylation, while SAL601 and
AZPN114 are silylated with hexamethyl cyclo tri silazane (HMCTS) or bis (di methyl amino) di silane (B(DMA)DS). SAL601
shows less silylation selectivity between exposed and unexposed areas possibly due to insufficient crosslinking.
Implications of the presented processes on low-energy electron-beam lithography are discussed.
A Simulation of Electron Scattering in Magnetic Materials
Authors: Tamura Keiji , Yasuda Masaaki , Murata Kenji , Kotera Masatoshi
Published: October 2002

A new simulation model is proposed to calculate the electron scattering in magnetic materials. It takes into account not only the three-dimensional electron trajectory, but also the electron spin transport along the trajectory. The mechanisms considered in the magnetic materials are the Lorentz force, the spin-orbit interaction, and the secondary electron generation. The band structure of the outer-shell electrons in the material is considered in the cascade process of low-energy secondary electron generation. The calculated energy dependence of the spin-polarization shows a reasonable agreement with the experimental value.
Resonance Characteristics of Micro Cantilever in Liquid
Authors: Hirai Yoshihiko , Mori Ryosuke , Kikuta Hisao , Kato Nobuhiro , Inoue Koji , Tanaka Yoshio
Published: October 2002

The resonance characteristics of a micro cantilever are experimentally and
theoretically studied. The micro cantilever is vibrated by thermal excitation using
laser exposure and the frequency responses of the micro cantilever in air, acetone
and water are experimentally evaluated based on an optical measurement
technique. It is demonstrated that the resonance frequencies in water decrease
to about one-tenth of the values in air. Also, the frequency responses are
calculated using the string of beads model taking into consideration the drag
force by viscous fluids. The calculation results show good agreement with the
experimental results.
Fabrication of a Silicon Micro-Probe for Vertical Probe Card Application
Authors: Kim Yong-Dae , Sim Jun-Hwan , Nam Jae-Woo , Lee Jong-Hyun
Published: October 2002

We report on the fabrication of a new type of probe card that uses a porous silicon micromachining
technique. Curled cantilever tips are fabricated using surface tension and the difference in the thermal
expansion coefficient between the films. The contact resistance of cantilever tips with an aluminum pad is
basically below 1 Ω and there is no change of contact resistance after 700,000 contacts.
Energy Quenching Effects on Dry-Etching Durability of Copolymers and Polymer Blends of Vinylnaphthalene or α-Methyl Styrene with Methyl Methacrylate
Authors: Masahito Kushida Masahito Kushida , Yoshinori Yoshida Yoshinori Yoshida , Kieko Harada Kieko Harada , Kyoichi Saito Kyoichi Saito , Kazuyuki Sugita Kazuyuki Sugita
Published: October 2002

Durabilities for O2 reactive ion etching (O2RIE) were studied as a function of number-average molecular weight (Mn) of poly(methyl methacrylate) [PMMA], poly(α-methyl styrene) [PMSt] and poly(2-vinylnaphthalene) [PVN]. Etching rates were independent of the Mn and in the descending order of PMMA, PMSt and PVN. Dry-etching durability which was defined as the reciprocal of etching rate relative to PMMA, of PVN was higher than that of PMSt. 2-Vinylnaphthalene (VN) moiety was found to be more effective for enhancing dry-etching durability than α-methyl styrene (MSt). Dry etching durabilities of copolymers (PMMA-co-MSt, PMMA-co-VN) were equal to those of polymer blends (PMMA/PMSt, PMMA/PVN) of the same composition and larger than the values calculated from the constituent homopolymers assuming the wt% or vol% additivity as the estimated bombardment probability by ion and neutral active species.
Scanning Tunneling Microscopy Study of Silicide Structure on Si(110) Surface
Authors: Izumi Ono Izumi Ono , Masamichi Yoshimura Masamichi Yoshimura , Kazuyuki Ueda Kazuyuki Ueda
Published: October 2002

Surface structures of Ni-deposited Si(110) after annealing at various temperatures have been investigated using scanning tunneling microscopy (STM). After deposition of a few monolayers (ML) of Ni at room temperature, Ni clusters cover the surface homogeneously, where initial stripe patterns of up and down terraces, characteristic of Si(110)-“16 ×2”, are still visible. After annealing above 400°C, NiSi2 islands with (1 ×1) periodicity grow on the Si substrate showing various Ni-induced reconstructions. Detailed STM images of the surface of the islands have revealed that paired bright protrusions are randomly distributed on the (1 ×1) terrace. We have proposed a structural model where adjacent Si atoms in the NiSi2(110) surface form dimers in the [001] direction forming a (1 ×1) terrace, on which pairs of dimers are located at geometrically identical sites on the next grown NiSi2 layer.
Self-Organization of a Two-Dimensional Array of Gold Nanodots Encapsulated by Alkanethiol
Authors: Shujuan Huang Shujuan Huang , Hiroyuki Sakaue Hiroyuki Sakaue , Shoso Shingubara Shoso Shingubara , Takayuki Takahagi Takayuki Takahagi
Published: October 2002

