bluuebunny/crossref_metadata_2025 huggingface dataset:
Bond-Angle Distribution of Sn Atom and 119Sn Mössbauer Spectroscopy in Hydrogenated Amorphous Silicon Doped by Sn
Authors: Myoren Hiroaki , Osaka Yukio
Published: February 2005

The 119Sn Mössbauer spectral shape resulting from the bond-angle distribution of a Sn atom in a Si matrix is theoretically investigated. The application of this theory to the experiments on 119Sn Mössbauer spectroscopy of sputtered a-Si:H films shows that the generation of fewer overconstrained regions due to SiH2 bonding configuration appreciably decreases the standard deviation σ of the bond angle deviation for the Sn atom. For sputtered a-Si:H films, the minimum value of σ is estimated to be 2.6°, which is mach smaller than the σ (≃7.7°) for the unhydrogenated films.
Optical Heterodyned Coherent Brillouin Spectroscopy (OHD-BIKES) Using Continuous-Wave (cw) Dye Lasers
Authors: Haga Taketomo , Higuchi Masahiko , Abe Kohji , Shigenari Takeshi
Published: February 2005

Steady-state coherent Brillouin spectroscopy using continuous wave(cw) lasers was demonstrated. Use of cw dye lasers and optically heterodyned detection, Brillouin-induced Kerr effect spectroscopy (cw-OHD-BIKES) was shown to have higher resolution power than conventional linear spectroscopy and pulsed-laser BIKES. The linewidth of the spectrum (FWHM 93 MHz in CS2) was limited by the stability of the dye lasers. Besides the Brillouin signals, coherent Rayleigh (quasi-elastic) spectrum was also observed in C6H6 and C6H5Cl. Compared to CARS-type spectroscopy, the cw-BIKES does not require the phase-matching condition and the spectrum can be observed without being masked by elastic Rayleigh scattering, so it might be useful for the study of low-energy excitations in anisotropic media, such as crystals.
Optical Characterization of Deep Levels in Single Crystals of CuGaS2 Grown by Chemical Vapor Transport
Authors: Tanaka Katsu , Ishii Koki , Matsuda Seisuke , Hasegawa Yoshitsugu , Sato Katsuaki
Published: February 2005

Optical absorption spectra were measured in undoped and Fe- or Ni-doped single crystals of CuGaS2 grown by the chemical vapor transport technique. Chemical analysis of Fe concentration by absorption spectrophotometry and optical characterization by absorption and photoluminescence(PL) spectroscopy in these materials revealed that the main trace impurities which darken undoped crystals are Ni and Fe. The excitation spectrum of the infrared PL due to Fe3+ was also measured. From this, the 1.8 eV peak of the strong absorption band introduced by trace Fe impurities was interpreted in terms of the transition from the valence band to the dangling bond state hybridized with 3d orbitals.
Diffusion Coefficient of Interstitial Iron in Silicon
Authors: Isobe Takashi , Nakashima Hiroshi , Hashimoto Kimio
Published: February 2005

The in-depth profiles of iron in silicon diffused with iron at 800, 900, 1000 and 1070°C were investigated by DLTS measurements. The diffusion coefficient of interstitial iron in silicon was represented by the expression D
Fe=9.5×10-4 exp
(-0.65/k
T) cm2s-1 in the temperature range of 800–1070°C.
Approach from a-Ge Films for Development of High-Quality a-SiGe Films
Authors: Haku Hisao , Sayama Katsunobu , Matsuoka Tsugufumi , Tsuda Shinya , Nakano Shoichi , Ohnishi Michitoshi , Kuwano Yukinori
Published: February 2005

a-Ge:H films fabricated by means of a separated ultrahigh-vacuum reaction chamber, called the super chamber, were systematically studied. In the conventional glow-discharge method, there is a very narrow substrate-temperature region for fabricating high-density a-Ge:H films; that is, a minimum deposition rate and a maximum refractive index were obtained at about 250°C. From the point of view of optoelectrical properties, it was clear that not only rigidity of the film network but also total hydrogen content are important. In order to satisfy the two above-mentioned factors simultaneously, a low substrate-temperature high hydrogen-dilution method was effective, and film properties of a-Ge:H were largely improved; δd∼4.0×10-5 Ω-1 cm-1, δph∼1.5×10-4 Ω-1 cm-1, B value ∼803 (eV·cm)-1/2, and the ESR spin density ∼1.5×1017 cm-3.
Electrical Properties of Undoped and Ion-Implanted Cubic SiC Grown on Si(100) by Chemical Vapor Deposition
Authors: Shibahara Kentaro , Takeuchi Tatsuya , Nishino Shigehiro , Matsunami Hiroyuki
Published: February 2005

Electrical properties of undoped layers of cubic SiC grown on Si(100) well-oriented and off-oriented substrates were evaluated by Hall measurements. The layers grown on off-oriented substrates showed electrical anisotropy. The origin of the electrical anisotropy was investigated by EBIC (electron beam induced current) and TEM (transmission electron microscope) observation. P+ or N2
+ implantation was also investigated. Electrical activation of implanted impurities was improved by raising annealing temperatures. N2
+-implanted layers elicited higher electrical activation rates than P+-implanted layers. Planar-type p-n junction diodes were fabricated using ion implantation, and their characteristics were evaluated.
Study of Quantitative Elemental Analysis of Monochromatic X-Ray CT Using Synchrotron Radiation
Authors: Hirano Tatsumi , Eguchi Shuuji , Usami Katsuhisa
Published: February 2005

