bluuebunny/crossref_metadata_2025 huggingface dataset:
Adsorption and Desorption of AlCl3 on Si(111)7×7 Observed by Scanning Tunneling Microscopy and Atomic Force Microscopy
Authors: Uesugi Katsuhiro , Takiguchi Takaharu , Izawa Michiyoshi , Masamichi Yoshimura Masamichi Yoshimura , Takafumi Yao Takafumi Yao
Published: February 2005

The initial stage of the reaction of aluminum chloride (AlCl3) with the Si(111)-(7×7) surface is investigated using a scanning tunneling microscope (STM) and an atomic force microscope (AFM). Reacted and unreacted sites are manifested in the contrast of adatom sites on the AlCl3-exposed surface. AlCl3 molecules dissociatively adsorb onto the Si(111)-(7×7) surface at room temperature. The preferential adsorption site is found to be the center-adatom site. Thermal annealing at 1200°C results not only in anisotropic etching of the Si surface but also in the deposition of Al.
Effects of Electron Irradiation on Two-Dimensional Electron Gas in AlGaAs/GaAs Heterostructure
Authors: Wada Toshimi , Kanayama Toshihiko , Ichimura Shingo , Sugiyama Yoshinobu , Shunji Misawa Shunji Misawa , Masanori Komuro Masanori Komuro
Published: February 2005

This paper describes how the two-dimensional electron gases in AlGaAs/GaAs heterostructures are degraded by low-energy electron irradiation. Both the electron mobility and the two-dimensional carriers are shown to decrease considerably by a 1×1017/cm2 irradiation with the incident electron energy of 8 keV. Comparing the experimental results both with the Monte Carlo simulation and with the theoretical mobility calculation, we speculated that the mobility degradation and the 2D carrier compensation are partly caused by the formation of complex defects in the GaAs buffer layer which are due to the excitations of core electrons of As and that the mobility is further degraded by the formation of short-range scatterers in the AlGaAs/GaAs heterointerface.
Barrier Height of InP Schottky Diodes Prepared by Means of UV Oxidation
Authors: Nakamura Junichi , Hirohiko Niu Hirohiko Niu , Seigô Kishino Seigô Kishino
Published: February 2005

Schottky diodes of Au/oxide/InP are fabricated by means of UV oxidation and evaluated by means of current-voltage (I-V) and capacitance-voltage (C-V) measurements. Their barrier heights are estimated from the I-V curve at room temperature, the 1/C
2-V plot and the Richardson plot. Remarkable apparent improvement of the I-V characteristics is achieved with the use of UV oxidation. However, there is a discrepancy among the barrier heights calculated from the three characteristics. It is revealed that these results are caused by the reduction in the saturation current due to electron tunneling through the UV oxide layer. On the basis of a tunneling model, the relationship between the tunneling probability and the thickness of the oxide is discussed.
A Simulation of Transient Negative Photoconductivity in Silicon Doped with Gold
Authors: Kimura Hideki , Kurosu Tateki , Yukio Akiba Yukio Akiba , Masamori Iida Masamori Iida
Published: February 2005

A transient negative photoconductivity phenomenon observed in silicon doped with gold atoms has been investigated. Rate equations for photoexcited carriers in silicon containing gold levels have been derived, taking two charge situations of gold atoms acting as the deep impurity into account. Computer simulation has also been carried out in order to obtain information about transient behavior of the photoexcited carriers. The simulated results show transient negative photoconductivity characteristics, which are in agreement with those observed in the experiment.
Estimation of Frequency Conversion Efficiency of Lasers with Intracavity Optical Mixing
Authors: Souma Hirotoshi , Toshiteru Maeda Toshiteru Maeda , Chuji Horie Chuji Horie
Published: February 2005

For lasers with intracavity frequency conversion, we present general expressions of the power output efficiencies as a function of the relative length of nonlinear optical crystals for different values of parameters related to fundamental lasers, the nonlinear crystal and optical geometries. The maximum available efficiencies due to the nonlinear interaction are calculated for cases where the optimum coupling conditions are either satisfied or not satisfied. It is explained that the forbidden ranges of nonlinear coupling coefficients are the result of several factors. These results provide useful suggestions for practical construction.
Anomalous Exciton Absorption in PbI2 Films Produced via Amorphous-To-Crystalline Transformation
Authors: Kondo Shin-ichi , Mikiya Shiraki Mikiya Shiraki , Tadaaki Saito Tadaaki Saito
Published: February 2005

An anomaly was found in the film annealed at 410 K for 1 h after the crystallization at 198 K. Unlike the case of the ordinary film, the 1st exciton band showed a doublet structure at 77 K. Upon heating, its lower-energy component grew and sharpened, showing the smallest full width at half maximum, 7 meV, at 150 K. The anomaly was correlated with a random crystallographic orientation of individual crystallltes in the film.
Molecular Orientation and Anisotropic Photoconduction of Evaporated Oligo-p-Phenylene Sulfide Films
Authors: Takimoto Akio , Wakemoto Hirofumi , Hisahito Ogawa Hisahito Ogawa
Published: February 2005

Thin films of highly oriented oligo-p-phenylene sulfide (OPS) molecules have been prepared by vapor deposition. This proves that the chain axis of OPS molecules has a directional arrangement perpendicular to the substrate with a decrease in deposition rate. Parallel OPS molecules, which are uniaxially oriented along the rubbing direction of a substrate covered with a rubbed polymer thin film, can be obtained by evaporation with a higher deposition rate. Photocurrent measurements of uniaxially oriented films along the rubbing direction have indicated that OPS molecules are anisotropic in photoconduction, that is, carriers are more easily transported perpendicular to the molecular chain axis than along that axis.
Electron Transport in Hole-Transport-Type Photoconductive Film
Authors: Nakazawa Toru , Kawahara Akihiko , Mizuta Yasufumi , Eiichi Miyamoto Eiichi Miyamoto , Nariaki Mutoh Nariaki Mutoh
Published: February 2005

