bluuebunny/crossref_metadata_2025 huggingface dataset:
Laser-Assisted Probing Method for Measuring Negative Ions in Plasmas
Authors: Hiroshi Amemiya Hiroshi Amemiya , Takanori Suzuki Takanori Suzuki
Published: February 2005

A laser beam is focussed on a position in a plasma and electrons photodetached from negative ions are detected by a probe. The probe potential for obtaining an optimum signal intensity is slightly below the voltage that causes the sheath breakdown. The signal-to-noise ratio is increased more than in the case where the signal is detected either from the anode or the cathode. Spatial resolution is obtainable to the order of the laser beam diameter.
Dependence of Gate Oxide Breakdown Frequency on Ion Current Density Distributions during Electron Cyclotron Resonance Plasma Etching
Authors: Seiji Samukawa Seiji Samukawa
Published: February 2005

According to the reduction of gate oxide thickness in Metal-Oxide-Semiconductor (MOS) devices, the gate oxide degradation caused by the stored charge during magnetized high-density plasma etching becomes a serious problem. The gate oxide degradation and the breakdown are brought about due to the nonuniform plasma radiation by the uneven magnetic field profile. Therefore, the flat equi-magnetic field profile suppresses the gate oxide degradation during electron cyclotron resonance (ECR) plasma etching.
Optical Characterization of Very Thin Hydrogenated Amorphous Silicon Films Using Spectroscopic Ellipsometry
Authors: Saitoh Tadashi , Hori Nobuyasu , Katsuyuki Suzuki Katsuyuki Suzuki , Shigeo Iida Shigeo Iida
Published: February 2005

Optical properties of very thin amorphous silicon films have been characterized by means of spectroscopic ellipsometry. Second derivatives of imaginary dielectric functions with respect to energy are compared. Etching-off the surface oxide is effective in determining the correct film thickness and dielectric functions. Complex refractive indices are obtained for films thinner than 50 nm. Calculated optical energy gap is found to increase for thinner films. The tendency is ascribed to the existence of a thin interface layer consisting of amorphous silicon and void.
Poly-Si Thin Film Transistors Fabricated with Rapid Thermal Annealed Silicon Films
Authors: Bonnel Madeleine , Duhamel Nicole , Guendouz Mohamed , Haji Lazhar , Bertrand Loisel Bertrand Loisel , Patrick Ruault Patrick Ruault
Published: February 2005

This letter describes a new process for realization of polysilicon thin-film transitors (TFT) on glass substrates. The process is based on crystallization by rapid thermal annealing of amorphous silicon films deposited by low-pressure chemical vapor deposition (LPCVD). With this technique, the time of crystallization of the silicon films is reduced to a few seconds. Thin-film transistors have been realized using this process, and the field-effect mobility is in the range of 20 cm2·V-1·s-1.
Electrical and Optical Properties of Ca1-xSrxCuO2 Films Prepared by Organometallic Chemical Vapor Deposition Method
Authors: Kobayashi Kenkichiro , Ishihara Yozo , Shigenori Matsushima Shigenori Matsushima , Genji Okada Genji Okada
Published: February 2005

The as-deposited Ca1-x
Sr
x
CuO2 film is a semi-insulator, and the resistivity of the film is reduced by a factor of about one hundred after postannealing in 1 atm O2. The temperature dependence of the resistivities of these films is semiconductive. The positive Seebeck coefficients of these films indicate that holes in the valence band are generated by excess oxygen. The charge-transfer absorption is observed at a wavelength shorter than 800 nm.
Threshold Current Density of GaAs/AlGaAs Single-Quantum-Well Lasers Grown by Molecular Beam Epitaxy
Authors: Miyazawa Sei-ichi , Yoshinobu Sekiguchi Yoshinobu Sekiguchi , Natsuhiko Mizutani Natsuhiko Mizutani
Published: February 2005

We report on the effect of substrate temperature on the threshold current density in GaAs/AlGaAs single-quantum-well lasers grown by molecular beam epitaxy under various flux ratios. It is found that the threshold current density has W-shape dependence on the substrate temperature and exhibits minima of 600 A/cm2 and 400 A/cm2 at the substrate temperatures of 375°C and 650°C, respectively.
Visible-Light Electroluminescent Diodes Utilizing Poly(3-alkylthiophene)
Authors: Ohmori Yutaka , Uchida Masao , Keiro Muro Keiro Muro , Katsumi Yoshino Katsumi Yoshino
Published: February 2005

A visible-light electroluminescent diode utilizing poly(3-alkylthiophene) has been demonstrated for the first time. The light emission intensity increases superlinearly with increasing injected current. Remarkable enhancement of electroluminescence intensity is obtained for a poly(3-alkylthiophene) diode with longer alkyl side chain length.
Photoconductive Decay Measurements on Semiconducting Black Phosphorus Crystals
Authors: Baba Mamoru , Nakamura Yoshitaka , Shibata Kiyotaka , Morita Akira , Yamada Hiroshi
Published: February 2005

Photoconductive decay measurements on black phosphorus crystals have been carried out in the temperature range 80-330 K. It was found that the measured lifetime is nearly constant below about 260 K, while it decreases with increasing temperature. From such temperature dependence, it was suggested that the indirect Shockley-Read recombination is dominant below 260 K, while the direct recombination such as the intrinsic Auger process is dominant above 260 K. It was also found that the measurement lifetime depends strongly on applied voltage. The fast response of the order of 10-6-10-7 s indicates that black phosphorus can be used as a photoconductive detector of high-frequency operation for infrared radiation below 4.4 µm.
Fabrication of Fe-Zr-N Films with Very Low Coercivity
Authors: Taneko Noriaki , Shimada Yutaka , Miyakawa Kazuaki Fukamichi
Published: February 2005

Fe-Zr-N films with very low coercivity have been fabricated by RF magnetron sputtering. The films consist of very fine α Fe and ZrN crystals. The crystal size of α Fe is estimated to be less than 50 Å, resulting in decrease of the coercivity down to 10 A/m. The magnetic softness and thermal stability are available only for a very narrow range of nitrogen content.
Photoacoustic Spectroscopy in Band Edge Region of Cd1-xMnxTe
Authors: Oka Mitsuharu Nogaku
Published: February 2005

