bluuebunny/crossref_metadata_2025 huggingface dataset:
Valence-Subband Structure of Strained Quantum Wells
Authors: Matsuto Ogawa Matsuto Ogawa , Tanroku Miyoshi Tanroku Miyoshi
Published: October 2002

The valence-subband structures of strained quantum wells are calculated using the Luttinger-Kohn Hamiltonian taking into account the strain effect. Numerical results are presented in detail for InxGa1-x
As/InP single-quantum-well structures. The strain-dependent coupling is present among the heavy-hole bands, light-hole bands, and the spin-orbit split-off bands for the strained quantum wells. Based on the results, we have shown that the axial approximation used in conventional calculations is no longer valid. We have also demonstrated that spin-orbit coupling plays a significant role in band mixing of the valence band and cannot be neglected.
Current-Path Observation in Low-Dose SIMOX (Separation by Implanted Oxygen) Buried-SiO2 Layer
Authors: Kajiyama Kenji , Hashiguchi Yoshihiro , Ikematsu Yoichi , Hamaguchi Isao , Yano Takayuki , Nakajima Tatsuo , Masui Shoichi , Kawamura Keisuke , Masaharu Tachimori Masaharu Tachimori
Published: October 2002

Current paths in the buried- SiO2 layer of low-dose SIMOX (Separation by IMplanted OXygen) wafers are observed directly by micro-beam techniques both in plan and sectional views based on Cu-plated indications. Large-area current paths display particle traces on the surface-Si layer immediately above the current path. Higher annealing temperatures (≥1330° C) decrease micro-roughness along the buried- SiO2 front/back boundaries and reduce current-path density.
Interface Structure and Magnetic and Transport Properties for Co/Cu(111) Multilayers
Authors: Saito Yoshiaki , Inomata Koichiro , Nawate Masahiko , Honda Shigeo , Goto Atsushi , Yasuoka Hiroshi
Published: October 2002

The interface structure and magnetic and transport properties of Co/Cu(111) multilayers have been investigated. NMR is sensitive to the atomic configuration, and the changes of the interface structures (atomic configuration) between as-deposited sample and sample annealed at 200° C were observed by measuring the 59Co NMR spectra, although low and high angle X-ray diffraction patterns changed little. The interface structure was analyzed by simulating the 59Co NMR spectra. It was revealed that the atomic configuration is correlated with the magnetic and transport properties.
Optical Transmittance of Anodically Oxidized Aluminum Alloy
Authors: Saito Mitsunori , Shiga Yasunori , Miyagi Mitsunobu , Wada Kenji , Ono Sachiko
Published: October 2002

Optical transmittance and anisotropy of anodic oxide films that were made from pure aluminum and an aluminum alloy (A5052) were studied. The alloy oxide film exhibits an enhanced polarization function, particularly when anodization is carried out at a large current density. It was revealed by chemical analysis that the alloy oxide film contains a larger amount of unoxidized aluminum than the pure-aluminum oxide film. The polarization function can be elucidated by considering unoxidized aluminum particles that are arranged in the columnar structure of the alumina film. Electron microscope observation showed that many holes exist in the alloy oxide film, around which columnar cells are arranged irregularly. Such holes and irregular cell arrangement cause the increase in the amount of unoxidized aluminum, and consequently induces scattering loss.
Structural Studies on Silicon Ditelluride (SiTe2)
Authors: Taketoshi Kazuhisa , Andoh Fumihiko
Published: October 2002

We found a silicon ditelluride ( SiTe2) having the lattice constants (a
0=4.2887 Å, c
0=6.7330 Å) and tellurium (Te) positions along the c-axis ( z-parameter 0.255) different from the reported values, using electron diffraction and X-ray diffraction. The structure was cadmium iodide ( CdI2)-type of trigonal space group P3̄ml. The bond lengths of Si-Te and Te-Te were 3.013 Å and 4.125 Å, respectively. The reliability factor was 0.0125%. We also found that the new surface structure of SiTe2 was √ 3×√ 3/R30°. The atomic positions of Si and Te are (0, 0, 0) and (1/3, 2/3, 0), (2/3, 1/3, 0), respectively. The lattice is hexagonal with a
0
′=√ 3a
0=7.4282 Å of the two-dimensional space group of P6. The reliability factor is 0.07%. Three-dimensional ordering along the c-axis was observed, and the surface structure has a size corresponding to 2 cells of normal SiTe2.
Formation and Properties of AgInSe2 Thin Films Deposited from Alloy Chunks
Authors: Ema Yoshinori , Nobuyoshi Harakawa Nobuyoshi Harakawa
Published: October 2002

AgInSe2 thin films have been deposited on glass substrates from an evaporation source of alloy chunks at various substrate temperatures. In the deposition process, atomic and molecular species of Se and In evaporate first, followed by Ag. The components react with each other on the substrate to form Ag-In-Se alloys at elevated temperatures. The crystal structure varies depending on the substrate temperature. Above 400° C, chalcopyrite-type crystallites of AgInSe2 were found to be dominant in the film, and there were very few of sphalerite-type. On the whole Se atoms were deficient in the films. Co-evaporation of Se with the alloy chunks followed by additional annealing produces a film containing only chalcopyrite crystallites. The optical absorption edge could be clearly observed both in the transmission and the photoconductance spectra. Electrical properties are discussed.
Resistance Ratio Bridge Using Cryogenic Current Comparator with DC-Superconducting Quantum Interference Device Magnetometer
Authors: Nakanishi Masakazu , Kinoshita Joji , Tadashi Endo Tadashi Endo
Published: October 2002

