bluuebunny/crossref_metadata_2025 huggingface dataset:
Application of Carbonaceous Material for Fabrication of Nano-Wires with a Scanning Electron Microscopy
Authors: Miura Naruhisa , Ishii Hideaki , Akira Yamada Akira Yamada , Makoto Konagai Makoto Konagai
Published: October 2002

Electron-beam-induced deposition (EBID) was studied for the fabrication of nanometer scale wire features (nano-wires). Residual hydrocarbon molecules in a scanning electron microscope chamber was used as a precursor and the writing conditions of carbonaceous wires was extensively investigated. A high acceleration voltage and high magnificaiton led to narrower growth of a carbon wire and a wire width of 30 nm was obtained under optimized conditions. For fabrication of conducting nano-wires, the carbon wire and a spin-coated SiO2 were employed as a dry etching mask and a nano-wire of heavily phosphorous-doped Si with a 60 nm width was successfully fabricated by this novel technique.
Preparation of CuInSe 2 Thin Films by the Pulse-Plated Electrodeposition
Authors: Saburo Endo Saburo Endo , Yasushi Nagahori Yasushi Nagahori , Shigetaka Nomura Shigetaka Nomura
Published: October 2002

CuInSe2 thin films have been prepared by the pulse-plated electrodeposition from aqueous solutions containing CuCl2, InCl3 and SeO2. The influence of the square pulse cathode potential on the film compositions, crystallinity and surface morphology has been studied. Homogeneous single phase CuInSe2 films with smooth surfaces have been obtained at a pulse potential of -0.8V vs the saturated calomel electrode (SCE), a duty cycle θ of 33%, and annealing treatment.
Proposal and Analysis of Very Short Channel Field Effect Transistor Using Vertical Tunneling with New Heterostructures on Silicon
Authors: Wataru Saitoh Wataru Saitoh , Katsuyuki Yamazaki Katsuyuki Yamazaki , Masahiro Asada Masahiro Asada , Masahiro Watanabe Masahiro Watanabe
Published: October 2002

We propose and analyze a very short channel tunneling field effect transistor using new heterostructures (CoSi2/Si/CdF2/CaF2) lattice-matched to Si substrate. In device operation, drain current from source (CoSi2) to drain (CoSi2) through tunneling barriers (Si) and channel (CdF2) is controlled by gate electric field applied to the barrier between source and channel through gate insulator (CaF2). Theoretical analysis shows that this transistor has characteristics similar to those of conventional metal- oxide-semiconductor field effect transistors even with the channel lengths of 20nm and 5nm.
Effect of Plasma Generation at Insulator Surface on Transport of Intense Electron Beam through an Insulator Beam Guide
Authors: Musuhi Hakoda Shigeo Kawata , \) \)
Published: October 2002

In our previous paper [Jpn. J. Appl. Phys. 35 (1996) L120] we presented a new feature in an intense electron beam transport system with an insulator guide. This paper presents a numerical study of the effect of plasma generation at the insulator guide surface on the transport of an intense electron beam. The plasma at the insulator surface is generated by the local electric field which is created by the beam electrons. Ion extraction from the plasma is delayed by the plasma generation time. The simulation results indicate that 1) the front of the electron beam pulse is used to generate the plasma, and 2) the electron beam transport efficiency is not totally but only slightly degraded.
Analytical Fourier Transform of Fraunhofer Hologram Pattern of a Wire
Authors: Nagayama Kunihito , Sachiko Hatano Sachiko Hatano , Keishi Nishihara Keishi Nishihara
Published: October 2002

An exact functional form of the Fourier transform of the Fraunhofer hologram pattern of a wire has been derived. Since the spatial frequency of the fringe pattern increases with distance from the symmetric axis, the same tendency is preserved in the Fourier transformed pattern of it. Although the frequency spectrum of the Fourier transformed pattern resembles that of the original hologram fringe pattern, one gets a quite different impression from the Fourier transformed image, if it is shown as an absolute value. A clear dark zone can be easily observed, which corresponds to the zero-amplitude and extremum points of the sinc function of the original hologram pattern. This property is useful for the estimation of wire diameter.
Growth of Polycrystalline Silicon Grains
Authors: Naoto Matsuo Naoto Matsuo , Tatsuo Sugiyama Tatsuo Sugiyama , Tadaki Miyoshi Tadaki Miyoshi
Published: October 2002

The relationship between the surface morphology of Si afterin situannealing carried out after a-Si deposition by low pressure chemical vapor deposition (LPCVD) and the preferred crystal orientation is examined. Dome-shaped grains are produced with <311> preferred orientations, and scrambling grains are produced at the boundaries between the <311> and <110> preferred orientations. Here, the scrambling grains are defined as some connected dome-shaped grains. Thein situannealing results in crystallization of the surface amorphous layer on the original <311> textured films. The <311> orientation factor is significantly increased after annealing. Taking into account the reciprocal reaction during thein situannealing between the polycrystalline Si (poly-Si) grains formed on the a-Si surface and the poly-Si grown from the interface between the a-Si and the SiO2substrate, the origin of the scrambling grains is discussed.
Polysilane-Based Polymer Diodes Emitting Ultraviolet Light
Authors: Ebihara Kenzo , Koshihara Shin-ya , Miyazawa Takashi , Kira Mitsuo
Published: October 2002

We show for the first time that a thin film of the organic-inorganic hybrid polymer polysilane can be used as an active element in a light-emitting diode with a large active area that generates ultraviolet light at low temperature. The thin-film device emitted 3.35 eV (370 nm) light with moderate efficiency (0.01–0.06%) at temperatures below 210 K. The origin of the emission was assigned to the 1B
u
exciton on the one-dimensional silicon chain. The reason for the decrease of the emission efficiency above 50 K was discussed in relation to the order-disorder phase transition in the polysilane thin film.
Elimination of Spherical Aberration in Grazing-Incidence Optics with Cylindrical Mirrors
Authors: Goto Yoshinori , Kaneko Takashi , Naoshi Uesugi Naoshi Uesugi
Published: October 2002

