bluuebunny/crossref_metadata_2025 huggingface dataset:
Resist and Sidewall Film Removal after Al Reactive Ion Etching (RIE) Employing F+H2O Downstream Ashing
Authors: Jimbo Sadayuki , Shimomura Kouji , Ohiwa Tokuhisa , Sekine Makoto , Mori Haruki , Keiji Horioka Keiji Horioka , Haruo Okano Haruo Okano
Published: February 2005

The sidewall residue seen after Al etching and via-hole etching on an Al pattern was investigated. X-ray photo-electron spectroscopy (XPS) after O2 plasma ashing revealed that this sidewall residue contained a large number of Al atoms sputtered from the Al film surface. A downstream ashing technique employing F atoms and water vapor has already been developed to remove the persistent resist after plasma processing or ion implantation, but even this downstream ashing could not remove the sidewall residue containing Al. It has been found that the downstream process changed Al and Al oxide in the residue to Al fluoride, a water-soluble compound. Thus, rinsing with DI water successfully removed the sidewall residue after downstream ashing.
Evaluation of Radiation Damage on Electrical Characteristics of SiO2 due to Reactive Ion Etching
Authors: Tsukamoto Akira , Mizushima Kazuyoshi , Hidaka Yoshiharu , Hiroyuki Okada Hiroyuki Okada , Sumio Terakawa Sumio Terakawa
Published: February 2005

Electrical characteristics of SiO2 are degraded due to reactive ion etching (RIE) radiation damage. We prepared metal-oxide-semiconductor (MOS) diode samples with plasma-exposed SiO2 film. Degradation of MOS diode characteristics was examined under several plasma conditions. Initial C-V measurement and B-T aging test show the RF power dependence of the radiation damage. The V
th shift increases with RF power. The V
th shift depends not on the plasma exposure time, but on the residual oxide thickness after plasma exposure. According to I-V measurement, trapped negative charge density increases with increasing RF power. The depth of the trapped charge centroid is proportional to V
dc
1/2. Neutral and charged traps are generated in SiO2 due to ion bombardment.
Growth Kinetics and Behavior of Dust Particles in Silane Plasmas
Authors: Yukio Watanabe Yukio Watanabe , Masaharu Shiratani Masaharu Shiratani
Published: February 2005

Growth kinetics and behavior of dust particles in silane plasmas are studied using a new method combining an rf discharge modulation technique with two laser light scattering techniques. From the experiments, the following results are obtained: dust particles tend to be sustained around plasma/sheath boundaries near electrodes, especially the rf electrode; dust particles of a larger size exist in a lower space potential region near the rf electrode; dust size and density amount to 60∼180 nm and 108∼109 cm-3 in 1∼2 s after the rf-power-on. The dust growth rate, which is high compared to the film deposition rate, can be explained by taking into account the contribution of positive-ion and/or neutral radical fluxes. The dust-trapping around the boundary can be explained by the balance between the electrostatic force and the ion drag force exerting on the particle. The effects of gas flow on dust motion and a dust suppression mechanism for rf modulated discharges are also discussed.
Formation of Single-Crystal Al Interconnection by In Situ Annealing
Authors: Wada Jun-ichi , Suguro Kyoichi , Nobuo Hayasaka Nobuo Hayasaka , Haruo Okano Haruo Okano
Published: February 2005

A new process for forming Al interconnections on amorphous insulators such as SiO2 is proposed in this paper. Al thin films were found to agglomerate at temperatures below the melting point and to fill the grooves on a SiO2 layer by in situ annealing in which native oxide is only minimally formed on the Al surface. In sufficiently deep grooves, single-crystal Al interconnections were successfully formed without used of Al dry etching. It has been clearly confirmed by acceleration testing that single-crystal Al interconnections formed by means of the present process have excellent endurance against electromigration compared with conventional poly-crystal interconnections.
Fluorine Termination of Silicon Surface by F2 and Succeeding Reaction with Water
Authors: Nakamura Masakazu , Takayuki Takahagi Takayuki Takahagi , Akira Ishitani Akira Ishitani
Published: February 2005

The F2 treatment of a hydrogen-terminated Si(100) surface in a vacuum chamber was chosen to generate a densely fluorinated silicon surface. It was confirmed by IR-attenuated total reflection and X-ray photoelectron spectroscopy measurements that the Si-H bonds on the surface were replaced with the Si-F bonds and that 1.0 monolayer of the Si-F bonds was formed after 1×104 L exposure. Mass spectrometry measurements of the volatile reaction products indicated that the Si-F bonds were produced by the following reaction: {SiH(surface)+F2(gas)→Si-F(surface)+HF(gas)}. The variation of thus prepared surface in water was also studied. The 1.0 monolayer of Si-F bonds was found to be replaced with the 0.7 monolayer of Si-H bonds and the 0.2-0.3 monolayer of Si-OH bonds after dipping into water for 1 min. The replacement of the Si-F bonds with the Si-H bonds was considered to be the back-bond-breaking reaction by water. Such a reaction between water and the surface Si-F was observed for the first time.
Vector Diffraction Modeling: Polarization Dependence of Optical Readout/Servo Signals
Authors: Kiyoshi Kobayashi Kiyoshi Kobayashi
Published: February 2005

Analytic formulae are derived for the incident polarization dependence of a light field reflected from an optical disk with embossed pits and grooves, on the basis of a vector diffraction theory using the mode expansion technique. The proposed formulation is applied to a bi-periodic structure suitable as a basis for discussion of the tracking servo and readout signals' dependence on incident polarization and disk geometry. Numerical results are also given and compared both with the results obtained by using a scalar diffraction model and with experimental data. Theoretical results on the polarization and depth dependence of servo-related signals agree fairly well with experimental data.
Optical Studies of CaS:Eu, Sm Infrared Stimulable Phosphors
Authors: Yasuaki Tamura Yasuaki Tamura , Atsushi Shibukawa Atsushi Shibukawa
Published: February 2005

