bluuebunny/crossref_metadata_2025 huggingface dataset:
Solid-Phase Reactions in Al Alloy/TiN/Ti/Si Systems Observed by In Situ Cross-Sectional TEM
Authors: Sobue Susumu , Mukainakano Shinichi , Ueno Yoshiki , Tadashi Hattori Tadashi Hattori
Published: October 2002

The mechanism of solid-phase reactions for multilayers of Al-1%Si-0.5%Cu/TiN/Ti/n+-Si substrates has been investigated by means of in situ and high-resolution/analytical cross-sectional transmission electron microscopy (X-TEM). We have succeeded for the first time in real-time observation of the instant of barrier breakdown of the TiN layer. An intermediate Al-Ti-Si(-N) layer ( ∼4 nm thickness) composed mainly of microcrystallites was formed at the Al alloy/TiN interface at ∼450° C, and the microcrystalline phase grew along the TiN grain boundaries. At over ∼500° C, the Al diffused downward very rapidly through the TiN layer, forming an Al region under the TiN layer. It is concluded that the rapid redistribution of the Al may be caused by movement along the TiN grain boundaries in the microcrystalline state.
In Situ Direct Imaging of Scanning Tunneling Microscope Tip Apex
Authors: Heike Seiji , Hashizume Tomihiro , Yasuo Wada Yasuo Wada
Published: October 2002

In situ and direct imaging of the scanning tunneling microscope (STM) tip apex is made possible by nano needle structures grown on the sample surface (needle formation and tip imaging: NFTI). The nano needle structures, which extend several nms and are sharper than the tip, are formed on the silicon(111)7×7 surfaces by applying high negative voltages to the tip. The relationship between the tip apex feature and the STM image is investigated and it is experimentally confirmed that an atomically sharp tip apex results in STM images with atomic resolution.
Estimation of the Emission Barrier Height of p-Type Semiconducting Diamond from its Field Emission Property
Authors: Ken Okano Ken Okano , Satoshi Koizumi Satoshi Koizumi , Junji Itoh Junji Itoh
Published: October 2002

The emission barrier height of p-type semiconducting diamond has been estimated relatively by comparing the field emission property of a diamond field emitter array (FEA) and a molybdenum (Mo) FEA having the same geometry. Diamond FEA showed lower turn-on voltage than Mo FEA in the emission current-anode voltage characteristics. The slope ratio of diamond FEA to Mo FEA in Fowler-Nordheim (F-N) plots yielded the emission barrier height ratio of the diamond to Mo as 0.44 ±0.06. From the obtained ratio, the emission barrier height of the diamond can be estimated to be 1.87 ±0.26 eV when the work function of Mo (4.24 eV) is assumed.
Novel Technique to Form Pt-Silicided Shallow p+n Junctions Using Low-Temperature Processes
Authors: Ma Kuo-Peng , Lin Cheng-Tung , Huang-Chung Cheng Huang-Chung Cheng
Published: October 2002

By implanting BF2
+ ions into thin polycrystalline Si films with subsequent low-temperature (as low as 500° C) annealing, excellent Pt-silicided shallow p+n junctions have been formed. The samples implanted under the conditions of 100 keV/5×1015 cm-2 showed a leakage of 7 nA/cm2 and a junction depth of about 0.05 µ m after 500° C annealing, and the current leakages further decreased to a value at about 2 nA/cm2 when the annealing temperature was raised to 550° C. Various conditions of implant and annealing were examined to determine and characterize their effects on the resultant junctions.
Improvement in the Crystalline Quality of ZnSe(111) Films Grown by Molecular Beam Epitaxy Using Misoriented GaAs(111)A Substrates
Authors: Matsumura Nobuo , Maemura Koichiro , Mori Tatsushi , Junji Saraie Junji Saraie
Published: October 2002

The crystalline quality of ZnSe(111) epilayers grown by molecular beam epitaxy can be improved using misoriented GaAs(111)A substrates. The epilayers grown on just-oriented GaAs(111)A substrates showed twinning, hazy surface morphology and weak photoluminescence spectra where deep-level emission dominates. Twin-free ZnSe(111) epilayers with mirrorlike surface morphologies and strong exciton emission were obtained on the GaAs(111)A substrates 10°-misoriented toward [100] direction.
Giant Magnetoresistance Effect in Amorphous CoFeB Sandwiches
Authors: Jimbo Mutsuko , Komiyama Kazuya , Matue Hidekazu , Tsunashima Shigeru , Uchiyama Susumu
Published: October 2002

The giant magnetoresistance effect has been investigated for amorphous-CoFeB/Cu/Co sandwiches with and without exchange-bias layers. A maximum magnetoresistance ratio of 5.4% was obtained in the CoFeB/Cu/Co sandwich at room temperature, where most of the MR change occurred within a magnetic field change of 280 A/m (3.5 Oe). The sandwich with NiO exchange-bias layer showed spin valve behavior with a MR ratio of 2.5%.
Preparation of New Superconducting Cuprate (Ru, Nb)Sr2(Sm, Ce)2Cu2Oz
Authors: Akira Ono Akira Ono
Published: October 2002

Ruthenium-containing 1222 superconductors, Ru

x

Nb1-
x

Sr2Sm1.2Ce0.8Cu2O

z

(x≤1.0), have been prepared and characterized. Almost monophasic samples are obtained for x=0, 0.5, 0.76 and 1.0. Samples annealed at 0.4 MPa of oxygen exhibit superconductivity below 25-32 K except for the x=1 sample which contains a ferromagnetic secondary phase.
Azimuthal Anchoring Energy in Photoinduced Anisotropic Films
Authors: Vorflusev Valery P. , Kitzerow Heinz-S. , Chigrinov Vladimir G.
Published: October 2002