A resistance ratio bridge using a cryogenic current comparator (CCC) with a dc superconducting quantum interference device (dc-SQUID) was developed. Its structure, driving circuit and principle of operation were based on those of a resistance ratio bridge using a CCC with a commercially available rf-SQUID.
Because of the small intrinsic noise of the dc-SQUID, its resolution was determined not by the dc-SQUID noise but by the thermal noise of the resistor being tested. The ratio of a resistor having a nominal resistance of 100 Ω and a resistor with that of 1 Ω was measured with an uncertainty of 1.1×10-8.
Analysis of a Laser-Cooled Mach-Zehnder Atomic Interferometer
Authors: Tetsuya Mukai Tetsuya Mukai , Fujio Shimizu Fujio Shimizu
Published: October 2002

Characteristics and operating conditions of an atomic Mach-Zehnder interferometer are discussed. It is shown that a laser-cooled ultracold atomic source and detection of interference by spatially resolved detector greatly improve the performance of the atomic interferometer.
Metrology of Atomic Force Microscopy for Si Nano-Structures
Authors: Masao Nagase Masao Nagase , Hideo Namatsu Hideo Namatsu , Kenji Kurihara Kenji Kurihara , Kazumi Iwadate Kazumi Iwadate , Katsumi Murase Katsumi Murase
Published: October 2002

A new, practical metrological method for atomic force microscopy (AFM) is proposed to determine the dimensions of Si nano-structures. In this method, the AFM image profile is expressed as a modeling equation which includes the critical dimensions of the sample and the tip. The dimensions are obtained from part of the measured AFM image as fitting parameters of the equation. It is demonstrated that the critical dimensions of the sample and the tip obtained by this method agree well with those measured by scanning electron microscopy in the nanometer range.
Low-Temperature Hole Mobility Anomaly in Compensated P-Channel Metal-Oxide-Semiconductor Field-Effect Transistor
Authors: Lu Wei-Lee , Guo Jyh-Chyurn , Kao Chin-Hsin , Hsu Charles Ching-Hsiang , Luke Su Lu Luke Su Lu
Published: October 2002

An anomalous hole mobility degradation effect at low temperature and low gate overdrive of a compensated p-channel metal-oxide-semiconductor field-effect transistor (PMOSFET) is reported. Measurements are performed with great care, including the temperature calibration of the device and measurement timing control to exclude unwanted self-heating effect. Methods to determine threshold voltage and effective mobility are discussed. The anomalous effect can be explained by the trapping or freezing out of the electrons ionized from donor level at the acceptor site. The additional charged center enhances the Coulomb scattering of conducting holes that are transported in this region.
Temperature Dependence of the Electrical Resistivity of Molten Silicon
Authors: Sasaki Hitoshi , Ikari Atsushi , Terashima Kazutaka , Shigeyuki Kimura Shigeyuki Kimura
Published: October 2002

The temperature dependence of the electrical resistivity of molten silicon was measured based on the direct-current four-probe method in the temperature range from the melting point (1,415° C) to 1,630° C. The variation of the resistivity in this temperature region was less than 0.7%, which is much smaller than previously reported values. The measured resistivity near the solodification point was about 72×10-6 Ω cm, which is about 8% smaller than previously reported values. The resistivity of molten silicon showed a local minimum in the range from 1,450° C to 1,500° C. The resistivity of molten silicon was calculated based on Ziman's formula. The temperature dependence of the measured resistivity was not reproduced when the structure factor S(Q) calculated by a simple hard-sphere model was substituted into Ziman's formula, but was reproduced by using the experimental data of S(Q) measured by Waseda which shows the first peak of asymmetric shape. This result suggests that the specific melt structure of molten silicon has a significant effect on the resistivity.
Construction and Performance Test of a Magnetically Levitated Transport System in Vacuum Using High-Tc Superconductors
Authors: Minami Hirofumi , Junpei Yuyama Junpei Yuyama
Published: October 2002

We have developed a magnetically levitated transport system in vacuum using the strong pinning force of high-T
c superconductors. This transport system consists of superconductors prepared by the quench-and-melt-growth (QMG) method and permanent magnets. The superconductors move within the cooling jacket inserted into the transport chamber. A transfer arm moves in the transport chamber without any contact or sliding, because stable levitation is brought about by magnetic interaction between the magnet attached to the arm and the superconductor. In this paper, structure and performance test results are described.
Orientation Dependence of Coherent Hole Oscillations in GaAs/AlGaAs Coupled Quantum Wells
Authors: Chun-Yen Chang Chun-Yen Chang , Ming-Feng Lu Ming-Feng Lu , Po-An Chen Po-An Chen , Cheng Juang Cheng Juang
Published: October 2002

Coherent hole tunneling dynamics in GaAs/AlGaAs coupled quantum wells (CQWs) based on (100)- and (111)-oriented GaAs substrates are investigated. The tunneling probability of the hole wave packet for a heavy-hole to heavy-hole (HH-HH) band and a light-hole to light-hole (LH-LH) band is described based on the results of a time-dependent analysis. It is demonstrated that the CQW HH-HH oscillation frequency on (100) substrates is larger than that on (111) substrates due to a significantly lighter in-plane effective mass. However, the LH-LH spatial tunneling oscillation frequency on (100) substrates is smaller than that on (111) substrates.
Experiments on Space-Division Multiplexing of Electron Waves in a Solid Using Andreev Reflection at the Si/Nb Boundary
Authors: Hatano Mutsuko , Saitoh Kazuo , Mitsuo Suga Mitsuo Suga
Published: October 2002

