bluuebunny/crossref_metadata_2025 huggingface dataset:
Evidence for Phosphorus Passivation of Plasma-Induced Damage at GaAs Surface Probed by EL2 Traps
Authors: Sugino Takashi , Yamada Takashi , Matsuda Koichiro , Shirafuji Junji
Published: February 2005

Change in EL2 density in the GaAs surface layer treated with H2 plasma and phosphine (PH3)-added H2 plasma has been investigated by means of deep level transient spectroscopy (DLTS) and isothermal capacitance transient spectroscopy (ICTS). Apparent reduction in the EL2 density occurs on the H2-plasma-treated GaAs surface in comparison with that on the untreated one, because of H passivation of EL2 centers. However, an annealing at 350°C for 3 min after the H2-plasma exposure leads to a remarkable increase of EL2 density on the surface, showing net introduction of EL2 centers during the plasma exposure. On the other hand, the generation of EL2 centers is suppressed when the surface is treated with the PH3-added plasma.
Evaluation of LaB6 Thin Film as Low-Work-Function Gate for MOSFET Operated at Low Temperature
Authors: Yokoyama Michio , Yi You-Wen , Masu Kazuya , Tsubouchi Kazuo , Mikoshiba Nobuo
Published: February 2005

The work function of LaB6 thin film has been evaluated from the LaB6/SiO2/Si metal-oxide-semiconductor (MOS) structure. Thermally stable MOS diodes with LaB6 gate were fabricated. From capacitance-voltage characteristics of MOS diodes, the work function of LaB6 film was found to be 3.5 eV. This result shows that LaB6 is a very promising candidate for a gate material of depletion MOSFET operated at low temperature without carrier freeze-out.
Property and Structure of YBa2Cu3Ox-Ag Composites Prepared from Nitrate Solutions
Authors: Hikichi Yasuo , Kato Makoto , Suzuki Suguru , Nomura Tsuyoshi , Miyamoto Masaaki
Published: February 2005

Mixtures of Y, Ba, Cu, and Ag nitrate aqueous solutions (nominal molten ratio of Y:Ba:Cu=1:2:3) were evaporated to dryness. The dried powders were codecomposed at 850°C in air, and sintered at 920°C for 20 h in O2. The phases were only orthorhombic YBa2Cu3O
x
and Ag. The bulk density, grain size, and critical current density (J
c) increased with increasing amount of Ag≦5 wt%: for instance, up to 5.65 g/cm3, 30 µm, and 215 A/cm2, respectively. The critical temperature (T
c(zero)) was about 91 K (with a width of 1–2 K) and insensitive to the amount of Ag≦5%. With addition of Ag, the degradation in moisture was improved.
Substituting Effect of Bi on Superconductor YBa2Cu3O7-y
Authors: Nagata Shoichi , Ikeda Toshimi , Nakajima Mikio , Chikazawa Susumu
Published: February 2005

Substitution of a small amount of bismuth for yttrium in Y1-x
Bi
x
Ba2Cu3O7-y
leads to a decomposition into more than two phases even at a low bismuth content of x=0.02. Experimental results of resistivity measurements and X-ray powder diffraction analysis are reported with emphasis on the low bismuth content. The resistivity exhibits rather complicated sample-dependent behavior for x larger than 0.02, reflecting the decomposition due to the substitution of bismuth.
Superstructure in Thin Films of Bi-Based Compounds on MgO
Authors: Kojima Kazuyoshi , Schlom Darrell G. , Kuroda Ken'ichi , Tanioku Masami , Hamanaka Koichi , Eckstein James N. , Harris James S. , Jr. Jr.
Published: February 2005

In situ epitaxial growth of BiSrCaCuO films by three target sputtering was performed on MgO substrates at a temperature of 650°C. From high resolution transmission electron microscopy, the film showed a superstructure consisting of the alternate stacking of the low-T
c and high-T
c phases with a c-axis of 34 Å. The film in the [110] or [1 1̄0] directions was parallel to <100 >MgO, and the transient layers between the substrate and the film were less than a few atomic layers thick. X-ray diffraction simulations indicated that the films contained random layer ordering of 34 Å bi-layers (low-T
c+high-T
c and high-T
c+low-T
c) and random layer ordering of low-T
c and high-T
c phase layers.
Fluorine Doping and Superconductivity of Nd2CuO4 Thin Films
Authors: Koinuma Hideomi , Takeuchi Kou , Yoshimoto Mamoru , Hashida Kenji , Nakabayashi Masaaki , Gonda Satoshi , Hirayama Tohru , Shiraishi Tadashi
Published: February 2005

Fluorine was doped into sputter-deposited Nd2CuO4 films to induce superconductivity in the films. The films annealed in the presence of NF3 gas were observed to show remarkable resistivity change which was in parallel with the change of a-axis length. Fluorine incorporation in the films was verified by the X-ray photoelectron spectroscopy analysis. The specimen annealed at 800°C in 0.1 Torr NF3(1%)/Ar gas under UV light irradiation exhibited the onset of superconductivity at 27 K after a reducing procedure at 700°C in Ar.
Experimental Analysis of YBa2Cu3Ox/Ag Proximity Interfaces
Authors: Fujimaki Akira , Tamaoki Tomohiro , Hidaka Tetsuya , Yanagase Masashi , Shiota Tetsuyoshi , Takai Yoshiaki , Hayakawa Hisao
Published: February 2005

We have fabricated SNS (superconductor-normal metal-superconductor) junctions consisting of YBa2Cu3O
x
(YBCO)/Ag/Nb trilayers in order to probe surface properties of the YBCO films. The trilayers are in situ deposited, and patterned by a photolithographic technique. These junctions exhibit Josephson-like behavior. The contact resistivity and its temperature dependence suggest that the weaklinks are formed inside YBCO and that the junction properties depend on the area of surface non-superconducting phases consisting of the YBCO components.
Optical and Electrical Logic Operations by a Liquid Crystal Bistable Optical Device
Authors: Nose Toshiaki , Sato Susumu
Published: February 2005