We have studied a fabrication strategy for self-organization of a two-dimensional array of alkanethiol-encapsulated gold nanodots. The fabrication process has two steps: (1) preparation of alkanethiol-encapsulated gold particles from gold colloidal particles; (2) self-organization of an ordered close-packed array of gold nanodots encapsulated by alkanethiol on a substrate. By this method, we succeeded in fabricating a wide range of ordered close-packed monolayers of gold nanodots. The simplicity, flexibility, and practicality of this method makes it a prospective procedure for developing future nanoelectronic devices.
Characterization of Low-Pressure Chemical Vapor Deposited Polycrystalline Silicon Thin-Film Transistors by Low-Frequency Noise Measurements
Authors: Brini Charalabos A. Dimitriadis , Georges Kamarinos Georges Kamarinos , Gérard Ghibaudo Gérard Ghibaudo
Published: October 2002

Low-frequency noise measurements are used to characterize low-pressure chemical vapor deposited polycrystalline silicon thin-film transistors (polysilicon TFTs). The drain current spectral density shows a 1/f behavior at low frequencies (f<100 Hz), which is attributed to deep levels with uniform energy distribution, and a 1/f
γ behavior at high frequencies, which is due to the presence of exponential band tails. The origin of noise is ascribed to mobility and/or carrier number fluctuations depending on the polysilicon deposition pressure and the drain current range. For the analysis of noise data, a theoretical model is proposed. This model is based on an existing one for monocrystalline silicon metal-oxide-semiconductor field-effect transistors (MOSFET) modified by relating the carrier number fluctuations with dynamic trapping and detrapping at the interface grain boundary traps. From the analysis of experimental data, the deep level density and the exponential band tails are determined in polysilicon films deposited at various pressures.
Wavelength Effects in the Laser Cleaning Process
Authors: Lu Yong-Feng , Song Wen-Dong , Tee Chong-Kiat , Chan Daniel Siu-Hung , Low Teck-Seng
Published: October 2002

The wavelength effects in the laser cleaning process were studied both theoretically and experimentally. As the reflectivity and absorption coefficient depend on laser wavelength, different wavelengths will result in different temperature distributions in a particle or a substrate so that various cleaning forces and efficiencies are induced in the laser cleaning process. For laser-induced removal of copper and aluminum particles from quartz surfaces, the cleaning efficiency is higher and the threshold fluence is smaller for a shorter wavelength under the same cleaning parameters. This is because laser irradiation at a shorter wavelength causes a higher temperature rise and induces a greater cleaning force in a copper or aluminum particle, which results in higher cleaning efficiency and lower threshold fluence. The theoretical analysis can successfully predict and explain the experimental results.
A Novel and Convenient Method for Monitoring Processing Plasma: The Insulated Pulse Probe Method
Authors: Mikio Deguchi Mikio Deguchi , Ryohei Itatani Ryohei Itatani
Published: October 2002

The “insulated pulse probe method” is presented as a useful and convenient method suitable for monitoring plasmas for processing. This method is essentially stable against the change of the probe surface conditions and is free from the fatal problems particular to the conventional Langmuir probe method in reactive plasmas. In this method, the probe surface is originally covered with an insulating layer, and the time response of the probe current is measured on application of a square voltage pulse to the probe. The theoretical analysis on the response of the probe current is presented, and the electron temperature measured by this method in Ar plasma shows good agreement with that measured by the conventional Langmuir probe method. In addition, it is proposed that a silicon wafer under processing is usable as the probe to observe the plasma just in front of the wafer.
Photovoltaic Effects of Retinal-Related Materials in Langmuir-Blodgett Films
Authors: Okazaki Choichiro
Published: October 2002

Multilayer films consisting of retinal, retinoic acid, and retinol were fabricated using the Langmuir-Blodgett method. It was found for the first time that these three materials in Langmuir-Blodgett films exhibit different photovoltaic characteristics. To study this difference of photovoltaic characteristics, the surface pressure vs area isotherms of these materials were measured and the dipole moment of the materials were calculated.
InGaN/GaN/AlGaN-Based Laser Diodes Grown on GaN Substrates with a Fundamental Transverse Mode
Authors: Nakamura Shuji , Senoh Masayuki , Nagahama Shin-ichi , Iwasa Naruhito , Yamada Takao , Matsushita Toshio , Kiyoku Hiroyuki , Sugimoto Yasunobu , Kozaki Tokuya , Umemoto Hitoshi , Sano Masahiko , Chocho Kazuyuki
Published: October 2002

An InGaN multiquantum-well (MQW)-structure laser diode (LD) was grown on an
epitaxially laterally overgrown GaN on sapphire. The lowest threshold current densities
between 1.2 and 2.8 kA/cm2 were obtained when the number of InGaN well layers was two.
The InGaN MQW LD was grown on a free-standing GaN substrate that was obtained by
removing the sapphire substrate. The LDs with cleaved mirror facets showed an output power
as high as 30 mW under room-temperature continuous-wave (CW) operation. The stable
fundamental transverse mode was observed by reducing the ridge width to a value as small as
2 µm. The lifetime of the LDs at a constant output power of 5 mW was about 160 h under CW
operation at an ambient temperature of 50°C, due to a high threshold current density of
6 kA/cm2.
Characteristics of Cavity Round-Trip Time Pulses in Short-Cavity Q-Switched AlGaAs Multiple-Quantum-Well Semiconductor Lasers
Authors: Shimizu Mitsuaki , Suzuki Yoshihiro , Watanabe Masanobu
Published: October 2002