The design of an optics system consisting of four cylindrical mirrors is described. Two symmetrically installed cylindrical mirrors reduce spherical aberration. This set of cylindrical mirrors can focus vertically or horizontally. Astigmatism is also eliminated by using a second set of mirrors. The spot size of this optics system is estimated to be about 2 µm.
Direct Observation of Crystal-Originated Particles on Czochralski-Grown Silicon Wafer Surface and Effect on Gate Oxide Reliability
Authors: Ishii Hiroyuki , Shiratake Shigeru , Oka Kazuhiro , Motonami Kaoru , Koyama Toru , Izumitani Junko
Published: October 2002

We found that crystal-originated particles (COP) on a Czochralski-grown Si wafer surface consist of single pits and pair pits, using a pattern-defect inspection machine and SEM. The influence of these pits on the gate oxide reliability was studied by means of a time dependent dielectric breakdown (TDDB) test under constant voltage stress (8 MV/cm). It was clearly demonstrated that when the gate oxide thickness was around 10 nm, in the active region pair pits caused gate oxide failure, while single pits did not. It was also found that broad pair pits, formed by preferential oxidation/etching treatment, did not degrade the gate oxide reliability even when situated in the active region.
Analysis of Subpicosecond Full-Switching with a Symmetric Mach-Zehnder All-Optical Switch
Authors: Shigeru Nakamura Shigeru Nakamura , Kazuhito Tajima Kazuhito Tajima
Published: October 2002

We present subpicosecond full-switching with a symmetric Mach-Zehnder all-optical switch. To the best of our knowledge, this is the fastest all-optical switching experiment with incoherent and thus realistic, efficient optical nonlinearities. We discuss various factors which possibly limit the switching speed. Present switching speed is determined only by the rise time of interband carrier excitation. Our analysis suggests that by reducing the duration of the control pulse, faster switching in the range from 100 to 200 fs can be expected, in which control pulse broadening due to group velocity dispersion is the dominant limitation.
Ferroelectric Behavior in Poly-L-Lactic Acid
Authors: Pan Qing Yang , Shigeru Tasaka Shigeru Tasaka , Norihiro Inagaki Norihiro Inagaki
Published: October 2002

Ferroelectric behavior was observed in poly-L-lactic acid (PLLA), though its crystal structure was previously reported to be nonpolar because the molecular chains are helical. The remanent polarization (P
r) increased with increasing temperature while the coercive electric field (E
c) decreased. The remanent polarization and coercive electric field at 130° C were 96 mC/m2 and 20 MV/m, respectively. Structural change upon application of an external electric field was observed by IR analysis, XRD and DSC measurements which suggested the possibility of polarization reversal in PLLA. The pyroelectric constant of a poled sample (T
p=130° C t
p=5 min E
p=50 MV/m) at room temperature was 10 µ C/m2·K and became almost zero at the glass transition temperature, but increased again to 20 µ C/m2 ·K at 85° C, and was stable up to 140° C.
Analysis of Sheath Electric Fields in a Radio-Frequency Discharge in Helium
Authors: Choi Young Wook , Mark Bowden Mark Bowden , Katsunori Muraoka Katsunori Muraoka
Published: October 2002

Electric fields in the sheath region of a radio-frequency discharge in helium were measured using laser induced fluorescence spectroscopy. Electric field distributions and sheath widths were determined for discharges operated at pressures in the range of 0.2–1.6 Torr. The experimental results are found to be predicted well by a theory in which collisions in the sheath are dominant.
Surface Morphology Study for Hexagonal GaN Grown on GaAs(100) Substrates by Hydride Vapor Phase Epitaxy
Authors: Kimura Akitaka , Yamaguchi A. Atsushi , Sakai Akira , Sunakawa Haruo , Masaaki Nido Masaaki Nido , Akira Usui Akira Usui
Published: October 2002

The surface morphology of hexagonal ( h-) GaN layers grown by hydride vapor phase epitaxy on GaAs (100) substrates with several misorientation angles and directions was examined. The surface morphology of the h-GaN epitaxial layers was very rough on GaAs (100) exact substrates and GaAs (100) substrates misoriented toward the [111]A direction. The morphology was greatly improved on GaAs (100) substrates misoriented toward the [111]B direction, depending on the misorientation angles. The best surface morphology in our experiment was obtained on GaAs (100) substrates misoriented by 15.8° toward the [111]B direction. It was also found that a Ga-rich surface was favorable for GaN growth with good morphology.
Coloring and Bleaching Reactions of Photochromic Molecules by using a Single GaN-based Light Emitting Diode
Authors: Tsuyoshi Tsujioka Tsuyoshi Tsujioka , Minoru Kume Minoru Kume , Masahiro Irie Masahiro Irie
Published: October 2002

A single GaN-based light emitting diode (LED) induced both coloring and bleaching reactions of photochromic molecules. Coloring reactions of photochromic diarylethenes were performed using light of a short wavelength which was emitted from a GaN-based LED driven by a pulsed current, and bleaching reactions were performed using light of a long wavelength which was emitted from the LED driven by a constant current.
Simultaneous Measurement of Absorption and X-Ray Emission from Preformed Plasma Generated by Ultrashort Prepulse
Authors: Hyeyoung Ahn Hyeyoung Ahn , Hidetoshi Nakano Hidetoshi Nakano , Tadashi Nishikawa Tadashi Nishikawa , Naoshi Uesugi Naoshi Uesugi
Published: October 2002

The first simultaneous measurement of the reflectivity and the X-ray yield from the preformed plasma was performed with a fine temporal resolution between the prepulse and the main ionization pulse. Enhancement of the X-ray emission at the long temporal separation is due to the increase of the absorption of an intense ultrashort laser pulse in a preformed plasma with a scale length longer than laser wavelength. The maximum response of X-ray emission at 22.5° and the weak dependence on the polarization of input laser light infer that collisional absorption with additional resonance absorption in a nonuniform critical density profile is the main absorption process in the preformed plasma.
Two-Dimensional Island Based Model for Self-Inducing Quantum Dots
Authors: Takuya Fujii Takuya Fujii , Mitsuru Ekawa Mitsuru Ekawa
Published: October 2002