Nonradiative recombination processes have been studied in Cd1-x
Mn
x
Te of x=0.4 and 0.6 by highly sensitive photoacoustic spectroscopy. The photoacoustic spectrum is found to be extended deeply into the energy-band-gap region by 150-300 meV and shows a remarkable decrease of the photoacoustic intensity at 2.07 eV. The results are interpreted in terms of the nonradiative recombination process which takes place in the fluctuating band-edge region of the material, and the suppression of the nonradiative process due to the energy transfer from the band electrons to the Mn ion levels. The relationship with the photoluminescence process is also discussed.
Application of Penta-Di-Methyl-Amino-Tantalum to a Tantalum Source in Chemical Vapor Deposition of Tantalum Oxide Films
Authors: Tabuchi Toshiya , Sawado Yoshinori , Kunimasa Uematsu Kunimasa Uematsu , Shohei Koshiba Shohei Koshiba
Published: February 2005

Penta-di-methyl-amino-tantalum (Ta[N(CH3)2]5), a new source chemical of Ta in TaO chemical vapor deposition (CVD), has been studied. TG and DTA measurements show that Ta[N(CH3)2]5 is chemically stable up to about 150°C and vaporizes at a temperature of 80°C. TaO films were deposited by LP-CVD at temperatures of 380∼520°C, by using the new chemical Ta[N(CH3)2]5 and O2. The deposition rate of TaO with Ta[N(CH3)2]5 is higher than that with Ta(OC2H5)5, a conventional Ta source. The TaO CVD using Ta[N(CH3)2]5 and O2 yields a good step coverage. Although the as-deposited TaO films are oxygen poor in film composition, annealing in an oxidizing ambient improves the stoichiometry and reduces the leakage current.
Resonant Tunneling in a Novel Coupled-Quantum-Well Base Transistor
Authors: Waho Takao , Koichi Maezawa Koichi Maezawa , Takashi Mizutani Takashi Mizutani
Published: February 2005

Resonant tunneling in a novel coupled-quantum-well (CQW) base transistor is investigated. The CQW-base structure is confirmed through secondary ion mass spectroscopy and transmission electron microscopy. Transconductance measurements reveal that the collector current is attributable to resonant tunneling transfer from the emitter to collector through the modified energy states in the CQW-base. Current gain β as large as 5.5 is observed for the first time with respect to the resonant tunneling current.
Novel Quadruple Zigzag Structure of Antiferroelectric Liquid Crystal Molecules Observed by Scanning Tunneling Microscopy
Authors: Hara Masahiko , Umemoto Takeshi , Takezoe Hideo , Anthony F. Garito Anthony F. Garito , Hiroyuki Sasabe Hiroyuki Sasabe
Published: February 2005

We report the first map of the interfacial structure of the antiferroelectric liquid crystalline phase, directly observed with molecular resolution by scanning tunneling microscopy (STM). STM images reveal that the antiferroelectric layers consist of novel quadruple “zigzag” molecular rows with one-dimensional modulated electron density distribution, instead of the simple binary model proposed earlier.
Oxygen Doping Effects on Thermal Properties of ZrF4-BaF2 Glasses Synthesized by Plasma-Enhanced Chemical Vapor Deposition
Authors: Fujiura Kazuo , Nishida Yoshiki , Kenji Kobayashi Kenji Kobayashi , Shiro Takahashi Shiro Takahashi
Published: February 2005

Oxygen-doped ZrF4-based fluoride glass film is synthesized by plasma-enhanced chemical vapor deposition (PCVD) and the effects of oxygen doping on thermal properties are investigated. The oxygen-doped fluoride glass film has a slightly higher glass-transition temperature and a wider T
x-T
g gap than fluoride glass prepared by the melt-casting method without oxygen doping. The glass forming region in the ZrF4-BaF2 system is significantly improved by oxygen doping. Oxygen ions, which are distributed homogeneously in the fluoride glass film by PCVD, strengthen the structural network of the fluoride glass, which improves its stability against crystallization.
Fine Patterns of Positive-Working Resists Using a Polyimide Langmuir-Blodgett Film System
Authors: Iwamoto Mitsumasa , Kasahara Shigeo , Iriyama Keiji , Nishikata Yasunari , Kakimoto Masaaki , Imai Yoshio
Published: February 2005

Thermally stable multilayer films of polyimide containing photosensitive disilane unit were applied to KrF excimer laser resists. The multilayer films prepared by the Langmuir-Blodgett technique were found to act as positive working resists with a resolution of 0.25 µm lines and spaces.
Experimental Study of NH3-O2 Oxidation of Si Wafers
Authors: Yen-Chuan Tseng Yen-Chuan Tseng , Katsufusa Shono Katsufusa Shono
Published: February 2005

The oxidation of an Si wafer in dry O2 with a few percent of NH3 added was shown to be a way of obtaining a clean Si-SiO2 interface. The SiO2 thickness grown on an Si wafer was obtained as a function of oxidation time, oxidation temperature and NH3 content in O2. The H2O produced in the oxidation of NH3 in excess O2 ambient enhanced the oxidation rate, which, however, did not exceed that for 100% steam (H2O).
In Situ Reflectance Anysotropy Monitoring of Antiphase Domains Evolution during Growth of GaAs/Si (001)
Authors: González Y. , L. González L. González , F. Briones F. Briones
Published: February 2005

