bluuebunny/crossref_metadata_2025 huggingface dataset:
Mass Spectrometry, Optical Emission Spectroscopy, and Atomic Force Microscopy Studies of Si Etch Characteristics in a Cl2 Plasma Generated by an Electron Cyclotron Resonance Source
Authors: Kuo-Tung Sung Kuo-Tung Sung , Stella W. Pang Stella W. Pang
Published: October 2002

Etching of Si with a Cl2 plasma generated by a multipolar electron
cyclotron resonance source has been studied using mass spectrometry, optical emission
spectroscopy (OES), and atomic force microscopy (AFM). It is found that the Si etch rate
can be related to the SiCl63 intensity measured using mass spectrometry and the
Si emission intensity at 634.6 nm using OES. At higher microwave or rf power, the Si
etch rate, SiCl63 intensity, and Si emission intensity increase but the
selectivity of Si over SiO2 decreases. Selectivity >80 is obtained with
30% O2 addition in Cl2. The induction time for Si etching is monitored
by mass spectrometry and it decreases with microwave or rf power. Surface roughness is
measured by AFM and it increases slightly with microwave or rf power. The optimized
condition for Si etching was applied to the etching of polysilicon gate down to the
thin gate oxide. A two-step etch process was developed for the etching of 0.35 µ m
polysilicon gate with vertical profile, smooth morphology, and high selectivity to the
underlying gate oxide. Only 0.5 nm of the gate oxide was removed with 100% overetch.
End point for polysilicon gate etching was clearly monitored using mass spectrometry or OES.
Scanning Tunneling Microscopy Study of GaAs Step Structures on Vicinal Substrate Grown by Metalorganic Chemical Vapor Deposition
Authors: Makoto Kasu Makoto Kasu , Naoki Kobayashi Naoki Kobayashi
Published: October 2002

Scanning tunneling microscopy (STM) is used to study the step structure of metalorganic chemical vapor deposition (MOCVD)-grown GaAs on a vicinal substrate. We passivated the as-grown surfaces with As in a vacuum chamber connected to the MOCVD system in order to protect it from oxidation during its transfer to the STM system. The undulation amplitude of the monolayer steps grown on a surface misoriented in the [110] direction is about twice that of these grown on a surface misoriented in the [1̄10] direction. On a substrate at misorientation angles equal to or less than 7.0°, surfaces show a monolayer step staircase when the growth temperature (T
g)>650° C; step bunching occurs and the vicinal surface decomposed into (001) terraces and facets on which steps bunch when 575° C≤T
g≤650° C; and elliptical two-dimensional islands form between the monolayer steps because of a decrease of Ga diffusion coefficient when T
g<575° C.
Analysis of Charging Effect During Observation of Trench Structures by Scanning Electron Microscope
Authors: Kotera Masatoshi , Yamaguchi Satoru , Sachio Umegaki Sachio Umegaki , Hiroshi Suga Hiroshi Suga
Published: October 2002

Charge deposition distribution is calculated by Monte Carlo simulation of electron
scattering in an insulator. Using this distribution and the boundary conditions of the
specimen chamber of the scanning electron microscope, the voltage distribution is obtained
inside and outside the trench structure by solving the Poisson equation. Electron
trajectories emitted from the bottom of the trench are traced by the equation of motion,
and the efficiency of an electron to exit the trench is calculated. It is found that
negative charging-up may be effective to obtain a bright image of the bottom surface of
the trench by the scanning electron microscope.
Estimation of Carrier Suppression by High-Energy Boron-Implanted Layer for Soft Error Reduction
Authors: Kishimoto Takehisa , Sayama Hirokazu , Takai Mikio , Ohno Yoshikazu , Sonoda Kenichirou , Nishimura Tadashi , Kinomura Atsushi , Horino Yuji , Fujii Kanenaga
Published: October 2002

Effect of charge-carrier suppression by a high-energy boron-implanted layer has been investigated by ion-induced-current
measurement using high-energy proton microprobes. Proton microprobes at 1.3 and 2.0 MeV
have been irradiated normal to the n+p diode to generate electron-hole pairs. The collection of charge carriers
induced by microprobe irradiation could be reduced by a buried layer formed by boron implantation. It was found
that the rate of charge collection depended on the implantation dose but not on the depth of the buried layer.
Behavior of Defects Induced by Low-Energy Ions in Silicon Films
Authors: Sadoh Taizoh , Takeshita Hironori , Baba Akiyoshi , Kenjo Atsushi , Hiroshi Nakashima Hiroshi Nakashima , Toshio Tsurushima Toshio Tsurushima
Published: October 2002

Behavior of defects induced by low-energy (5 keV at maximum) argon ions or protons in 600 nm thin silicon
crystals has been investigated. A significant amount of defects diffuse from the damaged surface layers to the
deeper regions even at room temperature, and act as the carrier traps and the scattering center that affect the
electrical properties of the films. Most of the defects disappaer after annealing at 300°C. Electrical and thermal
properties of the defects depend on the creation rate of Frenkel pairs.
Fabrication and Magnetotransport of One-Dimensional Lateral Surface Superlattice Fabricated by Low-Energy Ion Irradiation
Authors: Takahara Junichi , Ochiai Yukinori , Matsui Shinji , Takaoka Sadao , Murase Kazuo , Gamo Kenji
Published: October 2002

A new fabrication process of a lateral surface superlattice has been reported. A low-energy Ar ion irradiation has been used to fabricate a one-dimensional lateral surface superlattice. The decrease of carrier concentration and mobility has been investigated to avoid the serious damage caused by ion bombardment. The mobility decreases significantly with ion dose rather than carrier concentration and its scattering mechanisms are discussed. In addition, a Schottky gate on top of the superlattice is used to change the Fermi energy of two-dimensional electron gas and the anisotropic threshold characteristics are observed. Weiss oscillations can be modified by applying positive bias voltage to the gate.
Highly Uniform GaAs/AlAs Quantum Wires Grown on [001] Ridges of GaAs(100) Patterned Substrates by Molecular Beam Epitaxy
Authors: Liu Yi , Nishimoto Yoshinori , Shimomura Satoshi , Gamo Kenji , Murase Kazuo , Sano Naokatsu , Adachi Akira , Kanamoto Kyozo , Isu Toshiro , Fujita Katsuhisa , Watanabe Toshihide , Satoshi Hiyamizu Satoshi Hiyamizu
Published: October 2002