We propose a thermodynamic model which describes the formation of self-inducing quantum dots from two-dimensional islands. We assumed that the migrating atoms on the substrate surface can exist only on the surface lattice sites away from the two-dimensional islands. With this assumption, there is a maximum size of the two-dimensional islands in equilibrium with the migrating atoms. A source supply on the surface, after the islands reach the maximum size, causes size reduction of the two-dimensional islands. This size reduction induces the first-order phase transition of the two-dimensional islands to quantum dots.
Electrooptic Behavior of Free-Standing Ferroelectric Liquid Crystal Film
Authors: Sadahito Uto Sadahito Uto , Hideyo Ohtsuki Hideyo Ohtsuki , Motokazu Terayama Motokazu Terayama , Masanori Ozaki Masanori Ozaki , Katsumi Yoshino Katsumi Yoshino
Published: October 2002

Electrooptic effects in a free-standing film of ferroelectric liquid crystal have been studied. The threshold field of the electrooptic effect in the free-standing film is negligible compared with that in a sandwich cell. The response time of the electrooptic effect in the free-standing film is much shorter than that in a sandwich cell. These effects have been interpreted in terms of the strong influence of the glass surface of the sandwich cell.
Morphological and Structural Transitions in GaN Films Grown on Sapphire by Metal-Organic Chemical Vapor Deposition
Authors: Wu X. H. , Fini P. , Keller S. , Tarsa E. J. , Heying B. , Mishra U. K. , DenBaars S. P. , Speck J. S.
Published: October 2002

The structural and morphological evolution of GaN films grown by MOCVD at high temperature (1080°C) on a low temperature grown GaN nucleation layer (NL) on (0001) sapphire were studied using atomic force microscopy (AFM), transmission electron microscopy (TEM) and photoluminescence (PL) measurements. The high temperature (HT) GaN layers were found to grow by initially forming isolated truncated hexagonal islands having {10*BAR*1*BAR*1} facet planes and a top (0001) plane. The non-wetting or partial wetting behavior of the HT GaN on the GaN NL is attributed to both the roughness and predominantly cubic nature of the NL.
Purge Effect on Heterointerfaces of ZnSe/MgS Superlattices Grown by Metalorganic Vapor Phase Epitaxy
Authors: Hideki Suzuki Hideki Suzuki , Toshio Obinata Toshio Obinata , Hiroyuki Nashiki Hiroyuki Nashiki , Katsuhiro Uesugi Katsuhiro Uesugi , Ikuo Suemune Ikuo Suemune
Published: October 2002

Heterointerface properties of ZnSe/MgS superlattices (SLs) grown by -0.52pt metalorganic vapor phase epitaxy (MOVPE) are characterized using X-ray diffraction measurements and in situ monitoring of optical multiple reflection in the SL films. These studies showed the formation of MgSe-related extra interface layers in the SLs. It was found that a purge with a Zn precursor effectively suppresses the extra interface layer formation. By a purge with a Zn precursor, linewidths of the photoluminescence (PL) spectra became much narrower than those of SLs grown without purging. Monolayer exciton PL peaks were clearly observed in a SL with narrow wells. This demonstrates that a purge with a Zn precursor effectively improves the abruptness and the atomic flatness of the ZnSe/MgS heterointerfaces.
Strain Distribution near Si/NiSi 2 Interface Measured by Convergent Beam Electron Diffraction
Authors: Wakayama Yutaka , Yumiko Takahashi Yumiko Takahashi , Shun-ichiro Tanaka Shun-ichiro Tanaka
Published: October 2002

Lattice strain distribution was measured in Si (111) substrates near NiSi2 islands. Quantitative measurements with high spacial resolution were performed using convergent beam electron diffraction (CBED). Distorted and lower-symmetry CBED patterns were observed up to 2.0 µm from NiSi2 islands. We show that these CBED patterns can be accounted for by a combination of stress components with different orientations. Stresses were found to be tensile perpendicular to NiSi2 island edges and compressive parallel to them. In addition, another stress component which had a characteristic orientation was detectable within 0.5 µm of NiSi2 island edges.
Blue Electroluminescence of Substituted Polyacetylenes
Authors: Sun Runguang , Masuda Toshio , Takayoshi Kobayashi Takayoshi Kobayashi
Published: October 2002

We report blue emission from a series of alkyl and phenyl disubstituted polyacetylenes, i.e., poly(1-phenyl-1-alkynes) (PPhAs), with alkyne being n-propyne, n-butyne, and n-octyne. Blue electroluminescence from PPhAs is observed by employing a cell with an ITO (indium-tin oxide) coated glass substrate/PPhA/Mg/Al structure. The color of luminescence is changed from blue-green to pure blue and the luminescence intensity is enhanced when the length of alkyl side chain increases, while neither an alkyl nor a phenyl monosubstituted polyacetylene shows an intense luminescence. The electroluminescence efficiency of PPhAs is not efficiently improved by doping with a common electron-transporting material 2-(4-biphenylyl)-5-(4- t-butylphenyl)-1,3,4-oxadiazole (PBD).
Characteristics of Metal/Ferroelectric/Insulator/Semiconductor Structure Using SrBi 2Ta 2O 9 as the Ferroelectric Material
Authors: Nagashima Kazuhito , Hirai Tadahiko , Koike Hiroshi , Yoshihide Fujisaki Yoshihide Fujisaki , Yasuo Tarui Yasuo Tarui
Published: October 2002

