bluuebunny/crossref_metadata_2025 huggingface dataset:
Photoluminescence from Reactive Deposition Epitaxy (RDE) Grown β-FeSi 2 Balls Embedded in Si Crystals
Authors: Takashi Suemasu Takashi Suemasu , Tetsuo Fujii Tetsuo Fujii , Yuusuke Iikura Yuusuke Iikura , Ken'ichiro Takakura Ken'ichiro Takakura , Fumio Hasegawa Fumio Hasegawa
Published: October 2002

We report on the photoluminescence at around 1.5 µm from β-FeSi2 balls grown by reactive deposition epitaxy (RDE) and embedded in Si crystals for the first time.
The photoluminescence spectra depended on the size of the β-FeSi2 ball. We observed photoluminescence from the sample containing about 100-nm-diameter β-FeSi2 balls, but not from the samples
containing balls 50–70 nm and 150–200 nm in diameter.
This is because of the existence of nonradiative recombination centers due to a mixture of metallic α-FeSi2 for the former case, and of many dislocations induced by β-FeSi2 balls for the latter case.
Growth of Nanosize Ni Thin Films on a Modified c(2×2)-N Cu(100) Surface
Authors: Matsumoto Yuji , Tanaka Ken-ichi
Published: October 2002

Growth of Ni on a c(2×2)-N Cu(100) surface was studied by scanning tunneling microscopy (STM). When Ni atoms are vaporized on a Cu(100) surface with square c(2×2)-N patches, one-atomic-layer Ni islands with an average size of 50 Å are grown on the virgin area remaining at the corner of c(2×2)-N patches, so that uniform-size Ni islands are arranged like a checkerboard. This checkerboard arrangement of Ni islands is stable up to 470 K. Stronger interaction of the Ni layer with the clean area compared to the c(2×2)-N area brings about this unique growth of Ni islands on the c(2×2)-N Cu(100) surface.
Sub-Doppler Spectroscopy of Cs Atoms Optically Pumped in a Thin Cell
Authors: Tachikawa Maki , Fukuda Kyoya , Hayashi Shin'ichiro , Kawamura Tomoto
Published: October 2002

Optical pumping in a thin Cs vapor cell (end-wall gap 0.5–10 mm) transfers only atoms
with small velocity components to a certain energy state. The non-Maxwellian
velocity distribution is detected as a hyperfine-resolved spectrum by a double
resonance technique using diode lasers. The observed spectral profiles are
quantitatively reproduced by the rate-equation analysis in which the velocity-dependent
surface relaxation process is taken into account.
Formation of Nanostructures by Oxidation of Si at Low Temperature
Authors: Gin Nam Kyoung-Hwan Koo
Published: October 2002

Formation processes of Si nanostructures were investigated. The samples were formed by remote plasma enhanced chemical vapor deposition of Si and subsequent annealing in an oxidizing ambient at 560°C. It was found that the film structure of the annealed samples critically depends on the crystallinity of the as-deposited samples. Amorphous films resulted in dot formation when annealed, whereas grain agglomeration was observed in the case of crystalline films. In addition, the dots were embedded within SiO 2, whereas the agglomerated grains were isolated with no insulating material between them. These results were accounted for by taking into consideration the difference in kinetics involved during annealing.
Force Imaging of Optical Near-Field Using Noncontact Mode Atomic Force Microscopy
Authors: Masayuki Abe Masayuki Abe , Yasuhiro Sugawara Yasuhiro Sugawara , Yasuyuki Hara Yasuyuki Hara , Kazuyoshi Sawada Kazuyoshi Sawada , Seizo Morita Seizo Morita
Published: October 2002

We demonstrate a novel method to detect the van der Waals force gradient and the force gradient induced by the optical evanescent field on the surface, simultaneously, with high resolution. We use the noncontact mode atomic force microscopy (NC-AFM) with frequency modulation (FM) detection method, which can detect the force gradient with high sensitivity in a vacuum. The force gradient due to the evanescent field can be enhanced by applying the bias voltage. The 100-nm-diameter polystyrene latex spheres are observed with spatial resolution better than 50 nm (λ/14).
Density Control of GaSb/GaAs Self-assembled Quantum Dots (∼25nm) Grown by Molecular Beam Epitaxy
Authors: A. Hogg Kenji Suzuki , Koichi Tachibana Koichi Tachibana , Yasuhiko Arakawa Yasuhiko Arakawa
Published: October 2002

We report the realization of quantum-sized GaSb dots, of small diameter (∼25nm), on GaAs by molecular beam epitaxy in the Stranski-Krastanow growth mode. At the deposition of 3.1 mono-layer(ML) GaSb, the average diameter and height of GaSb quantum dot(QD) are 26 nm and 6.2 nm, respectively. In addition, the density control was systematically achieved between 2.6×109 to 1.2×1010cm-2 by carefully choosing the amount of GaSb deposited from 2.5 to 3.1ML. The growth mechanism are discussed in detail. These results are very useful in forming a QD of staggered band lineup (type-II) of possible use in novel device applications
Layered-Oxide-Isolation (LOXI) Metal-Semiconductor Field Effect Transistor (MESFET) for Low Parasitic Source-Drain Capacitance
Authors: Kodama Satoshi , Furuta Tomofumi , Kanda Atsushi , Muraguchi Masahiro , Ito Hiroshi , Ishibashi Tadao
Published: October 2002

We proposed and successfully fabricated a novel metal-semiconductor field effect transistor (MESFET) which is called as layered-oxide-isolation (LOXI) MESFET. In this structure, the channel is isolated from the semi-insulating (SI) GaAs substrate by a low dielectric constant (ε) material such as silicon dioxide. In order to realize this structure, we used a low-temperature wafer-bonding technique. Using this technique, it was possible for two 3-inch-diameter wafers to bond with each other at a temperature lower than 300°C. Thermal stability was kept at temperature higher than 420°C. In fabricated 0.5 µm-gate-length LOXI-MESFETs, transconductance g
m of 135 mS/mm, which is same as that for a conventional MESFET, and good pinch-off characteristics were obtained, demonstrating the feasibility of the fabrication process.
A Significant Reduction of Impurity Contents in Hydrogenated Microcrystalline Silicon Films for Increased Grain Size and Reduced Defect Density
Authors: Kamei Toshihiro , Kondo Michio , Matsuda Akihisa
Published: October 2002