X-ray computed tomography (CT), based on monochromatized synchrotron radiation as an X-ray source, provides spatial distributions of a specific element using the difference between two CT images taken just above and below the absorption edge energy of the element. We have studied a quantitative analytical function for an element by measuring X-ray CT images of a model sample using the subtraction method. The differential CT value, which is seen as the shading intensity in the differential CT image, is proportional to the concentration of the specific element. Both spatial distributions and concentrations of the specific element can be nondestructively observed. Barium concentrations in an optical waveguide were obtained, and the relation between the concentration and the refractive index was examined.
Photo-Induced Memory Effect in Polyaniline/Polyvinylcarbazole Organic System
Authors: Nakazawa Yusuke , Hoshino Katsuyoshi , Hanna Jun-ichi , Kokado Hiroshi
Published: February 2005

An illumination memory previously observed in a polyaniline/polyvinylcarbazole double-layered photoconductor was studied in detail. Various parameters were examined, such as the corona condition, the light intensity, the wavelength, and the exposure energy. Ionized polyaniline molecules with a dopant anion were considered to be responsible for the memory effect. They were dissolved and diffused into the polyvinylcarbazole layer, and upon light absorption they induced photoconduction accompanied by the memory effect. The memory effect was found to be linear against the amount of surface charges dissipated by photons. By optimizing the parameters, a large memory contrast potential more than 500 V, which is suffciently high for most practical applications, was obtained.
Surface-Enhanced Raman Scattering from Surface Layers of Gas-Evaporated Silver Small Particles
Authors: Hayashi Shinji , Koh Risho , Yamamoto Keiichi , Ishida Hideyuki
Published: February 2005

Silver small particles prepared by the gas-evaporation technique with four different heater materials, i.e. Mo, W, C and Ta, have been studied by Raman and X-ray photoemission spectroscopy. Raman spectra of the particles prepared with the Mo and W heaters exhibit a strong and asymmetric band at about 900 cm-1 and a few weak bands below 350 cm-1. These Raman bands are absent in the spectra of particles prepared by C and Ta heaters. Results of XPS suggest the formation of oxides of Mo and W at the particle surfaces. The observed Raman bands can thus be attributed to surface-enhanced bands originating from the oxide coatings. We identify the coatings with amorphous Ag2MoO4 and Ag2WO4.
Solid Phase Grain Growth and Electronic Properties of Si+-Implanted Glow-Discherged a-Si:H Thin Films
Authors: Noguchi Takashi , Ohshima Takefumi , Hayashi Hisao
Published: February 2005

Si+ was implanted into hydrogenated thin amorphous silicon films. After Si+ implantation, the films were changed to the disordered state; correspondingly, the absorbance peaks in the infrared region relating to the Si-Hn stretching mode were all concentrated near 2000 cm-1. Subsequently, as a result of furnace annealing at 600°C, dendritic large and flat grains with improved electronic properties were observed. These are expected to be applicable for large area electronics on low-temperature glass.
Construction of a Small-Angle X-Ray Scattering Diffractometer for the Study of Fluctuations in Solutions
Authors: Hayashi Hisashi , Nishikawa Keiko , Iijima Takao
Published: February 2005

A small-angle X-ray scattering (SAXS) diffractometer for the measurement of SAXS from solutions composed of molecules with low molecular weight has been constructed. In this diffractometer, a bent LiF monochromator, whose radius of curvature is 1828 mm, a sample holder with 25 µm-thick aluminium windows, and a PSPC system are used. A small-angle resolution of better than 6 mrad is achieved. To estimate the efficiency of the diffractometer, the measurement of the absolute intensity of some pure liquids was accomplished. Consequently, it has been ascertained that the diffractometer is a competent apparatus for the measurements within the accuracy of 3% of the absolute intensity.
Dispersive-Type Optical Bistability in a Self-Electrooptic-Effect Etalon
Authors: Tomita Akihisa , Suzuki Akira , Komatsu Keiro
Published: February 2005

A dispersive-type self-electrooptic-effect etalon, which consists of a Fabry-Perot etalon multiple quantum well modulator and an electrical feedback circuit, is proposed. Calculations show that the ON-OFF contrast is improved up to 9:1 due to the sharp etalon resonance. The effect of the mirror reflectivity and the absorption coefficient is also studied.
Dislocations and Thermal Conductivity of Gd3+y(Ga0.8Al0.2)5-yO12 Garnets
Authors: Kimura Hideo , Numazawa Takenori , Sato Mitsunori , Maeda Hiroshi
Published: February 2005

Single Crystals of Gd3(Ga0.8Al0.2)5O12 garnets with excess gadolinium ions have been grown using the Czochralski method. The reduction of the density of grown-in dislocations was attempted by means of the addition of excess gadolinium ions. This technique is effective to reduce the density of dislocations. The reduction of the dislocation density was confirmed by the thermal conductivity measurement.
Application of Vacuum Ultraviolet Laser Light to Photoelectron Spectroscopy
Authors: Munakata Toshiaki , Kasuya Takahiro
Published: February 2005

A photoelectron spectrometer based on laser light of vacuum ultraviolet (VUV) wavelength was developed for the study of electronic states of a solid surface. The VUV laser light, with 10.48 eV photon energy, generated by frequency tripling of the third harmonics of a pulsed YAG laser was used to induce photoelectron emission exhibiting a unique advantage over the conventional light source. The outstanding capabilities of this type of photoelectron spectrometer were demonstrated in (a) spatial resolution of at least 0.15 mm, (b) state selective photoemission by use of the polarized VUV laser, and (c) sensitivity to a normally unoccupied state by means of two-step excitation.
Theoretical Study on the High-Energy Electron Energy Loss Spectroscopy Compared with X-Ray Absorption Spectroscopy. II. Effects of Single Elastic Scattering
Authors: Fujikawa Takashi , Takatoh Shuji , Usami Seiji
Published: February 2005