We fabricated a metal/ferroelectric/insulator/semiconductor (MFIS) structure using SrBi2Ta2O9 (SBT) as the ferroelectric material for the first time. The SBT thin film on CeO2/Si (100) had (105), (110) and (200) orientation. Threshold hysteresis (called “memory window”) was observed in the capacitance-voltage ( C–V ) characteristics of this sample. The memory window was about 0.5 V. From the calculation of the C–V characteristics, it is estimated that the density of surface states at the CeO2/Si interface increases upon deposition of SBT. By X-ray diffraction (XRD) analysis, diffusion of Si to the surface of SBT was detected. In order to prevent such diffusion it may be necessary to reduce the firing temperature.
Reflection High Energy Electron Diffraction and Auger Electron Spectroscopy (RHEED-AES) Observation of Bi Desorption from a Single-Domain Si(001)2×1-Bi Surface
Authors: Kim Ki-Seon , Takakuwa Yuji , Yuji Mori Yuji Mori , Shozo Kono Shozo Kono
Published: October 2002

Bi desorption from a single-domain Si(001)2×1-Bi surface was investigated using grazing-incidence reflection high energy electron diffraction and Auger electron spectroscopy (RHEED-AES). This RHEED-AES method enabled the simultaneous measurement of both the surface structure and the surface coverage, θ Bi, during Bi desorption. As θ Bi decreased from 1 ML to 0 ML, the RHEED intensity profiles indicated several structural changes which were in accordance with previously reported structural changes. Despite these structural changes, the Bi desorption follows first-order reaction kinetics over the entire coverage range of 1 ML≥θ Bi with an activation energy of 1.54 eV.
Two-Dimensional Boron Analysis in Borophosphosilicate Glass Film Using Transmission Electron Microscope with Imaging Filter
Authors: Sekiguchi Tomoko , Kimoto Koji , Mitsui Takashi Aoyama
Published: October 2002

Two-dimensional boron concentration mapping of borophosphosilicate glass (BPSG) film has been performed using a transmission electron microscope equipped with an imaging filter. The atomic ratio of boron to silicon is obtained using core-loss electrons of boron K and silicon L23 spectra. Boron concentration increases at the BPSG/phosphosilicate glass (PSG) interface, which is consistent with the result obtained by secondary ion mass spectrometry (SIMS).
Critical Current Densities of Submillimeter Single-Grain Tl-2223 Superconducting Thin Film
Authors: Lin Han-Chi , Juang Jenh-Yih , Wu Kwong-Hsung , Gou Yih-Shung , Uen Tseng-Ming
Published: October 2002

Large single-crystalline superconducting grains of Tl2Ba2Ca2Cu3O10+
x

(Tl-2223) with sizes up to 150 µm×150 µm×1 µm are obtained on both MgO(100) and LaAlO3 (100) substrates by a single-target dc-sputtering process followed by appropriate postannealing at temperatures around 910°C. Such superconducting grains were isolated and patterned into 10-µm-wide bridges by reactive ion etching. The etching process was found to only minimally affect the transition temperature, T
c, typically around 110 K, of the films. Although there was evidence that these films were indeed two-dimensional in nature, the critical current densities, J
c, were greater than 106 A/cm2 at temperatures below 90 K. At lower temperatures, e.g., T=30 K, the J
c value of these films remains well above 106 A/cm2 even with magnetic fields as large as 7 T applied parallel to the c-axis of the grains. The results are in sharp contrast to the low J
c values expected from the low-dimensionality nature of this system.
Joule Heating of a Low-Pressure Plasma Jet by means of an Applied Magnetic Field
Authors: Taniguchi Kazuhiko , Fukumoto Naoyuki , Masayoshi Nagata Masayoshi Nagata , Tadao Uyama Tadao Uyama
Published: October 2002

The effect of a pulsed magnetic field upon various low-pressure plasma jets was investigated using a system of double probes. The results indicated that both the electron temperature and density of plasma are increased, due to the effect of Joule heating currents induced in the plasma. This method provides a means of equilibrating an initial jet distribution of plasma that is in thermal non-equilibrium, yielding a new application in plasma processing.
Controlled Quantum Confinement Potentials in Self-Formed InGaAs Quantum Dots Grown by Atomic Layer Epitaxy Technique
Authors: Mukai Kohki , Nobuyuki Ohtsuka Nobuyuki Ohtsuka , Mitsuru Sugawara Mitsuru Sugawara
Published: October 2002

The present work deals with the control of quantum confinement potential in self-formed In0.5Ga0.5As/GaAs quantum dots. The dots were grown by alternate supply of (InAs)/(GaAs) precursors using atomic layer epitaxy technique. As the number of supply cycles increased from 9 to 30, dot size observed by transmission electron microscopy increased from 20 to 32 nm in diameter and photoluminescence (PL) spectra shifted to lower energy. Measuring PL spectra under a magnetic field, we found that the smaller the dots, the smaller the diamagnetic shifts. These results indicate that the quantum confinement potential was controlled in our growth technique.
Controlled Tilted Homeotropic Alignment of Liquid Crystals for Display Applications
Authors: Vithana Hemasiri , David Johnson David Johnson , Philip Bos Philip Bos
Published: October 2002

A new method to obtain nearly homeotropic alignment with small pretilt angles off the substrate normal employing vacuum oblique evaporation of SiOxhas been developed. Selected pretilt angles in the range of (0–5) degrees can be easily obtained with this method and it is not very sensitive to the deposition angle, angle between the substrate normal and the direction of evaporation, or the SiOxlayer thickness, giving the flexibility of preparing very clean alignment layers on large area substrates. This could be useful in making high contrast liquid crystal light valves for projection displays and multi-domain liquid crystal displays.
Thermochromic V1-xWxO2 Thin Films Prepared by Wet Coating Using Polyvanadate Solutions
Authors: Takahashi Ikuya , Mitsuhiro Hibino Mitsuhiro Hibino , Tetsuichi Kudo Tetsuichi Kudo
Published: October 2002

Metallic vanadium powder was dissolved in a hydrogen peroxide solution, yielding a hydrosol based on a polyvanadate. A polycrystalline thin film of VO2 was fabricated on a fused silica substrate by spin-coating using this hydrosol followed by reduction in hydrogen and additional post-annealing in a nitrogen atmosphere. The thin film showed a sharp semiconductor-to-metal transition and concomitant thermochromic switching at 67° C. Tungsten-doped thin films ( V1-
x

