bluuebunny/crossref_metadata_2025 huggingface dataset:
Diagonal Phase Errors Affecting Optical Intensity in Phase Defect Repair Elements
Authors: Ohtsuka Hiroshi , Kazuyuki Kuwahara Kazuyuki Kuwahara , Toshio Onodera Toshio Onodera
Published: February 2005

The phase shift method (PSM) improves practical resolution in optical lithography, but phase defects in masks significantly degrade image integrity. Mask repair reduces the effects of these defects by satisfying both phase step and diagonal phase conditions. Repair methods optimized for phase defects of π/2 and π are discussed. Analysis of diagonal phases in the vicinity of defects has been used to determine the approprinate conditions for restoring optical intensity. Repair elements are produced using a simple focused ion beam (FIB) milling process. The location and phase of each repair element are optimized to reduce the required number of repair elements. Effectiveness of the repair technique is verified using an i-line resist process.
Preparation and Characteristics of a Superconducting Base Transistor with an Au/Ba1-xKxBiO3/Niobium-Doped SrTiO3 Structure
Authors: Suzuki Hiroshi , Yamamoto Tetsuya , Suzuki Seiji , Iyori Masahiro , Takahashi Kazuhiko , Usuki Tatsuro , Yorinobu Yoshisato Yorinobu Yoshisato , Shoichi Nakano Shoichi Nakano
Published: February 2005

We have observed the fundamental operation of a superconducting base transistor using a Ba1-x
K
x
BiO3 (BKBO) oxide superconductor. The transistor had a structure consisting of planar-type Au/natural-barrier/BKBO/niobium-doped SrTiO3 (STO:Nb), where Au, BKBO and STO:Nb correspond to the emitter, base and collector in the transistor, respectively. The Au/natural-barrier/BKBO emitter-base junction showed good tunneling characteristics, reflecting the superconductivity of BKBO. The BKBO/STO:Nb base-collector junction showed asymmetric I-V characteristics. Electrical measurements during transistor operation revealed collector current increment as the emitter current increased at 4.5 K. Furthermore, a transistor with a 100-nm thick base layer showed a maximum common-base current gain of over 0.5 at 4.5 K.
The Migration Path of Co Ions in Co-Substituted Spinel Ferrite Thin Films during Magnetic Annealing
Authors: Na Jong-Gab , Lee Taek-Dong , Kim Eng-Chan , Kim Chul-Sung , Park Soon-Ja
Published: February 2005

The migration path of Co ions in Co-substituted spinel ferrite thin films is investigated in detail during magnetic annealing. To this end, changes in the saturation magnetization were measured as a function of magnetic annealing time at various temperatures. Changes in Mössbauer spectra were also taken. The ferrite thin films were prepared by a reactive sputtering method. For Co-substituted ferrite thin films annealed at various temperatures, peaks were observed in the plots of the saturation magnetization vs annealing time, whilst the saturation magnetization remained nearly constant for Co-free ferrite thin films during magnetic annealing. From a subsequent Mössbauer spectroscopic investigation, it was confirmed that the peaks in the saturation magnetization-annealing time curves for Co-substituted ferrite thin films are originated from cation redistribution, i.e., the migration of Fe ions on tetrahedral sites (A sites) to octahedral sites (B sites) and Co ions on the B sites to the A sites.
Improvement of the Cerenkov Radiative Second Harmonic Generation in the Slab Waveguide with a Periodic Nonlinear Optical Susceptibility
Authors: Yuji Azumai Yuji Azumai , Heihachi Sato Heihachi Sato
Published: February 2005

Introducing a periodically corrugated nonlinear optical (NLO) susceptibility χ(2) in the guiding layer of a three-layered slab waveguide, we propose a Cerenkov radiative second harmonic generation (SHG) with numerical calculations, and experimentally demonstrate it. With vinylidene cyanide/vinyl acetate copolymer film having a sinusoidal χ(2) corrugation of 60 µm period as a guiding layer, the Cerenkov scheme of SHG was enhanced over a wide film thickness range at 1.06-µm fundamental wavelength, obtaining an enhancement factor of ∼1.5 in comparison with a uniform χ(2) scheme. Experimental dependences of the SHG power on both corrugation period and path length agree well with theoretical estimates, indicating usefulness of the modified Cerenkovian SHG with the corrugated χ(2).
Fundamental Physics and Promising Applications of Superionic Conductors
Authors: Hiroo Yugami Hiroo Yugami , Mareo Ishigame Mareo Ishigame
Published: February 2005

Recently, superionic conductors (SIC's) have been considered to be a key material for several application fields as well as energy engineering and ceramic technology. We review the recent stage of the basic models and concepts for the physical understanding of high-speed ionic transport in solids. In the latter part of this paper, we briefly review the applications of SIC's to solid-state fuel cells and sensors. As a new application of SIC's, we introduce a technique developed on a complex system consisting of an oxygen ionic conductor and high-T
c oxide super-conductors. Finally, we introduce the possibility of the application of SIC's to optical devices.
Uniform Field Electrodes for High-Power and High-Repetition TEA-CO2 Lasers
Authors: Ishii Akira , Okita Yuji , Yasuoka Koichi , Tamagawa Tohru , Satoshi Nakagawa Satoshi Nakagawa , Iwao Ohshima Iwao Ohshima
Published: February 2005

A new electrode system has been specially developed for high-power and high-repetition transversely excited atmospheric (TEA)-CO2 lasers. The new system produces a uniform glow discharge compared that in a conventional Chang electrode system. In this new system, the laser beam energy profile shows a nearly flat top configuration and the repetitive rate of maximum output power has been increased from 175 Hz to 350 Hz. The discharge energy density profile is calculated to estimate the influence of gas density fluctuation. The numerical result shows that the maximum fluctuation of gas density is 10% less in this electrode system.
Impurity Species in Synthetic and Brazilian Natural Quartz
Authors: Fumiko Iwasaki Fumiko Iwasaki , Hideo Iwasaki Hideo Iwasaki
Published: February 2005

