bluuebunny/crossref_metadata_2025 huggingface dataset:
Characteristics of Electron Trap Induced in n-InP by Hydrogen Plasma Exposure
Authors: Sugino Takashi , Ninomiya Hideaki , Matsuda Koichiro , Junji Shirafuji Junji Shirafuji
Published: October 2002

Behaviors of the electron trap at E
c-0.51 eV in n-InP treated with hydrogen plasma have been investigated by isothermal capacitance transient spectroscopy. It is found that considerable enhancement of the trap density occurs when a reverse bias voltage of only -1 V is applied to Au Schottky junctions on n-InP treated with hydrogen plasma. This implies that the enhancement of the electron trap is due to a dissociation of plasma-induced defect-hydrogen complexes into electrically active defects and hydrogen. An isochronal annealing experiment shows that the annealing procoss follows the first-order reaction kinetics and its activation energy is 1.4 eV.
Low-Temperature Metalorganic Chemical Vapor Deposition Growth of InGaAs for a Non-Alloyed Ohmic Contact to n-GaAs
Authors: Watanabe Noriyuki , Takumi Nittono Takumi Nittono , Hiroshi Ito Hiroshi Ito
Published: October 2002

The growth of In

x

Ga1-
x

As (0≤x≤0.8) on GaAs substrates by metalorganic chemical vapor deposition (MOCVD) is systematically studied. The In distribution coefficient for the InGaAs system at low growth temperatures was larger than unity and increased with decreasing growth temperature. The surface morphology can be improved by decreasing the growth temperature. The decrease of the carrier concentration in the Si-doped InGaAs layer after annealing at temperatures ranging from 500 to 700°C was smaller in the higher In composition samples. A contact resistivity of 4×10-7 Ω·cm2 was obtained for the InGaAs contact with In composition of 0.7.
Gas-Source Molecular Beam Epitaxial Growth of (Zn, Mg)(S, Se) Using Bis-methylcyclopentadienyl-magnesium and Hydrogen Sulfide
Authors: Suda Jun , Kawakami Yoichi , Shizuo Fujita Shizuo Fujita , Shigeo Fujita Shigeo Fujita
Published: October 2002

In this letter we report the first successful gas-source molecular beam epitaxy (GSMBE) of ZnMgSSe on (100) GaAs substrates. Source materials used were elemental zinc (Zn), elemental selenium (Se), hydrogen sulfide ( H2S) and bis-methylcyclopentadienyl-magnesium ((M
e
C
p)2
M
g). It is revealed that the growth by this technique results in good controllability of solid compositions of this quaternary alloy system. Photoluminescence and X-ray diffraction measurements show that the layer coherently grown on GaAs exhibits high quality comparable to that grown by conventional molecular beam epitaxy (MBE).
Interference Effects in Si/Ge Strained Multivalley Superlattice Structures
Authors: Jih-Chen Chiang Jih-Chen Chiang
Published: October 2002

The energy-band spectrum of a Si/Ge strained multivalley superlattice structure is investigated within an anti-bonding orbital model. It is shown that the energy-band spectrum as a function of the well-width exhibits a pairing interference pattern due to inter-valley mixing effect. We found two interesting interference effects: In each pair, not only (1) the energy separation between the two bands but also (2) the two band-widths are oscillatory functions of the width of the well material.
Observation of Magnetic Stripe Domains in Ni–Fe Films Using Spin-Polarized Scanning Electron Microscopy
Authors: Sudo Shuji , Mitsuoka Katsuya , Koike Kazuyuki , Matsuyama Hideo , Sugita Yutaka
Published: October 2002

Magnetic stripe domains in evaporated Ni–Fe films were observed by using spin-polarized scanning electron microscopy (spin-SEM). At the surface of the Ni–Fe film, both the magnetization components in the film plane, M

x
and M

y
, perpendicular and parallel to the stripes, respectively, change periodically across the stripe domains. The wavelength for M

x
change is twice the stripe width, while the wavelength for M

y
is the same as the stripe width. The amplitude for M

x
change is larger than that for M

y
. From this it has been clarified that the magnetization near the surface not only rotates upwards and downwards from the film plane, but also rotates in the film plane across the stripe domains.
Structure of a Twin Boundary in YBa2Cu3O6.9
Authors: Shigeo Horiuchi Shigeo Horiuchi , Akira Ono Akira Ono
Published: October 2002

The structure of a twin boundary in YBa2Cu3O6.9 is analyzed by using high-resolution transmission electron microscopy. It is observed to be of oxygen-centered type. The diffraction streak, which is excited only from the boundary region, is explained with help of optical diffraction for a model structure of tilted anti-phase boundary.
Layered Structure and Superconducting Properties of Ag-Sheathed Bi1.84Pb0.34Sr2Ca2Cu3OyWires Prepared by Combined Jellyroll and Hotextrusion Technique
Authors: Matsuzaki Kunio , Shimizu Kohichi , Akihisa Inoue Akihisa Inoue , Tsuyoshi Masumoto Tsuyoshi Masumoto
Published: October 2002

The superconducting wires were prepared by hotextrusion of a billet of jellyroll form. The wire exhibited a layered structure of Ag and Bi2223 oxide. Critical current density (Jc) increased with decreasing diameter of extrusion die and the highestJcvalue for the wire with 2 mm diameter is 3200 A/cm2at 77 K and 18000 A/cm2at 4.2 K. These rather highJcvalues are due to the increase of the interface area between Ag and oxide resulting from the decrease in the thickness of the oxide layer. This method seems to be a useful way of obtaining the superconducting wire with a round shape for the Bi2223 oxide.
Superconducting Properties of Ultrathin Films of YBa2Cu3Ox Prepared by Metalorganic Chemical Vapor Deposition at 500°C
Authors: Zama Hideaki , Saga Jun , Hattori Takeo , Shunri Oda Shunri Oda
Published: October 2002

