bluuebunny/crossref_metadata_2025 huggingface dataset:
Plasma Chemical View of Magnetron and Reactive Ion Etching of Si with Cl2
Authors: Ono Kouichi , Oomori Tatsuo , Hanazaki Minoru
Published: February 2005

Magnetron reactive ion etching and conventional reactive ion etching of Si with Cl2have been investigated in the light of the corresponding plasma properties of the discharges. Experiments were performed over a wide pressure range using a planar 13.56-MHz rf plasma reactor, with and without an external magnetic field parallel to the cathode surface. Plasma diagnostics included microwave interferometry, mass spectrometry, optical emission spectroscopy, and laser-induced fluorescence. Attention was focused on ion energies and fluxes onto the cathode and neutral radical densities in the plasma, which are related to the etching characteristics obtained. The outstanding plasma features observed are that in magnetron, the plasma density and hence the ion flux to the surface are about an order of magnitude higher, but the flux of neutral radicals is reduced relative to ions.
Al/GaAs Schottky Diode Implanted by Focused Ion Beam
Authors: Watanabe Nobuo , Tsukamoto Takeo , Okunuki Masahiko
Published: February 2005

We investigated electrical characteristics of Al/p-type GaAs Schottky diodes with carrier concentrations of 1×1017 to 3×1018 cm-3, which were produced by focused-ion-beam (FIB) implantation and by defocused-ion-beam implantation. It was confirmed experimentally that the ideality factors and the Schottky barrier heights depended on the effects of thermionic field emission. Furthermore, the possibility of the FIB implantation process for fabrication of the Schottky diode with the high carrier concentration region was recognized.
Focused Ion Beam Fabrication of Fine Metal Structures by Oxide Resists
Authors: Koshida Nobuyoshi , Wachi Hiroshi , Yoshida Kazuyoshi , Komuro Masanori , Atoda Nobufumi
Published: February 2005

It is demonstrated that 100-nm-width line patterns of refractory metals can be formed on Si substrates by a maskless process based on the combination of a focused ion beam (FIB) and high-contrast oxide resists. Thin amorphous films of MoO3 were deposited by electron beam or resistance-heated evaporation onto Si wafers, and were exposed to 30∼50 keV Ga+ FIB. Fine line patterns of MoO3, developed by chemical etching after line exposure, were reduced to Mo by heat treatment in H2 atmosphere. The linewidth before and after reduction was measured as a function of the ion dose. A study of the beam profile of the FIB indicates that the limiting resolution of this resist work is determined by the FIB diameter.
A Simulation of the Topographic Contrast in the SEM
Authors: Kotera Masatoshi , Fujiwara Takafumi , Suga Hiroshi , Wittry David B.
Published: February 2005

A simulation model is presented to analyze the topographic contast in the scanning electron microscope (SEM). This simulation takes into account all major mechanisms from signal generation to signal detection in the SEM. The calculated result shows that the resolution of the secondary electron image is better than that of the backscattered electron image for 1 and 3 keV primary electrons incident on an Al target. An asymmetric intensity profile of a signal at a topographic pattern, usually found in the SEM equipped with the Everhart-Thornley detector, is mainly due to the asymmetric profile of the backscattered electron signal.
Effect of Employing Positions of Thermal Cyclic Annealing and Strained-Layer Superlattice on Defect Reduction in GaAs-on-Si
Authors: Hayafuji Norio , Miyashita Motoharu , Nishimura Takashi , Kadoiwa Kaoru , Kumabe Hisao , Murotani Toshio
Published: February 2005

This paper describes the dependence of the dislocation density reduction effect on the employing position of either thermal cyclic annealing (TCA) or InGaAs-GaAs strained-layer superlattice (SLS) in GaAs-on-Si grown by metalorganic chemical vapor deposition (MOCVD). The dislocation density is reduced to one twenty-fifth of that in as-grown sample by the TCA as the position of TCA becomes farther than about 1.5 µm from the Si surface. The dislocation density is additionally reduced to one third by the SLS as the position of SLS becomes farther than about 2.0 µm. As a result, the dislocation density is reduced to 1.5 × 106 cm-2 by the combined use of TCA and SLS. The dislocation density reduction effect of TCA is determined mainly by the degree of residual stress. That effect of SLS is determined mainly by the degree of additional stress generated by SLS.
Influence of Effective Masses on the Oscillation of Fowler-Nordheim Tunneling in Thin SiO2 MOS Capacitors
Authors: Ono Yukinori , Makino Takahiro
Published: February 2005

The influence of effective masses on the oscillation of Fowler-Nordheim tunneling has been investigated by calculating the transmission probability of electrons through thin SiO2 film assuming effective mass approximation. As a result, the amplitude of the oscillation was found to depend on the ratio of the anode effective mass to the SiO2 conduction band effective mass. The amplitude has a minimal valley when the anode effective mass is about unity, or when the metal layer works as an anode. This result agrees well with a previous experimental report that the oscillation is strongly reduced when electrons flow into an Al electrode. The period of the oscillation depends on the effective mass of the SiO2 conduction band, whereas neither cathode nor anode effective mass dependence was found. The present calculations of the period are consistent with the previous experiment.
Microwave Properties of Inhomogeneous YBa2Cu3O7
Authors: Tateno Jun , Masaki Norio
Published: February 2005

Microwave properties of the powder specimen of high-T
c superconductor YBa2Cu3O7 were examined with the standing-wave method at 9.12 GHz. From the analysis based on the coexistence of superconductivity and dielectricity, the phenomenological penetration depth is found to be as large as 0.3 cm in the powder specimen. The temperature dependence of the penetration depth in the powder specimen resembles that of London penetration depth in the compact material. The imaginary part of the dielectric permittivity diverges at the superconducting phase transition, the origin of which can be attributed to either fluctuations or the Josephson effect.
Polarized Electromagnetic Detections by High Tc Superconducting Antenna
Authors: Ohnuma Toshiro
Published: February 2005