A liquid crystal bistable optical device (LCBOD) with internal optical feedback is prepared using a twisted nematic (TN) liquid crystal cell, a photoconductive (CdS) cell and a polarizing film. Its picture elements are arranged in a 3×5 matrix structure, and the bistable properties are measured as a function of optical input and electrical input. Then two-dimensional logic operations are demonstrated.
Control of Pretilt Angles of Liquid Crystal Molecules in a Liquid Crystal Cell Using a Chemically Adsorbed Monolayer as an Alignment Film
Authors: Ogawa Kazufumi , Mino Norihisa , Nakajima Keizo
Published: February 2005

Using chemically adsorbed monolayers with two surfactants as an alignment film for a liquid crystal cell, liquid crystal cells were structured. The monolayers showed a fair degree of alignment effects without rubbing. By changing the composition ratio of the mixture of the surfactants having a long hydrocarbon chain and a short hydrocarbon chain, the pretilt angles of the liquid crystal molecules could be controlled. The molecular density or the molecular arrangements in the chemically adsorbed monolayers may strongly affect the pretilt angles. To interpret the experimental results, possible model structures in the monolayer were proposed.
A Dye Laser Spectrometer with an External Iodine Cell Designed for Optical Ramsey-Fringe Spectroscopy in a Ca Atomic Beam
Authors: Morinaga Atsuo , Ito Nobuhiko , Sugiyama Kazuhiko
Published: February 2005

A novel dye laser spectrometer stabilized to a hyperfine component of molecular iodine as a frequency reference was developed for observing optical Ramsey fringes in a Ca atomic beam. The resolution of the spectrometer was less than 1 kHz and the uncertainty of the absolute frequency was within 20 kHz. By using this spectrometer, Ramsey fringes with a width of 10 kHz and a signal-to-noise ratio of 200 were obtained with an integration time of 5 ms. The frequency separation between lines of Ca (1S0-3P1) and I2. (g, 3–4, R(67)) was measured to be 191.48±0.02 MHz.
On-Chip Bottom-Gate Polysilicon and Amorphous Silicon Thin-Film Transistors Using Excimer Laser Annealing
Authors: Shimizu Kazuhiro , Sugiura Osamu , Matsumura Masakiyo
Published: February 2005

High-performance bottom-gate thin-film transistors (TFTs) with both polysilicon (poly-Si) and amorphous silicon (a-Si) have been fabricated, for the first time, using chemical-vapor-deposited a-Si film as a starting semiconductor material. The feature of this technology is that both TFTs can be produced in the same process and at the same time on a single substrate except for the local laser crystallization step of the a-Si. The field-effect mobilities were 60 cm2/V ·s for the poly-Si TFT and 1.3 cm2/V ·s for the a-Si TFT, respectively. Their on-off current ratios were more than 106.
Existence of Superconducting States Above 30 K in Sr-V-O Systems Doped with Various Elements
Authors: Matsuda Shin-Pei , Takeuchi Seiji , Soeta Atsuko , Doi Toshiya , Aihara Katsuzou , Kamo Tomoichi
Published: February 2005

Electrical properties of the Sr-V-O systems doped with Tl, La, and Ce were extensively studied. The Sr-V-O system was prepared in the reduced form, for example, SrVO3-δ, and was doped with Tl. In the Tl-Sr-V-O system a sharp drop in the resistivity was observed at around 30 and 130 K in several samples. A diamagnetic signal was clearly observed below 30 K. The superconducting states of the Tl-Sr-V-O system are found to be metastable in the ambient atmosphere. It is suggested that there are at least two superconducting phases or crystal structures giving rise to the T
c's. The highest onset temperature observed for the sharp resistivity drop was 160 K.
Effect of High-Energy Ion Irradiation on Current-Voltage Characteristics in the Oxide Superconductor YBa2Cu3O7-x
Authors: Iwase Akihiro , Masaki Norio , Iwata Tadao , Nihira Takeshi
Published: February 2005

The effect of 120 MeV 16O ion irradiation on the current-voltage (I-V) characteristics in YBa2Cu3O7-x
is examined at 77.3 K. Both the I-V characteristics and the dependence of V on the ion fluence \varPhi are found to show similar power-law behaviors in the form of V∝I

a
for small current and V∝\varPhi
b
, respectively. The experimental result is discussed in terms of current-induced unbinding of thermally excited vortex pairs.
Preparation of Bi Iron Garnet Film with a Two-Step Growth Technique
Authors: Mino Shinji , Matsuoka Morito , Shibukawa Atsushi , Ono Ken'ichi
Published: February 2005

Completely Bi-substituted iron garnet (Bi3Fe5O12, BiIG) film with a smooth surface is synthesized by electron cyclotron resonance (ECR) sputtering using a two-step growth technique. Consequently, the waveguide propagation loss of BiIG film at a wavelength of 1.55 µm can be measured. The surface smoothness and the propagation loss can be improved with a buffer layer as thin as 2 nm, as the growth temperature T
b (400°C≤T
b≤600°C) is increased. This shows that buffer layer crystallinity plays an important role in making the BiIG film surface smooth and the propagation loss low.
Influences on Director Alignment of the Lateral Bus-Line Field in an Active-Matrix-Addressed Liquid Crystal Display
Authors: Onozawa Tatsuo
Published: February 2005

By a two-dimensional numerical simulation for an active-matrix-addressed liquid crystal display, the lateral field effect has been studied. Potential and director distributions have been investigated in detail. It has been shown that a reverse tilt region extends at a gate bus-line side in a pixel and that optical transmission exhibits abnormal behavior on its boundary with the normal tilt region far from an edge.
1/f Spike Discharge Interval Fluctuations of DOPH Millipore Membrane
Authors: Akabane Akabane , Hideo Hideo , Musha Musha , Toshimitsu Toshimitsu
Published: February 2005

A Millipore filter whose pores are filled with dioleyl phosphate molecules exhibits self-oscillation of electric potential when it separates KCl solutions of 5 mM and 100 mM and a dc potential difference is applied across it. Self-oscillation intervals are found to have a 1/f spectrum, and the power spectral density of fractional interval variation is given by S
δT/(f)=3×10-4/f.
Low-Temperature Heat Capacity of Cubic Boron Nitride
Authors: Atake Tooru , Honda Akio , Saito Yasutoshi , Saito Kazuya
Published: February 2005