Low-temperature ( 500°C) growth of YBa2Cu3O

x

films by metaloganic chemical vapor deposition on (100)MgO substrates using N2O as an oxidizing agent has been investigated. Films 12 unit cells thick show superconducting onset critical temperature of 89 K and zero-resistivity critical temperature of 80 K. Films 4 unit cells thick show T
c (zero) of 30 K. Films as thin as 3 unit cells thick reveal superconducting onset characteristics. If the topmost (cap) layer and the bottom (buffer) layer are nonsuperconducting, this result suggests that superconductivity arises even from monomolecular layer of YBa2Cu3O

x

.
Efficient 1.5 µm to Visible Upconversion in Er3+-Doped Halide Phosphors
Authors: Wang Junichi Ohwaki
Published: October 2002

Bright visible fluorescence was emitted from Er3+-doped halide phosphors and ErX3 (X=Br, I), under 1.5 µm laser diode (5 mW) excitation. While green fluorescence was predominant with chloride ( BaCl2:Er) and bromide ( YBr3:Er), yellowish fluorescence was observed with iodide ( YI3:Er) and fluoride ( YF3:Er). The 550 nm green fluorescence intensities for the chloride, bromide and iodide were, respectively, 43, 10 and 2 times greater than that of conventional fluoride. The excitable wavelength region around 1.5 µm narrowed and the excitation peak shifted toward a longer wavelength with a decrease in the ligand field strength or in the matrix phonon energy.
Oxidation Properties of Nitrogen-Doped Silicon Films Deposited from Si2H6 and NH3
Authors: Scheid Emmanuel , Temple Boyer Pierre , Samitier Josep , Hassani Ahmed El
Published: October 2002

Si2H6/NH3 gas mixture was employed to obtain, by low-pressure chemical vapor deposition (LPCVD) at low temperature, nitrogen-doped silicon (NIDOS) films with various N/Si ratios. Thermal oxide was grown in dry oxygen at 900°C and 1100°C on NIDOS films. The result indicates that the nitrogen content of NIDOS films, assessed by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR), greatly influences their oxidation rate.
Observation of Anomalous Current-Voltage Characteristics in Organic Multilayer-Structure Diode
Authors: Ohmori Yutaka , Morishima Chikayoshi , Akihiko Fujii Akihiko Fujii , Katsumi Yoshino Katsumi Yoshino
Published: October 2002

A multilayer-structure diode consisting of alternating layers of organic perylene derivative and aromatic diamine has been fabricated by organic molecular beam deposition. The diode with multilayer structure shows anomalous current-voltage characteristics compared with those of a monolayer-heterostructure diode. The diode also shows electroluminescent characteristics, emitting red light at 632 nm at room temperature. The diode characteristics have been discussed in terms of the tunneling current of the multilayer structure.
Contact Electrification on Thin SrTiO3 Film by Atomic Force Microscope
Authors: Uchihashi Takayuki , Okusako Takahiro , Yamada Junji , Fukano Yoshinobu , Sugawara Yasuhiro , Igarashi Masaru , Kaneko Reizo , Seizo Morita Seizo Morita
Published: October 2002

Recently, we achieved reproducible and controllable contact electrification with a modified atomic force microscope (AFM). In the present paper, we report on the application of this novel microscopic method to investigate dissipation and spatial distribution of contact-electrified charges on SrTiO3 (STO) thin films with large dielectric constants. A charge dot with a Full width at half-maximum as small as 70 nm has been deposited using this technique. We also succeeded in depositing two adjacent dots with arbitrary charge signs. Thus, its potential capability for application to charge storage was clarified experimentally.
Phase Shift and Frequency Doubling on Intensity Oscillations of Reflection High-Energy Electron Diffraction: One-Beam Dynamical Calculations for Ge on Ge(111) Surface
Authors: Yoshimi Horio Yoshimi Horio , Ayahiko Ichimiya Ayahiko Ichimiya
Published: October 2002

Reflectivities of a high-energy electron beam are calculated under the one-beam condition with varying growing layer thickness and glancing angle of the incident electron beam as an example of Ge growth on a Ge(111) surface. The potential in the growing layer is assumed to be proportional to layer coverage. In order to investigate characteristic behaviors of reflectivity, a simple “birth-death model” is used to simulate the growth mode. It is revealed that the phase of diffracted electron waves in the growing layers play an important role in the understanding of “phase shift”, “frequency-doubling” and also characteristic change of rocking curves, which are observed in experiments.
Improvement of Spatial Resolution of a Laser-Scanning pH-Imaging Sensor
Authors: Nakao Motoi , Tatsuo Yoshinobu Tatsuo Yoshinobu , Hiroshi Iwasaki Hiroshi Iwasaki
Published: October 2002

We investigated the spatial resolution of a laser-scanning semiconductor-based pH-imaging sensor both experimentally and theoretically. A spatial resolution better than 100 µ m was obtained by thinning the Si substrate to 100 µ m. The simulation results on the spatial resolution based on a carrier diffusion model agreed well with those obtained by experiment. From the simulation results, we also predicted the optimal choice of parameters of Si substrate (thickness, doping, etc.) for the pH-imaging sensor.
Electrical Conductions of High Mobility Poly-Si Thin Film Transistors at Low Temperatures
Authors: Serikawa Tadashi , Shirai Seiiti , Takaoka Sadao , Murase Kazuo , Ishida Shuichi
Published: October 2002

N-channel, polycrystalline silicon thin-film transistors (poly-Si TFTs) with high field-effect mobility of 160 cm2/ V· s are fabricated from sputter-deposited Si film irradiated with laser light. Electrical properties, including Hall effects, of the poly-Si TFTs are measured at temperatures from 300 K to 4.2 K. At high gate voltages, the conductivities of the poly-Si TFTs increase with decreasing temperature down to 220 K, but below 200 K, they decrease with decreasing temperature even at high gate voltages, which produce low potential barriers at grain boundaries. At temperatures from 300 K to 100 K, the carriers show activation-type conduction. Below about 40 K, the conductivity obeys a variable-range hopping mechanism between localized states at grain boundaries. Hall effect measurements show that carrier density is nearly independent of temperature and that carrier velocity plays a more important role rather than carrier density in the electrical properties of poly-Si TFTs over the wide range of temperature.
Novel Circular Grating Surface-Emitting Laser with Emission from Center
Authors: Wu Chunmeng , Makino Toshihiko , Fallahi Mahmoud , Craig Robert G. A. , Knight Gordon , Templeton Ian , Cornelis Blaauw Cornelis Blaauw
Published: October 2002