In this paper we propose a new theoretical approach to high-energy electron energy loss spectroscopy (EELS) based on the short-range order theory which includes elastic scattering before and after deep core excitation. Within the single elastic scattering approximation for the fast electron, numerical calculations have been performed on the K-edge EELS from diamond (111) and Al (111), (001) surfaces for three different modes: the grazing incidence and low takeoff angle detection mode, the backward scattering reflection mode and the transmission mode. The calculated results show that the dipole excitation mainly contributes at small-angle scattering as expected, and the elastic scatterings recover the dipole excitation contribution substantially at large-angle scattering; however, the nondipole processes are dominant even under the large-angle scattering condition.
The Influence of the Si-H2 Bond on the Light-Induced Effect in a-Si Films and a-Si Solar Cells
Authors: Nakamura Noboru , Takahama Tsuyoshi , Isomura Masao , Nishikuni Masato , Yoshida Kazuhiro , Tsuda Shinya , Nakano Shoichi , Ohnishi Michitoshi , Kuwano Yukinori
Published: February 2005

The influence of the Si-H2 bond on light-induced degradation and the thermal recovery of a-Si films and a-Si solar cells were studied. The influence of the Si-H2 bond on light-induced degradation depends on the impurity content in a-Si films, and light-induced degradation can be reduced by decreasing the Si-H2 bond density in a-Si films with impurity content of 1018 cm-3. The activation energy of the thermal recovery process was about 1.0 eV, and it did not depend on the Si-H2 bond density. However, an irreversible phenomenon was observed in film properties and solar cell characteristics with high Si-H2 bond density. It is thought that the structural flexibility of the Si-H2 bond is related to this irreversible phenomenon.
XeCl Excimer Laser Annealing Used to Fabricate Poly-Si TFT's
Authors: Sameshima Toshiyuki , Hara Masaki , Usui Setsuo
Published: February 2005

Polycrystalline silicon thin-film transistors (poly-Si TFT's) with a high carrier mobility were fabricated at low processing temperatures of 150 and 250°C. A hydrogenated amorphous silicon (a-Si:H) film was successfully crystallized at room temperature by multistep irradiation of XeCl-308 nm excimer laser pulses without explosive evaporation of hydrogen. The poly-Si TFT's fabricated by the 250°C process had a carrier mobility of 54 cm2/V·s and a low potential barrier height at a grain boundary of 0.01 eV.
Multiple Photochemical Hole Burning of Tetraphenylporphine Derivatives
Authors: Tamura Shin-ichiro , Kishii Noriyuki , Asai Nobutoshi , Seto Jun'etsu
Published: February 2005

We have studied multiple photochemical hole burning of tetraphenylporphine derivatives in the frequency domain. More than 100 holes were produced in an inhomogeneously broadened absorption band at liquid helium temperature. High resolution monitoring of photochemical holes by scanning the wavelength of a single-mode dye laser proves that the potential area density of recording reaches up to 1000 holes/laser spot. We also carried out multiple photochemical hole burning in a focused laser spot, and produced more than 10 holes. These experiments indicate that tetraphenylporphine derivatives are suitable materials in practical applications of photochemical hole burning.
Optical Properties near the Fundamental Edge of an AgGaS2 Single Crystal
Authors: Kobayashi Satoshi , Ohno Toshiaki , Tsuboi Nozomu , Kaneko Futao , Maruyama Takeo
Published: February 2005

The exciton energies of the A and B
C excitons, which correspond, respectively, to the transitions from the uppermost valence band and the lower valence bands to the conduction band, in an AgGaS2 single crystal have been evaluated by analyzing polarized reflectivity spectra in the temperature range 77–294 K. The A exciton energy is estimated to be 2.701 eV, in agreement with the findings of other researchers, at 77 K. The energy difference between the A and B
C excitons is 270 meV and almost independent of temperature. Cathodoluminescence spectra have two peaks over the measured temperature range. The one at the higher photon energy is interpreted as the decay of the A exciton in consideration of the electron-beam voltage dependence on the peak position.
Anharmonic Interatomic Potentials of Metals and Metal Bromides Determined by EXAFS
Authors: Yokoyama Toshihiko , Satsukawa Tomiaki , Ohta Toshiaki
Published: February 2005

A new method is proposed for the determination of anharmonic interatomic potentials of fcc metals (Cu, Pd, Ag and Au) and metal halides (AgBr and CuBr). Structural parameters given by the temperature-dependent EXAFS (extended X-ray absorption fine structure) analysis allow us to estimate an interatomic potential if a certain analytical potential function such as Morse or Mardelung potential is assumed. The derived parameters as dissociation energies, thermal expansion coefficients and Mardelung constants (only for Mardelung potentials) are compared with the data in the literature.
Transmission Electron Microscopy Study on Microstructure of Tungsten/Carbon Multilayer Films
Authors: Oshino Tetsuya , Shindo Daisuke , Hirabayashi Makoto , Aoyagi Eiji , Nikaido Hideo
Published: February 2005

Microstructure changes of tungsten/carbon (W/C) multilayer films with heat treatments were investigated by high-resolution transmission electron microscopy (HRTEM) and X-ray diffraction. When the W/C amorphous multilayer films were annealed in vacuum at 800 or 900°C, the X-ray reflectivity became 30% higher than that of as-prepared ones in association with a slight increase of the periodic spacing of the multilayers. HRTEM images of the annealed specimens revealed the existence of randomly distributed microcrystallites of W
2
C in the W layers. The increase of X-ray reflectivity was interpreted well with a simple structural model assuming the decrease of the C-atom-number density in the C layers.
Interface-Roughness Scattering in GaAs/AlxGa1-xAs Superlattices
Authors: Wataya Mitsuo , Sawaki Nobuhiko , Goto Hideo , Akasaki Isamu , Kano Hiroyuki , Hashimoto Masafumi
Published: February 2005