Heat capacities of cubic boron nitride (c-BN) and synthetic diamond were measured between 10 and 300 K by adiabatic calorimetry. A difference between the heat capacity values of two substances was observed. Discussion was made concerning the lattice vibrational property of c-BN and diamond crystals.
Effect of the Beam Shape in Pseudoline Electron Beam Recrystallization
Authors: Ishiwara Hiroshi , Fukao Kazuichi
Published: February 2005

We investigated the shape of a spot beam which forms a pseudoline electron beam in the recrystallization of SOI (silicon-on-insulator) films. It was found that the recrystallization characteristics were strongly dependent on the shape of the spot beam. Under the optimized shape, 3×3 SOI patterns of 100 µm square were recrystallized in almost subboundary-free condition.
Preparation of C-Axis-Oriented PLT Thin Films by the Metalorganic Chemical Vapor Deposition Method
Authors: Tominaga Koji , Miyajima Masaki , Sakashita Yukio , Segawa Hideo , Okada Masaru
Published: February 2005

La-modified lead titanate (PLT) thin films are prepared by the metalorganic chemical vapor deposition method. Tetraethyl lead, titanium tetraisopropoxide and trisdipivaloylmethanato lanthanum are used as source materials. The films obtained at 600°C under reduced pressure of 6 Torr constitute PLT of the single perovskite phase, and highly c-axis-oriented films are grown on MgO(100). The crystal structures are transferred from the tetragonal to the cubic structure with increasing molar fraction of La2O3. The dielectric constant and tan
δ are around 800 to 2700 and 0.04 to 0.1.
In Situ Analysis of Gallium Arsenide Surfaces by Coaxial Impact Collision Ion-Scattering Spectroscopy with an Off-Axis Ion Source
Authors: Sugiyama Naoharu , Hashimoto Akihiro , Tamura Masao
Published: February 2005

A novel coaxial impact collision ion-scattering spectroscopy system with an off-axis ion source has been designed and constructed. By inserting a deflecting electrode in the primary ion-beam line, the ion source was arranged on the off-axis position of the line connecting the target and the detector. This configuration has resulted in high-resolution mass analysis and a high counting rate. This system has been applied to an in situ analysis of molecular beam epitaxial surfaces. It was found that signals scattered by Ga atoms and those by As atoms could be separately detected within the sensitivity of one monolayer GaAs on an AlAs layer and within a sampling depth of 2∼3 monolayers.
Plasma Etching of ITO Thin Films Using a CH4/H2 Gas Mixture
Authors: Mohri Mikio , Kakinuma Hiroaki , Sakamoto Masaaki , Sawai Hideo
Published: February 2005

Plasma etching of ITO (In2O3:Sn indium tin oxide) thin films has been performed using a CH4/H2 plasma. Etching occurs above a substrate temperature (T
s) of 60°C and the etch rate increases with increasing T
s, while amorphous like or polymer-like carbon deposits onto the ITO films below 60°C. The apparent activation energy of the etching is 4.12 kcal/mol (0.18 eV). This small activation energy suggests that the desorption of produced volatiles is the rate-limiting process. Fine ITO patterns (1.5 µmL/S) were obtained using this gas mixture.
Structural Characterizations of Conformally Grown (100) Si Films
Authors: Pribat D. , Chazelas J. , Dupuy M.
Published: February 2005

The defect structure of conformally grown Si films is investigated using electron microscopy techniques. Twins, stacking faults and dislocations are evidenced, mainly located at the different Si/SiO2 interfaces.
A qualitative model of defect generation is presented which suggests that these different defects mainly originate from differential thermal expansion problems associated to the “micro-roughness” of the Si/SiO2 lateral interfaces.
Optimization of Single Crystal Preparation of Bi2Sr2CaCu2Ox Superconductor by the Travelling Solvent Floating Zone Method
Authors: Shigaki Ichiro , Kitahama Katsuki , Shibutani Kazuyuki , Hayashi Seiji , Ogawa Rikuo , Kawate Yoshio , Kawai Tomoji , Kawai Shichio , Matsumoto Masahide , Shirafuji Junji
Published: February 2005

Optimization of single crystal preparation of the Bi2.2(Sr, Ca)2.8Cu2.0O
y
superconductor by the travelling solvent floating zone method has been performed with the intention of obtaining large single crystals and improving the superconductive transition temperature, T
c. The composition ratio, Sr/Ca, and the oxygen partial pressure of growth atmosphere, PO2
, were varied in the crystal growth. A single crystal typically obtained was a thin plate of the dimensions of 5×50×2 mm3. The thickness of the crystal was the largest in the crystal growth at Sr/Ca=1.4, while no distinct change was observed in the resulting crystals in the range of 22∼100 kPa. Electric and magnetic properties, the formal charge of copper ions and existence of ion defects are discussed.
Sorption and Desorption Characteristics of Water Vapour on YBa2Cu3O7-x Powders
Authors: Sakka Yoshio , Uchikoshi Tetsuo
Published: February 2005

The sorption isotherms of water vapour of YBa2Cu3O7-x
were determined volumetrically at 26°C. The reaction of the powders with water is observed at relative pressures above 0.2, where a small amount of oxygen desorption is detected. Temperature-programmed desorption spectra of the powders exposed to water vapour at 26, 120 and 200°C have two desorption peaks of water. One is due to the chemisorbed water and the other originates from the reacted hydroxide which is considered to be in the amorphous phase.
Phase Control of Bi-Sr-Ca-Cu-O Thin Films Prepared by Coevaporation with RF Oxygen Plasma
Authors: Ishizuka Yoshiki , Terashima Yoshiaki , Miura Tadao
Published: February 2005