In this letter, we propose a new circular grating surface-emitting laser that is featured by a central emission area. Pulsed room temperature operation has been demonstrated.
Laser-Induced Dry Cleaning in Air–A New Surface Cleaning Technology in Lieu of Carbon Fluorochloride (CFC) Solvents
Authors: Aoyagi Yong-Feng Lu
Published: October 2002

Surface contaminations are removed by laser irradiation with pulse output and short wavelength. It is a new dry cleaning process to remove surface organic contaminations without using ultrasonic cleaning with carbon fluorochloride (CFC) and other organic solvents. This provides a new dry process to clean different substrate surfaces and can take the place of conventional wet cleaning processes such as ultrasonic cleaning with CFC and other organic solvents. The mechanisms of laser cleaning may include laser photodecomposition, laser ablation and surface vibration due to the impact of laser pulse.
Preparation of Pyroelectric Pb1-xLaxTi1-x/4O3 Thin Films from Ceramic Target by RF Magnetron Sputtering
Authors: Komaki Kazuki , Kamada Takeshi , Hayashi Shigenori , Kitagawa Masatoshi , Takayama Ryoichi , Takashi Hirao Takashi Hirao
Published: October 2002

Pyroelectric Pb1-
x

La

x

Ti1-
x
/4O3 thin films of high quality have been obtained reproducibly by rf magnetron sputtering using a ceramic target. The effects of sputtering parameters on film composition and structure have been studied and related to plasma emission spectroscopy. By controlling the relative intensities of Pb* (406 nm) and Ti* (396 nm) emissions of the plasma, the sputtering conditions were optimized to produce stoichiometric and highly c-axis-oriented filins. Under stabilized conditions, use of the ceramic target offered stability of the plasma and a high deposition rate of 2 Å/s. The PLT film exhibited good pyroelectric parameters with a dielectric constant of 290 and a pyroelectric coefficient of 4.2×10-8 C/cm2· K.
Growth Condition Dependence of Carbon Reduction in GaAs Chemical Beam Epitaxy Using Trisdimethylamino-Arsine and Trimethylgallium
Authors: Ishikura Kouji , Takeuchi Atsushi , Kurihara Megumu , Machida Hideaki , Fumio Hasegawa Fumio Hasegawa
Published: October 2002

It was found that carbon incorporation in GaAs chemical beam epitaxy (CBE) using trisdimethylamino-arsine (TDMAAs) and trimethylgallium (TMGa) strongly depends on the V/III ratio and the cracking temperature of TDMAAs. Although a high concentration of carbon was incorporated for the growth with low V/III ratio, the carbon concentration was reduced to the order of 1016 cm-3 at high V/III ratios. For the layer grown using TDMAAs precracked at 550° C by a cracker cell, the carbon concentration was above 1019 cm-3. These results suggest that arsenic-dimethylamine (DMA) bonds rather than DMA itself play an important role in the carbon gettering mechanism.
Scanning Tunneling Microscopic Study on the Initial Growth of Bi2Sr2CuO6 Thin Films on SrTiO3(001) by Laser Molecular Beam Epitaxy
Authors: Koguchi Kazumasa , Matsumoto Takuya , Tomoji Kawai Tomoji Kawai , Shichio Kawai Shichio Kawai
Published: October 2002

The initial growth mechanism of Bi2Sr2CuO6 thin films has been studied using scanning tunneling microscopy (STM) and reflection high-energy electron diffraction (RHEED) on c-axis oriented ultrathin films prepared by laser molecular beam epitaxy (MBE). Layered growth films show an atomically flat surface with 0.4 nm height steps, suggesting the existence of an extra BiO layer on the topmost surface. The modulation structure strongly affects growth direction in the a-b plane. Preferential growth occurs along the modulation-free a-axis. Comparison has been made between STM images and RHEED patterns during the growth.
Magnetic and Magnetoresistive Modification on Granular Co–Ag Films by Soft Magnetic Permalloy Layer
Authors: Kume Minoru , Maeda Atsushi , Satoru Oikawa Satoru Oikawa , Kazuhiko Kuroki Kazuhiko Kuroki
Published: October 2002

Double-layered structure which is composed of permalloy and granular Co–Ag thin layers has been fabricated by successive sputtering method. Their magnetic and magnetoresistive (MR) characteristics have been studied as a function of the Co–Ag/permalloy thickness ratio. The coercive force decreases with increasing the permalloy layer thickness, indicating the presence of an interlayer magnetic coupling. However, the magnetic saturation field associated with the MR characteristics is maintained to be extremely high. The MR ratios of some double-layered films are larger than that of the Co–Ag single layer.
Linear and Nonlinear Operations of Optically Addressed Spatial Light Modulators Using Antiferroelectric Liquid Crystal
Authors: Masuda Taro , Oyama Tsuyoshi , Hamada Shouji , Takahashi N. Shinichi , Kawamura Ichiro , Hagiwara Takashi
Published: October 2002

A new spatial light modulator using antiferroelectric liquid crystal and amorphous silicon photosensor is presented. This spatial light modulator realizes real-time optical information processing by applying high-frequency voltage to the device. By changing the driving frequency, we have achieved both linear and nonlinear operations with a single device.
Heteroepitaxial Growth of Quaternary BaxSr1-xTiO3 Thin Films by ArF Excimer Laser Ablation
Authors: Hitoshi Kobayashi Hitoshi Kobayashi , Takeshi Kobayashi Takeshi Kobayashi
Published: October 2002