Photosensitivity of a film with dispersed pigment as carrier generation material in a hole-transport matrix was found to have a close connection with the electron-transport property of the film. Effects of the component materials on electron transport in the film were studied by means of photoinduced discharge of the surface potential applied to the film. Presence of pigment was found to be necessary for the electron transport to occur. We also found that the presence of hole-transport material in the matrix improved the electron transport between pigment particles.
High-Field Pulsed Magnet Wound of Cu-Ag Alloy Wire
Authors: Asano Toshihisa , Sakai Yoshikazu , Inoue Kiyoshi , Mitsutake Oshikiri Mitsutake Oshikiri , Hiroshi Maeda Hiroshi Maeda
Published: February 2005

Pulsed magnets wound of a newly developed Cu-Ag conductor were tested. A magnetic field of 62.7 T with 2.56 ms rise time was generated in a pulsed magnet of 15 mm inner winding diameter made of 2 mm×3 mm rectangular-cross-sectional Cu-Ag alloy wire after the magnet was cooled down to 77 K. The current for this shot was supplied by a capacitor bank of 10 mF charged to 5 kV. The Cu-Ag alloy wire proved to be promising for use in multilayered pulsed magnets due to its combination of high conductivity, high strength and ease of handling.
Formation Energy of Antisite Boron in GaAs
Authors: Masashi Suezawa Masashi Suezawa , Koji Sumino Koji Sumino
Published: February 2005

The concentration of antisite B and regular B atoms on Ga sites were measured by means of optical absorption in B-doped GaAs crystals quenched from various temperatures. The formation energy of an antisite B in GaAs was determined to be 1.7 eV.
Fast and Slow Processes in Light-Induced Electron Spin Resonance in Hydrogenated Amorphous Si-N Films
Authors: Kumeda Minoru , Sugimoto Ayumi , Zhang Jin-Yan , Ozawa Yoshiaki , Shimizu Tatsuo
Published: February 2005

Detailed light-induced Electron Spin Resonance (ESR) measurements are performed at room temperature and liquid nitrogen temperature for hydrogenated amorphous silicon alloyed with various amounts of nitrogen. The increase in the ESR signal intensity with increasing illumination time can be described in terms of a fast increase and a slow increase. The fast-increase component decays faster after ceasing illumination than the slow-increase component. The origins of the two components are discussed.
Semiconductor-Like Carrier Conduction and Its Field-Effect Mobility in Metal-Doped C60 Thin Films
Authors: Hoshimono Katsunori , Fujimori Shigeo , Shizuo Fujita Shizuo Fujita , Shigeo Fujita Shigeo Fujita
Published: February 2005

Conductivity and its temperature dependence, conduction type, and field-effect mobility in metal (In or Sb)-doped C60 thin films are investigated together with those of undoped films. All electrical measurements have been conducted without exposure to air after deposition, in order to minimize the degradation of films due to incorporation of oxygen. For films with both dopants, (1) the conductivity is several orders of magnitude higher than that of undoped films, (2) the conductivity follows a semiconductor-like temperature dependence with the activation energy of 0.10-0.17 eV, which is much lower than that of the undoped films, 0.51 eV, (3) the conduction is n-type, and (4) the field-effect mobility is 0.03-0.04cm2/V·s. Enhancement of conductivity in metal-doped C60 films is attributed to the increase of both carrier concentration and mobility.
Pulsed Laser Deposition of C60 Thin Films with Atomically Smooth Surface
Authors: Yoshimoto Mamoru , Arakane Takashi , Asakawa Toshiaki , Horiguchi Kenichi , Hirai Kiyoto , Hideomi Koinuma Hideomi Koinuma
Published: February 2005

Pulsed laser deposition was found to be a novel method for the fabrication of high-quality C60 thin films with extremely smooth surfaces. The irradiation of a pulsed KrF excimer laser beam onto a C60 powder target induced the formation of a plasma plume when the laser energy fluence was 40 mJ/cm2 and higher. The ablated species were condensed onto a substrate in the form of thin film. Thin films deposited at laser energy fluences in the narrow range between 40 mJ/cm2 and 50 mJ/cm2 were confirmed to have a single phase of C60 solid from the Raman scattering and optical absorption spectra as well as from the chromatography of benzene extract of the films. With increase of the laser energy fluence over 50 mJ/cm2, the deposited films included increasing amounts of photodecomposed components and, consequently, varying physical properties. Atomic force microscopy revealed atomically smooth surfaces of C60 thin films laser-deposited at laser energy fluences between 40 mJ/cm2 and 50 mJ/cm2.
Enhanced Two-Dimensional Growth of GaAs on InP by Molecular Beam Epitaxy with Atomic Hydrogen Irradiation
Authors: Chun Yong Jin , Yoshitaka Okada Yoshitaka Okada , Mitsuo Kawabe Mitsuo Kawabe
Published: February 2005

Growth modes and lattice relaxation processes in the heteroepitaxial growth of GaAs films on InP substrates by molecular beam epitaxy (MBE) with atomic hydrogen irradiation have been investigated for different growth temperatures. We have found that atomic hydrogen delays the onset of island growth and lattice relaxation at a substrate temperature of 350°C because of the presence and interaction of hydrogen atoms with incoming atoms on the surface at this temperature range. At 450°C, no significant differences in the lattice relaxation process between the MBE growth with and without the atomic hydrogen irradiation were observed. This change in the growth mode is believed to be an important factor which affects the mechanism of strain relaxation.
Control of Fluorocarbon Radicals by On-Off Modulated Electron Cyclotron Resonance Plasma
Authors: Takahashi Kunimasa , Masaru Hori Masaru Hori , Toshio Goto Toshio Goto
Published: February 2005