Highly uniform GaAs/AlAs ridge quantum well (QW) structures have been grown on ridges with various widths of about 0.1–1.3 µ m in the [001] direction on GaAs (100) patterned substrates by molecular beam epitaxy (MBE). A GaAs/AlAs quantum wire (QWR) with the cross-section of about 40± 7 nm (width)× 10–15 nm (thickness) grown on a [001] ridge with width of 0.45 µ m showed a very uniform cathodoluminescence (CL) at 78 K along the QWR. Linewidths of the CL peaks of the QWRs up to 75 µ m in wire length were as small as 20–26 meV. The CL peak intensity from only one GaAs/AlAs QWR was much larger than that from a GaAs/AlAs quantum well simultaneously grown on a flat GaAs (100) substrate when the excitation electron beam was 1 µ m in diameter, indicating the high optical quality of the QWRs.
Process-Induced Defects in InP Caused by Chemical Vapor Deposition of Surface Passivation Dielectrics
Authors: Hashizume Tamotsu , Hasegawa Hideki , Riemenschneider Rolf , Hartnagel Hans L.
Published: October 2002

Near-surface defects of InP produced during three different chemical vapor deposition (CVD) processes were systematically characterized by capacitance-voltage ( C-V ) and deep level transient spectroscopy (DLTS) techniques. Deposition of plasma-enhanced CVD (PECVD) phosphosilicate glass (PSG) and SiO2 films produced the same bulk level, lying at 0.35 eV below the conduction band edge, near the surface region of InP. Such a level was absent in the samples prepared by the photo CVD process. In addition, the photo CVD process gave a lower density of interface states than the PECVD process. The origin of the bulk trap and the energy- and space-distributed nature of interface states are discussed.
Growth Behavior and Mechanism of Alkyl-Desorption-Limited Epitaxial Growth of GaAs on Exactly Oriented and Vicinal Substrates
Authors: Goto Shu , Ishizaki Jun-ya , Takashi Fukui Takashi Fukui , Hideki Hasegawa Hideki Hasegawa
Published: October 2002

New atomically controlled epitaxial growth, called alkyl-desorption-limited epitaxial (ADLE) growth, is studied on (001) exactly oriented and vicinal GaAs substrates. In ADLE growth, the growth rate is limited by the desorption rate of alkyl from organometals rather than by saturation of alkyl adsorption. First, the proposed ADLE growth mechanism is quantitatively confirmed by comparing a new theory of growth based on the alkyl-desorption rate equations with the experimental growth data taken on (001) exactly oriented substrates. Next, the behavior of multi-atomic steps on vicinal substrates is studied using an atomic force microscope (AFM). It is found that the multi-atomic-step heights are reduced during ADLE growth. This new phenomenon is explained by the ADLE growth mechanism.
Effects of Phosphorus Pressure on Growth Rate and Layer Quality of InP Grown by Gas Source Molecular Beam Epitaxy
Authors: Yang Bing Xiong , Hasegawa Hideki
Published: October 2002

Effects of phosphorus pressure on the growth mechanism and the quality of the grown layers in gas source molecular beam epitaxial (MBE) growth of InP on (001) substrate are investigated. It is found that the normal growth process with the growth rate limited by indium flux intensity takes place only in a very narrow range of phosphorus supply. Outside this range, the growth rate depends also on phosphorus pressure. A significant decrease in growth rate under high phosphorus pressure is demonstrated to be due to oversaturation of the substrate surface by excess phosphorus. High phosphorus pressure deteriorates both the electrical and optical properties as well as the crystalline quality of the epitaxial layers. Incorporation of excessive phosphorus is shown to be responsible for deterioration, indicating that control of phosphorus pressure is very important for successful MBE growth of InP.
Characterization of In Situ Cl2-Etched GaAs Buffer Layers and Regrown GaAs/AlGaAs Quantum Wells
Authors: Tanaka Nobuyuki , Isamu Matsuyama Isamu Matsuyama , Tomonori Ishikawa Tomonori Ishikawa
Published: October 2002

We studied the interface between an in situ Cl2-gas-etched GaAs buffer layer and a regrown AlGaAs layer, as a function of the etching temperature, together with the optical properties of etched buffer layers and GaAs/AlGaAs quantum wells (QWs) which were regrown on the buffer layers. In the case of etching at 70° C, degradation of the photoluminescence (PL) was observed for the etched GaAs buffer layer and the regrown QWs, which extended 100 nm from the interface. With increasing etching temperature up to 200° C, on the other hand, the PL was greatly improved for both the etched GaAs buffer layer and the regrown QWs. This was due to the reduced C and O impurity accumulation at the etched/regrown interface, which was confirmed by secondary ion mass spectroscopy measurements.
Refractory WNx/W Self-Aligned Gate GaAs Power Metal-Semiconductor Field-Effect Transistor for 1.9-GHz Digital Mobile Communication System Operating with a Single Low-Voltage Supply
Authors: Nagaoka Masami , Ishida Kenji , Matsunaga Tokuhiko , Nishihori Kazuya , Hashimoto Takashi , Yoshimura Misao , Tanabe Yoshikazu , Mihara Masakatsu , Yoshiaki Kitaura Yoshiaki Kitaura , Naotaka Uchitomi Naotaka Uchitomi
Published: October 2002