In the AlGaAs/GaAs two-section multiple-quantum-well (MQW)
laser system, Q-switched optical pulses whose width is shorter than the
cavity round-trip time were obtained by driving the gain section with 200 ps
electrical pulses. The pulse-width characteristics were measured while
varying the cavity length, and the optimum cavity length for obtaining the
shortest optical pulse was found. When the cavity length was 170–200 µm,
the shortest optical pulse with a width of 6–8 ps was obtained. We also
found a profile change in the second-harmonic-generation (SHG) auto-correlation
trace when the cavity length was changed.
The Generation of High-Density Microwave Plasma and Its Application to Large-Area Microcrystalline Silicon Thin Film Formation
Authors: Shirai Hajime , Arai Takeshi , Ueyama Hiroyuki
Published: October 2002

A low-temperature, uniform, and high-density microwave plasma (2.45 GHz) is produced utilizing a spokewise antenna with no use of magnetic field. The plasma maintains a uniform state in Ar low pressure of 10 mTorr with high electron density, >1011 cm-3, and temperature less than of 2.5 eV within ±6% over a 16 cm diameter. Highly crystallized, photoconductive, hydrogenated microcrystalline silicon, µc-Si:H film is produced from dichlorosilane (SiH2Cl2), H2 and Ar mixture at a high deposition rate of more than 5 Å/s. This plasma source has high potential not only for etching but also for the large-area film deposition processes.
Defect Analysis in Bonded and H + Split Silicon-on-Insulator Wafers by Photoluminescence Spectroscopy and Transmission Electron Microscopy
Authors: Michio Tajima Michio Tajima , Atsushi Ogura Atsushi Ogura , Tomoki Karasawa Tomoki Karasawa , Atsushi Mizoguchi Atsushi Mizoguchi
Published: October 2002

Defects in silicon-on-insulator wafers fabricated by bonding and H+
splitting technique
(Unibond wafers [Unibond is a registered trademark of SOITEC.]) were characterized by photoluminescence (PL)
spectroscopy
together with transmission electron microscopy (TEM).
PL from the superficial Si layer and that from the supporting substrate
were separately
analyzed using UV and visible light as an excitation source, respectively.
The deep-level PL band appeared around 0.8 eV both in the superficial
layer and the
substrate with a spectral shape similar to that often observed in oxygen
precipitated Si
crystals.
Correspondingly, TEM observation revealed precipitates and related
defects.
These results allow us to conclude that the defects in Unibond wafers originate in
oxygen precipitation during the two-step annealing in the wafer
fabrication process.
Detection of X-ray Induced Current Using a Scanning Tunneling Microscope and its Spatial Mapping for Elemental Analysis
Authors: Kouichi Tsuji Kouichi Tsuji , Yukio Hasegawa Yukio Hasegawa , Kazuaki Wagatsuma Kazuaki Wagatsuma , Toshio Sakurai Toshio Sakurai
Published: October 2002

By using an external X-ray source for photoemission,
an ultrahigh vacuum scanning tunneling microscope (UHV-STM)
was successfully used to detect and map a tip current
induced by X-ray irradiation simultaneously with a tunneling current. Apparent height in the
STM image rises by the X-ray induced current
on the Au/Cu(111) and Si(111)7×7 surfaces.
Relative height increase of the Au overlayer to Cu substrate
in STM images was found to depend on the X-ray irradiation,
suggesting that it may be a promising tool
for elemental analysis in STM.
Europium-152: A Novel and Economical Isotope for Use in Brachytherapy
Authors: Adelman Stuart Lee
Published: October 2002

Europium-152 is suggested as a nuclide of choice in hard-gamma brachytherapy. With a
broad spectrum of gamma energies falling 63% between 1.0 and 1.4 MeV, 27% at 0.344 MeV
and 37% at 0.122 MeV, an excellent distribution of isodose lines exists as a function
of distance from the longitudinal axis of the needle or tube. The half-life, 13.4y, of 152Eu
is desirably long, whilst its practical (and available) specific activity is easily greater than
1.85 TBq/g (∼50 Ci/g) of unenriched isotope. A stable oxide with a density of 4.4 g/cm3
assists encapsulation. The expected cost of europium needles compares favourably with
cæsium-137 and most favourably with iridium-192
Self-Ordering of Cell Configuration of Anodic Porous Alumina with Large-Size Pores in Phosphoric Acid Solution
Authors: Masuda Hideki , Yada Kouichi , Osaka Atsushi
Published: October 2002

Large cell-sized anodic porous alumina with long-range ordering was fabricated
using phosphoric acid solution. Self-ordering of the anodic alumina took place under
long-period constant voltage anodization at 195 V, which generated the self-ordered
anodic porous alumina with a cell size of 500 nm.
Deep Level Emission in ZnS Caused by Electron Beam Irradiation Studied by Cathodoluminescence Measurement System
Authors: Mitsui Tadashi , Yamamoto Naoki
Published: October 2002