Artificial space-division multiplexing of electron-waves in mesoscopic Si with the Si/Nb boundary controlled through Andreev reflection is verified by using a sample with five electron-wave injectors separated by sub-micron spacing. The maximum injection power of electron-waves that maintains space-division multiplexing is 0.22 µ W when the distance between the injectors is 0.15 µ m. By applying space-division multiplexing, two-input switchable AND-OR operation based on threshold logic by a single device is confirmed.
A High Polarization and High Quantum Efficiency Photocathode Using a GaAs–AlGaAs Superlattice
Authors: Yoshimasa Kurihara Yoshimasa Kurihara , Tsunehiko Omori Tsunehiko Omori , Yasunori Takeuchi Yasunori Takeuchi , Masakazu Yoshioka Masakazu Yoshioka , Tsutomu Nakanishi Tsutomu Nakanishi , Syooji Okumi Syooji Okumi , Mmasabumi Tawada Mmasabumi Tawada , Kazuaki Togawa Kazuaki Togawa , Mitsuru Tsubata Mitsuru Tsubata , Toshio Baba Toshio Baba , Masashi Mizuta Masashi Mizuta , Raymond K. Alley Raymond K. Alley , Hideki Aoyagi Hideki Aoyagi , James E. Clendenin James E. Clendenin , Josef C. Frisch Josef C. Frisch , Gregory A. Mulhollan Gregory A. Mulhollan , Pablo J. Sáez Pablo J. Sáez , David C. Schultz David C. Schultz , Huan Tang Huan Tang , Klaus H. Witte Klaus H. Witte
Published: October 2002

A charge of 2.3×1011 electrons in 2.5 ns at a laser wavelength of 757 nm with a corresponding quantum efficiency (QE) of 2.0% measured at 752 nm was extracted from a -120 kV biased, 20 mm diameter, GaAs–AlGaAs superlattice photocathode. The maximum electron polarization measured with material from the same wafer, but in a different system, was 71% at 757 nm for a QE of 1.0% measured at 752 nm. The quantity and temporal distribution of the extracted charge is consistent with a space charge limitation, rather than a cathode charge limit. The performance of this type of cathode makes it a possible candidate for future linear colliders.
Peak Intensity Enhancement and Pulse Compression of a Picosecond Laser Pulse by Frequency Doubling with a Predelay
Authors: Zhang Tiejun , Kato Yoshiaki , Yamakawa Koichi , Daido Hiroyuki , Yasukazu Izawa Yasukazu Izawa
Published: October 2002

Theoretical investigation of frequency doubling of a short-duration, high-intensity laser pulse in a potassium dihydrogen phosphate (KDP) crystal is given. The coupled nonlinear equations for the parametric process, including the third-order nonlinear susceptibility, have been solved. By applying a time delay between the extraordinary and ordinary waves for the fundamental pulse in type-II phase matching, the group velocity mismatch and the nonlinear phase shift can be made to compensate each other, resulting in peak intensity enhancement and pulse width compression. The optimum conditions for the incident intensity, the crystal thickness and the predelay time have been derived. It is shown that intensity conversion efficiency of 440% accompanied by pulse width reduction from 1 ps fundamental pulse to 100 fs second-harmonic pulse is achieved for incident intensity of 50 GW/cm2.
Theory and Application of Optical Subharmonic Oscillator
Authors: Koichi Shimoda Koichi Shimoda
Published: October 2002

The theory of an optical subharmonic oscillator and its application are presented. The optical subharmonic oscillator is composed of a mixer, a harmonic generator and amplifiers. Steady-state operation and buildup of subharmonic oscillations are analyzed under a plane-wave approximation. Fourier synthesis of the subharmonics and their harmonics can produce a train of sub-femtosecond or femtosecond pulses of arbitrary shapes. In addition, a novel scheme of optical frequency measurement can be constructed using the optical subharmonic oscillators. A practical system of absolute frequency measurement is proposed.
Tunnel Gap Imaging Investigation of Voltage Dependence of Molecular Images Obtained by Scanning Tunneling Microscope
Authors: Kimura Masahiro , Okumura Akihiko , Miyamura Kazuo , Yohichi Gohshi Yohichi Gohshi
Published: October 2002

The molecular images obtained by scanning tunneling microscope (STM) exhibit bias voltage dependence, and at low bias voltage, the molecular images disappear. This voltage dependence of STM molecular images is investigated by the tunnel gap imaging (TGI) technique using STM equipment. TGI is a technique that maps out the vertical variation of the tunnel current by measuring the tunnel gap width dependence of the tunnel current at each pixel. It is shown that the tip is repelled from the surface by 5-6 nm when the bias voltage is increased by about 1 V.
Marked increase in the apparent corrugation accompanies this phenomenon. The mechanism of STM molecular image formation is discussed in terms of the vertical distribution of the local density of states (LDOS).
Study of Gas Recycling in the GAMMA 10 Tandem Mirror Based on Numerical Model Calculations
Authors: Katsuhiko Tsuchiya Katsuhiko Tsuchiya , Yousuke Nakashima Yousuke Nakashima , Kiyoshi Yatsu Kiyoshi Yatsu , Mamoru Shoji Mamoru Shoji , Makoto Ichimura Makoto Ichimura , Naohiro Yamaguchi Naohiro Yamaguchi , Masaaki Inutake Masaaki Inutake , Teruo Tamano Teruo Tamano
Published: October 2002

In this paper, we describe a gas recycling model based on atomic and molecular processes. This model assumes that hydrogen molecules cause various reactions with ions or electrons in a steady-state and uniform plasma. Enhancement of fuelling due to the recycling is evaluated on the basis of the calculated probabilities of neutral and ion production by using the rate coefficients of these reactions. For Ion cycrotron range of frequency (ICRF)-heated plasmas, the results derived from this model are compared with experimental results obtained by using pressure-balance equations and the experimental data. Good agreement is found between both results. This means that this model contributes to our understanding of the recycling mechanism in the GAMMA 10 tandem mirror device as well as in toroidal devices.
Simple Method for Measurement of Decay Rate in Superconducting Magnet
Authors: Yasuhiro Nakamura Yasuhiro Nakamura , Akio Iwasa Akio Iwasa , Akio Fukushima Akio Fukushima
Published: October 2002