Most electrooptic effects in liquid crystals require a uniform orientation of the director at the glass substrates. A new method to produce suitable alignment layers is based on the creation of anisotropic polymer films by photopolymerization with linearly polarized light. In the present paper we report on measurements of the anchoring strength of these photo-induced anisotropic films. Using a wedge-cell technique, we find an azimuthal anchoring energy ofWϕ≈2.3·10-6J/m2.
Heteroepitaxial Growth of SrBi4Ti4O15/Bi2Sr2CuO6+y Structure by ArF Excimer Laser Ablation
Authors: Tachiki Minoru , Matsutani Masahiro , Fujii Tatsuhiko , Sakaguchi Yoshiyuki , Takeshi Kobayashi Takeshi Kobayashi
Published: October 2002

Heteroepitaxial SrBi4Ti4O15/Bi2Sr2CuO6+
y

thin films were grown on (100)MgO substrates by the excimer laser ablation method. X-ray, reflection high-energy electron and low-energy electron diffraction (XRD, RHEED and LEED) revealed the epitaxial ordering of deposited film crystal oriented normal to the substrate surface, though the streak patterns were slightly dim. The permittivity of SrBi4Ti4O15 film was obtained as 120 ε
0 from C-V measurement for Al/SrBi4Ti4O15/Bi2Sr2CuO6+
y

parallel plate capacitor.
Surface Cleaning of Si-Doped/Undoped GaAs Substrates
Authors: Goto Shigeo , Yamada Masamichi , Yasuhiko Nomura Yasuhiko Nomura
Published: October 2002

It was found that the surface morphology and residual impurities after substrate-cleaning processes are influenced by the existence of a Si dopant in a GaAs (001) substrate. Atomic-force microscopy observations have revealed that the surface of an undoped substrate after conventional thermal cleaning under an As4 flux is smoother than that of a Si-doped substrate. The surface roughness of Si-doped substrates was greatly improved by cleaning using hydrogen radicals ( H•). Furthermore, secondary ion mass spectrometry revealed that the concentrations of residual carbon and oxygen on a H•-cleaned surface were also markedly reduced on undoped substrates, compared to those on Si-doped substrates.
Reconstructed Si(111) Surface Obtained by Electron Beam Heating Using a Conventional Transmission Electron Microscope
Authors: Masato Tomita Masato Tomita
Published: October 2002

Si particles are recrystallized by intense electron irradiation using a conventional transmission electron microscope without an ultrahigh vacuum (UHV) chamber. In spite of the unclean environment, some parts of the nucleated Si islands are much cleaner than those prepared by conventional methods such as ion milling. Under intense electron illumination, a superstructure of the surface is observed in [110] profile images of the Si(111) surface. Because the periodicity of the superstructure is 7×1/3(224) and the structure is localized at the topmost atomic layers, the reconstruction is thought to be Si(111) 7×7 or the absorbed structure.
Organic Luminescent Devices with a Multiplex Cavity Structure
Authors: Nakayama Takahiro , Kakuta Atsushi
Published: October 2002

Organic thin-film devices with multiple cavities vertical to the substrate surface were fabricated. The photo- and electroluminescences of these samples were examined, and the characteristics arising from these multiplex cavities were obtained. This multiplex cavity structure will make it possible to fabricate new functional devices such as optical switches.
Initial Growth of GaAs on Vicinal Si(111) Substrates by Molecular-Beam Epitaxy
Authors: Yodo Tokuo
Published: October 2002

GaAs grown on vicinal Si(111) substrates by molecular-beam epitaxy showed a phenomenon peculiar to a (111) interface due to bond-matching during the initial growth stage (layer thickness (t), t≤200 nm), accompanying the growth of GaAs islands with perfect-crystalline quality. The best full-width at half-maximum of (111) GaAs X-ray diffraction in GaAs layers on vicinal Si(111) tilted by 6° toward the [01̄1] direction was 100 arc.s. at a layer thickness of 200 nm.
N-Channel Metal-Oxide-Semiconductor Device with the Step-Functional I-V Curves Caused by the Punch-Through between Drain and Inversion Layer of the Gate
Authors: Shinji Karasawa Shinji Karasawa , Kazuhiko Yamanouchi Kazuhiko Yamanouchi , Junichi Omori Junichi Omori
Published: October 2002

The stair-shaped I-V characteristics are obtained by inserting a stair-shaped gap between the gate and drain in a metal-oxide-semiconductor field-effect transistor (MOSFET). The turn-on voltage depends on the amount of impurity ions along the path of punch-through. I-V characteristics of the polysilicon gate n-channel enhancement-type MOS device are complementary to those of the Al-gate p-channel MOS device with a similar structure. The stable step-functional I-V characteristics are measured under a negative bias voltage applied to the substrate of boron-doped p-Si.
Magnetic Properties of Granular Superconductors Rb3C60
Authors: Soji Otabe Nobuyoshi Sakamoto , Teruo Matsushita Teruo Matsushita , Michael Baenitz Michael Baenitz , Klaus Lü Klaus Lü
Published: October 2002

Magnetization curves observed in superconducting powders of alkali-metal-doped fullerene Rb3C60showed large hysteresis typical for nonideal type-II superconductors. The slope of initial magnetization was less than 3/2 and tended to decrease with increasing temperature. The theoretical magnetization of a small superconductor given by London agrees well with the observed data when adopting (1-T/Tc)-1/2as the temperatureTdependence of the penetration depth, whereTcis critical temperature. The minor magnetization also differed considerably from the prediction of the critical state model. The reversible phenomena are considered to be marked in the powders. The slope of the minor magnetization loop calculated using the Campbell model fitted well with the observed curves. The estimated interaction distance and the ac penetration depth are in good agreement with those estimated from the 3rd-harmonic susceptibility measurement.
Controlled Spot Size Laser Diode with Flared Stripe and Twin Stripe Modulator at Flare Base
Authors: Nakatsuka Shin'ichi , Maruo Seiji , Arimoto Akira , Saitoh Susumu
Published: October 2002