The electron mobility limited by the interface-roughness scattering in a GaAs/Al
x
Ga1-x
As superlattice is studied as a function of the period (the well width L
W and the barrier thickness L
B) and the temperature. If the superlattice period is short and the electronic states resemble that of the 3D state, the mobility is limited by the interface-roughness scattering at low temperatures and insensitive to the temperature, in good agreement with experimental results. Using a finite potential-barrier height, it is shown that the variation of the mobility as a function of the quantum well width L
W is not so steep as that of the single-quantum-well structure assuming an infinite potential-barrier height.
X-Ray Diffraction from GaAs/AlAs/GaAs Grown on GaAs(001) by MBE
Authors: Kashihara Yasuharu , Ikeda Kenjirou , Harada Jimpei
Published: February 2005

The structure of a GaAs/AlAs/GaAs multilayer grown on a GaAs(001) substrate by MBE was investigated by X-ray diffraction. The lattice spacing in such a single bunch of AlAs layers was found to expand along the epitaxial-growth direction due to a Poisson expansion. The lattice mismatch between GaAs and AlAs perpendicular to the growth direction is compensated.
Triangular Shaped Beam Technique in EB Exposure System EX-7 for ULSI Pattern Formation
Authors: Hattori Kiyoshi , Ikenaga Osamu , Tamamushi Syuichi , Wada Hirotsugu , Nishimura Eiji , Ikeda Naotaka , Katoh Yoshihide , Kusakabe Hideo , Yoshikawa Ryoichi , Takigawa Tadahiro
Published: February 2005

The generation of a triangular and rectangular shaped beam is very useful in increasing throughput for writing ULSI patterns which often include many oblique lines. To make use of these shaped beams in ULSI pattern formation, a new rectangular and triangular shaped beam calibration method has been developed on the EB exposure system EX-7. The shaped beam calibration method is established by analyzing the beam current of shaped beams and the backscattered electron signal from a fine gold particle on the target. Resultant accuracies were 0.013 µm for a beam size of 1.6 µm and 0.025 %micro;m for the relative beam position on the target. Using this method, 0.2 µm ULSI patterns including oblique lines have been accurately formed.
Performance of a Focused-Ion-Beam Implanter with Tilt-Writing Function
Authors: Sawaragi Hiroshi , Manabe Hironobu , Kasahara Haruo , Aihara Ryuso , Nakamura Kazuo , Nihei Fumiyuki , Ochiai Yukinori , Matsui Shinji , Nozaki Tadatoshi
Published: February 2005

An FIB implanter has been developed from a previous FIB lithography system design. Pattern writing with high registration accuracy is performed by a combination of beam-vector scanning and a step-and-repeat stage movement. In order to minimize the axial and planar channeling effects, the ion optical system can be tilted manually up to 7° without venting the workpiece chamber. To correct distortion, a high-speed distortion-correction unit was added. In addition, a sublens and a dynamic-focusing unit were also included for real-time focusing correction. Writing, stitching and overlay accuracies were evaluated by measuring vernier patterns. The stitching error was 0.178 µm (2σ) in the X axis and 0.161 µm (2σ) in the Y axis direction, while the overlay error was 0.170 µm (2σ) in the X-axis and 0.183 µm (2σ) in the Y-axis direction. Ion depth distribution from the implantation of focused Si ions has been measured. The coincidence in SIMS profiles was confirmed for FIBI and conventional ion implantation, when the ion-beam channeling is controlled.
CPAA Study on Carbon, Boron and Oxygen in LEC-GaAs
Authors: Itoh Yoshiko , Kadota Yoshinori , Nozaki Tadashi , Fukushima Hiroto , Takeda Kenji
Published: February 2005

Carbon, boron and oxygen in liquid-encapsulated Czochralski(LEC) semi-insulating GaAs crystals grown in three different ambiences (Ar, Ar+1% O2, and Ar+1% CO) were analyzed by charged particle activation analysis (CPAA) using the 12C(d, n)13N, natB(d, xn)11C, and 16O(3He, p)18F reactions.
An addition of 1% O2 or CO gas to a conventional Ar ambience during crystal growth was found to increase C contamination by a factor of up to 35 (1.8× 1016 cm-3), while B and O concentrations remained unchanged for the most part.
Cold and Low-Energy Ion Etching (COLLIE)
Authors: Fujiwara Nobuo , Shibano Teruo , Nishioka Kyusaku , Kato Tadao
Published: February 2005

It is shown that a new cold and low-energy ion etching system (COLLIE) is effective as a dry etching technique for fabrication of VLSI devices. In the COLLIE system, plasma instabilities are suppressed by an MHD stable magnetic field consisting of a solenoid coil and multicusp magnets. The ion temperature, which is strongly related to plasma instabilities, is lowered below 2 eV in this system. Etched profiles show a strong anisotropic feature without applying any external electrical bias. As small angular distribution of incident ions to a sample is realized, the microloading effect is greatly improved.
Effects of the Deposition Sequence on Amorphous Silicon Thin-Film Transistors
Authors: Hiranaka Kouichi , Yoshimura Tetsuzo , Yamaguchi Tadahisa
Published: February 2005

We examined the effects of the deposition sequence on the threshold voltage and field-effect mobility in amorphous silicon thin-film transistors. When the nitrides are deposited after the a-Si:H(normal), the threshold voltages become more positive, and the field-effect mobilities are lower than with the inverted sequence. Photoluminescence measurements reveal that the tail states in the a-Si:H near the a-Si:H/a-SiN
x
interface for the normal sequence are wider than for the inverted sequence.
Crystallization of TeOx-Pd Films for Optical Recording Materials
Authors: Kimura Kunio , Ohno Eiji
Published: February 2005