We have fabricated a simple and inexpensive sensor for measurements of decay rate of a magnetic field under a persistent mode in superconducting magnets using the magnetoresistance of a commercial copper wire of 0.1 mm diameter. We have found that the magnetoresistance of the copper wire has good reproducibility and no hysteresis up to 15 T at 4.2 K. Using this copper wire sensor, we can measure the decay rate with an accuracy of 1 ppm in the persistent mode of 15 T at 4.2 K. We also found that commercial GaAs Hall elements can be used for low temperatures experiments and that this copper wire sensor has advantages in terms of reproducibility and hysteresis compared with GaAs Hall elements.
Characterization of Thin-Film Interference Effect due to Surface Roughness
Authors: Nagata Hitoshi , Yamaguchi Atsumi , Kawai Akira
Published: October 2002

The normal and diffuse reflectivity from a resist/aluminum system were measured with various resist thicknesses. The average surface roughness σ a of aluminum surfaces varied from 5.5 to 10.5 nm upon changing the sputtering conditions. The diffuse reflectivity at the air/aluminum interface increases with surface roughness. This tendency is enhanced as the wavelength of incident light decreases. The interference effect for the resist/aluminum system decreases as the surface roughness increases. This tendency is enhanced when the resist absorptivity decreased. These results are analyzed with using the help of the “Swing” model.
Optical Memory Effect of Bacteriorhodopsin under an Electric Field
Authors: Okazaki Choichiro , Kazuo Takeda Kazuo Takeda
Published: October 2002

Optically induced absorption changes in bacteriorhodopsin under an electric field are investigated. A new intermediate appears due to light illumination under an electric field at room temperature. This optically induced state remains stable until it is again illuminated. The application of an electric field appears to change the energy level of bacteriorhodopsin molecules. Results show that an optical-writing, optical-erasing memory using bacteriorhodopsin which can function at room temperature can be fabricated.
Ultra-Shallow Depth Profiling of Arsenic Implants in Silicon by Hydride Generation-Inductively Coupled Plasma Atomic Emission Spectrometry
Authors: Matsubara Atsuko , Kojima Hisao , Itoga Toshihiko , Keiichi Kanehori Keiichi Kanehori
Published: October 2002

High resolution depth profiling of arsenic (As) implanted into silicon wafers by a chemical technique is described. Silicon wafers are precisely etched through repeated oxidation by hydrogen peroxide solution and dissolution of the oxide by hydrofluoric acid solution. The etched silicon thickness is determined by inductively-coupled plasma atomic emission spectrometry (ICP-AES). Arsenic concentration is determined by hydride generation ICP-AES (HG-ICP-AES) with prereduction using potassium iodide. The detection limit of As in a 4-inch silicon wafer is 2.4×1018 atoms/cm3. The etched silicon thickness is controlled to less than 4±2 atomic layers. Depth profiling of an ultra-shallow As diffusion layer with the proposed method shows good agreement with profiling using the four-probe method or secondary ion mass spectrometry.
Annealing Effects on the Hall Properties of Hg1-xCdxTe Heterolayers Grown by Liquid Phase Expitaxy
Authors: Yang Tian-Juh , Tai-Bor Wu Tai-Bor Wu
Published: October 2002

Hg1-xCdxTe (MCT) heterolayers consisting of a wide-band-gap layer on the top of a narrow-band-gap one were grown on (111)B CdTe substrates by liquid phase epitaxy from Te-rich solution. Both N-on-p and P-on-n type heterostructures were obtained by extrinsical doping of the top layer with Ga or Sb and a post-growth heat treatment. A two-zone annealing of the Ga-doped heterolayers was done for obtaining the N-on-p structure, and satisfactory electrical properties were obtained. On the other hand, a two-step two-zone annealing of the Sb-doped heterolayers was conducted for the P-on-n structure. A high temperature annealing was first performed to activate the p-type characteristics of the Sb-doped layer, and a low temperature annealing was subsequently conducted to convert the conductivity of the active layer (i.e., the bottom layer) from p- to n-type. The formation of P on n structure was confirmed by measurement of magnetic field dependent Hall coefficient of the heterolayers and data fitting with a three-carrier Hall coefficient model.
Power-Law Critical-State Model for Magnetization of Type-II Superconductors
Authors: Johansen Tom H. , Yuri Galperin Yuri Galperin , Harald Bratsberg Harald Bratsberg
Published: October 2002

The magnetization of a type-II superconductor obeying the power-law critical state model J
c = K
B
-n
is discussed for the case of an infinitely long rectangular bar placed in a parallel field. Explicit formulas are derived for all branches of the high-field hysteresis loop. Both the infinite slab and circular cylinder geometries are included as special cases. It is shown that the vertical width of the hysteresis loop has the asymptotic high-field behavior ΔM(B
a) ∼J
c(B
a), with a prefactor given by the geometrical aspect ratio. Also, two more terms in the functional expansion of ΔM { J
c} are derived. These terms are shown to vanish rapidly when the applied field exceeds the full penetration value. This allows for a new way of extracting J
c(B) from magnetization data.
Resistivity Oscillation of Ti Film During Growth
Authors: Iida Shoji , Abe Sinji , Hidemura Yoshikazu
Published: October 2002