The effect of electron beam irradiation on several emissions in ZnS films grown on GaAs (001) has been examined by a low-temperature
cathodoluminescence (CL) measurement system combined with a transmission electron microscope (TEM). It was found that the intensity of the
deep-level emission labeled “defect” increases during the electron beam irradiation while those of the other emissions decrease. This
suggests that the luminescence center of the “defect” emission act as the nonradiative centers for the others. These nonradiative centers
are most likely the point defects caused by electron beam irradiation.
Large Loop Current Induced Inside the Molecular Bridge
Authors: Shousuke Nakanishi Shousuke Nakanishi , Masaru Tsukada Masaru Tsukada
Published: October 2002

The noteworthy features of the current distribution
inside the molecular bridge structure are elucidated.
We consider the tight-binding model system with one orbital
per atom for the sake of simplicity.
The concept of the eigenchannel combined with the transfer matrix method
is developed for obtaining a transport view of
the quantum nature of the molecular bridge.
Eigenchannel decomposition is applied
not only to the transmission probability but also to the current distribution.
In some cases, a loop current induced by the source-drain current
is found at the ring part of the molecule.
The magnitude of the loop current can be much larger
than that of the source-drain current.
The condition for the appearance of this induced loop current
is also discussed.
Improved Stability of Metal-Insulator-Diamond Semiconductor Interface by Employing BaF2 Insulator Film
Authors: Tanaka Hiroyuki , Yun Young , Shirakawa Yusuke , Maki Tetsuro , Kobayashi Takeshi
Published: October 2002

Diamond metal-insulator-semiconductor (MIS) structures were fabricated by employing
various fluorides as gate insulator (MgF2, CaF2 and BaF2) and their electrical properties were
closely investigated by means of C-V measurements. The C-V characteristics of a
BaF2/diamond structure exhibited outstanding electrical properties (surface state density less
than 2×1010/(cm2·eV) near the valence band edge) as compared with the structures obtained
using other fluorides. From the chemiphysical point of view, the above result might be
explained as being due to the reduction of adsorbed-oxygen on the diamond surface via a
strong chemical reaction by the constituent Ba atoms in the insulator during the film
deposition.
Sublattice Reversal in GaAs/Si/GaAs (100) Heterostructures by Molecular Beam Epitaxy
Authors: Shinji Koh Shinji Koh , Takashi Kondo Takashi Kondo , Tetsuya Ishiwada Tetsuya Ishiwada , Chihiro Iwamoto Chihiro Iwamoto , Hideki Ichinose Hideki Ichinose , Hiroyuki Yaguchi Hiroyuki Yaguchi , Takanori Usami Takanori Usami , Yasuhiro Shiraki Yasuhiro Shiraki , andRyoichi Ito andRyoichi Ito
Published: October 2002

Sublattice reversal in III-V compound semiconductors grown on
group-IV epitaxial layers on III-V substrates has been proposed for
fabricating nonlinear optical devices with domain-inverted compound
semiconductor structures.
Sublattice reversal epitaxy is demonstrated in the GaAs/Si/GaAs (100)
system and confirmed by reflection high energy electron diffraction,
cross-sectional transmission electron microscopy, anisotropic etching,
and optical second-harmonic generation measurements.
The present sublattice reversal seems to be assisted by self
annihilation of antiphase domains generated at GaAs/Si interfaces.
Low Temperature High Electron Mobility in In0.75Ga0.25As/In0.75Al0.25As Modulation-Doped Hetrostructures Grown on GaAs Substrate
Authors: Gozu Shin-ichirou , Hong Chulun , Yamada Syoji
Published: October 2002

We have grown In0.75Ga0.25As/In0.75Al0.25As modulation-doped hetrostructure on GaAs
substrate via InAlAs step-graded buffer by molecular beam epitaxy and obtained electron
mobilities of 175,000 and 397,000 cm2/V·s at 77 and 4.2 K respectively, those of which
are the highest ones ever reported in this materials system. Comparing the results with
those of In0.75Ga0.25As/In0.66A0.34As and In0.5Ga0.5As/In0.5Al0.5As heterostructures grown
similarly, it is concluded that the high mobility was attained due to the reduced alloy
scattering under the strain-free interface condition and to the reduced electron effective
mass (0.040m
0 from far-infrared measurement).
Confinement of Nonneutral Plasmas in a Trap Composed of a Cusped Magnetic Field and an Electrostatic Octapole Field
Authors: Akihiro Mohri Akihiro Mohri , Tetsumori Yuyama Tetsumori Yuyama , Yasuhito Kiwamoto Yasuhito Kiwamoto , Yohei Yamazawa Yohei Yamazawa , Toshinori Michishita Toshinori Michishita
Published: October 2002

The field configuration formed by the superposition of a cusped
magnetic field and an electrostatic octapole field provides a closed
system of confinement for a charged particle. In a cusped magnetic
field, the Störmer region which constrains a charged particle is
open, but it is closed by adding a potential barrier made by the
octapole field. One-component plasmas are thus expected to be
confined in this configuration, preserving superior characteristics
of the cusp field for plasma stability. A preliminary experiment was performed on the confinement of electrons in this
field configuration. An electron plasma was confined
for 3 s in a magnetic field as weak as B=50 G at the
circular line cusp. The confinement time was roughly proportional
to B
2, suggesting that the confinement would be improved substantially in
a higher magnetic field.
Temperature and Applied Voltage Dependence of Magnetoresistance Ratio in Fe/Al oxide/Fe Junctions
Authors: Nobuki Tezuka Nobuki Tezuka , Terunobu Miyazaki Terunobu Miyazaki
Published: October 2002