The crystallization of TeO
x
-Pd films has been studied by differential thermal analysis, X-ray diffraction and transmission electron microscopy. The optical transmittance changes accompanying crystallization are not monotonous, but stepwise with increasing annealing temperature. The changes in films annealed at temperatures lower than 270°C are based on the phase transformation of PdTe from the amorphous to the crystalline state without large grains. For the films annealed at temperatures up to 270°C, large crystal grains of PdTe are observed. On the other hand, no large crystal grains in the recorded spots by laser irradiation are observed though the laser power is increased up to the level sufficient to melt the films. The degree of crystallization in laser-irradiated films is the same as that in films annealed at 270°C.
Investigation of the Uniaxial Stress Effect on the Exciton System in Pure Silicon and Germanium
Authors: Uddin Ashraf , Nakata Hiroyasu , Otsuka Eizo
Published: February 2005

The impact-ionization of free excitons is studied under uniaxial stress in pure silicon and germanium. The photoluminescence of hot free excitons related with light holes is observed in silicon under low excitation. The breakdown fields for the impact ionization of free excitons are 100 V/cm in silicon and 39 V/cm in germanium at zero stress. They decrease steadily with uniaxial stress. This decrease in breakdown field is due to the decrease in binding energy of the free exciton with stress. The photocurrent sharply increases when the electric field exceeds the breakdown field for free excitons. The sample resistance steadily decreases with increasing stress in the presence of illumination due to the increase of carrier density.
Electronic Structures Localized at the Boron Atom in Amorphous Fe-B and Fe-B-P Alloys
Authors: Yasuda Hidehiro , Nakayama Hiroshi , Fujita Hiroshi
Published: February 2005

The electronic structures localized at the B in amorphous Fe-B and Fe-B-P alloys and their crystallized alloys were studied by Auger valence electron spectroscopy and the states of solute B are discussed based on the change in the degree of covalent bonding and the charge transfer between the Fe and B atoms. In amorphous phases, the charge transfers from Fe to B above 15at%B where B atoms occupy the substitutionallike situations, and from B to Fe below 15at%B where B atoms occupy the interstitiallike situations. Magnetic properties depend on such states of solute B. In crystalline phases, covalent bonding becomes dominant because the electron excitation occurs to the B2p state. Consequently, amorphous phases are more metallic in character than crystalline phases and amorphous structures are stabilized by a mixture of more than two different bonding states.
Zinc-Oxide Film Synthesized by ECR Oxygen Plasma
Authors: Kokai Hideki , Kashiwagi Kunihiro , Sakamoto Yuichi , Morikawa Takitaro , Murayama Yoichi
Published: February 2005

ZnO films were deposited using an evaporation system with an oxygen ECR plasma. The ECR plasma was produced in an octapole magnetic field with 2.45 GHz microwave. The deposited ZnO films, which have 3.3 eV band gap, were obtamed without heating (55°C). Deposition was carried out on substrates set in two regions to examine the effect of ion irradiation; one region was in the octapole field (ion rich atmosphere) and the other was the area outside of it (ion poor atmosphere). The deposition in the ion poor atmosphere gave high quality films. The film structure was analyzed by means of optical spectrophotometer, RHEED, SEM and X-ray diffraction.
Electron Spin Resonance of Organic Radicals Derived from Amino Acids in Calcified Fossils
Authors: Kai Ayako , Miki Toshikatsu
Published: February 2005

The electron spin resonance of calcified fossils of coral, mollusk shells and bone has revealed that the quintet spectrum which was assigned to alanine radicals actually consists of 7 equally spaced hyperfine lines with isotropic spin-Hamiltonian parameters of g=2.0039 and A=2.17 mT. X-ray irradiation and subsequent heating of CaCO3 doped with L-valine yield the same septet. The septet detected in the fossils and the L-valine-doped CaCO3 is attributable to (CH3)2Ċ-radicals. Only irradiation produces nonparamagnetic precursors which alter to the radicals by postheating. A detailed model of the radical and its formation process are discussed. Multiline spectra arising in L-alanine-doped and glycinedoped CaCO3 are unlike those in irradiated L-alanine and glycine reagents. Models are proposed for the centers in the L-alanine-doped and glycine-doped CaCO3.
Gas Polarographic Humidity Sensor Usable above 100°C
Authors: Usui Toshio , Kurumiya Youichi , Ishibashi Kohsei , Nakazawa Mitsuhiro
Published: February 2005

Humidity-sensing characteristics of a gas polarographic sensor using a zirconia electrolyte were investigated in H2O-N2 gas mixtures at atmospheric temperatures of 100–160°C. The output current of the sensor was quite stable even above 100°C and increased linearly with increasing water vapor concentration up to 38%. Thus, it was found that the sensor can be used for monitoring and controlling of humidity above 100°C.
Application of Photobleachable Positive Resist and Contrast Enhancement Material to KrF Excimer Laser Lithography
Authors: Endo Masayuki , Tani Yoshiyuki , Sasago Masaru , Nomura Noburu , Das Siddhartha
Published: February 2005

In this paper, we present the application of photobleachable positive deep-UV resist and contrast enhancement material (CEM) to KrF excimer laser lithography. The effects of the photobleaching characteristics of the resist and CEM on the resist pattern angles and profiles were examined and optimization of these materials was performed. High-aspect-ratio 0.5 µm-line-and-space patterns were successfully obtained by optimization of the materials. PROLITH (positive resist optical lithography model) has excellently reproduced actual pattern profiles.
Downstream Etching of Si and SiO2 Employing CF4/O2 or NF3/O2 at High Temperature
Authors: Nagata Akiyoshi , Ichihashi Hideki , Kusunoki Yasutomo , Horiike Yasuhiro
Published: February 2005