We have prepared high-purity hydrogenated microcrystalline silicon films (µc-Si:H) on quartz substrates from a mixture of silane and hydrogen using a new type of ultrahigh vacuum plasma enhanced chemical vapor deposition system. In substrate temperatures ranging from 25 to 350°C, we have produced high-crystallinity µc-Si:H, as observed by Raman spectroscopy. At the highest temperature (∼350°C), we obtain larger crystalline Si grains, ∼1000 Å, estimated using Scherrer's formula. Transmission electron microscopy micrographs show that these crystalline grains are conical and extend 7000∼8000 Å in the film growth direction with a lateral size of ∼1000 Å. At a mid-range temperature (∼200°C), a spin density as low as ∼5×1015 cm-3 and the midgap position of the Fermi level imply a substantial reduction of the density of defects states in this pure film. Moreover, this pure film is stable against prolonged light exposure. Implications of these results for the role of impurities in the growth process and optoelectric properties of µc-Si:H are discussed.
Development of an Ultrashort-Pulse Reflectometer for Density Profile Measurements on GAMMA 10
Authors: Jr. Shigeyuki Kubota
Published: October 2002

An ultrashort-pulse reflectometer is under development for electron density profile and fluctuation measurements on the GAMMA 10 tandem mirror. At the heart of the system is an impulse generator which creates an 8 V, 65 ps full-width half-maximum pulse. Data was taken at the midplane of the GAMMA 10 central cell. The incident wave was launched with ordinary-mode polarization and frequency components of the reflected wave in the range 8–10 GHz were detected. The observed values of the time-of-flight are in rough agreement with those obtained from calculations using the Abel-inverted profile obtained from a 70 GHz microwave interferometer. These results suggest that the present system can be expanded to yield a reliable diagnostic for electron density profile measurements.
Reduction of Etch Pit Density in Organometallic Vapor Phase Epitaxy-Grown GaN on Sapphire by Insertion of a Low-Temperature-Deposited Buffer Layer between High-Temperature-Grown GaN
Authors: Iwaya Motoaki , Takeuchi Tetsuya , Yamaguchi Shigeo , Wetzel Christian , Amano Hiroshi , Akasaki Isamu
Published: October 2002

The etch pit density of organometallic vapor phase epitaxy (OMVPE)-grown GaN on sapphire was discovered to reduce drastically by the insertion of either a low-temperature-deposited AlN buffer layer or GaN buffer layer between high-temperature-grown-GaN on sapphire.
Numerical Analysis of Ar2
* Excimer Production in Laser-Produced Plasmas
Authors: Takahashi Akihiko , Okada Tatsuo
Published: October 2002

In this letter, we investigate the production of high-density Ar2
* excimer in the plasma produced by an intense laser field for the generation of coherent vacuum ultraviolet (VUV) radiation. The kinetics of high-pressure Ar gas irradiated by CO2 laser are analyzed using a simulation model which consists of the Boltzmann equation and rate equations. The calculated density of Ar2
*(1Σu
+) excimer is 7×1022 m-3 under a pressure of 20 atm irradiated by CO2 laser with an intensity of 1.4×1012 W/m2, which corresponds to the unit gain of 60 m-1.
Direct Evidence that Dislocations are Non-Radiative Recombination Centers in GaN
Authors: Sugahara Tomoya , Sato Hisao , Hao Maosheng , Naoi Yoshiki , Kurai Satoshi , Tottori Satoru , Yamashita Kenji , Nishino Katsushi , Romano Linda T. , Sakai Shiro
Published: October 2002

Plan-view transmission electron microscopy (TEM) and cathodoluminescence (CL) images were taken for the same sample at exactly the same location in n-type GaN grown on sapphire substrate by metalorganic chemical vapor deposition (MOCVD). There was a clear one to one correspondence between the dark spots observed in CL images and the dislocations in TEM foils, indicating that the dislocations are non-radiative recombination centers. The hole diffusion length in n-type GaN was estimated to be neighboring 50 nm by comparing the diameters of the dark spots in thick samples used for CL and samples that were thinned for TEM observation. The efficiency of light emission is high as long as the minority carrier diffusion length is shorter than the dislocation spacing.
Diffusion Barrier Characteristics of Hf(C,N) Thin Films Deposited by Plasma Enhanced Metal Organic Chemical Vapor Deposition for Cu Metallization
Authors: Woo-Cheol Roh Woo-Cheol Roh , Donggeun Jung Donggeun Jung
Published: October 2002

Diffusion barrier characteristics of Hf(C,N) thin films for Cu metallization was investigated. Hf(C,N) thin films were deposited on Si(100) substrates by pulsed D.C. plasma enhanced metal-organic chemical vapor deposition (PE-MOCVD) using tetrakis diethyl amido hafnium (Hf[N(C2H5)2]4 : TDEAHf) and N2 as precursors. X-ray diffraction analyses, sheet resistance measurements and Rutherford backscattering spectroscopy analyses revealed that Hf(C,N) films prevent diffusion of Cu fairly well up to 600°C. At 700°C, however, Hf(C,N) films allowed a significant diffusion of Cu into the Si substrate.
Two-Dimensional Measurement of Rotational Speed of a Diffuse Object Based on Laser Doppler Anemometry
Authors: Omori Ryota , Mita Go , Kawasaki Naoki , Suzuki Atsuyuki
Published: October 2002

A novel measurement method based on laser Doppler anemometry that determines the pure rotational speed of a diffuse object on the condition that its axis of rotation is in a plane perpendicular to the illuminating laser lights is described. The rotating object is illuminated by three parallel laser lights and its rotational speed is calculated from beat frequencies resulting from the mixing of their backscattered lights. To verify the principle, measurements of rotational speed of a brass cylinder were performed for rotational speeds in the range of 30–500 rpm. The measured values have a fairly good agreement with the preselected values over this range. The present method is useful for detection of rotational conditions of machinery components assembled in rotating or vibrating structures.
Enhancement of Selective Chemical Vapor Deposition of Copper by Nitrogen Plasma Pretreatment
Authors: Suk Kim Young , Joon Kim Dong , Kwak Sung Kwan , Kyu Kim Eun , Suk-Ki Min Suk-Ki Min , Donggeun Jung Donggeun Jung
Published: October 2002