Highly polarizable Ba

x

Sr1-
x

TiO3 (x=0∼1) (BSTO) thin films have been grown heteroepitaxially by the ArF excimer laser ablation method. They were characterized by X-ray diffraction, reflection high-energy electron diffraction (RHEED), capacitance-voltage (C-V), Fourier transform infrared (FTIR) and UV spectroscopic measurements, and x-dependent properties were studied systematically. The dielectric properties of the epitaxial BSTO films were consistent with data from ceramic bulk. However, the optical probes (FTIR and UV spectrometry) indicated the occurrence of microscopic composition fluctuation in the quaternary systems.
Design of a New Type of Variable-Frequency Radio-Frequency Quadrupole Linac with a Folded-Coaxial Resonator
Authors: Kamigaito Osamu , Goto Akira , Miyazawa Yoshitoshi , Chiba Toshiya , Hemmi Masatake , Masayuki Kase Masayuki Kase , Yasushige Yano Yasushige Yano
Published: October 2002

A new type of variable-frequency radio-frequency quadrupole (RFQ) linac that will be constructed as a new injector for the RIKEN heavy-ion linac (RILAC) is proposed. It is designed to accelerate ions with mass-to-charge ratios of 7 to 28 at up to 450 keV per charge by varying its operational frequency from 17 to 35 MHz. The resonator has a folded-coaxial structure, and the resonant frequency is changed by a movable shorting plate. As a result of a low-power test on a half-scale model, the required rf power is found to be 6 kW at 17 MHz, and it increases to 34 kW at 35 MHz in cw operation.
Photovoltaic Effect of Bilayer Solid-State Cell with Polysiloxane Pendant Tris( 2,2′-bipyridyl)ruthenium Complex
Authors: Yamada Katsumi , Kobayashi Norihisa , Ikeda Koji , Hirohashi Ryo , Kaneko Masao
Published: October 2002

A solid-state photoelectrochemical device was fabricated with a poly-siloxane pendant tris(2,2'-bipyridyl)ruthenium complex [ PSiO–Ru(bpy)3
2+] as a photosensitizer layer and a polysiloxane pendant methylviologen [ PSiO–MV2+] as an electron acceptor layer. In the dark, the SnO2/PSiO–MV2+/PSiO–Ru(bpy)3
2+/Ag solid-state cell showed rectification characteristics. Photocurrent was obtained in the bilayer solid-state cell upon illumination of visible light, which was caused by the photoexcitation of the Ru(bpy)3
2+ and successive electron transfer to the MV2+. The short-circuit photocurrent of 0.485 µ A· cm-2 was obtained with the intensity of illumination of 34 mW· cm-2.
Reflection-Resonance-Type Photon Scanning Tunneling Microscope
Authors: Jiang Shudong , Nakagawa Ken'ichi , Ohtsu Motoichi
Published: October 2002

A novel reflection-resonance-type photon scanning tunneling microscope is proposed to measure the sub-wavelength sample profile by detecting the resonant frequency shifts of a probe cavity. Simulation experiments were carried out to confirm the effectiveness of the present proposal and the theoretical estimation shows that the shot-noise-limited lateral resolution as high as 2.3×10-3λ can be expected.
Submicrometer Gold Interconnect Wiring by Sidewall Electroplating Technology
Authors: Hirano Makoto , Shinji Aoyama Shinji Aoyama , Kimiyoshi Yamasaki Kimiyoshi Yamasaki
Published: October 2002

A novel technique for forming submicrometer gold wires is proposed to realize high-density interconnection in LSIs. The wires are fabricated into a structure which is buried in an insulator spacer using sidewall electroplating technology. Optimum plating conditions are studied to achieve good metaling conformability and uniformity. By optimizing the plating conditions, gold interconnect wires with submicrometer linewidth and spacing are formed with good surface planarity of the buried structure.
Crude Estimates of Diffusivity and Supersaturation of Silicon Self-Interstitials Injected by Thermal Oxidation of Czochralski Silicon
Authors: Hideki Yamanaka Hideki Yamanaka , Yoshihira Aoki Yoshihira Aoki
Published: October 2002

A new approach based on the classical nucleation theory has been provided to estimate the diffusivity and the supersaturation of silicon self-interstitials ( I
S
i
). I
S
i
injected through thermal oxidation at 1000°C is found to reach the half-depth of the 650-µm-thick wafer within 3 min. This finding is confirmed by the observation of the depth profiles of oxygen precipitates in the wafer subjected to rapid thermal annealing at 1000°C in O2 for up to 5 min. The diffusivity of I
S
i
and the supersaturation of I
S
i
reaching the half-depth of the 650-µm-thick wafers after 3 min during oxidation at 1000°C are estimated to be 5.9×10-6 cm2/s and about 6, respectively.
In Situ Observation of Monolayer Steps during Molecular Beam Epitaxy of Gallium Arsenide by Scanning Electron Microscopy
Authors: Homma Yoshikazu , Osaka Jiro , Inoue Naohisa
Published: October 2002

We have applied scanning electron microscopy (SEM) for in situ observation of molecular beam epitaxy (MBE) of GaAs. Monolayer steps on a GaAs (001) surface are imaged by secondary electrons during MBE growth. The step structure change is observed between the step-bunched surface during growth interruption and the monolayer-stepped surface during growth.
Observation of Distinct Metallic Conductivity in NaCo2O4
Authors: Tanaka Tomoaki , Shin Nakamura Shin Nakamura , Shuichi Iida Shuichi Iida
Published: October 2002

Electrical conductivity and powder X-ray studies have been made on (Sr1-αNa[α])CoO

x

after firing at 980°C in air. The data are explainable in terms of the mixed phase of SrCoO

x

(x∼2.5) and NaCo2O4. We found a distinct metallic conductivity in NaCo2O4; the resistivity decreases linearly to 12 K from room temperature. This compound may be another candidate mother oxide for future study of high-temperature superconductivity.
Characterization and Oxygen-Sensing at Polycrystalline Copper-Dicyanoanthraquinone Diimines
Authors: Cheng Hwang Yaw , Chong Mou Wang Chong Mou Wang , Lilian Kao Liu Lilian Kao Liu
Published: October 2002