The photoluminescence (PL) and infrared stimulated luminescence (ISL) spectra of CaS:Eu,Sm infrared stimulable phosphors (ISPs) are studied. In addition, the concentration dependence of ISL intensity is examined. Sm3+- and Eu2+-related structures are found in both the PL excitation and emission spectra. Two types of Sm3+ are found, one of which exhibits strong emission at around 650 nm and the other, weak emission compared to the other emissions at around 565 nm and 605 nm. These are assigned to an asymmetric and a symmetric site, respectively. ISL excitation spectra coincide with the Eu2+ 4f7 to 4f65d1 and 4f66s1 transitions and range from 220 to 650 nm. ISL emission spectra coincide with the Eu2+ 4f65d1 to 4f7 transition and range from 550 to 750 nm. ISL stimulation spectra range from 0.8 µm to 1.7 µm and are thought to indicate the Sm2+ ion transition from 4f6 to 4f55d1. The maximum ISL intensity is obtained from a sample with Eu and Sm concentrations of 500 and 130 ppm, respectively.
Surface Phonon Dispersion Curves of NiAl(111)
Authors: Kitamura Kazuo , Nagao Tadaaki , Osaka Toshiaki , Franchy Rene , Oshima Chuhei
Published: February 2005

The surface phonon dispersion curves of the NiAl(111) surface have heen measured along \overlineΓK of the two dimensional Brillouin zone by means of high-resolution energy loss spectroscopy. The observed dispersion curves were compared with lattice dynamical calculations of a slab shaped crystal on the basis of a force constant model including up to the third nearest-neighbor interaction. Good agreement between the experimental and calculated curves was obtained for two different combinations of the surface force constants, which suggests the existence of two different models concerning the surface atomic relaxation.
Area Variation of Merocyanine Monolayer at the Air-Water Interface during Adsorption of Brilliant Green Dye
Authors: Hiroshi Yageta Hiroshi Yageta , Kazuhiro Kudo Kazuhiro Kudo
Published: February 2005

The area variation of merocyanine monolayers during the adsorption of brilliant green dye from the water subphase is investigated. A marked area expansion which depends on the surface pressure is observed. The experimental results demonstrate that the adsorption of water-soluble dyes to the monolayer can be controlled by choosing proper substituents of the dyes and the surface pressure of the monolayer.
Density Fluctuations Associated with Electromagnetic Waves in Ion Cyclotron Range of Frequencies
Authors: Hojo Hitoshi , Mase Atsushi , Katsumata Ryota , Inutake Masaaki , Akiyosi Itakura Akiyosi Itakura , Makoto Ichimura Makoto Ichimura
Published: February 2005

An expression for density fluctuations associated with electromagnetic waves in the ion cyclotron range of frequencies is obtained from the linearized Vlasov equation. The ratio of density to magnetic field fluctuations is discussed in connection with the reflectometer measurement in GAMMA 10.
High-Resolution Spectroscopy of Rubidium Atoms
Authors: Kim Seung-Sub , Park Sang-Eon , Lee Ho-Seong , Oh Cha-Hwan , Park Jong-Dae , Cho Hyuck
Published: February 2005

With a linewidth-narrowed diode laser system oscillating at 780.1 nm, the hyperfine structures of the 85Rb D2 line were observed extensively under various conditions. The results obtained with shielding of the geomagnetic field agree well with existing theory. It was also found that the hyperfine spectra are very sensitive to the geomagnetic field and that the sign of the resonance changes under the influences of the geomagnetic field and the change in laser power.
Translational-Energy-Dependent Emission Cross Sections of Excited Hydrogen Atoms Produced in Electron-Methane, Ethane, Ethylene and Acetylene Collisions
Authors: Yonekura Nobuaki , Tsuboi Toshiyuki , Tomura Hideaki , Nakashima Keiji , Junichi Kurawaki Junichi Kurawaki , Teiichiro Ogawa Teiichiro Ogawa
Published: February 2005

Translational-energy dependence of emission cross sections was measured for H
* (n=4) produced in collisions of methane, ethane, ethylene and acetylene with electrons through analysis of Doppler profiles of the Balmer-β line. Emission cross sections were calculated for the translational energies of 0-2, 2-4, 4-6, 6-8 and >8 eV. The translational-energy dependences of emission cross sections are similar for the four hydrocarbons. The five segments can be classified into 3 groups. The first group, 0-2 eV, is dominant at lower electron energies. The second group, 2-4 and 4-6 eV, is dominant above 40 eV. The third group, 6-8 and >8 eV, has some contribution at higher electron energies.
Novel Silicon-Containing Negative Resist for Bilayer Application in Electron Beam Direct Writing
Authors: Hashimoto Kazuhiko , Masayuki Endo Masayuki Endo , Masaru Sasago Masaru Sasago
Published: February 2005

A silicon-containing negative resist for bilayer application in electron beam (EB) direct-writing lithography has been developed. This newly developed EB resist comprises of alkaline soluble ladder type polysiloxane and trichloromethyl triazine. This negative EB resist has a high sensitivity of below 10 µC/cm2, along with a high resolution capability. Using this resist 0.2 µm line and space patterns were clearly delineated, and 0.2 µm rule device patterns were also successfully fabricated. The etching selectivity ratio of this negative resist against the novolak resin in an oxygen plasma was greater than 50, due to its high silicon content. High fidelity pattern transfer could be obtained by using it as a mask of silicon-containing negative resist patterns in a bilayer resist process.
Study of Applicability of AC Photovoltaic Method and Photoconductive Decay Method Using Microwaves as Noncontact Methods for Bulk Lifetime Measurement
Authors: Toda Masato , Yutaka Kitagawara Yutaka Kitagawara , Takao Takenaka Takao Takenaka
Published: February 2005