The tunnel magnetoresistance(TMR) ratio have been investigated in the Fe/Al oxide/Fe junctions, specifically the temperature and applied voltage dependence of the TMR ratio. It was found that the dependence of resistance at saturation magnetization state(R

s
) on the applied voltage at 4.2 K is completely anomalous in terms of the expected tunneling behavior. This “zero-bias anomaly" is due to the magnetic impurity in or near the boundary between ferromagnetic electrodes and insulator. The TMR ratio decreased rapidly with increasing temperature. The TMR ratio also decreased when increasing the applied voltage. We discussed the dependence of the TMR ratio on temperature and applied voltage taking into account the impurity assisted tunneling.
Formation Energy of Interstitial Si in Au-Doped Si Determined by Optical Absorption Measurements of H Bound to Interstitial Si
Authors: Suezawa Masashi
Published: October 2002

We determined the formation energy of interstitial Si in Au-doped Si from the measurements of optical absorption due to hydrogen (H) bound to interstitial Si. Si crystals were doped with Au by a vapor method; namely, specimens were sealed in quartz capsules together with a piece of Au wire and then annealed at high temperature followed by quenching in water. Then the specimens were doped with H by annealing them in hydrogen atmosphere of 1 atm. followed by quenching. We measured optical absorption of those specimens after quenching from various temperatures. From the temperature dependence of the 2223 cm-1 line identified as being due to H bound to interstitial Si, the formation energy of interstitial Si in Au-doped Si was determined to be about 2.1 eV.
Electron Counting Monte Carlo Simulation of the Structural Change of the GaAs(001)-c(4×4) Surface during Ga Predeposition
Authors: Ito Tomonori , Shiraishi Kenji
Published: October 2002

An electron counting Monte Carlo (ECMC) simulation is performed to investigate the structural change of As-rich GaAs(001)-c(4×4) surfaces during Ga predeposition, incorporating the As desorption process as a function of Ga adatom coverage based on ab initio calculations. The ECMC simulation results indicate that predepositing 0.5 monolayers of Ga on the GaAs(001)-c(4×4) surface induces As desorption and reduces effective As coverage θAs to 1.25, where four Ga dimers and two As dimers co-exist in the (4×4) surface unit cell used in this simulation. Subsequent equilibration of this surface changes its structure to (2×4)-like surface with θAs=0.75 and one As-dimer row and three missing As-dimer rows. These simulated results successfully give one possible interpretation to some puzzling questions in experimental results.
Formation of High Quality Tantalum Oxide Thin Films at 400°C by 172 nm Radiation
Authors: Zhang Jun-Ying , Bie Li-Jian , Boyd Ian W.
Published: October 2002

Thin uniform tantalum oxide films on Si were formed at 400°C using photo-assisted sol-gel process from a Xe2
* excimer lamp. Carbon contamination levels as low as 2.0 at% were obtained which compare favourably with the levels found (4–7%) by alternative techniques. Ellipsometry, electron probe X-ray microanalysis, capacitance-voltage, and current-voltage measurements were employed to characterise the films whose overall properties are found to be superior to those for Chemical Vapor Deposition (CVD) deposited films. Leakage current densities as low as 9.0×10-8 A·cm-2 at 0.5 MV/cm are obtained for the as-prepared films, several orders of magnitude lower than for any other as-grown films prepared by any other technique. A subsequent low temperature (400°C) annealing improves this to 2.0×10-9 A·cm-2 at 0.5 MV/cm. These values are essentially identical to those only previously formed for films annealed at temperatures between 600 and 1000°C.
Tunable Ultraviolet Short-Pulse Generation from a Ce:LiCAF Laser Amplifier System and Its Sum-Frequency Mixing with an Nd:YAG Laser
Authors: Liu Zhenlin , Sarukura Nobuhiko , Dubinskii Mark A. , Semashko Vadim V. , Naumov Alexander K. , Korableva Stella L. , Abdulsabirov Ravil Yu.
Published: October 2002

We developed an all-solid-state tunable short-pulse ultraviolet master oscillator and power amplifier (MOPA) system employing Ce3+:LiCaAlF6 (Ce:LiCAF) which can be pumped by the fourth harmonic of a Q-switched Nd:YAG laser. The demonstrated tuning range was 281 nm to 314 nm with the maximum output energy of 1 mJ from the oscillator maintaining short pulse characteristics. The maximum amplified pulse energy was 4 mJ after the double-pass amplifier. The tuning from 223 nm to 232 nm was realized by the sum-frequency-mixing of the Ce:LiCAF laser and the Q-sw Nd:YAG laser.
Electron Scattering Rates in AlGaN/GaN Quantum Wells for 1.55-µm Inter-Subband Transition
Authors: Suzuki Nobuo , Iizuka Norio
Published: October 2002