A series of substituted dicyanoanthraquinone diimines (DCNAQI) and related copper complexes were synthesized and characterized. These materials behaved like semiconductor and showed strong absorption in the IR region. With bandgap excitation, the photoconductances measured at these copper-DCNAQI complexes revealed a nearly linear relationship with the partial pressure of oxygen atmosphere. This remarkable relationship might be attributed to the retardation of the electron mobility caused by the interaction between the electron and oxygen adsorbed at the Cu-DCNAQI surface.
Determination of Surface Chemical Species in GaAs Atomic Layer Epitaxy by In Situ Gravimetric Monitoring
Authors: Koukitu Akinori , Takahashi Naoyuki , Yoshiki Miura Yoshiki Miura , Hisashi Seki Hisashi Seki
Published: October 2002

Atomic layer epitaxy (ALE) using a GaCl source is investigated by a real-time in situ gravimetric monitoring method. An ALE system with an electrobalance is used as a monitoring system. The direct gravimetric information from the growing surface in the growth system of ALE is monitored during an ALE cycle. It is shown that the surface chemical species are one-monolayer Ga atoms during H2 purge after GaCl supply, and the in situ gravimetric method is a powerful tool for the investigation of the ALE growth mechanism.
High-Rate Selective Etching of a-Si:H Using Hydrogen Radicals
Authors: Nagayoshi Hiroshi , Yamaguchi Misako , Kamisako Koichi , Tarui Takashi Horigome
Published: October 2002

A high-rate selective etching method of hydrogenated amorphous silicon (a-Si:H) using hydrogen radicals is presented. A very high etch rate of 2.7 µm/min was obtained at 50°C using a microwave hydrogen afterglow method. However, amorphous silicon nitride ( a-SiN1.2:H), silicon oxide ( SiO2), silicon carbide ( a-SiC0.5:H), and Al films were not etched under the same conditions. These results suggest that high-rate selective etching of a-Si:H can be achieved using hydrogen radicals. This method is suitable for the fabrication of large-area devices.
Fabrication and Evaluation of Superconducting Quantum Interference Devices with Nb/Al–AlOx–Al/Nb Edge Junctions
Authors: Mizutani Naoki , Yamasaki Shuichi , Takada Youichi , Adachi Akira , Kado Gen Uehara
Published: October 2002

We have fabricated superconducting quantum interference devices (SQUIDs) with an inductance of 140 pH by using sub- µm Nb/Al–AlO

x

–Al/Nb edge junctions. The small capacitance of the junction resulted in the very large voltage swing of 210 µV and gradient dV/ dΦ of 940 µV/Φ0. Consequently, the very low flux noise of 0.61 µΦ0/ Hz0.5 corresponding to the energy sensitivity ε of 8.6h at the white noise level was obtained by using a conventional flux-locked loop configuration. The low-frequency noise was also very low, 2.7 µΦ0/ Hz0.5 corresponding to ε= 170 h at 1 Hz. We could obtain very low flux noise for the SQUID which had the practical inductance using only a conventional readout circuit.
Violet and Blue Light Emissions from Nanocrystalline Silicon Thin Films
Authors: Zhao Xinwei , Schoenfeld Olaf , Kusano Junichi , Yoshinobu Aoyagi Yoshinobu Aoyagi , Takuo Sugano Takuo Sugano
Published: October 2002

Nanocrystalline silicon thin films with a grain diameter from three to seven nanometers were fabricated on silicon substrates. It is demonstrated for the first time that the thin films show intense violet and blue luminescence at room temperature. The luminescence spectra include three peaks at wavelengths of 415 nm, 437 nm and 465 nm. Anodizations of these thin films introduce additional green and red luminescence in the spectra. Fourier transform infrared spectroscopy indicates no hydrogen- or oxygen-related absorptions in the nanocrystalline silicon thin films. Only the anodized thin films show Si–H

x

absorptions. The violet luminescence should be evidence of light emission from zero-dimensionally confined silicon structures.
Time Variation of Surface Temperature during Electron Beam Evaporation
Authors: Ohba Hironori , Araki Masanori , Takemasa Shibata Takemasa Shibata
Published: October 2002

Time variation of the surface temperature of copper during electron beam evaporation was measured with a high-speed infrared thermometer. The periodic variation of the surface temperature was observed with the frequency of 100 Hz, which was synchronized with the relative atomic beam density measured by a mass spectrometer. Moreover, the fluctuation of the atomic beam density was consistent with that estimated from the surface temperature variation. It was found that the fluctuation in the atomic beam density depended on the periodic variation of the surface temperature.
Surface Preparation Effects for Molecular Beam Epitaxial Growth of ZnSe Layers on InGaP Layers
Authors: Saito Shinji , Nishikawa Yukie , Onomura Masaaki , Parbrook Peter J. , Masayuki Ishikawa Masayuki Ishikawa , Genichi Hatakoshi Genichi Hatakoshi
Published: October 2002

The effect of InGaP surface preparation has been investigated for the molecular beam epitaxial (MBE) growth of ZnSe. The net acceptor concentration profile near the interface of nitrogen-doped p-type ZnSe layers was strongly affected by the surface preparation of InGaP layers. The low net acceptor concentration region for the samples grown on a thermally treated (580°C) or P2S5-treated InGaP surface was narrower than that region for the sample grown on a surface exposed to neither thermal treatment nor P2S5 treatment. Structures with InGaP buffer layers exposed to the surface treatments outlined here hold much promise for the reduction of the blue-green laser operation voltage.
High Efficiency GaAs/Si Monolithic Three-Terminal Cascade Solar Cells Grown by Metal-Organic Chemical Vapor Deposition
Authors: Yang Mingju , Soga Tetsuo , Egawa Takashi , Jimbo Takashi , Masayoshi Umeno Masayoshi Umeno
Published: October 2002

