bluuebunny/crossref_metadata_2025 huggingface dataset:
Ion Beam Assisted Deposition of Tungsten on GaAs
Authors: Xu Zheng , Kosugi Toshihiko , Gamo Kenji , Namba Susumu
Published: February 2005

Ion beam assisted deposition of W on GaAs has been performed by irradiating low energy (500–2000 eV) H2
+ or Ar+ beams in WF6 ambient. The low energy beams were used to reduce damage in the substrate. The damage and annealing properties were examined by Schottky barrier characteristics and the DLTS method. W films with purity better than 90% and resistivity of ∼10-5 Ω·cm were deposited. Schottky contacts were formed by 500 eV H2
+ and all Ar+ irradiation without any annealing, though the leakage current was larger for Ar+ irradiation, while almost ohmic contacts were formed for 2000 eV beam irradiation, probably due to the thicker damaged layer in the substrates. Annealing at 350°C for 10 min yielded decreased reverse leakage current by more than two orders of magnitude and good Schottky contacts with n-factor ∼1.
Silicon-Hydrogen Bonds in Silicon Native Oxides Formed during Wet Chemical Treatments
Authors: Sugiyama Kazuhisa , Igarashi Takayuki , Moriki Kazunori , Nagasawa Yoshikatsu , Aoyama Takayuki , Sugino Rinshi , Ito Takashi , Hattori Takeo
Published: February 2005

Silicon-hydrogen bonds in silicon oxide films were detected for the first time by applying surface-sensitive X-ray photoelectron spectroscopy and were confirmed by measuring infrared absorption. The areal density of silicon-hydrogen bonds in native oxides formed in a hot solution of HNO3 is estimated to be nearly 2×1014 cm-2, and is much larger than that formed in a solution with a composition of NH4OH:H2O2:H2O=1:1.4:4.
A Sub-10 ps/gate Direct-Coupled FET Logic Circuit with 0.2 µm-Gate GaAs MESFET
Authors: Tsuji Hiromi , Fujishiro Hiroki Inomata , Nakamura Hiroshi , Nishi Seiji
Published: February 2005

A 0.2 µm-gate buried p-layer metal semiconductor field-effect transistor (MESFET) using a new gate fabrication technique is reported. With this technique, the gate length can be easily reduced down to less than 0.2 µm. The source resistance of enhancement mode field-effect transistor (FET) can also be reduced, resulting in excellent DC and RF performance. The maximum transconductance of 648 mS/mm and K-value of 506 mS/V ·mm were obtained. The maximum cutoff frequency was as high as 96.1 GHz. The propagation delay time of 8.1 ps/gate was observed with a power dissipation of 1.7 mW/gate at a supply voltage of 1 V.
ESR Spectra and Low-Field Microwave Absorption in Bismuth and Thallium Based Cuprate Superconductors
Authors: Edwards Peter P. , Janes Robert , Liu R. S. , Wu P. T. , Chang C. T.
Published: February 2005

Electron Spin Resonance and low-field microwave absorption are reported for a range of Bi- and Tl-based superconductors in the Bi-Ca-Sr-Cu-O, Bi(Pb)-Ca-Sr-Cu-O and Tl-Ca-Ba-Cu-O series together with the new monophasic series (Tl0.5Pb0.5)(Ca0.8A0.2)Sr2Cu2O
y
(A=Y or Er) superconductors. In contrast to two recent reports of ESR in the Tl-Ca-Ba-Cu-O and Bi(Pb)-Ca-Sr-Cu-O systems, we find: (i) no evidence of any “intrinsic” Cu2+ ESR signals close to the free spin region, and (ii) no evidence of a (low-field) microwave absorption at temperatures above T
c. The question of ESR silence in these oxide superconductors and related phases is discussed.
Open-Circuit Voltage Decay (OCVD) Measurement Applied to Hydrogenated Amorphous Silicon Solar Cells
Authors: Sakata Isao , Hayashi Yutaka
Published: February 2005

A small-signal open-circuit voltage decay (OCVD) method has been applied for the first time to measure carrier lifetime in hydrogenated amorphous silicon solar cells under dc bias illumination. The observed decay has multiexponential time dependence with the time constants between 0.7 µs and 20 µs. In the n-i-p type cells investigated in this paper, these time constants correspond to deep trapping hole lifetimes near the n-layer/i-layer interface of the cell. The light-induced changes in the OCVD signal have been observed.
Synthesis of Bi-Base High-Tc Oxide Superconductors through an Organic Acid Salt Thermal Decomposition Process
Authors: Asaka Takashi , Okazawa Yoshiyuki , Hirayama Toru , Tachikawa Kyoji
Published: February 2005

High-T
c Bi-Pb-Sr-Ca-Cu oxide superconductors have been successfully synthesized through a decomposition of organic acid salts. At the intermediate stage of this process, a gel state is obtained from a homogeneous solution. The gel shows a thermoplasticity which may facilitate its fabrication into a fiber form. The offset T
c of the specimen made from this process is 102 K, which is appreciably improved by an intermediate pressing between sinterings. The highest T
c and J
c (77 K, 0 T) so far obtained are 109 K and 810 A/cm2, respectively.
Characteristics of Superconducting Gd-Ba-Cu-O Thin Films
Authors: Hayashi Shigenori , Kamada Takeshi , Kohiki Shigemi , Hirao Takashi , Wasa Kiyotaka , Matsuda Akihisa , Hangyo Masanori , Nakashima Shin-ichi
Published: February 2005

Characteristics of Gd-Ba-Cu-O films in different crystal phases were studied. An evolution study showed that the chemical diffusion of oxygen depends on the crystal phase. The oxygen content was estimated from the Raman shift of the oxygen stretching mode. The reduction of Cu valence due to the orthorhombic-to-tetragonal transition was revealed by photo-electron spectroscopy. Optical reflectivity and absorption spectra showed that the transition is associated with a change of electronic state from a metal with a plasma edge of 1.16 eV to a semiconductor with a charge transfer gap.
Magneto-Optical Kerr Rotation of the PtMnSb Compound in a High Magnetic Field
Authors: Takanashi Kōki , Watanabe Jun , Kido Giyuu , Fujimori Hiroyasu
Published: February 2005