The applicability of the ac photovoltaic method and photoconductive decay method using microwaves (µ-PCD method) as bulk lifetime measurement methods were studied. Lifetimes measured by these two methods were compared with bulk lifetimes measured by the photoconductive decay method standardized by ASTM:F28-75. Lifetimes measured by the ac photovoltaic method were in good agreement with the bulk lifetimes of less than 3 ms for both n-type and p-type samples. However, lifetimes measured by the µ-PCD method were significantly lower than the bulk lifetimes. It is concluded that the ac photovoltaic method is a reliable noncontact method for the bulk lifetime measurement of the samples with bulk lifetimes less than 3 ms.
Sub-100-nm-Resolution Zone Plate Soft X-Ray Microscope Using Undulator Radiation
Authors: Kagoshima Yasushi , Wang Jidong , Ando Masami , Aoki Sadao , Anderson Erik , Attwood David , Kern Dieter
Published: February 2005

A high-resolution soft X-ray microscope has been constructed using a Fresnel zone plate (FZP) as its objective and undulator radiation as its source. The FZP used has the outermost zone width of 50 nm corresponding to theoretical spatial resolution of 60 nm as a microscope. An experiment has shown that the microscope attained resolution better than 100 nm.
Dislocations and Tungsten Concentration Profiles in Tungsten-Silicon Contact Areas
Authors: Aoyama Takashi , Koike Yoshihiko , Suzuki Masayuki , Yutaka Misawa Yutaka Misawa , Takaya Suzuki Takaya Suzuki
Published: February 2005

Dislocation formation and impurity distributions in metal-silicon contact areas were investigated by means of cross-sectional transmission electron microscopy (TEM) images and energy-dispersive X-ray measurement. Dislocations were formed in the (111) plane in the [110] direction by annealing at 700°C when W was used as barrier metal. As the diameter of contact holes decreased, dislocations became more significant. Both W and As concentration profiles in the horizontal direction showed maxima at the edges of contact holes. The diffusion length of W in the edge areas was about twice that in the center according to depth profile. This implied that stress in edge areas increased the W diffusion coefficient by a factor of about four.
Spectral Observation of As-Stabilized GaAs Surfaces in Metal-Organic Chemical Vapor Deposition Using Surface Photo-Absorption
Authors: Yamauchi Yoshiharu , Kunihiko Uwai Kunihiko Uwai , Naoki Kobayashi Naoki Kobayashi
Published: February 2005

The spectral dependencies of As-stabilized (001) GaAs surfaces in metal-organic chemical vapor deposition (MOCVD) are measured using the surface photo-absorption (SPA) method and compared them with those obtained in molecular beam epitaxy (MBE). The SPA spectrum of an As-stabilized surface at 600°C is anisotropic in regards to the perpendicularly intersecting incidence azimuths, [110] and [1̄10], of the monitoring light. It is also very similar at a arsine partial pressure of 4 Pa, which is a common MOCVD growth condition, to the spectrum obtained for an MBE As-surface having a c(4×4) reconstruction pattern in reflection high-energy electron diffraction (RHEED) observation, though not to the spectrum corresponding to a(2×4) pattern. Below 500°C, an isotropic signal appears and overlaps with the anisotropic spectrum of a c(4×4)-like surface, indicating that As species adsorbs excessively on a c(4×4)-like surface, which reduces its anisotropy. It is shown that by using different wavelengths, the dynamics of As desorption from each As-stabilized surface can be measured separately.
Structural and Electrical Properties of n-Type Poly-Si Films Prepared by Layer-by-Layer Technique
Authors: He Deyan , Shun-ichi Ishihara Shun-ichi Ishihara , Isamu Shimizu Isamu Shimizu
Published: February 2005

Polycrystalline silicon (poly-Si) films have been prepared from fluorinated precursors by introducing a layer-by-layer technique into hydrogen-radical-enhanced chemical vapour deposition (HR-CVD). The degradation in crystallinity caused by phosphine doping was found to be compensated by this novel technique and a highly ordered structure with a strong (220) orientation was observed by X-ray diffraction (XRD) and transmission electron microscopy (TEM) measurements. The hydrogen was efficiently removed from the growing film and marked evolution of the SiH
n
stretching mode was observed in IR absorption measurements. The measurements of dark conductivity showed that the carrier conduction at room temperature was dominated by a process of thermionic emission over grain boundary barriers. The trapping states as well as the recombination centres at the grain boundary of the growing film were passivated with the aid of atomic hydrogen, and the resulting films showed higher photoconductivity with the ηµτ product of around 10-4 cm2·V-1.
Trapping and Recombination of Photogenerated Carriers in As-Grown High-Temperature-Annealed and Light-Soaked a-Si:H
Authors: Saleh Zaki M. , Tarui Hisaki , Takahama Tsuyoshi , Nakamura Noboru , Nishikuni Masato , Tsuda Shinya , Shoichi Nakano Shoichi Nakano , Yukinori Kuwano Yukinori Kuwano
Published: February 2005

Our previous results of light-induced electron spin resonance (LESR) indicate that, in hydrogenated amorphous silicon (a-Si:H), light-induced defects differ from those formed during deposition or high-temperature annealing. The concept of demarcation was used to interpret these differences in terms of higher energy levels for light-induced defects. In this study, the constant photocurrent method (CPM), dark conductiviry and transient-LESR are used to supply new evidence for the differences and to conduct two tests on our hypothesis. The demarcation energies for electrons and holes are shifted by varying the temperature or bias-light intensity for transient-LESR. In striking agreement with our hypothesis, we find that the light-induced changes in the LESR line shape (an increase in the broad component relative to the narrow one upon light exposure) become indeed more dramatic as the demarcation energies move closer to the midgap.
Structural Analysis of ZnSe-GaAs Quantum Wells
Authors: Funato Mitsuru , Shizuo Fujita Shizuo Fujita , Shigeo Fujita Shigeo Fujita
Published: February 2005