Thin films of Bi-Sr-Ca-Cu-O were prepared on (100)SrTiO3 substrates by coevaporation with rf oxygen plasma. It has been confirmed that the structural phases of films can be controlled mainly by the flux density of activated oxygen and the substrate temperature, and not by the chemical compositions of the films. Thin films in the Bi2(Sr, Ca)3Cu2O
y
phase and the Bi2(Sr, Ca)2CuO
y
phase were prepared by changing the flux density of activated oxygen and the substrate temperature. The films in the Bi2(Sr, Ca)3Cu2O
y
phase showed superconducting transitions at 35 K.
A Semiconductor Laser as a Stable Phase Conjugate Mirror for Linewidth Reduction of Another Semiconductor Laser
Authors: Ohtsu Motoichi , Koshiishi Isao , Teramachi Yasuaki
Published: February 2005

An AlGaAs laser was used as a phase conjugate mirror. Reflectivities as high as 103 and bandwidth as wide as 1.9 GHz were observed. The linewidth of a second AlGaAs laser was reduced to 1/5 times that of its free-running value by optical feedback of the phase conjugate wave generated by the first laser. The reduced linewidth was independent of the separation between the two lasers, and was maintained in a stable manner for over two hours.
Thermal Expansion of Sol-Gel SiO2 Glass Fibers
Authors: Kobayashi Hiroshi , Yamaguchi Yukio
Published: February 2005

The thermal expansion of SiO2 glass fibers synthesized by the sol-gel method was measured in the temperature range of 100 to 300°C using a laser interferometer developed at NRLM. Fibers as grown represent shirinkage of length, but after annealing, thery represent low thermal expansion as is seen in the usual sol-gel SiO2 glasses. It is believed that the former is in a sintering process and the latter is a true glass.
RHEED Intensity Oscillation during Epitaxial Growth of Layered Materials
Authors: Shimada Toshihiro , Yamamoto Hideki , Saiki Koichiro , Koma Atsushi
Published: February 2005

Diffracted beam intensities in reflection high energy electron diffraction (RHEED) have been observed to oscillate during the epitaxial growth of NbSe2 and MoSe2 on GaAs(111) substrates. This is the first observation of RHEED oscillation in layered materials, to the author's knowledge. Monolayer- and bilayer-mode oscillations have been observed at different diffraction points. The existence of the bilayer-mode oscillation leads to the determination of the polytype of the grown films. It has also been shown that the antiphase portion of the grown film is considerably small.
In Situ Scanning Tunneling Microscopy Observation of Electroless-Deposited NiP Film
Authors: Homma Takayuki , Yamazaki Takuya , Kubota Toshimoto , Osaka Tetsuya
Published: February 2005

Preliminary results of an in situ scanning tunneling microscopy (STM) observation of electroless-deposited NiP film as well as that of electrodeposited film were demonstrated. The electroless-deposited film is observed to develop rough features consisting of small grains, suggesting the successive nucleation of the grains and their three-dimensional growth. The electro-deposited film, in contrast, consists of larger grains with smooth features.
Nonresonant Absorption of One Photon by One Atom and Resonant Absorption of Two Photons by Two Atoms
Authors: Mizushima Masataka
Published: February 2005

When a radiation field of frequency ω1 interacts with atoms, etch of which has a transition frequency ω
b
a
=(E

b
-E

a
)/\hbar, with ω1-ω
b
a
=Δ≠0, nonresonant absorption can take place with probability P
1 inversely proportional to Δ
2 (a pressure broadening). When another radiation field of frequency ω2, such that ω1+ω2=2 ω
b
a
, interacts simultaneously with the gas a resonant two-photon absorption can take place in addition to the nonresonant absorption. The probability of this two-photon absorption process, P
2, is found to be inversely proportional to Δ
4. If \varOmega=| | is the Rabi frequency of the transition, it is found that P
2/(P
1(Δ)+P
1(-Δ)) is given by 12{ \varOmega(-Δ)\varOmega(-Δ)}2/{Δ
2(\varOmega(-Δ)2+\varOmega(Δ)2)}.
Laser Cooling and Trapping of Calcium and Strontium
Authors: Kurosu Takayuki , Shimizu Fujio
Published: February 2005

Calcium and strontium atomic beams are cooled and trapped by using the 1S0-1P1 transition in the 400 nm region. The trapping of 8 isotopes, 40Ca, 42Ca, 43Ca, 44Ca, 84Sr, 86Sr, 87Sr and 88Sr, is observed. The decay rate of the trapped atom is found to be of the order of 10 ms and the average atomic velocity less than 1 m/s.
The Role of Hydrogen Atoms in Afterglow Deposition of Silicon Thin Films
Authors: Meikle Scott , Nakanishi Yoichiro , Hatanaka Yoshinori
Published: February 2005

Silicon thin film deposition resulting from addition of SiH4 to the afterglow of an H2 plasma has been investigated. A simple experiment where a steel insert has been used to quench H atoms in the afterglow indicates that H atoms from the plasma are not required for film growth. It is proposed that the results are most easily interpreted using a model where SiH2 is the growth precursor.
Improvement of Hydrogenated Amorphous Silicon n-i-p Diode Performance by H2 Plasma Treatment for i/p Interface
Authors: Ihara Hisanori , Nozaki Hidetoshi
Published: February 2005

Hydrogenated amorphous silicon (a-Si:H) n-i-p diodes in which the intrinsic (i-type) layer surfaces were exposed to an H2 plasma before depositing the p-type layer (H2 plasma treatment of the i/p interface) were prepared. The effects of this H2 plasma treatment of the i/p interface were observed by dark I-V, photo-I-V under 450 nm illumination, and quasistatic C-V measurements. It has been found that the defect density at the i/p interface is reduced by this treatment. It has also been determined that the performance of a-Si:H diodes is improved by this treatment of the interface.
An Npn AlGaAs/GaAs Collector-up HBT with an H+-Implanted High Resistivity Layer under the External p+-GaAs Base
Authors: Yanagihara Manabu , Ota Yorito , Ryoji Akira , Inada Masanori
Published: February 2005