W

x

O2) were easily fabricated by a similar technique. The transition temperature of a doped film with x=0.015 was as low as 36° C.
Spectroscopic Measurements of a High-Concentration Yb 3+:LiYF 4 Crystal
Authors: Noboru Uehara Noboru Uehara , Ken-ichi Ueda Ken-ichi Ueda , Yoshinori Kubota Yoshinori Kubota
Published: October 2002

We describe the spectroscopic measurements of Yb3+:LiYF4 crystal at room temperature. The absorption and the emission spectra are measured with a 40.5 at% Yb3+ doped crystal. A maximum absorption coefficient of 42 cm-1 for the π polarization is measured at 960 nm with a spectral fullwidth of 12 nm. The upper-state (2
F
5/2) lifetime is measured to be 2.0 ms. The emission cross section at an oscillation wavelength of 1018 nm for the π and the σ polarizations are measured to be 5.3 ×10-21 cm2 and 4.7×10-21 cm2, respectively. The ground-state absorption coefficient at 1018 nm for the π and the σ polarizations are measured to be 4.0 cm-1 and 1.6 cm-1, respectively.
Nematic Liquid Crystals with Polar Ordering Formed from Simple Aromatic Polyester
Authors: Watanabe Toshiyuki , Miyata Seizo , Furukawa Tomoo , Takezoe Hideo , Nishi Takuya , Sone Masato , Migita Ayako , Watanabe Junji
Published: October 2002

In this study, we describe a distinct nematic liquid crystal with polar ordering which is formed from the polar rod-like aromatic copolyester comprising 4-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid. The polarity in the nematic phase appears along the nematic director as determined by second-harmonic generation (SHG). It was found that SHG activity appears in compounds with a high degree of polymerization. This suggests that the strong dipole-dipole interaction between polar rod-like molecules is the origin of the polar structure.
Second- and Third-Harmonic Generation from Optically Trapped Liquid Crystal Droplet
Authors: Naoto Tamai Naoto Tamai , Takashi Ito Takashi Ito , Hiroshi Masuhara Hiroshi Masuhara
Published: October 2002

Optical trapping of micrometer-sized nematic and ferroelectric liquid crystal droplets in water was found to induce second- and third-harmonic generation. At high trapping laser power, an increase in the second-harmonic intensity over the predicted value was observed for both types of liquid crystal droplets. Size-dependent second-harmonic generation was found only for ferroelectric liquid crystal droplets. Possible interpretations of the nonlinear effect on liquid crystal droplets were discussed.
Thermal Simulation Analysis of Scanning Near-Field Optical Microscope Point Heating Mechanisms
Authors: Miyamoto Mitsuhide , Shintani Toshimichi , Sumio Hosaka Sumio Hosaka , Ryo Imura Ryo Imura
Published: October 2002

We performed thermal simulation of nanostructure modifications through point heating of phase-change materials using a scanning near-field optical microscope (SNOM). As the recording process, two major heating mechanisms were considered: direct heating by near-field light and thermal conduction from the SNOM tip heated by the incident light. The temperature increases in the sample due to these heating mechanisms were calculated for GeSbTe phase-change thin films. It was found that thermal conduction from the tip was the dominant process for heating and its temperature increase was more than three times larger than that of direct heating by near-field light.
Production of Various Fullerenes by Arc Discharge under Repetitive Weak Gravitational Field
Authors: Tetsu Mieno Tetsu Mieno
Published: October 2002

Arc discharge under a repetitive weak gravitational field is carried out using a vertically swinging arc reactor. By means of synchronous modulation of discharge current with modulated gravitation, long-time arc discharge equivalent to that under weak gravitational field is realized. Suppression of heat convection in the weak gravitation extends the reaction time of carbon molecules in hot gas atmosphere and increases the relative abundance of higher fullerenes.
In Situ Surface Characterization of YBa2Cu3O7-x Thin Films Grown by Pulsed Laser Deposition
Authors: Nakamura Takao , Hiroshi Inada Hiroshi Inada , Michitomo Iiyama Michitomo Iiyama
Published: October 2002

C-axis oriented YBa2Cu3O7-
x

(YBCO) thin films were grown by pulsed laser deposition and characterized by in situ X-ray photoelectron spectroscopy (XPS), low-energy electron diffraction (LEED) and low-energy ion scattering spectroscopy (LEISS). There existed a degraded layer at the surface of as-deposited YBCO film in contrast with the case of YBCO film grown by an ozone-assisted molecular beam epitaxy method. High background intensity of the LEED pattern and indistinctive LEISS spectra suggested that this degraded layer has poor crystallinity. This degraded layer was caused by impurities in the oxygen gas during film deposition.
Thermal Conductivity of Amorphous Silicon
Authors: Hiroshi Wada Hiroshi Wada , Takeshi Kamijoh Takeshi Kamijoh
Published: October 2002

We measured the thermal conductivity of amorphous silicon using a new simple steady state method implementing deposited Pt stripes as both resistive heaters and temperature monitors. Amorphous Si films were sputtered on Si substrates and heat was injected through the Pt resistive heaters. The increase in heater temperature was determined by the temperature-dependent electrical resistance of the Pt stripes. We thus determined the thermal conductivity of a-Si at room temperature to be 1.8 W/m·K, which is about one-hundredth of that of crystal Si. This information is very important to properly design the thermal resistance of long-wavelength surface emitting lasers which use the a-Si in high-reflective stack mirrors.
Magnetic Anisotropy Caused by the Directivity of Ni Grown in Amorphous Ni–P Alloy due to Abrasion
Authors: Motokazu Yamamoto Motokazu Yamamoto , Noriko Nakamura Noriko Nakamura , Yi Zhao Yi Zhao , Norio Hasegawa Norio Hasegawa , Nobuyoshi Watanabe Nobuyoshi Watanabe
Published: October 2002

