bluuebunny/crossref_metadata_2025 huggingface dataset:
Selective Surface Doping Method of P Atoms in Lateral Solid Phase Epitaxy and Its Applications to Device Fabrication
Authors: Ishiwara Hiroshi , Toru Dan Toru Dan , Kazuichi Fukao Kazuichi Fukao
Published: February 2005

Growth characteristics and device application of the selective surface doping method in lateral solid phase epitaxy (L-SPE) are presented. In this method, P atoms are incorporated near the surface of amorphous Si (a-Si) films to enhance the L-SPE growth and the underlying undoped layers are used for device fabrication. First, the growth characteristics are investigated by changing thicknesses of the a-Si film and the P-doped layer, and a quantitative model to explain the experimental results is presented. Then, it is shown that redistribution of the P atoms during L-SPE annealing is negligibly small, and the P-doped layer is selectively etched by combination of a wet chemical etchant and subsequent reactive ion etching. Finally, metal-oxide-semiconductor field-effect transistors (MOSFETs) with upper and lower gate electrodes are fabricated in the undoped layer and the electrical properties of both the upper and lower channel FETs are investigated.
Fluorine Adsorption and Etching on Si(111):SiH Surface during Immersion in HF Solution
Authors: Satoru Watanabe Satoru Watanabe , Mayumi Shigeno Mayumi Shigeno
Published: February 2005

We examined the infrared spectrum of Si(111) after terminating its surface with silicon monohydride and immersing it in various concentrations of HF solution to induce fluorine adsorption. After immersion in HF solution, a part of the silicon monohydride surface was etched and (100), (010) and (001) steps composed of strained dihydrides appeared. The silicon-hydrogen stretching frequency for the monohydride was shifted by the fluorine adsorption. Angle-resolved X-ray photoelectron spectroscopy revealed that fluorine penetrates the silicon lattice as well as exists close to the surface. We conclude that fluorine does not terminate the surface silicon dangling bond but inhabits interstitial sites just below the silicon surface.
Josephson Effect in YBa2Cu3O7/Au-Ag/Pb Junctions
Authors: Yoshida Jiro , Hashimoto Tatsunori , Inoue Shinji , Mizutani Yoshihisa , Masayuki Sagoi Masayuki Sagoi , Koichi Mizushima Koichi Mizushima
Published: February 2005

A comprehensive study was carried out on the Josephson effect in YBCO/Au-Ag/Pb SNS junctions prepared on YBCO thin films with various crystal orientations. Most of the fabricated junctions showed a dc Josephson current with a clear Fraunhofer pattern dependence on the applied magnetic field, which ensured the uniformity of the fabricated junction structure. Experimental results were quantitatively compared with the conventional junction theory based on the Usadel equation. The junction characteristics were confirmed to be reasonably explained by a junction model in which a thin insulating or highly resistive layer was assumed to exist at the YBCO-Au interface.
NbN/MgO/NbN Josephson Junctions for Integrated Circuits
Authors: Aoyagi Masahiro , Nakagawa Hiroshi , Itaru Kurosawa Itaru Kurosawa , Susumu Takada Susumu Takada
Published: February 2005

Characteristics of the NbN/MgO/NbN Josephson junction for integrated circuits have been investigated. The deposition process of the MgO film for the tunnel barrier was systematically investigated to obtain the controllability of the Josephson critical current density. The reproducibility of the Josephson critical current density was improved to ±28% with the critical current density of 610 A/cm2 and ±20% with the critical current density of 16 kA/cm2. The uniformity of the Josephson critical current density across a 3 cm-square area on the substrate was improved to ±12% with the critical current density of 650 A/cm2.
High-Speed GaInAs PIN Photodiodes with Low Series Resistance
Authors: Sakakibara Katsutoshi , Morio Wada Morio Wada , Yoichi Sekiguchi Yoichi Sekiguchi
Published: February 2005

We have demonstrated high-speed GaInAs PIN photodiodes fabricated by low-pressure metalorganic vapor-phase epitaxy. To reduce series resistance, a heavily sulfur-doped InP layer and graded band-gap (Ga
x
In1-x
As x=0.47 to 0) contact layer were incorporated into the photodiodes. Furthermore, to reduce stray capacitance, a semi-insulated substrate was used and mesa islands were passivated with polyimide. As a result, the RC time constant then decreased and a bandwidth of 31 GHz at 1.54 µm was obtained for a 160-mm2 junction-area diode. The series resistance for the diode with an electrode area of 24 µm2 was 47 Ω, estimated by fitting measured current-voltage curves. These results show that these layers are useful for reducing the series resistance of high-speed GaInAs photodiodes.
Threshold and Modulation Characteristics of Photon-Recycled Semiconductor Lasers
Authors: Tamanuki Takemasa , Fumio Koyama Fumio Koyama , Kenichi Iga Kenichi Iga
Published: February 2005

Threshold current characteristics of semiconductor lasers with photon recycling are theoretically investigated. By introducing rate equations modeling the reabsorption of spontaneous emission, the effect of photon recycling has been elucidated. The possibility of threshold reduction by a factor of more than three is suggested for a realizable closed cavity. In addition, modulation characteristics are also discussed.
Analysis of Atomic-Scale Structure of Microtwins in L-SPE Si by Modeling
Authors: Tomo Ueno Tomo Ueno , Iwao Ohdomari Iwao Ohdomari
Published: February 2005