Very thin Ti films have resistivities with film-thickness-dependent osciliatory characteristics. Experimental results show that with H2, CO2 and O2 gas adsorption on the film surface, the film structure and film components have little influence on the resistivity oscillation. Furthermore, the oscillation amplitudes are sensitive to the surface flatness. The resistivity oscillation is considered to occur by a modulation of the electron transmission, in the matching of two electron wave-functions at the interface of film/substrate and vacuum/film.
RuO2 Bottom Electrodes for Ferroelectric (Pb, La)(Zr, Ti)O3 Thin Films by Metalorganic Chemical Vapor Deposition
Authors: Takagi Takeshi , Oizuki Isamu , Kobayashi Ichizo , Masaru Okada Masaru Okada
Published: October 2002

RuO2 thin films were grown on various substrates by metalorganic chemical vapor deposition (MOCVD) using Ru(C11H19O2)3. The films produced at 350° C in O2 had a tetragonal rutile structure and a resistivity of 60 µΩ cm with excellent adhesion. From the viewpoint of integrated device applications, lanthanum-modified lead zirconate titanate (PLZT) films were also prepared by MOCVD.
The RuO2 films were found to serve as effective diffusion barriers for PLZT and MgO.
Significant interdiffusion at RuO2/Si and RuO2/SiO2 interfaces occurred during the deposition of PLZT films, and annealing of RuO2 film considerably depressed the interface reactions. Ta2O5 film served as an excellent barrier against the interface reaction between RuO2 and Si. The dielectric and ferroelectric properties of PLZT thin films on the RuO2/MgO and RuO2/Ta2O5/Si substrates were superior compared to those observed with RuO2/Si and RuO2/SiO2/Si substrates.
Determination of Elastic Stiffness and Piezoelectric e- and d-Constants of Piezoelectric Ceramic from Ultrasonic Velocity and Dielectric Constant
Authors: Sasaki Yukihiko , Ochiai Tsutomu , Takeuchi Yoshio , Shigeo Hayashi Shigeo Hayashi
Published: October 2002

Ultrasonic velocities and dielectric constants were measured along different directions on the X-Z plane of a Pb(Zr0.52Ti0.48)O3 ceramic (poling direction is along the Z-axis). A complete set of values of elastic stiffness constants and piezoelectric e- and d-constants have been obtained by the least squares method from the velocities and dielectric constants.
Temperature Dependence of ZnS Growth with Atmospheric-Pressure Metalorganic Vapor Phase Epitaxy Using Ditertiarybutyl Sulfide
Authors: Toshio Obinata Toshio Obinata , Katsuhiro Uesugi Katsuhiro Uesugi , Go Sato Go Sato , Ikuo Suemune Ikuo Suemune , Hideaki Machida Hideaki Machida , Norio Shimoyama Norio Shimoyama
Published: October 2002

Quadrupole mass spectrometric study of the decomposition of ditertiarybutyl sulfide (DtBS) showed that DtBS decomposes at low temperatures above 300°C. The growth of ZnS with metalorganic vapor phase epitaxy (MOVPE) using diethylzinc (DEZn) and DtBS showed the growth rate of more than 1 µm/h at ∼300°C with moderate flow rates of the precursors. These studies demonstrate the superiority of DtBS for low-temperature growth of S-containing II-VI semiconductors. However, the decrease of the growth rate was observed at higher temperatures under the growth condition limited by DtBS supply. We examined the reason for this phenomenon and attributed it mainly to the decrease of the transport efficiency of DtBS to the growing surface due to thermal cracking of DtBS during transport, which was caused by the excessive difference between the growth temperature and the decomposition temperature of the precursor.
Propagation Characteristics in 70 GHz Solid-Plasma Waveguide Containing n-InSb Slab with Light Irradiation
Authors: Obunai Tetsuo , Tsuyoshi Takeda Tsuyoshi Takeda
Published: October 2002

The transmission characteristics of a 70 GHz transversely magnetized partially filled solid-plasma waveguide can be varied by irradiating the plasma material with a semiconductor laser. The experimental results are explained by the increase in the slow surface wave resonant magnetic field in the waveguide. These findings indicate the possibility of controlling the propagation characteristics of the slow surface wave in the solid-plasma waveguide by means of optical injection.
Characterization of GaAs P-N Structures Grown on GaAs(111)A Substrates Using Controlled All-Silicon Doping
Authors: Fujita Kazuhisa , Toshihide Watanabe Toshihide Watanabe
Published: October 2002

GaAs p-n structures have been grown on a GaAs(111)A substrate by controlling the molecular beam epitaxy (MBE) growth conditions using only Si dopant. Cathodoluminescence (CL) spectra and I-V characteristics for the samples confirm the p-n structure. However, the quality of p-n structure is strongly affected by pausing after changing the growth conditions; as the pausing time is decreased, the breakdown voltage increases and the peak intensity of the emission spectrum increases drastically. Furthermore, for a pausing time of 1 min, emission in the p-layer appears at 14 K with increasing forward current; this indicates a decrease in the deep levels. As a result, strong emission of 875 nm is observed even at room temperature.
Magnetotransport in Hexagonal and Rectangular Antidot Lattices
Authors: Junichi Takahara Junichi Takahara , Akira Nomura Akira Nomura , Kenji Gamo Kenji Gamo , Sadao Takaoka Sadao Takaoka , Kazuo Murase Kazuo Murase , Haroon Ahmed Haroon Ahmed
Published: October 2002

