bluuebunny/crossref_metadata_2025 huggingface dataset:
Dielectric Properties and Phase Transitions of Ba(Ti1-xSnx)O3 Solid Solution
Authors: Yasuda Naohiko , Hidehiro Ohwa Hidehiro Ohwa , Shigeto Asano Shigeto Asano
Published: October 2002

In Ba(Ti1-
x

Sn

x

)O3 solid solution, for Sn concentration x≤0.1,
the permittivity follows the Curie-Weiss law above the Curie
point T
c. The increase in the peak value of the permittivity at
T
c is due to the change in ferroelectric transition from first
order to second order with increasing x. For x>0.1, some
deviations from the Curie-Weiss law are observed in a narrow
temperature region above T
c. The diffuse phase transition was
observed. For x>0.2, the Curie-Weiss law does not hold over a
wide temperature range. The dielectric dispersion was observed
in the radio-frequency range (10 kHz–10 MHz). With increasing Sn
concentration, the change in the phase transition from a normal
ferroelectric transition to relaxor through the diffuse phase
transition was observed.
Demonstration of Frequency-Domain Optical Data Storage of CuCl Semiconductor Nanocrystal Systems
Authors: Shinji Okamoto Shinji Okamoto , Yasuaki Masumoto Yasuaki Masumoto
Published: October 2002

Persistent spectral hole-burning phenomena are observed in semiconductor nanocrystals. This means that the nanocrystal systems are applicable to optical data storage devices as well as nonlinear optical devices. We demonstrate the persistence of spectral holes and frequency-domain optical data storage using CuCl semiconductor nanocrystals embedded in glass and in a NaCl host crystal.
Localized Polarization in Strontium Titanate Crystal
Authors: Junichi Karasawa Junichi Karasawa , Hitoshi Takaku Hitoshi Takaku , Tatsuo Fukami Tatsuo Fukami
Published: October 2002

Polarization charges, which are assumed to be located on crystal surfaces and contribute to ultra low frequency dielectric relaxation, were investigated through thermally stimulated current (TSC) studies of perovskite titanates in both single crystal and polycrystalline forms. When the anodic sides of the poled single crystal and ceramics were removed, the TSC peak near 90
o
C for single crystal was entirely eliminated, while that for the ceramics was virtually unchanged. The voltage dependences of the polarized charge were also different for single crystal and ceramics with various thicknesses, providing evidence for the previously proposed `localized dipole model'.
NH4OH-Treated Si(111) Surfaces Studied by Spectroscopic Ellipsometry and Atomic Force Microscopy
Authors: Kobayashi Kazuyuki , Takizawa Sadao Adachi
Published: October 2002

Chemically treated Si(111) surfaces in NH4OH:H2O=1:5 alkaline etchant at 80° C were investigated using spectroscopic ellipsometry (SE) and ex situ atomic force microscopy (AFM). The SE data indicate that when a native oxide layer is partly etch-removed, the resulting surface is very rough. The roughened layer thickness in this case is ∼4 nm with a void fraction of ∼40 %, obtained using an effective medium approximation; the AFM image for this sample indicates a roughened surface of ∼4.5 nm rms. Just after the oxide layer is etched away completely, the SE data yield the spectrum of a nearly flat Si surface. The AFM image confirms a microscopically flat surface (∼0.2 nm rms) with the emergence of relatively large triangular hollows. With further etching, the Si surface becomes microscopically rougher, as revealed by the SE and AFM.
Size Effect on the Phase Transition in PbTiO3 Fine Particles
Authors: Ishikawa Kenji , Nomura Takashi , Nagaya Okada Nagaya Okada , Kazumasa Takada Kazumasa Takada
Published: October 2002

The finite size effect on the phase transition in PbTiO3 fine particles is described. Very small crystals with an average diameter of 14.2 nm were obtained by lowering the calcination temperature to 400° C. Raman scattering measurements of such fine particles were carried out to study the dependence of the phase transition temperature on the particle size. The X-ray diffraction pattern was also measured to study the tetragonality, c/a ratio. The results strongly suggest the presence of a critical size below which the ferroelectric state becomes unstable. The critical size determined by Raman measurements was 10.7 nm.
Practical Simulation of the I–V Curve for Amorphous-Silicon-Based Multijunction Solar Cells after Light Soaking
Authors: Maruyama Eiji , Kuroda Shigeru , Okamoto Shingo , Tarui Hisaki , Makoto Tanaka Makoto Tanaka , Shinya Tsuda Shinya Tsuda
Published: October 2002

A new procedure was developed to simulate the I–V curves of amorphous-silicon-based multijunction solar cells after light soaking. In the proposed method, the I–V curves of multi-junction cells were calculated by adjusting the measured I–V curves of component single-junction cells, considering the effect of illumination-spectral dependence, using a newly developed formula for illumination-intensity dependence. Furthermore, during light soaking of single-junction cells, the light was soaked through proper optical filters which can reproduce almost the same spectrum and intensity of incident light under the multijunction condition. Consequently, the I–V curves estimated by this method agreed very well with measured values for real multijunction cells not only before but also after light soaking. A high stabilized conversion efficiency of 10.6% for an a-Si/a-SiGe 2-stack solar cell has been achieved, for which the efficiency estimated using this method was 10.7%.
Hydrofluoric-Treated GaAs Surfaces Analyzed by Contact Angle Measurement and Auger Electron Spectroscopy
Authors: Koichi Matsushita Koichi Matsushita , Naoki Suzuki Naoki Suzuki , Sumio Okuyama Sumio Okuyama , Yasuji Kumagai Yasuji Kumagai
Published: October 2002