Detections of polarized electromagnetic waves (f=9.55 GHz) by high T
c superconducting antenna were confirmed experimentally. New results on polarization effects and the directivity of the high T
c superconducting antenna were observed.
Chlorine-Kβ X-Ray Emission Spectra from 3d Transition-Metal Chlorides
Authors: Sugiura Chikara
Published: February 2005

The chlorine-Kβ emission spectra in fluorescence from CuCl, CuCl2, ZnCl2, CrCl3·6H2O (dark green), FeCl3·6H2O (brownish yellow) and trans-[CoCl2(NH3)4]Cl are measured with a high-resolution two-crystal vacuum spectrometer and are presented along with the chlorine-K absorption-edge spectra of these compounds. The emission spectra of CuCl, CuCl2 and ZnCl2 are quite different from one another. Those of CrCl3·6H2O and FeCl3·6H2O consist of a broad band in contrast to the line-shaped spectrum of trans-[CoCl2(NH3)4]Cl. The emission and absorption-edge spectra provide information on the electronic structure in the valence and conduction bands of these compounds.
Effect of La Content on the Thermal Volume Change of Ba4.22Na1.44Nb10.12O30.24-Ba3NaLaNb10O30 Solid Solutions at Ferroelectric Transition Temperature
Authors: Shimazu Masaji , Shinya Hirokazu , Kuroiwa Shinichiro , Tsukioka Masayuki , Tsutsumi Sadao
Published: February 2005

Sintered solid solutions in the Ba4.22Na1.44Nb10.12O30.24 (BNN-B)-Ba3NaLaNb10O30 (BNLN) system have been synthesized and examined by X-ray powder diffraction and differential scanning calorimeter (DSC) analysis. The BNN(-B)-BNLN system has continuous solid solutions over the whole range, which have a tungsten bronze type of structure with pseudotetragonal symmetry. At room temperature, the a-axis increases slightly with increasing La content while the c-axis markedly decreases. The temperature dependence of the axes is characteristic in the c-axis. The thermal contraction of the c-axis occurring at the ferroelectric transition temperature is depressed with increasing La content, and in an intermediate composition, the contraction is reduced to nearly zero. The DSC analysis showed that both the transition enthalpy (ΔH
t) and the transition temperature (T
t) decrease with increasing La content.
Effect of Hydrogen on Pseudomorphic ZnSe onto GaAs by the Alternate Gas Supply of Dimethylzinc and Dimethylselenide in the MOMBE System
Authors: Kawakami Yoichi , Toyoda Takashi , Wu Yi-hong , Fujita Shizuo , Fujita Shigeo
Published: February 2005

We investigated the pseudomorphic ZnSe on GaAs grown by the alternate gas source supply of dimethylzinc (DMZ) and dimethylselenide (DMSe) in the MOMBE system. We found through the in-situ RHEED monitoring that two-dimensional nucleation occurs from the early stage of growth if the GaAs substrates are pretreated by (NH4)2S
x
solution. A growth rate of about 0.95 ML (monomolecular layer) ZnSe per one operational cycle of gas source supply could be achieved on (NH4)2S
x
-pretreated GaAs substrates at 200°C under hydrogen gas exposure during growth. This result indicates that nearly complete atomic coverage is successfully proceeded in each step as a result of the termination of alkyl radicals adsorbed on the surface by hydrogen. Crystal qualities were much improved by both the substrate pretreatment and the hydrogen gas supply.
Anomalous Change in Temperature during the Pressure-Induced Phase Transition of KI
Authors: Nomura Motoyuki , Harino Hideo , Itoh Tsukasa
Published: February 2005

Temperature changes associated with the pressure-induced phase transition of KI were observed. Two kinds of temperature signals were detected, one of which is endothermic due to the adiabatic expansion of the pressure transmitting liquid brought about by the discontinuous decrease in the sample volume. The other is an exothermic one transmitted from the sample by radiation, which means heating of a sample at the forward transition. The latter signal consists of a spike accompanied by a small but long-tailed signal. The heating at the forward transition is inconsistent with the negative slope of the phase boundary in the accepted pressure-temperature phase diagram. Although the pattern of temperature signals observed seems to support the transition mechanism of the nucleation of B2 and its growth, this mechanism contradicts the behavior of the fracture plane of KI which suggests some kind of Martesite transformation. In a reverse transition, complicated temperature signals were detected.
Local Structure of ECR Process Plasma
Authors: Miyake Shoji , Chen Wei , Ariyasu Tomio
Published: February 2005

Characteristics of an ECR process plasma produced by 2.45 GHz microwave radiation in hydrogen gas were studied, paying attention to the localized feature of ECR phenomenon in a nonuniform magnetic field. At a pressure of over 3 × 10-1 Pa, a strongly nonuniform axial temperature distribution of electrons was observed, and the temperature control was found to be possible mainly near the resonance region. It was verified that variation of the radial wall dimension of the vacuum chamber gave a remarkable influence to the plasma parameter near the resonance region. Spatial structure of the plasma in mirror and divergent magnetic field configurations was found to be nearly the same in a high-pressure-range over 1 × 10-1 Pa.
Molecular Interaction between Merocyanine Dye and Several Kinds of Triphenyl Methane Derivatives in Langmuir-Blodgett Films
Authors: Okazaki Choichiro , Kuniyoshi Shigekazu , Kudo Kazuhiro , Tanaka Kuniaki
Published: February 2005