We have developed a refractory WN

x

/W self-aligned gate GaAs power metal-semiconductor field-effect transistor (MESFET) for use in L-band digital mobile communication systems. This power MESFET operates with high efficiency and low distortion at a gate bias of 0 V and a low drain bias of 2.7 V, because of its small drain knee voltage, high transconductance and sufficient breakdown voltage. This power MESFET is quite promising for a highly efficient linear power amplifier IC operating with a single low-voltage supply. Good output characteristics of the power MESFET with 1 mm gate width were attained for π/4-shifted quadrature phase shift keying (QPSK) modulated input signals in the 1.9-GHz band, such as an output power of 18.4 dBm, a power gain of 19.0 dB and a high power-added efficiency of 26.4% when a sufficiently low adjacent channel leakage power of -58 dBc was obtained.
Transport Properties of Modulation-Doped Structures Grown by Molecular Beam Epitaxy after Focused Ion Beam Implantation
Authors: Itoh Masayuki , Saku Tadashi , Fujisawa Toshimasa , Yoshiro Hirayama Yoshiro Hirayama , Seigo Tarucha Seigo Tarucha
Published: October 2002

Modulation-doped structures are grown by molecular beam epitaxy after focused ion beam writing. The growth and implantation chambers are connected in a high vacuum to minimize the effect of growth interruption. The electron channel is drastically depleted by the buried Be+ implanted region, but only slightly depleted by the buried Au+ and Au2+ implanted regions. This is because Be+ implantation forms a p-type material, while Au+ or Au2+ implaniation leaves damage only in the n-type material. Be+ implantation is therefore used to fabricate 0.1 µm-wide wires with electron mobility of 2.1×105 cm2/Vs.
Infrared Hot-Electron Phototransistor
Authors: Victor Ryzhii Victor Ryzhii
Published: October 2002

A hot-electron phototransistor (HEPT) is proposed and discussed. The HEPT utilizes the intraband absorption of radiation in the base. This two-terminal device can operate as a photodetector for the infrared region of spectrum. Photoelectric performances of the HEPT are evaluated using an analytical model.
Quantitative Evaluation of Gate Oxide Damage during Plasma Processing Using Antenna-Structure Capacitors
Authors: Eriguchi Koji , Uraoka Yukiharu , Nakagawa Hideo , Tamaki Tokuhiko , Masafumi Kubota Masafumi Kubota , Noboru Nomura Noboru Nomura
Published: October 2002

Plasma-induced damage of gate oxides is evaluated from the difference between the intrinsic charge-to-breakdown (Q
BD) and the residual Q
BD. This difference, ΔQ
BD, corresponds to the plasma-induced damage to the oxide and to the accumulation of conduction current from the plasma into the oxide. It is shown experimentally that the plasma-induced damage ΔQ
BD increases in proportion to the antenna ratio (exposed antenna area/gate area). The ΔQ
BD of the antenna capacitor depends not on the device structures such as the gate oxide thickness, but on the plasma process conditions.
Characterization of Dynamic Behaviour of Metal-Semiconductor-Metal Photodetectors by Correlation Technique
Authors: Sickmöller Markus , Peter Urbach Peter Urbach , Wolfgang Kowalsky Wolfgang Kowalsky
Published: October 2002

The frequency response, linearity, and sensitivity of metal-semiconductor-metal (MSM) photodetectors are investigated. A new measurement technique is presented for examination of the dominant effects on current transport. The technique is based on optical excitation of a device by subsequent pulses of varying delay and on correlation of the pulse responses. In combination with time domain measurements an efficient technique for material and device optimization is attained. Characterization of the MSM-photodetectors results in a short risetime (800 fs) and pulse width (9 ps) and excellent linearity using n-type epitaxial layers. In contrast to semiinsulating layers no pulse tails are observed.
Future Ultra-Large Scale Integration: Transport Physics in Semiconductor Nanostructures
Authors: Ferry David K. , Yukihiko Takagaki Yukihiko Takagaki , Jing-Rong Zhou Jing-Rong Zhou
Published: October 2002

The progress in Si ULSI, and the parallel progress in GaAs LSI, has pushed the gate length in current devices toward 0.1 µm. Research laboratories have gone even further, and FETs with gate lengths as short as 20 nm have heen demonstrated. It is apparent that within the next decade or so, devices with gate lengths approaching this scale will be made in the production environment. These devices are likely to be susceptible to new physical effects that are now being studied in nanostructures, or mesoscopic devices as they are usually called. The first new effect, already seen in the short-gate length devices, is tunneling through the gate depletion region. In this paper, we try to summarize the major physical effects, some approaches to studying them, and the role they may play in future industrial devices.
Microhardness of Indium Nitride Single Crystal Films
Authors: Qixin Guo Qixin Guo , Akira Yoshida Akira Yoshida
Published: October 2002

Indium nitride epitaxial layers were grown by microwave-excited metalorganic vapor phase epitaxy. Microhardness of the films was measured. The hardness value has been extracted from the curve of depth of indentation vs the applied load, and determined to be 1000±50 kg/mm2.
Fabrication of Less Than a 10 nm Wide Polycrystalline Silicon Nano Wire
Authors: Wada Yasuo , Kure Tokuo , Yoshimura Toshiyuki , Sudo Yoshimi , Kobayashi Takashi , Goto Yasushi , Seiichi Kondo Seiichi Kondo
Published: October 2002

This paper reports a fabrication technology of polycrystalline silicon (poly-Si) “slit nano wire”, with dimensions of less than 10 nm. The processing procedures consist of a 100 nm electron beam lithography, precision dry etching, conformable deposition of silicon dioxide layer, slit etching, conformable deposition of doped amorphous silicon (a-Si) layer and etch back. The resulting poly-Si “slit nano wire” layer measures less than 10 nm in width as ascertained by a cross section transmission electron microscope (X-TEM). A possible application of the “slit nano wire” to a future optoelectronic devices is also discussed.
Ultrafine Fabrication Technique for Hot Electron Interference/Diffraction Devices
Authors: Hiroo Hongo Hiroo Hongo , Yasuyuki Miyamoto Yasuyuki Miyamoto , Jun Suzuki Jun Suzuki , Miyako Funayama Miyako Funayama , Takenori Morita Takenori Morita , Kazuhito Furuya Kazuhito Furuya
Published: October 2002