The CF, CF2 and CF3 radical densities were investigated using infrared diode laser absorption spectroscopy (IRLAS) in a CHF3 electron cyclotron resonance (ECR) plasma with varying on-off period of the microwave source, as well as continuous wave (CW). The ratio of CF and CF2 radical densities to CF3 radical density was successfully controlled through variation of the duty cycle in a constant pulse width, together with the deposition rate of fluorocarbon films. Furthermore, the radical densities were discussed in comparison with intensities of emission lines F*, Ar* and Hα.
Nonlinear Detection of Ultrasonic Vibrations in an Atomic Force Microscope
Authors: Oleg Kolosov Oleg Kolosov , Kazushi Yamanaka Kazushi Yamanaka
Published: February 2005

A new method is proposed to detect ultrasonic vibration of the samples in the Atomic Force Microscope (AFM) using nonlinearity in the tip-sample interaction force curve F(z). Small amplitude ultrasonic vibration less than 0.2 nm is detected as an average displacement of a cantilever. This Ultrasonic Force Mode (UFM) of operation is advantageous in detecting ultrasonic vibration with frequencies up to the GHz range, using an AFM cantilever with a resonant frequency below 100 kHz. It was found that a strong repulsive force is acting after an ultrasonic amplitude threshold of the is crossed, with the amplitude of this threshold depending upon the average force applied to the tip.
Measurement of Extreme-High-Vacuum Pressure by Laser Ionization
Authors: Kokubun Kiyohide , Ichimura Shingo , Shigeyuki Sekine Shigeyuki Sekine , Hazime Shimizu Hazime Shimizu
Published: February 2005

Measurement of gas pressure using nonresonant multiphoton ionization has been performed. As a result, extreme-high-vacuum (XHV) pressure to 7×10-10 Pa was successfully measured by this method. The experimental results are presented, and problems related to noise are discussed.
Substitutional Diffusion of Transition Metal Impurities in Silicon
Authors: L. Zhong L. Zhong , F. Shimura F. Shimura
Published: February 2005

Near-surface Cu and Ni rich layers are observed by secondary ion mass spectroscopy (SIMS) in intentionally contaminated silicon wafers after thermal oxidation at 950°C for 35 min. The diffusivities of Cu and Ni obtained from their respective SIMS profiles are almost 9 orders of magnitude smaller than documented which are widely believed of interstitials, but comparable to that of Group III and V atoms which are known as substitutional. According to the experimental results, a model is proposed for in-diffusion of transition metal atoms contaminated on the surface of a silicon wafer during thermal oxidation. In this model, the interstitial and substitutional atoms diffuse independently and the slow substitutional diffusion gives rise to a near-surface impurity-rich layer.
Structural and Magnetic Properties of (001) Fe Films
Authors: Fuke Hiromi , Atsuhito Sawabe Atsuhito Sawabe , Tetsuhiko Mizoguchi Tetsuhiko Mizoguchi
Published: February 2005

The relationship between structural and magnetic properties was examined for epitaxial Fe(001) films with 500 Å to 1 µm thickness on MgO(001) substrates prepared by the ion beam sputtering technique. Lattice spacing perpendicular to the (001) plane of as-deposited Fe films was found to be longer by 1.4 to 2% than the lattice parameter of bulk Fe. The shapes of M-H curves for those Fe films changed from square to step type with increasing film thickness. Stripe domain was observed for films with step-type hysteresis loops. The appearance of the stripe domain was clearly explained by the perpendicular magnetic anisotropy induced by the tension of the lattice.
Appearance of Quasi-Direct Optical Transition from Si Network in SiO2-Doped Si Films
Authors: Osaka Yukio , Toyomura Fumitaka , Kohno Hideyuki Katayama
Published: February 2005

We report the first observation of an efficient optical absorption in the optical energy region 1.0∼1.8 eV from the Si network in SiO2-doped Si films. The SiO2-doped Si films were formed using the rf magnetron sputtering technique. From electron paramagnetic resonance measurements, the dangling bond density of unannealed samples was estimated to be 3×1017 cm-3.
Low-Temperature Synthesis of C-Axis-Oriented Polycrystalline Aluminum Nitride Films by Electron Cyclotron Resonance Plasma Chemical Vapor Deposition Using AlBr3-N2-H2-Ar Gas System
Authors: Zhang Wei , Someno Yoshihiro , Makoto Sasaki Makoto Sasaki , Toshio Hirai Toshio Hirai
Published: February 2005

Aluminum nitride (AlN) thin films have been synthesized on silicon substrates via microwave-excited electron cyclotron resonance (ECR) assisted chemical vapor deposition (CVD) at substrate temperatures ranging from 300 to 400°C from the AlBr3-N2-H2-Ar gas system. The resultant films were characterized using X-ray diffraction, scanning and transmission electron spectroscopies, transmission electron diffraction, infrared transmission spectroscopy, and Auger electron spectroscopy. The study of these analyses shows that highly c-axis-oriented polycrystalline AlN films, free of bromine and hydrogen impurities, can be deposited by the ECR plasma CVD method.
Quantitative Detection of Oxygen Contamination Related Traps in Gallium Arsenide Epitaxial Layer Grown by Molecular Beam Epitaxy at Low Temperature
Authors: Lau Wai Shing , Goo Chuen Hang , Chu Tow Chong Chong
Published: February 2005

Using a new technique, zero quiescent bias voltage transient current spectroscopy (ZBTCS), a semi-insulating GaAs epitaxial layer grown by MBE at 230°C is found to have a continuum of states with some discrete traps. The dominant discrete electron trap has an activation energy of 0.55 eV and a concentration of the order of 1017cm-3. This trap is believed to be the EL3 electron trap related to oxygen contamination. Quantitative secondary ion mass spectroscopy (SIMS) measurements confirms that GaAs epitaxial layers tend to be contaminated by oxygen when the growth temperature is low. The role of an ammonium sulphide surface treatment on the measured trap concentration is also discussed.
Superior Corrosion Resistance of Ion Beam Deposited Iron Film
Authors: Kiyoshi Miyake Kiyoshi Miyake , Kenya Ohashi Kenya Ohashi
Published: February 2005