Several triphenyl methane derivatives (TPMs) having different substituents can be adsorbed from an aqueous solution to Langmuir films consisting of arachidic acid (AR) or a mixture of AR and merocyanine dye (MC). The substituent dependence of the adsorption phenomenon shows that the adsorption mechanisms of TPM to AR and MC are mainly due to charge-charge and dipole-dipole interactions, respectively. Moreover, a peculiar property such as a negative photoelectric effect was obtained in the dye-adsorbed Langmuir-Blodgett films.
The Comparison of the Background Removal Methods in XPS Spectra
Authors: Tokutaka Heizo , Ishihara Naganori , Nishimori Katsumi , Kishida Satoru , Takabuchi Takuei
Published: February 2005

The comparison of the background lines obtained from Shirley's method and Tougaard's method was made in different energy ranges of the XPS spectrum. Tougaard's method always showed almost the same background line, even when the analyzing energy range of the spectrum was varied.
Penetration of Hypervelocity Projectile into Foamed Polystyrene
Authors: Ishibashi Toshihiro , Fujiwara Akira , Fujii Naoyuki
Published: February 2005

Spherical nylon projectiles 7 mm in diameter and 0.213 g in mass penetrated into foamed polystyrene targets of nominal densities of 11 kg/m3 (L-type), 37 kg/m3 (M-type), and 74 kg/m3 (H-type), at velocities of up to 4.3 km/s. The hole depth takes a broad maximum around the impact velocity of approximately 3.9, 1.8 and 1.5 km/s for L-type, M-type, and H-type targets, respectively, above which the fragmentation of the projectile occurs. Using L-type targets, more than 86% of the projectile mass at the impact velocity of 3.88 km/s is recovered without fragmentation. Maximum penetration depth, maximum cross-sectional area of the hole, and the target mass removed in the penetration are given as a function of the impact velocity V
i and target density ρt and expressed as ∼ρt
-1.2, ∼V
i
+2.2, and ∼E
+1.1 (E: Kinetic energy of the projectile), respectively. The latter relationship suggests that a constant proportion of the initial energy is expended to create the hole.
Electron Beam Direct Writing Technologies for 0.3-µm ULSI Devices
Authors: Moriizumi Koichi , Takeuchi Susumu , Fujino Takeshi , Aoyama Satoshi , Yoneda Masahiro , Morimoto Hiroaki , Watakabe Yaichiro
Published: February 2005

Electron beam direct writing technologies for 0.3-µm devices are studied in this paper. In order to prevent charging effects, TQV, which is a varnish consisting of 7, 7, 8, 8-tetracyano quino dimethane complex salt, has been coated on the top layer of a trilayer resist system. The effectiveness of TQV coating is indicated by the experimental results obtained from test patterns. A proximity effect correction system with several strategies to reduce the correction time and output data volume has been developed. These technologies have been adopted for the fabrication of ULSI circuit patterns with the dimension of about 0.3 µm. The calculation time and the output data volume of a proximity effect correction are reduced considerably by using new methods. It is revealed that 0.3-µm ULSI patterns can be precisely fabricated by these new technologies.
Electron Beam Direct Writing Technology for 64-Mb DRAM LSIs
Authors: Murai Fumio , Nakayama Yoshinori , Sakama Isao , Kaga Toru , Nakagome Yoshinobu , Kawamoto Yoshifumi , Okazaki Sinji
Published: February 2005

This paper describes the electron beam direct writing technology for 64-Mb DRAM LSIs including a resist process for 0.3-µm resolution, the prevention of the charging problem by a conducting polymer, and proximity effect correction by both the pattern classification method and the subsidiary exposure method. A large amount of pattern data is processed after dividing the whole chip data into peripheral circuits and 256-kb memory mats. An experimental 64-Mb DRAM LSI is fabricated by these technologies.
High-Precision X-Ray Mask Technology
Authors: Ohki Shigehisa , Yoshihara Hideo
Published: February 2005

The current status of X-ray mask accuracy around the globe is briefly reviewed, and some of the work done at NTT LSI Laboratories in order to suppress distortions caused by stresses in SiN membrane (σSiN) and Ta absorber (σTa) during the bulk-Si etching step in the subtractive process are explained. A mask-to-mask overlay accuracy of 0.09 µm (3σ) for 5 levels was attained with the conditions (1) σSiN·thicknessSiN<10 × 104 dyn/cm and (2) σSiN>σTa. With the aid of more precise stress control technology and membranes with a high Young's modulus, such as SiC, the accuracy of X-ray masks for practical use will reach at least 0.1 µm (3σ) in one or two years.
New Simulation for Wet and Dry Developable Photoresists
Authors: Tol A. J. W. , Reuhman M. E. , Maxwell G. D. , Urbach H. P. , Visser R. J.
Published: February 2005

Simulation programs can provide useful support for process understanding and the optimization of resist processes. Two new simulation programs and results are presented. One is 2 dimensional program based on solving the Maxwell equations which offers a rigorous solution for reflections on complex topograph and focus problems. And and this is for a single layer dry developable resist system.
Negative Resist for i-Line Lithography Utilizing Acid Catalyzed Silanol-Condensation Reaction
Authors: Hayashi Nobuaki , Tadano Keiko , Tanaka Toshihiko , Shiraishi Hiroshi , Ueno Takumi , Iwayanagi Takao
Published: February 2005

