bluuebunny/crossref_metadata_2025 huggingface dataset:
An Optimum Condition of Multipole Field for an ECR-Type Jon Source
Authors: Ishii Shigeyuki , Amemiya Hiroshi , Yanokura Minoru
Published: November 2005

A beam current including multiply charged ions was maximized by optimizing a plasma generated by ECRF (electron cyclotron range of frequency) microwave discharge in a hexapole-mirror magnetic field. The plasma density exceeded acritical value by one order of magnitude. From calculation of a plasma resonance equation it was disclosed that there exists a resonance zone for the overdense plasma. Experimentally, this plasma was obtained only when a magnetic flux surface involving the resonance zone nests within the plasma vessel.
High-Mobility Amorphous-Silicon MUS Transistors
Authors: Okada Hiroyuki , Uchida Yasutaka , Matsumura Masakiyo
Published: November 2005

Process conditions for gate oxide formation in amorphous-silicon MOS transistors have been investigated systematically. It was found that the n+ micro-crystal silicon layer just above the active transistor region should be removed before the gate oxidation at 250°C. Annealings in nitrogen ambient just after the oxidation and in hydrogen ambient after gate electrode evaporation were also effective. The highest field-effect mobility measured by the transistor fabricated under the optimum process conditions was about 4.8 cm2/Vs. Dynamic response characteristics have also been evaluated.
Depth Distributions of ESR Centers Induced in Fused Quartz by Gas-Discharges
Authors: Taniguchi Shizuo , Endo Tamio , Sugiyama Koichi
Published: November 2005

E'- and Al/H-centers were found by ESR in fused quartz exposed to glow discharges of H2, Ar, N2 and N2O gases. They distribute to a depth of 5 mm. The following introduction mechanisms are inferred. The E'-center is induced by ion bombardment and by reaction of discharge-produced hydrogen ion or atom with surface oxygen. An excitation by UV-light enhances diffusion of E'. AN/H-center, exhibiting a hyperfine structure, is induced by an association of aluminum impurity with hydrogen liberated from coexisting OH groups by the UV-ionization. It is partially induced also by penetration of the discharge-produced hydrogen species into the fused quartz.
Photo-Ionizalion Assisted Photo-CVD of Silicon Nitride Film by Microwave-Excited Deuterium Lamp
Authors: Tamagawa Kouichi , Hayashi Toshio , Komiya Souji
Published: November 2005

Silicon nitride films have been formed using a photo-CVD apparatus with a microwave-excited deuterium lamp. The BHF etching rate, 40–70 Å/ min, deposited at 320°C is lower by less than one-tenth than that deposited using a conventional low-pressure mercury lamp, indicating formation of a high density film. The deposition rate has been enhanced dramatically from 13 Å/min to 100 Å/min by incorporating the photo-ionization assisted effect, which is brought about by an ionization of a substrate surface, ions formed by collisions of reactant gases with photoelectrons and photo-ionized ions.
Improved Transconductance of AlGaAs/GaAs Heterostructure FET with Si-Doped Channel
Authors: Inomata Hiroki , Nishi Seiji , Takahashi Seiichi , Kaminishi Katsuzo
Published: November 2005

The n+ self-alignment process with a furnace annealing was applied to the fabrication of heterostructure FETs. Maximum transconductance of 350 mS/mm and the K-value of 430 mA/V2 mm were obtained for the HMT structure (L
g=0.7 µm) at room temperature. An intentionally doped channel structure was also studied. An extremely high transconductance of 440 mS/mm and an extremely high K-value of 520 mA/V2 mm were obtained for this structure, suggesting that the performances of HEMTs mainly depend on the capacitance between the gate electrode and the confinedelectron gas.
SIMS Study of Si–Be Co-doping Effects for Suppression of Compositional Disordering in AlGaAs–GaAs Superlattices
Authors: Kobayashi Junji , Nakajima Masato , Fukunaga Toshiaki , Takamori Takeshi , Ishida Koji , Nakashima Hisao , Ishida Koichi
Published: November 2005

We have studied the Si–Be co-doping effect for the suppression of the compositional disordering of AlGaAs–GaAs superlattices (SLs) by SIMS. The Si–Be co-doping is found to suppress the fast Si diffusion which is ascribed to the formation of (SiIII–SiV) pairs. The possible mechanism is that the formation of (BeIII–SiIII) pairs prevents that of (SiIII–SiV) pairs. The suppression of the Si fast diffusion impedes the SL disordering. The threshold concentration of Be required to suppress the SL (300 Å periodicity) disordering is around 2×1018 cm-3 in the case of 1.5×1019 cm-3 Si concentration.
Images of Barrier Layer of Anodic Aluminum Oxide in Air Obtained with Scanning Tunneling Microscope
Authors: Morita Seizo , Itaya Kingo , Mikoshiba Nobuo
Published: November 2005

We prepared anodic aluminum oxide (Al2O3) with a barrier layer. By evaporating Pt–Pd thin films on the barrier layer, surface images of several barrier layers were obtained even in air using a scanning tunneling microscope. From STM images, we found that the barrier layer consists of many domains. The measured size of domains agreed well with the estimated values from SUM photographs, though the depth of the domain walls depends on the thickness of the evaporated Pt–Pd film.
Efficient Si Planar Doping in GaAs by Flow-Rate Modulation Epitaxy
Authors: Kobayashi Naoki , Makimoto Toshiki , Horikoshi Yoshiji
Published: November 2005

During the growth of GaAs layers by flow-rate modulation epitaxy (FME), triethyl gallium and arsine are alternately supplied on the GaAs substrate. Thus, the Ga atomic surface and As atomic surface appear alternately at the growing surface. These atomic surfaces exhibit very different characteristics in capturing impurity atoms. By supplying 10% silane diluted with hydrogen gas at a flow-rate of 20 cc/min for one second, we have succeeded in obtaining extremely high Si planar doping levels with the maximum sheet carrier density of 1.1×1013 cm-2 occurring at the low growth temperature of 550°C.
Hydrogen-Reduced Carbonization by Acetylene Discharges
Authors: Sugai Hideo , Urano Shuichi , Amemiya Susumu , Ishikawa Kazuyuki , Noda Nobuaki , Okuda Takayoshi
Published: November 2005