The structural properties of ZnSe-GaAs quantum wells (QWs) grown by metalorganic vapor phase epitaxy are described. Detailed theoretical and experimental studies on X-ray diffraction show that when the thickness of the QW well layer is comparable to that of the barrier layer, satellite peaks which reflect the period of QW can appear even in diffraction patterns of a single quantum well. It is also shown that the intensity of X-ray interference fringes can be modulated by fluctuation of each individual layer thickness in a multiple quantum well. These analyses revealed that it was possible to fabricate ZnSe-GaAs QWs with only 10 Å well thickness, and that these structures had high crystalline quality, a high degree of lateral uniformity, well-defined interfaces, and strong periodicity. Transmission electron microscopy also gave evidence for these properties.
Atomic Step Structure on Vicinal H/Si(111) Surface Formed by Hot Water Immersion
Authors: Watanabe Satoru , Kei Horiuchi Kei Horiuchi , Takashi Ito Takashi Ito
Published: February 2005

We investigated the hydride structures at the step edges on Si(111) surfaces after removing surface oxide with HF solution followed by immersion in boiling water, using polarized infrared attenuated total-reflection spectroscopy. Vicinal (111) surfaces misoriented toward the [112̄] direction at angles of 0°, 2°, and 4° were used to elucidate the hydride structures at the steps. We assigned absorption peaks to monohydride chains at the step edges along the [1̄10] direction, vertical dihydride (whose three atoms form a surface vertical to [111]) at the kinks, and monohydride on the terraces. We determined that the silicon monohydride chain forms an atomically straight step edge along the [1̄10] direction with a small amount of vertical dihydride kinks after 5-min immersion in boiling water. Based on these assignments, we reexamined the water temperature and time dependence of these hydride structures and discussed the step formation mechanism.
Atomic Ordering in an Infinite-Layer Compound Sr0.85Nd0.15CuO2 Studied by Transmission Electron Microscopy
Authors: Li Jianqi , Yada Keiji , Zhou Xingjiang , Lin Li Lin Li , Zhongxian Zhao Zhongxian Zhao
Published: February 2005

Structural features of Sr0.85Nd0.15CuO2 superconducting compound have been studied by electron microscopy. A high resolution electron microscopy observation indicated that inhomogeneous distribution of lattice image contrasts for the tetragonal c-planes frequently appeared in the crystal, which seemed to be resulted from short range ordering of metal atoms. Upon in-situ heating observation, a superstructure with parameters 2√2a
p×2√2a
p×c has been found at the temperature of about 600 K. Following the formation of this superstructure, various kinds of antiphase domains appeared in the crystals.
Reflection-Induced Light Correlation in Spontaneous Emission in Front of a Mirror
Authors: Taniguchi Hiroshi , Yamada Hiroshi , Fujiwara Tamiya , Ito Hiroto , Tanosaki Shinji , Baba Mamoru
Published: February 2005

It is shown that fluorescence spectra from a dye-doped polymer film in front of a mirror exhibit angular and spectral localization effects caused by self-interference in the spontaneous emission. Spectral results obtained experimentally, which are dependent on film thickness, are found to be in good agreement with the calculated results predicted by a semiclassical description.
Waveguide-Type Multifrequency Acoustooptic Modulators
Authors: Hatori Masami , Miura Hideo , Sunagawa Hiroshi , Takeuchi Masao , Yamanouchi Kazuhiko
Published: February 2005

Multifrequency acoustooptic modulators (MF-AOMs) utilizing a Ti-diffused LiNbO3 waveguide are investigated for application to high-speed laser beam scanners. The Z-propagation of a light beam is free from optical damage. The surface acoustic waves (SAWs) for the MF-AOM are excited at 8 frequencies from 350 to 490 MHz every 20 MHz. Therefore, the MF-AOM generates 8 light beams using a TE-TM mode conversion. No optical damage at 633 nm wavelength is observed up to a power density of 2 kW/cm2. The AO diffraction efficiency per light beam, rise time and total efficiency of the device at 633 nm wavelength are 6%, 26 ns and 19%, respectively.
Enhancement of Photoelectric Conversion Efficiency in Copper Phthalocyanine Solar Cell by Surface Plasmon Excitation
Authors: Kume Tetsuji , Hayashi Shinji , Yamamoto Keiichi
Published: February 2005

In order to enhance the photoconversion efficiency, surface plasmon polaritons (SPP) in an organic solar cell consisting of Al, copper phthalocyanine (CuPc) and Ag thin films were excited by an attenuated total reflection (ATR) method. The dependence of the enhancement factor for the short-circuit current (I
sc) on the wavelength of the incident light (λin) was measured in detail in the visible region. It was found that the enhancement factor depends strongly on λin and takes a maximum (a factor of 8) around λin=550 nm. The good agreement between the calculated λin dependence of light absorption in the CuPc layer and the observed λin dependence of the enhancement factor suggests that the enhancement is caused by increased carrier generation in the CuPc layer due to increased light absorption upon SPP excitation.
Electrochemical Properties of Poly(isothianaphthene)
Authors: Onoda Mitsuyoshi , Morita Shigenori , Yoshino Hiroshi Nakayama
Published: February 2005