Reflectance Anisotropy Technique is used for the first time to in situ monitor the Antiphase Domain annihilation process during Atomic Layer Molecular Beam Epitaxy (ALMBE) growth of GaAs on Si (001)2° off towards [110] direction. We show that this technique is able to provide quantitative information on the domain evolution from the onset of growth, making possible an accurate determination of the thickness at which single domain GaAs growth front is achieved. Experimental data obtained with this new technique during growth under different conditions might be useful with the modelling of APD annihilation mechanism.
Narrow Band-Gap a-Si:H with Improved Minority Carrier-Transport Prepared by Chemical Annealing
Authors: Das Debajyoti , Shirai Hajime , Jun-ichi Hanna Jun-ichi Hanna , Isamu Shimizu Isamu Shimizu
Published: February 2005

a-Si:H films with narrow optical band gap down to 1.50 eV along with low hydrogen content down to 1 at% were fabricated using the concept of “chemical annealing”; alternating deposition with exposure to atomic hydrogen. Reduction in the density of the valence band tail states was confirmed by a time-of-flight experiment which exhibited non-dispersive behavior in the transient photocurrent curves and significant enhancement in drift mobility to 0.2 cm2/V·s at 300 K for holes. Remarkable improvement in the light induced metastability was also confirmed in some specimens annealed well, maintaining a photoconductivity 10-4 S/cm under AM1 white light illumination.
High Two-Dimensional Electron Gas Mobility Enhanced by Ordering in InGaAs/N-InAlAs Heterostructures Grown on (110)-Oriented InP Substrates by Molecular Beam Epitaxy
Authors: NAKATA Yoshiaki , Osamu UEDA Osamu UEDA , Toshio FUJII Toshio FUJII
Published: February 2005

We report the first mobility enhancement of the two-dimensional electron gas (2DEG) by suppressing alloy scattering in an ordered InGaAs/N-InAlAs heterostructure grown on a (110)-oriented InP substrate by molecular beam epitaxy. Transmission electron microscopy revealed CuAu-I ordered structure consisting of an (InAs)1(GaAs)1 monolayer superlattice in both the <110> growth and <001> directions in the InGaAs channel layer. This heterostructure showed a 2DEG mobility of 153000 cm2/V·s, with a sheet electron concentration (N
s) of 9.9×1011 cm-2 at 6 K (95000 cm2/V·s with N
s of 1.0×1012 cm-2 at 77 K). This mobility is, to our knowledge, the highest reported for InGaAs/N-InAlAs lattice-matched systems.
New Dry Etching Method for the Fabrication of InP/InGaAs Quantum Wires
Authors: Patillon Jean-Noël , Jay Charlotte , Delalande Claude , Iost Michel , Andre Jean-Pierre , Coz Hélène Le , Signles-Frehel Marcel , Soucail Olivier Vlaeminck
Published: February 2005

A new soft dry etching process has been used for the fabrication of quantum structures. It is based on the reversal of thermodynamical equilibrium which can be achieved in a chloride vapor-phase epitaxy reactor. An enhancement of the luminescence intensity is found with decreasing dimensionality, and is compared with a typical reactive ion etching method.
Equally-Spaced Multi-Frequency Laser Emission Generated by Two-Color Stimulated Raman Effect. –Enhancement of Rotational Lines and Suppression of Vibrational Lines–
Authors: Yoshikawa Shigetaka , Kawasaki Shuichi , Totaro Imasaka Totaro Imasaka , Nobuhiko Ishibashi Nobuhiko Ishibashi
Published: February 2005

A two-color laser beam separated by 587 cm-1 is focused into pressurized hydrogen to generate stimulated Raman emission. By optimizing the hydrogen pressure and the beam focusing condition, only rotational lines are generated in the near-UV region; the vibrational lines are completely suppressed. The rotational lines are further enhanced by using a circularly polarized beam.
Processing of Perovskite Pb(Zn<1/3Nb2/3)O3 by Hot Isostatic Pressing and Its Dielectric Properties
Authors: Fujiu Takamitsu , Takenaka Akira Tanaka
Published: February 2005

Perovskite Pb(Zn1/3Nb2/3)O3 (PZN) was obtained by first fabricating pyrochlore PZN ceramics and then converting pyrochlore to perovskite using HIP. PZN ceramics containing as much perovskite as 96% were fabricated under 200 MPa at 1150°C for 1 h. The electromechanical coupling factors and the piezoelectric constants were lower than expected, probably due to the low relative density of the specimen measured.
Design of Optically Coupled Three-Dimensional Content Addressable Memory
Authors: Okano Hiroshi , Takata Hirokazu , Hata Kiyomi , Aibara Reiji , Shin Yokoyama Shin Yokoyama , Mitsumasa Koyanagi Mitsumasa Koyanagi
Published: February 2005

An optically coupled three-dimensional content addressable memory is newly proposed and an example of parallel data processing systems with this memory is described. The new memory employs the optically coupling flip-flop with LEDs and photoconductors for optical data transfer. The optically coupling flip-flop is optimized in design for achieving a high data transfer rate. Simultaneous data inspection through several memory layers can be implemented by using the optically coupled three-dimensional content addressable memory.
Growth of Single Crystals of the Bi-Sr-Ca-Cu-O Superconductor from a KCl Flux
Authors: Takashi Yasuda Takashi Yasuda , Shuzo Takano Shuzo Takano
Published: February 2005

Thermal equilibrium phases of the Bi-Sr-Ca-Cu-O system in the KCl flux are investigated. It is shown that addition of excess CaO+CuO causes an instability of the solid phase against cooling. Besides, growth rate of the 2212-phase becomes lower by increasing the KCl content at a fixed temperature. In a proper condition, platelets grow on top of the melts, and block-like crystals from the deposits at the bottom. The block-like crystals are fair-sized with a good crystallinity. The effect of temperature cycling and addition of a small amount of impurity is also studied.
Excimer Laser-Assisted Chemical Vapor Deposition of Metal-Oxide Thin Film from β-Diketone Complexes
Authors: Ushida Takahisa , Higashiyama Kazutoshi , Izumi Hirabayashi Izumi Hirabayashi , Shoji Tanaka Shoji Tanaka
Published: February 2005