A pure acetylene discharge has been used to deposit thin carbon films onto the wall of a toroidal device, demonstrating in situ carbonization of magnetic fusion devices. The H-atom content of films deposited at different wall temperatures is measured by IR absorption, ERD, and 15N nuclear reaction techniques. Compared with a methane discharge, the acetylene discharge gives a rapid deposition rate, a high C-atom density, and a low H-atom film density. The 50% reduction of H/C atomic ratio is particularly desirable to suppress the enormous hydrogen desorption in tokamak discharges.
Coordination Number of Doped Boron Atoms in Photochemically-Deposited Amorphous Silicon Studied by X-Ray Photoelectron Spectroscopy
Authors: Kazahaya Tomio , Hirose Masataka
Published: November 2005

A new insight on the chemical bonding features of doped boron atoms in hydrogenated amorphous silicon (a-Si:H) has been obtained from a chemical shift in the binding energy of B(1s) core level electrons. It was found that the B(1s) X-ray photoelectron spectrum can be deconvoluted to the two Gaussian peaks at energies of 186.6 and 187.7 eV, which are respectively attributed to electrons emitted from three- and four-fold coordinated boron atoms in silicon matrix. The conductivity is clearly correlated with the concentration of four-fold coordinated boron atoms.
Fully Self-Aligned Amorphous-Silicon MUS Transistors
Authors: Okada Hiroyuki , Uchida Yasutaka , Zhang Hongyon , Sugiura Osamu , Matsumura Masakiyo
Published: November 2005

Fully self-aligned amorphous-silicon MOS transistors have been proposed and fabricated for the first time. All positions, i.e., an active region, source and drain region, contact holes and metal electrodes are determined by only one photo-mask for the top silicon-nitride layer of a multi-layer structure deposited successively on a glass substrate. The total number of photolithographic steps is 6. On-off current ratio and the maximum field-effect mobility of the fabricated transistor are 105 and 0.25 cm2/Vs, respectively.
Study of Thermal Stability of LaB6 and GaAs Interfaces by High Energy Ion Scattering
Authors: Uchida Yoko , Yokotsuka Tatsuo , Narusawa Tadashi , Nakashima Hisao
Published: November 2005

Thermal stability of LaB6/GaAs(001) interface has been studied using displacement-sensitive high energy ton scattering analysis. The samples were prepared by LaB6 electron beam evaporation on chemically etched GaAs and GaAs-c(4×4) grown by MBE. The GaAs interface structure approaches the bulk-like one because of relaxation of surface atoms due to annealing and no appreciable reaction at the LaB6/GaAs(001) interface is observed even after annealing at 850°C. These results provide firm evidence that the LaB6/GaAs(001) interface is thermally stable.
Growth of InP and InGaAs by MO-Chloride VPE
Authors: Kondo Susumu , Amano Toshimasa , Nagai Haruo
Published: November 2005

A novel chloride vapor phase epitaxial (VPE) growth of InP and InGaAs is performed using metal organic compounds instead of III group metal sources. The effect of an introduced partial pressure ratio between TMI and PCl3 on the InPgrowth features was investigated and analyzed thermodynamically. Typical values of carrier concentration and mobility for both of undoped InP and InGaAs at 77 K range in 4-15×1015 cm-3 and 10000–15000 cm2/Vs, respectivety.
Electroluminescence of Perylene Films with a Conducting Polymer as an Anode
Authors: Hayashi Seiji , Etoh Hiroyuki , Saito Shogo
Published: November 2005

We have investigated the electroluminescence (EL) of perylene films having different combinations of electrodes. Excellent hole injection current was obtained in the EL cell with a poly(3-methylthiophene) film as an anode. The threshold voltage for the EL remarkably decreased in the same cell.
Picosecond HEMT Pholodetector
Authors: Umeda Tokuo , Cho Yoshio , Shibatomi Akihiro
Published: November 2005

A short and narrow gate GaAs/AlGaAs MESFET with a HEMT structure was tested as a picosecond photodetector. Its impulse response was measured by the autocorrelation technique and found as fast as 22 ps in FWHM.
Thermal Conductivity of Diamond Films Synthesized by Microwave Plasma CVD
Authors: Ono Akira , Baba Tetsuya , Funamoto Hiroyuki , Nishikawa Akira
Published: November 2005

A measurement method is developed for the thermal conductivity of thin films in the direction parallel to the surface. Measurements are made between 100°C and 130°C for diannond films from 7 µm to 30 µm thick that are synthesized from a gas phase of methane/hydrogen mixture by microwave plasma chemical vapor deposition, The thermal conductivity of diamond films increases rapidly with decreasing concentration of methane. The highest thermal conductivity ever obtained in this experiment is about 1000 Wm-1 K-1. The thermal conductivity and Raman spectrum are compared under different synthesis conditions.
Be Doping Effect on Growth Kinetics of GaAs Grown by MBE
Authors: Iimura Yasufumi , Kawabe Mitsuo
Published: November 2005

In order to investigate the Be doping effect on growth kinetics of GaAs grown by molecular beam epitaxy, measurements of the intensity oscillations in reflection high-energy electron diffraction and of the depth profile of Be by secondary ion mass spectroscopy have been carried out. Be has been accumulated at the growth front and the accumulated Be has induced surface roughness. A critical surface concentration of Be to affect the growth kinetics has been estimated at 0.02 monolayer. The mechanism for the Be-induced roughness at the growth front is discussed.
High-Resolution Electron Microscope Study of Silicon on Insulator Structure Grown by Lateral Solid Phase Epitaxy
Authors: Kawarada Hiroshi , Ueno Tomo , Kunii Yasuo , Horiuchi Shigeo , Ohdomari Iwao
Published: November 2005