The polar magneto-optical Kerr rotation angle ( θK) for a polished surface of bulk PtMnSb was measured at 632.8 nm wavelength in high applied magnetic fields up to 15 T. The saturation value of θK was 1.42° in the as-polished state, and it was enhanced to 1.75° by annealing at temperatures higher than 400°C. Simultaneously, θK became easily saturated, suggesting that the magnetic anisotropy near the surface decreased due to annealing. The enhancement of θK and the decrease in magnetic anisotropy are considered to be due to the removal of structural disorder caused by polishing.
Preparation of YBa2Cu3Ox Thin Film by Flame Pyrolysis
Authors: Koguchi Makoto , Matsuda Yoshikazu , Kinoshita Eiji , Hirabayashi Kazuto
Published: February 2005

YBa2Cu3O
x
thin films were prepared by flame pyrolysis. The X-ray diffraction analysis showed that as-prepared films had a strong preferred orientation with the c-axis perpendicular to the film plane. Film resistivities showed a sharp transition at temperatures below 90 K. After thermal annealing in the O2 atmosphere, films showed zero resistivity at about 90 K.
ARXPS Analysis on As-Passivated GaAs Surfaces by HF Dipping Method
Authors: Menda Kazunori , Kanda Eizaburo , Yokoyama Takeshi
Published: February 2005

Undoped (001)GaAs surfaces have been analyzed with angular-resolve X-ray photoemission spectroscopy (ARXPS). The ARXPS analysis was performed on the GaAs surfaces which had been exposed to air for about 3 weeks after chemical etching or HF dipping. Both Ga2O3 and As2O3 signals were detected on the etched surface, whereas the Ga2O3 signal was not detected on the HF-dipped surface. This implies that the HF-dipped surface can be cleaned in vacuum by a thermal treatment at ∼500°C.
Solid State Reaction of Mo on Cubic and Hexagonal SiC
Authors: Hara Shiro , Suzuki Kiyohisa , Furuya Akira , Matsui Youichi , Ueno Tomo , Ohdomari Iwao , Misawa Shunji , Sakuma Eiichiro , Yoshida Sadafumi , Ueda Yoshiya , Suzuki Setsu
Published: February 2005

Mo/3C-SiC and Mo/6H-SiC interfaces have been investigated by Auger electron spectroscopy, Rutherford backscattering spectroscopy, X-ray diffraction, and transmission electron microscopy. High temperature annealing at 1200°C for 1 hour caused a reaction at the interfaces, resulting in forming a Mo2C/Mo5Si3/SiC multilayer. We have found that SiC poly-typism (3C or 6H) and Mo deposition process (evaporation or sputter deposition) make no influence in forming the multilayer. The diffusion mechanism at the Mo/SiC interface will be discussed.
GaInAs/InP PIN Photodiodes Fabricated by MOVPE and a New Zn Diffusion Technique
Authors: Wada Morio , Seko Mashahito , Sakakibara Katsutoshi , Sekiguchi Yoichi
Published: February 2005

GaInAs/InP photodiodes were fabricated by selective zinc diffusion using dimethylzinc as a zinc source to form the p+-region and selective p+-GaInAs growth to produce good ohmic contacts using low-pressure MOVPE. These photodiodes have an external quantum efficiency of 60–80% in the 0.95–1.55 µm-wave-length range, and a dark current of about 30 pA at -2 V and a -3 dB cutoff frequency of 1.4 GHz at 0 V were measured for 110 µm-diam diodes. These results show that this diffusion method is a useful process for fabricating photodiodes or other optical devices.
Upper Critical Field and Critical Current Density in Ceramic Samples of Pb2Sr2Y0.5Ca0.5Cu3O8+δ
Authors: Koike Yoji , Masuzawa Masahiro , Sunagawa Hiromu , Noji Takashi , Kawabe Hisashi , Kobayashi Norio , Saito Yoshitami
Published: February 2005

The electrical resistance of ceramic samples Pb2Sr2Y0.5Ca0.5Cu3O8+δ with zero resistance at 75 K has been measured in magnetic fields up to 21 T. The superconducting transition curve becomes as broad in the field longitudinal to the current direction as in the transverse field. The value of -dH
c2/dT is estimated as 1.7–1.8 T/K. The resistive tail in the lower portion of the transition curve is well expressed as ρ=ρ0 exp
(-U
0/k
B
T). The critical current density J
c shows hysteresis with respect to the magnetic field sweep, and is as low as 0.1 A ·cm-2 at 4.2 K in magnetic fields between 1 T and 13 T.
XPS Studies of 80 K-Phase Bi-Sr-Ca-Cu-O Single Crystals
Authors: Kishida Satoru , Tokutaka Heizo , Toda Fumihiko , Fujimoto Hiroshi , Futo Wataru , Nishimori Katsumi , Ishihara Naganori
Published: February 2005

The XPS (X-ray photoelectron spectroscopy) measurements of the 80 K-phase Bi-Sr-Ca-Cu-O single crystals were carried out on surfaces obtained by cleaving in vacuum, by cleaving in air and heating in vacuum, and by Ar+-sputter etching of the air-cleaved-and-heated surface. The chemical bond natures of all the constituent elements from the air-cleaved-and-heated surface are approximately equal to those from the vacuum-cleaved surface. Sr and Ca from the sputtered surface are more oxidized than those from the vacuum-cleaved surface.
Site-Dependent 18O Substitution in YBa2Cu3O7 Studied by Raman Scattering Measurements
Authors: Nishitani Ryusuke , Yoshida Naoki , Sasaki Yoshiro , Nishina Yuichiro , Yoshida-Katayama Hiroshi , Okabe Yutaka , Takahashi Takashi
Published: February 2005

The site-dependent replacement of 16O with 18O in YBa2Cu3
16O7 has been identified by Raman scattering measurements of different vibrational modes in the CuO2 and BaO planes. The Raman shifts due to isotope substitution for different modes in inequivalent oxygen positions show different temperature dependences. The activation energy of oxygen replacement in the BaO plane is lower than that in the CuO2 plane. The results show that the degree of oxygen substitution is site-dependent.
X-Ray Irradiation of YBa2Cu3Oy
Authors: Izumi Takatoshi , Iwasaki Kazuya , Kurihama Tadashi , Nakajima Tetsuo
Published: February 2005