A GaAs surface chemically treated with hydrofluoric (HF) acid was characterized using measurement of the contact angle between the GaAs surface and a water droplet on it and through Auger electron spectroscopy (AES). The surface oxide layer formed on GaAs during planar etching was removed by dipping it into HF solution. As the dipping time increased, a thicker arsenic layer was formed on the GaAs surface, which prevented the surface oxidation of the substrate. This is reflected in an increase in the contact angle. When the dipping time becomes very long (180 min), the amount of surface oxygen increases probably due to the roughened surface of the GaAs substrate, resulting in a decrease in the contact angle.
Evaluation of Densities and Energy Levels of Donors and Acceptors in Compensated Semiconductor from Temperature Dependence of Majority Carrier Concentration
Authors: Hideharu Matsuura Hideharu Matsuura
Published: October 2002

An accurate evaluation of densities and energy levels of donors and acceptors in a compensated semiconductor from the temperature dependence of the majority carrier concentration n(T) is carried out by modifying the graphic method proposed in Jpn. J. Appl. Phys. 35 (1996) L555. The introduced function, S(T,E
ref), is defined as S(T,E
ref) ≡n(T) exp
(E
ref/k
T)/k
T, where k is the Boltzmann constant and E
ref is the newly introduced parameter. From the dependence of S(T,E
ref) on the impurity density of minority carriers, the densities and energy levels of donors and acceptors can be determined accurately.
Effect of Bi2Sr2CaCu2Oy Single Crystal Surfaces on Contact Resistance
Authors: Hiroya Imao Hiroya Imao , Satoru Kishida Satoru Kishida , Heizo Tokutaka Heizo Tokutaka
Published: October 2002

We formed Au electrodes on the surfaces of Bi2Sr2CaCu2Oy single crystals and investigated the effect of the surfaces on the contact resistance between Au electrodes and the single crystals. The lowest contact resistivity was obtained by forming Au electrodes on the air-cleaved surface of the Bi2Sr2CaCu2Oy single crystal, which is nearly equivalent to a clean surface. X-ray photoelectron spectroscopy results indicated that the contact resistances of the specimens were sensitive to the chemical bond natures of the constituent elements on Bi2Sr2CaCu2Oy single crystal surfaces.
Magnetic Properties in Aligned (Tl0.5Pb0.5)Sr2Ca2Cu3O9High-Tc Superconductor
Authors: Kim Young Cheol , Kim Gun Cheol , Park Yong Dae , Kim Jeong Nam , Jeong Dae Yeong , Sohn Myung Hwan
Published: October 2002

The magnetic properties of c-axis-oriented powders of (Tl0.5Pb0.5)Sr2Ca2Cu3O9 have been investigated. With increasing field, the anisotropy of the persistent critical current density J
p decreases and crossover occurs at higher field. The sense of the anisotropy reverses. Therefore, the flux motion is easier for H||
c than for H||
a
b at higher field. The pinning forces show the scaling behavior of h
0.8(1-h)2.0 and are maximum at h=0.29. Near T
c, the slope d
H
c2/d
T of the upper critical field is -2.1 T/K for fields parallel to the c axis.
Organic Electroluminescent Devices Having Derivatives of Aluminum-Hydroxyquinoline Complex as Light Emitting Materials
Authors: Michio Matsumura Michio Matsumura , Tomonori Akai Tomonori Akai
Published: October 2002

Derivatives of aluminum-hydroxyquinoline complex were synthesized and used as light emitting materials for electroluminescent devices. The absorption and photo-luminescence spectra, and also the energy levels of the derivatives were shifted from those of the mother compound by electron-withdrawing and electron-releasing groups introduced into the hydroxyquinoline ligands. Using these compounds, the relationship between the electroluminescence efficiency and the energy levels was analyzed. The results strongly suggest that part of the injected electrons and holes recombine across the interface of the stacked organic layers, the process being non-emissive. It was also observed that the current-voltage curves shift toward the lower voltages as the electron accepting energy level of the light emitting material becomes lower.
A Bipolar Charge Transport Molecule
Authors: Murray B. J. , Kaeding J. E. , W. T. Gruenbaum W. T. Gruenbaum , P. M. Borsenberger P. M. Borsenberger
Published: October 2002

Hole and electron mobilities have been measured in vapor deposited layers of N-(p-(di-p-tolylamino)phenyl)- N′-(1,2-dimethylpropyl)-1,4,5,8-naphthalenetetracarboxylic diimide (TAND). The TAND molecule contains a naphthalene diimide acceptor functionality and a triarylamine donor functionality. The mobilities are of comparable magnitude and show similar field and temperature dependencies. The results are described within the framework of a formalism based on disorder. The formalism is premised on the assumption that charge transport occurs by hopping through a manifold of localized states with superimposed energetic disorder. The key parameter of the formalism is the energy width of the hopping site manifold. For TAND, the widths are 0.110 and 0.091 eV for hole and electron transport, respectively. The result leads to the conclusion that the hole and electron transport manifolds are independent and not influenced by the transport states of the oppositely charged carriers.
Transport Properties of La 1-xSrxMnOz Thin Films in Oxygen Deficient and Excess States
Authors: Naohisa Sengoku Naohisa Sengoku , Keiichi Ogawa Keiichi Ogawa
Published: October 2002

Thin films of La1-x
SrxMnOz (x=0.15 and 0.175) have been successfully fabricated by pulsed laser deposition. Resistivity and magnetoresistance of the films have been measured. With increasing post-annealing time or oxidizing gas pressure, the resistivity initially decreases and then increases. The latter increase has been observed for the first time in the present study. The observed initial reduction is attributed to the decrease in the oxygen deficiency of the as-grown film and the latter increase is attributed to the increase in cation vacancies. Semiconducting behavior of the sufficiently oxidized film is attributed to the localization of carriers due to the random potential produced by the cation vacancies. The resistivity enhancement in the oxygen excess state is found to increase the magnetoresistance ratio considerably.
Evaluation of C15TCNQ Langmuir-Blodgett Ultrathin Films on Aluminum Thin Films by Attenuated Total Reflection Measurements
Authors: Kato Keizo , Aoki Yusuke , Ohashi Kenichi , Kaneko Kazunari Shinbo
Published: October 2002