Structural study of L-SPE grown (100)Si/SiO2 interface after high temperature annealing in Ar has been carried out using HRTEM. On an atomic scale the roughness at the (100)Si/ SiO2 interface is less than a few lattice planes (0.5 nm). When micro-twins are present in the L-SPE layer, almost all of them nucleate at the Si/SiO2 interface. This is evidence for the formation of {111} growth planes near the interface during the L-SPE growth. The twin/SiO2 interface is not parallel to the substrate and forms atomically sharp {111} facets. This fact indicates that the interfacial energy of the (111)Si/SiO2 interface is lower than that of the (100)Si/SiO2 in solid phase.
A Blazed Grating Fabricated by Synchrotron Radiation Lithography
Authors: Kodate Kashiko , Okada Yoshiko , Kamiya Takeshi
Published: November 2005

A 1.25 µm pitch grating with a blazed angle of 45° is successfully fabricated using a deep UV region of synchrotron radiation lithography. The highest diffraction efficiency of 50±5% is obtained at normal incidence. The present technology is suitable for fabricating submicron grating devices in opto-electronic systems.
Metastable Phases in Sputtered Fe–Te Films
Authors: Chiba Kiyoshi , Ino Hiromitsu
Published: November 2005

In a binary alloy of Fe–Te, several new metastable phases were obtained by sputter deposition in the compositional range of 0 to 50 at % Te. These phases were CsCl type (B2) of Fe primary solid solution, amorphous Fe–Te, layered Fe–Te, and mixtures of equilibrium crystalline phases. Their structures were studied by X-ray diffraction. A first sharp diffraction peak (FSDP) associated with diffused halos exists in an alloy at around 30 at% Te, which is suggestive of aglass structure of medium-range order.
Anomalous Dielectric Behaviour in Biphenyl Ester Series of Ferroelectric Liquid Crystals
Authors: Mikami Naoko , Higuchi Ryo-ichi , Sakurai Takao , Ozaki Masanori , Yoshino Katsumi
Published: November 2005

In ferroelectric liquid crystals of biphenyl ester series with alkylcarbonyloxy (C
n
H2n+1COO) chain length n longer than 9 exhibit anomalous dielectric behaviour. The spontaneous polarization becomes 0, even in the chiral smectic-C phase, at around 30°C at which the reversal of the sign of the tilt angle is observed, indicating a change of the sign of the spontaneous polarization. The origin of this anomalous behaviour is also discussed in terms of molecular interactions.
Anomalous Switching Behavior of a Ferroelectric Liquid Crystal with Negative Dielectric Anisotropy
Authors: Orihara Hiroshi , Nakamura Kohji , Ishibashi Yoshihiro , Yamada Yuichiro , Yamamoto Norio , Yamawaki Masao
Published: November 2005

The switching characteristics of a ferroelectric liquid crystal with negative dielectric anisotropy were studied. An anomalous behavior has been found in the applied voltage dependence of the switching time, i.e., with increasing applied voltage in the low voltage region the switching time decreases monotonically, while in the high voltage region it attains a minimum and then increases.
Electroslatie Contribution to the Distortion Free Energy Density of Ferroelectric Liquid Crystals
Authors: Okano Koji
Published: November 2005

In a chiral smectic C liquid crystal, a bend type deformation of the C-director induces a polarization charge. We have shown that due to the screening effect by impurity ions the free energy of the electrostatic interaction of the polarization charge is renormalized into the distortion free energy density associated with the bend mode of the C-director. The renormalized elastic constant depends on the electrostatic screening length (i.e., the amount of impurity ions) as well as on the magnitude of the spontaneous polarization.
Nondestructive Detection of Small Voids in Solids by Transmission Electron Spectrometry
Authors: Okuda Shuichi , Tabata Tatsuo , Seiyama Takeyoshi
Published: November 2005

A nondestructive method for detecting small voids in solids by means of transmission electron spectrometry has been investigated. With collimated probe-beams of 10-MeV electrons, transmission momentum-spectra have been measured for model samples of silicon carbide 5-mm thick in which a slit-type 200 or 600 µm by 200 µm cavity simulated a void. Between the spectra measured for regions with and without the cavity, small difference has been observable. The results have shown that, according to the change in the spectra, voids 200 µm or smaller can be detected by the present method.
The 1.52µm Absorption Band in Optical Fibers Induced by Hydrogen Treatment
Authors: Nagasawa Kaya , Todoriki Tsuyoshi , Fujii Takashi , Ohki Yoshimichi , Hama Yoshimasa
Published: November 2005

Electron spin resonance (ESR) and optical absorption of optical fibers irradiated by γ-rays and treated by hydrogen gas were observed. A hyperfine structure (hfs) in ESR spectrum not previously reported was found. It is induced byhydrogen treatment only when peroxy radicals are observed. The hfs is explainable by assuming that peroxy radicals form a hydrogen bond with a hydrogen molecule. The 1.52 µm band appears in the same fibers as does the hfs, and diminishes at 90°C in a similar manner to the hfs. This band is thought to be caused by a hydrogen molecule that forms a hydrogen bond with a peroxy radical.
Nitrogen-Oxygen Complexes as Shallow Donors in Silicon Crystals
Authors: Suezawa Masashi , Sumino Koji , Harada Hirofumi , Abe Takao
Published: November 2005

Optical absorption of silicon crystals involving nitrogen and oxygen is investigated at low temperature. New absorption lines are found and attributed to seven defect levels that act as shallow donors. The characteristics of the absorption lines are well described by the effective mass approximation. Five among these seven levels are related to complexes of nitrogen and oxygen atoms.
Fine Structure of a Deep Photolumineseence Band Related to Oxygen in LEC-GaAs
Authors: Kazuno Tadao , Sawada Yuji , Yokoyama Takeshi
Published: November 2005