The npn AlGaAs/GaAs collector-up (C-up) heterojunction bipolar transistor (HBT) with an H+-implanted high resistivity layer (HRL) under the external p+-GaAs base layer has been successfully fabricated for the first time. For suppressing parasitic current from the emitter to external base when operating foward bias voltages, the H+-implanted HRL is superior to the O+-implanted and annealed HRL or the pn junction of wide band gap under the external base.
High-Pressure Synthesis of Superconducting YSr2Cu3Oy
Authors: Okai Bin
Published: February 2005

At a high oxygen pressure of 7 GPa and high temperature of 1380°C, YSr2Cu3O
y
was synthesized as a single phase. The crystal structure is a tetragonal “1-2-3” type, where a and c are 3.7949 Å and 11.4102 Å, respectively. This material is a superconductor with an onset temperature of 60 K.
Metal-Insulator Transition in Layered-Perovskite Sr3V2O7
Authors: Fukushima Noburu , Tanaka Shigenori , Niu Hiromi , Ando Ken
Published: February 2005

We have found a metal-insulator transition in the layered-perovskite vanadate Sr3V2O7. The transition from the metallic state to the insulating state took place by substituting Cr for V. Magnetization measurements did not indicate the drastic change between metallic and insulating states. The possibility of high-T
c superconductivity was also discussed in comparison with the layered-cuprate and other oxide superconductors.
Preparation of YBaCuO Films by Polarized Plasma Oxidation of Multilayered Films
Authors: Ito Wataru , Shimada Haruo , Ito Satoshi
Published: February 2005

YBaCuO superconducting thin films were prepared by oxidizing the multilayered thin films composed of Ba, Y2O3 and Cu in the oxygen-helium plasma. The superconductive properties of these films were found to be strongly dependent on the DC bias applied to the substrate during plasma oxidation. The negative bias increases the c-axis-preferred orientation, whereas the oxidation proceeds more easily under the positive bias. Therefore, the combination of both negative and positive bias is of great advantage to the preparation of high-quality superconducting thin films.
Two-Frequency Operation of a Hybrid TEA CO2 Laser and Its Application to Two-Frequency Pulse Injection Locking
Authors: Sasaki Koichi , Ohno Hirotaka , Fujii Takaharu , Tsukishima Takashige
Published: February 2005

Simultaneous two-frequency oscillation of a hybrid TEA CO2 laser is exhibited when the cw section is operated in a “below threshold” state. The output of the hybrid laser thus obtained is injected into a main TEA CO2 laser to obtain a power-modulated, long-pulse output with a well suppressed gain-switched spike.
Dispersion of Thermal Ripplon on Free Surfaces of Pure Liquids Measured up to 6 MHz
Authors: Sakai Keiji , Tanaka Hajime , Takagi Kenshiro
Published: February 2005

The dispersion and damping constant of the thermally excited surface-tension wave (ripplon) have been measured for free surfaces of water and some other liquids. The upper limit of the frequency range observed is extended up to 6 MHz with a newly developed light-scattering technique. The behavior of the ripplon is well described by the hydrodynamic theory throughout the whole experimental range, leaving no possibility of the surface viscosity which has been suggested by previous studies.
Hot-Carrier Degradation Effects Relevant in Real Operation of Metal Oxide Semiconductor Field Effect Transistors
Authors: Weber Werner , Wang Qin , Brox Martin , Schmitt-Landsiedel Doris
Published: February 2005

This paper describes hot-carrier stress experiments of various stages appearing in digital logic, such as inverters, NANDs, NORs, and transfer gates. Transient effects are proven to be unimportant while the effect of voltage combinations can cause small errors in duty cycle calculations. A relation between static and dynamic lifetimes is given and a more realistic lifetime criterion is proposed. The stress measurements of the logic stages show an agreement with the duty cycle calculation except for the bidirectionally stressed transfer gate. For this stage, specific stress conditions and lifetime criteria must be defined.
Analytical Model for Circuit Simulation with Quarter Micron Metal Oxide Semiconductor Field Effect Transistors: Subthreshold Characteristics
Authors: Miura-Mattausch Mitiko , Jacobs Hermann
Published: February 2005

For deep submicron MOSFETs short-channel effects dominate the transistor characteristics. This is due to the increase of the lateral electric field. This paper provides a new simple model which includes the gradient of the lateral electric field in an analytical way. The model describes the subthreshold characteristics relating to short-channel effects correctly down to 0.1 µm effective channel length L
eff with physical parameters (N
sub, C
ox, V
fb, φf) taken from the long-channel device.
Evaluation of the Si-SiO2 Interface by the Measurement of the Surface Recombination Velocity S by the Dual-Mercury Probe Method
Authors: Suzuki Eiichi , Takato Hidetaka , Ishii Kenichi , Hayashi Yutaka
Published: February 2005

A novel evaluation technique of the surface recombination velocity S at the Si-SiO2 interface based on the dual-mercury probe method is proposed. It is shown that the experimentally obtainable S takes an extremely low value of less than 10 cm/s under both accumulation and inversion surface conditions whether high D
it exists or not, and the S has a pyramidlike peak from the weak inversion condition to the weak accumulation condition. These experimental results indicate that strong band bending at the interface and a well-prepared interface are quite effective in reducing the surface carrier recombination.
Modeling of Band-to-Band Tunneling Mechanisms
Authors: Wolfgang Wolfgang , Bergner Bergner , Roland Roland , Kircher Kircher
Published: February 2005

Measurements and simulations are presented, which allow a better understanding of leakage mechanisms in reverse biased gated diodes. The model for the device simulation describes two mechanisms. In the high field regime the leakage current is identified as direct band-to-band tunneling. In the low field regime it is described as surface-state enhanced tunneling, which combines thermal activation of an electron to a surface-state with tunneling.
Sharp Boron Spikes in Silicon Grown at Reduced and Atmospheric Pressure by Fast-Gas-Switching CVD
Authors: Vink Adriaan T. , Roksnoer Piet J. , Maes Johannes W. F. M. , Vriezema Cornelis J. , van Ijzendoorn Leo J. , Zalm Peer C.
Published: February 2005