The attenuated total reflection (ATR) properties of C15TCNQ Langmuir-Blodgett (LB) ultrathin films deposited on the Al thin films about 20 nm thick were measured in order to evaluate the actual structure. The C15TCNQ LB ultrathin films were prepared by the vertical dipping method, using two deposition processes. The dielectric constants and the thicknesses of these deposited LB films were theoretically calculated from the ATR curves, taking into account the presence of the natural oxide layer on Al. It was considered that Z-type LB films were obtained when the deposition of each monolayer was carried out only as the substrates were withdrawn. In contrast, when monolayers were deposited during both upward and downward movements of the substrates, the resulting LB films were considered to be not perfect Y-type, but partially Z-type.
Influences of Ambient Gases on the Emission Characteristics of Nickel-Deposited Field Emitters for Vacuum Microelectronics
Authors: Masayoshi Nagao Masayoshi Nagao , Motoki Matsubara Motoki Matsubara , Kazunori Inoue Kazunori Inoue , Yasuhito Gotoh Yasuhito Gotoh , Hiroshi Tsuji Hiroshi Tsuji , Junzo Ishikawa Junzo Ishikawa
Published: October 2002

Influences of gases on the field emission characteristics of Ni-deposited field emitters were studied by introducing O2, Ar and N2 gases into a vacuum chamber. The extraction voltage depended both on the gas pressure and on the gas species. The observed noise, flicker noise and step-spike noise, was different among the gas species. For quantitative evaluations, noise power was calculated for flicker noise and the numbers of step-spike noise occurrences were counted. These quantitative evaluations allowed understanding of the origins of flicker noise depending on the emission current. By analyzing surface states of emitter apices using the slope and intercept of the Fowler-Nordheim plot (Seppen-Katamuki (S-K) chart), influences of the gases on the emitter were clarified.
Electrooptical Properties of the Si δ-doped GaAs/AlGaAs Triple-Barrier Resonant Tunneling Structure
Authors: Lu Chien-Rong , Szu-Ku Du Szu-Ku Du , Jia Lian Chang Jia Lian Chang
Published: October 2002

The electrooptical properties of a Si δ-doped GaAs/Al0.3Ga0.7As triple-barrier resonant tunneling (TRT) nanostructure have been studied by photoreflectance spectroscopy from 20 K to room temperature. The TRT structure forms two coupled quantum wells. The first and the second electronic subbands in the wide well are partially filled, and the corresponding optical transitions are suppressed. The strongest spectral feature is due to the enhancement of the subband resonance between the two coupled wells. The ionized δ–doping centers in the Al0.3Ga0.7As side barriers can induce internal electric fields, and cause oscillatory spectral features when the photon energy is larger than the gap of Al0.3Ga0.7As. Analyzing the oscillatory part of the spectrum gives an internal electric field of 32 kV/cm, and an estimation of the electron subband energy in the ionized δ-doping center induced potential wells.
Low Temperature Deposition of Gate Silicon Dioxide Film for Thin Film Transistors by Photoassisted Remote Plasma Chemical Vapor Deposition Method
Authors: Suzuki Hitoshi Shindo
Published: October 2002

High quality silicon dioxide films with low leakage current and low surface charge density were deposited by a photoassisted remote plasma chemical vapor deposition (PAP-CVD) method at 330° C. Oxygen gas excited in a plasma which is kept apart from the wafer, was transported to the wafer and reacted with monosilane gas to generate intermediates. The adsorbed intermediates on the wafer were photoexcited to produce silicon dioxide films. Since the energy and the flux of incident ions to the wafer are suppressed to be as low as 1.4 eV and 1.3×1013 cm-2 s-1, respectively, high-quality films with low leakage current and low surface charge density were successfully deposited at low temperature. The silicon dioxide film fabricated by the PAP-CVD method is suitable for use as the gate insulator of a thin film transistor (TFT).
General Expression for Current Transformer
Authors: Kenichi Yanagida Kenichi Yanagida , Hiroshi Yoshikawa Hiroshi Yoshikawa , Akihiko Mizuno Akihiko Mizuno , Shinsuke Suzuki Shinsuke Suzuki , Toshihiko Hori Toshihiko Hori , Yuichi Itoh Yuichi Itoh , Hideaki Yokomizo Hideaki Yokomizo
Published: October 2002

The mechanism of the current transformer is analyized, and its expression is derived as a complex function of the frequency spectrum or as a real function of the time evolution. These formulae include the effect of magnetic material, which is usually a part of the current transformer, and cause a multiple droop phenomenon in the time evolution. It becomes clear that the multiple droop phenomenon is enhanced in the case of a few turns of secondary windings, such as in a wall current monitor. In the case of many turns of secondary windings, the longest droop component becomes dominant, and the remaining shorter droop components disappear.
Measurement of Glancing Incidence-Exit X-ray Scattering in Reflection High Energy Electron Diffraction and Total-Reflection-Angle X-ray Spectroscopy System
Authors: Ziyuan Liu Ziyuan Liu , Seiya Ogota Seiya Ogota , Tadataka Morishita Tadataka Morishita
Published: October 2002

We developed the total-reflection-angle X-ray spectroscopy in reflection high energy electron diffraction (RHEED-TRAXS) experiments method (measuring X-rays at glancing exit angle) by introducing glancing incidence X-rays into a RHEED-TRAXS system so that the measurement of glancing incidence-exit X-ray scattering (GIEXS) has been realized. Nanometer scale islands, deposited on a sample surface in the RHEED-TRAXS system, were excited by an electron beam to generate characteristic X-rays. These X-rays impinge on the sample surface at small glancing angle to play a role of glancing incidence; thus, the TRAXS observation of the X-rays emitted from islands is equivalent to X-ray measurement under glancing incidence-exit geometry. Applying the GIEXS method to surface layer analysis for the SrTiO3 (001) single crystal, we found that the critical angle of total reflection observed by the GIEXS method can be used to determine the composition of the surface atomic layer.
Antenna-Coupled Warm Carrier Device Using Polycrystalline Ge Film Vacuum Deposited on ZnS Substrate
Authors: Uchida Takashi , Takashi Shimizu Takashi Shimizu , Yoshizumi Yasuoka Yoshizumi Yasuoka
Published: October 2002