A fine structure is discovered in a 0.63 eV photoluminescence emission band in GaAs at 4.2 K under the excitation of the 5145 A line of an Ar-laser. The fine structure is interpreted to be due to the phonon side-bands of the oxygen-related radiative transition. The emission band is stronger in both Ga2O3 doped LEC–GaAs and undoped LEC–GaAs grown using wet B2O3, as an encapsulant than in conventional undoped GaAs grown by dry B2O3 encapsulant. Nonlinear least squares fitting of the band gives 6.7 for Huang-Rhys coupling constant, 0.0237 eV for the coupled phonon energy and 0.16 eV for the Franck-Condon shift. Thermal energy of oxygen related level is evaluated as 0.74±0.02 eV below theconduction band.
Boron and Phosphorus Jon Emissions from a Cu–P–Pt–B Liquid Metal Ion Source
Authors: Umemura Kaoru , Ishitani Tohru , Tamura Hifumi
Published: November 2005

A liquid metal ion source using a Cu–P–Pt–B alloy has been developed to emit both boron and phosphorus ions for maskless ion implantation. The relative flux intensities of B+ and P2+ to total ion flux are 13 and 15%, respectively, at total ion current, I
T, of 30 µA. These ions are separable by mass separator with a low mass-resolving power of m/Δm≃10. A source lifetime of more than 30 hours has been achieved at I
T=10∼50 µA.
Characteristics of a Semi-Insulating InP:Fe Wafer
Authors: Kim H.K. , Hwang J.S. , Noh S.K. , Chung C.H.
Published: November 2005

A semi-insulating InP:Fe wafer has been investigated by Hall effect measurements. A 2-inch semi-insulating InP:Fe wafer was divided into 63 squares of 5×5 mm2, and 17 samples were selected along the <011> and <011̄> directions to determine the characteristics of the whole wafer. The resistivity, Hall mobility, Hall coefficient, and carrier concentration at room temperature were in the range of 2.1–4.6×107 ohm·cm, 1700–3000 cm2/V·sec, 5.5–14×1010 cm3/coul, and 4.5–11×107 cm3, respectively. From the measured Hall mobilities the impurity scattering mobilities were calculated and the neutral impurity concentration was estimated as to be 0.85–2.6×1016 cm-3. The resistivity distribution revealed that the 17 samples can be classified into 3 groups.
Indium Isoelectronic Doping Influence on Etch Pit Density in GaAs Layers Grown by Vapour Phase Epitaxy
Authors: Coronado M.López , Abril E.J. , Aguilar M.
Published: November 2005

In this letter we report the In doping of GaAs layers grown by VPE (chloride method) using a Ga/In alloyed source. This work also aims to contribute to an understanding of the influence of isoelectronic doping on etch pit density (EPD) reduction. With a 4.5×1019 at.cm-3 optimum doping and a 8 µm optimum thickness, a 50-fold EPD reduction has been obtained. Buffer layers assure considerable EPD reductions to In concentration values of 4.5×1020 at.cm-3.
High Purity In0.5Ga0.5P Grown on GaAs by Liquid Phase Epitaxy
Authors: Wu M. C. , Su Y. K. , Cheng K. Y. , Chang C. Y.
Published: November 2005

High purity In0.5Ga0.5P epitaxial layers lattice-matched to GaAs substrates were grown by liquid phase epitaxy using a supercooling technique. The lowest carrier concentration of 3×1015 cm-3 has been achieved in the layer grown with a high temperature baked In solution and a supersaturation temperature of 6°C. A deep electron trap located at E
c-0.39 eV was detected by deep level transient spectroscopy, and its concentration is below 22×1014 cm-3.
Fabrication of F-Doped Silica Glasses by the Sol-Get Method
Authors: Shibata Shuichi , Kitagawa Takeshi , Hanawa Fumiaki , Horiguchi Masaharu
Published: November 2005

Fluorine-doped silica glasses have been successfully fabricated by the sol-get method. Fluorine was incorporated into dry gels during the sintering process under an inert gas flow containing SF6. The F-content in the silica glasses strongly depends on the get property, especially on the specific surface area. The maximum minus relative index difference of the F-doped silica glass made from the dry gets is 1.5 times greater than that made from the VAD soot.
Low Frequency Vibrational Modes in Sintered Small Metal Particles Studied by Missbauer Spectroscopy
Authors: Hayashi Mitsuhiko , Tamura Ichiro , Sakai Hiroshi
Published: November 2005

Sintered small particles of metals (pure Au and Cu–Au and Ag–Au alloys) were studied by Mössbauer spectroscopy. Systematic increase in line width with decreasing average density of the sinter was observed for the sinters of particles about 50 nm in diameter (Au and Cu–Au); this was attributed to the low frequency vibrational modes in the sinters by a model based on a classical theory of Mössbauer effect.
X-Ray Imaging Sensor Using a Polycrystalline Cadmium Telluride-Hydrogenated Amorphous Silicon Heterojunction
Authors: Hatanaka Yoshinori , Tomita Yasuhiro , Mimura Hidenori , Nogami Minoru
Published: November 2005

Polycrystalline cadmium telluride (pc-CdTe) was prepared by sputtering deposition and was of the zincblende type with a preferential orientation of the (111) planes parallel to the substrate. Its electrical resistivity was 1010 ohm cm and X-ray absorption coefficient was 3×103 cm-1. pc-CdTe formed a good heterojunctin against the hydrogenated amorphous silicon (a-Si:H) prepared by GD-CVD. An X-ray image sensor constructed of the heterojunction showed high sensitivity and high resolution.
Defects in Ga+ Jon Implanted GaAs–AlAs MQW Structures
Authors: Suzuki Yoshifumi , Hirayama Yoshiro , Okamoto Hiroshi
Published: November 2005