Selective chemical vapor deposition of copper on TiN in the presence of borophosphosilicate glass (BPSG) was achieved by RF N2 plasma pretreatment. Without N2 plasma pretreatment, the copper films deposited on BPSG as well as TiN at the deposition temperature of 170°C, while N2 plasma treatment prior to copper deposition led to the significant suppression of the copper nucleation on BPSG. As the plasma pretreatment temperature was increased, the suppression of the copper nucleation on BPSG was increased. The results of time-of-flight secondary ion mass spectroscopy (TOF-SIMS) indicated that N2 plasma treatment decreased the content of hydroxyl groups on BPSG surface, suggesting that the reduction of the surface hydroxyl groups contributed to the selective deposition of copper on TiN/BPSG substrates.
Thermal Stability of Pt Bottom Electrodes for Ferroelectric Capacitors
Authors: Matsui Yuichi , Hiratani Masahiko , Kumagai Yukihiro , Miura Hideo , Fujisaki Yoshihisa
Published: October 2002

The stress of Pt films deposited at various temperatures and its correlation with the formation of hillocks during heat treatment were investigated. The residual stress changes from compressive to tensile as the deposition temperature increases. The compressive residual stress of a Pt film deposited at room temperature is initially relaxed by the shrinkage of the film thickness and then by hillock formation at a certain maximum compressive stress when the Pt film is heat-treated. On the other hand, Pt films deposited at higher temperatures (up to 500°C) have a high tensile residual stress. The Pt film maintains its smooth surface and no hillocks appear during the heat treatment at 500°C when the residual stress is tensile, since the threshold temperature at which hillocks form increases.
Intense-Proton-Beam Transport through an Insulator Beam Guide
Authors: Susumu Hanamori Susumu Hanamori , Shigeo Kawata Shigeo Kawata , Shigeru Kato Shigeru Kato , Takashi Kikuchi Takashi Kikuchi , Akira Fujita Akira Fujita , Yasunobu Chiba Yasunobu Chiba , Taisuke Hikita Taisuke Hikita
Published: October 2002

In this paper we study intense-proton-beam transport through an insulator guide. In our previous papers [Jpn. J. Appl. Phys. 34 (1995) L520, Jpn. J. Appl. Phys. 35 (1996) L1127] we proposed a new system for intense-electron-beam transport using an insulator guide. In contrast to the electron beam, an intense-proton beam tends to generate a virtual anode, because of the large proton mass. The virtual anode formation at the initial stage is prevented by prefilled plasma in this system. During and after this, electrons are extracted from the plasma generated at the insulator surface by the proton beam space charge and expand over the transport area. The proton beam charge is effectively neutralized by the electrons. Consequently, the proton beam propagates efficiently through the insulator beam guide. The electron extraction is self-regulated by the net space charge of the proton beam.
Reliability of GaN Metal Semiconductor Field-Effect Transistor at High Temperature
Authors: Yoshida Seikoh , Suzuki Joe
Published: October 2002

We have grown a high quality GaN for fabricating a metal
semiconductor field effect transistor (MESFET) using gas-source molecular
beam epitaxy (GSMBE). A GaN MESFET for high temperature operation
was developed. We used Au/Pt as a Schottky gate, and Au/Ti/Al as a source-drain. The endurance of high temperatures by GaN MESFET was
investigated. It was confirmed for the first time, that the FET performance
was satisfactory even after the FET was heated at 400°C for over 700 h,
thereby demonstrating, for the first time, the reliability of GaN MESFET. The device continued to be operative even when, heated further up to 600°C.
One-Step Grown Lateral p-n Junctions on GaAs (001) Patterned Substrates with (110) Sidewalls by Molecular Beam Epitaxy
Authors: Okumura Hideyo , Saito Nobuo , Kusano Jun-ichi , Aida Tahito , Sato Fumio , Takizawa Kuniharu
Published: October 2002

One-step growth of lateral p-n junctions on GaAs patterned substrates is investigated to demonstrate the possibility of obtaining a current confinement structure by utilizing the amphotericity of Si.
Rectangular patterns of the (001) plane encircled by four {110} sidewalls were etched on the substrates by means of anisotropic etching of an NH4OH+H2O2+H2O solution with high H2O
content. Si-doped GaAs layers are grown on thus-prepared patterned substrates by molecular beam epitaxy. A cathodoluminescence study shows the layers grown on the {110}
sidewalls are p-type, whereas they are n-type on the (001) surface. The potential of the lateral p-n junctions for forming a current confinement structure for surface light emitting devices is discussed.
A Novel Phase-Modulated Excimer-Laser Crystallization Method of Silicon Thin Films
Authors: Chang-Ho Oh Chang-Ho Oh , Motohiro Ozawa Motohiro Ozawa , Masakiyo Matsumura Masakiyo Matsumura
Published: October 2002

We propose a novel excimer-laser crystallization method that uses a phase-shift mask for large-grain growth of Si thin films on the glassy substrate. Due to interference effects of the laser light, the phase difference of light at the mask results in spatial modulation of light intensity at the sample surface, which triggers the lateral grain growth. Grains as large as 7 µm could be grown by a single-shot irradiation.
The Effect of BCl3 Addition on RuO2 Etching in M=0 Helicon Reactor
Authors: Kim Yun-Sang , Rampersad Regan H. , Tynan George R.
Published: October 2002

Photoresist patterned ruthenium oxide etching for ferroelectric capacitor structured device
has been studied using high density helicon wave plasma. The trends in the effect on the
etch rate and selectivity to photoresist for BCl3 ratio to Cl2 have been determined. It was
found that the strong scavenging effect of BCl3 lead primarily after ion bombardment on
the film surface. The possible mechanism on the reduction of the issued by-product,
RuO4, during plasma process was proposed using plasma and optical emission data.
Self-Organizing Three-Dimensional Colloidal Photonic Crystal Structure with Augmented Dielectric Contrast
Authors: Fukuda Koichi , Sun Hongbo , Matsuo Shigeki , Misawa Hiroaki
Published: October 2002