The Hall mobility of Ge thin films deposited on ZnS substrates at a substrate temperature of 600° C was 360 cm2/ V·s for a hole concentration of 3×1017 cm-3. This value was about 3.6 times larger than that obtained for Ge films deposited on Si3N4 substrates. A point-contact warm carrier device fabricated using Ge film deposited on ZnS substrate has a detected voltage for CO2 laser radiation about ten times higher than that of a device fabricated using Ge film deposited on Si3N4 substrate.
Magnetically Induced Superresolution Using Interferential In-Plane Magnetization Readout Layer
Authors: Junji Hirokane Junji Hirokane , Akira Takahashi Akira Takahashi
Published: October 2002

A magnetically induced superresolution (MSR) readout method using an in-plane magnetization mask was investigated. The magnetooptical disk consisted of an interference layer, a readout layer, a transparent intermediate layer, a recording layer and a protective layer. The use of the readout layer enabled center aperture detection which was suitable for a mark edge readout system. In this investigation, the film thickness of the readout layer was 20 nm, so the polar Kerr rotation angle is enhanced because of optical interference. The use of the interferential MSR readout method with an in-plane magnetization mask enabled excellent readout and recording characteristics to be obtained.
Doping of Phosphoric Acid into Ferroelectric Triglycine Sulfate Crystal
Authors: Noriyuki Nakatani Noriyuki Nakatani , Masakazu Yoshio Masakazu Yoshio
Published: October 2002

Single crystals of phosphoric-acid-doped triglycine sulfate (TGSP) were grown from solutions with various concentrations of H3PO4. The concentration of dopant in the crystal and the P–E hysteresis loop have been investigated. The concentration in the crystal is much lower than that in solution. The incorporation of H3PO4 molecule is highly inhomogeneous in the crystal and depends on the crystal growth sector. The doping generates no internal bias field and has no influence on the spontaneous polarization. Since the incorporated H3PO4 molecules act as obstacles to polarization switching, doping results in an the increase in coercive field E
c. There is a distinct correlation between the intensity of E
c and the concentration of H3PO4 in the crystal.
Temperature Dependence of Conductivity of Nitrogen-Containing Diamondlike Carbon Films Deposited from Pyridine
Authors: Uchida Masao , Hiroyoshi Tanaka Hiroyoshi Tanaka , Koichi Kotera Koichi Kotera
Published: October 2002

We investigated the effects of atmospheric and substrate temperatures on diamondlike carbon (DLC) films prepared by biased thermal-filament plasma chemical vapor deposition using vapor benzene and pyridine as a source. The DLC film deposited from pyridine which contains a nitrogen atom was conductive. Although the conductivity was dependent on the substrate temperature in the deposition process, the concentration of nitrogen and hydrogen in the conductive film was not. The reason for the dependence is the increase in number of hopping sites and the delocalization of π electrons with increasing substrate temperature.
Carbon Contamination Levels in Plasma-Enhanced Chemical Vapor Deposited Fluorinated Silica Glasses
Authors: Richard Swope Richard Swope , Woo Sik Yoo Woo Sik Yoo
Published: October 2002

In this study, the carbon levels in fluorinated silica glass (FSG) films were investigated. FSG films were deposited using a dual-frequency sequential-deposition plasma-enhanced chemical vapor deposition (PECVD) reactor using TEOS, O2 and C2F6 as source reagents. It was found that FSG films have substantially lower carbon levels than undoped PECVD TEOS-based silicon dioxide films. Carbon content was also found to be dependent on the fluorine content in the films.
Theoretical Analysis of 70 GHz Slow Surface Wave Propagation in Transversely Magnetized Partially Filled Ring-Form Solid-Plasma Waveguide
Authors: Tetsuo Obunai Tetsuo Obunai
Published: October 2002

Wave propagation in a 70 GHz transversely magnetized partially filled ring-form solid-plasma waveguide has been theoretically analyzed assuming the plasma material to be an n-type InSb ring at liquid nitrogen temperature. Surface wave resonant characteristics of two possible propagation modes and their dependence upon the waveguide curvature have been numerically analyzed. The results of the previously performed experiments are in good qualitative agreement with the calculated results for one of these modes. These findings both theoretically and experimentally confirm the existence of the slow surface wave resonance in the waveguide concerned.
Method of Characterizing Rubbed Polyimide Film for Liquid Crystal Display Devices Using Reflection Ellipsometry
Authors: Ichiro Hirosawa Ichiro Hirosawa
Published: October 2002

Reflection ellipsometry is applied to characterize the molecular orientation of rubbed polyimide films for liquid crystal display devices. Thickness, dielectric constants and tilt angle of the principal dielectric axis of the molecularly oriented upper layer and thickness of the random layer in rubbed polyimide films can be determined by analyzing the anisotropic polarization of reflected light.
Application of Thermal Desorption Spectroscopy to the Study of Defects Induced by Arsenic Implantation
Authors: Saito Kazuyuki , Sato Yoshiyuki , Yabumoto Norikuni , Homma Yoshikazu
Published: October 2002