Cross-sectional transmission electron microscope observation was performed on GaAs–AlAs multi-quantum-well(MQW) structures which were compositionally disordered by ion implantation of the constituent element Ga+ and subsequent heat-treatment, and compared with MQW structures implanted by other species of ions As+, Si+ and Ar+. It was found that most of the defects introduced by ion implantation of Ga+ are annealed out by heat treatment at 750°C for 60 minutes, and that this is also the case for defects introduced by ion implantation by another constituent element As+, while many of the defects introduced by Si+ and Ar+ ion implantation remain without being annealed out.
A Comment on Defects in GaAs Crystals Observed by Infrared Light Scattering Tomography and IR Absorption Microscopy
Authors: Ogawa Tomoya
Published: November 2005

Infrared light scattering and absorption due to electrons trapped by centers with a hydrogen-like structure are discussed and the following reported evidences are explained: (a) enhancement of IR scattering without clear change of IR absorption due to ingot annealing of GaAs crystals and (2) light scattering after bleaching of IR absorption in GaAs atlow temperature.
New Method of Determining Spectral Line Profile Using the Fabry-Perot Interferometer
Authors: Okada Katsuhiko , Yoshihara Kunio , Kitade Atsuo
Published: November 2005

By solving an integral equation associated with the interferogram of the Fabry-Perot interferometer numerically, it is possible to reconstruct spectral lines of various profiles. The theory of Hilbert and Schmidt is applied, in which a pair of integral equations arc solved and the spectral line profile is reconstructed using their eigenfunctions and eigen values. The resolution is 0.004 cm-1 at about 20000 cm-1 when the optical path difference varies from 5×103 µm to 5×103+0.4 µm, for instance, by pressure-scanning. The range of wave number is 0.4 cm-1 and the reflectivity is 0.95. It is confirmed that this method gives satisfactory results in the presence of noise of Gaussian distribution of which standard deviation is 2.5×10-4.
Hot Electron Conduction in a-Si:H/a-Si0.2C0.8:H Super Structure
Authors: Yoshimoto Masahiro , Fuyuki Takashi , Matsunami Hiroyuki
Published: November 2005

A-Si:H/a-Si0.2C0.8:H super structures were fabricated by glow discharge method. The barrier layer using a-Si0.2C0.8:H was typically 40 Å thick. The thickness of the well layer consisting of doped n-type a-Si:H was changed from 17 Å to 100 Å. The construction of super structures was confirmed by X-ray diffraction. Generation of hot electrons using a newly devised super structure was verified experimentally for the first time.
Formation of Sendust Films by DC Opposite Sputtering Method
Authors: Miura Michiyori , Tanaka Katsuyuki , Noro Yoshihiko
Published: November 2005

Sendust films were prepared using DC opposite sputtering equipment. Films with a low coercive force of 0.5 Oe and an initial permeability of 1300 at 6 MHz can be prepared at a deposition rate of 5.5 µm/h without annealing of the films after the deposition. The way in which sputtering conditions influence the coercive force of the films was also investigated.
Dynamic Reflection High-Energy Electron Diffraction Observations of the Atomic Layer Epitaxy Growth of Zn Chaleogenides
Authors: Yao Takafumi
Published: November 2005

Intensity variations of reflection high-energy electron diffraction (RHEED) during atomic layer epitaxy (ALE) growth of Zn chalcogenides are investigated. The specular beam intensity varies exponentially with time when the surface changes between Zn-covered surface and Se-covered one. Simultaneously, the surface reconstruction changes corresponding to the change of the outermost surface layer. The time constant shows the adsorption time of an impinging molecular beam. The adsorption time constants are investigated as a function of K-cell temperatures and the substrate temperature. The growth dynamics of ALE of Zn chalcogenides thus can be investigated from variations in the RHEED intensity.
Catalytic Chemical Vapor Deposition (CTC–CVD) Method Producing High Quality Hydrogenated Amorphous Silicon
Authors: Matsumura Hideki
Published: November 2005

A new method of producing high quality hydrogenated amorphous silicon (a-Si:H) films is presented. An SiH4. and H2 gas mixture is decomposed without using any plasmas or photochemical excitation, but using only thermal and catalytic reactions between deposition-gas and a heated tungsten catalyzer. Photoconductivity of films produced by this methodreaches 10-3 (Ωcm)-1 and photosensitivity exceeds 105 for illumination of AM-1 light of 100 mW/cm2.
Development of High Efficiency Polycrystalline Silicon Solar Cells Using Solar Grade Cast Wafers
Authors: Takamori Nobuyuki , Asai Masahito , Shibata Akira , Nishida Keiichi , Suzuki Akio , Kaneko Kyojiro , Misawa Teruoki , Shimokawa Ryuichi , Hayashi Yutaka , Shigeta Jun , Ikeda Shigeru
Published: November 2005

This report describes the efficiency improvement study of polycrystalline silicon solar cells utilizing bulk type polycrystalline silicon wafers made by casting method. Utilizing the newly developed cell fabrication and solar grade cast wafer technologies, we obtained encapsulated cell efficiencies up to 14.6% (100 mW/ cm2, 28°C).
These efforts are expected to contribute to the reduction of the cell cost per peak watt.
Molecular Beam Epitaxial Growth of GaAs Using Triethylgallium and Arsine
Authors: Horiguchi Seishi , Kimura Kōzō , Kamon Koichi , Mashita Masao , Shimazu Mitsuru , Mihara Minoru , Ishii Makoto
Published: November 2005

Undoped GaAs layers were grown by molecular beam epitaxy (MBE) using triethylgallium (TEG) and arsine (AsH3). The electrical properties of grown layers depended on the cracking temperature T
c of AsH3 as well as the AsH3/ TEG ratio. At T
c=750°C, all layers were p-type; the lowest hole concentration was 1.2×1015 cm-3, with a room-temperature mobility of 400 cm2/V·s. At T
c=850°C, p-n conversion occurred as the AsH3/TEG ratio was increased, probably due to compensation between carbon and silicon atoms incorporated.
The Characterization of the Variability of Silicon Wafers by Leakage Current Measurements
Authors: Murray Eileen M. , Sugano Takuo , Asada Kunihiro
Published: November 2005