The effects of excimer laser irradiation (KrF: 248 nm) on the CVD of single-source systems (Y(thd)3, Ba(thd)2, and Cu(thd)2, where (thd) represents 2,2,6,6-tetramethyl-3,5-heptanedionate), and double-source systems (Y-Ba, Ba-Cu, and Y-Cu) were investigated. In the single-source system, the laser irradiation promotes the crystallization and oxidation of the deposited oxides, but there is no remarkable change in the deposition rates. On the other hand, in the double-source systems (Ba-Cu and Y-Cu), the irradiation increases the deposition rates and the Cu reactivity with Ba and Y in the vapor phase, and also promotes the crystallization and the oxidation through the uptake of activated oxygen into the films during deposition.
Josephson Junctions Using Polyimide Langmuir-Blodgett Films with a Nb/Au/PI/(Pb-Bi) Structure
Authors: Kubota Tohru , Iwamoto Mitsumasa , Noshiro Hideyuki , Sekine Matsuo
Published: February 2005

We fabricated Josephson junctions with the structure of Nb/Au/PI/(Pb-Bi) using an ultrathin polyimide (PI) Langmuir- Blodgett film as an electrically insulating layer with neither the presence of native oxide layers formed on the base Nb layer nor the dissolution of the base-Nb/Au electrode during the imidization of PAA (Polyamic acid long alkylamine salts) films to produce PI LB films. A typical I-V characteristic of weakly-coupled Josephson junctions was found to be obtained.
As Grown Stress Free GaAs on Si by Regrowth on Chemically Released GaAs on Si Mesas
Authors: Boeck J. De , Hoof C. Van , K. Deneffe K. Deneffe , G. Borghs G. Borghs
Published: February 2005

GaAs layers are grown on GaAs on Si mesas, fabricated using a novel Mesa Release and Deposition (MRD) technique. The mesas that serve as the substrate for selective epitaxy are fabricated in a 1 µm thick GaAs on Si layer. The MRD structures are obtained after a complete underetching of the mesas and subsequent deposition, self-aligned on their original positions. The samples carrying the MRD structures are cleaned before epitaxy and a GaAs epilayer is deposited. Spatialy resolved photoluminescence is used to assess the strain level in the regrown layer. In contrast to the expected shift and splitting of the valence band of biaxially strained GaAs/Si, we find that the peak shift of the band-to-band optical transition of the heteroepitaxial GaAs/MRD/Si to the GaAs reference at 77 K is only 4 nm and no valence band splitting is observed for the regrown layer.
Growth of InAsP on InP by Liquid Phase Electroepitaxy
Authors: Sakai Shiro , Inufushi Kozo , Shintani Toshihisa Hyakuda
Published: February 2005

InAs
x
P1-x
layers were grown on a (100) InP substrate by liquid phase electroepitaxy. A uniform layer was grown by applying a current from the substrate to the melt, while the three-dimensional island growth took place in the conventional temperature-controlled liquid phase epitaxy. The experimental results were explained by the electromigration of the group V elements in the melt. The current tends to fill the grooves on the substrate, resulting in two-dimensional film growth.
Defect Filtering in GaAs on Si by Conformal Growth
Authors: Pribat D. , Provendier V. , Dupuy M. , P. Legagneux P. Legagneux , C. Collet C. Collet
Published: February 2005

Using a newly developed technique of conformal growth, we show that low defect density GaAs films can be obtained from MBE or MOVPE GaAs-coated Si heterostructures. The defect characterization of the conformally grown films has been carried out using transmission electron microscopy and chemical etching. For the first time dislocation densities below 105/cm2 have been observed in submicron GaAs films grown on Si by vapor phase epitaxy.
Fabrication of Vertical-Cavity Front-Surface-Emitting Laser Diode (FSELD) Using a Heterojunction Bipolar Transistor Process
Authors: Yoo Hoi-Jun , Hayes J. R. , Andreadakis N. , Paek E. G. , Harbison J. P. , Kwon L. T. Florez
Published: February 2005

We have investigated a front-surface-emitting laser diode (FSELD) which has both the n and p electrodes on the top surface and emits laser light from the front surface of the wafer. Since its structure is similar to that of HBT, it was fabricated using the conventional HBT process and mask sets. The current flows bypassing the high-series-resistance DBR stacks, and the active layer is surrounded by an oxygen-implanted semi-insulating layer. It showed a low series resistance and low threshold current of 6 mA, for a 25 µm-diameter laser.
Photocurrent Excitation Spectra Observed with Au-Al Heteroelectrodes Biased Reversely and Reflection Spectra in Trans-Polyacetylene
Authors: Kubo Takaya , Tsuji Taishi , Watanabe Toshio , Fukuda Takashi , Hideo Takezoe Hideo Takezoe , Atsuo Fukuda Atsuo Fukuda
Published: February 2005

To understand the low lying excited states of trans-polyacetylene, optical properties were studied at room temperature on carefully prepared samples by measuring photocurrent (PC) and photovoltage excitation spectra as well as optical absorption and reflectance. The 1.4 eV PC peak, the appearance of which sensitively depends on the sample quality, is correlated with some additional absorption sticking to the intrinsic absorption edge. An enhancement of PC with Au-Al electrodes biased reversely was observed in excitation spectra between 1.5∼2.0 eV, indicating that the formation of excitons causes three reflection peaks in this spectral region.
Structural Properties of (GaAs)1-x(Si2)x Layers on GaAs(100) Substrates Grown by Migration-Enhanced Epitaxy
Authors: Rao T. Sudersena , Kazuhiko Nozawa Kazuhiko Nozawa , Yoshiji Horikoshi Yoshiji Horikoshi
Published: February 2005

Epitaxial (GaAs)1-x
(Si2)
x
alloy layers (0<x<0.25) were grown on GaAs (100) substrates using Migration-Enhanced Epitaxy. Structural and compositional analysis of the as-grown (GaAs)1-x
(Si2)
x
layers indicated single-crystal zincblende structure with no evidence of phase separation throughout the entire compositional range. The lattice constant a
0 of the alloys was found to decrease linearly with increasing Si content from 0.56543 nm at x=0 to 0.5601 nm at x=0.25. Double crystal X-ray rocking curve measurements and cross-sectional transmission electron microscopy studies made on a 10 period (GaAs)0.80(Si2)0.20/GaAs strained-layer superlattice indicated sharp and abrupt interfaces of high crystalline quality.
Single Crystallization of Aluminum on SiO2 by Thermal Annealing and Observation with Scanning µ-RHEED Microscope
Authors: Masu Kazuya , Tsubouchi Kazuo , Hiura Yohei , Tatsuya Matano Tatsuya Matano , Nobuo Mikoshiba Nobuo Mikoshiba
Published: February 2005