A controlled spot-size laser diode, which can vary its near-field beam size by means of an electric signal, is demonstrated for use in high-quality laser printers. The laser has a flared stripe near the front facet and a twin injection stripe modulator at the base of the flare. The ratio of the maximum and minimum near-field spot sizes is 1:2.1 when the total operating current is 140 mA.
Niobium Oxide Electrochromic Thin Films Prepared by Reactive DC Magnetron Sputtering
Authors: Yoshimura Kazuki , Miki Takeshi , Iwama Saburo , Sakae Tanemura Sakae Tanemura
Published: October 2002

Niobium oxide electrochromic thin films were prepared by reactive DC magnetron sputtering method. Electrochromic properties of prepared films strongly depended on the substrate temperature during sputtering. The sample with a substrate temperature of 500° C was well crystallized and showed excellent electrochromism. Its integrated luminous transmittance could be controlled from 26% to 89%. Optical modulation range was small for samples with low substrate temperature and these samples showed fast degradation.
New High-Phase-Velocity Leaky Surface Acoustic Wave Mode on LiTaO3 and LiNbO3
Authors: Kobayashi Yasumi , Hirao Yasuhiro , Takeuchi Kousuke , Usuki Tatsuro , Shibata Kenichi , Shimizu Yasutaka
Published: October 2002

A new high-phase-velocity leaky surface acoustic wave (SAW) mode, which was predicted by computer simulation, was confirmed experimentally to exist on both LiTaO3 and LiNbO3. The Euler angles of the propagation direction are (90°, 90°, 31°) on LiTaO3 and (90°, 90°, 37°) on LiNbO3. One-port SAW resonators were produced to confirm these modes. The phase velocity of the mode on LiTaO3 (90°, 90°, 31°) is 6250 m/s, and that on LiNbO3 (90°, 90°, 37°) is 7170 m/s. The temperature coefficient of the resonance frequency on LiTaO3 (90°, 90°, 31°) is -30 ppm/°C, and that on LiNbO3 (90°, 90°, 37°) is -30 ppm/°C.
Novel Method of Obtaining Pretilt Angle in Liquid Crystal Alignment with Polyimide Langmuir-Blodgett Films
Authors: Vithana Hemasiri , Johnson David , Chen Jianmin , Albarici Aparecido , Lando Jerome
Published: October 2002

A new surface modification technique to obtain pretilt angle in Liquid Crystal alignment with polyimide (PI) Langmuir-Blodgett (LB) films is proposed. We modified the surface prior to the LB film deposition by depositing a thin layer of Silicon Monoxide ( SiO

x

) by oblique evaporation. Liquid Crystal Display cells prepared by this method gave no tilt disclinations upon an application of an electric field and were very stable with time. Preliminary results show that two PI-LB films are enough to align liquid crystal molecules with pretilt angles up to 9.1° along the dipping direction. It was found that the dipping direction of the LB films is very important in obtaining the observed pretilt angles.
Interface State Generation in p-Type Si Metal/Oxide/Semiconductor Capacitors due to Fowler-Nordheim Tunneling Current Stress
Authors: Masao Inoue Masao Inoue , Junji Shirafuji Junji Shirafuji
Published: October 2002

The interface state generation in (100) p-type Si metal/oxide/semiconductor capacitors due to Fowler-Nordheim tunneling current stress has been studied by means of multifrequency ac conductance measurements at room temperature. The results show that two kinds of interface states in the upper and lower halves of the gap are generated at different introduction rates. It is found that the capture cross sections of the two interface states change in an opposite way with increasing interface state density. The degradation mechanism of Si MOS capacitors is discussed in relation to the defect creation and the peculiar behavior of the capture cross section. In particular the capture cross section of the interface states in the upper half of the gap decreases rapidly as the density of the interface states is increased.
Hydrogen-Enhanced Diffusion of Plasma-Doped Phosphorus in Silicon
Authors: Kakinuma Hiroaki , Mikio Mohri Mikio Mohri
Published: October 2002

In order to investigate the role of hydrogen in the anomalous phosphorus diffusion in non-mass-separation-type plasma doping, we have studied the effects of prehydrogenation on the phosphorus diffusion in crystalline silicon. Secondary-ion mass spectrometry measurements show that prehydrogenated samples with an rf bias of -200 V have a much deeper penetration depth of phosphorus than samples without prehydrogenation after a PH3 plasma treatment, indicating that diffusion of phosphorus is enhanced by the prehydrogenation. Fourier-transformation infrared spectroscopy reveals that the Si-H bonds increase after the PH3 plasma treatment. Based on these results, the mechanism of the enhanced diffusion is discussed in terms of negatively charged monohydrogen and metastable dihydrides.
Superbright Green InGaN Single-Quantum-Well-Structure Light-Emitting Diodes
Authors: Nakamura Shuji , Senoh Masayuki , Iwasa Naruhito , Nagahama Shin-ichi , Yamada Takao , Mukai Takashi
Published: October 2002

Superbright green InGaN single quantum well (SQW) structure light-emitting diodes (LEDs) with a luminous intensity of 12 cd were fabricated. The luminous intensity of these green InGaN SQW LEDs (12 cd) was about 100 times higher than that of conventional green GaP LEDs (0.1 cd). The output power, the external quantum efficiency, the peak wavelength and the full width at half-maximum of green SQW LEDs were 3 mW, 6.3%, 520 nm and 30 nm, respectively, at a forward current of 20 mA.
The p-AlGaN/InGaN/n-GaN structure of green InGaN SQW LEDs were grown by metalorganic chemical vapor deposition on sapphire subsutrates.
Stress-Induced Raman Frequency Shift in CuInSe2 Thin Films Prepared by Laser Ablation
Authors: Taguchi Isao , Ezumi Hiromichi , Keitoku Susumu , Tamaru Takeyoshi , Osono Hiroto
Published: October 2002