The defects induced by through-oxide implantation of arsenic into silicon have been studied using thermal desorption spectroscopy (TDS) after hydrogen adsorption on the defects. TDS peaks observed at 350° C and at 540° C are assigned to the desorption of hydrogen when divacancies are recovered and when the recrystallization takes place. This paper confirms that TDS is a useful tool for investigating the annealing behavior of implanted defects.
Oxide-Voltage and Its Polarity Dependence of Interface-State-Generation Efficiency in (100) n-Si Metal/Oxide/Semiconductor Capacitors
Authors: Masao Inoue Masao Inoue , Akihiro Shimada Akihiro Shimada , Junji Shirafuji Junji Shirafuji
Published: October 2002

The polarity dependence of Fowler-Nordheim (F-N) tunneling current stress on the interface-state-generation efficiency in (100) n-type Si metal/oxide/semiconductor (MOS) capacitors has been investigated as a function of oxide voltage using the ac conductance method. The interface-state-generation efficiency η gen is larger when the F-N tunneling electrons are injected from the gate (gate emission) than when they are injected from the substrate (substrate emission) by about two orders of magnitude over the whole range of the oxide voltage employed. Moreover, the values of η gen for both polarities depend significantly on the oxide voltage in a similar fashion. The measured generation efficiency is combined with the critical electron fluence Q
BD for dielectric breakdown reported to date to demonstrate that the critical interface-state density for breakdown is independent of Q
BD and the oxide voltage.
Study of the Tunneling Characteristics of Ba1-xKxBiO3 Superconducting Thin Films Based on the Gap-Energy Distribution Model
Authors: Yamamoto Tetsuya , Suzuki Seiji , Iyori Masahiro , Yamano Koji , Suzuki Hiroshi , Kazuhiko Takahashi Kazuhiko Takahashi , Yorinobu Yoshisato Yorinobu Yoshisato
Published: October 2002

The broadening of the gap edge in the conductance-voltage ( dI/ dV–V) characteristics for native-barrier Ba1-
x

K

x

BiO3-gold (BKBO//Au) and MgO-barrier Ba1-
x

K

x

BiO3-gold (BKBO/MgO/Au) junctions was investigated by using a gap-energy distribution model where the inhomogeneity of the energy gap Δ at the junction interface was taken into consideration. It was demonstrated that the broadening of the dI/ dV–V curves and their temperature dependence (T<2T
C/3) in both junctions could be explained by assuming the Gaussian distribution of gap energies (at T=0 K) with Δ0(0)=3.1 meV, δΔ=0.9 meV for the BKBO//Au junction and Δ0(0)=3.5 meV, δΔ=1.1 meV for the BKBO/MgO/Au junction, where Δ0(0) and δΔ represent the center point and the width of the distribution, respectively. It was found that the value δΔ could be regarded as a criterion for the quality of the tunneling junction.
In-Situ Cleaning of SiO2-Patterned GaAs Surface with Trisdimethylaminoarsine for Selective Regrowth
Authors: Ortion Jean Michel , Cordier Yvon , Garcia Jean Charles , Didier Adam Didier Adam , Claude Grattepain Claude Grattepain
Published: October 2002

Trisdimethylaminoarsine (TDMAAs) has been used to clean SiO2-patterned GaAs surfaces prior to selective regrowth. Under TDMAAs pressure, the native oxide was completely removed at 480° C which is 110° C lower than the temperature of thermal oxide desorption. Compared to oxide removal with arsine, the morphology and the purity of the deoxidized surface are improved with TDMAAs cleaning. It was found that additional ex-situ chemical treatments further improve the cleaning. With the proper ex-situ preparation and TDMAAs cleaning, secondary ion mass spectrometry (SIMS) shows the removal of carbon at the regrowth interface to levels below the residual carbon concentration, while oxygen and silicon impurity concentrations are, respectively, 7.8×1011 cm-2 and 1.7×1011 cm-2. The carrier depletion at the regrowth interface is reduced to 2.6×1011 cm-2 and contact resistivity is lowered to 2.7×10-6 Ω· cm2.
Suppression of Boron Penetration in BF2
+-Implanted Poly-Si Gate
Authors: Chao Tien Sheng , Chu Chih-Hsun , Wang Chuan Fu , Ho Kuai Junz , Lei Tan. Fu , Lee Chung Len
Published: October 2002

In this paper, a comprehensive study of gate engineering to suppress the penetration of boron in p-type metal-oxide-semiconductor field-effect transistor (MOSFET) with the p+-poly-Si-gate is reported. Four types of poly-Si gate structure, two types of gate dielectrics were investigated to suppress the boron penetration. Among the different gate structures, the stacked amorphous silicon structure was found to be the most effective way to retard the boron penetration. N2O oxide exhibited a better retarding of the boron diffusion as compared with the O2 oxide. It was found that a combination of stacked amorphous silicon with N2O oxide is the most effective way to suppress the boron penetration. Thermal stability, oxide integrity, and D
it of this sample are superior to all the other samples.
Measurement of Carrier Concentration at the GaAs–Si Interface in GaAs on Si by Raman Scattering
Authors: Futagi Toshiro , Tachikawa Akiyoshi , Jono Aiji , Morikawa Yoji , Takashi Aigo Takashi Aigo , Akihiro Moritani Akihiro Moritani
Published: October 2002

The free carrier concentration in GaAs-on-Si was measured by Raman scattering at the GaAs back face which is revealed by etching the Si substrate. Asymmetric Raman spectra attributed to the coupled plasmon-longitudinal optical (LO) phonon mode ( L+) observed in the range of 400 to 700 cm-1 indicate that an electron concentration greater than 1.6×1018 cm-3 is induced by incorporation of Si atoms into the GaAs layer at the Si–GaAs interface in metal-organic chemical vapor deposition (MOCVD) grown GaAs-on-Si's at 700° C for 15 min.
Recovery Process of the Conductance of Au Electrode on YBa2Cu3O7-δ
Authors: Oka Katsutoshi , Takeo Iri Takeo Iri , Nobuyoshi Yamada Nobuyoshi Yamada
Published: October 2002