Negative resist systems composed of a novolak resin, diphenylsilanediol (Ph2Si(OH)2) and an acid generator are investigated for i-line lithography. The reaction in this resist system is based on an acid-catalyzed condensation reaction; the acid produced in the exposed area induces a condensation reaction of Ph2Si(OH)2 during post-exposure baking. The condensation product, siloxane, acts as an aqueous-base dissolution inhibitor, while silanol compounds in unexposed areas work as dissolution accelerators. The resist composed of a novolak resin, Ph2Si(OH)2 and 2-naphthoylmethyl-tetramethylenesulfonium hexafluoroantimonate (NMTMS-SbF6) shows a sensitivity of about 200 mJ/cm2 at 365 nm. This sensitivity is lower than that at 248 nm when triphenylsulfonium triflate (Ph3S+OTf-) is used as an acid generator, which can be ascribed to the low quantum yield of acid generation from NMTMS-SbF6. Using this resist, 0.3 µm space patterns with 1 µm film thickness were obtained by combining an i-line stepper with a phase-shifting mask.
Organotin-Containing Resists (TMAR) for X-Ray Lithography
Authors: Tanaka Youko , Horibe Hideo , Kubota Shigeru , Koezuka Hiroshi , Yoshioka Nobuyuki , Aoyama Satoshi , Watakabe Yaichiroh , Maezawa Hideki
Published: February 2005

The newly synthesized polymers containing organotin indicate higher sensitivities (2500 mJ/cm2) to synchrotron radiation X-ray (SR X-ray). The sensitivities and the imaging types depend on the amount of tin atoms incorporated in the polymers. Their resistance of the O2 gas reactive ion etching is 50 times higher in comparison with poly(methyl methacrylate) (PMMA). The results for electron beam (EB) are also reported.
Tetragonal-to-Orthorhombic Phase Transition and Superconductivity in the Y-Ba-Cu-O System
Authors: Sugai Tokuko , Oya Gin-ichiro , Imai Syozo
Published: February 2005

Fully decarbonated Y-Ba-Cu-O specimens are prepared and investigated by TG-DTA analysis and susceptibility measurement. Composition dependence of Δχ/W (susceptibility change at Tc, Δχ, normalized by the weight, W) and accordingly, that of S/W(S: magnitude of the DTA anomaly corresponding to the tetragonal-to-orthorhombic phase transition) and Tc can be explained by the change of volume fraction of the 123 phase in the specimens.
Measurement of Surface Magnetic Field of Superconductor by Magnetic Resonance
Authors: Maniwa Yutaka , Sato Hiroshi , Mizoguchi Kenji , Kume Kiyoshi
Published: February 2005

A technique for the measurement of the surface magnetic field by magnetic resonance is presented. Its application to copper oxide superconductors YBa2Cu3O7-x
demonstrated that the magnetic properties of superconductors can be conveniently investigated by this technique.
Microbeam Line of MeV Heavy Ions for Materials Modification and In-Situ Analysis
Authors: Horino Yuji , Chayahara Akiyoshi , Kiuchi Masato , Fujii Kanenaga , Satoh Mamoru , Takai Mikio
Published: February 2005

A microbeam line for MeV heavy ions of almost any element has been developed for microion-beam processing such as maskless MeV ion implantation and its in-situ analysis. Beam spot sizes of 4.0 µm × 4.0 µm for 3 MeV C2+ and 9.6 µm × 4.8 µm for 1.8 MeV Au2+ beams were obtained. Maskless MeV gold ion implantation to a silicon substrate and in-situ microanalysis before and after ion implantation were demonstrated.
Phase Diagram of YBa2Cu3O7-x, Y2Ba4Cu7O15-x and YBa2Cu4O8 Superconductors
Authors: Murakami Hirohiko , Suga Toshiaki , Noda Tamotsu , Shiohara Yuh , Tanaka Shoji
Published: February 2005

The phase diagrams of Y-system superconductors with compositions of 123 and 124 are given as a function of temperature and partial pressure of oxygen over the range 700 to 1000°C and 0.5≦P(O2)≦10 atm. The stable regions of the phases YBa2Cu3O7-x
(123), Y2Ba4Cu7O15-x
(247) and YBa2Cu4O8(124) were determined. The phase boundaries of 247/124 (starting composition of 124) and 123/124 (starting composition of 123) were found to be represented by the following equations, respectively:

log
P(O2)(atm)=(7.89±0.08)-(0.86±0.01)×104/T(K)

log
P(O2)(atm)=(12.1±1.6)-(1.25±0.18)×104/T(K).

The 123 phase is stable only in its semiconductor phase (tetragonal phase) and the superconducting phase (orthorhombic phase) is metastable at all temperatures. The 124 phase is more stable than the 123 orthorhombic phase.
Defect Thermodynamics of (La1-xSrx)2CuO4-δ Superconducting Oxide
Authors: Idemoto Yasushi , Fueki Kazuo
Published: February 2005

The oxygen deficit δ of (La1-x
Sr
x
)2CuO4-δ was determined as a function of oxygen partial pressure(P
O2
) at various temperatures. When the δ-log
P
O2
curve at a specified temperature was chosen as the reference and the curves for other temperatures were shifted along the abscissa, all the data points were found to form a single smooth curve (master curve). A theoretical equation providing δ as functions of P
O2
and strontium content was derived by combining defect equilibrium, mass action law and site conservation condition. The calculated curve was found to be in good agreement with the master curve. The relationship between copper valence and strontium content at constant oxygen pressure and temperature was determined experimentally and compared with calculated values. Good agreement was found between them.
Melting Point of Superconducting Oxides as a Function of Oxygen Partial Pressure
Authors: Idemoto Yasushi , Fueki Kazuo
Published: February 2005

The melting point of high T
c superconductors was determined as a function of oxygen partial pressure. It decreased with the decrease in oxygen partial pressure. It was concluded that the melting is a kind of reduction reaction, in the form of Solid(I) → Solid(II) + Liquid + O2. The enthalpy change ΔH
0 and the entropy change ΔS
0 for the reaction are calculated from the oxygen partial pressure independence of melting point.
Effects of Calcination and Hot-Pressing Temperatures of Magnesium Fluoride Powder on Its Optical Property
Authors: Chang Chen-Shen , Hon Min-Hsiung , Yang Sheng-Jenn
Published: February 2005