Thin films of CuInSe2 have been prepared by laser ablation using a Nd:YAG laser at substrate temperatures up to 450° C. Raman scattering experiments have shown that the frequency of the A
1 phonon mode for these films shifts markedly to higher frequencies similarly with CuInSe2 single crystals under compression. The existence of compressive stress in the films has been confirmed by observing the bending of a cover glass used as substrate. The magnitude and temperature dependence of the stress estimated from the frequency shifts agree with those determined from the degree of bending.
Growth of SrTiOx Buffer Layers and Their Effect on Surface Flatness of YBa2Cu3O7-δ Films on SrTiO3 (110) Substrates
Authors: Diao Chien Chen , Gin-ichiro Oya Gin-ichiro Oya
Published: October 2002

SrTiO

x

(110) homoepitaxial films as buffer layers grown on SrTiO3 (110) substrates are investigated as regards their effect on the surface flatness of high-T
c YBa2Cu3O7-δ (YBCO) epitaxial films grown on them. It is observed that SrTiO

x

films thinner than 30 nm grow laterally so as to decrease the surface roughness of the SrTiO3 substrates, while thicker SrTiO

x

films grow three-dimensionally with conical islands so as to increase their surface roughness. From the former effect, all-epitaxial YBCO/SrTiO

x

/YBCO/SrTiO

x

łSrTiO3 (sub.) tetralayers with the maximum surface roughness (R
max) less than 6 nm in a large area are successfully grown.
Proposal of Monochromatic Electron Beam Source Using Resonant Tunneling Effect
Authors: Ohshima Takashi , Okamoto Masakuni , Katsuhiro Kuroda Katsuhiro Kuroda
Published: October 2002

We propose a new type of monochromatic electron beam source that incorporates the resonant tunneling effect for ultrahigh-resolution electron microscopes. One set of barrier and quantum well layers on a very sharp GaAs tip surface and a triangular vacuum level barrier created by applying a negative voltage to the sharp tip form a double-barrier structure which enables the resonant tunneling effect to occur. Computer simulations indicated large peaks of electron transmittance through the vacuum/GaAs/AlAs/GaAs double-barrier system. A monochromatic electron beam of about 30 meV in full width at half-maximum is expected at room temperature.
Collisional Energy Exchange of Electrons in the Plug Cell of a Tandem Mirror
Authors: Hitoshi Hojo Hitoshi Hojo
Published: October 2002

Collisional energy exchange between electrons having a plateau-shaped distribution with loss cone and a Maxwellian plasma component in the plug cell of a tandem mirror is studied. The expression for the energy exchange rate is obtained analytically and is compared with that for two Maxwellian plasma components. The energy exchange rate is also calculated for different shapes of the loss cone boundary.
Heavily B-Doped Epitaxial Si Films Grown by Photochemical Vapor Deposition at Very Low Temperature ( <200° C)
Authors: Oshima Takayuki , Abe Katsuya , Yamada Akira , Konagai Makoto
Published: October 2002

Heavily B-doped epitaxial Si films were grown by photochemical vapor deposition (photo-CVD) using a gas mixture of SiH4, H2, SiH2Cl2 and B2H6 in the substrate temperature range of 160-210° C. The electrical and optical properties of the obtained films were evaluated. The most striking result was that B atoms in the as-grown films were almost 100% neutralized even though the hole concentration was increased to 1.3×1020 cm-3 by annealing. It was found that the hole concentration increased as a stretched-exponential function of the annealing time, and an infrared absorption band at 2210 cm-1, which is regarded as a B-related band, appeared as the B-doping quantity was increased. The neutralization of B is considered to be related to H atoms in the films.
Acoustic Emission in Laser Surface Cleaning for Real-Time Monitoring
Authors: Yong-Feng Lu Yong-Feng Lu , Yoshinobu Aoyagi Yoshinobu Aoyagi
Published: October 2002

Real-time monitoring of surface cleanness in laser dry cleaning has been achieved by monitoring the acoustic waves emitted from the substrate surface under pulsed laser irradiation. It is found that the acoustic wave emitted from the surface under laser irradiation can reflect the surface condition, i.e., the surface cleanness. Removal of surface contaminants can result in a weakened laser-induced acoustic wave. The surface cleanness, therefore, can be monitored in real time by detecting the amplitude and frequency of the acoustic wave during the laser cleaning process. This phenomenon provides the laser cleaning system with real-time feedback during the cleaning process.
Simulation of Secondary Electron Emission from Solid Surface Irradiated by Plasmas in an Oblique Magnetic Field
Authors: Ohya Kaoru , Kawata Kazuyuki Hiroi
Published: October 2002

A Monte Carlo simulation model which calculates secondary electron emission from a beryllium surface is combined with an electron transport model in a sheath which is found at the interface between the surface and an edge plasma in magnetic confinement fusion devices. In the model, (1) secondary electron emission from the surface due to bombardment of Maxwellian plasma electrons decelerated by the sheath potential, (2) gyromotion of emitted secondary electrons in the sheath subjected to an oblique magnetic field and (3) their acceleration of the sheath electric field normal to the surface, are involved. Some of the secondary electrons return to the surface within their first gyration, resulting in a considerably low effective secondary electron yield.
Dynamics of Rapid Responsive Polymer Gel Films with the Solvent Effect
Authors: Miura Toshiaki , Eiichi Ono Eiichi Ono , Hisao Ichijo Hisao Ichijo
Published: October 2002

We report the dynamics of the rapid responsive chemomechanical gel device caused by changes in the properties of the solvent. The swelling processes are well described by the Tanaka-Fillmore (TF) theory. However, we found that there are distinct discrepancies in the relaxation times between the swelling and shrinking processes to the same final state, even though this gel has no surface skin layer in the shrinking process. The shrinking process reflects detailed features of the diffusion process which are hidden during the swelling process. We also consider the conditions under which the TF theory is valid in the shrinking process.
Effect of Oxidation due to Ultraviolet-Light Irradiation on Diamond Thin Films Synthesized by Hot-Filament Chemical Vapor Deposition
Authors: Ishikawa Yutaka , Hirose Hideto Yoshimi
Published: October 2002