We have found single crystallization of Al on patterned SiO2 by thermal annealing. Via-holes on the Si wafer were completely planarized by selective and nonselective chemical vapor deposition of Al using dimethylaluminum hydride and hydrogen. Single crystallization of Al on patterned SiO2 was observed with a scanning µ-RHEED microscope. Polycrystal (100) Al film on patterned SiO2 was changed into single-crystal (111) Al after the annealing at 645°C.
C-Axis Oriented YBa2Cu3O6.8 Films on Amorphous Silicate Glasses Using Laser Deposition
Authors: Narumi Eiki , Song Liwei , Li Cehui , Kao Yi-Han , Patel Sushil , Shaw David T. , Shue Shaulin , Fujino Kozo
Published: February 2005

In situ laser deposition was used to fabricate YBa2Cu3O6.8 (YBCO) films on amorphous glasses. Yttrium stabilized zirconia (YSZ) and conducting indium-tin-oxide (ITO) were used as the buffer layers to improve the transport properties of YBCO films. There was negligible interdiffusion occurring at the interfaces. YBCO films were strongly c-axis oriented normal to the substrate. However, those films were randomly oriented in the a-b plane. T
c
′s of 81 K and 72 K were achieved for YBCO films, with a YSZ buffer and an ITO buffer, respectively. Also, the resistivity of the ITO buffer fabricated by laser deposition was in the order of 10-4 Ω·cm.
Estimation of Threshold Current of Microcavity Surface Emitting Laser with Cylindrical Waveguide
Authors: Tamanuki Takemasa , Fumio Koyama Fumio Koyama , Kenichi Iga Kenichi Iga
Published: February 2005

We have estimated a threshold current of a microcavity surface emitting laser with a cylindrical optical waveguide and quantum well structure. The possibility of extremely low-threshold-current (I
th<1 µA) operation of a GaAlAs/GaAs laser is suggested.
Temperature Profiles in Etched-Well Surface-Emitting Semiconductor Lasers
Authors: W\lodzimierzNakwaski W\lodzimierzNakwaski , Marek Osiński Marek Osiński
Published: February 2005

Radial distributions of temperature profiles in the active layer of etched-well vertical-cavity surface-emitting lasers are determined using a new comprehensive two-dimensional thermal model featuring realistic distribution of heat sources. Self-consistency between electrical and thermal processes is achieved. Importance of two- dimensional current- and heat-spreading is demonstrated.
Comments on “Anomalously Large Shift of Absorption Edge of GaSe-Based Layered Crystals by Applied Electric Field”
Authors: Segura Alfredo , Miguel V. Andrés Miguel V. Andrés , Vicente Mun̄oz Vicente Mun̄oz
Published: February 2005

Electroabsorption results in Gallium Selenide crystals can be explained in terms of standard Franz-Keldysh broadening of the exciton absorption peak. The anomalous effect observed by the authors of the commented paper is shown to have thermal origin.
Memory Effects of Light Transmission Properties in Polymer-Dispersed-Liquid-Crystal (PDLC) Films
Authors: Rumiko Yamaguchi Rumiko Yamaguchi , Susumu Sato Susumu Sato
Published: February 2005

A new type of memory effect is observed in polymer-dispersed-liquid-crystal (PDLC) film with UV-curable polymer. The transmittance of the memory state is preserved for a long time after an applied voltage is removed. In this state, the resistivity of the film decreases and the dielectric constant increases comparing to those of the initial off state. The memory state can be erased and changed to the scattering off state by heating the film to the clearing temperature of the liquid crystal.
Preparation of Cu9Al4 Intermetallic Compound Films as a Metallization Material for LSI Technology
Authors: Atsushi Noya Atsushi Noya , Katsutaka Sasaki Katsutaka Sasaki
Published: February 2005

The intermetallic compound film of Cu9Al4 was prepared by cosputtering at substrate temperatures below 300°C. The prepared film is structurally quite stable up to about 700°C, showing little change in X-ray diffraction pattern. The film with well-textured polycrystalline grains has a low electrical resistivity of 13 µΩ-cm. It is revealed that the films obtained have sufficiently promising properties well applicable as metallization material for large-scale integrated circuits.
Some Results Obtained by a Newly Constructed Ultra-High-Resolution 1300 kV Electron Microscope
Authors: Matsui Yoshio , Horiuchi Shigeo , Bando Yoshio , Kitami Yoshizo , Yokoyama Masato , Suehara Shigeru , Matsui Isao , Katsuta Teiji
Published: February 2005

A new ultra-high-resolution electron microscope with a point-to-point resolution of 0.1 nm at 1300 kV was constructed. A lattice fringe image of 0.07 nm due to an interaction of two 220 reflections of gold was clearly observed, indicating good stability of the microscope. The so-called “black-atom” image of silicon was obtained. Direct observations of oxygen positions in Y-stabilized zirconia were also achieved successfully. All the metal atom positions in YBa2Cu3O
y
superconductor were observed clearly as dark dots, while imaging of oxygen positions has not yet been successful.
In Situ Photoconductive Monitoring of Phthalocyanine Thin Film Growth
Authors: Nobutsugu Minami Nobutsugu Minami , Michihiko Asai Michihiko Asai
Published: February 2005

The in situ measurement of lateral photocurrent has been carried out while the vacuum evaporation of phthalocyanine (Pc) thin films was in progress. After a very steep rise ranging from 3 to 4 orders of magnitude, the photocurrent increase slowed abruptly around a film thickness of 5-6 nm. The scanning electron microscopic observation of Pc layers have revealed the existence of cluster structures at an early stage of thin film growth. The behaviors of the in situ photocurrents are understood in terms of the growth and coalescence of the cluster structures.
Electrical Conductivity and Thermoelectric Power of Langmuir-Blodgett Films of Tridecylmethylammonium-Au(dmit)2
Authors: Miura Yasuhiro F. , Takenaga Mitsuru , Kasai Akinari , Nakamura Takayoshi , Matsumoto Mutsuyoshi , Kawabata Yasujiro
Published: February 2005