Finely dispersed magnesium fluoride powder, synthesized by a solution technique and calcined at 480–630°C, was hotpressed at temperatures varying within the range of 570–690°C. The effects of both the calcining temperature and hot-pressing temperature of MgF2 powders on the optical transmittance were investigated to determine the optimum combination temperatures to increase the transmittance in the short-wavelength region of the spectrum. It was concluded that the influence of the calcining temperature of the powder on the transmittance was less sensitive than that of the hot-pressing temperature when the hot-pressing temperature is higher than the calcination temperature. In addition, the transmission curve indicated that the extrinsic absorptance from the broad band of free water (H2O) at 2.75 µm was almost independent of calcining temperature whereas it was completely controlled by the hot-pressing temperature. The experiment showed that the broader the H2O absorption band, the higher the transmittance at the short-wavelength region of the spectrum.
Synthesis of Zr–N Thin Film by Reactive Ion Beam Sputtering
Authors: Yoshitake Masaaki , Yotsuya Tsutom , Takiguchi Katsumi , Ogawa Soichi
Published: February 2005

Thin films of Zr–N have been prepared by reactive ion beam sputtering. The relation between film properties, such as structural, optical and electrical properties, and nitrogen gas pressure and ion beam is systematically investigated. The film properties can be controlled not only by varying reactive gas pressure, nitrogen gas pressure, but also by varying sputtering ion beam current even at a constant nitrogen gas pressure. The previously proposed model of a reactive sputtering mechanism for the Zr–O system, which takes into account the gettering action of Zr atoms and deals with the number of sputtered Zr atoms and O2 molecules, is expanded to a sputtering mechanism for the Zr–N system and discussed quantitatively. The nitrogen partial pressures during sputtering calculated from the expanded model are compared with experimental results. It is found that the calculated values agree well with the experimental results.
Low Temperature Vapor Phase Epitaxy of Undoped ZnSe Films on (100) GaAs Using Metallic Zn and Se
Authors: Muranoi Tetsuo , Kurosawa Kazuhito , Yamamoto Kenji , Miyokawa Tsutomu , Shimizu Michiaki , Furukoshi Mitsuo
Published: February 2005

High-quality ZnSe films were grown at 290°C by VPE with an improved reaction apparatus: a reflection plate for Se vapor was prepared at the end of the nozzle. With this configuration, the growth rate became several times higher than that without such a plate. Exciton emissions including free exciton line were predominant. The deep level emission was very low even at RT in the PL spectrum. The electron mobility was 2410 cm2/V·s at 77 K.
Photodisplacement Measurement by Interferometric Laser Probe
Authors: Takamatsu Hiroyuki , Nishimoto Yoshiro , Nakai Yasuhide
Published: February 2005

A highly sensitive optical heterodyne interferometer was developed for the purpose of measuring the photodisplacement of a sample induced by the absorption of modulated light. The sensitivity is 1 pm in the 1 Hz bandwidth, sufficient to measure the photodisplacement. A good correlation was obtained between the amplitude of the photodisplacement and the subsurface structures of aluminum thin-film samples. The experimental results revealed that this technique is applicable to thickness measurement and to imaging of subsurface structures for opaque thin films.
Fabrication of SiO2–GeO2 Glass Optical Waveguides by the Gas-Phase Doping Method
Authors: Kondo Osamu , Hirata Masukazu , Arii Mitsuzo
Published: February 2005

A new method of fabricating silica glass optical waveguides has been developed. Porous silica glasses made by the sol-gel method were used as substrates, into which a dopant was introduced by utilizing the adsorption equilibrium between porous glass and vapor of the relevant dopant material. Index distributions within the glass were produced by placing the doped glass under reduced pressure to outgas the dopant from the surface of the glass, followed by transforming the dopant into oxide by hydrolysis, and then the porous glass was densified to give nonporous glass. Combining this method with the selective photopolymerization method, where the undesired portion of pores was clogged by polymer, 3D waveguides have been fabricated. The SiO2–GeO2 waveguides thus fabricated have index differences of more than 0.02 with the propagation loss of less than 1 dB/cm.
A New Bessel-Box Energy Analyzer for Sputtered Neutral Mass Spectrometry
Authors: Yoshikawa Hideki , Shimizu Ryuichi
Published: February 2005

A new type energy analyzer with an electron impact ionizer for sputtered neutral mass spectrometry (SNMS), which is compact enough to be mounted in secondary ion mass spectrometry (SIMS) instruments, has been developed. The compact energy analyzer, called a modified Bessel-Box, enables energy distribution of slow charged particles with different energy resolutions to be obtained by changing the ratio of voltages applied to the analyzer. Applying this system for SNMS of Al-Mg alloy under different partial pressures of oxygen, it has been confirmed that SNMS is free from oxygen enhancement, allowing the quantification of matrix elements with considerable accuracy. It has also been revealed that the space-charge effect caused by bombarding electrons becomes fairly marked, resulting in the deformation and shift of energy distributions of the postionized particles.
Enhanced Erythrocyte Sedimentation Rate and Upflow Layer in Inclined Rectangular Vessel
Authors: Toyama Yoshiharu , Dobashi Toshiaki , Sakanishi Akio , Oka Syoten
Published: February 2005

We have measured the velocity profile within the upflow layer in an inclined rectangular vessel during erythrocyte sedimentation with a microscopic video system and estimated the flow rate of the upflow. A good agreement between experimental data and the theory by Acrivos et al. was obtained. The results show that the Boycott effect or the enhanced sedimentation rate is due to the upflow in an inclined vessel.
Anomalous Diffusion of Cd in InSb
Authors: Tu S. L. , Huang K. F. , Yang S. J.
Published: February 2005