The effects of irradiation, synchrotron radiation (8 k=30 keV), of high-T
C superconductor YBa2Cu3O
y
have been studied by the Meissner effect and X-ray photoelectron spectroscopy measurements. Changes in the Cu2p satellite emission indicate that Cu2+ changes to Cu1+ with irradiation. Although diamagnetic signals decreased with the irradiation of intense synchrotron radiation, no significant change in the T
C was observed.
Photoluminescence from Electron-Hole Plasma in MOVPE Grown ZnSe
Authors: Nakata Hiroyasu , Yodo Tokuo , Yamashita Ken
Published: February 2005

A strong near-band-edge emission is observed in a ZnSe epitaxial layer excited by a pulsed N2 laser. The spectrum is well fitted by a no-k-selection model of the spontaneous emission from an electron-hole plasma. The obtained electron-hole densities are proportional to effective temperatures. The band renormalizations are estimated from the peak positions.
Atomic Layer Epitaxy of ZnS on GaAs Substrates by Metalorganic Molecular Beam Epitaxy
Authors: Wu Yi-hong , Toyoda Takashi , Kawakami Yoichi , Fujita Shizuo , Fujita Shigeo
Published: February 2005

ZnS was grown on GaAs (001) substrates by a metalorganic molecular beam epitaxy (MOMBE) technique, using sequential dimethylzinc (DMZ) and hydrogen sulfide (H2S) reactant gas exposures, where these gases were supplied to the substrates after cracking at 950 and 1080°C, respectively. The results show that at a given temperature between 250 and 310°C, the growth rate was observed to be determined by the number of growth cycles, which is typical of atomic layer epitaxy (ALE). In spite of very large lattice mismatch (4.4%) between ZnS and GaAs, ZnS layers grown in an ALE mode showed good surface morphology and exhibited strong near-band-edge photoluminescence.
Thermal Relaxation of Strained SiGe/Si Heterostructure
Authors: Shigekawa Hidemi , Kanaya Hiroyuki , Cho Yukiko
Published: February 2005

The lattice strain of SiGe/Si relaxes upon annealing, but the relaxation speed decreases with time according to the change in the residual strain. This menchanism is expected to produce the metastability which has been observed in SiGe/Si strained structures. The deceleration process was interpreted comprehensively by the dislocation glide dynamics based on the thermal activation process, where the activation energy E depends linearly on the applied shear stress σ as high as ∼1 GPa. The stress dependence of the activation energy Δ
E/Δσ obtained experimentally was ∼2×10-28 m3.
80 K Superconductivity in Bi-Sr-Cu-O Thin Films
Authors: Adachi Hideaki , Ichikawa Yo , Hirochi Kumiko , Matsushima Tomoaki , Setsune Kentaro , Wasa Kiyotaka
Published: February 2005

High-T
c superconductivity near 80 K has been obtained in Bi-Sr-Cu-O thin films. Films were prepared by rf-magnetron sputtering onto heated MgO substrates and heat-treated. It was found that the Bi-based crystal structure with a c-axis length of 3.12 nm was formed in thin film. This film exhibited the superconducting transition with the onset temperature of about 80 K. The present superconducting phase in the Bi-Sr-Cu-O system is considered to be the isostructure with the conventional 80 K Bi2Sr2CaCu2O
y
(2-2-1-2) phase.
Measurements of the CF Radical in DC Pulsed CF4/H2 Discharge Plasma Using Infrared Diode Laser Absorption Spectroscopy
Authors: Magane Mitsuo , Itabashi Naoshi , Nishiwaki Nobuki , Goto Toshio , Yamada Chikashi , Hirota Eizi
Published: February 2005

Infrared diode laser absorption spectroscopy (IRLAS) was established as the measurement method for the CF radical density. The absolute density of the CF radical and its pressure dependences were measured in DC pulsed CF4/H2 discharge plasma. Moreover, from the analysis of the decay parts of the observed transient absorption waveforms of the CF radical, the CF radical was shown to be removed mainly by a diffusion process in the present plasma, yielding the diffusion coefficients D(CF in H2) and D(CF in CF4).
Measurement of Dipole Matrix Element of Atomic Gd Transitions using Rabi Flopping
Authors: Adachi Satoru , Niki Hideaki , Izawa Yasukazu , Nakai Sadao , Yamanaka Chiyoe
Published: February 2005

Dipole matrix elements were measured for two transitions of the gadolinium atom by detecting the laser-induced fluorescence as a function of laser intensity using Rabi flopping. Those values are 2.7×10-19 and 3.0×10-19 esu ·cm for 9D2-9F2(0–17381 cm-1) and 9D5-9D4(999–17931 cm-1), respectively. Optical Bloch equations for two-level atoms were calculated for each pair of magnetic sublevels, where the effects of inhomogeneous broadening and laser intensity fluctuation were included. Experimental results were well described by this model. This method is very useful for determining a dipole matrix element which is one of the basic parameters for laser isotope separation.
Novel Temperature-Dependent Junction Characteristics of Poly(3-alkylthiophene) Schottky Diodes
Authors: Ohmori Yutaka , Manda Yasuhisa , Takahashi Hiroyuki , Kawai Tsuyoshi , Yoshino Katsumi
Published: February 2005

Electrical characteristics of poly(3-alkylthiophene) and metal interfaces have been studied. Good Schottky type diodes have been fabricated using aluminum and gold-tin electrodes vacuum-evaporated onto poly(3-alkylthiophene) films. Markedly large temperature dependences are observed for poly(3-alkylthio-phene) Schottky diodes and discussed in terms of a temperature-dependent electronic band scheme.
Thermally Stimulated Currents in Epitaxially Grown Tin Selenide Films
Authors: Singh J. P. , Bedi R. K.
Published: February 2005