A high-efficiency GaAs/Si monolithic three-terminal cascade solar cell is proposed and fabricated by the metal-organic chemical vapor deposition (MOCVD) method and thermal diffusion method. The quantum efficiency in the long wavelength region was improved by using p-Si substrates with the resistivity of 10 Ω ·cm as the Si bottom cells. Adopting a graded band-gap layer (GBL) of Al

x

Ga1-
x

As, the collection efficiency of the GaAs top cell was increased considerably. A total conversion efficiency of 19.1% was achieved at the AM0 condition for the GaAs/Si three-terminal cascade solar cell.
In Situ Deposition of YBCO Thin Films by Sputtering under Low Oxygen Partial Pressure
Authors: Park Yong Ki , Park Keunseop , Lee Soon-Gul , Shin Dong Chan , Jong-Chul Park Jong-Chul Park
Published: October 2002

Y–Ba–Cu–O superconducting thin film was grown on the SrTiO3 substrate by in situ 90°-off-axis rf magnetron sputtering under the low oxygen partial pressure of 0.67 Pa (5 mTorr) from different targets with various Ba/Y ratios. All films were grown at 645°C with their c-axis normal to the substrate surface. The critical temperature and c-axis length approached the optimum values as the Ba/Y ratio of the target decreased from 2 to 1. In addition, the effect of the oxygen pressure during cooling after deposition on the critical temperature and the c-axis length of the thin films was determined.
Preparation of Al–Pd–Mn Quasicrystal Films by Laser Ablation Method
Authors: Ichikawa Norio , Matsumoto Osamu , Hara Tsutomu , Kitahara Tadashi , Yamauchi Toshihiko , Matsuda Takeshi , Takeuchi Tsunehiro , Mizutani Uichiro
Published: October 2002

Al–Pd–Mn quasicrystal thin films were prepared by KrF excimer laser ablation for the first time, to our knowledge. The thin films were obtained only when the substrate temperature was lowered to liquid nitrogen temperatures during ablation. The composition of the films was found to agree with that of the target material within a few percent, regardless of the substrate temperature in the rang from -196°C to 300°C.
Spatial Distributions of Densely Contact-Electrified Charges on a Thin Silicon Oxide
Authors: Sugawara Yasuhiro , Morita Seizo , Fukano Yoshinobu , Uchihashi Takayuki , Okusako Takahiro , Chayahara Ayumi , Yamanishi Yoshiki , Oasa Takahiko
Published: October 2002

The spatial distributions of densely contact-electrified charges on silicon oxide were investigated in air with an atomic force microscope. We found that the spatial distributions immediately after contact electrification significantly depended on the sign of the charge. The spatial distributions showed sharp peaks for positive charge but round peaks for negative charge. We conjectured that the sign dependence of the spatial distributions was induced by the forced tunneling process. We also found the other feature of the spatial distributions of the dissipated charge, which seemed to be related to premonitory phenomena of dielectric breakdown for silicon oxide.
Quantitative Analysis of Oxygen Deficiency in Epitaxial CeO2 Layers on Si by Detecting 18O Added for Stoichiometry
Authors: Tomoyasu Inoue Tomoyasu Inoue , Yasuhiro Yamamoto Yasuhiro Yamamoto , Masataka Satoh Masataka Satoh , Takahiro Hoshi Takahiro Hoshi , Kenji Miyoshi Kenji Miyoshi
Published: October 2002

Oxygen deficiency in epitaxially grown CeO2 layers on Si substrates by ultrahigh-vacuum evaporation is studied using secondary ion mass spectrometry (SIMS). 18O2 gas is externally introduced in the evaporation process for compensation of oxygen deficiency of the CeO2 layer. Oxygen components in CeO2 layers are analyzed, separately detecting secondary ions of Cs16O+ and Cs18O+. The extrinsic oxygen content needed to obtain stoichiometric CeO2 is determined to be in the range of 11–18%. These SIMS data agree well with the oxygen deficiency of ∼18% determined by Rutherford backscattering analysis of a nonstoichiometric CeO2 layer grown without oxygen gas introduction.
Optoelectronic Phase-Tracking and Waveform Display of Microwave Signals up to 8 GHz Using Gain-Switched Laser Diodes
Authors: Wu Hsiao-Hua , Wang Chi-Luen , Lin Gong-Ru , Chang C.-S. , Ci-Ling Pan Ci-Ling Pan
Published: October 2002

We present a new, more versatile scheme for maintaining phase coherence between optical probe pulses and microwave signals under test in a laser-diode-based optoelectronic sampling system. This approach takes advantage of the relative ease of changing the repetition rate of the gain-switched laser diode (GSLD). The microwave signal to be sampled is used as the clock signal for phase-locking of a voltage controlled-oscillator (VCO) which drives the GSLD. Phase-tracking and display of waveforms at frequencies up to 8 GHz have been realized. It is also shown that lower phase noise sidebands for the phase-locked VCO can be realized by locking the higher harmonics of the laser pulse to the microwave clock.
Possibility of Analyzing the Type of Impurities in Semiconductors by Application of Bistability in Luminescence
Authors: Ullrich Bruno , Misawa Kazuhiko , Kobayashi Takayoshi , Kazlauskas Arunas , Cong Hoan Nguyen , Chartier Pierre
Published: October 2002

Besides the well-known phenomenon of bistability in transmission, the excitation of thin ( 5.5 µm) CdS films by the 514.5 nm A
r
+-laser line generates all-optical bistability in luminescence in the near-infrared region of the spectrum. With the application of this feature, the determination of the type of impurities, donors or acceptors in GaAs is possible. The novel method proposed here underlies the principle that differently contrasting bistable loops in luminescence are clearly observed if n-type, intrinsic or p-type GaAs wafers are used as cut-off filters for the bistable luminescent emission of thin CdS films.
Type I/Type II Transition in InGaAlAs/InP Multiple Quantum Well Structures Grown by Gas Source Molecular Beam Epitaxy
Authors: Kawamura Yuichi , Hideki Kobayashi Hideki Kobayashi , Hidetoshi Iwamura Hidetoshi Iwamura
Published: October 2002