In order to investigate anisotropic transport in various types of lattices, two-dimensional electron gas in the hexagonal and rectangular antidot lattices are measured. Magnetoresistance is isotropic in hexagonal lattice, but anisotropic in the rectangular lattice with circular antidots. The influence of antidot shapes upon anisotropic transport is also investigated in the rectangular lattice. It is found that the anisotropic transport is sensitive to the arrangement and the shape of antidot potential and anomalous peaks are observed in rectangular lattice with ellipsoidal antidots. The origin of the anomalous peaks is discussed. In both lattices quenching of the Hall effect is observed and the positions of commensurate peaks in Hall resistance shift to higher field than that in magnetoresistance. These effects cannot be explained by the pinned orbit model.
Formation and Characterization of GaAs Quantum Wires at Giant Step Edges on Vicinal (110) GaAs Surfaces
Authors: Misaichi Takeuchi Misaichi Takeuchi , Kazuhiro Shiba Kazuhiro Shiba , Kazuki Sato Kazuki Sato , Hu Kun Huang Hu Kun Huang , Koichi Inoue Koichi Inoue , Hisao Nakashima Hisao Nakashima
Published: October 2002

We report the formation of GaAs quantum wires using giant step structure formed during molecular beam epitaxial growth of AlGaAs on vicinal (110) GaAs surfaces. Atomic force microscope observation indicates that the steps extend to over several µm and are coherently aligned. The growth of an AlGaAs/GaAs quantum well (QWL) on the giant step structure forms quantum wires (QWRs) along the step edges. Carrier confinement into the QWRs is caused by the increase of well width (well-width modulation) and the decrease of Al composition in the AlGaAs barriers (barrier-compositional modulation), which are confirmed by transmission electron microscope observation. Redshift and strong polarization parallel to the wire direction in the photoluminescence spectra support carrier confinement into the GaAs QWRs.
Dual Electron Waveguide Devices: the Quest for Electron Directional Coupling
Authors: Jesús A. del Alamo Jesús A. del Alamo , Cristopher C. Eugster Cristopher C. Eugster
Published: October 2002

In our quest to demonstrate electron directional coupling, the coherent tunneling of electrons between two electron waveguides, we have investigated split-gate dual electron waveguide devices. With the structure biased in a “leaky" electron waveguide configuration we have carried out extensive observations of one-dimensional (1D) to two-dimensional (2D) tunneling between a waveguide and a neighboring two-dimensional electron gas. These tunneling spectroscopy experiments have provided the first glimpse of the one-dimensional density of states of a 1D electronic system. We have also carried out experimental observations of 1D to 1D tunneling between two electron waveguides. Demonstrating electron directional coupling will still require the development of a new generation of ultrashallow heterostructures with sharp confining potential barriers.
Possibility of High-Temperature Evaluation of Phase Coherent Length of Hot Electrons in Triple-Barrier Resonant Tunneling Diodes
Authors: Michihiko Suhara Michihiko Suhara , Riichiro Takemura Riichiro Takemura , Kazuhito Furuya Kazuhito Furuya
Published: October 2002

To investigate the possibility of estimating hot electron phase coherence at high temperature, the current-voltage (I-V) characteristic of a triple-barrier resonant tunneling diode (TBRTD) is analyzed taking phase breaking into account. When the central barrier width is larger than 7 nm in GaInAs/InP TBRTD, the width of the peak in the I-V curve is determined predominantly by the phase breaking. Therefore the peak width provides the information of the phase coherent length of the hot electrons. It is shown that the phase coherent length can be estimated up to 100 K using TBRTD.
Wannier-Stark Localization in Superlattices
Authors: Hamaguchi Chihiro , Yamaguchi Masahito , Nagasawa Hidekazu , Morifuji Masato , Carlo Aldo Di , Vogl Peter , Böhm Gerhard , Tränkle Günter , Weimann Günter , Nishikawa Yuji , Muto Shunichi
Published: October 2002

We present experimental and theoretical evidence for Wannier-Stark (WS) oscillations in the DC electric current through reverse-biased highly doped p-i-n GaAs diodes. The intrinsic region in the diode contained seven (GaAs)5/(AlAs)2multi-quantum wells. Carrying out these transport experiments at low temperatures, we found periodic WS oscillations in the second derivative of the Zener current, which is in qualitative agreement with theoretical predictions based on a realistic multiband and multichannel scattering theory. These findings resolve long-standing controversies about the existence of Wannier-Stark levels in the Zener tunneling current.
Magnetic Oscillation of Luminescence Energy in Asymmetric Quantum Wells
Authors: Takuma Tsuchiya Takuma Tsuchiya , Shin'ichi Katayama Shin'ichi Katayama , Tsuneya Ando Tsuneya Ando
Published: October 2002

Magnetic-field dependence of luminescence energy due to recombination of a two-dimensional electron and a photogenerated free hole in one-side-doped n-type GaAs/AlGaAs single quantum wells is calculated. The luminescence energy shows an anomalous shift when the Fermi energy is in an energy gap between adjacent Landau levels. The direction of this energy shift depends on the well width. This is due to well-width dependence of screening strength of two-dimensional electron gas for holes.
Electrical Characteristics of Thin-Film Transistors with Double-Active-Layer Structure
Authors: Tsai Meng-Jin , Wang Ping-Wei , Su Huan-Ping , Huang-Chung Cheng Huang-Chung Cheng
Published: October 2002

Thin-film transistors (TFTs) with a double-active-layer (DAL) structure have been proposed and found to exhibit two kinds of special electrical characteristics. One is the improvement of current drivability and transconductance as compared to the traditional structure. The other is the double-switching characteristics caused by the bi-transistor action. By means of a buried oxide separating the conduction channel into two parts, carrier transport could be enhanced due to the reduction of the vertical electric field. In addition, the weak avalanche breakdown for the top channel results in hole accumulation in the top poly-Si/buried oxide interface, further promoting the conduction of the bottom active layer, leading to the novel double-switching properties.
A Complete Model of Lifetime Distribution for Electromigration Failure Including Grain Boundary and Lattice Diffusions in Submicron Thin Film Metallization
Authors: Kuan-Yu Fu Kuan-Yu Fu
Published: October 2002