The recovery of the electrode conductance for Au metal on YBa2Cu3O7-δ (YBCO) has been investigated. The reduction in the electrode resistance, which is defined as the inverse of the electrode conductance, was measured during heat treatment ranging from 150 to 280° C. The reduction has been characterized by two relaxation processes with activation energies of 0.52±0.04 and 1.40±0.03 eV. The former activation energy corresponds to that of the process in which the oxygen-deficient layer at the YBCO surface is replenished by oxygen diffusion from the bulk, and the latter to that of the process of rearrangement of Au atoms at the YBCO/Au interface which results in improved interconnections between Au metal and YBCO.
Growth and Characterization of Vertical-Cavity Surface-Emitting Lasers Grown on (311)A-Oriented GaAs Substrates by Molecular Beam Epitaxy
Authors: Takahashi Mitsuo , Vaccaro Pablo O. , Watanabe Toshihide , Mukaihara Toshikazu , Koyama Fumio , Iga Kenichi
Published: October 2002

We have fabricated InGaAs/GaAs vertical-cavity surface-emitting lasers (VCSELs) grown on GaAs(311)A substrates by molecular beam epitaxy. High-quality crystals for VCSEL structures on (311)A having flat and smooth heterointerfaces were obtained by optimizing the growth conditions. It was experimentally demonstrated that the optical anisotropic gain of (311)-oriented strained-layer quantum wells is effective for polarization control. A [*BAR*2*BAR*33] polarization mode is stable against the injection currents of 3 times the threshold. In addition, the threshold current density of 80 A/(cm2·well) is achieved for a device with a laser aperture as large as 25 µ m square, which is comparable to or even lower than that of (100)-oriented VCSELs.
Emission Spectra of an Atom for Multiphoton Jaynes-Cummings Model
Authors: Kuniaki Matsuo Kuniaki Matsuo , Hiroshi Iwasawa Hiroshi Iwasawa
Published: October 2002

The emission spectra of an atom in a cavity for the multiphoton Jaynes–Cummings model are investigated. Using Eberly's formula for the time-dependent physical spectrum, the analytical expression for the atomic emission spectrum is obtained from the two-time dipole-moment correlation function of the atom. The appearance of two strong peaks in the spectrum is explained in detail, and the relationship between the initial photon distributions and the shapes of the spectra are examined. The fundamental differences in the atomic emission spectra for the two-photon and multiphoton models are specified. Furthermore, the role of the detector filter is thoroughly studied. It is explicitly shown that the atomic emission spectra can be obtained by averaging over the convolution integrals between the Fourier transform of the atomic dipole-moment correlation function associated with a pure number state and the detector filter function on frequency domain. The comparisons of the spectra for a coherent initial field to those for a thermal initial field are presented.
The AC Electrical Behavior of Hydrothermally Synthesized Barium Titanate Ceramics
Authors: Zhu Weidong , Wang Ching Chyr , Akbar Sheikh A. , Asiaie Reza , Dutta Prabir K. , Alim Mohammad A.
Published: October 2002

The ac electrical response of hydrothermally synthesized polycrystalline barium titanate ( BaTiO3) was studied as a function of frequency using immittance measurements at temperatures ranging from 200 to 500° C in air. Two semicircular relaxations were observed in impedance (Z
*) and modulus (M
*) planes. The capacitance of the high-frequency relaxation obtained from these complex planes showed a Curie-Weiss behavior originating from a lumped grain contribution. The low-frequency relaxation exhibited a high capacitance which was invariant with temperature, suggesting a possible grain-boundary contribution. The grain-boundary resistance was found to be higher than that of grains at all temperatures. An equivalent circuit consisting of two parallel R
C combination in series is evident from the Z
*- and M
*-plane analyses, and represents the individual contribution of grain and grain-boundary regions of the polycrystalline sample. Another circuit consisting of a series R
C combination in parallel with a dc resistance (R
0) and a high-frequency limit capacitance (C
∞) is identified. This circuit portrays a possible trapping effect revealed by the admittance (Y
*) and capacitance (C
*) plane analyses. The two circuits are equivalent and complementary to each other as they together provide more information on the operative electrical processes in the sample.
Molecular Fluctuations in Smectic Phases Possessing Antiferroelectric Ordering
Authors: Hiraoka Kazuyuki , Uematsu Yoshiko , Takezoe Hideo , Fukuda Atsuo
Published: October 2002

In order to investigate molecular fluctuation in chiral smectic phases that possess antiferroelectric ordering, we have carried out electrooptic measurements of linear and second harmonic responses in 4-(1-methylheptyloxy-carbonyl)phenyl 4′-octyloxybiphenyl-4-carboxylate (MHPOBC) which has two antiferroelectric smectic phases, namely, smectic Cα
* ( SmCα
*) and smectic C
A

* ( SmC
A

*). In the SmC
A

* phase, we confirmed the relaxation of the antiferroelectric phase mode corresponding to the symmetry-recovering Goldstone mode in the frequency dispersion of optical responses under a sinusoidal electric field. However, no evidence of the antiferroelectric phase mode was found in the SmCα
* phase, although we recognized the relaxation corresponding to the ferroelectric phase mode. In addition, we speculate on the fluctuation models responsible for the electrooptic behavior in the SmCα
* and SmC
A

* phases.
Structural Analysis of Collagen Fibrils in Rat Skin Based on Small-Angle X-Ray-Diffraction Pattern
Authors: Itoh Takashi , Tsuchiya Hajime , Yoshimura Yumi , Masato Hashimoto Masato Hashimoto , Takashi Konishi Takashi Konishi
Published: October 2002