Atomic-scale structure of a microtwin formed at the lateral solid phase epitaxial (L-SPE) region in a silicon-on-insulator (SOI) structure is analyzed using a plastic ball-and-spoke model. The microtwin is observed by means of high-resolution transmission electron microscopy (HR-TEM) to distribute not throughout the L-SPE film, but only in the region adjacent to the SiO2 substrate. Strain energy of each atom around the microtwin is calculated with Keating-type potential. The results show that strain energy of the atoms around the further edge of the planar twin boundaries (incoherent twin boundary) amounts to several hundred meV per atom. Higher strain energy must be introduced to reduce as much as possible the dangling bond density near the incoherent twin boundary, by forming a few pairs of 5- and 7-membered rings. In addition, a phase shift in the matrix region causes a wider distribution of strain energy.
Isothermal Vapor Phase Epitaxy of Hg1-x(Cd1-yZny)xTe Thin Films Using Semiclosed Open-Tube System
Authors: Isshiki Minoru , Maruyama Yutaka , Tobe Satoshi
Published: February 2005

Isothermal vapor phase epitaxy (ISOVPE) of Hg1-x
(Cd1-y
Zn
y
)
x
Te (MCZT) is performed at 723, 773 and 823 K using a HgTe source and Cd1-x
Zn
x
Te (CZT; x=0, 0.2 and 1) substrates. A weight loss of the source of more than 40% causes the melt of the substrate surface. Interdiffusions of Hg and Cd and/or Zn are clearly observed, and the layer thickness is proportional to the square root of the growth time. The surface morphology of the Hg1-x
Zn
x
Te (MZT) epitaxial layers is rough, and their thickness is not uniform, while the Hg1-x
Cd
x
Te (MCT) and MCZT grown using the CZT (x=0.2) substrates have good morphology and uniform thickness.
Defect Compensation by Bonded Hydrogen in Undoped a-Ge:H Films with Mono- and Dihydride Bonding
Authors: Nakashita Toshio , Hagiwara Shingo , Uehara Fumiya , Kohno Kenji
Published: February 2005

Hydrogenated amorphous Ge(a-Ge:H) thin films are prepared by the capacitive-coupled plasma chemical vapor deposition method using GeH4 as a reactive gas. Two kinds of films, one which involves only monohydride bonding and the other, which involves mainly dihydride bonding, are deposited in different deposition conditions. Although no impurity atoms, such as P or B atoms, are doped, both n- and p-type films are formed, depending on the deposition conditions. Infrared absorption spectra, electronic properties including photo- and dark conductivities, and optical properties of a-Ge:H have been studied. The effect of mono- and dihydride bonding on defect compensation is confirmed from the measurements, and it is concluded that the monohydride-bonding hydrogen atoms terminate the gap states mainly below midgap, and that the dihydride-bonding atoms chiefly decrease the number of gap states above midgap.
Growth of Single-Crystal Aluminum Films on Silicon Substrates by DC Magnetron Sputtering*
Authors: Nakajima Yasushi , Kusuyama Koichi , Hidenobu Yamaguchi Hidenobu Yamaguchi , Yoshinori Murakami Yoshinori Murakami
Published: February 2005

Single-crystal Al(110) films were deposited on Si(100) substrates 4 degrees off toward [01̄1̄] and single crystal Al(111) films were deposited on Si(111) substrates 3 degrees off toward the nearest [110] by DC magnetron sputtering deposition. In the formation of single-crystal aluminum films, both the buffered HF solution cleaning procedure for removing the SiO2 layers on the silicon substrates and the offset angle of the silicon wafers are indispensable. Without buffered HF solution cleaning, polycrystal Al(111) films were deposited. Without the offset angle, a bicrystal Al(110) preferred-orientation structure was deposited. Optical reflectance, scanning electron microscopy and X-ray diffraction were used to evaluate the film properties.
Electrical Properties of High-Temperature Annealed Boron-Implanted Hg0.7Cd0.3Te
Authors: Lam Kai-Yuen , Gong Jeng , Wu Tai-Bor , Jen-Chung Lou Jen-Chung Lou
Published: February 2005

The annealing effect of boron ion implantation in p-type Hg0.7Cd0.3Te/CdTe epilayers has been investigated. The implanted samples were annealed at temperatures ranging from 350°C to 500°C under saturated and nonsaturated Hg vapor pressure without encapsulation. The electrical activity of the n+-layer for samples annealed at high temperatures was found to be related to the activation of implanted boron ions. Generation-recombination noise measurement showed that the impurity energy level is about 5.6 meV.
Relationship between Crystal Structure and Chemical Composition of PbTiO3 Thin Films Prepared by Sputter-Assisted Plasma CVD
Authors: Mihara Toshiyuki , Mochizuki Schoichi , Saburo Kimura Saburo Kimura , Ryoji Makabe Ryoji Makabe
Published: February 2005

PbTiO3 thin films were prepared by sputter-assisted plasma chemical vapor deposition (CVD) on Pt-coated glass substrates at a substrate temperature of 500°C. As the source materials, a Pb metal target, TiCl4 gas and O2 gas were used. The crystal structures of the films changed from a pyrochlore phase to a perovskite one, and to a PbO (red) one with increasing Pb/Ti atomic ratio.
Magnetic Multipole Field Generated by Columns of Permanent Magnets Arranged on a Cylindrical Surface
Authors: Nihei Hitoshi , Hiroyuki Enomoto Hiroyuki Enomoto , Junji Morikawa Junji Morikawa
Published: February 2005

The magnetic multipole field generated by columns of permanent magnets arranged on a cylindrical surface at equal intervals is calculated. Each magnet is replaced by two sheet currents flowing in opposite directions through each side of the magnet. The results have been compared with measured values and found to be in good agreement with them. These expressions are simple and very convenient for the design of a plasma source surrounded by magnetic multipole fields.
Detection of Half-Wavelength Resonance of Surface Wave-Produced Plasma Column and Its Gas-Pressure Dependence
Authors: Shigehiko Nonaka Shigehiko Nonaka
Published: February 2005