Thermoelectric power and electrical conductivity in Langmuir-Blodgett (LB) films of tridecylmethylammonium-Au(dmit)2 have been measured in the temperature range of 300 to 125 K. The conductivity in the lateral direction of the LB films is 30 S/cm at room temperature. The conductivity increases down to around 200 K, and decreases below that temperature. The thermoelectric power is positive and its temperature dependence shows a metallic behavior in the temperature range measured. The average value in thermoelectric power at room temperature is 20 µV/K.
Improvement of Regrown Interface in InP Organo-Metallic Vapor Phase Epitaxy
Authors: Miyamoto Yasuyuki , Hirayama Hideki , Suemasu Takashi , Miyake Yasunari , Arai Shigehisa
Published: February 2005

It is shown that a preheating process in a pure hydrogen atmosphere with a (NH4)2S
x
treatment was effective for improvement of the regrown interface in InP organometallic vapor phase epitaxy (OMVPE). The carrier concentration was under 5×1015 cm-3 in the entire region after the regrowth, even if we carried out various dummy processes of fabrication between the first growth and the surface treatment for improvement. Thus, this improvement will be useful for the device-required regrowth process after fabrication of an ultrafine-size structure.
Role of Atomic Hydrogen During Growth of Hydrogenated Amorphous Silicon in the “Chemical Annealing”
Authors: Shirai Hajime , Jun-ichi Hanna Jun-ichi Hanna , Isamu Shimizu Isamu Shimizu
Published: February 2005

In our previous paper, we proposed a novel preparation technique termed “Chemical annealing” to make a rigid and stable Si-network. In this letter, with the aim of the understanding the role of atomic hydrogen on the growing surface, systematic studies were made on the concentrations of H and D for the chemically annealed films made by SiH4 and atomic deuterium system as a function of the deposition time in one cycle, the annealing time and the substrate temperature. In the chemically annealed film, the structural relaxation is thermally activated with an activation energy of 0.3 eV. The role of atomic hydrogen is the creation of dangling bonds in the top surface for the enhancement of a cross linking reaction; passivation of dangling bond and break of weak Si-Si bonds for the rearrangement of Si-network. In comparison with the post-deutrization results, the role of atomic hydrogen in the “Chemical annealing” is discussed.
Growth Mechanism of YBa2Cu4O8(124) Phase in Metalorganic Chemical Vapor Deposition Film
Authors: Hayashi Harumi , Yamada Yasuji , Sugimoto Tsunemi , Yuh Shiohara Yuh Shiohara , Shoji Tanaka Shoji Tanaka
Published: February 2005

Recently, we reported that Y-Ba-Cu-O superconducting films containing the 124 phase were fabricated by MOCVD below 800°C without post annealing. In this study, efforts were focused on clarifying when the 124 phase appears and how the 124 grain grows. From annealing experiments, it is clear that the 124 phase is not formed as a result of solid state reaction, but it grows during deposition. The results from different deposition times under the same conditions, show that the upper part and the lower part of the film consist differently, and that in the part near the film surface, 124 is the main phase.
Changes of Superconductivity and Crystal Structure on Ba2YCu3O7-x by 1 MeV Ar+ Ion Irradiation
Authors: Terai Takayuki , Furuta Tai , Masegi Tamaki , Kazuyuki Kusagaya Kazuyuki Kusagaya , Yoichi Takahashi Yoichi Takahashi
Published: February 2005

Effects of 1 MeV Ar+ ion irradiation on thin films of high-T
c oxide superconductor Ba2YCu3O7-x
(BYCO) were investigated in the fluence range between 1.7×1010 ions/cm2 and 9.9×1013 ions/cm2. Increase of transport critical current density (J
c) by irradiation was observed with a fluence below 1.3×1011 ions/cm2, while the critical temperature (T
c) was unchanged in this fluence region. With a fluence above 3.4×1011 ions/cm2, both T
c and J
c decreased with increasing fluence. Regarding the change of the crystal structure, expansion of the c-axis lattice constant and an increase of full width at half maximum(FWHM) value of the peak in X-ray diffraction were observed above a fluence of 1.0×1013 ions/cm2. These results suggest that the radiation induced defects act as pinning centers in the low fluence region, and they cause the destruction of the crystal structure in the high fluence region.
Analysis of Donor and Compensation Ratio in I-Doped ZnSe by Far-Infrared Magnetoabsorption
Authors: Saito Ken , Yamada Syoji , Ohki Akira , Ando Koshi
Published: February 2005

The first far-infrared (FIR) magnetoabsorption study of iodine (I)-doped n-ZnSe is described. The FIR experiments are carried out by observing the Zeeman absorption spectra with a FIR-laser and high-magnetic fields. Four different donor species, including the I-donor, are resolved, and the I-donor ionization energy of 25.6 meV is precisely estimated. Moreover, compensation ratios and absolute donor (or acceptor) densities N
d are determined. As a result, it is found that the acceptor density N
a increased almost linerly with increasing N
d. This suggets a deep and complex origin for the acceptors in the I-doped ZnSe.
Au+-Ion-Implanted Silica Glass with Non-Linear Optical Property
Authors: Fukumi Kohei , Chayahara Akiyoshi , Kadono Kohei , Sakaguchi Toru , Horino Yuji , Miya Masaru , Junji Hayakawa Junji Hayakawa , Mamoru Satou Mamoru Satou
Published: February 2005

Au+ ions have been implanted in silica glass at an acceleration energy of 1.5 MeV and a fluence level of 1017 ions/cm2. The Au ions form colloid particles with the radius of 2.9 nm after heat treatment. The glass with Au colloid particles shows the large third order non-linear susceptibility; χ(3)=1.2×10-7 esu. The large χ(3) value of the glass is attributed to the high concentration of Au colloid particles in the narrow region.
Copper Vapor Laser Pumped Single-Mode Grazing Incidence Dye Laser Using Dye Jet
Authors: Maruyama Yoichiro , Masaaki Kato Masaaki Kato , Takashi Arisawa Takashi Arisawa
Published: February 2005