We demonstrated that low-velocity quasi-equilibrium evaporation of
water from an aqueous colloidal solution of polystyrene microparticles with
220 nm diameter enabled the preparation of a three-dimensional colloidal-air photonic crystal structure without significantly distorting the lattice, and
the absorption peak of the structure was observed at around 500 nm. A
much stronger photonic band gap effect is expected due to an approximately
30% increase of the dielectric contrast.
Determination of the Linear Electrooptic Coefficient of a Lead Zirconate Titanate Thin Film Using Two-Beam Polarization Interferometer with an Adaptive Photodetector
Authors: Spirin Vasilii V. , Lee Changho , No Kwangsoo , Sokolov Igor A.
Published: October 2002

A novel interferometric modulation technique for optical thin-film testing using a two-beam polarization (TBP) interferometer with GaAs:Cr adaptive photodetector is presented. The technique enables determination of Pockels coefficient of thin films with a strong Fabry-Perot effect and automatic adjustment and maintenance operation point of the interferometer. We use this method for measuring the effective differential linear electrooptic coefficientre=r33-(n0/ne)3r13of lead zirconate titanate (PZT) thin film. A strong hysteresis effect with a slightly asymmetric form of the hysteresis loop was observed for the dependence of the effective differential Pockels coefficient of the PZT thin film on the DC electric field. The values ofreare in agreement with known data.
Synthesis and Electrical Properties of Phosphorus-Doped Homoepitaxial Diamond (111) by Microwave Plasma-Assisted Chemical Vapor Deposition Using Triethylphosphine as a Dopant Source
Authors: Saito Takeyasu , Kameta Masanori , Kusakabe Katsuki , Morooka Shigeharu , Maeda Hideaki , Hayashi Yasunori , Asano Tanemasa
Published: October 2002

A phosphorus-doped (111) diamond film was formed homoepitaxially on a nondoped diamond film, which was also formed homoepitaxially on a type Ib (111) diamond substrate, by microwave plasma-assisted
chemical vapor deposition using CH4 as the carbon source and triethylphosphine (TEP, P(C2H5)3) as the dopant source. The P-doped film, which was
approximately 800 nm in thickness, exhibited an n-type conduction in the temperature range of 100–500 K. This represents the first such observation, for a film
prepared using TEP as the dopant. The activation energy for carrier concentration was 0.09 eV in the range of 145–500 K. The Hall mobility reached a maximum of
approximately 3.5 cm2/(V·s) at 145 K and decreased to 0.15 cm2/(V·s) at 500 K. Phosphorus was uniformly incorporated into the diamond film, as evidenced
by secondary ion mass spectrometry.
Electron Field Emission Resulting from High-Density Breakdown Sites on Amorphous Carbon-Polyimide Composite Films
Authors: Li Yunjun , Yao Ning , Zhao Gang , He Jintian , Zhang Binglin , Gong Zhiben
Published: October 2002

Amorphous carbon-polyimide composite films (a-C:P) were prepared by laser ablation using a 266 nm wavelength fourth- harmonic YAG laser. A rotating target for deposition composed of half a pyrolytic graphite tape and half a 0.12 mm thick polyimide sheet. A high-density breakdown site of ∼106/cm2was obtained while field emission experiments were performed on the a-C:P films. After breakdown, the turn-on field decreased and the total emission current increased. Permanent breakdown sites with crater-like structures were formed on a large breakdown area of 0.3 cm2due to a quasi-explosion process. A mean emission site density of 105/cm2on some breakdown regions was obtained. The crater structure was found to be a potential candidate for emitting electrons with a low turn-on field of 4 V/µm.
Nematic Liquid Crystal Phase-Gratings for Reflective Spatial Light Modulators
Authors: Lu Minhua , Yang Kei-Hsiung
Published: October 2002

The twisted nematic liquid crystal phase grating, using patterned alignment with opposite
twist angles for reflective spatial light modulators, is analyzed with respect to operating mode,
diffraction efficiency and operating voltage including the effect of disclination lines between
opposite twist domains. In general, the high-field difflactive modes have lower operating
voltages, slower response time and relatively higher contrast ratio than zero-field diffractive
modes. We describe a high-field diffractive mode with a twist angle of approximately ±54° for opposite twist domains which achieves an optical efficiency of nearly 100% and an estimated contrast ratio greater than 300:1 for monochromatic light.
Electroluminescence of Nanocrystal Si Embedded in Single-Crystal CaF 2/Si(111)
Authors: Masahiro Watanabe Masahiro Watanabe , Takeshi Matsunuma Takeshi Matsunuma , Takeo Maruyama Takeo Maruyama , Yasuhisa Maeda Yasuhisa Maeda
Published: October 2002

Electroluminescence (EL) from a single-crystal CaF2 layer including
nanocrystal Si formed on Si(111) substrate has been
demonstrated. For the sample grown by the coevaporation of
Si and CaF2 with a flux ratio of Si:CaF2=1:3–1:4,
visible electroluminescence was clearly observed at room
temperature with pulsed bias of approximately 10 V.
A typical EL spectrum had a 580 nm peak wavelength and
280 nm the full width at half maximum (FWHM). EL can be
observed from the sample with appropriate size and
density of nanocrystal Si embedded in single-crystal CaF2.
Effects of the Deposition Conditions of the Seed Layer on the Crystallinity and Electrical Characteristics of the Pb(Zr,Ti)O3 Films
Authors: Sung-Tae Kim Sung-Tae Kim , Yong-Il Kim Yong-Il Kim , Hyun-Ho Kim Hyun-Ho Kim , Moon-Yong Lee Moon-Yong Lee , Won-Jong Lee Won-Jong Lee
Published: October 2002