Longitudinal half-wavelength resonances of a plasma column produced by a surface wave were observed at a region of a glass tube divided by the wave launcher. The gas pressure dependence of the resonance was also detected. This lowest resonance may be very useful for simple and non-perturbative determination of the plasma density produced by a surface wave.
Iodized Polymeric Yb-Diphthalocyanine Films Prepared by Plasma Polymerization Method
Authors: Naoya Kashiwazaki Naoya Kashiwazaki
Published: February 2005

An iodized polymeric Yb-diphthalocyanine film was prepared by a plasma polymerization method. Iodines were simultaneously incorporated into the polymeric Yb-diphthalocyanine (pp-YbPc2) film prepared by the plasma polymerization process. The iodized pp-YbPc2 film showed iodine-phenyl bonds and coordination of iodines to pp-YbPc2 ions. In addition, because of these strong interactions, iodines were not removed from the film under a heating condition with temperatures up to 120°C. The conductivity of the iodized pp-YbPc2 film at room temperature was about two orders of magnitude higher than that of an uniodized film. The iodized pp-YbPc2 film may be applicable as a heat-resistant polymeric semiconductor.
A Deep-Level Transient-Conductance Spectrometer for High-Resistivity Semiconductors Using a Marginal Oscillator Detector
Authors: Alexiev Dimitri , Tansley Kenneth Scott Alexander Butcher
Published: February 2005

A deep-level transient-conductance spectrometer for high-resistivity semiconductors, using a radiofrequency (∼40 MHz) marginal oscillator as a conductance detector, is described. Spectra are generated by periodically filling deep-level trapping centres with carriers stimulated by a pulsed GaAs laser, and processing the trap-emptying conductance signal through an exponential Miller correlator as the sample temperature is slowly ramped. Simple capacitive coupling of samples to the oscillator tank circuit eliminates problems such as unwanted defect annealing and other material changes often associated with the high-temperature techniques necessary for ohmic contact formation. Representative deep-level spectra are given for semi-insulating Bridgman-grown CdTe.
KrF Excimer Laser Process: Lateral and Surface Modification for Enhancing Resist Contrast
Authors: Minamiyama Takayuki , Kumagae Akitoshi , Sato Kazuo , Shin-ichi Ito Shin-ichi Ito , Makoto Nakase Makoto Nakase
Published: February 2005

A KrF excimer laser process, “lateral and surface modification for enhancing resist contrast” (LASER), combining alkali treatment before exposure and step development was investigated to improve the resolution capability of a novolac-diazoquinone-type positive tone photoresist. It has been found that a thin insoluble layer formed on both the resist surface and side wall maintains the resist thickness and the resist profile during development. As a result, a 0.35-µm line-and-space pattern with a steep profile can be obtained. The insoluble layer formation is due to the concentration of a photoactive compound, which is caused by the water rinse processes after the alkali treatment and the first step development.
Adhesion of Photoresist Micropattern to Aluminum Substrate in Alkaline Aqueous Solution
Authors: Kawai Akira , Takata Hitoshi Nagata
Published: February 2005

The purpose of this study is to analyze the fracture mechanism of adhesive bonding between a photoresist micropattern and an aluminum surface in an alkaline aqueous solution. Various surface treatments are performed on the aluminum surface prior to photoresist coating in order to control surface free energy and the thickness of the surface layer, which respectively relate to the two well-known fracture models: (i) debonding at the resist-aluminum interface and (ii) cohesive failure in the surface layer. Surface free energy is determined by means of the contact angle method. The thicknesses of the grease and oxide layers on the aluminum surface are obtained by means of ellipsometry. The results do not provide further evidence of a correlation between practical adhesive strength and surface free energy. It is also found that adhesive strength decreases with increases in surface oxide thickness. The interpretation of this is that bond failure does not take place at the interface between the aluminum and photoresist, but occurs in the oxide layer, which acts as a weak boundary layer, on the aluminum surface.
A Precision Alignment with Moire Technique and Differential Amplifier
Authors: Chang Tze-chung , Wu Cheng-wen , Chou Chien
Published: February 2005

A precision alignment technique is developed. We combined a moire and a differential amplifier to align two Ronchi rulings with high accuracy. The precision of this technique can reach submicron level if higher spatial frequency of the ruling is used.
Electron Wave Reflection by Multiquantum Barrier
Authors: Takagi Takeshi , Fumio Koyama Fumio Koyama , Kenichi Iga Kenichi Iga
Published: February 2005

For the purpose of experimentally and quantitatively demonstrating the enhancement of electron wave reflection by a multiquantum barrier (MQB) consisting of multiple combinations of quarter-de Broglie-wavelength heterostacks, we have fabricated two types of n-GaAs/i-barrier/n-GaAs tunneling diodes with a bulk Al
x
Ga1-x
As barrier and an Al
x
Ga1-x
As/GaAs MQB. From the current-voltage characteristic at 77 K it has been clarified that electrons are well reflected by the MQB. The potential barrier height was virtually increased by the MQB, and is estimated to be about 80 meV, which is in good agreement with theoretical expectation.
Fabrication of Tungsten-Carbon Multilayers for Soft X-Ray Optics Using Excimer-Laser-Induced Chemical Vapor Deposition Technique
Authors: Yamada Yuka , Mutoh Katsuhiko , Takashi Iwabuchi Takashi Iwabuchi , Takeo Miyata Takeo Miyata
Published: February 2005

The authors describe a new excimer-laser-induced chemical vapor deposition (LCVD) technique using laser-beam-scanning and ultrahigh-vacuum chamber systems. Film thickness distribution is controlled by scanning the laser beam on the substrate. Film thicknesses in LCVD with film depositions on the laser-beam transmitting window are also controlled by changing the deposition time. Tungsten-carbon multilayers of uniform thickness are successfully deposited on 2-inch-diameter substrates without being restricted by the beam size. A soft X-ray reflectivity of 25% is obtained at a grazing angle of 6°, and reflection peaks up to the third order are clearly observed for the first time in LCVD.
In-Situ X-Ray Photoelectron Spectroscopy of Reactive-Ion-Etched Surfaces of Indium-Tin Oxide Film Employing Alcohol Gas
Authors: Sakaue Hiroyuki , Makoto Koto Makoto Koto , Yasuhiro Horiike Yasuhiro Horiike
Published: February 2005