Thermally stimulated currents (TSC) have been measured in the structures containing a monocrystalline tin selenide film grown by Hot Wall Epitaxy technique. The results indicate a total trap density of the order of 1018–1019 cm-3. It is observed that trap density increases with decrease in film thickness. Decayed TSC results suggest trapping energies over a range of values upto 0.18 eV.
Softening of Cu(1)-Site Vibration Matched with the Onset Temperature of Superconducting YBa2(Cu0.995Sn0.005)3O6.60
Authors: Nishida Tetsuaki , Katada Motomi , Arakawa Tsuyoshi , Matsumoto Yasukuni
Published: February 2005

The 119Sn-Mössbauer spectrum of superconducting YBa2(Cu0.995Sn0.005)3O6.60 ceramic, prepared by quenching at 815°C, consists of an intense singlet peak due to square planar Cu(Sn)O4 and a weak doublet due to triangular Cu(Sn)O3. The absorption area increases linearly with decreasing temperature and becomes constant below the onset temperature of superconducting transition (ca. 60 K). This indicates that the mean square displacement <u
2 > of the Cu(1)-site vibration becomes constant, as was observed below 95 K in the YBa2(Cu0.995Sn0.005)3O7-y
system (y\fallingdotseq0.15). The decrease of T
c is ascribed to the displacement of O(4) atoms from the c-axis.
First Order Paraelectric-Antiferroelectric Phase Transition in a Chiral Smectic Liquid Crystal of a Fluorine Containing Phenyl Pyrimidine Derivative
Authors: Inui Shiroh , Kawano Shin , Saito Masaki , Iwane Hiroshi , Takanishi Yoichi , Hiraoka Kazuyuki , Ouchi Yukio , Takezoe Hideo , Fukuda Atsuo
Published: February 2005

The first-order phase transition between paraelectric SmA and antiferroelectric SmCA
* phases has been observed for the first time in (S)-4-(1-trifluoromethylheptyloxycarbonyl)phenyl 4-(5-dodecyloxypyrimidin-2-yl)benzoate (TFMHPDOPB). Three pieces of evidence for the first-order phase transition are shown by means of DSC, X-ray and dielectric measurements. The DSC peak of the SmA-SmCA
* transition is as large as the one for the Iso-SmA transition. The temperature dependences of the interlayer spacing determined by X-ray diffraction and of the dielectric constant reveal marked discontinuous jumps at the SmA-SmCA
* phase transition.
Thickness Dependence of Infrared Reflection Absorption in Vacuum-Deposited Thin Film of Polyvinylidene Fluoride
Authors: Maki Kunisuke , Terashima Hidenobu , Kikuma Kazuhiro
Published: February 2005

Reflection absorption intensities for p-polarized infrared rays are shown as a function of thickness (d) of vacuum-deposited films of polyvinylidene fluoride (PVDF), which were deposited on Ag-covered mica substrates held at 25°C. Each absorption due to α-type polycrystalline film at 1412, 1215, 1185, 1150, 1070, 875 and 615 cm-1 increases linearly with increasing d. Some structural relaxation during the growth of PVDF film is discussed for interpretation of the result that absorption at 1215, 1185 and 875 cm-1 is not observed and the peak height at 882 cm-1 is seen clearly for films at d<15 nm.
Epitaxial Growth and Electrical Properties of Ferroelectric Pb(Zr0.9Ti0.1)O3 Films by Reactive Sputtering
Authors: Okamura Takeshi , Adachi Masatoshi , Tadashi Shiosaki Tadashi Shiosaki , Akira Kawabata Akira Kawabata
Published: February 2005

Ferroelectric Pb(Zr0.9Ti0.1)O3 thin films have been successfully obtained on the pt/(0001)sapphire substrates and the Pt/SiO2/(100)Si substrates by reactive sputtering of the multimetal target. The films with perovskite structure have been grown at substrate temperatures of 600-620°C. The epitaxial films have been obtained on the Pt/(0001) sapphire substrates and the oriented. films have been obtained on the Pt/SiO2/(100)Si substrates. The crystallinity of the Pb(Zr0.9Ti0.1)O3 film depended on the substrate temperature and the crystallinity of the platinum film used as the bottom electrode. The films showed ferroelectricity, and the switching speed was measured as 50 ns at 8 V for the 0.60 µm film on the Pt/SiO2/(100)Si substrate.
Damage Induced by Electron Cyclotron Resonance Plasma Etching on Silicon Surface
Authors: Washidzu Gen , Hara Tohru , Hiyoshi Jun , Sasaki Masami , Suzuki Yasuhiro , Ukai Katsumi
Published: February 2005

Physical and electrical damage induced on silicon surfaces by electron cyclotron resonance (ECR) plasma etching is studied. In sulfurhexalluoride (SF6) plasma etching, shallow (less than 750 Å) electrical damage is induced in the surface. Damage density increases markedly with the increase of microwave power. Deeper (1 µm) damage is formed when radio frequency (RF) bias power is added. This damage can be eliminated by annealing at 200°C. In Ar plasma etching, however, thin (∼80 Å) physical damage is induced.
Epitaxially Grown Diamond (001) 2×1/1×2 Surface Investigated by Scanning Tunneling Microscopy in Air
Authors: Tsuno Takashi , Imai Takahiro , Nishibayashi Yoshiki , Hamada Kotaro , Naoji Fujimori Naoji Fujimori
Published: February 2005

Scanning tunneling microscopy (STM) observation was performed for the surface of diamond epitaxial film which was grown on a diamond (001) substrate by microwave plasma-assisted chemical vapor deposition (CVD). The surface was stable even in air, and it showed a reflection high-energy electron diffraction (RHEED) pattern of the 2×1/1×2 structure. Images of the atomic level corresponding to the RHEED pattern were obtained by STM in air. Significant extension of dimer rows was observed over the entire surface. Strong similarity between Si(001) grown by molecular beam epitaxy (MBE) and diamond (001) grown by CVD was shown.
Rate-Equation Analysis of Optogalvanic Effect in CO2 Laser Medium
Authors: Maki Tachikawa Maki Tachikawa , Tadao Shimizu Tadao Shimizu
Published: February 2005