We proposed a device for observing hot electron interference by a double slit. For this purpose we had refined and improved the fabrication techniques, especially electron beam lithography; the alignment of electron beam lithography before and after crystal growth with accuracy of 100nm was reported for the first time. We could form detection electrodes of fine pitch on a narrow mesa structure. The formation of a 50-nm-pitch InP buried structure was also reported.
Effect of Surface Treatments after HF Etching on Oxidation of Si
Authors: Masatoshi Egawa Masatoshi Egawa , Hideaki Ikoma Hideaki Ikoma
Published: October 2002

Oxidation of the Si surfaces treated in various solvents after HF etching was investigated by means of the Schottky diode characteristics and X-ray photoelectron spectroscopy (XPS). The solvents employed were deionized water, ethanol ( C2H5OH), trichloroethylene ( CHCl:CCl2), 1,1,1-trichloroethane ( CH3CCl3), dichloromethane ( CH2Cl2) and acetone ( CH3COCH3). The effect of rinsing of the Si substrate in deionized water under a reduced pressure was also studied. The XPS data showed that the Si surface is oxidized the most in acetone. The degree of oxidation was the next highest in deionized water and then in ethanol. On the other hand, Si oxidation was substantially suppressed in solvents which do not include oxidant groups such as OH and CO. In deionized water under reduced pressure, oxidation was also considerably retarded. A possible oxidation kinetics are proposed to explain the experimental results. In this model, co-existence of both oxidant groups such as OH radicals and dissolved oxygen in the solvent is assumed to enhance oxidation. First OH radicals attack the Si-F and/or the Si-H bonds on the Si surface, resulting in the formation of the unterminated and the OH-terminated Si surface. Then, the Si surface is predominantly oxidized further by dissolved oxygen. Hence, oxidation can efficiently be suppressed by removing either the oxidant group or dissolved oxygen. This is in good agreement with the experimental results. The oxidation kinetics in acetone is also speculated.
Oxide-Phase Simulated Thermodynamics and Calculation of Thermochemical Properties of Compounds Auxiliary to Y–Ba–Cu–O High Tc Superconductors*
Authors: Šesták Jaroslav , Moiseev German K. , Tzagareishvili Demna S.
Published: October 2002

Evaluation methods for the estimation of standard enthalpy and entropy of formation, the temperature dependence of heat capacity and the temperature and heat of melting are shown for a generalised description of oxides. The calculation is applied to an actual simulation of the thermochemical data of real and hypothetical compounds for the following Y:Ba:Cu ratios: 123, 112, 213, 235, 133, 223, 135, 247, 124, 125, 516, 145, 146, 415, 132, 153, 312, 385, 163, 232, 143, 212, 122, 211, 121, 152, 131, 221, 321 and 142.
Hysteretic Josephson Junction Behavior of Ba1-xKxBiO3 Grain Boundary Junctions Using SrTiO3 Bicrystal Substrates
Authors: Takami Tetsuya , Kuroda Ken'ichi , Kataoka Masayuki , Wada Yukihiko , Terada Kumi , Tanimura Junji , Kazuyoshi Kojima Kazuyoshi Kojima , Masahiro Nunoshita Masahiro Nunoshita
Published: October 2002

We have fabricated Ba1-
x

K

x

BiO3 artificial grain boundary junctions with low resistance on a SrTiO3 bicrystal substrate. These junctions show hysteretic junction behavior with a clear superconducting energy gap structure and Josephson current. The area resistance was low; it ranged from 5.2×10-8 to 2.0×10-5 Ω ·cm2. The I
c
R
n product of the 20-µm-wide junction was 3.5 mV at 4.2 K. The gap voltage increased as the heater temperature increased and reached about 8 mV. A weak magnetic field applied normal to the substrate induced a Fraunhofer-type pattern.
C K-Edge X-Ray Absorption Near-Edge Structure of Carbon Nanotubes
Authors: Imamura Motoyasu , Shimada Hiromichi , Matsubayashi Nobuyuki , Yumura Motoo , Uchida Kunio , Oshima Satoshi , Kuriki Yasunori , Yoshimura Yuji , Toshio Sato Toshio Sato , Akio Nishijima Akio Nishijima
Published: October 2002

C K-edge X-ray absorption near-edge structure of the carbon nanotubes was measured by monitoring the total electron yield from the sample. The spectrum shows similar features to those of graphite except the feature between the lowest anti-bonding π and σ bands called the interlayer band.
Giant Magnetoresistance in Bulk Cu-Rich Co–Cu, Co–Ni–Cu and Fe–Ni–Cu Granular Alloys
Authors: Takeda Hideki , Kataoka Noriyuki , Shimada Kazuaki Fukamichi
Published: October 2002

Magnetoresistance has been investigated for bulk Cu-rich Co–Cu and Co–Ni–Cu and Fe–Ni–Cu granular alloys prepared by aging and plastic deformation. Giant magnetoresistance (GMR) is observed in these bulk alloys in the process of phase separation and anisotropy in GMR for Fe5Ni15Cu80 alloy aged at 500° C for 170 min is obtained by compression.
Crystal Structural Change of Poly(3-Alkylthiophene) Induced by Iodine Doping as Revealed by X-Ray Diffraction and Infrared/Raman Spectroscopic Measurements*
Authors: Tashiro Kohji , Minagawa Yasuhisa , Kobayashi Masamichi , Morita Shigenori , Kawai Tsuyoshi , Yoshino Katsumi
Published: October 2002

Based on the X-ray fiber diagram, polarized infrared and Raman spectra, the crystal structural model of iodine-doped poly(3-alkylthiophene) has been proposed: polythiophene chains are displaced along the chain axis to give the tunnels extending along the b axis, in which the I-
5 ions are mainly intercalated. The resultant charge transfer between thiophene rings and iodine molecules is considered to give polaron and bipolaron with intense transition dipole moments along the chain axis, as judged from the infrared dichroism.
Comparison of GaAs Facet Formation on Patterned Substrate during Molecular Beam Epitaxy and Migration Enhanced Epitaxy
Authors: Takumi Yamada Takumi Yamada , Yoshiji Horikoshi Yoshiji Horikoshi
Published: October 2002