Reactive ion etching (RIE) of the In-Sn oxide (ITO) film has been studied employing methyl alcohol (CH3OH). The ITO etch rate depends strongly on ion energy, and the etching results show a directional feature for a wide region of pressure. The activation energy is a relatively high value of 4.0 kcal/mol. Therefore, ITO etching with CH3OH is likely to follow the ion-induced chemical reaction. The reaction kinetics which were also studied using in-situ X-ray photoelectron spectroscopy (XPS) and mass analysis implied that at first the ITO bonds were broken or weakened by hydrocarbon and hydrogen ions, thereby being reduced to metallic Sn and In. These metals are changed to volatile alkyls or alkoxys as a consequence of the reaction with hydrocarbon species. In fact, M/e=104 of the double-charge ion of In(OCH3)3 with M/e=208 is detected by a mass analyzer in the range of M/e=1-200. The advantage of using CH3OH is the suppression of the photoresist etch rate. The photoresist exposed by CH3OH plasma was ashed easily by oxygen radicals.
Mechanism for AlSiCu Alloy Corrosion
Authors: Ishida Tomoaki , Fujiwara Nobuo , Yoneda Masahiro , Horie Kazuo Nakamoto
Published: February 2005

We investigated corrosion at AlSiCu/TiN interconnection lines in VLSI devices. This type of corrosion appeared during the deionized water rinse treatment after the dry etching and ashing treatment (with O2+CF4 gas mixture). The corrosion shape was “pitlike”. When added the vacuum heating treatment before the deionized water rinse, the corrosion number was decreased. However, the ashing treatment had a contrary effect for this type of corrosion suppression. We investigated this type of corrosion mechanism by ion-chromatography analysis. In this analysis, residual Cl concentration decreased when the ashing time was prolonged, but the corrosion number was increased significantly. We measured residual F concentration at the same time, and detected a high concentration of F- ions. We consider that these F- ions contribute to this type of corrosion.
Identification of Vacancy-Type Defects in Molecular Beam Epitaxy-Grown GaAs Using a Slow Positron Beam
Authors: Wei Long , Tanigawa Shoichiro , Uematsu Masashi , Maezawa Koichi
Published: February 2005

Vacancy-type defects in the GaAs film grown to a thickness of 3000 Å on a GaAs substrate by molecular beam epitaxy (MBE) were studied using a slow positron beam. The Doppler-broadened shape parameters showed a significant difference between the as-grown GaAs film at 450°C and that at 650°C. It is suggested that the higher growth temperature promotes the creation of Ga vacancies in MBE-grown GaAs film. It is also shown that the oxide capped on the surface of GaAs enhances the formation of Ga vacancies during annealing (950°C, 4 s). The Si ion-implanted GaAs could not be recovered completely with subsequent annealing (950°C, 4 s).
Conduction Mechanism of Leakage Current Observed in Metal-Oxide-Semiconductor Transistors and Poly-Si Thin-Film Transistors
Authors: Yazakis Masatoshi , Takenaka Satoshi , Ohshima Hiroyuki
Published: February 2005

It has been confirmed that the leakage current observed in Metal-Oxide-Semiconductor (MOS) transistors and polycrystalline thin-film transistors (poly-Si TFTs) corresponds to activation energies of the current. Two new models of the conduction of leakage current have been proposed on the basis of this correspondence. These models consist of two types of steps: the first step is the thermal emission of an electron occurring in the neighborhood of the drain electrode, and the second step is the tunneling of an electron through a trap state in the band gap. These models have enabled us to explain the conduction mechanism of the leakage current in various devices.
A Model of Heterojunction Bipolar Transistors at T=0
Authors: Kuniichi Ohta Kuniichi Ohta
Published: February 2005

A model of HBT (heterojunction bipolar transistor) at absolute zero temperature T=0 is developed as a limit of the scaling principle proposed previously by the present author. On the basis of the inhomogeneous degenerate non-equilibrium free-electron gas model, analytical solutions for a symmetric transistor are obtained in some detail in both active and saturation regions. It is found that collector current is a steeply rising function of base emitter bias voltage. Then, the possibility of very small logic swing circuits is briefly discussed.
As-Grown BiPbSrCaCuO Superconducting Films on MgO(100) by DC-Sputtering
Authors: Chin Tsung S. , Huang Jee Y. , Perng Li H. , Huang Tung W. , Yang Sheng J. , Hsu Shu E.
Published: February 2005

As-grown BiPbSrCaCuO superconducting films with T
c-zero of up to 79 K have been prepared on MgO(100) substrates by dc-sputtering a single Bi1.8Pb0.3Sr2Ca2Cu3O
x
(2223 phase) target. Film composition depends mainly on deposition time and the substrate temperature. The 700°C×2 h-deposited films have optimum composition, and phases hence show T
c-zero of higher than 77 K. The cooling rate after deposition is found to be crucial for obtaining higher T
c. The optimum rate is 75°C/min or faster.
Photoconductive Gain in a Schottky Barrier Photodiode
Authors: Schubert F. Soares Schubert F. Soares
Published: February 2005