Impurity species in synthetic and Brazilian natural quartz were studied by means of infrared absorption spectroscopy and atomic absorption spectrometry. It is shown that almost all of the Al ions in synthetic quartz are incorporated as a substitutional type of Al(3+). The possibility of the existence of interstitial Al is small. In the formation of Al-related centers in crystals grown in Li-containing solution, the dominant charge compensator for Al(3+) is Li(+). In natural quartz, the charge of Al(3+) is compensated by Li(+) and H(+) to form Al-Li and Al-OH centers. Na(+) ions are incorporated into crystal with H2O impurities both in synthetic and natural quartz. The content of Al-hole centers due to γ irradiation is approximately proportional to the content of Al-Li centers and inversely proportional to H2O impurity content.
New Method of Preparation and Some Properties of Electrochromic MoO3 Thin Layer
Authors: Margit Tölgyesi Margit Tölgyesi , Mihàly Novàk Mihàly Novàk
Published: February 2005

A new method for large area preparation of electrochromic MoO3 thin film on ITO glass has been developed. In the electroless procedure the Cu-metal covered ITO glass was sprayed by 0.5 mol/dm3 lithium molybdate solution of 0.5-1.5 pH and blue oxide film was obtained. Experiments were carried out for the cathodically deposited films, too. The optical properties of the two layers showed the same pattern.
Reflection High-Energy Electron Diffraction Oscillation during CaF2 Growth on Si(111) by Partially Ionized Beam Epitaxy
Authors: Watanabe Masahiro , Nobuhiro Suzuki Nobuhiro Suzuki , Masahiro Asada Masahiro Asada
Published: February 2005

We have observed reflection high-energy electron diffraction (RHEED) intensity oscillation in the growth of single-crystalline CaF2 on Si(111) by partially ionized beam epitaxy at relatively low growth temperature (440°C). During and after the growth, the RHEED pattern of the CaF2 shows single-crystalline nature using this epitaxy technique, whereas polycrystalline CaF2 is grown without ionization and acceleration at the same temperature level. In the high-temperature range (>600°C), although single-crystalline CaF2 is obtained without acceleration, RHEED oscillation is not observed during the growth.
Structural Changes and Annealing Behavior of Ar-Ion-Irradiated Superconducting BiSrCaCuO Thin Films
Authors: Masatsugu Kaise Masatsugu Kaise , Kazuo Saito Kazuo Saito
Published: February 2005

Superconducting mixed phase BiSrCaCuO thin films containing mainly the low-T
c phase were irradiated with 100 keV Ar ions up to 4×1017 ions/cm2 at 10 K or 300 K and were subsequently annealed below 800°C. The irradiated thin film was considered to consist of a heavily damaged surface layer and an underlying partially displaced crystalline layer. X-ray diffraction studies showed that a specific phase transformation occurs during postannealing at relatively low temperatures, 700-730°C, i.e., irradiated layer→high-T
c (2223) phase+Ca-free (2201) phase. The high-T
c phase ratio and the T
c of the films were markedly improved by an Ar ion dose of 2×1016 ions/cm2 at 10 K, prior to the low temperature annealing. Preirradiation at 10 K was more effective for improving superconducting properties of the films than preirradiation at 300 K.
Broad Tuning of Nd:YVO4 Green Laser by Temperature Control of Intracavity KTiOPO4
Authors: Honda Tokuyuki , Morimoto Hiroyuki , Hirokazu Matsumoto Hirokazu Matsumoto
Published: February 2005

The optical frequency of the green output of a laser-diode-pumped Nd:YVO4 laser is tuned over 400 GHz by introducing a Brewster window and by varying the temperature of an intracavity KTiOPO4 (KTP) crystal.
Preparation and Electrical Property of Polypyrrole-Polyethylene Composite
Authors: Yoshino Katsumi , Yin Xiao Hong , Morita Shigenori , Nakanishi Yutaka , Nakagawa Shinichi , Yamamoto Hideo , Watanuki Toshiro , Isa Isao
Published: February 2005

Polypyrrole-polyethylene composites have been prepared by pressing the mixture of polypyrrole coated and non-coated polyethylene spheres. Electrical conductivity is enhanced by more than 16 orders of magnitude and its activation energy decreases remarkably at concentration of polypyrrole coated polyethylene above around 10-20%, which corresponds to effective polypyrrole concentration of 0.1-0.2%. These characteristics can be explained by a percolation model. That is, at this concentration electrodes are bridged by conducting channel of doped polypyrrole. Thermoelectric power increases in proportion to absolute temperature and is independent on concentration of polypyrrole coated polyethylene sphere above 30%, which support the percolation model. The electrical property of this polypyrrole-polyethylene composite is found to be stable up to 160°C. The application of this composite to the semiconducting layer of a cable has been proposed.
Light Emission from Si-Metal-Oxide-Semiconductor Tunnel Junctions
Authors: Watanabe Junichi , Uehara Yoichi , Junichi Murota Junichi Murota , Sukekatsu Ushioda Sukekatsu Ushioda
Published: February 2005

We have observed visible light emission from Si-Metal-Oxide-Semiconductor (MOS) tunnel junctions with a thin oxide barrier (6.6 nm). The junction consists of a phosphorous diffused n-type layer in a p-type Si wafer, a SiO2layer as the tunnel barrier, and an evaporated metal film (Au or Al) as the counter electrode. The current-voltage characteristics of these junctions are well described by the Fowler-Nordheim tunneling theory. The emission spectra are independent of the bias voltage polarity, but depend on the counter electrode material. After examining different possible emission mechanisms, we conclude that the surface plasmon mechanism that is operative in metal-oxide-metal (MOM) light emitting tunnel junctions is the most important process of light emission in the MOS junctions also.
Self-Limited Facet Growth for GaAs Tetrahedral Quantum Dots
Authors: Ando Seigo , Takashi Honda Takashi Honda , Naoki Kobayashi Naoki Kobayashi
Published: February 2005