A Littman type grazing incidence dye laser using a dye jet is designed and single-mode operation is demonstrated at a pulse repetition frequency of 6000 Hz. The frequency width of the laser is around 1 GHz and the pulse duration about 4 ns (FWHM).
Anomalous Diamagnetism of a Perovskite LaVO3
Authors: Naoki Shirakawa Naoki Shirakawa , Masayasu Ishikawa Masayasu Ishikawa
Published: February 2005

We have found that a perovskite LaVO3 exhibits a cubic-to-orthorhombic transformation, immediately followed by a magnetic transition into a large diamagnetic state below about 135 K. Resistivity measurement revealed that the compound is a semiconductor in the whole temperature range investigated, with a slightly larger resistivity in the diamagnetic state. A small negative remanent moment was confirmed at low temperatures, and similarities and dissimilarities to other magnetic oxide systems are discussed.
Surface Structure of InAs (001) Treated with (NH4)2Sx Solution
Authors: Katayama Mitsuhiro , Aono Masakazu , Oigawa Haruhiro , Nannichi Yasuo , Sugahara Hirohiko , Oshima Masaharu
Published: February 2005

The surface structure of (NH4)2S
x
-treated InAs (001) was studied by means of coaxial impact collision ion scattering spectroscopy (CAICISS) and low-energy electron diffraction (LEED). These observations revealed that arsenic atoms at the outermost surface are partially replaced by sulfur atoms. Significantly, the (2×1) reconstruction of the (NH4)2S
x
-treated surface with heat treatment at 380°C is described by the formation of dimers lined up in [11̄0] direction. This surface model is supported by the data obtained by synchrotron radiation photoemission spectroscopy (SRPES).
Effect of Pt Addition on Melt-Processed YBaCuO Superconductors
Authors: Morita Mitsuru , Tanaka Masamoto , Takebayashi Seiki , Kimura Keiichi , Katsuyoshi Miyamoto Katsuyoshi Miyamoto , Kiyoshi Sawano Kiyoshi Sawano
Published: February 2005

Platinum addition in precursors of melt processing could produce finely dispersed Y2BaCuO5 (211) inclusions of about 1 µm in YBa2Cu3O
x
matrix. This fine dispersion of 211 resembles that of quench-and-melt-grown materials. The platinum-added sample exhibited a critical current density exceeding 2×104A/cm2 at 77 K and 1 T. Platinum is considered to enhance the nucleation of 211 which forms by the pertitectic reaction between Y2O3 and liquid phase.
The Irradiation Effects of an Oxygen Radical Beam on the Preparation of Superconducting Thin Films
Authors: O'keeffe Patrick , Komuro Shuji , Den Shoji , Morikawa Takitaro , Aoyagi Yoshinobu
Published: February 2005

Irradiation using oxygen radicals O* and ions O2
+ from an active ECR oxygen plasma source has been applied to the preparation of Y-Ba-Cu-O superconducting films. Irradiation by oxygen radicals O* was found to drastically improve the films characteristics over those prepared in the presence of oxygen ions O2
+. This effect is considered to be as a result of enhanced and damage-less surface interactions due to oxygen radicals.
Sweeping of Trapped Flux in Superconductors Using Laser Beam Scanning
Authors: Geng Qiquan , Minami Hirofumi , Chihara Kazunori , Junpei Yuyama Junpei Yuyama , Eiichi Goto Eiichi Goto
Published: February 2005

A new technique has been developed to remove flux quanta trapped in superconducting film. It consists of measuring the magnetic field distribution over a superconductor with an rf SQUID and removing the detected trapped flux using laser beam scanning. The trapped flux movement follows the motion of the Ar laser beam exactly. By scanning the laser beam over the trapped flux quanta, the trapped flux is successfully moved to any desired location.
Leakage Current Reduction of Poly-Si Thin Film Transistors by Two-Step Annealing
Authors: Aoyama Takashi , Mochizuki Yasuhiro , Kawachi Genshiro , Saburo Oikawa Saburo Oikawa , Kenji Miyata Kenji Miyata
Published: February 2005

Leakage currents of polysilicon TFT's (thin film transistors) were reduced significantly by a two-step annealing technique which utilized low-temperature crystallization of amorphous films and a reduction of trap states by a high-temperature process. Two-step annealing formed polysilicon films with larger grains and lower electron spin densities. Trap state densities obtained from TFT on-currents correlated strongly with the leakage currents of the TFT's.
Observation of Focused Electron Beams inside a High-Tc Bulk Superconductor Lens (Supertrons)
Authors: Matsuzawa Hidenori , Osada Tomoaki , Ohya Makoto , Tsuji Takahisa , Yukio Chino Yukio Chino , Tetsuya Akitsu Tetsuya Akitsu
Published: February 2005

Focusing of intense electron beams (340 keV, 0.8 kA, and 10 ns) was confirmed visually inside a high-T
c bismuth-based bulk superconductor lens (Supertrons) with image fibers. The electron beams were focused to 1.1 mm in diameter (full width at half-maximum) at the exit of the lens, the narrowest beams which have been achieved with Supertrons.
Theoretical Analysis for a New Package Concept: High-Speed Heat Removal for VLSI Using an AlN Heat-Spreading Layer and Microchannel Fin
Authors: Tsubouchi Kazuo , Utsugi Satoshi , Tomoshi Futatsuya Tomoshi Futatsuya , Nobuo Mikoshiba Nobuo Mikoshiba
Published: February 2005