Quantum efficiency in excess of 100% was measured for a Ni-Si-Ni Schottky-barrier photodiode. In addition, the RF impedance of the photodiode displayed strong reciprocal dependance on the optical power illuminating the photodiode, and proportional dependance on the applied bias. It is proposed here that the mechanism by which this anomalous gain occurs is the modification of the Schottky barrier by optically-generated charge; specifically, residual holes that are slower in transit than electrons. The electric field between these holes, and the corresponding image charge in the metal contact, is sufficiently strong to alter the barrier. The result of a theoretical calculation indicates that the resistance of the Schottky barrier, and consequently the photodiode, varies inversely as the square-root of the electric field. The equivalent circuit of a semiconductor photodetector is generalized to include this effect.
Ferromagnetic Resonance in Epitaxial Fe Films on MgO
Authors: Jr. Osamu Kohmoto
Published: February 2005

Ferromagnetic resonance measurements were carried out to study the magnetic anisotropy and the crystallographical orientation in epitaxial (001) Fe films grown on (001) MgO. The magnetocrystalline anisotropy field (2K
1/M) and the saturation magnetization (4πM) were measured by the angular dependence of the resonance field; the static field was applied in the film plane and the vertical plane. The obtained 2K
1/M and 4πM values are close to those of bulk Fe. Therefore, these results suggested that the specimen was a single crystal; the orientation was [100] Fe//[110] MgO.
Evaluation of High-Efficiency LiNbO3 Optical Phase Modulator Using Electrodes Buried in the Buffer Layer
Authors: Miyamoto Hiroshi , Ohta Hiroshi , Kazuhiko Tabuse Kazuhiko Tabuse , Yoshihide Miyagawa Yoshihide Miyagawa
Published: February 2005

A new optical phase modulator with electrodes buried in the buffer layer in order to match the microwave electric field with optical electric field has been designed and fabricated. As a result of evaluation, this structure was effective for widening bandwidth and reducing driving voltage, the 3 dB down bandwidth and V
π of the interaction length of 13 mm at the optical wavelength of 1.5 µm were 20 GHz and 12 V, respectively.
Detection of Electron Transfer in Multilayer Systems by a Displacement Current-Measuring Technique
Authors: Atsuzawa Makoto , Majima Yutaka , Iwamoto Mitsumasa , Kakimoto Masaaki , Imai Yoshio
Published: February 2005

A displacement current-measuring technique was used for the detection of transportation of photoexcited electrons at the interface between electrodes and monolayers prepared on the electrodes. Displacement current was found to be generated by the motion of electrons at the interface. The current-measuring technique was also used for the detection of transportation of photoexcited electrons between two adjacent single monolayers. Displacement current was found to be generated in the direction predicted by the motion of electrons.
Electrostatic Force and Absorption Current of Alumina Electrostatic Chuck
Authors: Watanabe Toshiya , Tetsuo Kitabayashi Tetsuo Kitabayashi , Chiaki Nakayama Chiaki Nakayama
Published: February 2005

Electrostatic chucks composed of alumina ceramics doped with 1.3 wt% TiO2 and 3.5 wt% Cr2O3 were fabricated. Evaluations of electrostatic force and absorption charge in various atmospheres were carried out. The electrostatic force in various atmospheres clarified that the electrostatic force is affected not only by the bulk resistance, but also by the surface resistance of the ceramics. Absorption charge measurements revealed that the surface resistance affects the charge distribution of the dielectric layer, and it is deduced that the large electrostatic force of the alumina electrostatic chuck in the vacuum atmosphere is explained by the space charge which concentrates on the dielectric layer and intensity contact potential difference.
Surface-Induced Parallel Alignment of Liquid Crystals by Linearly Polymerized Photopolymers
Authors: Schadt Martin , Schmitt Klaus , Kozinkov Vladimir , Chigrinov Vladimir
Published: February 2005

Photopolymerization of polymer-coated solid substrates with linearly polarized light is shown to induce an anisotropic, uniaxial orientation of polymer molecules. The linearly photopolymerized (LPP) layers exhibit UV dichroism and optical anisotropy. The resulting anisotropic dispersive surface interaction forces are shown to align adjacent liquid crystals parallel. A qualitative microscopic model is presented. The new LPP-alignment technique allows to generate homogeneous LC-director pattern with different azimuthal director angles on the same substrate requiring no mechanical treatment. The use of LPP substrates in liquid crystal displays (LCDs) is shown to enable to combine different electrooptical effects-such as twisted nematic (TN) and parallel configurations-in the same hybrid LCD. Besides from high-contrast LPP-aligned TN-LCDs, LPP-aligned supertwisted nematic (STN)-LCDs exhibiting steep transmission-voltage characteristics are presented.
Effective Techniques for Ultra-High Purity Liquid Phase Epitaxial Growth of Ga0.47In0.53As
Authors: Amano Toshimasa , Nagai Susumu Kondo
Published: February 2005

Ultra-high purities are obtained using a two-step method involving baking the In solvent in wet hydrogen prior to the source addition and subsequent solution recycling for several growth stages with baking in dry hydrogen. We obtain the highest purity so far with a carrier concentration as low as 5.8×1013 cm-3, and an electron mobility as high as 132000 cm2/Vs at 77 K for a GaInAs lattice matched to an InP substrate using three subsequent recyclings of the source solution after baking the In in wet hydrogen. The purity obtainable with this technique seems to be restricted by the indium purity, and more seriously by both impurity out-diffusions into solution from the substrate, and from the boat, which absorbs impurities at the preceding growth stage.
Characterization of Grown-in Dislocations in Benzophenone Single Crystals by X-Ray Topography
Authors: Tachibana Masaru , Motomura Shigeki , Uedono Akira , Tang Qi , Kenichi Kojima Kenichi Kojima
Published: February 2005