A superhelix structure is proposed to explain the short band period (65 nm) observed in rat skin collagen fibrils in comparison with that of tendon collagen fibrils (67 nm). In the former case, each molecule forms an angle of 12–13° with the fibril axis and almost ten tropocollagen molecules aggregate to form a tilting plane in a bundle or a subfibril. The adjacent bundles may be staggered with respect to each other by a length of ten amino acid residues along the chain axis to form the band structure observed to be normal to the fibril axis. This model is found to be quantitatively consistent with small-angle X-ray diffraction data obtained from uniaxially oriented collagen fibrils in native rat skin as well as a transmission electron microscopic image of freeze-etched fibrils in glycerinated rat skin.
Monte Carlo Simulation of Yield and Energy Distribution of Secondary Electrons Emitted from Metal Surfaces
Authors: Kaoru Ohya Kaoru Ohya , Akio Harada Akio Harada , Jun Kawata Jun Kawata , Kenji Nishimura Kenji Nishimura
Published: October 2002

A Monte Carlo simulation of secondary electron emission from Be (atomic number Z=4), Mg (Z=12), Al (Z=13), Mo (Z=42) and W (Z=74) due to 100 eV–4 keV electron impacts is performed in order to understand the primary energy (E
p) dependence of the yield and the energy distribution of secondary electrons. The E
p-dependence of the secondary electron yield calculated for the metals is characterized in terms of the maximum yield and E
p at which it occurs, which are in good ageement with Kollath's empirical formula for E
p where the formula can be applied. At high E
p (>1 keV), the calculated energy distribution of the secondary electrons, except for Mg which has a low surface potential barrier, approaches the E
p-independent theoretical curve derived by Chung and Everhart. At low E
p, however, the energy distribution largely depends on E
p, in particular for high-Z metal.
A New Silicon Detector Telescope for Measuring the Linear Energy Transfer Distribution over the Range from 0.2 to 400 keV/µm in Space
Authors: Tadayoshi Doke Tadayoshi Doke , Takayoshi Hayashi Takayoshi Hayashi , Nobuyuki Hasebe Nobuyuki Hasebe , Jun Kikuchi Jun Kikuchi , Sachiko Kono Sachiko Kono , Takeshi Murakami Takeshi Murakami , Takao Sakaguchi Takao Sakaguchi , Kenichi Takahashi Kenichi Takahashi , Takeshi Takashima Takeshi Takashima
Published: October 2002

A new telescope consisting of three two-dimensional position-sensitive
silicon detectors which can measure the linear energy transfer
(LET) distribution over the range
from 0.2 to 400 keV/µ m has
been developed as a real-time radiation monitor in manned
spacecraft. First, the principle of LET measurement and its design method
are described. Second, suitable electronic parameters for the LET measurement
are experimentally determined. Finally, the telescope performance is
investigated by using relativistic heavy ions. The first in-flight test of this
type of telescope on the US Space Shuttle (STS-84) is scheduled for May, 1997.
Nuclear Resonant Excitation of 161Dy and 151Eu by Synchrotron Radiation
Authors: Koyama Ichiro , Yoda Yoshitaka , Zhang Xiao Wei , Ando Masami , Seishi Kikuta Seishi Kikuta
Published: October 2002

We report the first observation of nuclear resonant excitation of the 25.7 keV level of 161Dy and the 21.5keV level of 151Eu by synchrotron radiation. Time-delayed emission of L X-rays produced in the internal conversion process was used to facilitate this observation.
Transient Beam Loading in Extended Constant-Gradient Structures, Combined with SLED (SLAC's Energy Doubler) in Electron Linac
Authors: Isamu Uetomi Isamu Uetomi
Published: October 2002

A transient beam-loading theory is developed for extended constant-gradient (XCG) structures, and applied to single bunched beam acceleration, using RF power multiplied by SLAC's energy doubler (SLED). It is shown that XCG structures for constant accelerating fields and maximum energy gain have different beam-loading parameters.
Advantages of a SiOxNy:H Anti-Reflective Layer for ArF Excimer Laser Lithography
Authors: Ogawa Tohru , Sekiguchi Atsushi , Noritsugu Yoshizawa Noritsugu Yoshizawa
Published: October 2002

This paper presents the advantages of using hydrogenated silicon oxynitride ( SiO

x

N

y

:H) film as an anti-reflective layer (ARL) for argon fluoride (ArF) excimer laser lithography. This material has already been used as an ARL in both i-line and krypton fluoride (KrF) excimer laser lithography, because its refractive indices can be controlled by varying the deposition conditions. We describe the results of measuring the optical constants for the various materials at the wavelength of 193 nm using a spectroscopic ellipsometer to clarify the importance of the anti-reflective process. The influence of the thin-film interference effects in the photoresist of the 193 nm wavelength are almost same as that of the 248 nm. Then we describe the possibility of using the SiO

x

N

y

:H film as an ARL at the wavelength of 193 nm, from the standpoint of the spectroscopic characteristics in the optical constants. The SiO

x

N

y

:H film is desirable for use as an ARL. Finally, we propose that SiO

x

N

y

:H film has great potential as a high-performance ARL for ArF excimer laser lithography.
Direct Patterning of Spin-on-Glass Materials by ArF Excimer Laser Irradiation and Their New Application to Hard-mask Processes
Authors: Taku Morisawa Taku Morisawa , Hiroshi Fukuda Hiroshi Fukuda
Published: October 2002

Several spin-on-glass (SOG) materials were examined as single layer resists for ArF excimer laser lithography, with the goal of directly forming a hard mask from these materials for dry-etching underlying metal films. Perhydro-silazane (PHSN) was found to be photo-reactive at 193 nm wavelength as well as polyphenylmethyl-silsesquioxane (PMSQ) and polyhydroxybenzyl-silsesquioxane (HSQ), which we have reported previously. These materials showed a sufficient resolution performance and sensitivity at 193 nm. The Fourier-transform infrared (FTIR) and X-ray photoelectron spectrometry (XPS) analyses showed that the basic reaction is photo-oxidation, though the imaging mechanism in each material is quite different. The etching resistance of these materials was significantly improved by special treatment after patterning, whereas those without the treatment were insufficient. For example, etching rate of PHSN after baking in steam ambient was comparable to that for CVD SiO2 in RIE using SF6 gas. 0.2 µ m patterns were transferred into poly-Si films by dry-etching using these materials as hard masks.
Nanofabrication with a Novel EB System with a Large and Stable Beam Current
Authors: Yoshimura Toshiyuki , Ohta Hiroya , Yamamoto Jiro , Uchino Shou-ichi , Yasushi Gotoh Yasushi Gotoh , Tsuneo Terasawa Tsuneo Terasawa
Published: October 2002