Boron doping spikes in Si were grown by fast-gas-switching CVD at 800 and 850°C using Si2H6 and B2H6 in 0.03, 0.1 and 1 atm H2 as the carrier gas. The B2H6 doping gas was added for 2 s by two methods, namely during growth or as a flush while the Si2H6 flow was interrupted. High-resolution SIMS measurements have revealed extremely sharp and highly concentrated dopant profiles. Peak B concentrations up to 5×1021 cm-3 and, at 1 atm H2, a FWHM of 3 nm were obtained. Electrical measurements show that for B-spikes having a FWHM value of 4–5 nm, a sheet resistivity of as low as 580 Ω/ \Box can be obtained.
Silicon Wafer Bonding Mechanism for Silicon-on-Insulator Structures
Authors: Abe Takao , Takei Tokio , Uchiyama Atsuo , Yoshizawa Katsuo , Nakazato Yasuaki
Published: February 2005

X-ray diffraction topography and tensile testing are used to study the perfection of bonded interfaces in the sandwich structure where one of the two silicon wafers used had an SiO2 layer applied to it first. The tensile strength and the formation of unbonded areas (voids) were compared to the cases where two bare silicon wafers were used and where both wafers were coated with oxide. There are two mechanisms for wafer bonding: one is for a lower temperature and another is for a higher temperature range. It is concluded that a strong affinity between the two wafers at low temperatures is essential to obtaining tight bonding after a high-temperature anneal. A proper amount of H, OH and H2O on the wafers plays an important role in good chemical bonding below 800°C. Above 1000°C an interaction between adjacent atoms to create covalent bonding and deformation of the SiO2 layer are effective in establishing good bonding.
As+-Preamorphization Method for Shallow p+-n Junction Formation
Authors: Kwon Sang-Jik , Kim Hyeong-Joon , Lee Jong-Duk
Published: February 2005

The effects of preamorphization by As+ implantation for the shallow p+-n junction formation have been investigated in this study. The retarded diffusion effect of boron atoms due to the electric field produced by arsenic profile was observed during annealing. The shallow p+-n junction with low leakage was obtained by optimizing the thickness of the preamorphized layer.
Homogeneous Heteroepitaxial NiSi2 Formation on (100)Si
Authors: Kunishima Iwao , Suguro Kyoichi , Aoyama Tomonori , Matsunaga Junichi
Published: February 2005

The mechanism of NiSi2/Si interface formation on (100)Si is examined. The interface roughness between NiSi2 and Si strongly depends on the substrate impurity species. A smooth interface is formed on As-doped Si, but the interface is highly faceted on the {111} plane on BF2-doped Si. The covalent radius of the impurity atoms strongly affects the interface formation. An interfacial distorted layer is observed only at the NiSi2/As-doped Si interface. This distorted layer could reduce the lattice strain between NiSi2 and Si. These results demonstrate the possibility of realizing a homogeneous epitaxial interface.
Highly Reliable Thin Nitrided SiO2 Films Formed by Rapid Thermal Processing in an N2O Ambient
Authors: Fukuda Hisashi , Arakawa Tomiyuki , Ohno Seigo
Published: February 2005

A novel method of nitridation of thin SiO2 film (<10 nm) has been achieved for the first time by in situ multiple rapid thermal processing (RTP) using oxygen (O2) and nitrous oxide (N2O) as reactants. Nitrided SiO2 (SiO
x
N
y
) films, in which nitrogen piles up about 5 at% at the SiO
x
N
y
/Si interface, showed smaller densities of electron and hole traps in high-field stressing as compared to those of pure SiO2 films. However, only the SiO
x
N
y
film formed via oxidation in O2 and following nitridation in N2O ambients has a large charge-to-breakdown value (>30 C/cm2) and indicates a quite uniform interface ordered within at least one or two atomic layers.
Growth of ZnSe/GaAs Superlattices by Migration-Enhanced Epitaxy
Authors: Kobayashi Naoki , Horikoshi Yoshiji
Published: February 2005

ZnSe/GaAs superlattices are grown on (001)-oriented GaAs substrates by migration-enhanced epitaxy. By this method, high-quality GaAs layers can be grown on GaAs substrates at temperatures as low as 250°C, which corresponds to the optimum growth temperature of ZnSe. However, the extremely low sticking coefficient of As4 onto a ZnSe surface deteriorates the crystal quality of GaAs on ZnSe. To solve this problem, GaAs growth on ZnSe is initiated by As4 deposition at room temperature. A few atomic layers of Ga are then deposited. After annealing at 250°C, GaAs growth is continued by migration-enhanced epitaxy. This method produces superlattices with a low density of dislocations and defects. Transmission electron microscope observation of the superlattice shows the GaAs growth rate per one cycle of alternately supplied Ga and As4 to be almost constant throughout a superlattice growth of 12 periods. However, the ZnSe growth rate per one cycle of alternate Zn and Se deposition increases from about 0.35 monolayer in the first period and tends to saturate at about 0.5 monolayer at the particular growth temperature of 250°C. To explain this, a missing Zn array structure of the c(2×2) reconstructed structure is proposed along the [100] and [1̄00] directions.
High Mobility Poly-Si Thin Film Transistors Using Solid Phase Crystallized a-Si Films Deposited by Plasma-Enhanced Chemical Vapor Deposition
Authors: Takenaka Satoshi , Kunii Masafumi , Oka Hideaki , Kurihara Hajime
Published: February 2005

Thin film transistors (TFTs) have been developed on quartz substrates by using large-grain-size polycrystalline silicon (poly-Si) films. The poly-Si films were fabricated by solid phase crystallization (SPC) of amorphous silicon (a-Si) deposited by plasma-enhanced chemical vapor deposition (PECVD). We have found that the dehydrogenation process is strongly correlated with the SPC of the a-Si, especially in nucleus generation time. The n-channel TFT mobility of 158 cm2/(V ·s) is obtained by using the SPC of the PECVD a-Si.
Native Oxide Growth on Silicon Surface in Ultrapure Water and Hydrogen Peroxide
Authors: Morita Mizuho , Ohmi Tadahiro , Hasegawa Eiji , Teramoto Akinobu
Published: February 2005