Systematic studies of Cd diffusion into InSb were performed by a two-temperature zone method with InSb substrate and Cd source temperature controlled independently. Diffusion profiles were determined by C-V measurements and were found to be anomalous as in other III-V diffusion systems. The junction depth plotted against the square root of diffusion time was not a straight line through the origin, indicating that the standard interstitial-substitutional model and the conventional Boltzmann-Matano method can not be used to analyze the result. This non-linearity in Cd diffusion in In-Sb, predicted previously by Kolodny and Shappir, was confirmed experimentally in the present work. The X
j versus √t plot can be fitted rather nicely by a model similar to that proposed previously by assuming D(X, C) as functions of both diffusion depth and time. Furthermore, a modified Boltzmann-Matano method was used to deduce the diffusion coefficients and normalized diffusion curves of Cd into InSb were obtained.
Ar Ion Laser-Assisted Metalorganic Molecular Beam Epitaxy of InP
Authors: Iga Ryuzo , Sugiura Hideo , Yamada Takeshi
Published: February 2005

Selective growth of InP by Ar ion laser-assisted metalorganic molecular beam epitaxy is reported. Trimethylindium (TMI) and triethylindium (TEI) are used as a group III source gas. Growth rate enhancement by laser irradiation occurs in the substrate temperature range of 350–480°C when TMI is used, but does not occur when TEI is used. The beam flux response time of TMI is less than 0.5 seconds, while that of TEI is as long as 30 seconds. Therefore, TMI is suitable for the selective growth of InP. It is found for the InP film using TMI that the carbon concentration of the laser-irradiated area is less than one third that of the nonirradiated area. Also, the mechanism involved in the reduction of carbon incorporation by laser irradiation is discussed.
Electrical and Optical Properties of the CuGa(S1-xSex)2 System
Authors: Matsushita Hiroaki , Endo Saburo , Nakanishi Hisayuki , Nomura Shigetaka , Irie Taizo
Published: February 2005

The mixed crystal system CuGa(S1-x
Se
x
)2 was prepared by the normal freezing method. The compositional dependence of the lattice constants and the optical band gap obeyed Vergard's law. The phase diagram of this system was studied by DTA measurement. An orange photoluminescence was observed for x≦0.5 after annealing in vacuum. It was confirmed that the emission was due to D-A pair recombinations, and an increase of S-vacancy caused an increase of photoluminescence intensity. The electrical resistivity was also affected by S-vacancy.
Compositional Change of the Au–Cu2Te Contact for Thin-Film CdS/CdTe Solar Cells
Authors: Uda Hiroshi , Ikegami Seiji , Sonomura Hajimu
Published: February 2005

The stability of thin-film CdS/CdTe solar cells with evaporated Au–Cu2Te contacts to the CdTe film has been investigated. A decrease in conversion efficiency due to an increase in series resistance was observed in the solar cells stored in air at room temperature for 120 days. The increase in series resistance is caused by an increase in contact resistance resulting from the compositional change in the Au–Cu2Te contact to the CdTe film.
An Efficient Combustion Process for Synthesis of YBa2Cu3O7
Authors: Rambabu D.
Published: February 2005

A novel combustion process which saves time and energy for the synthesis of YBa2Cu3O7 superconductor is reported. The process involves ignition of metal nitrates–urea mixture which results in an intimate mixture of partially reacted oxides. After another combustion with ammonium nitrate and urea and subsequent heat treatment and oxygenation this gives single phase superconducting YBa2Cu3O7 powder.
Trapping States in CaS and SrS Single Crystals, Films and Powders as Revealed Using the Technique of Transient Thermoluminescence
Authors: Rennie John , Nakazawa Eiichiro , Koda Takao
Published: February 2005

Trapping centres of doped and undoped CaS and SrS phosphors, in single crystal, thin film and powder forms, have been investigated by the transient thermoluminescence technique. Comparison between the forms are made, and conclusions, regarding the possible sources of the trapping centres, are postulated. The thin films specimens are found to have dramatically different trap spectra, to those observed for single crystal and powder forms. Analysis of the trapping centres, that is the determination of the trap depths, was also carried out, using the aforementioned technique, and the subsequent results compared with those reported in the literature employing the technique of thermoluminescence. The result was a favourable match. Most of the dominant trapping states in these compounds seem related to natural defects and not, directly, to the added dopants.
Spectroscopic Study on Sputtering of PLZT Thin Film
Authors: Ibuki Sumiaki , Nakagawa Taichi , Okuyama Masanori , Hamakawa Yoshihiro
Published: February 2005

An optimization of RF sputtering condition for preparation of high-quality PLZT thin film has been studied by use of spectroscopic analysis of vapor phase species and composition for deposited PLZT thin film. Relative amounts of the component elements in the sputtering vapor have been measured from optical emission spectra of the plasma. Distributions of the elements perpendicular to the surface in the deposited films have been obtained by use of ESCA. Results of the systematic analysis imply that fine control of Pb content is the key issue for higher quality film. PLZT films having a large dielectric constant of 5000 have been obtained under the sputtering condition of low RF power.
LPE Lateral Overgrowth of GaP
Authors: Zhang Suian , Nishinaga Tatau
Published: February 2005

Epitaxial lateral overgrowth (ELO) of GaP on SiO2-coated (111)B or (111)A GaP substrates was carried out successfully by LPE. It was found that the ELO of GaP showed dependency on seed orientation similar to that of GaAs. However, a pronounced asymmetry of lateral growth in [2̄11] and [21̄1̄] orientations was found. Monomolecular growth steps on the ELO layer have been observed by a Nomarski differential interference contrast microscope equipped with an image processor without decoration. Nitrogen doping was performed, and its nonuniform distribution was investigated by a fluorescence microscope and spatially resolved photoluminescence. From the nonuniformity, an understanding of the ELO mechanism was derived. It was found that the epilayer had a much lower dislocation density than that in a substrate. It was concluded that wide and extremely flat GaP epilayers with high quality can be obtained by the ELO technique.
Forming Condition of Striped and Scrolled Texture in Cholesteric Liquid Crystals
Authors: Nawa Nobuhiko
Published: February 2005