We propose a novel rate-equation model to describe the optogalvanic effect in a CO2 laser medium. In this model, the spontaneous emission from the upper laser level and the translational energy dissipation in the gas medium are included in addition to the vibrational relaxation processes. The calculation quantitatively reproduces the characteristic dependence of the optogalvanic signal on the modulation frequency of the incident laser beam and the gas pressure. The vibration-to-translation relaxation rates of the upper and lower laser levels are determined.
A Novel Optical Lithography Technique Using the Phase-Shifter Fringe
Authors: Tanaka Toshihiko , Uchino Shouichi , Hasegawa Norio , Yamanaka Toshiaki , Tsuneo Terasawa Tsuneo Terasawa , Shinji Okazaki Shinji Okazaki
Published: February 2005

A new optical lithography technique called outline pattern transfer imaging (OPTIMA) is described. OPTIMA utilizes an optical phase change at a clear phase-shifter pattern edge. Very narrow closed patterns can be delineated along the fringe of the phase-shifter pattern by this method. The resolution limitation of OPTIMA is presented using a newly developed high-resolution i-line negative resist. The resist is transparent (90% at 0.5 µm thickness) and has a high γ value (4.5). Results show that 0.13 µm-wide groove patterns can be delineated with an i-line stepper having 0.42 numerical aperture. Practical focus latitude and exposure latitude are obtained for 0.2 µm patterns. In OPTIMA, linewidth control is also possible by adding notch patterns at the shifter edge.
Low-Concentration Cadmium Diffusion into GaAs
Authors: Gautam Dinesh Kumar , Yoshiaki Nakano Yoshiaki Nakano , Kunio Tada Kunio Tada
Published: February 2005

Experimental results to obtain low p-type surface concentration into GaAs at high temperature using Ga-Cd alloy as a diffusion source, for the fabrication of a bipolar transistor optical switch, have been presented for the first time. The values of the diffusion coefficient of different proportions of cadmium into the alloy source are measured. The diffusion constant, D
0, and the activation energy, ε, for pure cadmium and 1% cadmium into the Ga-Cd alloy as a source have also been measured. The modified values of these parameters for pure cadmium seem to be different as compared to the data reported earlier due to the SiO2 thin film deposited on the surface of the substrate to prevent arsenic loss at high temperature. The experimental results show a continuous reduction in surface concentration and diffusion coefficient by reducing the percentage quantity of cadmium into the Ga-Cd alloy diffusion source.
High-Output Power and Fundamental Transverse Mode InGaAs/GaAs Strained-Layer Laser with Ridge Waveguide Structure
Authors: Takeshita Tatsuya , Masanobu Okayasu Masanobu Okayasu , Shingo Uehara Shingo Uehara
Published: February 2005

Low-threshold, high-efficiency and high-output-power operation is achieved in an InGaAs/GaAs strained-layer ridge waveguide. A light output power of 80 mW for fundamental transverse mode, and 270 mW for higher-order transverse mode lasers have been obtained.
Lyotropic Liquid Crystalline Structures of Synthetic Polypeptide 2. Measurements of Elastic Constants and Coupling Constants of Poly(γ-Benzyl L-Glutamate) Solutions by the Freedericksz Transition
Authors: Itou Satoshi , Tozaki Ken-ichi , Komatsu Naoki
Published: February 2005

The object of this report is the determination of material parameters of the lyotropic polymer liquid crystal, poly(γ-benzyl L-glutamate)-1,1,2-trichloroethane solutions, by means of the Freedericksz transition with the magnetic field. The critical field strength H
c of the homeotropic polymer liquid crystal was determined in the condition without hysteresis. The bend elastic constant K
33=1.3-1.0×10-11 N and the coupling constant B=4.4×10-6 J m-2 (weight fraction of polymer, w
2=0.173 and 0.138) were obtained from the relations between H
c and the cell thickness. The splay elastic constant K
11=1.6×10-11 N (w
2=0.173 and 0.138) was obtained by the simulations of the transition curves. The ratio K
11/K
33 exceeds one and is larger than those of the small molecular liquid crystal.
Preparation of Cu-O Films by Electron Cyclotron Resonance Plasma-Assisted Sputtering
Authors: Fujii Takamichi , Anno Toshihiko , Koyanagi Tsuyoshi , Hidetoshi Hirai Hidetoshi Hirai , Kakuei Matsubara Kakuei Matsubara
Published: February 2005

Preparation of Cu-O films has been performed by using electron cyclotron resonance (ECR) plasma-assisted sputtering, and the effects of activated species in the ECR plasma on the properties of Cu-O films have been investigated from measurements of the optical emission spectroscopy. The emission intensities from O2
+ molecular ions and O* atomic radicals in the ECR oxygen plasma increase monotonously with increasing microwave power of the ECR plasma source. The oxygen content of Cu-O films can be successfully controlled by changing the microwave power of the ECR plasma source. These results suggest that the role of the activated species of oxygen is important in oxidization of Cu atoms.
Analysis of Sputtered Neutrals by Nonresonant Multiphoton Ionization. III. Change of the Velocity Distribution with Time after Sputtering
Authors: Eizoh Kawatoh Eizoh Kawatoh , Ryuichi Shimizu Ryuichi Shimizu
Published: February 2005

The nonresonant multiphoton ionization technique was applied to the composition analysis of Cu-Ni (52 at.%) alloy to verify the capability for quantitative surface characterization. It has been revealed that the intensities of Cu- and Ni-sputtered neutrals from the pure and alloy samples represented a rapid change after high-current ion bombardment was stopped. This suggests that the Ar atoms implanted in the surface during Ar+ ion bombardment caused a considerable change of the surface binding energy, resulting in the change of the velocity distributions of the photoionized neutrals.
Transverse Magnetic (TM) Guided-Transverse Electric (TE) Radiation Mode Conversion in Proton-Exchanged Z-Cut LiNbO3 Waveguides
Authors: Endoh Hiroaki , Yoshihiro Sampei Yoshihiro Sampei , Yoshihide Miyagawa Yoshihide Miyagawa
Published: February 2005

The mechanism of transverse magnetic (TM) guided to transverse electric (TE) radiation mode conversion losses in proton-exchanged z-cut LiNbO3 waveguides was investigated experimentally. These mode conversion losses are caused by strains in the proton-exchanged regions. To clarify the mechanism, the influence of both external electric fields and propagation directions on the conversion efficiencies were measured, and a model of the strain induced by proton exchange is presented.
Hydrogen Analysis of the Surface Layers in Sodium β′′-Alumina Crystals by using Elastic Recoil Detection Technique
Authors: Fernando Lázaro Freire Jr. Fernando Lázaro Freire Jr.
Published: February 2005