When metal-organic chemical vapor deposition is used to fabricate GaAs tetrahedral quantum dots by selective epitaxy on triangular windows of (111)B GaAs, there is a condition under which growth automatically stops before the tetrahedral shape is completed. Under a constant growth condition, the size of self-stopped (111)B triangular top facets is extremely uniform and is not influenced by fluctuation of mask window size. Experiments showing that the size of top facet increases with increasing substrate temperature and with decreasing trimethylgallium partial pressure imply that the size is determined by the submicron diffusion length of Ga atoms on (111)B GaAs surface.
Effect of Annealing on Magnetic Properties of Sputtered CoPt Alloy Films
Authors: Shiomi Shigeru , Nakakita Tomoki , Tadashi Kobayashi Tadashi Kobayashi , Morio Masuda Morio Masuda
Published: February 2005

CoPt alloy films with perpendicular magnetic anisotropy were sputtered on Pt buffer layers. In spite of rather large perpendicular anisotropy, the coercivity H
c and squareness ratio S of the perpendicular magnetization curve were very low. It was found that annealing at 300°C in air resulted in a drastic increase in H
c and S, while magnetic moment was reduced. The effect of annealing on magnetic properties was more marked in a thinner film. Auger electron spectroscopy and X-ray photoelectron spectroscopy revealed that cobalt atoms were preferentially oxidized to form CoO during annealing.
Minute Strain Fields due to Vacancy Type Defects in a Rapidly Cooled Czochralski-Grown Silicon Crystal
Authors: Kimura Shigeru , Ono Haruhiko , Ishikawa Taeko Ikarashi
Published: February 2005

The spatial fluctuations of lattice strain in regularly grown and in rapidly cooled Czochralski-grown silicon (CZ Si) wafers were measured by means of plane-wave X-ray topography using highly collimated X-rays with an angular divergence of less than 0.01”. By comparison with the spatial fluctuations of the interstitial oxygen (Oi) concentration measured by means of micro-Fourier transform infrared spectroscopy, we found that the lattice strain of the rapidly cooled wafer was smaller than the strain attributed solely to Oi atoms. This result gave the first clear evidence for the existence of vacancy-type defects in as-grown, rapidly cooled CZ Si crystals.
An ac Bias Readout Scheme for High Tc dc-Superconducting Quantum Interference Devices
Authors: Shinya Kuriki Shinya Kuriki , Daisuke Suzuki Daisuke Suzuki
Published: February 2005

We propose a readout scheme for high-T
c dc-SQUIDs (superconducting quantum interference devices) with alternating current bias and synchronized offset flux. By use of this scheme, low-frequency noise due to critical current fluctuations, which exist in grain boundary junctions, can be canceled. The readout electronics are simple and operation parameters requiring adjustment are minimized. The ac bias scheme has been applied to YBCO step-junction SQUIDs, where partial reduction of the equivalent flux noise below 100 Hz is observed.
Improvement of Gap-Filling Property of O3-tetraethylorthosilicate (TEOS) Film by Ethanol Surface Treatment
Authors: Sato Nobuyoshi , Nakano Tadashi , Hiroshi Yamamoto Hiroshi Yamamoto , Tomohiro Ohta Tomohiro Ohta
Published: February 2005

A new surface treatment involving spin coating of ethanol on substrate prior to O3-tetraethylorthosilicate (TEOS) deposition by atmospheric pressure chemical vapor deposition (APCVD) was found to be very effective for improvement of gap-filling properties and film quality. Deposited film has a “flowlike” surface shape similar to that of spin-on-glass (SOG) film, and can be used to fill trenches of 0.3 µm width and 1.2 µm height (aspect ratio of 4) which could not be filled by a conventional O3-TEOS APCVD. Effects of the surface treatment by some other organic solvents are also reported and a possible mechanism is presented.
Remote Sensing of Induced Electric Current in Melt for Magnetic Czochralski Crystal Growth
Authors: Kasuga Masanobu , Fukai Ikuo , Masaya Amano Masaya Amano , Ken'ichi Kumoyama Ken'ichi Kumoyama
Published: February 2005

A new diagnostic tool for the study of transient and spatial flow patterns of the melt in magnetic Czochralski crystal growth is proposed. The tool is indirect remote sensing of the induced eddy current distribution inside the melt through the measurement of the secondary magnetic field at various points outside the melt. The principle of reconstruction of the electric current in the melt is described. In a simulation experiment using a rotating top as a moving conductor, an appreciable secondary magnetic field was observed and a corresponding eddy current pattern was reconstructed.
Generation and Evaluation of Post-Heated Zinc and Selenium Molecular Beams
Authors: Yoneta Minoru , Ohishi Masakazu , Hiroshi Saito Hiroshi Saito , Tetsuya Hamasaki Tetsuya Hamasaki
Published: February 2005

We report the details of a post-heating cell developed to obtain high-velocity molecular beams. Zn and Se molecular beams generated from this cell are evaluated by measuring deposition rate by means of a quartz thickness monitor. The observed deposition rates are analyzed by means of a simple model for the operation of an ionization gauge. We found that Zn atoms have a thermal velocity determined by the temperature at the post-heating zone, and that Se molecules are thermally cracked.
Growth and Characterization of GaAs/GaSe/Si Heterostructures
Authors: Palmer Joyce E. , Saitoh Tohru , Tokuo Yodo Tokuo Yodo , Masao Tamura Masao Tamura
Published: February 2005