Superior corrosion resistance was obtained for 56Fe+-IBD (ion beam deposited) films on Si and Ge substrates. The iron films deposited at an ion energy of 50 eV showed the highest corrosion resistance in 0.001 M NaCl solution. The estimated current density at its corrosion potential was four orders of magnitude smaller, 10-6 A/m2, than that of 2N-purity iron bulk materials. Ion bombardment induced formation of finely-grained polycrystalline structure, and coupled with its purifying action, these were considered to account for the superior corrosion resistance.
Transport Properties of SrCuO2 Thin Films with Artificially Modulated Structures
Authors: Kawai Maki , Liu Ziyuan , Sekine Rika , Koinuma Hideomi
Published: February 2005

Transport properties of SrCuO2 thin films with and without the artificial modulated structures formed by periodical incorporation of extra Sr layers as (SrCuO2)10Sr by MBE are presented. The resistivity of the film is found to decrease by one order of magnitude when they are post-oxidized in situ. For the films with an extra Sr layer (double Sr-layer formation) for every ten units of SrCuO2 cells, an anomaly in resistivity is observed around 100 K which coincides with the reported T
c of the high-T
c superconductor of infinite layers.
Crystal Structure and Magnetoresistance of Fe10Ni90 Films Deposited by Sputter-Beam Method
Authors: Yokoyama Yukimasa , Okamoto Satoshi , Kitakami Osamu , Shimada Yutaka , Watanabe Fuminori , Kondo Shinji , Hayashi Atsushi , Fujita Hiroyuki
Published: February 2005

Films of Fe10Ni90 alloy were deposited by the sputter-beam method and their magnetic properties were compared with those of films deposited by a conventional RF sputtering method. High magnetoresistance was obtained for film thickness between 550∼2250 Å. Some of the films exhibit magnetoresistance equal to the bulk value. These properties are attributed to a more enhanced crystal growth than in the RF method.
Contact Charging of a-Se Electrophotographic Photoreceptor with Molten Gallium
Authors: Matsumoto Shoji , Du Boxue , Masui Masayoshi , Kuniomi Oguchi Kuniomi Oguchi , Manabu Takeuchi Manabu Takeuchi
Published: February 2005

Contact charging of an amorphous selenium (a-Se) electrophotographic photoreceptor was studied employing molten gallium as the contact medium. Bias voltage was applied between the photoreceptor and the molten gallium, and the surface potential of the photoreceptor was monitored with a surface potentialmeter. The photoreceptor was charged to close to 100% of the bias voltage for both the positive and negative biases. The charging mechanism of the a-Se photoreceptor with molten gallium was attributed to charge injection and trapping. Uniformity of the surface potential of the photoreceptor contact-charged with molten gallium was confirmed.
Optical Characterization of Ion-Implanted Glass Surface Layers with Surface Plasmon Resonance Method
Authors: Dai Yisheng , Okamoto Takayuki , Ichirou Yamaguchi Ichirou Yamaguchi , Masaya Iwaki Masaya Iwaki
Published: February 2005

The feasibility of a surface plasmon resonance method for optical characterization of ion-implanted glass surface layers is demonstrated. Resonance curves were measured for silica and fluoride glass implanted with various nonmetal and metal ions and compared with those of unimplanted samples. Regardless of their thinness and unclear depth profile of refractive index, the effect of ion implantation on the refractive index and absorption of the glass surface layers could be quantitatively evaluated by curve fitting method.
Optical Properties of GaAs(001) Surface during Desorption of As Atoms
Authors: Sakamoto Akira , Shigeyuki Otake Shigeyuki Otake , Izumi Iwasa Izumi Iwasa
Published: February 2005

The surface photoabsorption (SPA) signal from the GaAs (001) surface was measured at the angle of incidence between 69° and 83°. We found two processes of As desorption during H2 purge after AsH3 injection. The SPA signals for the two processes had different time constants and different angle dependence. The angle dependence indicated that the change of the SPA signal was due to both the optical absorption of the surface and the refractive index change of the surface layer.
Growth-Temperature Dependence of the Quality of Al2O3 Prepared by Sequential Surface Chemical Reaction of Trimethylaluminum and H2O2
Authors: Jia Fa Fan Jia Fa Fan , Koichi Toyoda Koichi Toyoda
Published: February 2005

Dependence of the quality of thin films of Al2O3 on the growth temperature was investigated in the surface reaction limited growth system. It has been found that the density, the chemical bonding strength, and the electrical properties improve significantly with increasing growth temperature although the growth rate remains nearly constant. Also, Fourier transform infrared spectroscopy indicates that hydrogen incorporation into the films is nearly negligible.
Carrier Lifetime Measurements by Microwave Photoconductive Decay Method at Low Injection Levels
Authors: Fujihira Chiyo , Morin Michel , Hashizume Hidehisa , Friedt Jean , Hirose Yasuhide Nakai
Published: February 2005

The minority carrier lifetime of Si wafers has been measured at very low injection levels by employing a newly developed microwave photoconductive decay (µ-PCD) technique. It is found that the effective lifetime is dramatically increased for the case of p-type Si when the injection level is reduced to two orders of magnitude less than the equilibrium value. In contrast to this, the n-type wafer lifetime remains almost un-changed even upon lowering the injection level. Also, it is shown that the different contamination levels of Fe in Si wafers are clearly discriminated by the measured lifetime.
Electron Trapping and Interface State Generation in PMOSFET's: Results from Gate Capacitance
Authors: C. H. Ling C. H. Ling
Published: February 2005

Significant generation of hot-carrier induced donor and acceptor interface states in PMOSFET's is observed for the first time from gate-to-drain capacitanceCgd^*s. Plotting the change ΔCgd^*sagainst gate bias reveals two peaks, attributed to donor and acceptor states. A voltage on the drain displaces the donor peak by approximately the amount of the applied voltage, but the acceptor peak shifts by a fixed amount.
Band-Edge Photoluminescence of SiGe/Strained-Si/SiGe Type-II Quantum Wells on Si(100)
Authors: Nayak Deepak K. , Usami Noritaka , Sunamura Hiroshi , Susumu Fukatsu Susumu Fukatsu , Yasuhiro Shiraki Yasuhiro Shiraki
Published: February 2005