Abrasion of amorphous Ni–P alloys induces crystallization of the alloys. When an amorphous Ni–P alloy is abraded by abrasive particles, heat is generated locally on its surface and grooves are formed in the direction of abrasion. The heat generated by friction causes structural transformation of the amorphous Ni–P alloy, resulting in the formation of Ni and Ni5P4 crystals along the grooves. Magnetic hard disks are fabricated by abrading an amorphous Ni–P substrate in the circumferential direction and sputtering CoNiCr/Cr on the abraded surface. It has been reported that the fabricated hard disks have magnetic anisotropy and high coercivity. It is considered that the magnetic anisotropy is caused by the Ni particles grown along the grooves of the amorphous Ni–P surface.
Observation of Cross Sections of Plasma-Polymerized Films of Benzene and Naphthalene by Electron Spectroscopic Imaging
Authors: Kiyoshi Yase Kiyoshi Yase , Shin Horiuchi Shin Horiuchi , Mutsumasa Kyotani Mutsumasa Kyotani , Kazuhiro Yamamoto Kazuhiro Yamamoto , Akira Yaguchi Akira Yaguchi , Yutaka Futaesaku Yutaka Futaesaku , Toshihiro Suwa Toshihiro Suwa , Masa-aki Kakimoto Masa-aki Kakimoto , Yoshio Imai Yoshio Imai
Published: October 2002

Plasma-polymerized films of benzene and naphthalene were prepared by direct current (D.C.) glow discharge. The chemical structures of the films were characterized by IR and Raman spectroscopy, electron energy loss spectroscopy (EELS), and electron spectroscopic imaging (ESI). With increasing D.C. voltage, the hydrogen-free carbon films consisting of sp2 bonded carbon tended to change to sp3 bonded carbon. Successive plasma-polymerization with different D.C. voltages for benzene and naphthalene on poly(ethylene terephthalate) (PET) film yielded double-layer films consisting of sp2 and sp3 bonded carbons, respectively. Observation of cross section of the film by ESI yielded clear images of the heterostructure.
NOx Sensing Characteristics of Bi17Sr16Cu7Oz
Authors: Ayumi Nozaki Ayumi Nozaki , Mitsunobu Wakata Mitsunobu Wakata , Takashi Yoshida Takashi Yoshida , Fusaoki Uchikawa Fusaoki Uchikawa
Published: October 2002

We measured the electrical resistivity change of Bi-based cuprates in various gases. A ceramic formation process and a thin film deposition process based on the laser ablation method were used to prepare samples. It was found that the compound Bi17Sr16Cu7O

z

had a selective sensitivity to nitrogen oxide (NO). The resistivity of the compound was measured in atmospheres containing carbon monoxide (CO) or propylene ( C3H6) as the encountered gases. The resistivity change was negligible in those gases. This compound absorbed large quantities of NO gas and the resistivity increased with increasing NO concentration.
(111) Twins in BaTiO3 Thin Films Deposited by RF Magnetron Sputtering
Authors: Jang Jin Wook , Kim Young Hwan , Hahn Taek Sang , Choi Sang Sam , Su Jin Chung Su Jin Chung
Published: October 2002

Polycrystalline BaTiO3 thin films were prepared by rf magnetron sputtering and twin structures in the thin films were investigated using a transmission electron microscope. (111) twin boundaries were found in the thin films with thicknesses of 2100 and 10000 Å. Not only single twin boundaries but (111) twin lamellae with a very narrow width of ≈1 nm were observed in thin films of both thicknesses. This result suggested that the twin lamellae would be stable although the interfacial energy appeared to be much higher than single twin boundaries. A correlation between twin lamella width and grain size was also found.
Preparation of SnO 2 Thin Films by Plasma-Assisted Metalorganic Chemical Vapor Deposition
Authors: Sho Shirakata Sho Shirakata , Atsumi Yokoyama Atsumi Yokoyama , Shigehiro Isomura Shigehiro Isomura
Published: October 2002

Polycrystalline SnO2 thin films have been prepared by the low-pressure plasma-assisted metalorganic chemical vapor deposition technique using tetrabutyltin (TBT) and oxygen as reactant gases. RF glow discharge during growth effectively enhances the thin film growth. Structural and electrical properties of the SnO2 films have been studied with relation to RF power, substrate temperature and the flow rate ratio of O2 to TBT. Highly (200)-oriented SnO2 films with Hall mobility of 20 cm2/V·s and electron concentration of 1019 cm-3 have been obtained at the substrate temperature of 400°C.
Nanocrystalline Soft-Magnetic Fe–Zr–B–Cu Composites by Consolidation of Amorphous Powders Coated with Oxide Film through Sol–Gel Process
Authors: Kawamura Yoshihito , Akihisa Inoue Akihisa Inoue , Tsuyoshi Masumoto Tsuyoshi Masumoto
Published: October 2002

To improve the soft-magnetic properties of nanocrystalline Fe–Zr–B bulk compacts, nanocrystalline soft-magnetic composites with full density have been fabricated by hot-pressing the amorphous powder coated with SiO2 thin film through the sol–gel process. The nanocrystalline composites exhibit better soft-magnetic properties at higher magnetic induction B
m and higher frequency f than the uncoated powder compacts. The saturation magnetization B
s, coercive force H
c, effective permeability µ e and core loss W
h at f=50 kHz and B
m=0.2 T were 1.50 T, 39 A/m, 240 and 1200 W/kg, respectively. These results indicate the possibility of producing nanocrystalline soft-magnetic bulk cores with complex shapes for high-frequency AC applications.
Bonding Temperature Dependence of Optically Controlled Field-Effect Transistor Fabricated by Direct Wafer Bonding Technique
Authors: Takayuki Sakai Takayuki Sakai , Kazuhiko Shimomura Kazuhiko Shimomura
Published: October 2002