The effect of oxidation due to ultraviolet (UV) irradiation in air on diamond thin film synthesized by hot-filament chemical vapor deposition (CVD) has been investigated. A low-pressure mercury lamp is used as the UV light source. With UV irradiation, removal of graphite contained in the film begins at a temperature of 350° C due to the oxidation. This temperature is 250° C lower than that reported to yield the same effect without UV irradiation. UV irradiation enables the selective removal of graphite while maintaining the idiomorphic structure of diamond. It is clarified that direct UV irradiation on the film is critical in this process.
The Strain Energy Densities of Hexagonal and Tetragonal Epitaxial Media
Authors: David J. Bottomley David J. Bottomley , Paul Fons Paul Fons
Published: October 2002

Motivated by the burgeoning interest in the epitaxial growth of hexagonal and tetragonal semiconductors, we report expressions for the strain energy density for the high symmetry directions in these crystal systems. In addition, we have calculated the behaviour of the strain energy density as a function of epilayer surface normal orientation for the following systems: GaN on 6H-SiC, GaN on AlN, AlN on 6H-SiC and CuInSe2on GaAs. For the first three cases, we suggest that substrate orientations not yet investigated may improve film quality as they will serve to reduce the strain energy density by approximately 30%, 17% and 65%, respectively, relative to the commonly employed (001) substrate orientation.
Picosecond Time-Resolved Spectroscopy of the Photoluminescence Intensity and Its Dynamical Linear Polarization of Porous Si by 2.86 eV Pulse Excitation
Authors: Norio Akiyama Norio Akiyama , Katsuhiro Ishii Katsuhiro Ishii , Makoto Ohkura Makoto Ohkura , Tokuo Kure Tokuo Kure , Hiroshi Ohkura Hiroshi Ohkura
Published: October 2002

The time-delayed and time-resolved photoluminescence (PL) intensity, and its degree of linear polarizationPof porous Si (PS) reflecting a quantum structure have been studied at room temperature by picosecond spectroscopy with an excitation photon energy of 2.86 eV. Qualitative analysis has been done by assuming that the time-delayed PL spectra are decomposed into at least four Gaussian bands which have time-independentPvalues related to a quantum microstructure. The PL decay curve is presented as a sum of stretched exponential functions for each composite band. With this information, thePdecay curves can be reproduced. We propose that the large depolarization ofPand wide PL bandwidths observed are caused by electron-phonon interaction in surface defects correlated to oxidized PS.
New Surface-Imaging Process for Electron Beam Lithography Using Highly Oriented Polydimethylsilane Film
Authors: Takeuchi Ken-ichiro , Shoji Furukawa Shoji Furukawa
Published: October 2002

The possibilities of highly oriented polydimethylsilane film for use in electron beam lithography are shown in the present work. By electron beam irradiation onto the film, submicron patterns are obtained after the etching process. The effects of electron beam irradiation on the chemical bonds in the film are also studied using Fourier transform infrared absorption spectroscopy. The oriented character and the high density of the film are advantageous to the resolution, and the irradiated area shows excellent resistance to acid through the formation of the C-O-C, Si-O-C, and/or Si-O-Si bonds.
Laser Silicon Ablation Studied by Time-of-Flight Mass Spectrometry: Generation of Si Ions and Neutrals and Their Translational Properties
Authors: Quan Zhuang Quan Zhuang , Kazutaka Ishigoh Kazutaka Ishigoh , Katsumi Tanaka Katsumi Tanaka , Katsuyasu Kawano Katsuyasu Kawano , Ryohei Nakata Ryohei Nakata
Published: October 2002

Laser pulses of Nd:YAG (532 and 266 nm) were irradiated on a Si target to investigate the ablation process. Monoatomic ions and neutrals were simultaneously ablated, with ions having higher most probable kinetic energy (MPKE) and broader velocity distribution than neutrals. The two beams showed close ablation fluence threshold, but different exponential relationships of the intensity of the ablated species vs laser fluence, with the 266 nm beam having a higher increasing rate than that of the 532 nm beam. The 266 nm beam also resulted in higher kinetic energy and a higher fraction of ions in the ejected particle stream. The time-of-flight (TOF) results fitted the shifted Maxwell-Boltzmann distribution well. The laser Si ablation mechanism was discussed.
Effect of Plasma Current on Magnetohydrodynamic Modes in Neutral Beam Heated Plasmas in Compact Helical System
Authors: Sakakibara Satoru , Yamada Hiroshi , Toi Kazuo , Ejiri Akira , Ando Akira , Iguchi Harukazu , Matsuoka Keisuke , Morita Shigeru , Motojima Osamu , Nishimura Kiyohiko , Okamura Shoichi , Tanaka Kenji
Published: October 2002

Effects of the net toroidal plasma currents on magnetohydrodynamic (MHD) modes have been investigated in neutral beam heated plasmas with the control of ohmic current. The characteristics of experimental observations are discussed in comparison with the calculated 3-D equilibria. The resonant modes are destabilized by the change of magnetic configuration due to the induced current in the co-direction. The modes withm/n=2/1 and 3/2 abruptly disappear at the specific current, which is consistent with the disappearance of the resonant surfaces. The behavior of these modes is phenomenologically consistent with that of the interchange mode.
Improving the Quality of GaAs Films by Electron Beam Irradiation during Molecular Beam Epitaxial Growth at Low Temperature
Authors: Tamura Susumu , Kinoshita Koushi , Yokota Katsuhiro , Kazumi Yamashita Kazumi Yamashita
Published: October 2002

Thin GaAs films were grown on (001) GaAs substrates at temperatures ranging from 300° C to 400° C using Ga and As molecular beams under electron beam irradiation. These films were compared with GaAs films grown at the same temperatures by conventional molecular beam epitaxy (MBE). Electron beam irradiation improved the reflection high-energy electron diffraction (RHEED) patterns and increased the photoluminescence intensities of the GaAs films. These improvements were not a result of raised growth temperatures caused by electron beam irradiation.
New Gray Level Control Technique and Its Characterization for Antiferroelectric Liquid Crystal Cells
Authors: Okada Hiroyuki , Watanabe Manabu , Onnagawa Hiroyoshi , Miyashita Kazuo
Published: October 2002