We compare the film thickness profile and facet formation of GaAs films grown on a patterned substrate by migration-enhanced epitaxy (MEE) and by molecular beam epitaxy (MBE). The film thickness profile indicates that the Ga diffusion length during MBE growth decreases as the As pressure increases. In contrast, the diffusion length during MEE growth is independent of the As pressure. The facets resulting from MBE and MEE differ greatly. The dominant facet produced by MBE is in the (111)B plane, whereas (110), (113)B and (221)B are the most observable facet planes resulting from MEE. From these results, it is found that Ga atoms migrate to occupy every available site on each plane, with excess atoms moving to other index planes in MEE growth.
Ablation Plasma Temperature Produced by Intense, Pulsed, Ion-Beam Evaporation
Authors: Kang Xiangdong , Katsumi Masugata Katsumi Masugata , Kiyoshi Yatsui Kiyoshi Yatsui
Published: October 2002

Characteristics of the ablation plasma produced by an intense, pulsed, ion-beam evaporation which has been known to be very effective in preparing thin films have been evaluated experimentally by measurement of the ion flux. Using the data of ion flux, the ablation plasma temperature (T
0) is deduced by an analytic one-dimensional hydrodynamic solution. From the measurement of the ion-beam voltage and the ion-beam current density, the energy deposition per one atom (E
d) is estimated. The dependence of T
0 vs E
d is studied experimentally and compared with that derived theoretically. Reasonable agreement is obtained between them.
Observations of Suspension and Levitation Effects of Bulk High-Tc Superconductors in Microgravity Experiments
Authors: Matsuura Kiyotaka , Homma Norio , Sawada Nobuyuki , Tsuchimoto Masanori , Yamaya Kazuhiko , Honma Toshihisa
Published: October 2002

We were successful in observing suspension and levitation effects of bulk high-T
c superconductors (HTSCs) with a permanent magnet in microgravity experiments. Different results from experiments on Earth have been observed for a sintered Y–Ba–Cu–O sample levitated above a ring shape magnet. However, a melt processed sample showed no difference in suspended and levitated positions both on Earth and in microgravity. The different motions between sintered and melt processed HTSCs in microgravity can be explained by the difference in magnitude of the pinning force. It is shown that melt processed HTSCs for applications of suspension and levitation effects can be employed in space as on Earth.
Recorded Magnetization Structures and Noise Characteristics of CoCr Alloy Longitudinal Thin-Film Media
Authors: Honda Yukio , Suzuki Mikio , Tomiyama Futoshi , Matsuyama Hideo , Inaba Nobuyuki , Koike Kazuyuki , Masaaki Futamoto Masaaki Futamoto
Published: October 2002

Magnetic force microscopy and spin-polarized scanning electron microscopy are used to study the relationship between the reproduced noise properties and the recorded magnetization structures of longitudinal recording media. Magnetically continuous areas cross-linked between the neighboring recorded bits are observed when the linear recording density is increased to greater than 100 kFCI (Flux Change per Inch). The magnetization transition for a randomly oriented medium tends to form an intermittent magnetization transition with a size similar to that of magnetic clusters. This process is related to the relatively high DC-erased noise characteristics. High Cr content in CoCr-alloy media and magnetic anisotropy along the circumferential direction contribute to reducing medium noise possibly through the reduction in size and/or the oriented magnetic distribution of the magnetic clusters.
Electron Spin Resonance Image of Annealing under Thermal Gradient: Chemical Vapor Deposition Poly-Silicon Film
Authors: Motoji Ikeya Motoji Ikeya , Masahiro Yamamoto Masahiro Yamamoto
Published: October 2002

The spatial distribution of dangling bonds in a CVD poly-silicon film has been measured using a microwave scanning electron spin resonance (ESR) microscope. Uniformity of the spin concentration was imaged on a CRT display. An ESR image caused by thermal annealing of dangling bonds under known spatial temperature distribution (thermal gradient) for an annealing time t
a gives an intensity at each pixel (i,j) corresponding to each temperature, T

i,j
. The parameters, such as activation energy E and frequency factor ν o, can be obtained in a short period of time by plotting the decay time τ
i,j
from the intensity ratio I/I
o, i.e., τ
i,j
=-t
a/ln
(I/I
o)
i,j
against the reciprocal temperature 1/T

i,j
.
Numerical Analysis of Current Modulation in Optically-Controlled Field-Effect Transistor
Authors: Yukio Shimizu Yukio Shimizu , Kazuhiko Shimomura Kazuhiko Shimomura
Published: October 2002

Current modulation of an optically-controlled field-effect transistor using the field-screening effect of photogenerated carriers is numerically calculated. When the optical input power is 1 mW, more than 6 mA of current modulation can be obtained in this device.
Oxygen Microclusters in Czochralski-Grown Si Probed by Positron Annihilation
Authors: Uedono Akira , Kawano Takao , Wei Long , Tanigawa Shoichiro , Ikari Atsushi , Kawakami Kazuto , Itoh Hisayoshi
Published: October 2002

Trapping of positrons by oxygen microclusters in Czochralski-grown Si was studied. Lifetime spectra of positrons were measured for Si specimens annealed in the temperature range between 450°C and 1000°C. Positrons were found to be trapped by oxygen microclusters, and the trapping rate of positrons into such defects increased with increasing annealing temperature. In order to investigate the clustering behaviors of oxygen atoms in more detail, vacancy-oxygen complexes, V

n

O

m
(n,m=1, 2,…), were introduced by 3 MeV electron irradiation. The concentration of monovacancy-oxygen complexes V
O

m
(m=2, 3,…) increased with increasing annealing temperature. These facts were attributed that the oxygen microclusters, O

m
, were introduced by annealing above 700°C.
Photoluminescence from Si Network in SiO2-Doped Si Films
Authors: Kohno Kenji , Katayama Yukio Osaka
Published: October 2002