The downstream etching reaction of Si and SiO2 employing CF4/O2 or NF3/O2 gas mixtures at high temperature has been studied. The Si etch rate of CF4/O2 downstream etching increases with increasing temperature reaching a maximum value around 15% O2 concentration; the amount of decrease in the SiO2 etch rate at higher temperatures and O2 concentrations is small. Accordingly, a reversal in Si/SiO2 selectivity is observed at 80% O2 concentration in the temperature range from 100°C to 400°C, but it is not found in the NF3/O2 case. As a result, the reversal is ascribed to F atoms involving silicon-oxide film formation on a Si surface.
Growth Kinetics of Silicon Thin Film Studied by Hydrogen Radical and Ion Irradiation
Authors: Miyazaki Seiichi , Inoue Yushi , Kiriki Yoshihiro , Hirose Masataka
Published: February 2005

Silane plasma/solid surface interactions have been simulated through hydrogen neutral and ion beam irradiation onto a thin film produced by silane radical beam condensation on a cooled substrate. The volatile chemical species created by the beam-induced surface reaction has been detected by mass spectrometry. The result showed that the hydrogen radical and ion beam irradiation causes the emission of SiH4 and H2 from the surface when the ion beam is not accelerated. It was also found that pure hydrogen neutrals induce the evolution of SiH4 and H2, and that the accelerated hydrogen ion beam produces Si2H6 molecules on the surface.
Injection-Limited Currents in Insulators
Authors: Godlewski Jan , Kalinowski Jan
Published: February 2005

A general treatment of the injection-limited currents (ILC) at the insulator intersurface, based on the continuity equation including source current, is presented. Various approximations are discussed of which the one-dimensional Onsager model is a particular case for a weak gradient source current or the injection distance approaching zero.
A coordinate-dependent geminate recombination is introduced into this model. Formal requirements leading to analytical, tractable solutions divide the electric field (F) range into two regimes: low-field regime (LFR) (F<5.2 ε
T
2 V/m) and high-field regime (HFR) (F >5.2 ε
T
2 V/m). At room temperature T=293 K and with typical dielectric permittivity ε=4, F
LFR <106 V/m and F
HFR>106 V/m. In the approximations discussed the current-field dependence is linear or sublinear in the LFR and follows the function j ∞F
3/4 exp
(a
F
1/2) (a=constant) in the HFR. Comparison of the theory with the experimental data shows that the current changes at the predicted division value of the field and shows good agreement in the HFR. In the LFR, experimentally observed ILC follow the function j ∞exp
(-b
F
-1/2) (b=constant). It is shown that it is caused by surface-trap limitation of the injection currents (STLIC).
Redistribution of Internal Energy of Molecules Scattered from Solid Surfaces
Authors: Okude Shin'ichiro , Tachikawa Maki , Shimizu Tadao
Published: February 2005

A novel experimental method for the spectroscopy of nonbeam low density gas has been developed to probe the interaction between molecules and solid surfaces. Translational and rotational temperatures of the molecules scattered from solid surfaces are measured as a function of surface temperature. The results are critically dependent on the kind of surfaces (glass, graphite, silver, mica, and molybdenum oxide). A new model describing the mechanism of energy transfer from solid surfaces to molecules is proposed. A good agreement between observation and calculation is obtained.
Low Temperature Silicon Surface Cleaning by HF Etching/Ultraviolet Ozone Cleaning (HF/UVOC) Method (II)–in situ UVOC
Authors: Kaneko Tetsuya , Suemitsu Maki , Miyamoto Nobuo
Published: February 2005

A new method to obtain clean silicon surfaces using a thermal treatment at as low as 700°C is proposed. The method consists of an ex situ treatment of HF dipping followed by a rinse in distilled, deionized water and in situ treatments of both UVOC under low oxygen pressure and annealing in vacuo. From the Arrhenius plot of the removal rate of the surface oxide, two mechanisms corresponding to a diffusion of the volatile product, SiO, and a reaction between oxygen and silicon are suggested to exist, with activation energies 3.7 eV and 1.9 eV, respectively.
Composition Dependence of Exciton Band Gaps and Edge Emissions of AgGa(S1-xSex)2
Authors: Yamamoto Nobuyuki , Mouri Atsusi , Setoyama Makoto , Horinaka Hiromichi
Published: February 2005

Composition dependence of the lattice constants and edge emissions of crystals of AgGa(S1-x
Se
x
)2 solid solution grown by the sintering method were examined in comparison with those grown by the iodine vapour transport method using sintered crystals as raw materials. Phase shift difference measurement of reflection showed a linear dependence of the band gap on composition, whereas a slight bowing characteristic was observed in composition dependence of edge emission. The shift of composition, x, during the iodine vapour transport growth and slight bowing of the edge emissions confirmed from these experiments are discussed.
Conduction Current Relaxation of Inhomogeneous Conductor II
Authors: Yamamoto Kazunao , Namikawa Hiroshi
Published: February 2005

The low-frequency dielectric relaxation of oxide glass is ascribed to Maxwell-Wagner effect due to the microscopic conducting path structure. The Maxwell-Wagner effect of a special type of inhomogeneous conductor consisting of inclined layers with different local conductivities is investigated and the following findings are made: (1) The exceptional temperature dependence of the low-frequency dielectric relaxation of some electronic conducting oxide glasses is ascribable to the effect of the local conductivity of the nonconductive region. (2) The multiple dielectric relaxation of some mixed alkali oxide glasses is attributable to a special type of conducting path structure with two kinds of conducting paths. (3) The shape of the conducting path of oxide glass is highly complicated.
Layer Thickness Calculation of In1-xGaxAs for Diffusion-Limited Liquid-Phase Growth in a Temperature-Graded Solution with Source Material
Authors: Nakajima Kazuo
Published: February 2005