An optically controlled field-effect transistor (FET) in which the GaAs FET region and the GaInAs/InP light absorption region were directly bonded was demonstrated. The temperature dependence of the direct bonding and its effect on the performance of the optically controlled FET were examined. A maximum current modulation rate of 60% and a responsivity of more than 150(A/W) were obtained.
Translational Phase Domains in the Cation Sublattice of Chalcopyrite Compounds
Authors: Yamada Akimasa , Fons Paul , Niki Shigeru , Makita Yunosuke , Hajime Shibata Hajime Shibata , Hiroyuki Oyanagi Hiroyuki Oyanagi
Published: October 2002

There are four unique choices of cation origin in the chalcopyrite conventional unit cell. Three of these choices correspond to [1/2, 1/2, 0], [1/2, 0, 1/4] or [0, 1/2, 1/4] translations of the standard cell. If two of these domains coexist, a domain boundary is formed. Coexistence of different domains can occur when a chalcopyrite compound is grown epitaxially on a zincblende structure substrate. In this case there are two possible domain boundary types. Although each cation is bound to four anions at the phase boundaries as elsewhere in the crystal, the total valence due to the four cations neighboring an anion causes a charge anomaly at the translational phase domain boundary.
Novel Scanning Probe Microscope for Local Elasticity Measurement
Authors: Ryo Yamada Ryo Yamada , Shen Ye Shen Ye , Kohei Uosaki Kohei Uosaki
Published: October 2002

A novel scanning probe technique was developed by combining an atomic force microscope (AFM) and a quartz crystal resonator (QCR). The resonant frequency of the QCR increased when the AFM tip was placed in contact with the QCR surface and increased further when the force applied to the QCR surface increased. The frequency increase depended on the material with which the tip was in contact and seemed to reflect the local elasticity of the sample. Imaging of the material distribution on a surface was demonstrated for a pattern of polymer and gold by mapping the frequency shift of the QCR as a function of the horizontal position of the AFM tip while scanning the AFM tip over the QCR surface in constant force mode.
High Precision Heat Capacity Measurement by Dynamic Differential Scanning Calorimetry
Authors: Ichiro Hatta Ichiro Hatta , Satoshi Muramatsu Satoshi Muramatsu
Published: October 2002

We developed a novel method for measuring heat capacity with high precision by use of the modulated mode (or ac mode) in dynamic differential scanning calorimetry (dynamic DSC). For this purpose, we placed a pan with a sample on the sample side and no pan on the reference side. The thermal system was analyzed, taking into account a thermal resistance between the sample pan and the base plate; this quantity is indispensable in dynamic measurements such as differential scanning calorimetry and dynamic DSC, but is difficult to estimate. From the theoretical analysis, it was found that the calibration constant required for heat capacity determination is strictly given in terms of a relation of the amplitude ratio of ac temperatures vs their phase difference even if there is the thermal resistance.
1 µm-Long Amorphous-Silicon Thin-Film Transistors with Wide Dynamic Range
Authors: Chang-Dong Kim Chang-Dong Kim , Masakiyo Matsumura Masakiyo Matsumura
Published: October 2002

1 µ m-long amorphous-silicon thin-film transistors with a distributed-threshold-voltage (DTV) structure have been evaluated in detail, for the first time, and found to have sufficiently low cut-off characteristics, simultaneously with good turn-on characteristics. The dynamic range, that is, the on/off current ratio, was as high as 8 orders in magnitude. This favorable property is due to the partially doped channel in the DTV structure and the selectively polycrystallized Si source and drain.
Low-Threshold 1.5 µm Quaternary Quantum Well Lasers Grown by Solid Source Molecular Beam Epitaxy
Authors: Savolainen Pekka , Toivonen Mika , Asonen Harry , Murison Richard
Published: October 2002

We report the growth and characterization of low-threshold 1.5 µ m wavelength strained-layer InGaAsP/InP separate confinement heterostructure multi-quantum well lasers grown by solid source molecular beam epitaxy. Valved crakcer cells were used to supply group V fluxes of As2 and P2. A threshold current density of 387 A/cm2 was achieved for a 1440 µ m long broad-area laser having 5 QWs. A low threshold current of 18.5 mA was measured for a 5×280 µ m2 as-cleaved ridge waveguide laser. These results are fully comparable to the results for similar devices grown by other techniques.
Self-Formed InGaAs Quantum Dot Lasers with Multi-Stacked Dot Layer
Authors: Shoji Hajime , Nakata Yoshiaki , Mukai Kohki , Sugiyama Yoshihiro , Sugawara Mitsuru , Naoki Yokoyama Naoki Yokoyama , Hiroshi Ishikawa Hiroshi Ishikawa
Published: October 2002

Systematic investigation of lasing characteristics of self-formed InGaAs quantum dot lasers with multi-stacked dot layer is reported. We show that the lasing wavelength is strongly dependent on the number of quantum dot layers and the cavity length. Discontinuous shifts of the lasing wavelength from a high-order subband to a lower-order subband are clearly observed with increasing number of quantum dot layers and with decreasing cavity loss. The possibility of lasing at the ground state of quantum dots is also quantitatively discussed.
Effect of Oxygen Additive on Microwave Plasma for Diamond Film Synthesis Studied by the Plasma Impedance Measurement
Authors: Miyake Hitoshi , Sugahara Ken-ichi , Kobayashi Takeshi , Kondo Kazuki , Taniguchi Michio , Sugiyo Masato
Published: October 2002

We have developed a new microwave-plasma-assisted chemical vapor deposition (CVD) system for diamond film synthesis, which includes a real-time monitor of the plasma impedance in the microwave circuit. This impedance measurement facilitated much the noncontact diagnosis of hydrogen-based CVD plasmas. It appeared that, with increasing the excitation energy, the impedance moved from capacitive to slightly reactive complexs. With high sensitivity and cleanliness, the impedance measurements revealed that the addition of a small amount of oxygen to the hydrogen plasma increased the plasma density.
Polymeric Bipolar Thin-Film Transistor Utilizing Conducting Polymer Containing Electron Transport Dye
Authors: Kazuya Tada Kazuya Tada , Hiroshi Harada Hiroshi Harada , Katsumi Yoshino Katsumi Yoshino
Published: October 2002