Pb(Zr,Ti)O3 (PZT) films were deposited on Pt/Ti/SiO2/Si
substrates by electron cyclotron resonance (ECR) plasma enhanced DC
magnetron reactive sputtering. Various seed layers with different
compositions were formed by varying the target power of each element at
the initial stage of the deposition process, and the effects of the seed
layers on the properties of the PZT films subsequently deposited on them
were studied. The seed layers were fabricated in three ways: increasing
Pb flux at a particular Zr/Ti flux ratio which is kept constant in the
subsequent PZT film deposition process, increasing Pb flux with decreasing
the Zr/Ti flux ratio to make the layer composition below the morphotrophic
phase boundary (Zr/Ti=1.08) value and finally maintaing a Zr flux of zero
for the PbTiOx seed layer. It was found that the PZT seed layer is more
effective than a PbTiOx seed layer and the effectivity of the seed layer is
increased not by just increasing the supply of Pb, but by increasing the
Pb supplement in the presence of low Zr/Ti flux ratio. However, too
much excess supplement of Pb element during the seed layer deposition
degrades the crystallinity and capacitance properties of overlying PZT films.
Surface Morphology of Ba Atomic Layer on a LiF(001) Surface Studied by He Atomic Beam Scattering
Authors: Murakami Fumiaki , Yagyu Shinjiro , Kino Yasunobu , Yamamoto Shigehiko
Published: October 2002

He atomic beam scattering has revealed the morphology of a thin Ba layer on a
LiF(001) surface. The Ba atoms randomly deposited on a LiF(001) surface followed by
subsequent annealing form an atomically flat atomic-order layer. The layer does not reflect the
periodic structure of the substrate. Flatness of the layer before and after annealing is evaluated
using the hard cube model with surface roughness parameters. Prolonged annealing causes Ba
atoms to react with the substrate and roughens the surface. The structure of the reaction product
measured by He atomic beam diffraction shows periodicity twice as large as that of the substrate.
Effect of Very Thin SiC Layer on Heteroepitaxial Growth of Cubic GaN on Si (001)
Authors: Yuichi Hiroyama Yuichi Hiroyama , Masao Tamura Masao Tamura
Published: October 2002

We have investigated the effect of very thin SiC layer formation on Si (001) for cubic GaN growth by RF plasma-assisted molecular beam epitaxy. It is found that a cubic GaN film can be epitaxially grown on Si (001) covered with an approximately 2.5-nm-thick cubic SiC layer, while GaN grown on Si (001) without such an SiC layer results in the polycrystal growth of a predominantly hexagonal phase. In the latter case, an approximately 1-nm-thick amorphous Si layer is formed at the interface between GaN and Si by the irradiation of nitrogen plasma.
A Completely Single-Mode and Single-Polarization Vertical-Cavity Surface Emitting Lasers Grown on GaAs (311)B Substrate
Authors: Nishiyama Nobuhiko , Mizutani Akimasa , Hatori Nobuaki , Koyama Fumio , Iga Kenichi
Published: October 2002

We realized a completely single-mode and single-polarization 0.98 µm InGaAs/GaAs
vertical-cavity surface emitting laser (VCSEL) grown on a GaAs (311) B substrate. The
device operates in a single transverse, longitudinal mode and polarization state in the entire
tested current range. An oxide confinement structure with a nearly square oxide aperture of
2.5 µm×3.0 µm was formed for transverse mode control. We obtained a side mode
suppression ratio of over 35 dB and a polarization mode suppression ratio of over 25 dB
between the [233] and the [011] axis modes in the entire driving range. The threshold
voltage and electrical specific resistance are as low as 1.5 V and 1.1×10-4 Ω·cm-2,
respectively. One of the tested devices shows a record low threshold current of 230 µA for
non-(100) substrates.
Wavelength Conversion in LiNbO3 Waveguide Difference-Frequency Generation Devices with Domain-Inverted Gratings Fabricated by Voltage Application
Authors: Fujimura Masatoshi , Shiratsuki Akihide , Suhara Toshiaki , Nishihara Hiroshi
Published: October 2002

LiNbO3 waveguide quasi-phasematched (QPM) difference-frequency generation (DFG)
devices were studied for wavelength conversion in wavelength range of 1-2 µm. The device
performance was analyzed, and DFG output power was estimated to be 1.0 mW for 10 mW
signal power, 500 mW pump power, and 3 mm interaction length. A prototype device was
fabricated for DFG at 1.67 µm wavelength from 1.54 µm signal and 0.8 µm pump. Voltage
application technique was successfully used in fabrication of ferroelectric domain inverted
gratings for QPM. DFG experiments were performed using a distributed feedback laser
diode as a signal light source and a Ti:Al2O3 laser as a pump light source, and DFG light of
1.67 µm wavelength was obtained.
BCl3/Ar Plasma-Induced Surface Damage in GaInP/InGaAs/GaInP Quantum-Well High-Electron-Mobility Transistors
Authors: Kuo Chi-Wein , Su Yan-Kuin , Kuan Hrong
Published: October 2002

BCl3 plasma etching for gate recessing of GaInP/InGaAs/GaInP quantum-well
high-electron-mobility transistors (QHEMTs) is found to be improved by the addition of an appropriate amount of Ar to the gas flow. The influence of the BCl3/Ar gas flow ratio on the etching selectivity of GaAs to GaInP and surface damage was studied. Surface damage was determined using Raman spectroscopy and drain-source current to gate-source voltage (I
ds-V
gs) measurements. For the BCl3/Ar flow ratio either lower or higher than 6/4, Raman spectra indicate that the plasma causes damage that will make the InP- and GaP-like longitudinal optical (LO) modes undergo redshift and their intensities to become smaller. The DC characteristics of QHEMT S6:4 dry-etched with 6:4 BCl3/Ar were superior to those of the QHEMT S
wet wet-etched, and QHEMT S10:0, dry-etched with pure BCl3. These results show that the use of the BCl3/Ar gas mixture has considerable potential for achieving high selectivity and low damage in GaInP/InGaAs/GaInP QHEMTs.
MoSe 2 layer formation at Cu(In,Ga)Se 2/Mo Interfaces in High Efficiency Cu(In1- xGa x)Se 2 Solar Cells
Authors: Shiro Nishiwaki Shiro Nishiwaki , Naoki Kohara Naoki Kohara , Takayuki Negami Takayuki Negami , Takahiro Wada Takahiro Wada
Published: October 2002