We have grown and characterized epitaxial GaAs grown on layered structure GaSe on As-passivated Si(111) for the purpose of using layered structure GaSe as a lattice mismatch/thermal expansion mismatch buffer layer in the GaAs on Si system. Films were grown on nominally (111) oriented Si substrates by Molecular Beam Epitaxy (MBE) and characterized by in-situ Reflection High Energy Electron Diffraction (RHEED), as well as ex-situ plan-view and cross-sectional Transmission Electron Microscopy (TEM). After GaSe was epitaxially grown at 500°C on As-passivated Si(111) substrates, GaAs growth was carried out at 500°C: As grown GaAs films (300 Å) were highly twinned. In-situ annealing at 650°C for 10 minutes reduced the density of twins as observed by RHEED. In plan-view TEM, Moiré fringes from both GaAs and GaSe are observed and showed conclusively that the GaAs grew epitaxially on the GaSe without contacting the Si substrate. Cross-sectional TEM showed the interface between the Si and GaSe was not smooth on the atomic scale. In spite of this, the GaSe becomes smooth within about 2 monolayers of growth and the GaAs/GaSe interface appeared to be very smooth. Despite the crystalline defects seen in cross section in the GaSe film, the GaAs film grows epitaxially.
Photoassisted Metalorganic Vapor-Phase Epitaxy of Nitrogen-Doped ZnSe Using Tertiarybutylamine as Doping Source
Authors: Fujita Shizuo , Asano Takeharu , Kensaku Maehara Kensaku Maehara , Shigeo Fujita Shigeo Fujita
Published: February 2005

Nitrogen doping into ZnSe was carried out by photoassisted metalorganic vapor-phase epitaxy using diethylzinc and dimethylselenium. Tertiarybutylamine (t-BNH2) was used as a doping source. Photoluminescence, electrical properties of Schottky diodes, and electroluminescence from ZnSe:N/n-ZnSe:Ga diodes revealed acceptor incorporation and p-type behavior in the ZnSe:N layers. Low-temperature (350°C) growth and low irradiation intensity (45 mW/cm2) were found to be desirable for effective doping. As an example, for the ZnSe:N layer with nitrogen concentration of 5×1017 cm-3 revealed by secondary ion mass spectroscopy, net acceptor concentration was estimated to be 2×1017 cm-3 from capacitance measurements of the Schottky diodes as a first approximation.
Measurement and Thermodynamic Analyses of the Dielectric Constant of Epitaxially Grown SrTiO3 Films
Authors: Kazuhide Abe Kazuhide Abe , Shuichi Komatsu Shuichi Komatsu
Published: February 2005

The dielectric constant was measured and analyzed for epitaxially grown SrTiO3 thin films with thicknesses from 23 nm to 92 nm. A stronger applied bias field or a thinner dielectric film caused a decrease in the dielectric constant. Thermodynamic theory was introduced to explain these variations. Good agreement between the experimental results and theoretical calculations led to the conclusion that both the bias field dependence and thickness dependence is an intrinsic nature of SrTiO3 thin film capacitors.
Cathodoluminescence Measurement of Surfaces in Reflection High-Energy Electron Diffraction Experiments
Authors: Michihiro Miyauchi Michihiro Miyauchi , Noriyoshi Shibata Noriyoshi Shibata
Published: February 2005

A new surface analysis system comprising by a reflection high-energy electron diffraction (RHEED) apparatus combined with a cathodoluminescence (CL) detector has been developed. In this method, the luminescence is mainly radiated from the region within a few tens of nanometers below the surface due to the very shallow penetration of the electron beam. This enhancement of surface sensitivity has been demonstrated using bare and Au-coated sapphire (0001) wafers. The CL spectra varied with changing Au thickness on the order of nm, as well as with changing incident angle.
Chemical Treatment Effects of Si Surfaces in NH4OH:H2O2:H2O Solutions Studied by Spectroscopic Ellipsometry
Authors: Sadao Adachi Sadao Adachi , Katsuyuki Utani Katsuyuki Utani
Published: February 2005

Chemically treated Si surfaces in 1NH4OH:XH2O2:5H2O (X=0 and 1) solutions at 80°C have been studied using spectroscopic ellipsometry (SE). The SE data clearly indicate that the X=0 solution results in surface roughening while the X=1 solution, in surface chemical oxidation. It is found that chemical oxidation occurs immediately upon immersing the sample in the X=1 solution. The thickness of the oxide is also found to show a saturated value of ∼11 Å against immersion time t.
Effect of Phosphine on Plasma-Induced Traps in n-InP
Authors: Ninomiya Hideaki , Sugino Takashi , Matsuda Koichiro , Junji Shirafuji Junji Shirafuji
Published: February 2005

Electron traps in n-InP generated by exposure to Ar or phosphine (PH3) plasma have been investigated using isothermal capacitance transient spectroscopy (ICTS). One electron trap (E
c-0.54 eV) is generated by Ar-plasma treatment at 250°C for 60 min. Annealing at 350°C for 3 min after Ar-plasma treatment induces another electron trap (E
c-0.32 eV) together with an increase of the (E
c-0.54 eV) trap density. In contrast to the case of Ar plasma, no traps are detected in InP treated with PH3 plasma consisting of Ar(90%) and PH3(10%) at 250°C for 60 min. Moreover, addition of PH3 to hydrogen (H2) plasma is shown to be effective in suppressing generation of the traps. Generation of these traps does not occur due to annealing after PH3-plasma treatment, while simple annealing of as-etched InP introduces these traps. It is demonstrated that PH3-plasma treatment leads to diffusion of phosphorus atoms during the process and deposition of a thin phosphorus layer at the surface of InP.
A New Drain Engineering Structure-SCD-LDD (Surface Counter Doped LDD) for Improved Hot Carrier Reliability
Authors: Chou Jih Wen , Chang Chun Yun , Ho Lien Tse , Ko Joe , Hsue Peter
Published: February 2005

A new SCD-LDD (Surface Counter Doped LDD) structure is proposed. This structure introduces an additional oblique BF2 implant after nLDD implant, which counter-dopes the nLDD surface concentration near the gate edge. As a result, the lateral electric fields beneath the gate were reduced and the saturation drain current was conducted downward away from the maximum electric fields, resulting in a substantial enhancement of hot carrier reliability due to suppression of hot carrier generation and injection with this structure.
SiO2 Film Growth from ArF Laser Photolysis of Si2H6 and N2O in a Perpendicular Irradiation Configuration
Authors: Tsuji Masaharu , Naoki Itoh Naoki Itoh , Yukio Nishimura Yukio Nishimura
Published: February 2005