A complete model of electromigration failure lifetime distribution is illustrated in detail in this paper. The proposed theory can be divided into two portions: the physical model and the statistical model. As a result of the combination of these models, the electromigration lifetime distribution as a function of line width and temperature is generally predicted. Experiments have been conducted to verify the validity of this model and reported previously. Various theoretical aspects and implications of this model are discussed in this paper. Empirically, it is found that a significant portion of the increase in the shape factor with the decrease in line width can be attributed to the increase in the temperature standard deviation for narrower lines. Based on this model and coupled with the experimental observations, it is shown that the design rule scaling suffers a steep drop with line width in the deep submicron region. As a result, it will be difficult for the bamboo structure in practice to salvage thin film metallization from electromigration susceptibility for deep submicron microchip technologies. In order to meet the reliability specification for deep submicron devices, other alternatives are considered and discussed.
Friction Force Microscopy Study of the Langmuir-Blodgett Films with Different Molecular Structures
Authors: Fujiwara Ichiro , Kamei Takahiro , Jun'etsu Seto Jun'etsu Seto
Published: October 2002

The microscopic frictional properties of Langmuir-Blodgett (LB) films were investigated with a friction force microscope (FFM). At first, the microscopic frictional properties of LB films with different molecular structures were investigated. It is found that the friction coefficient of a tilt LB film are smaller than that of Ba arachidate. It is suggested that the friction coefficient of the LB film which alkyl chains are tilted with a large limiting area is smaller than that of the LB film with a small limiting area. Second, molecular level friction properties of behenic acid LB films were investigated. The molecular resolution image of the friction force is obtained. It is found that the FFM image shows the two dimensional regularity and the period of the regularity is 0.48 nm and 0.52 nm respectively. The period of the regularity in the FFM image is in fair agreement with that of the atomic force microscope (AFM) image. The molecular simulation of the friction force is carried out using local density functional method for LB film model system. It is found that the period of the regularity of the lateral force is consistent with that of the potential energy. This indicates that the calculated results support the experimental results.
Structural Analysis of Langmuir-Blodgett Films of Alkylated Tetracyanoquinodimethanes
Authors: Katsuhiro Nichogi Katsuhiro Nichogi , Taro Nambu Taro Nambu , Akihito Miyamoto Akihito Miyamoto , Mutsuaki Murakami Mutsuaki Murakami
Published: October 2002

Structural characterization of alkylated tetracyanoquinodimethane (TCNQ) Langmuir and Langmuir-Blodgett (LB) films has been carried out. Scanning electron microscope (SEM) and atomic force microscope (AFM) observations reveal numerous platelet microcrystal domains in the alkylated TCNQ Langmuir films transferred onto a quartz substrate. The analysis of height distribution in the AFM data proves that these domains have periodic layered structure. The thickness of these layered structures agrees well with the d-values obtained by X-ray diffraction analysis of the alkylated TCNQ LB films. Moreover, the high-resolution AFM image and the d-value of the 2-dodecyl-TCNQ Langmuir film suggest that the structure of the second and the upper layers in the domains is identical to that of the single crystal. SEM and AFM measurements prove that the LB films consist of numerous platelet microcrystal domains which are superposed upon each other, resembling a mosaic structure. Therefore, the periodic structures observed in X-ray diffraction measurements of the alkylated TCNQ LB films are ascribed to the layered structure in these domains, although they are usually explained as well-defined multilayered structure.
A Rigorous Series Solution for a Thermal Dissipation System with a Diamond Heat Spreader on an Infinite Slab Heat Sink
Authors: Hui Ping , Hong Siang Tan Hong Siang Tan
Published: October 2002

We consider the problem of conductive heat dissipation from an infinite stripe of constant heat flux, through an infinitely-long rectangular rod diamond heat spreader and an infinite slab heat sink. Using the Fourier cosine series and the Fourier transform, we have developed series solutions for both the temperature distributions in the system and the average temperature over the heating stripe. The series coefficients are determined through an infinite set of linear algebraic equations. Considering the case of diamond heat spreader and copper heat sink, we have investigated the effects of the geometrical dimensions and the thermal conductivity of the spreader on the thermal behavior of the system for a given sink thickness. The main results are: (1) there exists a spreader thickness for achieving the minimum temperature at the top spreader surface; (2) the commonly-used assumption of isothermal spreader-sink interface is valid for a relatively thicker spreader compared to the heating-stripe width; (3) increasing the ratio of the heat spreader width to the heating-stripe width beyond 30 does not reduce the average temperature significantly, indicating the existence of an effective spreader width; (4) for lowering the surface temperature, the spreader width is the most effective and practical design parameter over the thickness and the thermal conductivity.
Metal Alkoxide Solution-Derived Epitaxial Lead Titanate-Based Thin-Film Optical Waveguides
Authors: Nashimoto Keiichi , Nakamura Shigetoshi , Hiroaki Moriyama Hiroaki Moriyama
Published: October 2002

Lead titanate-based thin films were prepared for optical waveguide studies by nonhydrolyzed methoxyethoxide-solution-derived solid-phase epitaxy. PbTiO3 thin films crystallized with preferred (001) and (100) orientations on SrTiO3 (100) and MgO (100), respectively. PLT (28/100) thin films had obvious grain structure although they crystallized with a single (110) orientation on sapphire (011̄2) substrates. Epitaxial PZT thin films with a single (100) orientation crystallized on MgO (100) also had obvious grain structure. Epitaxial PZT (52/48) thin films on SrTiO3 (100) had a single (001) orientation, rocking curve full width at half-maximum of around 0.1°, and smooth surface of rms roughness less than 2 nm. The epitaxial PZT thin films on SrTiO3 showed optical propagation loss as small as 8 dB/cm at 633 nm.
Epitaxial Growth of BaTiO3 Thin Films and Thier Internal Stresses
Authors: Lee Song-Tae , Fujimura Norifumi , Taichiro Ito Taichiro Ito
Published: October 2002