A new gray-level control technique for antiferroelectric liquid crystal cells under phase transition from the field-induced ferroelectric state to antiferroelectric state has been investigated. A continuous gray level is realized by optimizing the holding voltage and is closely related to the value of the interval pulse voltage divided by the interval pulse width. Negative interval pulse voltage with short interval pulse width is effective to shorten the response time from the field-induced ferroelectric state to gray-level state. From stroboscopic micrographs, a multidomain comprising ferroelectric and antiferroelectric domains is found to be stabilized due to the pinning effect of focal-conic fan texture along the smectic layer direction.
Hydrogen-Initiated Nucleation and Growth of Hydrogenated Amorphous Silicon on Graphite
Authors: Kazuyuki Ikuta Kazuyuki Ikuta , Yasutake Toyoshima Yasutake Toyoshima , Satoshi Yamasaki Satoshi Yamasaki , Akihisa Matsuda Akihisa Matsuda , Kazunobu Tanaka Kazunobu Tanaka
Published: October 2002

Initial nucleation and formation processes of a-Si:H clusters on single-crystal graphite have been studied by ultrahigh-vacuum scanning tunneling microscopy and Raman scattering spectroscopy. It is critically demonstrated that hydrogen radicals coming from the SiH4 plasma create structural defects on the surface of the single-crystal graphite which act as absorption sites for SiH3 radicals diffusing on the surface. On the basis of this picture, spatially-inhomogeneous formation of a-Si:H clusters prior to full coverage of the surface is also discussed.
CdS Thin Film Deposited in Iodide-Containing Chemical Bath
Authors: Yoshio Hashimoto Yoshio Hashimoto , Takuya Nakanishi Takuya Nakanishi , Takayoshi Andoh Takayoshi Andoh , Kentaro Ito Kentaro Ito
Published: October 2002

CdS thin films grown from an aqueous solution of iodides were studied using electron probe microanalysis (EPMA) and X-ray photoemission spectroscopy (XPS). It has been revealed that the films contain 3% iodine whereas those grown from chlorides contain less than 1% chlorine. Both films are Cd-rich and also have impurity phases of CdOx and/or Cd(OH)x. XPS depth profile showed a uniform distribution of these impurities in the films. The presence of iodine in the former CdS film, which is suitable for CdS/CuInS2 solar cell application, suggests a potential role of iodine in the improvement of the solar cell performance.
Numerical Analysis of Influence of Surface Barrier on Current-Voltage Characteristics for Narrow Superconducting Lines
Authors: Hiroya Andoh Hiroya Andoh , Masanobu Kusunoki Masanobu Kusunoki , Akira Fujimaki Akira Fujimaki , Hisao Hayakawa Hisao Hayakawa
Published: October 2002

The variation of critical current density with reduced line width and the temperature dependence of voltage for superconducting narrow lines are calculated theoretically. Critical currents of superconducting narrow lines increase progressively as the lines become narrower. The surface barriers for superconducting narrow lines are discussed in order to understand the progressive increase in critical currents of superconducting narrow lines. Furthermore, the thermally activated flux lines jumping over the surface barrier are discussed in order to understand the temperature dependence of voltage for superconducting narrow lines. The results of calculation using the surface barriers agree well with experimental results.
Effect of Alumina on Crystallization of Low-Dielectric Lead Borosilicate Glass
Authors: Jean Jau-Ho , Lin S.-C. , Yang S.-L.
Published: October 2002

Formation of cristobalite in lead borosilicate glass at 700° C is completely prevented by addition of 5-10 vol% alumina. Thermal expansion results show that, in contrast to the sample without a sufficient amount of alumina, the thermal expansion coefficient of the cristobalite-free sample remains relatively unchanged with sintering time at the temperature investigated, and is close to those theoretically calculated.
Copper Oxide-Loaded Tin Dioxide Thin Film for Detection of Dilute Hydrogen Sulfide
Authors: Yoo Do Joon , Tamaki Jun , Park Soon Ja , Miura Norio , Noboru Yamazoe Noboru Yamazoe
Published: October 2002

The H2S sensing characteristics of SnO2 thin films loaded with CuO were found to be much improved by reducing the film thickness. A 40-nm-thick film showed sensitivity as high as 20000 and 2000 to 1.5 and 0.3 ppm H
2
S in air, respectively, at 200° C, while the rate of response to 0.3 ppm H
2
S was rather slow.
Neutral Stream Extraction from Electron Cyclotron Resonance Plasma by Using Parallel Magnetic Field
Authors: Yoshito Jin Yoshito Jin , Tai Tsuchizawa Tai Tsuchizawa , Seitaro Matsuo Seitaro Matsuo
Published: October 2002

A low-energy neutral stream is generated by charge exchange reactions between the accelerated ions in an electron cyclotron resonance plasma stream and the background molecules and atoms. This stream is extracted using a parallel magnetic field to eliminate charged particles. Etched Si profiles demonstrate that this neutral stream has high directionality.
Observation of a New CuPt-Type Ordered-Phase with Orientation in the [111]A Direction in Al0.5In0.5P Alloy
Authors: Gomyo Akiko , Sumino Masayoshi , Hino Isao , Tohru Suzuki Tohru Suzuki
Published: October 2002

A new type of CuPt ordered-phase (CuPt-A) with orientation in the [111]A and [1̄1̄1]A directions was found in Al0.5In0.5P grown at 520° C on exact (001)GaAs substrate by gas-source molecular-beam epitaxy. Weak formation of conventional CuPt-B type ordered phase was also observed in the same AlInP layer. The surface reconstruction observed by RHEED during the growth was (2×2). At a growth temperature of 560° C the surface reconstruction was (2×1) and only conventional CuPt-B was formed. A step array parallel to [1̄10] and descending towards [110] was found to promote formation of the CuPt [111]A variant.
More than 103 Times Photoluminescence Intensity Recovery by Silicon Interface-Control-Layer-Based Surface Passivation of Near-Surface Quantum Wells
Authors: Hasegawa Hideki , Kodama Satoshi , Koyanagi Satoshi , Tamotsu Hashizume Tamotsu Hashizume
Published: October 2002