A theoretical model was proposed to calculate the layer thickness of a III-V ternary crystal for diffusion-limited growth in a temperature-graded ternary solution into which solute elements were continuously supplied from a source material. This model was applied to the layer thickness calculation of In1-x
Ga
x
As in a temperature-graded In-Ga-As ternary solution with GaAs source material. It was studied by these calculation how the thickness of grown layers depends on growth parameters such as growth temperature, cooling rates of the substrate and the source material, solution length, and temperature difference between the substrate and the source material.
Photon-Stimulated Desorption of H+ Ions from Oxidized Si(111) Surfaces
Authors: Takakuwa Yuji , Niwano Michio , Nogawa Masafumi , Katakura Hitoshi , Matsuyoshi Satoshi , Ishida Hiroyuki , Kato Hiroo , Miyamoto Nobuo
Published: February 2005

Photon-stimulated desorption (PSD) experiments on oxidized Si(111) surfaces were performed to study the adsorption of hydrogen at the SiO2/Si(111) interface using synchrotron radiation. H+ is found to be the only ion product desorbing in significant quantities from the oxidized surfaces at photon energies above 20 eV. PSD spectra of H+ ions, i.e., the H+ ion desorption yield as a function of photon energy, exhibit two peaks at 23 eV and 33 eV. These peaks are interpreted in terms of Si-H bond and O-H bond breaking in a Si-H and Si-OH complex, respectively. The observed dependence of the H+ ion yield on oxidation temperature implies that the peak at 23 eV originates from hydrogen atoms adsorbed onto the so-called Pb centers at the SiO2/Si(111) interface. A comparison between the PSD and the total photoelectric yield spectra, the latter of which corresponds to the photoabsorption spectrum, is also made.
Absolute Calibration of a Normal Incidence Vacuum Spectrometer Using Synchrotron Radiation
Authors: Kubo Hirotaka , Sakasai Akira , Nishino Nobuhiro , Koide Yoshihiko , Akaoka Nobuo , Hara Makoto , Chiba Shinichi , Sugie Tatsuo , Takeuchi Hiroshi , Tanaka Kenichiroh , Maezawa Hideki , Yamaguchi Naohiro
Published: February 2005

A normal incidence spectrometer was absolutely calibrated for light 700–1250 Å in the first order and 350–650 Å in the second order using synchrotron radiation at the Photon Factory, National Laboratory for High Energy Physics. The spectrometer was equipped with a 0.4 m, 2400 grooves/mm ruled concave grating with an Al+MgF2coating and a blaze angle of 6.9°, and a multichannel detector. Synchrotron radiation was monochromatized by a 1 m Seya-Namioka monochromator, and the absolute intensity of the incident photon flux was measured with a windowless far-UV photodiode calibrated at the National Institute of Standards and Technology, USA. The error in the sensitivity calibration was estimated to be 13–35%. The spectrometer is used to study impurity behaviors in the JT-60 tokamak.
High Resolution Monochromatic X-Ray Tomography Using Synchrotron Radiation
Authors: Hirano Tatsumi , Usami Katsuhisa
Published: February 2005

We have improved the spatial resolution of X-ray computed tomographic (CT) images using monochromatic synchrotron radiation and a high resolution X-ray sensing pickup tube as a two-dimensional detector. The developed CT imaging system was used to observe nondestructively fine structures, such as cracks, and the chemical component distribution in a ceramic. A high resolution of 10 µm was obtained. The yttrium distribution in the ceramic was obtained using the difference between two CT images, above and below the absorption edge. The possibility of imaging small samples with a resolution of a few µm is described.
Transient Response of the Aharonov-Bohm Effect
Authors: Furuya Kazuhito
Published: February 2005

The transient phenomenon of the Aharonov-Bohm effect is formulated using a quantum mechanical model. As a result, it is found that the intrinsic response time is equal to the electron transit time of the ring. To apply the Aharonov-Bohm effect to high-speed devices, it is important to reduce the transit time.
Effect of Ar Gas Pressure on Magnetic Properties of Sputter-Deposited Fe–Cu Alloys
Authors: Sumiyama Kenji , Takemura Koichi , Kataoka Noriyuki , Nakamura Yoji
Published: February 2005

Magnetization and Mössbauer effect measurements were made for Fe1-x
Cu
x
alloys sputter-deposited on water-cooled substrates under Ar gas pressures, P
Ar, of 8.9 and 0.23 Pa. The scanning electron micrograph (SEM) shows a columnar structure for P
Ar=8.9 Pa and a fibrous structure for P
Ar = 0.23 Pa. A perpendicular magnetic anisotropy is observed and the coercive force, H
c, is large for P
Ar = 8.9 Pa, while an in-plane magnetic anisotropy is observed and H
c is small for P
Ar =0.23 Pa. The magnetization and average hyperfine field for P
Ar = 8.9 Pa are smaller than those for P
Ar = 0.23 Pa. These differences can be ascribed to the presence of CuFeO2, which is detected in the paramagnetic Mössbauer spectra in the Cu rich alloys formed under P
Ar = 8.9 Pa.
Analysis of Weighting Function in Transient Spectroscopy for Precise Measurement of Deep States
Authors: Kida Hirotsugu , Sakita Koichi , Nohda Tomoyuki , Yamamoto Keiichi
Published: February 2005

The weighting function in transient deep-level spectroscopy has been analyzed for precise measurement of deep states. The relation among weighting functions of different measurement modes is discussed. It is shown that unless the deep energy level is a well-defined discrete one, reconstruction of the density-of-states from the observed quantity is not straightforward and the weighting function greatly depends upon the energy dependence of attempt-to-escape frequency or capture cross section of the states. Approximate and exact methods to deduce the density-of-states are presented emphasizing that the neglect of energy dependence of the attempt-to-escape frequency brings a large error in the density-of-states estimation.
Epitaxial Growth of CdTe on GaAs(100) by RF Sputtering
Authors: Tokumitsu Yoji , Kawabuchi Akira , Kitayama Haruyuki , Imura Takeshi , Osaka Yukio
Published: February 2005