We report the photoluminescence from a Si network in SiO2-doped Si films. The peak position of the photoluminescence spectrum was at the photon energy of 1.08 eV and the full width at half-maximum (FWHM) was about 0.38 eV. It was speculated that this photoluminescence is due to multiple bound states induced by SiO2 islands, not to Si microcrystals with average diameter of 50 nm.
High-Performance Double δ-Doped Channel Si Metal Semiconductor Field-Effect Transistors
Authors: Wu San Lein , Shui Jinn Wang Shui Jinn Wang , Chen Chin Liu Chen Chin Liu
Published: October 2002

In this paper, we report the double boron δ-doped Si metal semiconductor field-effect transistors (MESFETs) grown by molecular beam epitaxy (MBE). It is found that when a double boron δ-doped layer has been used as a conducting channel, the devices exhibit the excellent property of not only higher drain-to-source saturation current (I
DSS) but also enhancement in extrinsic transconductance. MESFETs with a variety of boron doses of δ-doped layers have been fabricated and studied. The measured transconductance is enhanced two to five times over that of the single δ case.
A Study of Defect Formation Mechanism at Edges of Local Oxidation of Silicon Structure
Authors: Ishigami Shun-ichiro , Shinyashiki Hiroshi , Hisashi Furuya Hisashi Furuya , Takayuki Shingyouji Takayuki Shingyouji
Published: October 2002

We have investigated the effect of the oxygen concentration of the substrate upon defect formation at edges of the local oxidation of silicon (LOCOS) structure by preparing various kinds of substrate. It was found that the defect density was not correlated with oxygen concentration near the LOCOS-fabricated region and that no LOCOS defect was found when bulk defects were induced. The most probable model for the defect formation is proposed to be the combination of maximized tensile stress at LOCOS edges and agglomeration of ejected self-interstitials due to this stress, which is greatly affected by the existence of other strong sink sites such as bulk defects.
Gravity-Dependent Silicon Crystal Growth Using a Laser Heating System in Drop Shaft
Authors: Jōsuke Nakata Jōsuke Nakata , Ikuo Inagawa Ikuo Inagawa , Katsuro Yamamoto Katsuro Yamamoto , Hironori Honda Hironori Honda , Noriaki Kuratani Noriaki Kuratani , Shuhei Furuichi Shuhei Furuichi , Toru Noguchi Toru Noguchi , Masayuki Kudoh Masayuki Kudoh
Published: October 2002

Spherical silicon crystals were grown without a crucible within about 10 s under microgravity in a drop shaft. To perform crystal growth in a short period, a compact crystal growth system which can be installed in a drop capsule was developed. A CO2 laser with the output power of 25 W was focused to approximately 300 µm to heat the crystal seeds. We used silicon crystal rod arrays as seeds and moved the arrays with a motor-driven sliding mechanism. This method allowed us to observe variations of crystal growth when gravity changed successively from 1 G to microgravity in a single drop test.
Increase of Critical Thickness and Optical Emission Range in (InAs)1(GaAs)n Strained Short-Period Superlattices
Authors: Saito Daishiro , Yonezu Hiroo , Kawai Takahiro , Mikihiro Yokozeki Mikihiro Yokozeki , Kangsa Pak Kangsa Pak
Published: October 2002

The critical thickness and optical emission wavelength range of (InAs)1(GaAs)

n

strained short-period superlattices (SSPSs) grown on GaAs(100) substrates were investigated by reflection high-energy electron diffraction, transmission electron microscopy and photoluminescence (PL). When the (InAs)1(GaAs)

n

SSPSs were grown at a substrate temperature of 420°C, the critical thickness was increased up to about ten times as large as that of InGaAs alloys except for the (InAs)1(GaAs)1 SSPS. The wavelength range of the PL peak was markedly increased in the (InAs)1(GaAs)

n

SSPS/GaAs single quantum wells (SQWs), compared with that in the InGaAs/GaAs SQWs. When the (InAs)1(GaAs)

n

SSPS was grown at 500°C, the longest experimental wavelength was 1.16 µm at room temperature. A wide range of PL peak wavelengths from 0.87 to 1.23 µm can be expected at room temperature in the (InAs)1(GaAs)

n

SSPSs, if nonradiative recombinations can be reduced with a low temperature growth of 420°C.
Hall Mobility of Low-Temperature-Deposited Polysilicon Films by Catalytic Chemical Vapor Deposition Method
Authors: Matsumura Hideki , Tashiro Yoshinari , Sasaki Kimihiro , Furukawa Seijiro
Published: October 2002

Nondoped polysilicon films are deposited at temperatures as low as 260°C by the catalytic chemical vapor deposition (cat-CVD) method using a silane and hydrogen gas mixture. Electrical properties such as the Hall mobility are investigated for various measuring temperatures. It is found that the Hall mobility depends on the hydrogen flow rates during deposition and is larger than 20 cm2/V·s, and that the barrier height at the grain boundary appears to be lower than the thermal activation energy at room temperature.
Electric Field Sensitive Moving Hot Spot in GdBa2Cu3O7- δ Ceramics
Authors: Okamoto Tomoichiro , Ben Huybrechts Ben Huybrechts , Masasuke Takata Masasuke Takata
Published: October 2002

An electric field sensitive moving hot spot appeared on a GdBa2Cu3O7-δ bar with following dimension, 0.65 mm×0.65 mm×40 mm, when a dc voltage of 7 V was applied at room temperature. The spot moved to the negative electrode, and the direction of movement could be reversed time after time by switching the positive and negative electrode. The average velocity of the hot spot was 1.9 mm/min. The spot size increased with increasing voltage. This phenomenon is believed to be related to the ionic conduction by oxygen.
Fine Resolution of Energy Structures of Large Molecules in Solution by Coherent Population-Grating Spectroscopy
Authors: Souma Hirotoshi , Horie Chuji , Hoshi Masayuki , Tashiro Taeko Daiguji
Published: October 2002