Hydrogen depth profiles have been determined by 2.2 MeV 4He+-Elastic Recoil Detection (ERD) for sodium β′′-alumina crystals submitted to thermal annealing in dry atmosphere or ion implantation. The results demonstrate the usefulness of this technique as an auxiliary tool for the analysis of water retention by these crystals. Simultaneous Rutherford Backscattering (RBS) Spectrometry analysis were also made.
Evaluation of Internal Stress in Reactively Sputter-Deposited ZrN Thin Films
Authors: Ping Jin Ping Jin , Shigeo Maruno Shigeo Maruno
Published: February 2005

The influence of preparation conditions (nitrogen flow ratio, total pressure and applied substrate bias) on the internal stress of ZrN films deposited on a Si substrate was investigated by means of the substrate deflection method. The film microstructure was also examined by high-resolution field emission scanning electron microscope (FE-SEM). Films deposited at relatively low pressure have a dense microstructure and a compressive stress of from 1.7 to 4.2 GPa dependent on the nitrogen flow ratio, while films deposited at high pressure have an open structure and the stress decreases to 0.3 GPa. The latter films are densified by applying a negative substrate bias, leading to high compressive stress of up to 6.5 GPa. It has been found that the stress is closely connected with the film microstructure, and oxygen impurities in the films have a relaxation effect on the compressive stress.
Electrical Characteristics of HoBa2Cu3O7-x-La1.5Ba1.5Cu3O7-y-HoBa2Cu3O7-x Junctions with Planar-Type Structures
Authors: Kabasawa Uki , Tarutani Yoshinobu , Fukazawa Tokuumi , Tsukamoto Akira , Masahiko Hiratani Masahiko Hiratani , Kazumasa Takagi Kazumasa Takagi
Published: February 2005

A HoBa2Cu3O7-x
-La1.5Ba1.5Cu3O7-y
-HoBa2Cu3O7-x
junction having a planar structure is fabricated and its electrical characteristics are investigated. The planar junction is formed by sectioning a HoBa2Cu3O7-x
layer into two superconducting electrodes keeping a submicrometer between them. Supercurrent is detected for the junction with an electrode spacing smaller than 0.4 µm. Critical current is exponentially dependent on electrode spacing. Superconducting decay length for the La1.5Ba1.5Cu3O7-y
layer is 65 nm and is almost independent of temperature up to 70 K. This extraordinary long decay length and anomalous superconducting characteristics are not shown to be explained by the conventional proximity theory, and phenomenologically outlined.
Phase-Matching of Optically Second-Harmonic Generation in the Single Crystals of Gd- and La-Added Barium Sodium Niobate
Authors: Shimazu* Masaji , Tsukioka Masayuki , Kuroiwa Shinichiro , Tanokura Yasuo , Tsutsumi Sadao
Published: February 2005

Optically microscopic observation, measurements of the phase-matching temperature of second-harmonic generation (SHG) and evaluation of the SHG conversion efficiency were carried out for three kinds of single crystals: barium sodium niobate (BNN), La-added BNN [BN(La)N] and Gd-added BNN [BN(Gd)N]. The best crystalline-quality crystal was [BN(Gd)N] and the crystal showing the highest SHG conversion efficiency was also [BN(Gd)N]. The phase-matching temperatures were about 120°C and 160°C. Some discussion was given on the SHG phase-matching.
The Determination of the Deformation Potential Constant of the Conduction Band in InSb by the Electron Mobility in the Intrinsic Range
Authors: Kunio Tukioka Kunio Tukioka
Published: February 2005

The electron Hall mobility in InSb has been measured at 200∼430 K by van der Pauw's method. The experimental data were compared with theoretical values calculated by an iteration technique with a variable parameter |E
l|. In the calculations, the temperature dependence of m
* was estimated from the experimental data of E
g(T) and m
*(0) on the basis of Ravich's theory, and the value of κs was taken to be 16.8 instead of κs∼17.5. The comparison between the theoretical and experimental values of µH led to the value of |E
l|=33 eV, which is more than two times larger than that obtained in a previous work.
Preparation and Switching Kinetics of Pb(Zr, Ti)O3 Thin Films Deposited by Reactive Sputtering
Authors: Takashi Hase Takashi Hase , Tadashi Shiosaki Tadashi Shiosaki
Published: February 2005

Ferroelectric Pb(Zr, Ti)O3[PZT] thin films have been prepared on Pt/Ti/SiO2/Si and Pt/SiO2/Si substrates using the reactive sputtering method with a metal composite target. The (111)-oriented PZT(80/20) thin films with a perovskite structure have been obtained at a substrate temperature of 595°C on highly (111)-oriented Pt films formed on SiO2/Si substrates. When an 8 V pulse sequence was applied to a 265 nm-thick film with an electrode area of 50×50 µm2, the switching time and the switched charge density measured were 20 ns and 10 µC/cm2, respectively. The switching time was strongly dependent on the electrode area.
Reactive Coevaporation Synthesis and Characterization of SrTiO3 Thin Films
Authors: Yamaguchi Hiromu , Shogo Matsubara Shogo Matsubara , Yoichi Miyasaka Yoichi Miyasaka
Published: February 2005

SrTiO3 thin films were prepared by the reactive coevaporation method, where the Ti and Sr metals were evaporated in oxygen ambient with an E-gun and K-cell, respectively. A uniform depth profile in composition was achieved by altering the Ti evaporation rate according to the Sr evaporation rate change. A typical dielectric constant of 170 was measured on films of 75 nm in thickness. The in-situ annealing in oxygen plasma reduced the leakage current.
Lead Perovskite Relaxor-Based Low-Loss Ceramic Dielectric for High-Voltage Ceramic Capacitors
Authors: Furukawa Osamu , Yohachi Yamashita Yohachi Yamashita , Mitsuo Harata Mitsuo Harata
Published: February 2005