Benzophenone single crystals were grown by the Czochralski method. The dislocations introduced during the crystal growth were examined using X-ray topography. Double images of single dislocations were found on the topographs taken in some reflection planes. The Burgers vector of predominant grown-in dislocations was estimated from analysis of the dislocation images on the basis of kinematical theory.
Effect of Preparation Conditions on the Properties of CdSe Microcrystal-Doped SiO2 Glass Thin Films Prepared by RF-Sputtering
Authors: Kaneko Shoji , Nasu Hiroyuki , Ikegami Tomohiro , Jun Matsuoka Jun Matsuoka , Kanichi Kamiya Kanichi Kamiya
Published: February 2005

CdSe microcrystal-doped SiO2 glass thin films were prepared by an RF-sputtering technique under various conditions. The mean size and the size distribution of microcrystals in the films were found to be controlled by the sputtering conditions. A marked narrowing of size distribution of CdSe microcrystals was achieved in the films, compared to the melt-derived CdSe microcrystal-doped glasses. The relationship of the blue shift of the absorption edge to the reciprocal square of the mean particle size deviated from those theoretically deduced from the exciton confinement and the electron-hole confinement, and this can be deduced from the significant contribution of the Coulomb force between electrons
and holes.
Scanning Tunneling Microscopy of the ReO3 Surface
Authors: Ikebe Shin-ichiro , Suzuki Katsumi , Nishikawa Hisao , Daisuke Shimada Daisuke Shimada , Nobuo TSuda Nobuo TSuda
Published: February 2005

The surface of a ReO3 single crystal was studied using the scanning tunneling microscope (STM) with a tungsten tip. Atomic images were taken and they revealed that the surface consists of {100} planes, and that there are many drains whose depth and width are integer multiples of the unit cell length. There are biperiodic structures on the surface coexisting with a single-period structure. The biperiodic structure may originate in the biperiodic arrangements of the top oxygen ions.
Epitaxial Growth of TiO2-SnO2 Solid Solution Film by Reactive Ion Beam Sputtering
Authors: Okamura Takeshi , Yoji Seki Yoji Seki , Nobukazu Sagawa Nobukazu Sagawa
Published: February 2005

Epitaxial thin film of rutile-type TiO2-SnO2 solid solution has been successfully prepared. The film was fabricated on a sapphire (011̄2) substrate by the reactive ion beam sputtering method using a TiO2-SnO2 ceramic target. The crystallinity of the film was dependent on the substrate temperature. The (101)-oriented film was grown at temperatures higher than 300°C. An epitaxial film was obtained by heat-treatment at temperatures higher than the miscibility gap.
Characterization of Diamond Films by Means of a Pulsed Positron Beam
Authors: Suzuki Ryoichi , Kobayashi Yoshinori , Mikado Tomohisa , Ohgaki Hideaki , Chiwaki Mitsukuni , Yamazaki Tetsuo , Uedono Akira , Tanigawa Shoichiro , Funamoto Hiroyuki
Published: February 2005

Positron lifetime spectra of thin diamond films synthesized by microwave plasma-enhanced chemical vapor deposition have been measured with a variable-energy pulsed positron beam in order to characterize defects in the diamond films. A positron lifetime experiment on bulk diamond synthesized at high pressures has also been carried out. It has been found that there exists a high concentration of vacancy-type defects in the films and the defect properties are strongly influenced by the deposition condition. Positronium formation in voids has been observed in all of the films but not in the bulk diamond. The void sizes have been estimated from the lifetime values of ortho-positronium components. The present study demonstrates that pulsed positrons can be used nondestructively and sensitively to characterize defects in thin diamond films.
Optical and Magnetic Properties of Electrochemically Doped p- and n-Type Poly(3-hexylthiophene)
Authors: Onoda Mitsuyoshi , Manda Yasuhisa , Morita Shigenori , Yoshino Katsumi
Published: February 2005

The electrochemical, optical and magnetic properties of poly(3-hexylthiophene) (PAT-6) in comparison with those of polythiophene (PT) during electrochemical p- and n-type doping have been investigated by cyclic voltammetry, optical absorption spectroscopy and electron spin resonance measurements. The results are discussed in terms of polaron and/or bipolaron models and lead to a better understanding of the electronic levels. Specifically, as the top of the valence band of PAT-6 is located at a higher energy state than that of PT by about 0.3 eV, the p-type dopant in PAT-6 is relatively stable compared with that in PT. However, because the bottom of the conduction band of PAT-6 was evaluated to be located at a higher energy state by about 0.3 eV than that of PT, the n-type doping in PAT-6 is more difficult than in PT.
Photon-Induced Hopping in Bi2Sr2Ca0.5Y0.5Cu2Oy
Authors: Masayuki Sato Masayuki Sato , Keigo Nagasaka Keigo Nagasaka
Published: February 2005

Transmission measurements of freestanding Bi2Sr2Ca0.5Y0.5Cu2O
y
crystals have been made in the frequency range from 10 to 12000 cm-1. Photon-induced hopping from occupied to unoccupied O-2p states was found in the absorption spectra from 10 to 5200 cm-1. The absorption edge at 11500 cm-1 due to charge transfer excitation and so-called mid-IR absorption from 1000 to 10000 cm-1 were also observed. Mid-IR absorption has been ascribed to a photon-induced hopping conduction edge continuing from the far-IR region.
Characteristics of an Chemically Amplified Silicone-Based Negative Resist (CSNR) in Electron Beam Lithography
Authors: Tanaka Akinobu , Ban Hiroshi , Jiro Nakamura Jiro Nakamura , Yoshio Kawai Yoshio Kawai
Published: February 2005