The effects of n-type dopant (P, As) concentration in silicon (100), temperature, and oxidizing species on native oxide growth in liquid water are described. The oxide growth on phosphorus (P)- and arsenic (As)-doped n+-Si surfaces (1020 cm-3) in ultrapure water exhibits saturation of oxide thickness, suggesting a field-assisted mechanism. Oxide thickness saturation was also found on n-Si in hydrogen peroxide (H2O2) solution or in H2O2 solution in the presence of a platinum (Pt) mesh that creates oxidizing radicals or ions. The oxide growth rate in ultrapure water increases with an increase of temperature.
Minimizing Wafer Surface Damage and Chamber Material Contamination in New Plasma Processing Equipment
Authors: Goto Haruhiro , Sasaki Makoto , Ohmi Tadahiro , Shibata Tadashi , Yamagami Atsushi , Okamura Nobuyuki , Kamiya Osamu
Published: February 2005

Magnetic enhancement was determined to be effective in reduction of the plasma potential. In extremely high-excitation-frequency plasma, the self-bias voltage of the electrode was substantially reduced, while the plasma potential remained constant. The plasma potential was effectively controlled by utilizing a DC-biased shield electrode, and found to be very effective in minimizing the chamber material contamination. The dual rf excitation plasma processing equipment was proposed and found to be capable of controlling the self-bias of the substrate without altering the target self-bias voltage.
Molecular Beam Epitaxy Grown GaAs Bipolar-Unipolar Transition Negative Differential Resistance Power Transistor
Authors: Yarn Kao-Feng , Chang Chun-Yen , Wang Yeong-Her , Wang Ruey-Lue
Published: February 2005

This letter describes a power GaAs bipolar-unipolar transition negative differential resistance transistor (BUNDR) using n+-i-p+-i-n+ structure prepared by molecular beam epitaxy (MBE). The peak-to-valley current ratios (PVRs), peak current densities and generated power outputs can be easily modulated by changing the third external base to emitter bias. A highest PVR of 140 with V
BE=0.5 V at room temperature has been obtained. For power consideration, it can be compared with resonant tunneling hot electron transistors. The bipolar-unipolar transition action was also confirmed experimentally.
InAs/GaSb Hot Electron Transistors Grown by Low-Pressure Metalorganic Chemical Vapor Deposition
Authors: Taira Kenichi , Nakamura Fumihiko , Hase Ichiro , Kawai Hiroji , Mori Yoshifumi
Published: February 2005

We have investigated an abrupt and a graded GaInSb collector and GaSb collector in LPMOCVD grown HETs and report the effect of the collector barrier on device performance. The device uses a GaSb emitter barrier and 100 Å-wide InAs base. The room temperature common-emitter current gains for the GaSb barrier HET, the abrupt collector one, and the graded collector one are 0.5, 1.2 and 1.6, respectively. The collector barrier for the GaSb HET is the highest. The barriers for the other two cases are comparable. The grading reduces the quantum reflection to enhance the collector current.
A Tristate Switch Using Triangular Barriers
Authors: Wang Y. H. , Yarn K. F. , Chang C. Y.
Published: February 2005

We demonstrate a new GaAs regenerative switching device with a double triangular barrier (DTB) structure, i.e., p+-i- δ(n+)-i- δ(p+)-i-n+, prepared by molecular beam epitaxy (MBE). Using the concept of sequential collapse of the internal barriers, two distinctive switching regions are established. First, a negative resistance region (S-type) is observed, followed by a positive resistance region (inverted N-shape) in between the switching behavior with the increase of applied bias. This device may have applicability for tristate logic circuits.
Single (2223) Phase and Transport Current Path in Bi-Pb-Sr-Ca-Cu-O
Authors: Oota Akio , Ohba Kentaro , Ishida Akira , Noji Hideki , Kirihigashi Akihiro , Iwasaki Kiyotoshi , Kuwajima Hideaki
Published: February 2005

Studies of DTA, XRD, resistivity and susceptibility are made for oxides with the nominal composition of Bi2Pb0.6Sr2Ca2Cu3O
x
. The (2223) phase has been singled out, to our knowledge, in the shortest sintering time reported so far in air from the partially melted phase by introducing the re-press process, but the value of T
c(ρ=0) is lowered to ∼73 K by a disturbance in current paths at the grain boundaries. A prolonged sintering improves this and enhances T
c(ρ=0) to above 100 K. Taken together, we can see the efficacy of the re-press process and the slowness of the intergrain reaction to open up the current paths.
Preparation of High-Quality Bi-Pb-Sr-Ca-Cu Oxide Precursor by the Citrate Gel Process
Authors: Aoki Aiko
Published: February 2005

In order to achieve a high-T
c superconducting phase of Bi-Pb-Sr-Ca-Cu oxide, we applied a highly reactive citrate gel process to yield a precursor powder. A citrate-nitrate solution was dehydrated and heated to form the desired compound. We applied a thermogravimetric analysis, scanning electron microscopy and X-ray diffraction to study thermal decomposition during the heat stage. Sintered sample showed good superconducting properties with T
c above 100 K. Chemical analyses revealed negligible loss of metals during the preparation procedure, indicating that the citrate gel process is an excellent and reliable method for this compound.
Superconductivity of Bi System Thin Films Formed by Consecutively Sputtering Three Pb-Doped Targets of Slightly Different Compositions
Authors: Kuroda Ken'ichi , Kojima Kazuyoshi , Tanioku Masami , Yokoyama Kazuo , Hamanaka Koichi
Published: February 2005