A low-loss ceramic dielectric with a less than 0.1% dissipation factor at 100 kHz, based on a modified lead zinc niobate relaxor, has been fabricated by shifting the ferroelectric transition temperature (T
c) to below -55°C. This dielectric has a high dielectric constant (K), ranging from 250 to 2000. The temperature coefficient of capacitance (TCC) locates at the middle area between values for temperature compensation dielectric and values for high-K dielectric. Even at 150°C, high insulation resistance, more than 5×1013 Ωcm, was also retained. Moreover, a typical composition with K=530 revealed that the dielectric has a high breakdown voltage of 95 kV per 10 mm of thickness and a TCC value of -2900 ppm/°C. Accordingly, this dielectric has proven useful for high-voltage ceramic capacitors.
Ba(Mg, Ta)O3-BaSnO3 High-Q Dielectric Resonator
Authors: Matsumoto Hiroyuki , Hiroshi Tamura Hiroshi Tamura , Kikuo Wakino Kikuo Wakino
Published: February 2005

Dense ceramics with the chemical formula (1-X)Ba(Mg1/3Ta2/3)O3-XBaSnO3(X=0-0.15) are prepared for use as dielectric resonators. The obtained dielectric constant and Q value for Ba(Mg1/3Ta2/3)O3 were 24 and 43000 at 10 GHz, respectively. As X increased from 0 to 0.15, the temperature coefficient of resonant frequency decreased gradually from 5.4 to -0.5 ppm/ °C. At X=0.05, the Q value decreased drastically, and at X=0.10-0.15, the Q value increased to 33000 at 10 GHz. The specimens were investigated by scanning electron microscopy and X-ray diffraction analysis. It is found that Q improvement is not always dependent on the ordering structure of (1-X)Ba(Mg1/3Ta2/3)O3-XBaSnO3.
Fatigue Degradation and Reliability of Piezoelectric Ceramics
Authors: Toshio Tanimoto Toshio Tanimoto , Kiyoshi Okazaki Kiyoshi Okazaki
Published: February 2005

Reliability-based consideration of the fatigue degradation of piezoelectric ceramics has been performed in the present work. The material used for this work is a commercial piezoelectric ceramics with the composition of PbZrO3-PbTiO3 (PZT) including the third component Experimental studies were performed on the changes of mechanical and electrical properties of this material under repeated compression fatigue loading. In addition, a statistical residual strength degradation model was devised for this material and the validity of the proposed model was examined by comparison with a sufficient amount of test data. Good agreement has been observed between the experimental results and the theoretical prediction on the residual strength degradation.
Thermal Diffusivity of Crystalline and Liquid Silicon and an Anomaly at Melting
Authors: Yamamoto Katsuhiro , Abe Toshio , Shin-ichiro Takasu Shin-ichiro Takasu
Published: February 2005

The thermal diffusivity of Si was measured by a laser flash method up to 1723 K. SiC and fused quartz cells were prepared for the measurement on the melt. The thermal conductivities of the crystal and the melt at the melting point were determined to be 27.3±0.3 and 56±1 W/mK, respectively. It is suggested that a new (metastable) phase exists in a narrow temperature range just above the melting point. It irreversibly transformed to ordinary liquid metal. The new phase may have very low emissivity, and/or large specific heat.
Reflectance Spectroscopy of (GaP)n(GaAs)n/GaAs Atomic Layer Superlattices
Authors: Tsugunori Takanohashi Tsugunori Takanohashi , Masashi Ozeki Masashi Ozeki
Published: February 2005

Exciton-absorption transition in the GaP-GaAs atomic layer superlattices has been observed by reflectance spectroscopy. The absorption coefficients of the near-band-edge transition are as high as 1×105 cm-1.
Carrier Concentration in Quantum Wires Fabricated by Reactive Ion Beam Etching
Authors: Itoh Masayuki , Takashi Honda Takashi Honda , Kotaro Tsubaki Kotaro Tsubaki
Published: February 2005

High-quality quantum wires with a submicron width are fabricated by a combination of electron beam lithography and selective etching by reactive ion beam etching. The carrier concentrations in these wires are evaluated as a function of gate voltage by analyzing the magnetic depopulation effect observed in the quantum wire resistance. This analysis assumes a parabolic potential profile for the wire constriction. The quantum wire capacitance calculated from the carrier concentration agrees well with the capacitance measured by the 1-MHz capacitance meter. This agreement confirmes that the carrier concentration derived from the magnetoresistance gives a good estimation to the actual quasi 1-dimensional concentration.
Perpendicular Coercivity of Co-Cr Films
Authors: Uchiyama Yoichi , Sato Hiroshi , Yoshitaka Kitamoto Yoshitaka Kitamoto , Uee-Myung Hwang Uee-Myung Hwang
Published: February 2005

In order to explain the mechanism of the perpendicular coercivity of Co-Cr films, a new model of the microstress distribution has been established based on the structure observed elsewhere. The microstrain measured by an X-ray diffraction technique, the Warren-Averbach method, is considered to contribute to the perpendicular coercivity through the magnetostrictive effect upon magnetic wall displacement; then a relationship between the perpendicular coercivity and the microstrain is induced. The theoretical results are compared with experimental values of the perpendicular coercivity. In addition, the mechanism of the magnetization reversal is discussed.
Afterglow and Thermoluminescence of UV-Irradiated MgO Surfaces at Low Temperature
Authors: Yasunori Yanagisawa Yasunori Yanagisawa , Aki Narumi Aki Narumi
Published: February 2005

Afterglow emission and thermoluminescence are observed on UV-irradiated MgO powders at low temperatures of 140 K-300 K under high vacuum. The main peak of the TL spectrum is at 3.1 eV with a shoulder at about 2.3 eV. A plausible emission process is discussed in terms of the tunneling recombination of an electron of Fs
+ centers and a hole of Vs
- centers on the surfaces. The luminescence is quenched by O2 gas exposure at low temperature.
Thermochemical Kinetics of a Proposed Mechanism for Diamond Growth from Acetylene
Authors: Stephen J. Harris Stephen J. Harris , David N. Belton David N. Belton
Published: February 2005