Electrochemical, optical, and magnetic properties of poly(isothianaphthene) as a function of doping potential and electronic states, are discussed in detail. The band gap of poly(isothianaphthene) has been evaluated to be 1.0 eV and the evolution of localized states is evidenced by the spectral change with electrochemical doping. The magnetic susceptibility evaluated from electron spin resonance measurement has exhibited the highest value at a doping potential of 3.5 V vs Li/Li+. These results are interpreted in terms of the polaron and/or bipolaron models. The electronic band structure of poly(isothianaphthene) has been determined. The top of the valence band of poly(isothianaphthene) is located at an energy state higher than that of polythiophene by about 0.5 eV. On the other hand, the bottom of the conduction band of poly(isothianaphthene) is located at an energy state lower than that of polythiophene by about 0.6 eV, suggesting successful electrochemical n-type doping.
Study of the Crystal Structure of Titanylphthalocyanine by Rietveld Analysis. II
Authors: Okada Okimasa , Kozo Oka Kozo Oka , Masakazu Iijima Masakazu Iijima
Published: February 2005

Rietveld analysis with the Monte Carlo method was used to estimate the crystal structure parameters of one of the polymorphs of titanylphthalocyanine (TiOPc). This polymorph is called TiOPc type C (C-TiOPc), and it is a low-photosensitive pigment used in electrophotograpy. In order to determine the relationship between crystal structure and photosensitivity, the crystal structure of C-TiOPc was estimated. The most probable crystal structure is a monoclinic unit cell, space group Cc: a=2.519 nm, b=0.385 nm, c=2.546 nm, β=90.3°, Z=4, d
calc.=1.54 g/cm3.
Estimation of the Thickness of Ultrathin Silicon Nitride Films by X-Ray Photoelectron Spectroscopy
Authors: Muto Akiko , Toshiyuki Mine Toshiyuki Mine , Masatoshi Nakazawa Masatoshi Nakazawa
Published: February 2005

The thickness and composition of ultrathin silicon nitride films which are deposited on Si substrates and on thin thermal oxide are estimated by means of X-ray photoelectron spectroscopy (XPS). With use of the peak decomposition technique and angle-resolved XPS (ARXPS), the distribution of the silicon nitride and oxide in the films is determined. Both the nitride and oxide thicknesses are evaluated. The thickness determined by XPS agrees with the thickness determined by cross-sectional transmission electron microscopy (TEM). This XPS method is valid for estimation of the thickness and composition of ultrathin silicon nitride films, and it has the advantages of accuracy over ellipsometry and convenience over TEM.
Direct Extraction of Sodium Negative Ions from Sodium Plasma
Authors: Yamaoka Hitoshi , Wada Motoi , Sasao Mamiko , Fujita Xiao-Min Tong
Published: February 2005

Diatomic negative ions of Na(Na2
-) are extracted with atomic negative ions of Na(Na-) from a low-temperature Na plasma. The extracted currents of these negative ions are experimentally measured as functions of discharge parameters and wall temperatures. The measured extraction characteristics are discussed by comparing the results with those of negative hydrogen and negative lithium ions extracted from the corresponding plasmas. The maximum current ratio of Na2
- to Na- for a wall temperature below 235°C is on the order of 0.01, much smaller than that obtained in the sputtering experiment.
Oxygen Solubilities in Si Melt:Influence of Sb Addition
Authors: Huang Xinming , Terashima Kazutaka , Sasaki Hitoshi , Eiji Tokizaki Eiji Tokizaki , Shigeyuki Kimura Shigeyuki Kimura
Published: February 2005

The oxygen solubility in liquid silicon, both undoped and Sb-doped, in equilibrium contact with SiO2 has been analyzed after quenching by the SIMS (secondary ion mass spectroscopy) technique in order to investigate the influence of antimony addition on the oxygen solubility. It has been shown that oxygen solubility in undoped silicon melt increases from 2.08×1018 to 2.29×1018 atoms/cm3 upon temperature increases from 1447 to 1542°C. The influence of antimony addition in the same temperature range was twofold. Addition of less than 1 at.% Sb caused practically no change in oxygen solubility, while addition of more than 1.3 at.% Sb appreciably increased both its level and its temperature coefficient.
Low-Field Breakdown and Negative Differential Resistance in Semi-Insulating GaAs
Authors: Hirohata Toru , Suzuki Tomoko , Kazutoshi Nakajima Kazutoshi Nakajima , Yoshihiko Mizushima Yoshihiko Mizushima
Published: February 2005

In a semi-insulating GaAs (S.I. GaAs) diode with an ohmic cathode, a negative differential resistance (NDR) appears at a field as low as 2 kV/cm. In the NDR region, luminescence with a broad spectrum is observed. The luminescence area is localized just in front of the anode. These results are explained on the basis of the avalanche injection effect in S.I. GaAs material. The electron temperature estimated from the luminescent spectrum is 3200 K. The avalanche multiplication is discussed in terms of the low-field avalanche scheme.
Carrier Reset Operation in Charge Modulation Device
Authors: Nomoto Tetsuo , Kazuya Matsumoto Kazuya Matsumoto , Tsutomu Nakamura Tsutomu Nakamura
Published: February 2005

The reset operation of the charge modulation device (CMD) transistor was examined by experiments and calculations. It was clarified that such conditions as high drain voltage, low reset gate voltage, short reset time or scaling down the size of the CMD transistor have a tendency to cause reset incompleteness. However, it was revealed experimentally that an ordinary bias condition for the CMD imager leads to complete reset in 50 ns reset pulse duration even if the size of the CMD transistor is scaled down to 5.0 µm×5.2 µm. This reset time is very short compared to the allowed time for the CMD reset operation of about 10 µs and 1 µs in national television system committee (NTSC) and high definition television (HDTV) format, respectively. It was also revealed by calculations that lowering the drain voltage synchronized with reset timing is very promising for rapid and complete reset operation. This method is applicable to all sizes of CMDs.
Optimization of ZnO Films for Amorphous Silicon Solar Cells
Authors: Tabuchi Katsuya , Wenas Wilson W. , Yamada Akira , Takahashi Makoto Konagai
Published: February 2005