We have succeeded in observing finely resolved spectra in the spectral regions of absorption and emission bands of cresyl violet in ethanol, by means of population-grating spectroscopy based on four-photon parametric mixing. The inhomogeneous width is investigated in terms of the excitation frequency dependence. The energy separation and the homogeneous width are also analyzed by assuming that the observed fine bands consist of several Lorentzian lines. It is revealed that the observed spectra reflect the detailed vibrational and vibronic structures of molecules. This high-resolution spectroscopy can be readily applied to more general disordered systems in the condensed phase.
Unique Dynamic Characteristics of Electroluminescent Diode with Superlattice Structure Utilizing Cyclopentadiene Derivative and Aromatic Diamine
Authors: Ohmori Yutaka , Yoshida Masayoshi , Morishima Chikayoshi , Akihiko Fujii Akihiko Fujii , Katsumi Yoshino Katsumi Yoshino
Published: October 2002

The pulse response of an organic electroluminescent (EL) diode with superlattice structure which consists of alternating layers of cyclopentadiene derivative and aromatic diamine has been investigated. The EL emission from the superlattice structure with increased layer thickness shows fast response, whereas that from reduced layer thickness shows both slow response and decay upon application of a rectangular-shaped pulse current. The origin of the slow response and decay has been discussed in terms of the layer thickness and the energy band model of the superlattice structure.
Efficient Energy Transfer in Organic Multilayer Structure Utilizing 8-Hydroxyquinoline Aluminum and Aromatic Diamine
Authors: Fujii Akihiko , Morishima Chikayoshi , Yoshida Masayoshi , Yutaka Ohmori Yutaka Ohmori , Katsumi Yoshino Katsumi Yoshino
Published: October 2002

Photoluminescence from an organic multilayer structure utilizing 8-hydroxyquinoline aluminum ( Alq3) and aromatic diamine has been discussed in terms of the wavelength of the excitation light and the layer thickness. The photoluminescence intensity from Alq3 layers is enhanced in the thinner multilayer structure compared with the thicker one as a result of efficient energy transfer at the heterointerfaces. The mechanism behind the increase of photoluminescence intensity in the organic multilayer structure is discussed.
Study of Spin Dynamics and Electronic Structure in Polythiophene Heavily Doped with ClO-
4
Authors: Mizoguchi Kenji , Honda Makoto , Masubuchi Shin-ichi , Kazama Shigeo , Kiyoshi Kume Kiyoshi Kume
Published: October 2002

ESR line width was measured in polythiophene heavily doped with ClO-
4 as functions of both temperature and frequency. We studied the dynamics of charge carrier with spin. The temperature dependence was explained by the Elliott mechanism, indicating the existence of metallic electrons. The frequency dependence demonstrated that electron spins are in the state of diffusive motion in quasi-one-dimension. These experimental results were interpreted in a consistent way, yielding the parameters characteristic of the electronic structure like effective mass and mean free path.
TiO2 Thin Films Formed by Electron Cyclotron Resonance Plasma Oxidation at High Temperature and Their Application to Capacitor Dielectrics
Authors: Yoshio Abe Yoshio Abe , Takuya Fukuda Takuya Fukuda
Published: October 2002

Low-leakage-current rutile- TiO2 thin films were fabricated by electron cyclotron resonance (ECR) plasma oxidation of Ti thin films. Rutile- TiO2 thin films could be obtained at substrate temperatures above 280°C. A relative dielectric constant of about 120 was obtained at substrate temperatures above 390°C. Leakage current characteristics of the TiO2 thin films were improved by using high-temperature plasma oxidation and high-work-function electrodes. A leakage current of less than 1×10-8 A/cm2 at an applied voltage of 1.25 V was obtained for a Au/TiO2/Pt capacitor with SiO2 equivalent thickness of 4.9 nm.
Preparation of Ordered Vacancy Chalcopyrite-Type CuIn3Se5 Thin Films
Authors: Negami Takayuki , Kohara Naoki , Mikihiko Nishitani Mikihiko Nishitani , Takahiro Wada Takahiro Wada
Published: October 2002

Polycrystalline CuIn3Se5 films were successfully prepared by three-source coevaporation with controlling and shielding of the molecular beams from elemental sources. The CuIn3Se5 film exhibited good chemical homogeneity and an ordered vacancy chalcopyrite-type structure with lattice constants of a=5.742 Å and c=11.486 Å. High-resolution transmission electron microscopy showed that the CuIn3Se5 film had a columnar microstructure and each grain contained a high density of twins in {112} planes. The band-gap energy of the film was determined to be 1.23 eV from optical transmission measurements. The film showed n-type conduction and low conductivity of 3.7×10-7/ Ω·cm. These characteristics of the CuIn3Se5 film are compared with those of the chalcopyrite-type CuInSe2 film.
The Use of the Transfer Function in Dielectric Measurements by Time Domain Reflectometry
Authors: Casalini R. , A. Livi A. Livi , P. A. Rolla P. A. Rolla
Published: October 2002

The use of the transfer function to determine the permittivity by time domain reflectometry is discussed and proved by error analysis to be more accurate than previous methods. The transfer function, since it is determined by the simultaneous acquisition of the incident and reflected signals, is less sensitive to the fluctuations of the voltage step. Reliable and accurate results in a wide frequency interval (50 MHz–20 GHz) were obtained by a single measure.
Characterization of Au Thin Film by Glancing-Incidence and -Takeoff X-Ray Fluorescence Spectroscopy
Authors: Tsuji Kouichi , Shigeo Sato Shigeo Sato , Kichinosuke Hirokawa Kichinosuke Hirokawa
Published: October 2002