Cadmium telluride is deposited by rf sputtering on the clean surface of GaAs(100) substrates from which the surface native oxides have been etched off in advance by H2 plasma treatment. RHEED patterns of CdTe films prepared at 270°C on GaAs pretreated with H2 plasma at 120°C are streaked with (100) characteristics, which shows that the deposited layers are grown epitaxially. The crystalline quality of the CdTe films, which depends on the substrate temperature, is evaluated by means of the optical reflectance. The peak height of the second-derivative reflectance spectra, which is a measure of the crystalline quality, steeply increases at deposition temperatures of 220∼270°C. Thus a deposition temperatures of more than 270°C is needed for high crystalline quality.
Study of Charge Density Waves in 4Hb–TaS2 by STM/STS
Authors: Tanaka Masamoto , Mizutani Wataru , Nakashizu Tsuneo , Yamazaki Shuichi , Tokumoto Hiroshi , Bando Hiroshi , Ono Masatoshi , Kajimura Koji
Published: February 2005

An investigation of charge-density waves in 4Hb–TaS2 was carried out by scanning tunneling microscopy and scanning tunneling spectroscopy. We succeeded in discriminating of the surface electronic structures of 4Hb–TaS2, octahedral structure and trigonal-prismatic structure in terms of the electronic properties. The measured energy gap of the charge-density waves of 4Hb–TaS2 at room temperature was about 9± 10 meV.
Effect of Ion Bombardment on the Growth and Properties of Hydrogenated Amorphous Silicon-Germanium Alloys
Authors: Perrin Jérôme , Takeda Yoshihiko , Hirano Naoto , Matsuura Hideharu , Matsuda Akihisa
Published: February 2005

We report a systematic investigation of the effect of ion bombardment during the growth of amorphous silicon-germanium alloy films from silane and germane rf-glow discharge. Independent control of the plasma and the ion flux and energy is obtained by using a triode configuration. The ion contribution to the total deposition rate can reach 20% on negatively biased substrates. Although the Si and Ge composition of the film does not depend on the ion flux and energy, the optical, structural and electronic properties are drastically modified at low deposition temperatures when the maximum ion energy increases up to 50 eV, and remain constant above 50 eV. For a Ge atomic concentration of 37% and a temperature of 135°C, the optical gap decreases from 1.67 to 1.45 eV. This is correlated with a modification of hydrogen bonding configurations. Silicon dihydride sites disappear and preferential attachment of hydrogen to silicon is reduced in favour of germanium. Moreover the photoconductivity increases which shows that ion bombardment is a key parameter to optimize the quality of low band gap amorphous silicon-germanium alloys.
PIXE in Determination of Argon Impurity in Ion Beam Sputter-Deposited Co–Cr Films
Authors: Shoji Fumiya , Taniguchi Hideki , Kusumoto Osamu , Oura Kenjiro , Hanawa Teruo , Suzuki Yoshihiko , Ogawa Soichi
Published: February 2005

Co–Cr films prepared by the method of argon ion beam sputtering are analyzed by the proton-induced X-ray emission (PIXE) technique. The PIXE spectra show a clear peak of Ar Kα X-ray, indicating the existence of impurities. The content of argon impurity is in the order of 102 ng, and the content is found to increase as the argon ion beam energy increases and the argon pressure decreases. The argon impurity is attributed to the scattering processes of argon ions at the Co–Cr alloy target surface.
Concentration of Deep Level in InxGa1-xAsyP1-y Grown on (100) GaAs by LPE
Authors: Zhu Qin-Sheng , Hiramatsu Kazumasa , Sawaki Nobuhiko , Akasaki Isamu
Published: February 2005

The electron trap concentration and its in-depth profile have been investigated on In
x
Ga1-x
As
y
P1-y
/(100)GaAs Schottky diodes by the DLTS technique. An electron trap thought to originate from an anion vacancy took a maximum value in concentration as the As fraction reached the middle of the immiscibility region. Because of the relatively low binding energy of the alloy atoms near the middle of the immiscibility region, a large number of anion vacancies are created there. In addition, the influence of the defects in a substrate was considered to explain the higher electron trap concentration near the heterointerface.
Large Piezoelectric Effect Induced by Direct Current Bias in PMN:PT Relaxor Ferroelectric Ceramics
Authors: Pan W. Y. , Gu W. Y. , Taylor D. J. , Cross L. E.
Published: February 2005

The longitudinal piezoelectric effect induced by a direct current bias field was investigated in PMN:PT family of relaxor ferroelectric ceramics in the frequency range from 0. 1 Hz to 50 kHz. The piezoelectric d
33 coefficient was studied by measuring the strain induced by the applied electric field. Under the 10 kHz driving field, the large piezoelectric strain coefficient, d
33, of 800 pC/N is obtained. The piezoelectric strain coefficient related dielectric and electrostrictive parameters were also studied under direct current bias and the d
33 coefficient was calculated by the equation d
33=2Q
11
P
3
ε
33. The results are in good agreement with the directly measured ones. The dispersion of the piezoelectric effect is mainly due to the dielectric dispersion.
Multi Electron-Temperature Models for a Hollow Cathode Glow Discharge
Authors: Hashiguchi Seishiro , Hasikuni Mitugi
Published: February 2005

A numerical simulation is made of a cylindrical hollow cathode glow discharge in helium gas. Electrons are assumed to consist of two or three groups of different temperatures. Calculations are made for the following conditions: gas pressure of 0.24 kPa, cathode fall potential of 260 V and discharge current of 33 mA. Numerical results present number densities of electrons, ions and excited atoms of 64 excited levels as a function of the radial distance r. Experimentally determined population densities of excited atoms are also presented as a function of r. Agreement of calculation with experiment is good for densities at the center of the cathode. Calculated densities, however, have a larger peak near the edge of the negative glow than measured densities.