The latest version of the silicon interface control layer (ICL)-based passivation process utilizing a Si/Si3N4 double-layer ICL was applied to passivation of Al0.3Ga0.7As/GaAs/Al0.3Ga0.7As near-surface quantum wells (Q
W
s). Its effectiveness was investigated using normalized PL intensities from passivated and unpassivated Q
W
s. Complete recovery of PL intensity was achieved by the novel passivation with an observed maximum recovery factor of 1.4×103.
Effect of the Polymer Tilt Angle for Generation of Pretilt Angle in Nematic Liquid Crystal on Rubbed Polyimide Surfaces
Authors: Seo Dae-Shik , Araya Kazuo , Yoshida Norihiro , Nishikawa Michinori , Yabe Yoshikazu , Shunsuke Kobayashi Shunsuke Kobayashi
Published: October 2002

We have studied the effect of the polymer tilt angle for pretilt angle generation in nematic liquid crystal, 4-cyano-4′-n-penthylbiphenyl (5CB) on rubbed polyimide surfaces. The polymer tilt angle was determined by measuring induced optical retardation produced in rubbed polyimide (PI) surfaces by rubbing. We suggest that the polymer tilt angle is not related directly to the pretilt angle on rubbed PI surfaces by rubbing. We proposed a microscopic model of pretilt angle generation on rubbed PI surfaces by rubbing. Finally, we conclude that the pretilt angle generation of 5CB strongly depends on the characterization of polymer materials and the micro-asymmetric triangular structure of the polymer on rubbed polyimide surfaces.
Preparation and Properties of CuInS2 Thin Films Produced by the Reactive Sputtering Method
Authors: Kobayashi Satoshi , Yu Dan Yang , Sarinanto Mohammad Mustafa , Kobayashi Yasuyuki , Kaneko Futao , Takahiro Kawakami Takahiro Kawakami
Published: October 2002

Nearly stoichiometric CuInS2 thin films have been prepared on Pyrex slide glass by the reactive sputtering method using CS2 as a reactive gas at a substrate temperature of 150° C by controlling the CS2 partial pressure. Sputtering for 2 hours yields the thickness of 1∼2 µ m. The films are preferentially oriented with the (112) plane parallel to the substrate. The forbidden gap is estimated to be 1.51 eV which is slightly smaller than that of the single crystal. For films with fairly good stoichiometry, the conduction is p-type and the resistivity ranges between 10 and 104 Ω· cm. A fairly large amount of carbon is incorporated during growth.
Observation of Ion Scattering from Metal Surfaces Bombarded with Low-Energy Hydrocarbon Ions
Authors: Mitsuoka Yoshihito , Toyoda Hirotaka , Sugai Hideo
Published: October 2002

A single species of hydrocarbon ion CH
x

+ (x=2, 3, 4) is extracted from an inductive plasma via a mass filter and irradiated onto aluminum surfaces at the incidence angle of 45°. Measurements of ions scattered in the specular direction revealed two types of dissociative ion scattering depending on the incidence energies. One is the dissociation into relatively large molecular ions ( CH3
+, CH2
+) at the low incidence energies (<50 eV). The other is the dissociation into small fragment ions ( H+, C+, CH+) at the high incidence energies (≥150 eV). The former is tentatively interpreted as a result of electronic excitation in resonant neutralization or Auger neutralization processes, while the latter is attributed to rovibrational excitation (via direct momentum transfer) induced by molecular-ion metal-surface collisions.
Extended X-Ray Absorption Fine Structure Study of ZnSSe and ZnMgSSe
Authors: Maruyama Takahiro , Ogawa Takashi , Akimoto Katsuhiro , Kitajima Yoshinori , Ito Satoshi , Ishibashi Akira
Published: October 2002

Distribution of chalcogen atoms in ZnS

x

Se1-
x

(x=0.06) and Zn1-
x

Mg

x

S

y

Se1-
y

(x=0.18, y=0.2) with zincblende structure was investigated by EXAFS (extended X-ray absorption fine structure) spectroscopy. By measuring sulphur K-edge EXAFS, it was found that the ratio of the number of sulphur atoms to that of selenium for the second nearest neighbors around sulphur atoms is proportional to the respective composition ratio both in ZnSSe and in ZnMgSSe. These results indicate that there is no clustering in ZnSSe and that chalcogen atoms are also randomly distributed in ZnMgSSe.
Effect of a Magnetic Field on the Excitonic Luminescence Decay Time in a GaAs-AlxGa1-xAs Quantum Well
Authors: Aksenov Igor , Aoyagi Yoshinobu , Kusano Jun-ichi , Sugano Takuo , Yasuda Takashi , Segawa Yusaburo
Published: October 2002

The effect of a magnetic field on the excitonic radiative lifetime has been studied in a high-quality GaAs-AlGaAs quantum well. A temporal dynamics has been observed within the excitonic emission band, with different spectral components exhibiting different dependencies of the luminescence decay time on magnetic field. An application of a magnetic field has been found to result in a decrease of the radiative lifetime τ rad for delocalized excitons, and, to the contrary, in an increase of τ rad for localized excitons. Three magnetic field induced mechanisms, i.e. shrinking of the exciton lateral dimensions, expanding of its coherence area, as well as 2D⇒ 0D transformation in the electronic density of states, have been put forward to explain the obtained results.
Molecular Orientation of Liquid Crystalline Polymer Films Fabricated by Polarized-Laser Chemical Vapor Deposition
Authors: Itadani Toshiaki , Saito Koichi , Akiya Takeo , Nagata Shiro , Niino Hiroyuki , Yabe Akira
Published: October 2002