Deposition of SiO2 thin films by unfocused ArF excimer laser photolysis of Si2H6/N2O mixtures in a perpendicular configuration has been studied in the low substrate-temperature range of 30-400°C. Thin SiO2 films with a refractive index of 1.46 were deposited on and around the irradiated areas in the substrate-temperature range of 80-400°C and 40-400°C, respectively. The maximum growth rates on and around the irradiated areas were ∼90 and ∼70 Å/min, respectively, at a substrate temperature of 400°C, a laser repetition rate of 50 Hz, a total pressure of 2 Torr, and a N2O/Si2H6 flow ratio of 2000.
Frequency Stabilization of 1.5 µm Diode Laser Using Nonlinear Optical Frequency Conversion in Organic Fiber
Authors: Toda Yasunori , Enami Takashi , Outsu Motoichi
Published: February 2005

Second-harmonic generation using 1.5 µm diode lasers in a nonlinear organic fiber with Cerenkov radiation phase matching is demonstrated for the first time. This second harmonic frequency was locked to the center of the rubidium spectral line to stabilize the fundamental frequency of the 1.56 µm diode laser. The resultant frequency fluctuation, which was evaluated by the error signal from the lock-in amplifier, was maintained at less than 0.3 MHz for one hour.
Evidence of Copious Vacancy Formation in Ni and Pd under a High Hydrogen Pressure
Authors: Yuh Fukai Yuh Fukai , Nobuyuki Ōkuma Nobuyuki Ōkuma
Published: February 2005

From in situ observation of X-ray diffraction of Ni and Pd under a high hydrogen pressure (≃5 GPa) and temperatures (≤800°C), anomalous lattice contraction of the hydride was found to occur in 2∼3 h. This contraction, amounting to ∼0.5 Å3 per a metal atom, remained in the recovered specimen even after the hydrogen was removed by heating to 400°C, but was annealed out at 800°C. The concentration of vacancies responsible for this effect is estimated at ∼20% of metal-atom sites. Anomalous concentration dependence of the hydrogen-induced volume and enhanced diffusion of metal atoms are explained in terms of this effect.
Rhenium Tips for Stable Scanning Tunneling Microscopy
Authors: Miyoko O. Watanabe Miyoko O. Watanabe , Teruyuki Kinno Teruyuki Kinno
Published: February 2005

A rhenium (Re) tip has been investigated for scanning tunneling microscopy (STM). Most of the Re tips etched electrochemically from poly-crystalline wires were found to have a [112̄0]-oriented apex by field ion microscopy. A single atom of the tip apex surface has been expected to be stable, because of its high coordination number. The 7×7 reconstructions of silicon (111) surfaces were observed at atomic level by STM using the Re tip. These results suggest that a Re tip with a single apex atom can be one of the most stable tips for STM.
A High Sensitivity, Phase Sensitive d33 Meter for Complex Piezoelectric Constant Measurement
Authors: Wang Hong , Qiming Zhang Qiming Zhang , Leslie Eric Cross Leslie Eric Cross
Published: February 2005

Based on the direct piezoelectric effect and signal comparison method, a quasi-static, high sensitivity, phase sensitive d
33 meter has been developed. The system is capable of measuring the complex piezoelectric d
33 constant down to about 1 pC/N and has a phase resolution of ±0.05°. The advantage of this apparatus is that its operation is almost as easy as that of the commercial Berlincourt d
33 meter, hence, it is suitable for everyday routine usage.
Carbon Atomic Layer Doping in AlGaAs by Metalorganic Chemical Vapor Deposition and Its Application to a P-Type Modulation Doped Structure
Authors: Toshiki Makimoto Toshiki Makimoto , Naoki Kobayashi Naoki Kobayashi
Published: February 2005

Carbon (C) atomic layer doping in AlGaAs is demonstrated. During undoped AlGaAs growth by conventional low-pressure metalorganic chemical vapor deposition, C atomic layer doping is performed by supplying trimethylgallium onto AlGaAs surfaces under arsine-free conditions. C incorporation increases with increasing Al composition of the surface layer onto which trimethylgallium is supplied, suggesting that the C incorporation mechanism is that As atoms of the AlGaAs surface are partially replaced by C atoms of methyl groups to become acceptors. The capacitance-voltage measurement of the C atomic layer doped AlGaAs shows a carrier profile with a full width at half-maximum as narrow as 8.0 nm at a peak carrier concentration of 2.1×1018 cm-3, indicating that the diffusion of C atoms in AlGaAs is not serious during growth at 610°C. A p-type modulation doped AlGaAs/GaAs structure was fabricated using C atomic layer doping, and a mobility of 1.3×105 cm2/V·s was obtained at 1.5 K for a sheet hole density of 3.9×1011 cm-2. Because of the high quality two-dimensional hole gas, a region limited by acoustic phonon scattering can be seen in the temperature dependence of hole mobility.
Boron Delta-Doped Si- and Ge0.2Si0.8–Channel Metal Semiconductor Field-Effect Transistors Grown by Molecular Beam Epitaxy
Authors: Wang Shui Jinn , San Lein Wu San Lein Wu , Hsiang Dar Chung Hsiang Dar Chung
Published: February 2005

In this paper, we report the realization and the experimental investigations of boron δ-doped Si- and Ge0.2Si0.8-Metal Semiconductor Field-Effect Transistors (MESFET's) grown by molecular beam epitaxy (MBE). Based on Hall measurements, a sheet carrier density of 5×1013 (1.8×1012) cm-2 and a carrier mobility of 34(120) cm2·V-1·s-1 for Ge0.2Si0.8 (Si) δ-doped layer at 300 K were obtained. For the same device structure with an 5 µm Ag gate, the Si- and Ge0.2Si0.8-channel MESFET show an extrinsic transconductance of 0.56 mS/mm and 6.4 mS/mm, respectively. The latter is much larger than that obtained previously in delta-doped Si MOSFETs reported in the literature. As compared to the Si-channel MESFET, the Ge0.2Si0.8 delta-FET (δ-FET) is shown having much smaller leakage current due to the band offset of the Si/Ge0.2Si0.8 heterointerface offering an excellent confinement for channel holes, and much higher transconductance due to the Ge0.2Si0.8 channel promises a higher channel conductivity.
Electrical Characteristics of WO3-Based CO2-Sensitive Solid-State Microsensor
Authors: Shuchi Chao Shuchi Chao
Published: February 2005