We have performed a thermochemical and kinetic analysis of a previously proposed mechanism for diamond growth from C2H2. We estimate enthalpy and entropy changes for each step in the mechanism using the MM3 molecular mechanics code. Rate constants are estimated based on the assumption that reaction cross sections measured for analogous gas phase reactions may be applied to gas-surface reactions. Gas phase species concentrations are taken from measurements and modeling. The rate equations are then integrated. According to the analysis, each step in the proposed mechanism is exothermic (ΔH<0), but the reduction in entropy is so great that this mechanism does not produce diamond at a significant rate. This result does not rule out the possibility of growth from C2H2 by some different reaction mechanism.
Simultaneous Measurement of Surface Profile and Ultrasonic Transmission Profile by Ultrasonically Vibrated Diamond Tip
Authors: Yasuda Kyosuke , Shigemitsu Oguchi Shigemitsu Oguchi , Reizo Kaneko Reizo Kaneko
Published: February 2005

An ultrasonically vibrated diamond tip was used to simultaneously measure the surface profile and obtain the ultrasonic transmission profile of a sample. The ultrasonic transmission amplitude varied with the hardness of the sample surface and with the contact condition between the tip and the sample surface.
Dielectric and X-Ray Diffraction Study on the Additional Relaxation below the Curie Point of Vinylidene Fluoride-Trifluoroethylene Copolymers
Authors: Ogura Hiroshi , Tohriyama Satoru , Hanaki Atsushi , Sasaki Sunao , Chiba Kunio Kase
Published: February 2005

In the dielectric relaxation curves measured for P(VDF/TrFE): poly(vinylidene fluoride and tritluoroethylene) copolymers, additional anomalies appear below the Curie transition. These additional anomalies are sensitive to thermal history, and the samples annealed above the melting point show the remarkable effect. The observed phenomena are discussed in terms of molecular interactions with structural disorder in the phase transition.
Transmission-Loss Spectra of Chalcohalide Se-Te-I Glass Fibers and Its Delivery of CO2 Laser Power
Authors: Inagawa Ikuo , Takashi Yamagishi Takashi Yamagishi , Toshiharu Yamashita Toshiharu Yamashita
Published: February 2005

Chalcohalide Se-Te-I glass fibers have been investigated. The glasses stable against crystallization were found in the region of Se20-70Te10-40I20-45 (at.%). Unclad fibers were prepared by the pressurized crucible fiber-drawing method. The lowest transmission loss of 0.9 dB/m at 10.6 µm wavelength, which is lower than that of previously reported chalcogenide glass fiber, was achieved for the Se25Te30I45 glass fiber. The maximum CO2 laser power delivered through a fiber of 400 µm in diameter and 1 m in length was only 0.8 W. Both the absorbance increments with temperature and the low glass transition temperature of this glass have imposed a limitation on its deliverable power.
SHG-Active Polymorphism of p-Nitroaniline Mixed with Its N-Alkyl Derivatives
Authors: Tasaka Shigeru , Abe Takashi , Matsushima Ryoka , Suzuki Morio , Chen Ding Yu , Okamoto Naomichi
Published: February 2005

The second-harmonic generation (SHG) in each mixture of p-nitroaniline (p-NA) and its derivatives (n-methyl, n-ethyl, n-propyl, i-propyl, n-butyl, n-hexyl, dimethyl, phenyl, and diethyl-4-nitroaniline) was measured by the powder method with a Nd:YAG laser. Most of the mixtures having a typical eutectic phase diagram exhibited a high SHG intensity; in particular, the SHG activity of the p-NA/isopropyl-NA mixture was 1670 times higher than that of urea. This may be due to the crystal growth of noncentrosymmetrical polymorphism of p-NA on the surface of the isopropyl-NA. The crystal growth of the SHG-active polymorphism was accomplished by vacuum deposition on the isopropyl-NA substrate.
Proposal of the New Thermally Stimulated Current Curve Having a Straight Line Passing through the Origin
Authors: Shigeyoshi Maeta Shigeyoshi Maeta , Hiroaki Suzuki Hiroaki Suzuki
Published: February 2005

A new theory of a thermally stimulated current (TSC) curve of the first order which has a straight line passing through the origin of the new coordinates of the A-B plane is proposed for the first time from the original concept of “the fundamental element”. The key functions of A and B are originally defined and proposed. The theory is very simple and the energy depth of the carrier trap E

t
can accurately be revealed from the slope of the new TSC curve as the essential parameter. All coordinates of the usual TSC curve are freely digitized and accurately transformed to a series of fundamental elements, and they create two clear standards, the “origin” as the reference point and the “straight line”. Then, several TSC curves can be put on the origins of one another in the new TSC curve, and all fundamental elements make directly possible the detailed comparison of various TSC curves.
Assessment of Signal Detectability for Conventional and Reversal-Processed Medical X-Ray Films Obtained without Intensifying Screens
Authors: Kariya Hiroshi Inatsu
Published: February 2005

The detectability of the conventional and reversal-processed images obtained without intensifying screens was assessed by using the maximum information content (I
max) generated from receiver operating characteristic (ROC) curve data and the noise-equivalent number of quanta (NEQ). It was demonstrated, from the I
max values versus background density, that reversal-processed images have a very high detectability at lower density levels, but exhibit a rapid decrease in detectability at higher density levels. On the other hand, the detectability of conventional images was not as strongly affected by the density. Therefore, the detectability of both conventional and reversal-processed images varies with the density, and conventional images are superior to reversal-processed images at higher densities. This was confirmed by measureing the NEQ.
Photolithography System Using Annular Illumination
Authors: Kamon Kazuya , Miyamoto Teruo , Myoi Yasuhito , Nagata Hitoshi , Tanaka Masaaki , Horie Kazuo
Published: February 2005

Photolithography is a leading technique in LSI device fabrication. The LSI pattern size has approached the exposure wavelength such as the g or i-line of a Hg lamp. This fact indicates that the shorter wavelength or some novel technique will be needed in order to cope with finer patterns. It is known that annular illumination can improve the depth of focus and resolution. We applied the annular illumination method to the step and repeat exposure system. Experiments and simulations using annular illumination were carried out and subhalf-micron patterns were produced. The process latitudes of the annular illumination method are evaluated.