Electron scattering rates in AlGaN/GaN QWs for the 1.55-µm inter-subband transition at room temperature are calculated. The inter-subband scattering time, which is dominated by the longitudinal optical (LO) phonon scattering, is as short as about 100 fs. The intra-subband LO-phonon scattering rate, the electron-electron scattering rate, and the ionized impurity scattering rate are greater than those in (In)GaAs QWs. This causes a short dephasing time of about 10 fs, which reduces the peak value of the third-order nonlinear susceptibility but broadens its spectral width. Even if the band nonparabolicity is taken into consideration, ultrafast response of the inter-subband optical nonlinearity in GaN QWs is little affected by the delay in intra-subband energy relaxation caused by non-equilibrium phonons.
Observation of Vortex Movements in a Bi2212 Single Crystal under Application of a Transport Current by means of the Bitter Pattern Technique
Authors: Ohshima Shigetoshi , Koseki Takahiro , Kamimura Akira
Published: October 2002

The high-resolution Bitter pattern technique has been used to observe vortex movements of Bi2Sr2CaCu2Oy single crystals. A transport current is applied to the sample parallel to the ab plane, and a dc magnetic field is applied normal to the ab plane at the Ni decoration. The Ni decoration pattern can be observed using a scanning electron microscope (SEM) and an atomic force microscope (AFM). Through observation of the Ni pattern, we can identify vortex movements while the transport current is being applied. The vortices move randomly with a small transport current of less than 40% of J
c, and they move in a line with a large transport current nearly equal to J
c. The vortex movement was not observed in the sample on applying a transport current larger than 1.5 J
c.
Effect of Ultra-Clean Sputtering on Magnetoresistance and Thermal Stability of Magnetoresistance in Spin-Valves
Authors: Hayashi Kazuhiko , Nakada Masafumi , Kamijo Atsushi , Fujikata Jun-ichi , Yamada Kazuhiko
Published: October 2002

The influence of the base pressure (8.6×10-10–1.3×10-7 Torr) in the sputtering chamber just before the deposition on the magnetoresistance (MR) ratios and the thermal stability of the MR ratios in spin-valves (SVs) was studied, using purified sputtering Ar gas (impurity level less than 1 ppb). The resistivity ρ in the SVs decreased and as a result, the MR ratio increased with decreasing base pressure. Also, the thermal stability of the MR ratio was improved with decreasing base pressure. The increase of grain size in the SVs fabricated under low base pressures bears a close relationship to the MR ratios and the thermal stability of the MR ratios.
Investigations of a Rapid Thermal Annealed Al0.15Ga0.85As/Si Structure
Authors: Saravanan Shanmugam , Arokiaraj Jesudoss , Jimbo Takashi , Soga Tetsuo , Umeno Masayoshi
Published: October 2002

Al0.15Ga0.85As/Si grown by metalorganic chemical vapor deposition (MOCVD) was
subjected to rapid thermal annealing (RTA) and investigated by photoluminescence (PL),
scanning electron microscopy (SEM), Auger electron spectroscopy (AES), secondary ion mass
spectrometry (SIMS) and double crystal X-ray diffraction (XRD) measurements. After RTA at
850°C for 10 s the PL intensity increased significantly. Above 900°C, quenching of PL
intensity was observed. An emission at 1.515 eV was observed only in 900 and 950°C
annealed samples and is attributed to the formation of a Si-related complex defect. AES and
SIMS measurements revealed the diffusion of Si at higher annealing temperatures from the top
surface into the epilayer and this diffusion is accounted for by a gas phase reaction. Double-crystal XRD showed a decreasing full width at half maximum (FWHM) value as the annealing
temperature was increased.
Erasable Phase Change Disks with Super Resolution Capability by Pulse-Readout
Authors: Liu Jia-Reuy , Shieh Han-Ping David
Published: October 2002

Erasable thermal phase change super resolution (EPSR) disks composed of mask and
recording layers can be fabricated with a “below-diffraction-limited” aperture within the readout
spot to achieve optical super resolution. The formation of the aperture and the readout signal on
the EPSR disk were analyzed. The feasibility of the designed EPSR disks was evaluated by thermal
simulation. A carrier-to-noise-ratio (CNR) of 32 dB at mark size of 0.4 µm, 8 dB higher than that
in a conventional disk, was obtained by applying pulse-readout to the EPSR disks at a wavelength
of 780 nm and numerical aperture of 0.55.
Continuous Versus Limited Smectic Liquid Crystal Layer Rotation
Authors: Dierking Ingo , Komitov Lachezar , Lagerwall Sven T.
Published: October 2002

The in-plane reorientation of smectic layers of ferroelectric smectic C* liquid crystals, enclosed in
sandwich cells, can be continuous or limited to twice the molecular tilt angle, depending on the
surface treatment of the substrates. We have identified the imposing of a preferred direction of
alignment through unidirectional rubbing to be responsible for the limitation of the smectic layer
reorientation. As soon as the monostable boundary conditions are changed to degenerate planar
anchoring (no preferred alignment direction) the limited layer reorientation transforms into a
continuous one.
Preparation of Langmuir-Blodgett Films Containing a Charge-Transfer Complex of Alkylated Dicyanoquinonediimine (DCNQI) and Copper
Authors: Ikegami Keiichi , Nakamura Takayoshi
Published: October 2002