A WO3-impregnated thin polymer across two closely spaced microelectrodes is employed as a solid-state CO2 microsensor at 1 atm and room temperature. Its function is based on the WO3 transformation to the conducting HXWO3 by intercalation of released protons from CO2 equilibration in the polymer. The response to CO2 concentrations is reversible and linear between ∼0-16% at ∼840 kΩ per 1% change over prolonged operations of ∼80-second switching time. A dependence on residual water in the polymer is detected but exerts no influence on the CO2 response as long as the polymer is not entirely dried out by H2O-free gas.
Sub-MHz Doppler-Free Spectral Line of 51S0-53P1 Intercombination Transition in Strontium
Authors: Akulshin Alexander , Celicov Alexander , Ohtsu Motoichi , Nakagawa Ken'ichi , Vladimir Velichansky Vladimir Velichansky
Published: February 2005

The saturated absorption resonance of an intercombination transition of 88Sr (λ=689 nm) has been observed using a carefully designed external cavity laser diode and gas cell without buffer gas. A minimum linewidth of 0.7±0.1 MHz has been obtained. The comparison between Sr and Ca reference lines was performed for laser frequency stabilization.
Ingenious Method for Eliminating Effects of Heat Loss in Measurements of Thermal Diffusivity by ac Calorimetric Method
Authors: Gu Yuqin , Tang Xiaowei , Hatta Yuan Xu
Published: February 2005

To eliminate the heat loss effects in thermal diffusivity measurements using the ac calorimetric method, it is proposed theoretically that simultaneous measurement of the effective thermal diffusivities from both the amplitude decay of the ac temperature waves propagating along the surface of a thin sample and its phase shift will solve the problem, i.e., the square root of the product of the two effective thermal diffusivities is equal to the true thermal diffusivity. This is verified experimentally in the measurements for a stainless steel film and a copper film.
Low Diffusivity of Dopants in (111)A GaAs
Authors: Shinoda Akinori , Yamamoto Teiji , Inai Makoto , Toshihiko Takebe Toshihiko Takebe , Toshihide Watanabe Toshihide Watanabe
Published: February 2005

We investigate the evaporation of As atoms from the surface and the diffusion of Si and Be in δ-doped layers, for (111)A and (100) GaAs. As atoms on the (111)A surface do not easily evaporate compared with those on the (100) surface. The diffusion of dopants in (111)A GaAs is smaller than in (100) GaAs, independent of the presence of As vacancies. The diffusion in (100) GaAs, on the contrary, is enhanced by the presence of As vacancies.
Stress in Al-Sc Interconnection Layers
Authors: Hara Tohru , Hosoda Noriko , Nagano Shozo , Ueda Tadao
Published: February 2005

Stress has been measured in Al-Sc layers with different Sc compositions. Stress at room temperature after sintering at 450°C decreases with the increase of Sc concentration and reaches 62 MPa at Sc concentration of 0.3%. This stress level is much lower than of 327 MPa in the Al-1%Si-0.5%Cu layer. The mean time of failure is 6.3×106 h in an Al-0.15%Sc layer. This time is seven times longer than that in the Al-1%Si-0.5%Cu layer. Therefore, Al-Sc is a promising prospect as an interconnection layer for quarter-micron devices.
Effects of Heavily Carbon-Doped Base Layers on Performance of Submicron AlGaAs/GaAs Heterojunction Bipolar Transistors
Authors: Yang L. W. , Wright P. D. , Shen H. , Lu Y. , Brusenback P. R. , Ko S. K. , Calderon L. , Hartzler W. D. , Han W. Y. , Dutta M. , Chang W. H.
Published: February 2005

Submicron heterojunction bipolar transistors (HBTs) with maximum frequency of oscillation, f
MAX, of 91 GHz have been fabricated using a self-aligned technique and a very heavily carbon-doped (1020 cm-3) base layer. Since the quenching of photoluminescence (PL) intensity in heavily-doped GaAs is mainly due to nonradiative recombination in the bulk material, while contribution from surface recombination is negligible, the use of a heavily carbon-doped base layer in AlGaAs/GaAs HBTs minimizes the influence of surface recombination in the extrinsic base region. Thus, for HBTs with a heavily doped base layer, the ”emitter size effect” (degradation of HBT current gain) is greatly reduced when the emitter width is scaled down to submicron (0.6 µm) dimensions.
The Influence of Deposition Process on Polymer Conformation in Langmuir-Blodgett Films
Authors: Zhu Yang-Ming , Zu-Hong Lu Zu-Hong Lu , Yu Wei Yu Wei
Published: February 2005

A lattice model of deposition-induced biased self-avoiding random walk for polymer conformation study is proposed and simulated. Simulation results confirm that the oriented polymer chain direction in Langmuir-Blodgett (LB) films prepared by vertical dipping is caused by deposition process. Thus, the mechanism of liquid crystal alignment on polymer LB films can be deduced.
Ion Collection by Electromagnetic Force
Authors: Murakami Masakatsu , Yutaka Ueshima Yutaka Ueshima , Katsunobu Nishihara Katsunobu Nishihara
Published: February 2005

A new scheme to collect ions is proposed for application to atomic vapor laser isotope separation (AVLIS). A two-dimensional simulation based on the magnetohydrodynamics (MHD) model is presented. It is shown that a dense plasma with density of the order of 1011 cm-3 is efficiently driven by the j×B force within 20-30 µs.
Atomic Force Microscopy and Infrared Spectroscopy Studies of Hydrogen Baked Si Surfaces
Authors: Vatel Olivier , Verhaverbeke Steven , Bender Hugo , Caymax Matty , Chollet Frederic , Vermeire Bert , Mertens Paul , André Elie , Marc Heyns Marc Heyns
Published: February 2005