In a wedge-shaped cell with homeotropic boundary conditions, the forming process of cholesteric textures is observed under a magnetic field. It is found that the type of cholesteric texture depends on the difference between the induced pitch in the cell and the equilibrium pitch of the sample.
Kinetics of Dopant Diffusion in Poly(3-alkylthiophene) Films Studied by Chronoabsorptometric Method
Authors: Wang Shenglong , Manda Yasuhisa , Yoshino Katsumi , Tanaka Kazuyoshi , Yamabe Tokio
Published: February 2005

The kinetics of dopant diffusion in poly(3-alkylthiophene) films is studied by the determination of apparent diffusion coefficient from chronoabsorptometric curves. The diffusion coefficient during oxidation D
Ox increases with increasing electrolyte concentration and applied potential. On the other hand, the diffusion coefficient during reduction D
Red is not dependent on the electrolyte concentration. Both D
Ox and D
Red decrease with increasing alkyl chain length. From the experimental results, a model of charge-transport in poly(3-alkylthiophene) films during doping and undoping processes is proposed.
Wavenumber Measurement of the 1.5-µm Band of Acetylene by Semiconductor Laser Spectrometer
Authors: Kinugawa Shigeru , Sasada Hiroyuki
Published: February 2005

Near-infrared distributed feedback (DFB) semiconductor laser spectroscopy of acetylene has been carried out from 6450 to 6570 cm-1 with an accuracy of about 0.0033 cm-1. The molecular constants of the (1010000)–(0000000), (1011100)–(0001100), and (1010011)–(0000011) bands of 12C2H2 and the (1010000)–(0000000) and (0020000)–(0000000) bands of 12C13CH2 have been precisely determined. The transition frequencies calculated from the constants can be used as references for optical communication systems.
Effects of Surface Morphology of Transparent Electrode on the Open-Circuit Voltage in a-Si:H Solar Cells
Authors: Sakai Hiroshi , Yoshida Takasi , Hama Toshio , Ichikawa Yukimi
Published: February 2005

The open-circuit voltage of hydrogenated amorphous silicon (a-Si:H) p-i-n solar cells depends on the surface morphology of transparent electrodes and the i-layer thickness. We have studied the relationship between the V
oc and these parameters experimentally. To investigate the detailed mechanism of the V
oc drop, transmission and scanning electron microscopies (TEM and SEM) were used, and it was found by the TEM images that white stripelike defective regions were generated in the i-layer deposited on highly textured transparent electrodes. From the current-voltage characteristics of these solar cells under the dark condition, the relationship between the defects and the electrical properties of the cells has been studied. The results showed that the defect acts as a recombination center of carriers.
Electrostriction as the Origin of Piezoelectricity in Ferroelectric Polymers
Authors: Furukawa Takeo , Seo Naoya
Published: February 2005

Electric-field-induced changes in thickness have been measured interferometrically for thin films of ferroelectric VDF/TrFE copolymers. For sinusoidal fields high enough to induce ferroelectric switching, the strain x in the thickness direction draws a hysteresis loop of butterfly shape while the electric displacement D draws a conventional square D–E hysteresis loop. The x is shown to be proportional to D
2. Their ratio gives the electrostriction constant κ33 ranging from -2.1 to -2.5 m4/C2. Low-field measurements for poled samples with remnant polarization P
r yield a linear relationship between x and D. The piezoelectric constant given by the ratio x/D coincides with 2κ33
P
r, implying that the piezoelectric activity of VDF copolymers originates from electrostrictive coupling as does that of traditional ferroelectrics. The role of the dimensional effect in both piezoelectricity and electrostriction is discussed.
Cubic Crystals in Ti Films Evaporated on NaCl Substrates
Authors: Yamada Yukio , Kasukabe Yoshitaka , Yoshida Kazuhiko
Published: February 2005

The growth and structure of Ti films evaporated on NaCl substrates have been studied by electron microscopy. The film showed cubic or fcc-like diffraction spots of three types in the early growth stage, depending on the preparation method and temperature of the substrate and film thickness. The lattice parameters corresponding to those spots taken from 2 nm-thick films formed on the substrate at 260°C were a=0.441 nm, 0.418 nm and 0.426 nm, which were determined to be those of CaF2-type TiH1.5, NaCl-type TiO1.0 and some titanium compound, respectively. The former two grew on the substrate cleaved in vacuum while the last one grew on that cleaved in air, only. When the film was thicker than 3 nm, hcp diffraction spots also appeared. The formation mechanism of the cubic and hcp crystallites is discussed.
Collisional Studies Involving Discharge Emissions Relevant To Mercury Bromide Laser
Authors: Mahmood Mohammad F.
Published: February 2005

Emission of HgBr (B–X) band system and atomic mercury lines have been observed during collisions of N2(A) with HgBr2 and also with CH3HgBr molecules. On the basis of intensity of the most intense band, (0, 22) of the HgBr (B–X) transition, the efficiency ratio of the HgBr (B-state) formation due to N2(A)+HgBr2 with respect to N2(A)+CH3HgBr collisions has been determined to be 2.3:1.
Profiles of Relativistic Electron Beams Focused with High-Temperature Superconducting Lenses (Supertrons)
Authors: Matsuzawa Hidenori , Ishibashi Yoshiharu , Osada Tomoaki , Irikura Kazunori , Okamoto Kenji , Wada Haruhisa , Mochizuki Akihide , Akitsu Tetsuya
Published: February 2005