In0.52Ga0.48-yAlyAs/InP multiple quantum well (MQW) structures are grown by gas source molecular beam epitaxy (GS-MBE). It is found that a transition from type I to type II structure occurs at an Al composiaon (y) of 0.18, accompanied by a drastic change of optical and electrical properties. Theydependence of the effective band gap of the InGaAlAs/InP MQW layers agrees well with the calculated result.
Improvement of Gate-Insulator/Silicon Interface Characteristics in Amorphous Silicon Thin Film Transistors
Authors: Sameshima Toshiyuki , Kohno Atsusi , Sekiya Mitsunobu , Masaki Hara Masaki Hara , Naoki Sano Naoki Sano
Published: October 2002

N-channel Al-top gate type amorphous silicon thin film transistors (a-Si TFTs) were fabricated with an SiO2 gate oxide, never exceeding a substrate temperature of 250° C. A reactive evaporation of SiO powder in an oxygen atmosphere with a flow rate of 2 sccm at a pressure of 1×10-4,Torr was used for forming a good quality interface of SiO2/a-Si. The a-Si TFTs showed characteristics of a low threshold voltage of 0.86 V, a moderate carrier mobility of 1.1 cm2/V· s and a subs-threshold slope of 0.12 V/decade. These characteristics result from a good SiO2/a-Si interface with a density of trapping states of 1.6×1011 cm-2·eV-1.
Epitaxial Growth of Aluminum Films on Hydrogen-Mediated Si(100) Surface
Authors: Hideo Sugawara Hideo Sugawara , Kazuyuki Ueda Kazuyuki Ueda
Published: October 2002

Epitaxial growth of Al film on hydrogen-terminated Si(100) has been studied using LEED-Auger analysis. Characteristics of hydrogen adsorption were studied in a separate experimental chamber by using a time-of-flight-type electron-stimulated desorption spectroscopy. As a result of weakening of Al–Si bonding by hydrogen termination of dangling bonds, the growth mode of the Al film changed to the Volmer-Weber mode from the Stransky-Krastanov mode in the conventional case, and metal-like character appeared in the AES spectrum. Particularly in LEED observation, an epitaxial structure of the Al film in the H/Si(100) system was observed with an orientation of Al(111).
Characteristics of a Large-Bore Copper Vapor Laser with Gas-Cooling Plates
Authors: Yasushi Iseki Yasushi Iseki , Kazuo Hayashi Kazuo Hayashi , Ikuo Watanabe Ikuo Watanabe , Etsuo Noda Etsuo Noda , Setsuo Suzuki Setsuo Suzuki
Published: October 2002

It has been experimentally found that the insertion of plates into the plasma tube has improved the output characteristics of an 80-mm copper vapor laser. It has been revealed that the buffer gas temperature decreases and the metastable-state (the lower laser level) density of copper atoms decreases near the center axis of the plasma tube. Moreover, electric power is transferred into plasma more efficiently because of the increase in plasma impedance. As a result, the average output power is increased by 57 % and the beam intensity profile has become uniform.
A Flat Panel Display Combining a Polymer-Dispersed Liquid Crystal Film with an Electroluminescent Device
Authors: Fuh Andy Ying-Guey , Huang Chi-Yen , Sheu Chi-Ren , Gen-Lan Lin Gen-Lan Lin , Ming-Shann Tsai Ming-Shann Tsai
Published: October 2002

A novel display device combining a polymer-dispersed liquid crystal (PDLC) film and a thin-film electroluminescent (TFEL) device was fabricated. This device may be used as a liquid crystal display (LCD) in strong light ambient. In the dark, it can be switched to become an electroluminescent display, providing high viewability. Measurements of its electrooptical characteristics showed that the breakdown voltage of the TFEL device did not change significantly with the addition of a LC layer. It implies that the cured polymer could provide an intrinsic barrier preventing LC material from diffusing into the TFEL device.
Anisotropic Optical Matrix Elements in Quantum Wells with Various Substrate Orientations
Authors: Yamaguchi A. Atsushi , Nishi Kenichi , Akira Usui Akira Usui
Published: October 2002

Optical matrix elements and in-plane hole effective masses in quantum wells (QWs) are investigated theoretically as functions of substrate orientation. Calculations are performed for GaAs QWs which orient to an arbitrary direction in a (11̄0) plane. It is found that large optical anisotropy appears in (211) QWs as well as in (110) QWs. The advantages of the (211) QWs for low-threshold lasers are discussed.
Reduction of Radiation-Induced Degradation in n-Channel Metal-Oxide-Semiconductor Field-Effect Transistors (MOSFET's) with Gate Oxides Prepared by Repeated Rapid Thermal N2O Annealing
Authors: Wu You-Lin , Kang-Min Kuo Kang-Min Kuo , Jenn-Gwo Hwu Jenn-Gwo Hwu
Published: October 2002

Repeated rapid thermal N2O annealing is proposed as a new gate oxide preparation method for n-channel metal-oxide-semiconductor field-effect transistors (n-MOSFET's). It is found that the n-MOSFET's with gate oxide prepared by this method exhibit higher field-effect mobility and better radiation hardness when compared with those with fresh and the conventional one-time N2O-annealed gate oxides.
Electric Field Effects on YBa2Cu3O7-δ Grain Boundary Josephson Junctions
Authors: Nakajima Kensuke , Yokota Kazuki , Chen Jian , Hiroaki Myoren Hiroaki Myoren , Tsutomu Yamashita Tsutomu Yamashita
Published: October 2002

Various effects of the electric field on YBa2Cu3O7-δ grain boundary Josephson junctions were studied using inverted metal-insulator-superconductor (MIS) samples which employed bicrystal SrTiO3 substrates as insulators. The critical cutrents, I
c of the junctions were regulated by gate voltages with the field-induced changes in charge carrier densities. Furthermore, a significant field effect on equidistant step structures observed in I-V curves was found. The equidistant steps can be ascribed to self-resonances of the ac Josephson current in the grain boundary junctions. The gate voltages shifted the step voltages corresponding to resonance frequencies of the grain boundary toward high voltages. This appears to be a consequence of the field dependence of dielectric properties of grain boundary junctions.
ZnCdSe/ZnSSe/ZnMgSSe SCH Laser Diode with a GaAs Buffer Layer
Authors: Itoh Satoshi , Nakayama Norikazu , Matsumoto Satoshi , Nagai Masaharu , Nakano Kazushi , Ozawa Masafumi , Okuyama Hiroyuki , Tomiya Shigetaka , Ohata Toyoharu , Ikeda Masao , Akira Ishibashi Akira Ishibashi , Yoshifumi Mori Yoshifumi Mori
Published: October 2002