High-quality completely lattice-relaxed SiGe buffer layer has been grown on Si(100) by using gas source molecular beam epitaxy. Pseudomorphic Si layer has been grown on this lattice-relaxed SiGe buffer layer to form SiGe/strained-Si/SiGe quantum wells. Intense band-edge photoluminescence has been observed from these quantum wells for the first time. Quantum confinement effect in SiGe/strained-Si/SiGe quantum well has been demonstrated from the systematic shift of photoluminescence energy peaks with the width of the quantum well.
Evidence of Zero Potential Spike Energy in AlGaAs/GaAs Heterostructure Emitter Bipolar Transistors
Authors: Chen H. R. , Lee C. P. , Chang C. Y. , K. L. Tsai K. L. Tsai , J. S. Tsang J. S. Tsang
Published: February 2005

The potential spike energy at the emitter junction of AlGaAs/GaAs heterostructure emitter bipolar transistors (HEBT) was directly measured for the first time. Experimental data revealed that emitter thickness as thin as 300 Å is thick enough to eliminate potential spike without compositional grading. It is found that the band bending in n-GaAs reduces the potential spike and hence very low offset voltage of 70 mV with high current gain of 150 can be obtained.
Crystal Growth of Tl-Based Cuprate Superconductors
Authors: Takei Humihiko , Sakai Fumiko , Hasegawa Masashi , Nakajima Satoru , Kikuchi Masae
Published: February 2005

Growth of Tl-based cuprate superconductor crystals has been investigated using a mixed state of solid with melt. Analyses by X-ray and SEM-EPMA reveal that the crystals are grown in a plate form with a developed c-plane with coexistence of two phases, Tl2Ba2CuO6 with Tl2Ba2CaCu2O8, or Tl2Ba2CaCu2O8 with Tl2Ba2Ca2Cu3O10, having common crystal axes. The growth feature is explained in terms of a stacking fault mechanism during lateral growth on the c-plane.
Dependence of Off-Diagonal Components of χ(3) on Substrate Temperature of Epitaxially Grown Vanadyl Phthalocyanine Films
Authors: Fang Shaoli , Kohama Keiichi , Hajime Hoshi Hajime Hoshi , Yusei Maruyama Yusei Maruyama
Published: February 2005

Single-crystalline vanadyl phthalocyanine films have been grown by the molecular beam epitaxy technique. The normalized off-diagonal ratio 3χ1221/χ1111 has been determined by circular-polarization third-harmonic generation measurement. It is revealed that the single-crystalline phase with 4mm symmetry can be distinguished from the C
∞υ polycrystalline phase by circular-polarization third-harmonic generation measurement, and the quality of the epitaxial film can be quantitatively analyzed by the normalized off-diagonal ratio of 3χ1221/χ1111.
Control of Liquid Crystal Alignment Using Stamped-Morphology Method
Authors: Lee Eung Sang , Vetter Peter , Miyashita Tetsuya , Uchida Tatsuo , Kano Mitsuru , Abe Munemitsu , Sugawara Kiyomi
Published: February 2005

We propose a new method to align liquid crystals using microgrooves that are fabricated by a stamping process. This rubless alignment method has the advantage of accurate control of the pretilt angle and azimuthal surface anchoring energy by means of changing the surface morphology. In this paper we discuss the control of the pretilt angle and the azimuthal surface anchoring energy in detail.
W-YBa2Cu3O7-y Point-Contact Junction at Millimeter-Wave
Authors: Kurosawa Tomizo , Atsushi Onae Atsushi Onae , Etsuo Kawate Etsuo Kawate
Published: February 2005

Experiments of up to the 8th harmonic mixing of 10 GHz have been carried out using point-contact junctions made with sharply tipped tungsten whiskers and sintered polycrystalline YBa2Cu3O7-y
at room temperature and in liquid nitrogen. Some features of the W-YBa2Cu3O7-y
point-contact junctions are described. The characteristics of the static current-voltage curve fitting to the 9th-order polynomial expression are discussed and the noise equivalent power is roughly estimated.
Magnetoresistance in [Cu/{Fe-Mn/M/Cu/M}] Spin-Valve Multilayers (M=Ni80Fe15Co5, Ni80Co20, Co90Fe10)
Authors: Hiroshi Sakakima Hiroshi Sakakima , Mitsuo Satomi Mitsuo Satomi
Published: February 2005

[Cu/{Fe-Mn/M/Cu/M}]
N
spin-valve multilayers (M=Ni-Fe-Co, Ni-Co, Co-Fe) were prepared by RF sputtering. The multilayers showed a considerably large magnetoresistance (MR) ratio (∼5%) at RT with a small transient field (≤30 Oe). The MR ratio increased with the repetition number N, whereas the MR ratio of Fe-Mn-capped multilayers such as Fe-Mn/[Ni-Fe-Co/Cu]
N
decreased with N, and the value was smaller than that of [Ni-Fe-Co/Cu]
N
or spin-valve multilayers [Cu/{Fe-Mn/Ni-Fe-Co/Cu/Ni-Fe-Co}]
N
.
Measurements of Diffusion Coefficient of CF2 Radical in DC Pulsed CF4 Discharge Plasma
Authors: Arai Toshihiko , Goto Miki , Asoh Yoshinori , Daisuke Takayama Daisuke Takayama , Tetuya Shimizu Tetuya Shimizu
Published: February 2005

Laser-induced fluorescence has been used to measure the CF2 radical ground-state densities after extinction of DC pulsed CF4 discharge plasma. From the measurement, the CF2 radical was shown to be removed mainly by a diffusion process. Its diffusion coefficient was found to be D=65 cm2·Torr·s-1 in CF4 at room temperature.
Implantation Induced Order-Disorder Transition in Ga0.52In0.48P/(Al0.35Ga0.65)0.5In0.5P Heterostructures
Authors: Hämisch York , Steffen Robert , Röntgen Peter , Alfred Forchel Alfred Forchel
Published: February 2005