Effects of substrate pre-treatment and O2 partial pressure on the epitaxial growth of sputter-deposited BaTiO3 films on (100)MgO have been studied. When the film thickness is 20 nm, significant differences in the surface crystallinity and morphology of the films are produced by HCl etching of the substrate surface. In 200-nm-thick films, on the other hand, there is no significant difference in the crystallinity between films on etched and as-received substrates. Differences in surface structure with increasing film thickness are also observed. The lattice constant parallel to the film thickness of the 20-nm-thick films is smaller than the theoretical value, and in the 200-nm-thick films, the lattice constants both perpendicular and parallel to the growth direction are larger than those of the BaTiO3 bulk material. The stress change can be well explained in terms of epitaxial restriction from the substrate and peening effect of O species during sputtering.
Phase-Change Optical Recording Films with AgInTe 2–Sb–Te System
Authors: Tatsuhiko Matsushita Tatsuhiko Matsushita , Akio Suzuki Akio Suzuki , Tomoki Nishiguchi Tomoki Nishiguchi , Keiji Shibata Keiji Shibata , Masahiro Okuda Masahiro Okuda
Published: October 2002

Reversible optical change due to laser irradiation or thermal annealing in amorphous films of the composition triangle AgInTe2-Sb-Te is described. Distinctive features are that there are a composition H (Ag9In14Te37Sb40) representing the best cyclability (≈106) for static repetition tests and a composition L (Ag8In8Te46Sb38) showing the largest reflectivity difference (≈26%) between the as-deposited and the annealed states at λ=830 nm.
Thermal Effects in Properties of Photovoltaic Currents of Pb(Zr, Ti)O3 Thin Films
Authors: Matsumura Akira , Kamaike Yasuyuki , Horiuchi Toshihisa , Shimizu Masaru , Shiosaki Tadashi , Kazumi Matsushige Kazumi Matsushige
Published: October 2002

Thermal effects in the characteristics of photovoltaic currents of Pb(Zr, Ti)O3 (PZT) thin films were studied from room temperature up to 360° C. The photovoltaic currents at a steady state increased with increasing temperature and then decreased above 250° C. By conducting annealing for positively or negatively poled samples, the traces of photovoltaic currents gradually became symmetric, suggesting the improvement of crystallinity of PZT thin films and/or the formation of a symmetric pair of Schottky junctions at two interfaces with electrodes. Furthermore, this suggestion was supported by the significant improvement in the characteristics of hysteresis loops upon annealing.
Characteristics of the Ultrasonic Linear Motor Using Radial and Nonaxisymmetric Vibration Modes of an Annular Plate
Authors: Takano Takehiro , Tomikawa Yoshiro
Published: October 2002

This paper deals with an ultrasonic linear motor using nonaxisymmetric ((1, 1)) vibration and radial (R, 1) vibration modes of a piezoelectric ceramic annular plate. A new method of making these modes degenerate is proposed. By applying this method to a vibrator, the neutral axis of vibration for ((1, 1))-mode is fixed on the prescribed position, and the difference between the two resonance frequencies is adjusted to the optimum state for a stator vibrator. The construction and some operational characteristics of the linear motor are presented. The maximum efficiency of the prototype motor was about 48%.
Measurements of Complex Piezoelectric d33 Constant in Ferroelectric Ceramics under High Electric Field Driving
Authors: Yasuyoshi Saito Yasuyoshi Saito
Published: October 2002

A measurement system has been designed and constructed which is capable of automatic data collection for complex piezoelectric d
33 constant (amplitude and phase), field-induced polarization and switching current under high electric field driving in ferroelectric materials. The system is based on the direct piezoelectric effect and d
33 constant can be measured down to about 10 pC/N.
Using this system, low and high electric field piezoelectric responses were examined in soft lead zirconate titanate (PZT) ceramics by comparing the data with the total polarization and strain changes. At a low a.c. electric field, the observed complex piezoelectric d
33 constant measured by the direct piezoelectric method is equal to the values measured by the converse piezoelectric method, and the field-induced strain is fully accounted for the complex piezoelectric d
33 constant. At a high electric field, however, the amount of total strain becomes larger than the estimated strain by integrating d
33 in terms of electric field. The contribution of irreversible domain wall motion to the total strain change was found to approach 51.5% at the electric field strength of +1400 V/mm. The newly developed system can quantitatively determine the lattice motion and reversible domain wall motion-induced strain component in the total strain response under the high electric field driving in piezoelectric ceramics.
Energy Trapping Characteristics for Thickness Extensional Vibration of Preferentially Orientated ZnO Ceramics
Authors: Ando Akira , Minamikawa Tadahiro , Takagi Hiroshi , Kunisaburo Tomono Kunisaburo Tomono
Published: October 2002

The energy trapping characteristics for thickness extensional (TE) mode vibration were studied for preferentially orientated zinc oxide (ZnO) ceramics fabricated by the chemical transfer method. The results of both the dispersion curve analysis and the finite-element method (FEM) simulation indicate that frequency-lowering-type energy trapping is possible for ZnO ceramics. The number of generating mode in the ZnO ceramic plate decreases with decreasing diameter of the electrode in the experiment. This means that the energy trapping characteristics were obtained on the ZnO ceramics. However single-mode energy trapping was not realized in this study.