A H2 pre-bake at temperatures over 1050°C is typically used prior to Si epitaxial growth. In this study surface microroughness probed with tapping mode Atomic Force Microscopy (AFM) is correlated with multiple internal reflection infrared spectroscopy measurements for the different steps involved before epitaxy. A novel sample preparation technique was used for the multiple internal reflection set-up. A strong correlation was found between the presence of surface terraces and the IR double monohydride peaks for H2 annealed Si surfaces. We therefore put forward that the terraces are due to the H2 pre-bake step. These terraces remain after epitaxial deposition.
Low Activation Energy by Polarization in a Floating Gate Structure
Authors: Tamaru Hiroshi Nozawa
Published: February 2005

This paper describes a new and essential mechanism for the low activation energy of charge retention, based on the electrostatic energy change of the floating gate due to a decrease in the stored electrons. The electrostatic potential in the floating gate when a positive space charge is generated at the interface is given by Debye-Hückel. The electron cloud shifts and polarization arises. At this time, a pair consisting of a positive space charge and polarized electron cloud forms an exciton. An electron which forms an exciton recombines with a positive charge by tunneling through SiO2. As a result, the mechanism that an electron is emitted above the work function of 3.2 eV at the Si-SiO2 interface by supplying a thermionic activation energy of 1.2 eV has been revealed.
Self-Excited Potential Oscillation of Lipid across a Micropore Controlled by Hydrostatic Pressure
Authors: Sha Seimei , Takamichi Nakamoto Takamichi Nakamoto , Toyosaka Moriizumi Toyosaka Moriizumi
Published: February 2005

Effects of the hydrostatic pressure difference across the oil to water interface on a self-excited potential oscillation at a micropore have been investigated by potential measurement and microscopic observation. The amplitude and frequency of the oscillation are precisely controlled by means of changing the hydrostatic pressure. This effect of hydrostatic pressure is due to the change in the diameter of a dome that is built at the micropore. These results are qualitatively consistent with our previous ones [Jpn. J. Appl. Phys. 30 (1991) L1435]; i.e., the self-excited potential oscillation can be controlled through changes in the shape or the size of the interface.
491-nm ZnCeSe/ZnSe/ZnMgSSe SCH Laser Diode with a Low Operating Voltage
Authors: Itoh Satoshi , Nakayama Norikazu , Ohata Toyoharu , Ozawa Masafumi , Okuyama Hiroyuki , Nakano Kazushi , Ishibashi Akira , Masao Ikeda Masao Ikeda , Yoshifumi Mori Yoshifumi Mori
Published: February 2005

Room temperature pulsed operation of ZnCdSe/ZnSe/ZnMgSSe separate-confinement heterostructure lasers has been achieved at a wavelength of 491 nm, which is the shortest wavelength at room temperature ever reported. The laser structure was made by molecular beam epitaxy on n-GaAs substrate. The operating current density was 3.8 kA/cm2 for a diode with a 720 µm long and 10 µm wide stripe. An operating voltage of 9 V has been obtained at the threshold current using improved contact layers and ohmic metals.
In Situ Optical Measurement Using Optical Fibers for a-Si:H Ultra-Thin Films: Theoretical and Numerical Analysis
Authors: Leblanc François , Yoshihito Maeda Yoshihito Maeda , Tetsuroh Minemura Tetsuroh Minemura
Published: February 2005

A new in situ optical characterization technique, consisting of measuring the transmittance of a multimode optical fiber when depositing a hydrogenated amorphous silicon (a-Si:H) thin film on the unclad core, is theoretically and numerically analyzed. Due to a large interferential effect, an apparent increase of the optical gap occurs when decreasing the film thickness below 10 nm. The same effect allows the measurement of the absorption coefficient at a given wavelength in the mid-gap region, lower than 5 cm-1 for 20-nm-thick films. The method is a promising tool to investigate the Density of States (DOS) of a-Si:H ultra-thin films.
High-Quality GaAs Films on Si Substrates Grown by Atomic Hydrogen-Assisted Molecular Beam Epitaxy for Solar Cell Applications
Authors: Okada Yoshitaka , Ohta Shigeru , Shimomura Hirofumi , Akio Kawabata Akio Kawabata , Mitsuo Kawabe Mitsuo Kawabe
Published: February 2005

Minority carrier lifetimes of high-quality n-GaAs heteroepitaxial thin films grown on vicinal Si(100) substrates by atomic hydrogen-assisted low-temperature molecular beam epitaxy (MBE) technique have been investigated. Photoluminescence decay characteristics have been evaluated and a minority carrier lifetime of as high as 8.0 ns has been successfully obtained, which is the highest value reported to date. These results are regarded as of particular importance for high-performance optoelectronic device applications especially for tandem solar cells.
Stability of Sputter Deposited ZnO:Cr Films Against Acids
Authors: Shinoda Makoto , Nishide Toshikazu , Sawada Yutaka , Hosaka Masato , Matsumoto Toshihiko
Published: February 2005

ZnO:Cr films were deposited on water-cooled soda-lime glass substrates at room temperature in an Ar atmosphere by rf magnetron sputtering of a ZnO target on which Cr chips were placed. The films exhibited extraordinary stability against acids such as HCl or HNO3, and also high resistivities similar to those of ZnO films. The addition of Cr suppressed the growth of ZnO grains which resulted in the formation of a dense film with a smooth surface. The stability ahd high resistivity displayed by the ZnO:Cr films can be attributed to the formation of a chromium-oxide-rich grain boundary.
Deposition of Calcium Phosphate on Titanium by Electrochemical Process in Simulated Body Fluid
Authors: Maruno Seiji Ban
Published: February 2005