MoSe2 layers formed at the interface between Cu-In-Ga-Se and Mo layers were studied by X-ray diffraction and high resolution transmission electron microscopy. Various composition Cu-In-Ga-Se films such as Se, Cu-Se, In-Ga-Se and Cu-rich Cu-In-Ga-Se were deposited on Mo coated glass substrates by physical vapor deposition. For the case of the Se/Mo interface, a MoSe2 layer of about 100 Å thickness was observed. The c-axis of the MoSe2 grains were found to be oriented normal to the surface of Mo layer. For the Cu-Se/Mo and Cu-rich Cu-In-Ga-Se/Mo structures, the thickness of the MoSe2 layers found at the interface was thin. For the case of the In-Ga-Se/Mo structure, a 0.1 µm thick interfacial MoSe2 layer was observed whose c-axis was oriented parallel to the Mo surface. The microstructure of the In-Ga-Se/Mo film was similar to that of the device quality CIGS/Mo structure deposited by the “3-stage” process. A formation mechanism for the MoSe2 layers occurring during the “3-stage” process is proposed.
Polymer Electroluminescent Diodes with Ring Microcavity Structure
Authors: Akihiko Fujii Akihiko Fujii , Sergey V. Frolov Sergey V. Frolov , Z. Valy Vardeny Z. Valy Vardeny , Katsumi Yoshino Katsumi Yoshino
Published: October 2002

Cylindrical microcavity structures, such as microrings of π-conjugated conducting polymers, poly(2, 5-dialkoxy- p-phenylene vinylene) (ROPPV), on optical fibers, were fabricated for an optically pumped laser and a light emitting diode (LED). Extremely low excitation threshold for lasing has been demonstrated with the microring structure. Microring LEDs with cylindrical geometry of Al/π-conjugated conducting polymers, ROPPV, /ITO on optical fibers of 125 µm external diameter have been fabricated for the first time and orange electroluminescence has been observed upon application of an electric field. These results suggest the future possibility of electrically pumped conducting polymer laser diodes.
Reduction in Driving Voltage of In-Plane Switching Liquid Crystal Displays Using Photo-Alignment Method
Authors: Li Xiang Tong , Kawakami Atsuhiro , Akiyama Hidenari , Kobayashi Shunsuke , Iimura Yasufumi
Published: October 2002

In-plane switching liquid crystal displays (IPS-LCDs) have been fabricated by
a photo-alignment method using poly (vinyl cinnamate), and the effect of the
azimuthal anchoring energy on the electrooptical performance has been studied
theoretically and experimentally. The results show a large reduction in the driving
voltage of IPS samples with decreasing azimuthal anchoring energy, which
demonstrates the usefulness of the photo-alignment method for fabricating IPS-LCDs.
Prevention of Oxygen Incorporation in poly-Si1-xGex Deposition with Interfacial Amorphous Silicon Layer
Authors: Park Young-Bae , Lee Seo-Kyu , Kim Ohyun , Rhee Shi-Woo
Published: October 2002

Polycrystalline silicon germanium (poly-Si1-x
Ge
x
) thin films have been deposited on thermal oxide and a-Si surfaces by rapid thermal chemical vapor deposition (RTCVD) from SiH4-GeH4-H2. The effect of oxygen incorporation on the initial surface of poly-Si1-x
Ge
x
/SiO2 has been investigated. Poly-Si1-x
Ge
x
films deposited on the substrate with an amorphous silicon buffer layer on the oxide (poly-Si1-x
Ge
x
/a-Si/SiO2) show better crystallinity and contain less oxygen than those deposited directly on the oxide surface (poly-Si1-x
Ge
x
/SiO2). Poly-Si1-x
Ge
x
films deposited directly on the oxide contain 5–23.5 at% oxygen due to the etching effect on the SiO2 surface by decomposed GeH
x
during the initial stages of the deposition. All films have mixed amorphous and crystalline phases and the grain size and crystallinity increased when the films were deposited on a thin a-Si layer.
Electric Field-Effect Enhancement by a Combination of Coplanar High-TC Superconducting Devices with Step-Edge Junctions
Authors: Suzuki Shigeru , Sugai Satoshi , Oda Shunri
Published: October 2002

We investigated electric field-effect enhancement by combining a grain boundary junction with a coplanar-type superconducting field-effect device. Superconducting field-effect devices are promising for
use in the design and construction of switching devices. Because of its structure, the coplanar device has advantages of low gate leakage current and simple fabrication
process. These advantages can be enhanced when the device is combined with the grain boundary structure. We describe the fabrication process of a coplanar field-effect
device with step-edge junctions and measurement of the electrical properties. The gate leakage current is sufficiently low for valid measurement. The channel I–V
characteristics show large critical current modulation when negative gate voltage is applied.
IrO2/Pb(ZrxTi1-x)O3(PZT)/Pt Ferroelectric Thin-Film Capacitors Resistant to an Interlayer-Dielectric-Deposition Process
Authors: Kushida-Abdelghafar Keiko , Fujisaki Yoshihisa
Published: October 2002

Resistance of the IrO2/PZT/Pt ferroelectric capacitor to the ambient of an
interlayer-dielectric-deposition process is investigated for integrating the capacitor in a ferroelectric
nonvolatile memory. Silicon dioxide films are deposited on the capacitor as the
interlayer dielectric by plasma-enhanced chemical vapor deposition (CVD) using SiH4
and N2O gases. Degradation of ferroelectric characteristics reported so far for Pt/PZT/Pt
capacitors is found to be significantly suppressed in the IrO2/PZT/Pt structure. This is
because IrO2 does not show a catalytic effect as exhibited by a platinum electrode which
causes hydrogen decomposition during the CVD processes. Hence, the IrO2/PZT/Pt
capacitor structure proposed by us did not undergo the degradation in the process.
Surface Flattening of GaN by Selective Area Metalorganic Vapor Phase Epitaxy
Authors: Akasaka Tetsuya , Nishida Toshio , Ando Seigo , Kobayashi Naoki
Published: October 2002