An alkylated N,N
′-dicyanoquinonediimine (alkylDCNQI) derivative has
been synthesized and the Langmuir-Blodgett (LB) technique has been applied to
this material and its mixture with CuI, aiming at the construction of a DCNQI-Cu
system in two dimensions. No chemical reaction could be detected for
alkylDCNQI-CuI mixed solutions. However, optical measurements have shown
that the LB films obtained from the mixture contain a partially reduced DCNQI
group, suggesting that a new CT complex is obtained by in situ reaction of
alkylDCNQI and CuI at the air-water interface.
On In-plane Smectic Layer Reorientation in Ferroelectric Liquid Crystal Cells
Authors: Dierking Ingo , Komitov Lachezar , Lagerwall Sven T.
Published: October 2002

We report the results of a systematic investigation of the process of smectic layer reorientation of a ferroelectric liquid crystal on the application of asymmetric electric fields. In contrast to previous reports, we observed a reversible smectic layer rotation in the plane of the substrate, limited by the amount of the director tilt angle, particularly also for asymmetric rectangular waveforms. We discuss the behaviour of a variation of external parameters, such as field asymmetry, electric field amplitude, frequency, cell gap and temperature in terms of the dominant influences of -liquid crystal substrate interactions, director switching including the electroclinic effect and electro-convective effects which provides a qualitative description of the smectic layer rotation.
0.66 µm InGaP/InGaAlP Single Quantum Well Microdisk Lasers
Authors: Pan Jin Shan , Cheng Po Hsiu , Lee Tsin Dong , Lai Yinchieh , Tai Kuochou
Published: October 2002

Visible emitting microdisk lasers with single InGaP/InGaAlP quantum well were
demonstrated for the first time. Large spontaneous emission factors β of 0.12 and 0.08
were observed for 5 and 10 µm diameter disks, respectively.
Significant Improvement in Ba 1-xKxBiO 3 Grain Boundary Junctions on MgO Bicrystal Substrates by Minimal BaBiO 3 Sputtering
Authors: Yukihiko Wada Yukihiko Wada , Tetsuya Takami Tetsuya Takami , Ken'ichi Kuroda andTatsuo Ozeki Ken'ichi Kuroda andTatsuo Ozeki
Published: October 2002

High quality Ba1-x
KxBiO3 (BKBO) artificial grain boundary junctions
were fabricated on MgO (100) bicrystal substrates. We found that extremely-short-time
sputtering of BaBiO3 (BBO) onto MgO substrate prior to BKBO deposition results in a
marked improvement in the quality of the BKBO film. Utilizing this technique, a
junction with J
c=6 kA/cm2 and ΔV
g≈1 mV at 4.2 K
was fabricated. In addition, a junction with a high critical current density of
J
c=78 kA/cm2 was obtained.
Ultrahigh Resolution in Sputter Depth Profiling with Auger Electron Spectroscopy Using Ionized SF6 Molecules as Primary Ions
Authors: Hofmann Siegfried , Rar Andrei
Published: October 2002

Depth profiling studies with Auger electron spectroscopy (AES) on a GaAs/AlAs
multilayer structure using different sputtering gases (Ar, Xe, SF6), ion energies of 500,
750 and 1000 eV and ion incidence angles of 70 and 85 deg show that ultrahigh depth
resolution with Δz=1.6 nm is obtained for SF6 at 500 eV and 85 deg. Application of the
mixing-roughness-information depth (MRI) model for quantitative profile evaluation
reveals the various contributions of atomic mixing, roughness and information depth to
the depth resolution. Although under optimum conditions the roughness is still
predominant with an rms value of 0.7 nm, a record low value of 0.4 nm was found for
the mixing zone length. This correponds to less than two monolayers and opens the way
to layer-by-layer sputtering without atomic mixing.
Generation and Detection of Squeezed Light with Phase Tunable Fiber Loop Mirror using Polarization Beam Splitter
Authors: Norihiko Nishizawa Norihiko Nishizawa , Masaki Hashiura Masaki Hashiura , Takeo Horio Takeo Horio , Masakazu Mori Masakazu Mori , Toshio Goto Toshio Goto , Kazuo Yamane Kazuo Yamane
Published: October 2002

Squeezed light generation is demonstrated using a new scheme of nonlinear
fiber loop mirror.
The squeezed light can be generated stably in a compact setup
and the phase difference can be changed arbitrarily.
Using a 100 ps mode-locked pulse laser at 1.064 µm and 0.85 µm
single-mode fiber, the quantum noise reduction of 2.0 dB below the shot noise level
is observed in the frequency range of 25–35 MHz.
Accounting for the detection efficiency, this corresponds to 2.9 dB squeezing.
Hydrothermal Transformation of Gel Pb(Zr0.52, Ti0.48)O3 Thin Films into Perovskite Phase at Low Temperature of 160°C
Authors: Xu Huaping , Kiyomoto Tomofumi , Morikawa Yasuomi , Okuyama Masanori , Lin Chenglu
Published: October 2002