The implantation induced transition from the ordered to the disordered state of Ga0.52In0.48P/(Al0.35Ga0.65)0.5In0.5P–layers was investigated by means of Ar+ ion implantation, rapid thermal annealing (RTA) and photoluminescence spectroscopy. The implantation dose and annealing temperature dependence of the luminescence was studied in the dose range from 1×109 cm-2 to 5×1013 cm-2 and in the temperature range from 500°C up to 1025°C. By an Ar+ dose of 2×1012 cm-2 the temperature of the order-disorder transition can be decreased by about 200°C compared to the transition temperature of only annealed samples. For annealing temperatures higher than 700°C a dose variation by less than one order of magnitude causes an emission energy blue shift of the GaInP luminescence band by about 100 meV due to a complete disordering of the previously ordered layers.
Improved Selectively δ-Doped GaAs/InGaAs Double-Quantum-Well Pseudomorphic HFET's Utilizing a Buried P-Layer on the Buffer
Authors: Kao Ming-Jer , Wei-Chou Hsu Wei-Chou Hsu , Hir-Ming Shieh Hir-Ming Shieh
Published: February 2005

This letter demonstrates a new double-quantum-well (DQW) selectively δ-doped GaAs/InGaAs HFET's utilizing a buried lightly doped p-layer on the GaAs buffer prepared by low-pressure metalorganic chemical vapor deposition (MOCVD). Pinch-off characteristic and transconductance are remarkably improved in the DQW HFET's by using a buried p-layer. The extrinsic transconductances of the DQW HFET's with and without the buried p-layer are 240 mS/mm and 190 mS/mm, respectively.
A Study on the Potential Structure of the Barrier in Ba1-xKxBiO3/Natural-Barrier/Au Structures
Authors: Inoue Masumi , Maezawa Masaaki , Tsukino Yoichiro , Yoshiaki Takai Yoshiaki Takai , Hisao Hayakawa Hisao Hayakawa
Published: February 2005

Ba1-x
K
x
BiO3(BKBO)/natural-barrier/Au junctions were fabricated and the potential structure of the barrier was investigated. These junctions showed very clear gap structure in the I-V characteristics. The energy gap parameter Δ was estimated to be 3.5 meV, which yielded 2Δ/k
B
T
czero=3.8. The potential structure of the barrier was estimated assuming a trapezoidal potential, which was revealed to be a good approximation. The barrier heights at the BKBO side and Au side were ∼100 meV and ∼300 meV, respectively, and the thickness of the barrier was 30 Å.
Record Low Threshold Current in Microcavity Surface-Emitting Laser
Authors: Numai Takahiro , Kawakami Takeshi , Yoshikawa Takashi , Sugimoto Mitsunori , Sugimoto Yoshimasa , Yokoyama Hiroyuki , Kenichi Kasahara Kenichi Kasahara , Kiyoshi Asakawa Kiyoshi Asakawa
Published: February 2005

We demonstrate a record low threshold current of 190 µA in a microcavity surface-emitting laser with a 5-µm-diameter airpost, in pulsed operation at room temperature with no heat sink. This low threshold current is attributed to high-quality epitaxial layers and a dry-etched smooth sidewall.
Scaling Analysis of Chemical-Vapor-Deposited Tungsten Films by Atomic Force Microscopy
Authors: Tatsuo Yoshinobu Tatsuo Yoshinobu , Hiroshi Iwasaki Hiroshi Iwasaki
Published: February 2005

We have studied the static surface roughness of 500-nm-thick tungsten chemical-vapor-deposited polycrystalline films on length scales between 5 and 5×104 nm, using atomic force microscopy. The interface width scales as a power of the system size for small system sizes (<1000 nm) but is constant for large sizes, which is in agreement with nonequilibrium interface growth theory. The scaling exponent (0.75±0.05) for short-length scales appears to be consistent with the recent prediction based on a conservative volume growth model. In the long-range regime, the rms value becomes larger as the substrate temperature is lowered.
Silicon Surface Imperfection Probed with a Novel X-Ray Diffraction Technique and Its Influence on the Reliability of Thermally Grown Silicon Oxide
Authors: Kitano Tomohisa , Hasegawa Eiji , Tsukiji Masaru , Akimoto Koichi , Kimura Shigeru , Shuichi Saito Shuichi Saito , Kazuko Ikeda Kazuko Ikeda
Published: February 2005

Silicon surface imperfection was investigated by an X-ray diffraction technique under the condition of simultaneous specular and Bragg reflections, using the tunability of synchrotron radiation in conjunction with an asymmetric reflection. The surface roughness was the main imperfection on the conventional mechanochemical polished silicon wafer, and this surface imperfection was reduced by a series of sacrificial oxidation procedures. The time-dependent dielectric breakdown (TDDB) characteristics were also improved by these procedures. In this way, the reliability of the metal oxide semiconductor capacitor was dependent on the surface imperfection of the silicon substrate.
Si-Doped InGaN Films Grown on GaN Films
Authors: Nakamura Shuji , Takashi Mukai Takashi Mukai , Masayuki Senoh Masayuki Senoh
Published: February 2005

High-quality Si-doped InGaN films were grown on GaN films for the first time. Strong and sharp band-edge (BE) emissions were observed at peak wavelengths between 400 nm and 425 nm, while deep-level emissions were not observed in photoluminescence (PL) measurements at room temperature. The intensity of BE emissions of Si-doped InGaN films was about 36 times stronger than that of undoped InGaN films and 20 times stronger than that of the blue emission (at 450 nm) of Mg-doped p-type GaN films. The smallest full width at half-maximum (FWHM) of the double-crystal X-ray rocking curve (XRC) from the Si-doped InGaN films was 6.4 minutes. This value of FWHM was the smallest ever reported for InGaN films.
High-Quality Nb/AlOx-Al/Nb Josephson Junctions with Gap Voltage of 2.95 mV
Authors: Kusunoki Masanobu , Yamamori Hirotake , Fujimaki Akira , Yoshiaki Takai Yoshiaki Takai , Hisao Hayakawa Hisao Hayakawa
Published: February 2005