The characteristics of CSNR, which is composed of an alkali-soluble silicone polymer (ASSP) and an acid generator, have been studied. ASSP is obtained by a sol-gel reaction of a mixture of phenyltrimethoxysilane and 2-(3,4-epoxycyclohexyl)ethyl trimethoxysilane and has a lot of silanol groups that make ASSP alkali-soluble. The resist chemistry of CSNR is based on the acid-catalyzed condensation of the silanol groups during post exposure baking. The resist characteristics of CSNR also depends on the acid generator. Using triphenylsulfonium triflate as a acid generator, a 0.2-µm lines-and-spaces pattern can be fabricated upon electron beam exposure at a dosage of 1.2 µC/cm2.
Nanometric Scale Biosample Observation Using a Photon Scanning Tunneling Microscope
Authors: Jiang Shudong , Ohsawa Hisao , Yamada Kazunobu , Pangaribuan Togar , Ohtsu Motoichi , Imai Kensaku , Ikai Atsushi
Published: February 2005

A T4 bacteriophage with a tail diameter of about 9 nm was observed for the first time in an atmospheric condition without a metal film coating, by means of a superresolution photon scanning tunneling microscope (PSTM) using a fiber probe. Fiber probes with cone angles of 25°-100° and their minimum curvature radii less than 10 nm were fabricated andthe angle variance was less than 0.5°. The normal resolution of such a PSTM was evaluated to be less than 1 nm, and the lateral resolution, limited by the curvature radius of the fiber probe, was estimated to be within 20 nm.
X-Ray Diffraction Study on Ultrafine Particles of Ag-Cu Alloys Prepared by “Hydrogen Plasma-Metal” Reaction Method
Authors: Nakahigashi Kiyotaka , Ishibashi Hiroki , Shinnosuke Minamigawa Shinnosuke Minamigawa , Mineo Kogachi Mineo Kogachi
Published: February 2005

A series of ultrafine particles (UFP) in Ag
x
Cu100-x
alloys was prepared by the “hydrogen plasma-metal” reaction method with changing composition x}b of bulk parent alloys. The changes in diffraction profiles and lattice constants on x
b were investigated by X-ray diffraction and least-squares pattern fitting methods. On the Cu-rich side (x
b<50), the UFP was composed of three metastable phases: Cu-rich 1 phase (x=6.1∼5.3), Cu-rich 2 phase (x∼12.2) and Ag-rich phase (x=94.8∼91.0). In these, the solubility of Ag in the Cu-rich 2 phase was about 2.5 times as large as the maximum value (x=4.9) at the eutectic temperature of the equilibrium phase diagram. On the Ag-rich side together with x
b=50, the UFP was composed of Cu-rich 1 phase (x∼5.3) and Ag-rich phase (x∼91.7) except for x
b=90. The total concentration of Ag in the UFP noticeably deviated positively from x
b.
Ignition Probability in a Fuel Spray
Authors: Liao Chihong , Utaka Kunio Terao
Published: February 2005

Application of the stochastic ignition theory to spontaneous ignition in an n-octane fuel spray injected into high-temperature air behind reflected shock waves in a shock tube is statistically investigated. The total space into which the fuel is injected is optically divided into 25 sections and the induction period of ignition in each section is separately, but at the same time, measured, using several photomultipliers. From the histogram of the ignition induction period in each section obtained by repeating the same experiment many times, the temporary and spatial distributions of ignition probability in the fuel spray are obtained.
AC Photovoltaic Images of Thermally Oxidized P-Type Silicon Wafers Contaminated with Metals
Authors: Munakata Hirofumi Shimizu
Published: February 2005

Upon oxidation, traces of some metal impurities intentionally introduced are identified qualitatively in p-type silicon (Si) wafers as dark photovoltaic images, using a scanning photon microscope (SPM) based on ac surface photovoltages (SPVs). Metal impurities in the Si bulk act as recombination centers for excess carriers, eventually reducing SPVs at the contaminated region. The SPM was successfully applied to eliminate such deteriorated wafers nondestructively in semiconductor device processing.
High-Efficiency and Highly Reliable 20 W GaAs Power Field-Effect Transistor in C Band
Authors: Sonoda Takuji , Sakamoto Shinichi , Kasai Nobuyuki , Yamanouchi Masahide , Saburo Takamiya Saburo Takamiya , Yuzou Kashimoto Yuzou Kashimoto
Published: February 2005

This paper describes a high-performance and highly reliable GaAs field-effect transistor (FET) with a new gate structure employing the stepped gate recess combined with a multirefractory metal gate. This gate structure allows the simultaneous increase of maximum channel current and gate-drain breakdown voltage (V
gdo) of the FET and thus improves significantly its output power (P
o) and power-added efficiency (ηadd). The resultant high V
gdo with highly stable gate Schottky characteristics and a novel surface stabilization prior to plasma-SiN passivation effectively suppress both catastrophic and gradual failures. The four-chip internally matched device (4×12.6 mm) has delivered P
o of 20 W at 1 dB gain compression with 39% ηadd over 3.5 to 4.2 GHz. Sufficient reliability of the 20 W device available for satellite use has been assured by comprehensive reliability tests.
AlxGa1-xAs Heterojunction Phototransistors Responding to Entire Visible Wavelength Region
Authors: Zhu Yu , Noda Susumu , Yoshikazu Takeda Yoshikazu Takeda , Akio Sasaki Akio Sasaki
Published: February 2005

An Al
x
Ga1-x
As heterojunction phototransistor, in which an incident light directly reaches the base through an opening at the center of the emitter layer, is proposed and fabricated. The phototransistor exhibits photosensitivity over a wide spectral region from 380 to 870 nm. The optical conversion gains, G=520 at 515 nm wavelength and G=950 at 730 nm, are obtained. The opening at the emitter layer influences the characteristics of the devices and this is discussed in terms of the surface recombination and emitter current crowding. The device can serve as a photodetector with optical conversion gain over a wide wavelength region.
Optimum Design of Thin-Film-Based Tandem-Type Solar Cells
Authors: Hideyuki Takakura Hideyuki Takakura
Published: February 2005