The variations in silicon wafers including standard Czochralski material, intrinsic gettered wafers, epitaxial wafers, wafers with and without backside damage, high oxygen wafers and nitrogen-doped Float Zone wafers were investigated by measuring the leakage currents of junction diodes fabricated by a modified CMOS dynamic RAM process.
Switching Process in Ferroelectric Liquid Crystals; Disclination Dynamics of the Surface Stabilized States
Authors: Ouchi Yukio , Takezoe Hideo , Fukuda Atsuo
Published: November 2005

The switching process of a surface stabilized ferroelectric liquid crystal cell is considered on the basis of disclination dynamics for various cell thicknesses. In this report we first summarize the surface stabilized ferroelectric liquid crystal states and their boundaries, and then examine the switching characteristics using stroboscopic micrographs. New experimental findings are (1) the boundary between two uniform states consists of two surface disclinations and one internal disclination, and (2) the domain nucleation, including the internal disclination loop, is responsible for the slow optical response. Finally, we point out several inconsistencies with our simple model regarding molecular orientations and suggest the existence of a selective pre-tilt at both surfaces, which should be controlled from an application point of view.
Small-Angle Neutron Scattering from Oxygen Precipitates in Czochralski-Grown Silicon Crystals
Authors: Takeda Takayoshi , Komura Shigehiro , Ohsawa Akira , Honda Koichiro
Published: November 2005

Small-angle neutron scattering (SANS) from oxygen precipitates in Czochralski-grown silicon crystals, annealed at several tempertures (600, 700, 750 and 800°C) for various periods, has been measured in order to investigate the growth mechanism of oxygen precipitation. It was confirmed that the precipitate grows two-dimensionally in a form of platelet with a thickness of about 40 Å, the plate surface being parallel to the {100} silicon lattice planes. It is considered from an analysis of the absolute values of the cross sections that the oxygen precipitates consist of oxygen-deficient oxides (SiO2-x
), or that the nucleation rate of the oxygen precipitate is less than the reported value. The mean size of oxygen precipitates grows according to less than the 3/4-th power of annealing time t at 750°C and to about the 3/4-th power of t at 800°C.
GaAlAs/GaAs MOCVD Growth for Surface Emitting Laser
Authors: Koyama Fumio , Uenohara Hiroyuki , Sakaguchi Takahiro , Iga Kenichi
Published: November 2005

A GaAlAs/GaAs Metalorganic chemical vapor deposition (MOCVD) has been introduced for growing GaAlAs/GaAs wafers with a thick active layer (d\cong3 µm) and multilayer Bragg reflectors for surface emitting lasers. A nominal threshold current density as low as 3.6 kA/cm2 µm was obtained in stripe cleaved lasers with a cavity length of 400 µm. GaAlAs/GaAs surface emitting lasers were fabricated by using these MOCVD grown wafers. The room-temperature pulsed operation of an MOCVD grown laser was obtained with a threshold current of 300 mA as a primary demonstration. In addition, a reflectivity of 97% was achieved by a Zn-doped 30 layer Ga0.9Al0.1As/AlAs Bragg reflector. These experimental results suggest the possibilities of a low-threshold surface emitting laser grown by MOCVD and potential applications toward integrated optics based on surface emitting lasers.
Growth Temperature Dependence of Disorderings in a Be-Doped GaAs/AlAs Multilayered Structure
Authors: Kamata Norihiko , Kobayashi Kikuo , Endo Koichi , Suzuki Takeo , Misu Akira
Published: November 2005

The compositional disorderings of a GaAs/AlAs multilayered structure grown with molecular-beam epitaxy, selectively doped with Be in barrier layers, were studied. Using the depth profiles measured by means of secondary ion mass spectroscopy (SIMS), we investigated the mixing of Al and Ga during growth, the interdiffusion of these atoms during post growth annealing at 750°C, and the Be doping concentration dependence of those disorderings. The mixing during the growth was found to be strongly dependent on both the Be concentration and the substrate temperature. The multilayer which preserved the prescribed structure during growth were found to be stable through annealing; however, those slightly mixed during growth were found to be further disordered mainly in the first short annealing and a little thereafter.
Crosshatch Pattern on InGaAsP Layers Grown on GaAs0.7P0.3 Substrate by LPE
Authors: Fujii Sadao , Susawa Hiromoto , Sakai Shiro , Umeno Masayoshi
Published: November 2005

The crosshatch pattern on an InGaAsP layer grown on a (001) 2° off GaAs0.7P0.3 substrate by LPE was investigated in detail. The crosshatch pattern was analyzed by a fast Fourier transformation of surface height profiles and the effects of growth conditions as well as the substrate pretreatment could be clarified. The surface roughness was reduced by substrate polishing. The formation mechanism of a crosshatch pattern is discussed and it is shown that the crosshatch pattern becomes initiated at the aligned dislocation existing on the substrate and is enhanced by a crystal orientation dependence of the growth rate. About an 80-µm wide (001) facet going along the <110> direction appears on a grown surface. This (001) facet is very smooth and may be suitable for visible lasers having a stripe in the <110> direction.
Lateral Seeding of Silicon-On-Insulator by Using an Elliptically-Shaped Laser Beam
Authors: Fujii Eiji , Senda Kohji , Hiroshima Yoshimitsu , Takamura Tohru
Published: November 2005

It has been demonstrated that an elliptically-shaped laser beam with an elliptical ratio of 20 can be successfully used to obtain a melt width as large as 160 µm. We also discuss an interesting experimental result in which the growth length of a single crystal from the seeding region on (100) Si substrates is larger in the scanning direction along <110> than along <100> in a lateral seeding process.
Calculations of Molecular Beam Flux from Liquid Source
Authors: Yamashita Tatuya , Tomita Takashi , Sakurai Takeshi
Published: November 2005