The dependence of the gap voltage on impurities in Nb films is studied. The gap voltage is determined by the number of impurities included in the films. The impurities arise from the residual gas in the sputtering chamber before the deposition of Nb films. By reducing the impurities in the films, we obtain high-quality Nb/AlO
x
-Al/Nb Josephson junctions having the gap voltage of 2.95 mV which is close to that estimated from the energy gap of Nb bulk at 4.2 K. In addition, the use of a thin Al layer is also an important factor in obtaining excellent current-voltage characteristics.
Deposition Rate of Boron Nitride Films Using Plasma Jet Technique
Authors: Saitoh Hidetoshi , Morino Hiroki , Ichinose Yukio
Published: February 2005

A plasma jet apparatus was developed to obtain high-growth-rate deposition of boron nitride films. In this apparatus, the gas mixture of B2H6-NH3-H2 was excited into a plasma state by dc arc discharge. As the resulting deposits, thick films of boron nitride containing cubic phase nanocrystallites were seen on silicon single-crystal wafers. The deposition rate reached 40 µm/min at a substrate temperature of 900 K. This was 2000-4000 times larger than the deposition rates obtained previously using the rf plasma chemical vapor deposition technique. With addition of Ar to gas mixture, the deposition rate decreased to <20 µm/min. The volume fraction of cubic boron nitride in the deposits was dependent upon the substrate temperature under the conditions both with and without Ar.
A Newly Developed 300 kV Field-Emission Analytical Transmission Electron Microscope
Authors: Bando Yoshio , Kitami Yoshizo , Tomita Takeshi , Honda Toshikazu , Ishida Yukihisa
Published: February 2005

In order to carry out high-spatial-resolution analysis at the nanometer level, a 300 kV analytical transmission electron microscope with a field-emission gun has been developed. Some characteristic features of the new microscope are described and the results of the nanometer-level analysis are shown for silicon nitride and indium iron zinc oxide.
Optical Investigations of the Sidewall Recombination in Wet Etched InGaAs/InP-Wires
Authors: Jacobs B. , Emmerling M. , Forchel A. , Gyuro I. , Speier P. , Zielinski E.
Published: February 2005

We have investigated the optical properties of wet chemically etched InP/InGaAs-wires with widths between 100 nm and 10 µm for a wide range of excitation densities and energies. We observe that the non radiative recombination centers at the etched sidewalls can be saturated already at moderate excitation densities of 100 W/cm2. Avoiding saturation effects we obtain a surprisingly large sidewall recombination velocity of 107 cm/s at 77 K. The comparison of luminescence measurements at excitation energies above and below the InP band gap energy shows, that the non radiative recombination centers are located in the InGaAs quantum well.
Asymmetric Bias Injection Technique for Drung-Type Superconducting Quantum Interference Devices
Authors: Uehara Gen , Matsuda Naoki , Kazami Kunio , Kado Youichi Takada
Published: February 2005

An asymmetric bias current injection method is developed to reduce bias-caused noise in Drung-type SQUID (superconducting quantum interference devices) without adding extra coils. A measuring scheme for ∂Φ/∂I
b is tested, and it is demonstrated that the reduction is from 100 to 150 times that attained by the conventional SQUID biasing method. It is revealed that the direction of APF (additional positive feedback) coil winding is important in attaining this reduction.
Observations of the Initial Stage of Chemical-Vapor-Deposited Diamond Growth Using Transmission Electron Microscopy
Authors: Yagyu Hiroyuki , Mori Yusuke , Hatta Akimitsu , Toshimichi Ito Toshimichi Ito , Akio Hiraki Akio Hiraki
Published: February 2005

The initial stage of growth of diamond synthesized by microwave plasma-assisted chemical vapor deposition (CVD) on Si substrates has been observed using a transmission electron microscope (TEM). It is found that the CVD diamond particles are formed on the Si protuberances fabricated by etching of the substrate surface. A high-resolution TEM (HRTEM) image has revealed the morphology of the initial-stage crystal, the amorphous layer underneath the crystal, and the defects along {111} planes can be seen clearly. Multi-nucleation growth process on an atomic scale on the {111} surface is probable.
Preparation and Anisotropic Superconducting Properties of HgBa2CuO4 Thin Films
Authors: Adachi Hideaki , Mizuno Koichi , Toshifumi Satoh Toshifumi Satoh , Kentaro Setsune Kentaro Setsune
Published: February 2005

Thin films of HgBa2CuO4 have been grown with c-axis orientation perpendicular to (100) SrTiO3 substrates by sputtering deposition and subsequent annealing. The films exhibited sharp superconducting transition at 93 K.
Values of the upper critical field H
c2(0) estimated from the resistive measurements were 45 T and 565 T for themagnetic field H parallel with and perpendicular to the c axis, respectively. The Ginzburg-Landau coherence lengths were calculated to be 27 Å in the basal plane and 2.2 Å along the c axis, showing the anisotropy factor of 12. These values are almost similar to those of conventional p-type cuprate superconductors.
Electrical Breakdown at the Falling Edge of Rectangular Pulse Voltage Curve in Cyclohexane under Nonuniform Field Configuration
Authors: Yamada Hiroshi , Fujiwara Tamiya , Yamauchi Yoshibumi , Kusano Kazusa , Kimura Shingo , Tamada Koji
Published: February 2005

The electrical breakdown process in cyclohexane for a point-to-plane gap configuration has been studied, using an image converter camera and a photooptical current measuring technique. An actual breakdown was occasionally observed at the falling edge of microsecond rectangular pulse voltage. A field-increasing effect by plasma oscillation in the prebreakdown streamer and a polarization effect of the molecules in remainder gap in front of the stramer are proposed to account for the phenomenon.
Substrate Potential Effects on Low-Temperature Preparation of SrTiO3 Thin Films by RF Magnetron Sputtering
Authors: Shibuya Munehiro , Nishitsuji Mitsuru , Kitagawa Masatoshi , Kamada Takeshi , Hayashi Shigenori , Tamura Akiyoshi , Takashi Hirao Takashi Hirao
Published: February 2005