ZnO films prepared by the metalorganic chemical vapor deposition (MOCVD) method were applied to amorphous silicon (a-Si) solar cells as a transparent conductive oxide (TCO). The B2H6 flow rate and the thickness of the film were optimized at 0.5 µmol/min and 2.0 µm, respectively. We also proposed a preannealing technique of the ZnO film before fabrication of a-Si solar cells, and it was shown that the open circuit voltage was increased with use of this technique. Furthermore, we fabricated a novel p-i-n a-Si solar cell structure, which had a 0.1-µm-thick ZnO layer between a-Si and the metal electrode. Theoretical calculation and experimental results proved that the reflectance of the ZnO/Ag back reflector was higher than that of the Ag electrode at wavelengths between 600 nm and 800 nm. As a result, a marked enhancement of collection efficiencies in the long-wavelength region was achieved, resulting in the increase of the short-circuit current of about 1 mA/cm2. Using both the preannealing technique of ZnO film and a ZnO/Ag/Al back reflector, a conversion efficiency of 11.9% (V
oc=0.893 V, I
sc=18.6 mA/cm2, F
F=0.715) was obtained.
Effect of Zn Diffusion on the Properties of AlGaAs Double-Hetero Light-Emitting Diodes
Authors: Yoneda Muneo , Nakamura Yukiyo , Akihito Tsushi Akihito Tsushi , Kiyoshi Ichimura Kiyoshi Ichimura
Published: February 2005

The state of Zn diffusion on the heterointerface of 660 nm AlGaAs double-hetero (DH) light-emitting diodes (LEDs) was investigated by the electron-beam-induced current (EBIC) method. The p-n junction penetrates toward the n-cladding layer as a result of Zn diffusion when the carrier concentration of the p-active layer is greater than 1×1018 cm-3. The distance between the heterointerface and p-n junction was related to the optical output and modulation bandwidth of LEDs. For producing superior LEDs, it is important that the p-n junction coincides with the hetero interface or slightly penetrates into the n-cladding layer. The dependence of the Zn effective diffusion coefficient on the carrier concentration of the p-active layer and n-cladding layer was also investigated. Finally, it was determined that the suitable growth temperature of the active layer was around 850°C.
Nondestructive Diagnostic Method Using AC Surface Photovoltage in Silicon Wafers Rinsed with Metal-Contaminated Water Solutions
Authors: Munakata Hirofumi Shimizu
Published: February 2005

The ac surface photovoltage (SPV) technique is intended for nondestructive detection of impurities in silicon (Si) wafer surfaces rinsed with various metal-contaminated water solutions. Iron (Fe)- and copper (Cu) considerably increase the ac SPVs of rinsed n-type Si wafers. This indicates that Fe and Cu induce a negative charge in the native oxide, which is similar to results previously reported for aluminum (Al) and/or Fe-contaminated Radio Corporation of America (RCA) alkaline rinses. Nickel and zinc induce a small ac SPV change, whereas Al and chromium effect no change even after exposure in air for 7 days. These results suggest that the ac SPV technique is applicable for nondestructively detecting contaminants in water-rinsed wafers.
Characterization of Damaged Layer Using AC Surface Photovoltage in Silicon Wafers
Authors: Munakata Hirofumi Shimizu
Published: February 2005

AC surface photovoltage (SPV) responds to damaged layers in n-type silicon (Si) wafers with depleted or inverted surfaces. Excited carriers recombine at broken bonds in a damaged layer, and the ac SPV is then reduced depending on whether slight or heavy damage exists at the Si surface. The ac SPV is related to the thermally modulated reflectance signal and, thus, is qualitatively applicable to nondestructive evaluation of the damaged layer.
Low-Frequency Fluctuation of the Transport Factor in Junction Transistors*
Authors: Takagi Keiji , Mizunami Toru , Shiyuan Yang Shiyuan Yang , Masanori Wada Masanori Wada
Published: February 2005

Noise analysis is carried out in a junction transistor. It is shown that the transport factor of the transistor fluctuates in proportion to the 3/2 power of the current at low frequency. This is derived from the base width modulation caused by mobility fluctuation in the collector space-charge region.
Modulation of Kinetic Inductance of High Tc Superconducting Thin Films with Bias Current
Authors: Enpuku Keiji , Hoashi Masakazu , Hideki Doi Hideki Doi , Takanobu Kisu Takanobu Kisu
Published: February 2005

Kinetic inductance of high T
c superconducting thin films is studied using numerical simulation of the Ginzburg-Landau (GL) theory. It is shown that a current distribution in the film changes nonlinearly with a bias current supplied to the film, which results from the nonlinear properties of the GL equation. Using the current distribution, the kinetic inductance of the film is obtained as a function of the bias current. It is shown that the kinetic inductance is constant for low bias currents, and increases nonlinearly with the bias current when the bias current becomes large. The effect of the film geometry on the modulation of the kinetic inductance is quantitatively studied. Analytical solutions for the current distrubiton and the kinetic inductance are also obtained, which agree well with the simulation results. The modulation of the kinetic inductance with the bias current predicted from the theory is partly confirmed from experiments using YBaCuO films.
Washer Resonances of DC Superconducting Quantum Interference Device Coupled to Multiturn Input Coil
Authors: Koch Keiji Enpuku
Published: February 2005