Relativistic electron beams (REBs, 310 keV, 1.5 to 3.8 kA, pulse widths of about 5 ns) were focused with high-temperature Bi- and Y-compound, straight and tapered superconducting lenses (Supertrons, inner diameters of 5, 10, and 20 mm, thickness of 1.5 mm, and axial length of 40 mm) to diameters of 2 mm or less (full width at half maximum). The gently tapered Bi-compound lens showed the highest functioning in focusing REBs with current density of more than 400 A/mm2. Radial profiles of the REBs focused were visually confirmed with open-shutter photographs of fluorescence of neon gases excited by the REBs. A bent superconducting tube guided REBs as optical fibers do. To rate the focusing ability of these lenses, a figure of merit was proposed.
Characteristics of Epitaxial Layers Grown by a New RF-Induction Heated Hot-Wall-Type Reactor for High-Volume Epitaxy
Authors: Inoue Yohsuke , Onose Hidekatsu , Suzuki Takaya
Published: February 2005

Silicon epitaxial layers grown by a newly developed RF-induction heated hot-wall-type reactor (prototype) which is capable of processing at least 20 5-inch-diameter wafers per 100 mm of stack length, have been characterized. Satisfactory uniform layers with low undoped donor concentration (∼5×1013 cm-3) and high crystalline quality have been obtained. The p+-n(epi)-n+ junction diodes exhibited almost ideal breakdown and reverse leakage characteristics. The C-t response and the quasi-static C-V measurements from Al-gate MOS capacitors showed high minority carrier generation lifetimes of 150–800 µs and interface trap level densities comparable to those of bulk CZ silicon. An increase in undoped donor concentration and a decrease in carrier lifetime caused by HCl gas addition to the growth nutrient gas were observed.
Properties of Boron-Doped Epitaxial Diamond Films
Authors: Fujimori Naoji , Nakahata Hideaki , Imai Takahiro
Published: February 2005

Boron-doped homo-epitaxial films were deposited by microwave plasma CVD on synthesized single-crystal diamonds. Boron concentration in the films was determined by the boron concentration in the reactant gases. The crystallinity of boron- doped films was found to be affected by the boron concentration in the reactant gases. The conductivity of boron doped films was determined by the concentration of boron, and the activation energy was nearly the same as for natural IIb diamonds. The effect of the surface orientation of substrates was found in the conductivity of highly doped films. The result of the Hall effect measurement indicated that the mobility of boron-doped diamond epitaxial films was 70 cm2/V·s even at 500°C.
Threshold Voltage of Gold-Doped p-MOSFET
Authors: Choe Il Yong , Kaji Hirakazu , Watanabe Kazuhito , Satoh Yoichi , Kurosu Tateki , Iida Masamori
Published: February 2005

The variation of the threshold voltage of p-channel MOSFET with gold diffusion has been investigated. Both positive and negative shifts of threshold voltage with increasing gold diffusion temperature were observed by using the silicon substrate with the resistivity of 60–80 Ω-cm. To account for both the positive and negative shifts of the threshold voltage, the theoretical curves of threshold voltage versus gold concentration were calculated.
Magnetic Ordering of fcc Fe Small Particles
Authors: Saegusa Norio , Kusunoki Michiko
Published: February 2005

The magnetic ordering state of fcc Fe small particles prepared with the gas evaporation technique was measured by57Fe Mössbauer spectroscopy. Paramagnetic state was observed at the temperatures as low as 4.2 K for the fine particle sample.
Descriptive and Theoretical Analysis of the CuCl Vapor Laser Output
Authors: Taniguchi Hiroshi , Saito Hiroshi
Published: February 2005

Characteristics of the undulation of the laser output in the 510.6 nm laser line of a discharge-pumped CuCl vapor laser have been precisely analyzed by computer simulations of the nonlinear rate equations. Measured results are reproduced well by the calculations. The exact solutions in the analysis have been compared with the results obtained after applying a small-signal approximation to the system. It is found from the results that an application of a small-signal analysis to the self-terminating copper vapor laser is effective.
X-Ray Diffraction Studies of Ni–Cr–Based Amorphous Alloys
Authors: Yu Seongcho , Lynn Jeffrey W.
Published: February 2005

The structures of the amorphous alloys with atomic percent compositions Ni68.21Cr14.22P17.22C0.35 (MBF 65) and Ni67.33Cr14.31B18.11C0.25 (MBF 80), which have similar Ni–Cr–C components, have been studied and compared by X-ray diffraction. The interference functions, atomic distribution functions, and radial distribution functions were calculated from the X-ray diffraction intensity data. The nearest-neighbor distances and coordination numbers were determined to be 2.52±0.01 Å, 12.50±0.10 for MBF 65, and 2.48±0.01 Å, 12.75±0.11 for MBF 80, respectively. The observed nearest-neighbor distance is in good agreement with a simple contact-distance packing model using the calculated atomic radii and a coordination number of twelve. These results are compared with the same composition of Ni in amorphous Ni–P and Ni–B alloys.
Chemical Vapor Deposition of Low Hydrogen Content Silicon Nitride Films Using Microwave-Excited Hydrogen Radicals
Authors: Yasui Kanji , Nasu Masaaki , Komaki Kazuki , Kaneda Shigeo
Published: February 2005

The chemical vapor deposition method using hydrogen radicals excited by microwave plasma has been applied to obtain silicon nitride (SiN) films of low hydrogen content. In this method, silane and monomethylamine were used as source gases. Various properties of deposited films such as the composition of SiN, the residual contents of carbon and oxygen, and the deposition rate were influenced by growth conditions. In the growth conditions, the distance between the center of the waveguide and the substrate was the most critical parameter because the distribution of the H radical strongly depended upon it in our experiment. For a suitable substrate position, carbon and oxygen contents could be reduced to a small value. On the other hand, residual hydrogen content was less than ∼1×1022 cm-3. This value was a quarter of that in the films grown by silane and ammonia gases under similar conditions.