Lead-zirconate-titanate (PZT) films with perovskite structure have been synthesized using a novel
soft-chemistry method that involved use of a sol-gel method followed by a subsequent
hydrothermal treatment. Both pyrolyzed and unpyrolyzed Pb(Zr0.52, Ti0.48)O3 films prepared using
sol-gel method were chosen as the precursor films for hydrothermal treatment. Structural
characteristics proved that the films were transformed from their amorphous precursor phase to
the crystallized perovskite phase and were found to grow from the surface to the underneath layer.
Anomalous Gate Length Dependence of Threshold Voltage of Trench-Isolated Metal Oxide Semiconductor Field Effect Transistors
Authors: Oishi Toshiyuki , Shiozawa Katsuomi , Furukawa Akihiko , Abe Yuji , Tokuda Yasunori
Published: October 2002

We investigate the influence of trench isolation edges on metal oxide
semiconductor field effect transistors (MOSFETs) by comparison with the
characteristics of a reference transistor with no isolation edge. The result
indicates that the gate length (L) dependence of the threshold voltage (V
th) is
remarkably modified by an electric field concentration at the channel edge. The
anomalous V
th behavior is explained in terms of the mixing between the short
and narrow channel effects, by a qualitative three-dimensional analysis.
Generation of cw-Terahertz Radiation Using a Two-Longitudinal-Mode Laser Diode
Authors: Ping Gu Ping Gu , Masahiko Tani Masahiko Tani , Masaharu Hyodo Masaharu Hyodo , Kiyomi Sakai Kiyomi Sakai , Takehiro Hidaka Takehiro Hidaka
Published: October 2002

Coherent cw-terahertz (THz) radiation has been generated by photomixing with a photoconductive antenna fabricated on a
low-temperature-grown (LTG) GaAs film using a two-longitudinal-mode distributed Bragg reflector (DBR) laser diode (LD).
The frequency of the emitted radiation corresponds to the difference frequency between the two modes of the LD. The linewidth
of the radiation is much narrower than that of each laser mode oscillating in the same cavity due to the common-mode rejection
effect between the two modes oscillating in the same cavity. This property of the two-mode LD, as well as its compactness and
ease of optical alignment, make the device promising as an excitation laser source for photomixing.
Structural and Energy-Gap Characterization of Metalorganic-Vapor-Phase-Epitaxy-Grown InAsBi
Authors: Okamoto Hiroshi , Oe Kunishige
Published: October 2002

The structural properties and energy-gap dependence on InBi content and temperature are investigated for metalorganic-vapor-phase-epitaxy (MOVPE)-grown InAsBi. All measurement results-X-ray-diffraction, secondary ion mass spectroscopy (SIMS), and Rutherford-backscattering-spectroscopy (RBS) channeling-show that the layer has good crystalline quality. The energy-gap dependence on InBi content is evaluated by optical-transmission and low-temperature photo luminescence, and it is shown that the dependence can be expressed by a linear equation. The temperature dependence of E
g (ΔE
g/ΔT) is evaluated by optical-transmission measurement. The ΔE
g/ΔT of 0.22 meV/K obtained for InAs0.963Bi0.037 is smaller than that of InSb (0.29 meV/K), whose energy gap is smaller than that of InAs0.963Bi0.037.
Aerosol Fabrication of Nanocrystals of InP
Authors: Deppert Knut , Bovin Jan-Olov , Magnusson Martin H. , Malm Jan-Olle , Svensson Chatrin , Samuelson Lars
Published: October 2002

Nanocrystals of indium phosphide, with diameters of around 10 nm, have been produced via an aerosol route. The method is based on the formation of monodisperse indium droplets and the subsequent reaction with phosphine at elevated temperature. The size of the final InP nanocrystal is self-limited by the size of the introduced size-selected In droplet. This size can be tuned carefully, thus this method allows a narrow size distribution of the nanocrystals. The kinetics of the reaction of In to produce InP depends on the temperature and the phosphine flow. Extensive high resolution transmission electron microscopy studies lead to a consistent picture of the process. Our approach opens the possibility for efficient production of size-selected semiconductor nanocrystals and it will allow new types of self-assembly and control of quantum dots.
Nanoscale ErP Islands on InP(001) Substrate Grown by Organometallic Vapor-Phase Epitaxy
Authors: Leonid Bolotov Leonid Bolotov , Takahiro Tsuchiya Takahiro Tsuchiya , Takashi Ito Takashi Ito , Yasufumi Fujiwara Yasufumi Fujiwara , Yoshikazu Takeda Yoshikazu Takeda , Arao Nakamura Arao Nakamura
Published: October 2002

We have investigated nanoscale ErP islands formed on InP(001) during Er exposure in organometallic vapor-phase epitaxial growth by means of atomic force microscopy and scanning tunneling microscopy. Different features of surface morphologies are observed depending on the growth temperature and the ErP coverage. The generation of misfit dislocation arrays along the [1\bar0] direction leads to anisotropic strain relaxation that originates from the anisotropy of the atomic bonds at the interface. The residual strain of partially relaxed islands is ∼2% for growth at 530°C, which corresponds to the minimum of total areal energy of the strained film. Current imaging tunneling spectroscopy shows a high tunnel current at dislocations and ErP island edges suggesting the existence of high-density surface states near the Fermi level and the decrease in tunneling barrier height.