SrTiO3 films have been prepared by RF magnetron sputtering at a low substrate temperature of 200°C. The dielectric properties of the films deposited wherein substrate potentials were floated were fairly dependent on the film thickness, which was related to a change of the substrate potential at the initial stage of deposition. In order to control the substrate potential, positive DC bias voltages were applied on substrates, so that leakage current densities of the films were markedly reduced while their dielectric constants and structural properties remained almost the same. A 300-nm-thick film deposited with DC bias voltages >+5 V exhibited. good dielectric properties with a leakage current density of 1×10-7 A/cm2 and a dielectric constant of 90.
Characterization of Chemical-Vapor-Deposited Amorphous-Silicon Films
Authors: Shiraiwa Toshiaki , Sugiura Osamu , Kanoh Hiroshi , Asai Norihito , Usami Koh-ichi , Hattori Takeo , Masakiyo Matsumura Masakiyo Matsumura
Published: February 2005

We have studied post-hydrogenation characteristics and photo-absorption characteristics of amorphous-silicon films thermally deposited from disilane at 500°C. There is a critical post-hydrogenation temperature of about 400°C, below which both the density of hydrogen (deuterium) atoms on the surface and the activation energy of their diffusion constants are constant. Post-hydrogenation drastically enhances the decrease of the photo-absorption coefficient for photon energies less than the optical bandgap. The optimum density of hydrogen atoms introduced by post-hydrogenation was between 3 at% and 3.5 at%. The Urbach tail slope E
0 was 42 meV, i.e., about 8 meV lower than the typical value of the film deposited by plasma enhanced chemical vapor deposition (PECVD) method.
Low-Pressure Diamond Nucleation and Growth on Cu Substrate
Authors: Ojika Shin-ichi , Yamashita Satoshi , Kataoka Kazuhiro , Ishikura Takefumi , Yamaguchi Akira , Kawarada Hiroshi
Published: February 2005

We present a new technique for providing nuclei for diamond formation on nondiamond substrates and its application to the growth of diamond on a Cu substrate by chemical vapor deposition (CVD). This is a predeposition process in which the substrate is immersed in a CH4/H2 plasma formed by electron cyclotron resonance at a low pressure (0.1 Torr). The technique provides possibilities of nucleation over an increased area at temperatures lower (about 500°C) than usual, as well as improved process controllability. The grown diamonds on Cu exhibit a morphology significantly different from that of diamonds grown on Si.
Which Surfactant Shall We Choose for the Heteroepitaxy of Ge/Si(001)? –Bi as a Surfactant with Small Self-Incorporation–
Authors: Sakamoto Kunihiro , Kyoya Ken'ichi , Miki Kazushi , Hirofumi Matsuhata Hirofumi Matsuhata , Tsunenori Sakamoto Tsunenori Sakamoto
Published: February 2005

While the effectiveness of surfactants in Si/Ge heteroepitaxial growth has recently been reported, their disadvantages of self-incorporation and poor surface morphology restrict their practical application. We propose Bi as a surfactant which overcomes these disadvantages. We demonstrate by means of reflection high-energy electron diffraction and secondary ion mass spectrometry (SIMS) that Bi is an effective surfactant for Si/Ge heteroepitaxy in preventing both 3D islanding and surface segregation of Ge, while the amount of Bi incorporated in the epitaxial layer is smaller than the detection limit of the SIMS instrument (<5×1016 cm-3) and Bi can be removed easily by desorption at temperatures as low as 575°C.
Effect of Ultraviolet Irradiation on Surface Recombination Velocity in Silicon Wafers
Authors: Buczkowski A. , G. A. Rozgonyi G. A. Rozgonyi , F. Shimura F. Shimura
Published: February 2005

A theoretical explanation of surface recombination velocity reduction observed in silicon material irradiated by ultraviolet light is presented. The time dependent UV effect found in wafers covered by a native oxide results from a slow state discharge process which capture electrons during high energy photon exposure. The capture process is followed by a surface potential change which modifies the surface recombination velocity. As the slow states discharge, the original value of surface activity is recovered.
Observations of Anomalous Droplet Formation during the Molecular Beam Epitaxy of AlAs on GaAs (111)B Surfaces with an Alternating Source Supply
Authors: Morishita Yoshitaka , Goto Shigeo , Nomura Yasuhiko , Isu Toshiro , Yoshifumi Katayama Yoshifumi Katayama
Published: February 2005

A unique droplet behavior has been observed during the molecular beam epitaxial growth of AlAs on GaAs (111)B surfaces with an alternating source supply by in situ scanning microprobe reflection high-energy electron diffraction (µ-RHEED) in real time. It has been found that the intermixing of Al and Ga atoms strongly affects droplet formation during the initial four cycles of the growth. The droplet density increases and its size decreases as the growth cycle proceeds, and after the 5th growth cycle, the density and size are almost constant. The surface diffusion lengths of excess group-III atoms in the 1st and 5th cycles are estimated to be about 55 and 3.3 µm, agreeing with those obtained in the homoepitaxial cases of GaAs and AlAs, respectively.
Layer-by-Layer Growth of AlAs Buffer Layer for GaAs on Si at Low Temperature by Atomic Layer Epitaxy
Authors: Kitahara Kuninori , Ohtsuka Nobuyuki , Ashino Toshihiko , Masashi Ozeki Masashi Ozeki , Kazuo Nakajima Kazuo Nakajima
Published: February 2005

We developed a novel growth technique for AlAs on GaAs and Si substrates at a low temperature of 150°C. The low-temperature growth was achieved using atomic layer epitaxy (ALE) with trimethylamine alane as a group III source. Layer-by-layer growth of one monolayer per ALE cycle with a self-limiting effect was obtained on both substrates. Surface morphology of GaAs on Si was improved by the use of this AlAs as a buffer layer. The degradation of crystal quality, expected due to the growth of the GaAs active layer on the low-temperature buffer layer, did not occur.