We propose a microchannel-fin package concept utilizing an AlN passivation layer as the heat spreader and a microchannel fin as an efficient means of heat removal. AlN film has high thermal conductivity and compatibility with the thermal expansion coefficient of Si. A microchannel fin has 4-fold 100 lines of 50 µm×250 µm channels on a 1 cm2 chip. The simulation of dynamic thermal analysis for the new package concept showed that the chip temperature was below 47°C at a power density of 1.5 kW·cm-2 when the liquid-cooled microchannel-fin package was used and below 49°C at 30 W·cm-2 when a compressive-air-cooled microchannel-fin package was used.
Very Stable a-Si:H Prepared by “Chemical Annealing”
Authors: Shirai Hajime , Jun-ichi Hanna Jun-ichi Hanna , Isamu Shimizu Isamu Shimizu
Published: February 2005

Chemical reactions in the growing surface responsible for the structural relaxation during the “chemical annealing” (CA) treatment were investigated to reveal the role of active species such as atomic hydrogen and excited states of noble gases such as He* and Ar*. Not only atomic hydrogen, but also excited species, Ar* or He*, were responsible for the decrease in hydrogen content in the hydrogenated amorphous silicon (a-Si:H) films. Structural relaxation was also enhanced with He* and Ar*. The stability under illumination was remarkably improved in the films prepared by the CA process at substrate temperatures higher than 300°C.
Highly Reliable 150 mW CW Operation of Single-Stripe AlGaAs Lasers with Window Grown on Facets
Authors: Sasaki Kazuaki , Matsumoto Mitsuhiro , Kondo Masaki , Ishizumi Takashi , Takeoka Tadashi , Saburo Yamamoto Saburo Yamamoto , Toshiki Hijikata Toshiki Hijikata
Published: February 2005

High-power single-stripe AlGaAs lasers with a new type of window structure named “window grown on facets (WGF)” are described here for the first time. In the lasers, window layers have been grown on cleaved (110) facets, independent of the internal laser structures. A stable fundamental transverse mode has been obtained up to more than 200 mW of output power in the wavelength range of 830 nm. No obvious degradation has been observed beyond 2000 hours under 100 mW and 150 mW CW operation at 50°C.
Low-Temperature Molecular Beam Epitaxy Growth of Single Quantum Well GaAs/AlGaAs Lasers
Authors: Sei-ichi Miyazawa Sei-ichi Miyazawa , Yoshinobu Sekiguchi Yoshinobu Sekiguchi
Published: February 2005

We report on the low-temperature Molecular Beam Epitaxy (MBE) growth of single quantum well (SQW) GaAs/AlGaAs lasers under a low flux ratio. Lasing action was observed at a substrate temperature as low as 300°C. A threshold current density of 600 A/cm2 was obtained at the substrate temperature of 375°C, which is the lowest threshold current density below 400°C reported so far.
Secondary Ion Yield Changes in Si due to Topography Changes during Cs+ Ion Bombardment
Authors: Shichi Hiroyasu , Kazuhiro Ohnishi Kazuhiro Ohnishi , Setsuo Nomura Setsuo Nomura
Published: February 2005

Depth profiles of 30Si negative secondary ions were measured at Cs+ ion impact energies of 10.5 keV, 14.5 keV and 17.5 keV and a 45° impact angle by means of secondary ion mass spectrometry (SIMS). Yield changes due to surface topography changes occurred at 14.5 keV and 17.5 keV impact energy, although no surface topography change has ever been reported during Cs+ ion bombardment. No yield change was detected at 10.5 keV impact energy. The topography changes and ion yield changes are obviously affected by the Cs+ ion impact energy.
Properties of the Excitonic Emission at Room Temperature in Cd0.3Zn0.7S/ZnS Strained-Layer Superlattices
Authors: Tsunemasa Taguchi Tsunemasa Taguchi , Yasuyuki Endoh Yasuyuki Endoh
Published: February 2005

Cd0.3Zn0.7S/ZnS multiple-quantum-well strained-layer superlattices with a range of well widths can produce excitonic emissions around 3.4 eV at room temperature (RT), due to the quantum confinement of excitons in the CdZnS wells. The emission spectra of a 41 Å Cd0.3Zn0.7S well were extensively studied under high optical excitation. We found a non-linear dependence of the spontaneous RT exciton-emission intensity on the excitation intensity for high excitations. With increasing excitation density, the emission line moves to slightly the lower-photon energy and in addition its linewidth is broadened. A shoulder on higher-energy side of the excitonic spectrum appears above about 100 kW/cm2, which is related to an optical transition associated with a higher excited-level state of the electrons confined in the conduction-band potential well.
Gas-Phase Nucleation in GaAs Thin Film Preparation by Metal Organic Chemical Vapor Deposition
Authors: Okuyama Kikuo , Huang David D. , Seinfeld John H. , Tani Naoyuki , Matsui Isao
Published: February 2005

GaAs epitaxial film growth in the metal organic chemical vapor deposition (MOCVD) horizontal reactor was analyzed by a mathematical model, which takes into consideration of vapor phase hydrodynamic and kinetic phenomena including decomposition reactions of reactants, Ga or GaAs nucleation and subsequent particle growth. The position dependent changes in mass concentrations of Ga or GaAs monomers and homogeneously nucleated Ga or GaAs particles are predicted under various substrate temperatures. The appearance of particles in the gas phase is found to be enhanced under substrate temperature exceeding about 900 K. The conditions under which the growth of the thin film is governed by the diffusive deposition of metal organic vapor and Ga monomers are determined, and the effect of homogeneously nucleated particles on the growth of thin film has been clarified. The simulation results are in good agreement with the data of van de Ven et al [J. Cryst. Growth 76 (1986) 352].
LPE Ga1-xInxSb Multigrading Layers with Cut-off Wavelength up to 4.71 µm (x=0.75)
Authors: Xiuying Gong , Okitsu Kazuhiko , Hayakawa Yasuhiro , Tomuo Yamaguchi Tomuo Yamaguchi , Masashi Kumagawa Masashi Kumagawa
Published: February 2005

The dependence of the energy band-gap on In atomic fraction for the liquid phase epitaxy (LPE) GaInSb/GaSb multigrading layers has been investigated by infrared transmission measurements combined with electroprobe microanalysis (EPMA). The result showed that epilayers with cut-off wavelength up to 4.71 µm at room temperature and with In atomic fraction as high as 0.75 have been obtained for the first time.