A polymeric bipolar TFT with a single channel layer has been successfully realized. In the present TFT, a single interpenetrating network channel layer, consisting of PAT12 and electron transport dye, was formed by spin-coating. The current-voltage characteristics of the TFT are qualitatively similar to those of a heterostructure bipolar TFT. The interpenetrating network TFT has some advantages in fabrication compared with the heterostructure TFT.
Photoluminescence Wavelength Dependence on Layer Structure of GaP/AlP Modulated Superlattices
Authors: Kim Joon Hong , Asahi Hajime , Doi Kenji , Kumiko Asami Kumiko Asami , Shun-ichi Gonda Shun-ichi Gonda
Published: October 2002

In the (GaP)

m
1(AlP)

n
1(GaP)

m
2(AlP)

n
2 (m=m1+m2, n=n1+n2, m1≥m2, n1≥n2) modulated superlattices (SLs) grown on (001) GaP substrates by gas-source molecular beam epitaxy, a blue shift of 4.2 K photoluminescence (PL) peak is observed with decreasing the wide periods of (m1+n1). It is suggested that holes and electrons are localized in the wide GaP (m1) and AlP (n1) layers, respectively, and that the PL peak wavelength is mainly determined by the wide SL periods of (m1+n1). This suggestion is supported by the observed PL peak wavelengths for the {(GaP)11(AlP)3}

j

{(GaP)2(AlP)2}2 and (GaP)5(AlP)5{(GaP)2(AlP)2}

k

modulated SLs, where the wavelengths are almost independent of j and k.
Thermal and Electronic Transport Properties of Single Crystal PtSb 2 Obtained by the Photoacoustic Method
Authors: Nikolić Pantelija M. , Vujatović Stevan S. , Todorović Dragan M. , Miletić Milan B. , Golubović Aleksandar , Bojičić Aleksandar I. , Kermendi Ferenc , Durić Stevan , Radulović Katarina T. , Elazar Jovan
Published: October 2002

Single crystal PtSb2 ingots were synthesized using the Bridgman technique. Electronic transport properties and thermal diffusivity of PtSb2 sample were determined using the photoacoustic (PA) method with transmission detection configuration. The excess carrier lifetime, the recombination velocity and thermal diffusivity were determined by comparing the experimental results and theoretical photoacoustic signals.
Raman and Electrical Characterizations of a-GaAs1-xNx Thin Films Grown on c-Si(p) Substrates by N2 Reactive Sputtering
Authors: Bandet Jaqueline , Aguir Khalifa , Lollman Dave , Abdelhak Fennouh Abdelhak Fennouh , Hervé Carchano Hervé Carchano
Published: October 2002

In this paper, we report on electrical properties and Raman scattering of amorphous GaAs1-
x

N

x

deposited on p-type crystalline silicon (c-Si(p)) substrates. The aim of this study is the investigation of the dielectric character of GaAs1-
x

N

x

in view of its applications in MIS structures. The “compound” GaAs1-
x

N

x

is obtained by reactive RF sputtering of a GaAs target. The electrical characteristics of the a-GaAs1-
x

N

x

/c-Si(p) heterostructures present a MIS-like structure behaviour with some imperfections. Raman scattering points out that a-GaAs1-
x

N

x

is a wide gap material which is formed by the substitution of arsenic by nitrogen in the GaAs network. For substitution ratios below 25–30%, the material obtained would be an alloy whose vibrational behaviour is a single mode. Beyond 30%, it would be in a very inhomogeneous phase, infact polyphased, and would present a phase of hexagonal origin (GaN).
Phase Stability, Dielectric and Piezoelectric Properties of the Pb(Sc1/2Nb1/2)O3–Pb(Zn1/3Nb2/3)O3–PbTiO3 Ternary Ceramic Materials
Authors: Yamashita Yohachi , Hosono Yasuharu , Ichinose Noboru
Published: October 2002

The crystal structure and electrical properties of
x
]r
m
P
b(S
c
1/2
N
b
1/2)O
3–
y

P
b(Z
n
1/3
N
b
2/3)O
3–
z

P
b
T
i
O
3 (PSZNT 100x/100y/100z) ternary ceramic materials have been systematically investigated. Stable perovskite-phase ceramics are obtained with less than 20 mol% of Pb(Zn1/3Nb2/3)O3 and more than 50 mol% of PbTiO3. Piezoelectric properties were found to peak at PSZNT 31/40/29, where the electromechanical coupling factor k
p is 60%. The dielectric constant is 2,020, and Curie temperature (T
c) is 222 °C. An interesting property of PSZNT is a nonlinear T
c change in terms of the composition. T
c decreases with increasing PbTiO3 content in the range 0.3>z>0 and then increases with z>0.3. This nonlinear change in T
c is explained as a site preference of Zn ions in the PSZNT system.
A Model Describing the Rubbing Energy Dependence of the Pretilt Angle in Nematic Liquid Crystals
Authors: Cnossen Gerard , Florent N. Lagarde Florent N. Lagarde , Nick A. J. M. van Aerle Nick A. J. M. van Aerle
Published: October 2002

The dependence of the nematic liquid-crystal (LC) pretilt angle on the applied rubbing energy was measured for two commercially available polyimide alignment materials. The rubbed polyimide is described in terms of an oriented top layer and an isotropic bottom layer. The rubbing energy was quantified by the thickness of the top layer oriented by rubbing. This thickness was revealed by optical retardation measurements. A close correlation was found between the pretilt angle of the LC and the rubbing-oriented top layer thickness. The resulting anchoring properties are explained in terms of van-der-Waals interactions between the LC molecules and both the oriented polyimide top layer and the isotropic polyimide bottom layer. A prediction for the rubbing-energy dependence of the polar anchoring energy follows from the theory.