A calculation of the MBE flux from slantingly arranged crucibles containing liquid sources such as Ga and Al has been performed. The calculated and experimental results are in good agreement. The results also indicate that cylindrical crucibles are more effective in improving the uniformity of the epitaxial thickness than conical crucibles.
Characterization of WNx/GaAs Schottky Contacts Formed by Reactive RF Sputtering
Authors: Yamagishi Haruo , Yamamoto Yasuhiro
Published: November 2005

The structural and electrical characterization of WN
x
/GaAs Schottky contacts formed by a reactive rf sputtering in a mixed nitrogen-argon gas atmosphere was performed under various fabricating conditions to establish a Schottky gate for a self-aligned GaAs MESFET. The characteristics of a WN
x
film and a WN
x
/GaAs contact greatly depend on the relative nitrogen gas partial pressure γ, rf sputtering power P
0, and annealing temperature T
A. We determined the optimum values of γ, P
0, and T
A in order to obtain an excellent thermally stable WN
x
/GaAs Schottky contact for a self-aligned gate, with a typical barrier height φBO
I of about 0.94 eV and an ideality factor n of ∼1.1.
Restitution Coefficient in a Collision between Two Spheres
Authors: Kuwabara Goro , Kono Kimitoshi
Published: November 2005

On the basis of elastic theory the restitution coefficientewas derived as a function of the elastic constants, radii, masses and colliding velocities of two spheres by taking the visco-elastic property into consideration. For a coefficient close to one, the value of (1-e) was found to be proportional to (velocity)1/5. This result was compared with a treatment based on the plastic property of solids.
X-Ray Lithography Using Chlorinated Polymethylstyrene (CPMS) as a Negative X-Ray Resist
Authors: Suzuki Yoshiki , Ishio Noriaki , Eimori Takahisa , Yoshioka Nobuyuki , Watakabe Yaichiro , Yamazaki Teruhiko
Published: November 2005

The development characteristics of chlorinated polymethylstyrene (CPMS) have been studied in order to form half micron patterns with X-ray lithography. The solubility and the swelling of CPMS are very sensitive to the chlorine content, especially in ethylcellosolve (EC); swelling has been reduced while maintaining a reasonable solubility in the development process of a CPMS (\overlineM
w=52×104, C
l%=21.8 wt%) using an EC as a developer. This CPMS has been called CPMS-HR. The resolution of CPMS-HR has been influenced by a resist shrinking procedure which is determined by the rinse sequence. EC development followed by the optimum rinse sequence has formed 0.4-µm wiring patterns of CPMS-HR with a thickness of 1.2 µm. The advantages of the X-ray lithography using a single CPMS-HR layer have been demonstrated through the application of the X-ray lithography to a VLSI fabrication process.
Thermal Diffusion of Buried Beryllium and Silicon Layer in GaAs Doped by Focused Ion Beam Implantation
Authors: Morita Tetsuo , Kobayashi Junji , Takamori Takeshi , Takamori Akira , Miyauchi Eizo , Hashimoto Hisao
Published: November 2005

The diffusion profiles of buried Be and Si doped by focused ion beam (FIB) implantation in GaAs after annealing were investigated. The diffusion coefficients of Be and Si were determined by fitting from the results of computer calculations. The diffusion coefficient of FIB-doped Be was enhanced by excess interstitial Be. Beryllium diffusion profiles expand by annealing with a high dose at 850°C. The concentration-dependent diffusion of Si in GaAs doped using a molecular beam was observed. The diffusion coefficient of Si heavily doped by FIB, however, was undetectably small in contrast with that of Be at 850°C.
In Situ Electrical and Optical Measurements on GaAs Epitaxial Layers during Chemical Etching
Authors: Yamashita Akiyasu
Published: November 2005

For the detailed characterization of epitaxial GaAs a chemical method has been devised. This method combines carrier concentration vs depth profile measurements with in-depth photocapacitance spectroscopy regarding the deep levels involved in a sample. This method was constructed on the following base: (1) Uniform chemical-etching by suitable etchants selected in the H2SO4–H2O2–H2O system and (2) In situ capacitance and photocapacitance measurements on the etchant as well as the other electrolyte Schottky contact. In applying the method there is almost no restriction on the magnitude of both the carrier concentration and the sample-thickness. It can, therefore, be applied to various samples, including their interface regions. Here, details of the method and typical results are presented.
A Study on Boundary Layer Arc in an MHD Generator Channel
Authors: Seidou Tadashi , Ohtomo Norio , Aoki Yoshiaki , Kayukawa Naoyuki
Published: November 2005

In a propane-oxygen combustion MHD generator channel, experimental measurements were made of the V–I characteristics accompanying the arc current with an without and externally-applied magnetic field. The data for V–I characteristics were analyzed by a theoretical approach using Rosa's arc model. Good agreement between the theoretical results and the experimental data was observed. Moreover, the critical current densities were obtained from the V–I characteristics data and could be compared with a curve calculated by using Petty's model. It has been confirmed that a strong magnetic field affects the behavior of the electrode boundary-layer arc.
Green Electrochromism in the System of p-Cyanophenylviologen and Potassium Ferrocyanide
Authors: Mori Hiroshi , Mizuguchi Jin
Published: November 2005

A high-performance green-electrochromic display has been developed in a system of p-cyanophenylviologen (p-CV) and potassium ferrocyanide in the presence of sodium hypophosphite and potassium chloride. The main difficulty was in the fact that p-CV reacts with potassium ferrocyanide to form a scale-like green precipitate even in the absence of any applied voltage when the concentration of p-CV exeeds only 0.001 M. At this concentration, only a poor write-erase contrast ratio can be obtained. The addition of an excess of potassium chloride, however, dissolves the precipitate, which enabled a concentration as high as 0.035 M to be attained and hence a high contrast ratio. Sodium hypophosphite facilitates the erasing of the reduced p-CV (“green”) and thus contributes to a long working lifetime. The electrochromic characteristics obtained are as follows: driving voltage of 0.4–0.9 V, contrast ratio of 50:1 and write-erase cycle of about 3 × 107.
High Pressure Gas Apparatus for Measuring Ultrasound Velocity in Matters up to 4 GPa
Authors: Kimura Masaki , Hanayama Yoichi , Nishitake Teruo
Published: November 2005