Chemical vapor deposition of three kinds of 4-[ω(2-methylpropenoyloxy)alkyloxy]-4′-cyanobiphenyls (alkyloxy; ethyloxy, propyloxy and hexyloxy) was carried out using a polarized KrF excimer laser. The films deposited from the hexyloxy monomer, whose radical polymerization gave a side-chain-type liquid crystalline polymer, showed birefrengence and IR dichroism. The anisotropy of IR absorbance suggests that the direction of side chains of the polymer is parallel to the electric vector of the laser beam. The deposition of two other monomers, which yielded amorphous polymers because of the shortness of side chains, induced no molecular orientation. It was concluded that the molecular orientation took place due to an interaction between the liquid crystalline phase of the deposited polymer film and the polarized laser beam.
Thermal Growth of Thin Oxide in Ge Films and Interfacial Bond Defects of Oxygen
Authors: Sunada Junji , Fukuchi Ken-ichi , Taneda Youji , Hirose Masami
Published: October 2002

Taking account of the high photoabsorption coefficient of Ge for 290 nm light, we investigate the thermal growth of thin oxide in Ge films by utilizing a double-beam UV spectrometer, and discuss the results in connection with photoconduction accompanied by oxidation. Rapid growth in the initial stage of oxidation up to 18 Å thickness follows the kinetics of slow linear rates. Oxidation at temperatures lower than 400° C induces oxygen bond defects with high density at the Ge-GeO2 interface.
A Model for the Formation of Oxidation-Induced Stacking Faults in Czochralski Silicon
Authors: Sadamitsu Shinsuke , Okui Masahiko , Sueoka Koji , Marsden Kieran , Tatsuhiko Shigematsu Tatsuhiko Shigematsu
Published: October 2002

The mechanism of oxidation-induced stacking fault (OSF) formation in Czochralski silicon (CZ-Si) crystals was investigated by transmission electron microscopy observations of the initial stages of OSF growth. OSFs were observed to be always generated at one of the <110> edges of platelet oxygen precipitates. We observed previously that these platelet oxygen precititates had an expansive strain field in the direction parallel to the precipitate plate and a compressive strain field normal to the plate. Silicon self-interstitials having compressive strain are probably attracted to the expansive strain field of the precipitates, and condense to form stacking faults. A new model for OSF generation is presented taking into consideration the strain field around self-interstitials and oxygen precipitates.
TEA-CO2 Laser Oscillation by Inductive Energy Storage Pulsed Power Generator
Authors: Ihara Satoshi , Satoh Saburoh , Ishimine Masashi , Yamabe Chobei , Akiyama Hidenori
Published: October 2002

A pulsed-power technology has been used for production of high power and fast pulses. It is possible that a pulsed-power generator with a storage inductor and an opening switch can be extremely compact and light in comparison with a conventional system. We have carried out the experiments on TEA-CO2 laser oscillation using the inductive energy storage pulsed-power generator. The output energy of the laser and the peak power were 0.3 J and 0.53 MW, respectively.
Evaluation of the Waveguide Effect in Proximity X-Ray Lithography Using an Optical Trace Method
Authors: Ogawa Taro , Murayama Seiichi , Ito Masaaki , Matsuzaka Takashi
Published: October 2002

In proximity X-ray lithography, mask-patterns may be 500 to 1000 times as thick as the X-ray wavelength. This suggests the occurrence of physical phenomena such as interference between wave modes propagating through a mask pattern. Change in intensity profiles of X-rays caused by such interference, referred to as the waveguide effect, is re-evaluated through a new simulation method. This simulation uses a technique based on the optical trace method to superpose rays that can propagate the mask pattern. As a result, the influence of the waveguide effect can be calculated for the mask pattern consisting of not only a perfect conductor but also a real material. The feasibility of this simulation is investigated by comparing the intensity profiles of X-rays with those obtained using a previous simulation method based on Maxwell's equations with a mask pattern assumed to be a perfect conductor. The results suggest that the new simulation is applicable for wide mask pattern sizes ranging from 500 nm (0.5 µ m) to below 100 nm (0.1 µ m). The simulation results also show that the waveguide effect makes intensity profiles of X-rays propagated through a 50-nm-wide mask pattern of tungsten (W) narrower than the pattern width. Furthermore, the energy of X-rays propagated through this mask pattern is found to decrease about 12%. These results indicate that the waveguide effect influences the intensity profiles of X-rays propagated through the mask pattern, even if it consists of real materials.
Fourier Transform Infra Red Observation of the Orientation of Dipolar Urea Bonds in Polyurea during Corona Poling
Authors: Iijima Masayuki , Ukishima Sadayuki , Iida Keiko , Takahashi Yoshikazu , Eiichi Fukada Eiichi Fukada
Published: October 2002

Polyurea thin films were prepared using 4,4-diaminodiphenyl methane (MDA) and 4,4-diphenyl methane diisocyanate (MDI), by vapor deposition polymerization. Polyureas include urea bonds which contain NH and CO dipolar groups. The dipole orientation which was caused by corona poling was observed by Fourier Transform Infra-Red [FT-IR] reflectance. In diode corona poling, the dipoles are aligned best in the area directly below the needle electrode, with the degree of dipole orientation decreasing in proportion to increasing distance from this electrode. In triode corona poling, a grid electrode is set up between the needle electrode and planar electrode, and orientation is accomplished uniformly over the entire surface. Contrary to this assumption, however, we found, through FT-IR mapping analysis, that dipole orientation follows the form of a net mesh structured like a grid electrode.
Patterning-Assisted Control for Ordered Arrangement of Atomic Steps on Si(111) Surfaces
Authors: Ogino Toshio , Hibino Hiroki , Homma Yoshikazu
Published: October 2002

We propose a novel technique for organizing steps on Si surfaces. Arrays of small holes are formed on Si(111) wafers misoriented toward [112̄] by using conventional Si technology. The wafers are then annealed in an ultra-high vacuum at about 1300° C. During the hole filling-in process, steps on the surface are arranged regularly, and finally parallel step bands are ordered after the holes have completely disappeared.