The surface flattening of GaN films by selective area metalorganic vapor phase
epitaxy is demonstrated. Selectively grown GaN films 30–50 µm in diameter have
smooth surfaces with neither bunched steps nor ridge growth. These surfaces
consist of bilayer height spiral steps that originate from screw dislocations. The
surface flattening is probably due to the disappearance of steps at the edges of the
selectively grown GaN. Desorption of the film forming precursors from the
growing surface is increased on the smooth GaN surface during growth at substrate
temperatures of 1000°C or higher in H2 carrier gas. A low dislocation density is
essential for a smooth GaN surface, because the spirals determine the step structure.
Improvement of Soft Magnetic Properties of Co–Cr–O Film by Additional X(=Rh, Ir, Ag, or Au)
Authors: Morikawa Takeshi , Suzuki Motofumi , Taga Yasunori
Published: October 2002

Soft magnetic properties have been achieved for Co–X–Cr–O (X=Rh, Ir, Ag, or Au) films including nanoscaled Co grains. It is found
that the presence of any additional X not only reduces the
coercivity but also enhances the uniaxial anisotropy field of the
Co–Cr–O film. A Co65Rh8Cr11O16 film including both the hcp and
fcc of nanocrystalline Co shows a low coercivity of 1.6 Oe and a
high ferromagnetic resonance frequency of 3.4 GHz. A relative
permeability of µ′=90 is obtained at 1 GHz.
Improvement of Electrode/Organic Layer Interfaces by the Insertion of Monolayer-like Aluminum Oxide Film
Authors: Yoshitaka Kurosaka Yoshitaka Kurosaka , Norio Tada Norio Tada , Yutaka Ohmori Yutaka Ohmori , Katsumi Yoshino Katsumi Yoshino
Published: October 2002

Insertion of a thin film of aluminum oxide (Al2O3) at
the interface of electrodes and organic layers has been investigated.
Insertion of a thin film of Al2O3 at the interface of the ITO
anode and the diamine derivative (TPD) layers, as well as at the interface
of the
8-hydroxyquinoline aluminum (Alq3) and the Mg:Ag cathode in the
electroluminescent (EL) diode has been examined. The insertion of
an Al2O3 layer with a proper thickness was observed to enhances
the emission
efficiency of the device. The mechanism of quantum efficiency
enhancement of the device was studied.
Measurement of Residual Stress in Diamond Films Obtained Using Chemical Vapor Deposition
Authors: Kim Jung Geun , Yu Jin
Published: October 2002

Diamond films were deposited on a p-type Si substrate using the hot filament chemical vapor
deposition (HFCVD) method. Residual stresses in the films were subsequently measured using the
curvature, the X-ray diffraction (XRD) sin
2ψ, and the Raman peak shift methods. Results from the three
methods were in agreement and indicated that residual stresses changed from compressive to tensile with
increasing film thickness, but the maximum or minimum extent of the stresses measured by the Raman
and XRD methods was 3–5 times larger than those by the curvature method. These results were
correlated with the results from the determination of Young's modulus and total peak shifts by the XRD and
the Raman methods. Young's moduli of diamond films were measured by the sonic resonance method,
and the peak shift due to residual stress was separated from the total peak shift using the beam bending
theory. After the adjustment, the disparity among the stress measurements was significantly reduced and a
stress range of -0.5 GPa to +0.5 GPa was obtained.
Role of Cl or I Codoping in Li-Doping Enhancement in ZnSe
Authors: Yamamoto Tetsuya , Katayama-Yoshida Hiroshi
Published: October 2002

We propose the doping of Cl or In species intop-type ZnSe crystals doped with Li, a Zn-substituting species, in order to fabricate low-resistivityp-type ZnSe crystals, based onab initioelectronic band structure calculations. The simultaneous codoping of a Cl or I donor and a Li acceptor enhances Li incorporation inp-type ZnSe crystals due to a strong interaction between donors and acceptors with a decrease in the Madelung energy, resulting in the formation ofp-n-pcomplexes that occupy the nearest-neighbor sites.
Monoclinic Tungstates KDy(WO 4) 2 and KLu(WO 4) 2 - New χ( 3)-Active Crystals for Laser Raman Shifters
Authors: Findeisen Alexander A. Kaminskii , Sergei N. Bagayev Sergei N. Bagayev , Fedor A. Kuznetsov Fedor A. Kuznetsov , Alexsei A. Pavlyuk Alexsei A. Pavlyuk , Georges Boulon Georges Boulon , Frederic Bourgeois Frederic Bourgeois
Published: October 2002

Efficient high-order Stokes and anti-Stokes generation in the visible and near infrared (NIR) in monoclinic KDy(WO4)2 and KLu(WO4)2 1aser host crystals by stimulated Raman scattering (SRS) and Raman-induced four-wave mixing (RFWM) were observed at 300 K for the first time in the single-pass geometry under picosecond excitation. All scattering components were identified and connected with the SRS-active vibration modes of these tungstates.
Optical Frequency Comb Generation with an Optical Loop
Authors: Takanori Saitoh Takanori Saitoh , Shigenori Mattori Shigenori Mattori , Shigeru Kinugawa Shigeru Kinugawa , Koichiro Miyagi Koichiro Miyagi
Published: October 2002

We propose a novel method using an optical loop system to expand the span of an optical frequency comb. The validity of this system was confirmed experimentally in the 1.5 µm wavelength region. By using this system, the modulation index was doubled.
Three-Dimensional Microscopic Crystallization in Photosensitive Glass by Femtosecond Laser Pulses at Nonresonant Wavelength
Authors: Kondo Yuki , Suzuki Toshio , Inouye Hideyuki , Miura Kiyotaka , Mitsuyu Tsuneo , Hirao Kazuyuki
Published: October 2002

We investigated three-dimensional microscopic crystallization by irradiation of femtosecond and nanosecond laser pulses at a nonresonant wavelength of 630 nm in a photosensitive glass containing Ag+ and Ce3+. The pulse widths of the lasers were 150 fs and 3 ns, respectively. By focusing the femtosecond laser beam and following heat-treatment, spot crystallization within the glass of about 10 µm successfully occurred without surface crystallization, while the use of the nanosecond laser beam produced no crystallization. By using the femtosecond laser, it is possible to create three-dimensional structured crystallization because of the use of transparent light and the presence of a threshold for crystallization.
Transmission Electron Microscope Observations of Interfaces in YBa 2Cu 3Ox/BaSnO 3/YBa 2Cu 3Ox trilayers
Authors: Shintaro Miyazawa Shintaro Miyazawa , Masashi Mukaida Masashi Mukaida
Published: October 2002