Superconducting Bi system thin films have been formed on MgO(100) substrates by RF magnetron sputtering from three lightly Pb-doped targets: Bi2.4Pb0.6Sr2Ca2Cu3O
x
, Bi1.6Pb0.4Sr3Ca3Cu3O
x
and Bi1.6Pb0.4Sr2Ca2Cu4.5O
x
. To improve the superconductivity of the as-grown films, the films were kept in a sputtering chamber after deposition. The film, formed at 660°C and kept at the same substrate temperature and gas pressure as the sputtering conditions for 5 h after deposition, showed zero resistivity at 83 K and a resistivity drop at 115 K. The critical current density of the film was 4×105 A/cm2 at 77 K and 1×107 A/cm2 at 52 K.
Preparation of As-Deposited Bi-Sr-Ca-Cu-O Films with High Tc Superconducting Phase by Metalorganic Chemical Vapor Deposition
Authors: Endo Kazuhiro , Hayashida Shigeru , Ishiai Junichi , Matsuki Yuji , Ikedo Yozo , Misawa Shunji , Yoshida Sadafumi
Published: February 2005

As-deposited Bi-Sr-Ca-Cu-O films with the high T
c phase were prepared on MgO (100) substrates by metalorganic chemical vapor deposition using triphenyl bismuth and β-diketonates of Sr, Ca and Cu as source materials. Films with a superconducting onset temprature of 110 K and a zero resistance temperature of 70 K were obtained at 800°C without postannealing. The X-ray diffraction patterns show that the films consist of the high T
c single phase with the c-axis oriented normal to the substrate surfaces. The surface structures of the films were found to be much smoother than those of postannealed ones.
Discrete Shifts of Absorption and Emission Lines by Individual Electron-Hole Pair Excitation in DC-Biased Quantum Box Structures
Authors: Yamanishi Masamichi , Osaka Yukio , Kurosaki Masami
Published: February 2005

It is discussed theoretically that two kinds of substantial jumps of optical transition energies, a blue shift of emission and absorption lines and a red shift of the emission line from the absorption line, caused by a single electron-hole pair excitation, should occur in three-dimensional mesoscopic structures, quantum boxes. (quantum dots) and microcrystallites, biased by dc-electric fields. We illustrate the theory with specific calculations for hypothetical GaAs-like quantum boxes.
Extremely Low Threshold Butt-Jointed 1.5 µm DBR Lasers
Authors: Lesterlin D. , Gilleron M. , Chaminant G. , Robein D. , Bouley J. C.
Published: February 2005

A simple new fabrication process for 1.5 µm Distributed Bragg Reflector Laser is proposed. A butt-junction coupling is used between the active and passive waveguide. The average pulsed threshold current of 400 µm long laser with 200 µm long 1st order grating DBR section is 10 mA. A threshold current in DC operation as low as 7.7 mA has been measured.
An Electric Bilayer Model of the Transient Current in a Nematic Liquid Crystal Cell
Authors: Mochizuki Akihiro , Yoshihara Toshiaki , Motoyoshi Katsusada , Kobayashi Shunsuke
Published: February 2005

The transient currents were observed in nematic liquid crystal (LC) cells when the polarity of the applied square wave voltage was reversed. The magnitude of these currents were shown to increase when the used LCs have a tendency to form dimers and the orientation films have a high electrical polarization. The origin of the transient currents is explained by assuming the switching of LC layers associated with the bilayers made of decomposed monomers adsorbed on the orientation films. The origin of the crosstalk appearing in the STN dot matrix LCDs is discussed in conjunction with the decomposition of dimers in the surface alignment region.
Different Effects of Alkyl Chain Length on Rotational Viscosity in Two Types of FLC Mixtures
Authors: Nishiyama Isa , Shiratori Nobuyuki , Fukumasa Mitsuo , Yoshizawa Atsushi , Hirai Toshihiro
Published: February 2005

In order to clarify the role of intermolecular interaction, effects of alkyl chain length on the rotational viscosity are investigated in two types of FLC mixtures: a totally chiral compound system and a chiral-compound-doped system. Only in the case of the chiral-compound-doped system does a long alkyl chain, which can produce the strong intermolecular interaction, provide the low rotational viscosity. In this system, ferroelectrically triggered orientation change of a small amount of chiral molecules induces the orientation change of a large amount of non-chiral molecules. It is suggested that the strong intermolecular interaction between the chiral and non-chiral molecules is required in order to amplify the molecular orientation change efficiently.
Dielectric Dispersion in the Antiferroelectric Liquid Crystal MHPOBC
Authors: Fukui Minoru , Orihara Hiroshi , Suzuki Atsushi , Ishibashi Yoshihiro , Yamada Yuichiro , Yamamoto Norio , Mori Kaoru , Nakamura Koji , Suzuki Yoshiichi , Kawamura Ichiro
Published: February 2005

The dielectric dispersion in the ferroelectric and antiferroelectric phases of a smectic liquid crystal, 4-(1-methylheptyl-oxycarbonyl)phenyl 4'-octyloxybiphenyl-4-carboxylate (MHPOBC), has been measured with several frequencies between 100 Hz and 100 kHz. The soft mode with the Debye-type dispersion was observed in the phase transition from the Sm A phase to the ferroelectric Sm C* phase. In the Sm C* phase, the Goldstone mode was observed at the frequency of about 4.5 kHz. The dielectric dispersion in the Sm CA
*, Sm Cα
* and Sm Cγ
* phases is discussed.
Positron Study of Vacancy-Type Defects Induced by Heavy Doping into MBE-Grown GaAs
Authors: Uedono Akira , Tanigawa Shoichiro
Published: February 2005

Variable-energy positron beam studies have been carried out on heavily Si-doped GaAs/AlGaAs/GaAs specimens prepared by molecular beam epitaxy. From the measurements of Doppler broadening profiles of the positron annihilation as a function of the incident positron energy, it was found that Ga vacancies with very high concentration are introduced in the GaAs layer by the heavy doping of Si. It was concluded that a Ga vacancy acts to reduce the concentration of free carriers.
A Chemical Method for Preparing Copper Iodide Thin Films
Authors: Chaudhuri T. K. , Basu P. K. , Patra A. B. , Saraswat R. S. , Acharya H. N.
Published: February 2005

A chemical method for preparing CuI thin films by iodination of solution grown Cu2S films is described. X-ray characterization identifies γ-CuI and suggest that the films are polycrystalline in nature. SEM reveals a granular film morphology. Optical studies show that the band gap of the material is 2.93 eV. The sheet resistance of the films is in the range 1 to 3 k Ω/sq.