Blue-green laser diodes exhibiting continuous-wave operation during hundreds-of-seconds have been fabricated. This structure is a ZnCdSe/ZnSSe/ZnMgSSe separate-confinement heterostructure with low dislocation density of ∼105 cm-2 in the n-ZnMgSSe cladding layer. The use of a GaAs buffer layer has lead to the decrease of dislocation density for laser-diodes, with which we have observed CW operation up to 80° C, that showed the feasibility of ZnCdSe/ZnSSe/ZnMgSSe SCH laser-diodes.
Growth of Low-Resistivity n-Type ZnTe by Metalorganic Vapor Phase Epitaxy
Authors: Ogawa Hiroshi , Irfan Gheyas Syed , Nakayama Hitoshi , Nishio Mitsuhiro , Yoshida Akira
Published: October 2002

Doping of ZnTe has been carried out by metalorganic vapor phase epitaxy using triethylaluminum as the dopant source. N-type ZnTe layers with a carrier concentration of (1–4) ×1017cm-3and a resistivity as low as 0.1–0.3 Ω·cm have been obtained. It has been indicated by the photoluminescence measurement that Al is incorporated effectively into the epitaxial layer.
Estimation of Critical Current Density in a Melt-Processed Superconducting Y-Ba-Cu-O Using AC and DC Inductive Methods
Authors: Edmund Soji Otabe Edmund Soji Otabe , Nozomu Ohtani Nozomu Ohtani , Teruo Matsushita Teruo Matsushita , Yuichi Ishikawa Yuichi Ishikawa , Shuji Yoshizawa Shuji Yoshizawa
Published: October 2002

The local and transport critical current densities in a melt-processed Y-Ba-Cu-O were estimated by analyzing the results of the Campbell method and DC magnetization measurement in terms of the Campbell model in which the reversible fluxoid motion is treated. The factor of overestimation of the local current density was evaluated from the slope of minor DC magnetization curve. The obtained local critical current density was about one order of magnitude larger than the transport critical current density and was comparable to a theoretical value where normal particles of the 211 phase are assumed to act as dominant pinning centers.
Characteristics of the Oxidation Barrier Layers for Copper Metallization
Authors: Lee Kyung-Il , Min Kyung-Ik , Joo Seung-Ki , Rha Kwan-Gu , Woo-Shik Kim Woo-Shik Kim
Published: October 2002

Characteristics of the oxidation barrier layers for copper metallization were investigated. Thin films of Cr, TiN and Al were used as the oxidation barrier layers for Cu. Ultrathin Al film was found to prevent the oxidation of Cu up to the highest annealing temperature (600° C) among the barriers layers tested in this study. Topographical features of Cu\Al film were better than those of Cu\Cr and Cu\TiN after an oxidation annealing treatment. It was found that oxygen did not diffuse into Cu because of the ultrathin Al2O3 layer formed on the Cu surface, and consequently ultra thin (25 Å) Al film could be a good oxidation barrier layer for Cu metallization.
Studies of Corrosive Outgasses from Via Holes Using Thermal Desorption Spectroscopy
Authors: Tokitoh Shunichi , Uchida Hidetsugu , Uchida Hiroaki , Okuno Yasuyuki , Fushimi Kimihisa , Liu Guo-Lin , Sakaya Yoshihiro , Norio Hirashita Norio Hirashita
Published: October 2002

This work reveals the presence of corrosive outgassing from via holes in multiinterdielectric structures with inorganic spin-on-glass (SOG) films using thermal desorption spectroscopy. Main species of the corrosive outgassing are found to be H2O, NH3 and HF.
The amount of NH3 desorption reaches 5-10% of water desorption. Significant amounts of H2O and NH3 are found to be desorbed from the SOG films. The desorption of NH3 results from occlusion of the species into the SOG film through the via holes.
Novel Pulse-Mode Neural Circuits Based on an AlGaAs-GaAs Multi-Quantum Well Diode
Authors: P. Roenker Chung-Kun Song
Published: October 2002

A novel approach to the hardware implementation of artificial, electronic pulse-mode neural circuits is described based on a new compound semiconductor device called a multi-quantum well injection mode device (MQW-IMD). The device exhibits a novel s-type current- voltage characteristic which has been theoretically modeled and experimentally verified. When operated with an resistance-capacitance (RC) load, the device switches periodically between the low conductance off state and high conductance on state generating a pulse mode output. The operation is analogous to that of the axon hillock or trigger zone of the neuron, exhibiting a threshold behavior and a nonlinear (exponential-like) dependence of the pulse frequency on the input voltage (mean membrane potential). Electronic synapses are proposed for accepting pulse-mode inputs, with both excitatory and inhibitory inputs possible. Signal integration over multiple inputs is shown to be feasible with individual synaptic weighting. Operation is shown to be possible at low voltages and powers with pulse amplitudes comparable to and pulse frequencies equal to or larger than its biological counterpart. This paper will focus on the neural-like characteristics of circuits based on this novel MQW-IMD diode.
Stand-Alone Hardware-Based Learning System
Authors: Ng Trevor Clarkson
Published: October 2002

The probabilistic Random Access Memory (pRAM) is a biologically-inspired model of a neuron. The pRAM behaviour is described in this paper in relation to binary and real-valued input vectors. The pRAM is hardware-realisable, as is its reinforcement training algorithm. The pRAM model may be applied to a wide range of artificial neural network applications, many of which are classification tasks. The application presented here is a control problem where an inverted pendulum, mounted on a cart, is to be balanced. The solution to this problem using the pRAM-256, a VLSI pRAM controller, is shown.