Properties of washer resonances in dc superconducting quantum interference devices (SQUIDs) coupled to a multiturn input coil have been studied using an expanded model of the coupled SQUID. The condition of resistances required to suppress the washer resonance is clarified. In the coupled SQUID, junction shunt resistances should be determined by taking into account this condition in addition to the conventional condition βc<1, where βc is the McCumber parameter. In the case of small junction capacitances, it is shown that the washer resonance limits the value of junction shunt resistances, and prevents the use of large resistances given by βc<1. In order to solve this problem, a new washer geometry of the SQUID is proposed. From the experiment using the expanded model of the new washer, it is shown that the new washer can control the washer resonances, and enables the use of large resistance in the coupled SQUID. Therefore, the new washer will be useful for the improvement of the performance of the coupled SQUID.
Reflection and Diffraction of Laser Plasma Induced by Bombardment of TEA CO2Laser at Low Pressures
Authors: Tani Masanobu , Kurniawan Hendrik , Ueda Hiroshi , Mizukami Kazuo , Kawai Kazuyuki , Kagawa Kiichiro
Published: February 2005

A transversely excited atmospheric-pressure (TEA) CO2laser beam has been focused on a Zn plate at reduced ambient gas pressure. It is demonstrated that reflection and diffraction phenomena take place in the laser plasma when the free expansion of the laser plasma is limited by an obstructing material placed in front of the target. These findings strongly support the shock wave model for explaining the mechanism in forming a laser plasma.
Luminescence from the Aggregated Cu+ Centers in SrS:Cu+
Authors: Yamashita Nobuhiko , Kazuo Ebisumori Kazuo Ebisumori , Kaizo Nakamura Kaizo Nakamura
Published: February 2005

The photoluminescence (PL) and excitation spectra, PL decay curves and time-resolved PL spectra are measured at 80 K for the SrS:Cu+ powder phosphors activated with a large amount of Cu2S. The shape and peak position of the PL spectra depend on both the activator concentration and the excitation wavelength. The PL spectra consist of four kinds of Cu+ bands, α, β, γ and δ. The α band peaking at 513 nm at 80 K is attributed to the isolated Cu+ center, the β band peaking at 543 nm at 80 K to the paired Cu+ center, and the γ (558 nm at 80 K) and δ (about 600 nm at 80 K) bands to the highly aggregated Cu+ centers.
Ion-Beam-Induced White Luminescence of CaF2 Implanted with Both Eu and Tb Ions
Authors: Aono Keiko , Kumagai Makoto , Kashiwagi Kunihiro , Murayama Youichi , Iwaki Masaya
Published: February 2005

A study on luminescence induced by Ar-ion bombardment of ion-implanted CaF2 has been conducted. Ion implantations of Eu and Tb ions in CaF2 single crystals ware carried out at fluences of 1×1014-1×1015 ions/cm2 at 100 keV at room temperature. The luminescence spectra from the Eu-implanted specimen mainly consist of two peaks: one is at ∼430 nm due to Eu2+ and the other is at ∼600 nm due to Eu3+. The main peak of ∼545 nm owing to Tb3+ appears in Tb-implanted CaF2. The luminescence spectra from CaF2 implanted with both Eu and Tb ions mainly show three peaks at ∼430, ∼545 and ∼600 nm, which are close to the wavelengths of the three primary colors. Ion implantations of both Eu and Tb ions result in white luminescence which is visible to the naked eye, with control of the fluences of Eu and Tb ions.
Mechanism of Photoinduced Charge Transfer of Cu-Doped ZnO Film in Strong Electric Field
Authors: Kobayashi Kenkichiro , Udaka Hiroaki , Shigenori Matsushima Shigenori Matsushima , Gengi Okada Gengi Okada
Published: February 2005

A three-layer film consisting of In-doped ZnO, Cu(Li)-doped ZnO and Au has been prepared by the sputtering method. Photocurrent measurements have been performed by applying a reverse bias to the In-doped ZnO and Au electrodes. Continuous photocurrents are observed at wavelengths shorter than 780 nm, and a distinct peak is seen near 400 nm. Illumination with light of 365 nm during the photocurrent measurements results in an increase in photocurrent near 600 nm, but a decrease in photocurrent near 700 and 400 nm. The mechanism of the photoinduced charge transfer in the three-layer film is discussed on the basis of spectral and time dependence of photocurrent.
Organic Electroluminescence Devices Using Poly(arylene vinylene) Conducting Polymers
Authors: Onoda Mitsuyoshi , Uchida Masao , Ohmori Yutaka , Yoshino Katsumi
Published: February 2005

An orange electroluminescent (EL) diode utilizing poly(1,4-naphthalene vinylene) (PNV) has been demonstrated for the first time and the EL properties of PNV are discussed in comparison with those of EL diode utilizing poly(p-phenylene vinylene) (PPV). The EL emission of these two devices can be interpreted in terms of radiative recombination of the singlet polaron exciton formed by the injection of electrons and holes. Although the EL intensity of the PNV light-emitting diode is weak compared to that of the PPV diode, orange EL emission was clearly observed under normal room light even at low driving voltage. These results are discussed in terms of the difference in effective conjugation length and the interchain transfer of polaron excitons generated by the injection of electrons and holes.
Interdiffusion in Pd/Ti Bilayer Films Studied by Auger Electron Depth Profiling
Authors: Tadayyon Seyed Mohammad , Osamu Yoshinari Osamu Yoshinari , Kazuhide Tanaka Kazuhide Tanaka
Published: February 2005

Interdiffusion processes in Pd/Ti bilayer films subjected to diffusion annealing at temperatures between 523 K and 623 K are studied. Changes of the concentration profile with annealing as revealed by Auger electron depth profiling are analyzed based on an error function analysis and the Boltzmann-Matano method to derive the intrinsic diffusion coefficients of Pd and Ti in the films. The diffusion coefficients obtained by the two methods agree well on the Ti-rich side. The temperature dependence of the diffusion coefficients is expressible by an Arrhenius-type equation, from which characteristic diffusion parameters are determined. A structural change associated with the interdiffusion is studied by grazing incidence X-ray diffraction.
Molecular Orientation in Polyimide Films Having Rodlike Molecular Skeleton Formed on Silicon Substrate
Authors: Hideshi Nomura Hideshi Nomura , Masaya Asano Masaya Asano
Published: February 2005