The conversion efficiency of a thin-film-based tandem solar cell is theoretically calculated and the best material combinations are discussed. As constituent materials, not only crystalline but also amorphous materials are considered. Attention is given especially to the electrical performances of both the top and bottom cells, which have strong effects on the optimum conditions and attainable conversion efficiency. It is found that a conversion efficiency of above 30% can be expected when utilizing an amorphous Si-based cell as the top cell with a single crystalline Si bottom cell, and above 20% with CuInSe2 or CdTe as a bottom cell. In order to obtain a conversion efficiency of above 40%, insolation concentration with effective cell cooling is essentially required in tandem solar cells of both single crystalline materials.
Characterization of a New Cu-Al-Se Phase Grown by Molecular Beam Epitaxy
Authors: Yoshio Morita Yoshio Morita , Tadashi Narusawa Tadashi Narusawa
Published: February 2005

We have confirmed the existence of a new Cu-Al-Se phase grown by molecular beam epitaxy. The phase possesses a crystal structure equivalent to the tetragonal structure compound Cu5FeS4 found in the Cu-Fe-S system, and has a direct band gap of around 3.1 eV at room temperature. The new Cu-Al-Se phase clearly differs from the chalcopyrite structure compound CuAlSe2, and is considered to be a Cu5AlSe4 compound.
Crystallization of Superconducting Phases in Melt-Quenched and Annealed Bi1.6Pb0.4Sr2Can-1CunOy (n=1 to 4) Ceramics
Authors: Harada Ryo , Osamu Yoshinari Osamu Yoshinari , Kazuhide Tanaka Kazuhide Tanaka
Published: February 2005

The crystallization processes of the superconducting phases in melt-quenched BSCCO ceramics which exhibit glass structures after melt quenching have been investigated by means of X-ray diffractometry, electrical resistivity measurements, thermogravitational and differential thermal analyses (TG-DTA) and scanning electron microscopy (SEM). The crystallization occurs in the sequence glass phase⇒semiconducting (2201) phase⇒low-T
c (2212) phase⇒high-T
c (2223) phase. The excess addition of Ca and Cu constituents to the BSCCO ceramics facilitates the growth of the low-T
c and high-T
c phases.
Temperature-Modulated Semiconductor Laser for Widely Tunable and Power-Controlled Operation
Authors: Shudong Jiang Shudong Jiang , Takao Kobayashi Takao Kobayashi
Published: February 2005

We describe a widely tunable, power-controlled oscillation method of AlGaAs semiconductor lasers in the visible region, based on temperature modulation by a microheater placed on the laser chip. The continuous frequency tuning range for a single-axial-mode operation is extended to 0.28 nm (132 GHz) at 779 nm by the heater current modulation. Cutoff frequency of the temperature modulation response is 50 Hz. The injection current is used mainly for the power control of the FM oscillation. By using a short external mirror for axial mode selection, the continuous tuning range is further increased to 0.49 nm (237 GHz), which corresponds to almost five times the value with the injection current modulation.
Learning Generalization by Validation Set
Authors: Hasegawa Akira , Matoba Osamu , Kazuyoshi Itoh Kazuyoshi Itoh , Yoshiki Ichioka Yoshiki Ichioka
Published: February 2005

Training a neural network to respond reasonably to input data not present in the training set is believed to be difficult. This is known as the generalization problem. We propose a learning method for solving this problem. The proposed method adjusts the number of hidden units in the network according to the difference between the errors for the validation and the training sets. The difference reflects the degree of generalization during the learning process. The correction of weights is based on the error back propagation. Numerical simulations of curve fitting demonstrate the effectiveness of our algorithm.
Evolution of Transport Properties along a Semi-Insulating CdTe Crystal Grown by Vertical Gradient Freeze Method
Authors: Tanaka Kazuhiko Suzuki
Published: February 2005

The evolution of transport properties along a chlorine-doped CdTe crystal grown by the gradient freeze (GF) method has been investigated by time of flight (TOF) measurement. Drift mobilities as high as 1100 cm2/(Vs) and 80 cm2/(Vs) for electrons and holes, respectively, are measured at the initial part of the grown crystal, and were found to decrease with increasing solidified fraction (g). On the other hand, the specific resistivity increases with increasing g. These behaviors can be understood as the dopant (Cl) concentration variation due to segregation during growth. The change in γ-detection properties between crystals having different g is demonstrated.
Carbon in III-V Compounds: A Theoretical Approach
Authors: Markus Weyers Markus Weyers , Kenji Shiraishi Kenji Shiraishi
Published: February 2005

Carbon as a very well behaved acceptor dopant in GaAs/AlGaAs is already successfully used in many device applications. However, the physics governing its incorporation behavior (amphoteric impurity) into III-V semiconductors is currently not well understood. We present a calculation from first principles of the change in total energy accompanying the incorporation of carbon onto lattice sites in the III-V compounds AlP, GaP, InP; and AlAs, GaAs and InAs. Taking into account the energy gained by filling a group III or group V vacancy with carbon, the obtained p-type conduction in carbon doped GaAs, AlAs, GaP (and presumably AlP) as well as the n-type conduction in InP can be explained based on the results of our total energy calculations. Additionally, the observed trends in the energy gain can explain the observed differences in tendency for carbon incorporation into the compounds under study.
The Effect of Atmosphere and Doping on Electrical Conductivity of CuO
Authors: Suda Seiichi , Fujitsu Satoru , Koumoto Kunihito , Yanagida Hiroaki
Published: February 2005

The electrical conductivity and Seebeck coefficient have been measured for pure and Li- or Al-doped CuO. The sign of the Seebeck coefficient of all samples shows p-type semiconducting properties in all temperature and oxygen partial pressure ranges employed in this measurement. The temperature dependence of electrical conductivity shows two regions. The conductivity in the high-temperature region is independent of the doping and the atmosphere, whereas that in the low-temperature region depends strongly on such factors.