We have developed an experimental apparatus for a glancing-incidence and -takeoff X-ray fluorescence spectroscopy (GIT-XRF) to analyze thin films and material surfaces. In this method, the fluorescent X-rays from the thin film are measured at various incident and takeoff angles, and the thin film is cross-checked. Therefore, the GIT-XRF method allows for detailed characterization of the thin film.
Phase Controlled Scanning Force Microscope
Authors: Kikukawa Atsushi , Hosaka Sumio , Honda Yukio , Ryo Imura Ryo Imura
Published: October 2002

A noncontact scanning force microscope employing a novel tip height control system using phase lock technology has been developed. An oscillator using a cantilever as a mechanical resonator is used as a voltage controlled oscillator in a phase locked loop, and its output signal is phase locked to a high-precision signal source. Its most remarkable feature is that this tip height control is unconditionally stable. Thus, it was possible to realize the desired system response by adjusting the loop parameters. Its efficiency was demonstrated by imaging the surface of a magneto-optical disk at the lowest tip height which was impossible to achieve with a conventional servo technology.
Effect of Cu Addition to Ag Sheath on Properties of Powder-in-Tube-Processed Bi-2223 Tapes
Authors: Ahn Jung-Ho , Ha Kook-Hyun , Lee Soo-Young , Ko Jae-Wung , Hae-Doo Kim Hae-Doo Kim , Hyungsik Chung Hyungsik Chung
Published: October 2002

The effect of Cu addition to Ag sheath on superconducting and mechanical properties was investigated for Bi-2223/Ag composite tapes fabricated by the powder-in-tube process. Workability, mechanical strength and oxide/sheath interface morphology were improved considerably without deterioration ofTcorJcwhen using Ag-2.5 and 5 wt% Cu alloys as sheath materials.
Improvement in Magnetoresistance of Very Thin Permalloy Films by Post-Annealing
Authors: Funaki Hiroshi , Okamoto Satoshi , Osamu Kitakami Osamu Kitakami , Yutaka Shimada Yutaka Shimada
Published: October 2002

We prepared Ni80Fe20 films by the sputter-beam method and investigated their magnetotransport properties. The very thin film of 200 Å exhibited a high magnetoresistance of 3.5% after an appropriate post-annealing treatment. The improvement is due to the decrease of zero-field resistivity resulting from remarkable grain growth in the films. Taking into account diffusive electron scattering at the film surface, the magnetoresistance value is thought to be very close to that of the bulk.
Very Weak Dependence on Temperature of 980-nm InGaAs/InGaAsP/InGaP Lasers
Authors: Ohkubo Michio , Iwai Norihiro , Tetsuro Ijichi Tetsuro Ijichi , Takao Ninomiya Takao Ninomiya
Published: October 2002

The effects of mirror loss on the characteristic temperature T
0 were studied for 980-nm strained-layer InGaAs single-quantum-well graded-refractive-index separate-conlinement-heterostructure lasers with InGaP cladding layers. It was found that the lasers exhibited a very high T
0 of over 300 K and strong dependence on temperature with change in the mirror loss. Assuming the logarithmic current ( J) -gain ( G) relation G=G
0 ln(J/J
0), these phenomena could be interpreted using the behavior of the temperature dependence of G
0.
Non Lorentzian Line Shape Functions for Wavelength Tunable Laser Diodes
Authors: Andreas Dieckmann Andreas Dieckmann
Published: October 2002

The calculation of the phase noise and the power spectrum carried out for wavelength tunable laser diodes proves that its line shape cannot be approximated by the Lorentzian shape to determine the spectral linewidth. Since the shot noise in the tuning region, which contributes significantly to the laser phase noise, exhibits a bandwidth of about 100 MHz the line shape decreases stronger than expected from the corresponding linewidth. Therefore the noise power is smaller than calculated from a Lorentzian approximation.
Growth of Ultrathin Silver Films by Excimer-Laser-Induced Decomposition of Silver Acetate in Air
Authors: Yong-Feng Lu Yong-Feng Lu , Mikio Takai Mikio Takai , Takao Shiokawa Takao Shiokawa , Yoshinobu Aoyagi Yoshinobu Aoyagi
Published: October 2002

Excimer-laser-induced deposition of silver film from a silver acetate ( CH3COOAg) has been investigated. Ultrathin silver film with a thickness of nanometer order can be obtained by excimer-laser-induced decomposition of silver acetate in air. The decomposition reaction is photochemical. Smooth thin film without grains and other microstructures can be obtained by this process. Almost pure silver in the deposited thin film has been achieved. This method provides a way to grow silver thin film on different substrate materials such as Mn-Zn ferrite, glass and metals.
Electron Energy-Loss Spectra of Single-Shell Carbon Nanotubes
Authors: Kuzuo Ryuichi , Terauchi Masami , Saito Michiyoshi Tanaka
Published: October 2002

Transmission electron energy-loss spectra of single-shell carbon nanotubes were measured and compared with those of multishell carbon nanotubes and graphite. Two peaks due to the π plasmon and the π+σ plasmon were observed at 5.8 eV and 20.6 eV, respectively. The energy of the π plasmon takes a value between those of two kinds of multishell tubes. The energy of the π+σ plasmon is lower than those of multishell tubes and graphite by 2 eV and 6 eV, respectively. The 1s→π* and 1s→σ* transition peaks of the single-shell tubes are much broader than those of the multishell tubes and graphite. The reason for the broadening may be due to the strong curving of the graphitic sheets.
Characterization of p-Type Silicon Field Emitters
Authors: Sawada Kazuaki , Kun Ji Kun Ji , Takao Ando Takao Ando
Published: October 2002

The saturation current phenomenon of a p-type silicon field emitter is reported and the mechanism of this phenomenon is proposed. The current-voltage characteristics of these field emitters using n-type silicon follow the Fowler-Nordheim relationship. However, the emission current of the emitters using p-type silicon is saturated in a high field region, because maximum emission electrons are restricted by the electron generation rate at the surface. The saturation current is observed on the emitters with HF treatment, but it not without HF treatment. These results indicate that the saturation current depends on the surface state density.