Polarized infrared spectroscopy was used to characterize molecular orientation in polyimide films deposited on silicon wafers. The films were constructed from a single polyimide having a rodlike molecular skeleton. The degree of in-plane orientation at the interface with the wafer in the film varied with film thickness. On the other hand, that at the surface was almost constant. As a result of the difference in the thermal coefficient of expansion related to the degree of in-plane orientation between the surface and interface regions, thick films curled after they were stripped off the wafers. This phenomenon was presumed to be caused by the variation in the amount of the residual solvent in the polyimide precursor film with film thickness before the thermal cycle for imidization.
Application of a Ge Detector to Search for Fast Neutrons from DD Fusion in Deuterized Pd
Authors: Choi Eunjoo , Hiroyasu Ejiri Hiroyasu Ejiri , Hideaki Ohsumi Hideaki Ohsumi
Published: February 2005

A low-background high-resolution Ge detector surrounded by neutron scatterers was applied to investigate fast neutrons from the electrochemically loaded Pd-D system. The neutron flux was obtained by measuring the yields of the γ-rays following inelastic scattering of the fast neutrons from nuclei in the scatterers. The detector was shown to be very sensitive in the search for rare neutron events such as d-d fusion at room temperature. The observed spectrum shows no statistically significant excess of the γ-rays above the background. The upper limit on the fusion rate was obtained as λ
f
<1.6·10-24(ddn)fusions/(dd)pair/s.
High-Power Microwave Window for Reactive Plasma Production
Authors: Kokai Yuichi Sakamoto
Published: February 2005

It is experimentally shown that a high-power coaxial microwave window, the surface of which is covered with a Cr2O3 thin film, is very stable against reactive plasma irradiation.
Energy Distributions of Atoms Sputtered from Cu-Pt Alloy Measured by Nonresonant Multiphoton Ionization Sputtered Neutrals Mass Spectrometry
Authors: Kunitomo Shinta , Ono Masahiro , Chun Fei Li Chun Fei Li , Ryuichi Shimizu Ryuichi Shimizu
Published: February 2005

Energy distributions of sputtered Cu and Pt atoms from monoatomic and Cu-Pt (55 at.%) alloy samples under Ar+ ion bombardment were measured using an sputtered neutrals mass spectrometry (SNMS) instrument in nonresonant multiphoton ionization. The distributions for the pure Cu and Pt samples agreed very well with the theoretical distribution derived by Thompson [Philos. Mag. 18 (1968) 377], while considerable deviation was found in the distributions of Pt atoms from the Cu-Pt alloy, particularly at lower energy. The results have also revealed that the peak position, which reflects the surface binding energy according to Thompson's theoretical expression, of the energy distribution of Pt atoms from the alloy is ∼0.6 eV lower than that of the Pt atom energy distribution from the pure Pt sample.
Constant Angle of Diffraction-Spherical Grating Monochromator for Undulator Radiation
Authors: Eiji Ishiguro Eiji Ishiguro
Published: February 2005

A new type of spherical grating monochromator for undulator radiation is proposed. Two reflecting elements of a plane mirror and a spherical grating are used between the entrance slit and the exit slit. It has a simple scanning mechanism: the plane mirror rotates around an axis on its surface so as to change the angle of incidence, while the grating is fixed with a constant angle of diffraction. Resolution of the monochromator is estimated for a soft X-ray undulator beamline of the SPring-8 by a ray tracing calculation. The results show that the monochromator can achieve high resolution, high energy and high photon flux in the soft X-ray region.
Characteristics of Boron Epoxy Resin as a Gasket for Pressure Generation in the 20 GPa Region
Authors: Taniguchi Takashi , Osamu Shimomura Osamu Shimomura , Shinobu Yamaoka Shinobu Yamaoka
Published: February 2005

Boron and epoxy-resin gaskets were characterized in terms of pressure generation in the 20 GPa region using a Bridgman-type opposed anvil apparatus made of sintered diamond (SD). As compared to pyrophyllite, boron and epoxy resin exhibited markedly large internal friction. It was recognized that the properties of boron and epoxy resin as a gasket can be modified by changing their composition or by adding layered materials such as mica. Stress analysis of the anvils was performed by a finite-element method using the evaluated value of the internal friction of the gasket. The breakage behavior of the SD anvils were then described on the basis of the evaluated properties of the gaskets used.
Efiect of Electron Energy Distribution on Bremsstrahlung Spectrum
Authors: Nakamori Nobuyuki , Yamano Kaname , Masayoshi Yamada Masayoshi Yamada , Hitoshi Kanamori Hitoshi Kanamori
Published: February 2005

We calculated bremsstrahlung spectra using the Monte Carlo method taking into consideration electron energy distribution and multiple scattering in a target, which were neglected in the semiempirical models of Birch and Marshall (BM) [Phys. Med. Biol. 24 (1979) 505] and Tucker et al. (TBC) [Med. Phys. 18 (1991) 211]. We compared our results with the spectra measured by Fewell et al. and those calculated by BM- and TBC-models, and discussed the effects of the electron energy distribution on the bremsstrahlung spectra. Our results agreed with the spectra measured by Fewell et al., for a variety of radiographic conditions used in medical diagnosis. Spectra calculated using the BM model agreed roughly with measured data, but tended to deviate as target angle decreased. Spectra calculated using the TBC model agreed with measured data for an X-ray tube with the target angle of 10°, but disagreed for other X-ray tubes. As a result, we showed that electron energy distribution had significant effects on the calculation of bremsstrahlung spectra for medical use.