A piston-cylinder apparatus using gases, which could produce hydrostatic pressures of up to 4 GPa and temperatures of up to 800°C is described. A high-pressure tapered cylinder made of 350 maraging steel was 262 mm long and had a 19 mm inside diameter and a working space of 100 mm in length at 4 GPa. The support ring was made of 300 maraging steel and was approximately 180 mm thick and 420 mm in outside diameter. For measurements of both the pressures and temperatures, a manganin gauge and a thermocouple were placed inside the tapered cylinder. No difficulty was encountered with any of these components at pressures of up to 3.5 GPa. This apparatus could be used almost indefinitely, since neither a considerable change of the bore nor surface cracks in the tapered cylinder had been found thus far.
Drift Mobilities of Photocarriers in Amorphous Hydrogenated GaP Made by Reactive Evaporation
Authors: Onuki Masami , Kubota Hiroshi
Published: November 2005

The drift mobilities of photoelectrons and photoholes in a film of a-GaP:H at 300 K were estimated to be 2.3×10-3 cm2/Vs and 1.3×10-3 cm2/Vs, respectively, from a time-of-flight measurement in which the mole ratio of Ga to P, r, in the film was nearly equal to unity. Spectra of the ac photoconductivity for different hydrogenated films with different values of r were measured at 90 K and the results at low photon energies suggest an excitation of electrons and holes at the gap states to the mobility edges of the conduction and valence bands, respectively, owing to the transport of mobile holes as well as mobile electrons deduced from time-of-flight measurements.
The Luminescence and ESR of a Synthetic Emerald and the Natural Ones Mined from Santa Terezinha in Brazil
Authors: Ohkura Hiroshi , Hashimoto Hisashi , Mori Yuzo , Chiba Yoshinori , Isotani Sadao
Published: November 2005

Both the luminescence and ESR of a synthetic (KC-) emerald and a natural (ST-) type, mined from Santa Terezinha in Brazil, have been studied. The luminescence spectra of the impurity Cr3+ ions in both emeralds consist of two zerophonon lines followed by satellite bands. The satellite band of the ST-emerald shows huge intensity and broad width compared with that of the KC-emerald. The ESR of the Cr3+ ions in the ST-emerald is specific in the anisotropy of the g-factor and has a wider peak-to-peak value than the KC-emerald. We propose that these differences are caused by an interaction induced by the presence of a large number of impurity Fe3+ ions contained in the ST-emerald. The existence of Fe3+ and their concentrations were estimated by ESR.
Effects of an Electric Field on the Decay Time of Luminescence from a GaAs/Ga0.6Al0.4As Multi-Quantum-Well Structure
Authors: Miyoshi Tadaki , Aoyagi Yoshinobu , Segawa Yusaburo , Namba Susumu , Sano Naokatsu
Published: November 2005

The decay time of luminescence from a multi-quantum well has been measured at 20 K by using a cw mode-locked Kr laser and a synchroscan-streak camera. The decay time was found to increase with applied electric field. The increase is considered to be attributable to a field-induced carrier separation. The decay time depends on the observed wavelength of luminescence. This dependence changes with the electric field, suggesting that the energy-decreasing rate of excitons becomes slower in the presence of an electric field.
Study on Work Function of the {0001} Faces of CdS Crystal. III. Effect of the Irradiation with Red Light
Authors: Sasaki Kazuo
Published: November 2005

By means of a highly sensitive thermistor (sensitivity: 10-3°C) as well as a Kelvin electrode of NESA glass with a detection sensitivity of several mV, the contact potential difference and the temperature of a crystal were measured with respect to CdS polar surfaces. It was confirmed that when a photoconducting crystal is irradiated at room temperature by weak light with bulk excitation for a certain time and then interrupted, the temperature drop and rapid decrease in the electric conductivity of the crystal suggests a pyroelectric charge on the polar surface.
Effect of Cladding Material on 2-eV Optical Absorption in Pure-Silica Core Fibers and Method to Suppress the Absorption
Authors: Nagasawa Kaya , Tohmon Ryoichi , Ohki Yoshimichi
Published: November 2005

The growth of 2-eV optical absorption induced by γ-ray irradiation is larger in pure-silica core fibers with a dopedglass cladding than in the fibers with a silicone cladding, regardless of the manufacturing process. Precursors of nonbridging oxygen hole centers which abundantly exist at the core/cladding interface of the glass-cladding fibers are responsible for the difference in the absorption. A combined-treatment of hydrogen and γ-ray irradiation can remove these precursors and suppress the absorption.
Resistivity Correction Factor for Four-Probe Method on Circular Semiconductors I
Authors: Yamashita Masato
Published: November 2005

A resistivity correction factor is described for a system consisting of a thick, circular semiconductor and a four-probe array. The electric potentials in the interior of the sample were obtained by solving Poisson's equation analytically. Expressions for the resistivity correction factor are presented for three cases of the probe position. The resistivity correction factors of a circular sheet, calculated by the present method, coincides with that obtained from the conformal transformation method. Numerical evaluations were carried out as a function of the thickness and radius of the sample and the spacing and position of the probe array.
SiOx/TaOx Gate Insulator a-Si TFT for Liquid Crystal Displays
Authors: Ikeda Mitsushi , Dohjo Masayuki , Aoki Toshio
Published: November 2005

A double layer of anodized TaO
x
and plasma CVD SiO
x
was applied to the gate insulator for an a-Si TFT active matrix LCD. This double layer was effective in eliminating interlayer short circuits between address bus lines and data bus lines in an LCD. No deterioration was observed in the TFT characteristics or the reliability upon adding a TaO
x
layer to a SiO
x
gate insulator. An LCD with no interlayer short circuits has been fabricated with this double layer.