A new insulating material, BaSnO3 with a relatively large mismatch to YBa2Cu3O
x
is investigated as a barrier material in a superconductor/ insulator/ superconductor (SIS) structure.
All c-axis oriented YBa2Cu3O
x
/ BaSnO3/ YBa2Cu3O
x
SIS structures are grown by an in situ sequential pulsed laser deposition technique.
Transmission electron microscopy (TEM) reveals that BaSnO3 thin films cover well c-axis oriented YBa2Cu3O
x
thin films.
Moreover, c-axis oriented YBa2Cu3O
x
thin films grow epitaxially on BaSnO3 thin films with very good wetability.
The relatively large mismatch provides periodical lattice discontinuity, which is probably associated with the generation of dislocations in one third of c-axis unit of YBa2Cu3O
x
thin films.
This study provides guidelines for selecting insulating materials.
Application of Wavelet Analysis to Plasma Fluctuation Study on GAMMA 10
Authors: G. Bruskin Leonid , Atsushi Mase Atsushi Mase , Shigeyuki Kubota Shigeyuki Kubota , Tokihiko Tokuzawa Tokihiko Tokuzawa , Naoyuki Oyama Naoyuki Oyama , Akiyosi Itakura Akiyosi Itakura , Teruo Tamano Teruo Tamano
Published: October 2002

A time-frequency analysis of plasma turbulence is performed for the GAMMA10 tandem mirror plasma. The method is based on the decomposition of the reflectometer signal into a set of wavelets.
Fast changes in the instantaneous spectra of fluctuations were observed in both the low-frequency (up to 50 kHz) and high-frequency (5–6 MHz) spectral regions.
In order to estimate the propagation velocity of turbulent fluctuations, a wavelet cross-correlation function was calculated.
Comparison of wavelet spectra, corresponding to different reflectometer channels, demonstrates the existence of short-time flashes of fluctuation intensity, as well as elongation of low-frequency disturbances along the magnetic field lines and their rotation in E ×B direction.
Imaging p–n Junctions by Scanning Auger Microscopy
Authors: Takashi Ide Takashi Ide , Seiichi Hiroshima Seiichi Hiroshima , Keiji Shimizu Keiji Shimizu
Published: October 2002

We present a new technique for imaging p–n junctions in semiconductors based on Auger electron spectroscopy. By measuring fine Auger electron spectra of the semiconductor material (e.g., silicon LVV Auger), the position of the Fermi level in the band gap of the semiconductor is estimated from the energy shift of the Auger spectra. The position of the Fermi level depends on the type of dopant. By applying a correlation calculation to measure the Auger energy shift, which is smaller than the band gap of the semiconductor, we can successfully image two-dimensional p–n junctions in LSI devices.
Near-Room-Temperature Selective Oxidation on GaAs Using Photoresist as a Mask
Authors: Wang Hwei-Heng , Wang Yeong-Her , Mau-Phon Houng Mau-Phon Houng
Published: October 2002

Selective oxidation on GaAs operated at near room temperature,
by a liquid phase chemically enhanced method using photoresist as a mask,
is proposed and demonstrated.
Because of the low temperature and electroless features of the oxidation
method, the process is simple, economic and reliable.
Good electrical insulating properties comparable with those of
thermal oxide have been obtained.
According to the results of X-ray photoelectron spectroscopy,
the chemistry of the oxide surface is stable after thermal annealing.
The thermal stability shows the potential for device fabrication.
Carrier-Relaxation Process in Time-Resolved Up-Converted Photoluminescence at Ordered (Al0.5Ga0.5)0.5In0.5P and GaAs Heterointerface
Authors: Yamashita Kenichi , Kita Takashi , Nishino Taneo , Oestreich Michael
Published: October 2002

Up-converted photoluminescence (UPL) was observed at the
long-range ordered (Al0.5Ga0.5)0.5In0.5P/GaAs(001)
heterointerface, during the excitation of GaAs. Excitation-power
dependence of the UPL intensity reflects carrier-localization
properties caused by potential fluctuations due to a multidomain
structure in the ordered
(Al0.5Ga0.5)0.5In0.5P. When we excited the GaAs
layer, photoexcited carriers spatially transferred to the
(Al0.5Ga0.5)0.5In0.5P layer and relaxed from
higher lying states to lower lying states in the fluctuated
potential. Time-resolved measurements were performed for the UPL and
normal photoluminescence (NPL) excited by an above-gap light. We
observed a slowly rising component in the time-resolved UPL, whereas
the NPL showed an exponential decay profile. These results reveal
that the carrier-relaxation processes are different near the surface
and near the interface of the epitaxial layer.
Thermal Quenching of Er-Related Luminescence in GaInP Doped with Er by Organometallic Vapor Phase Epitaxy
Authors: Fujiwara Yasufumi , Ito Takashi , Ichida Masao , Kawamoto Takeshi , Watanabe Osamu , Yamakawa Ichiro , Takeda AraoNakamura
Published: October 2002

Thermal quenching of Er-related photoluminescence (PL) due to intra-4f shell
transitions of Er3+ ions has been investigated in
Ga
x
In1-x
P (0≤x≤1) doped with Er by
organometallic vapor phase epitaxy (OMVPE). In GaInP grown on GaP and InP, the 4.2 K
PL intensity gradually increases with increasing Ga composition, while the spectral shape
remains unchanged. In GaInP grown on GaAs, the 4.2 K PL spectrum is dominated by three
emission lines whose relative intensity depends on the Ga composition. Thermal quenching of
the Er-related luminescence gradually decreases with increasing Ga composition, i.e.,
increasing band gap. PL lifetimes and their temperature variations are discussed in relation to
deep-level properties of Er in the excitation mechanism of the 4f shell.