We describe nanofabrication using a novel electron beam (EB) system that has a large and stable beam current, combined with high resolution resists. This system has a low aberration objective lens and a Zr/O/W cathode that provides a probe current of 1.2 nA. By detecting Si-groove marks, the system achieves high overlay accuracy of within 10 nm ( mean+3σ) over large areas. We have realized resist nanofabrication down to 10 nm with small nano edge roughness. By introducing a hard mask consisting of a thin (25 nm) SiO2 layer, we have also obtained a poly-Si gate structure of 30 nm on a thin (4 nm) gate oxide.
A 100 kV Electron Gun for the X-Ray Mask Writer, EB-X2
Authors: Saito Kenichi , Kato Junichi , Nobuo Shimazu Nobuo Shimazu , Akira Shimizu Akira Shimizu
Published: October 2002

A 100-kV thermal-emission electron gun was developed for the X-ray mask writer EB-X2, which employs a variable-shaped electron beam with a beam edge resolution of 20 nm. The optimized design of the EB-X2 electron optical system requires that the electron gun has crossover diameters of 50 µ m and an optical length of less than 100 mm. So the crossover diameters of the gun were accurately calculated with an electron ray tracing program, and a gun with the required crossover diameters and optical length was designed. The gun was constructed, and the crossover diameters were measured. The measured values agree well with the calculated ones, and this confirms that the gun is suitable for use in the EB-X2 electron optical system.
A Simple Fabrication Process of T-Shaped Gates Using a Deep-UV/Electron-Beam/Deep-UV Tri-Layer Resist System and Electron-Beam Lithography
Authors: Lai Yeong-Lin , Chang Edward Y. , Chang Chun-Yen , Yang Hung-Pin D. , Nakamura K. , Shy S. L.
Published: October 2002

A new fabrication process of T-shaped gates has been developed using a deep-UV/electron-beam/deep-UV (DUV/EB/DUV) tri-layer resist system and electron-beam lithography for the first time. The simple process accomplished a submicron T-shaped gate by a single exposure and a single development step. The narrow/wide/narrow opening of the DUV/EB/DUV resist structure can be accurately controlled by the e-beam dosage and the development conditions. Differences in the sensitivities of the DUV resist and the EB resist were investigated. Due to the lower sensitivity of the adopted DUV resist to the electron beam, the smaller opening of the DUV resist layer was obtained. The higher sensitivity of the EB resist resulted in a wider opening in the middle resist layer. A 0.15-µm-gate-length T-shaped gate can be easily formed by the short-process-time and low-production-cost hybrid DUV/EB/DUV resist approach.
Photon-Stimulated Ion Desorption Measurement of Organosilicon Resist Reactions in Extreme Ultraviolet Lithography
Authors: Ogawa Taro , Yamaguchi Atsuko , Yamanashi Hiromasa , Ito Masaaki , Tachibana Hiroaki , Matsumoto Mutsuyoshi , Sekitani Tetsuji , Tanaka Kenichiro
Published: October 2002

In extreme ultraviolet (EUV) lithography, a surface-imaging process using an organosilicon resist is essential. Since the binding energies of Si core-level electrons coincide with the photon energy of the light source of EUV-lithography, we have analyzed the effect of their excitation on the decomposition of an organosilicon resist. We have also investigated a design policy for optical systems in terms of selecting the multilayer mirror materials to use organosilicon resists in EUV lithography. A photon-stimulated ion desorption (PSID) analysis of poly(cyclohexylmethylsilane) (PCHMS) that was exposed to monochromatic synchrotron radiation was carried out. We found that decomposition of the Si–Si backbone of PCHMS is enhanced by EUV exposure to wavelengths that excite the Si 2p and 2s electrons. In addition, the yield of CH3
+ desorbed from the side-chain methyl of PCHMS is increased at a photon energy of 108 eV (a 11.5-nm wavelength), which presumably excites Si 2p electrons into the Si–C σ* state. Calculated reflectivities of a multilayer mirror suggest that the reflectivity of a multilayer mirror which does not contain Si, such as Mo/Be, realizes excellent reflectivity at the wavelength that excites the Si 2p electron.
Proton Transfer to Melamine Crosslinkers in X-Ray Chemically Amplified Negative Resists Studied by Time-Resolved and Steady-State Optical Absorption Measurement
Authors: Nagahara Seiji , Yamashita Yoshio , Taguchi Takao , Kozawa Takahiro , Yoichi Yoshida Yoichi Yoshida , Seiichi Tagawa Seiichi Tagawa
Published: October 2002

Proton transfer to melamine crosslinkers has been analyzed in three X-ray chemically amplified (CA) negative resists. One is an in-house fabricated resist composed of m-cresol novolac, 2,4,6-tris (trichloromethyl)-1,3,5-triazine (TCT), and hexamethoxymethylmelamine (HMMM). The other two are commercially available resists: SAL-601 (Shipley Co.) and AZ-PN 100 (Hoechst Co.). The behavior of protons induced by X-ray exposure was analyzed using both conventional steady-state optical absorption spectroscopy and nanosecond time-resolved absorption spectroscopy (pulse radiolysis). The results indicate that the protons are transferred from the proton adducts (acid precursors) of matrix polymers to the melamine crosslinker in a very early step. This proton transfer was much faster than that from the proton adducts of matrix polymers to dissolution inhibitors in CA positive resists.