Calcium phosphate coatings were produced by an electrochemical process in a simulated body fluid. Granular precipitates were formed on the working electrode after loading a cathodic potential. The products were amorphous calcium phosphates containing magnesium, of which the composition was nearly the same as calcium-deficient carbonate apatites such as biological apatite. The amount of calcium and magnesium deposited on the electrode increased in direct proportion to the square root of loading time of cathodic potential. The diffusion process of ions around the cathode was found to be a rate-determining step in the electrochemical process of forming calcium phosphate.
Transverse-Mode Characteristics of InGaAs/GaAs Vertical-Cavity Surface-Emitting Lasers Considering Gain Offset
Authors: Kaneko Yasuhisa , Tamanuki Takemasa , Katoh Masao , Maekawa Hiroaki , Fumio Koyama Fumio Koyama , Kenichi Iga Kenichi Iga
Published: February 2005

We have fabricated InGaAs/GaAs vertical-cavity surface-emitting lasers with modulation-doped graded distributed Bragg reflectors (DBRs) grown by metal-organic chemical vapor deposition (MOCVD). The threshold current was 3.2 mA. By observing the spontaneous emission through DBRs, we found that transverse mode behavior depends on gain characteristics. Single fundamental transverse-mode lasing is achieved at a negative gain offset and multiple transverse-mode lasing is achieved at a positive gain offset.
In-Diffusion and Isothermal Annealing of Iron-Related Defects in n-Type Silicon
Authors: Kitagawa Hajime , Shuji Tanaka Shuji Tanaka , Baorong Ni Baorong Ni
Published: February 2005

In iron-related deep levels in n-type silicon, the introduced concentration of E
c-0.21 eV(B) and E
c-0.41 eV(C) levels decrease with increasing the diffusion time at 1160°C, indicating that the formation process includes the conversion process into other types of complexes. The concentration of the C level decays exponentially with the duration of isothermal annealing up to 200°C, the time constant activation energy being 0.65 eV. The results indicate that the observed defects are due to the intermediate states in consecutive reactions of iron-related complex formation.
Preparation of (Bi, Pb)-Sr-Ca-Cu-O Superconducting Thin Films by the Mist Microwave-Plasma Chemical Vapor Deposition Method
Authors: Takahashi Naoyuki , Kanematsu Daigorou , Koukitu Akinori , Kamioka Hisashi Seki
Published: February 2005

Superconducting thin films of (Bi, Pb)-Sr-Ca-Cu-O were prepared on single-crystal MgO(100) substrates by the mist microwave-plasma chemical vapor deposition method. The prepared films constituted of the 2212 and 2201 phases with c-axis orientation perpendicular to the substrates. The dependence of critical temperature of films on the input mole ratio of oxygen OR=FO2
/(FO2
+total FAr) was investigated. The maximum critical temperature (78 K) of as-deposited films was obtained at the input molar ratio of oxygen about of 0.60 and the microwave power of 300 W.
Fluctuation-Free Electron Emission from Non-Formed Metal-Insulator-Metal (MIM) Cathodes Fabricated by Low Current Anodic Oxidation
Authors: Kusunoki Toshiaki , Suzuki Mutsumi , Sasaki Susumu , Tomio Yaguchi Tomio Yaguchi , Toshiyuki Aida Toshiyuki Aida
Published: February 2005

Fluctuation-free electron emission is obtained from MIM (Al-Al2O3-Au) cathodes. The Al2O3 layer is fabricated by anodic oxidation with a reduced electrolysis current density, i.e., a reduced oxidation rate. The slow oxidation process improves the insulating effect of the Al2O3 layer, and enables the MIM cathodes to operate in the non-formed state. The fluctuation-free emission is reproducible when the diode voltage is cut off instantaneously. With a thin Al2O3 layer, the diode voltage reguired for the cathode operation is reduced to values slightly above the work function of the top electrode.
Carbon-Induced Rapid Annihilation of Thermal Double Donors in Czochralski Silicon Studied by Infrared Absorption Spectroscopy
Authors: Kamiura Yoichi , Yutaka Uno Yutaka Uno , Fumio Hashimoto Fumio Hashimoto
Published: February 2005

Carbon-rich Czochralski Si shows anomalously rapid annihilation for all the species of thermal double donors at 470°C in two stages, which have good time correlations with the decrease of substitutional carbon density and also with the formation of two kinds of carbon-related new donors which were previously found. The hypothesis is proposed that Si self-interstitials created during the oxygen aggregation process eject substitutional carbon into an interstitial site, and this interstitial carbon rapidly diffuses to thermal double donors to aggregate with them so as to form electrically inactive clusters which act as the embryos of the carbon-related new donors.
Structure of Chemical Vapor Deposited Diamond (111) Surfaces by Scanning Tunneling Microscopy
Authors: Hidehiro Sasaki Hidehiro Sasaki , Hiroshi Kawarada Hiroshi Kawarada
Published: February 2005

Scanning tunneling microscopy (STM) has been employed in the observations of chemical vapor deposited (CVD) homoepitaxial diamond (111) surfaces. The surfaces are composed of an H-terminated 1×1 structure. Single-atom height steps on the surfaces are observed to be very straight and form a downward slope in the [112̄] direction. Some adsorbates different from the H-terminated monohydride structure have been found on each terrace. We speculate that these adsorbates are CH3.
Dependence of ErAs Clustering and Er Segregation in ErAs/GaAs Heterostructures on Growth Temperature
Authors: Jourdan Nicolas , Hiroshi Yamaguchi Hiroshi Yamaguchi , Yoshiji Horikoshi Yoshiji Horikoshi
Published: February 2005

The effect of growth temperature on the growth properties of ErAs/GaAs heterostructures grown by low-temperature migration-enhanced epitaxy and molecular beam epitaxy is investigated in detail using transmission electron microscopy, double-crystal X-ray diffraction and secondary ion mass spectroscopy. Our results demonstrate that the formation of ErAs clusters at the ErAs/GaAs interface occurs even at very low growth temperatures (320°C). Moreover, we clearly observe that the size of the clusters drastically increases and Er segregation takes place when the growth temperature is increased. All our characterization results suggest that when the samples are grown by migration-enhanced epitaxy at 320°C, these problems can be limited, leading to an enhancement of crystal quality.