bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of Adsorption and Thermal Desorption of Atomic Hydrogen on Electronic and Atomic Structures of Si(111)(√3×√3)-Al Surface
Authors: Li Sung-Te , Hasegawa Shigehiko , Nakashima Hisao
Published: February 2005

The adsorption and thermal desorption of atomic hydrogen induce electronic and atomic structural changes on the Si(111)(√3×√3)-Al surface. These changes have been studied using low-energy electron diffraction (LEED), Auger electron spectroscopy (AES), and angle-resolved electron-energy-loss spectroscopy (AR-EELS). Upon exposure to atomic hydrogen, the (√3×√3) surface structure changes into a hydrogen-induced (1×1) in the LEED pattern. Simultaneously, the characteristic loss peaks of the Si(√3×√3)-Al surface completely disappear and a new loss peak appears at 8 eV. We ascribe this new peak to a Si-H bonding state. After thermal desorption of atomic hydrogen, a (√3×√3) LEED pattern reappears and a new loss peak emerges at 1.5 eV. The Al-LVV Auger peak is observed on the Si(√3×√3)-Al surface, but not on this hydrogen-desorbed surface. The new loss peak at 1.5 eV is ascribed to the transition due to the Si-adatom-induced surface state. The reappeared (√3×√3) surface structure is proposed to be induced by the Si adatoms substituting for Al in the T4 adatom geometry.
Introduction of Dislocation into YBa2Cu3O7-δ and Effect on Jc Characteristics
Authors: Zheng Xuguang , Kuriyaki Hisao , Hirakawa Kazuyoshi , Tanaka Eishi , Tomokiyo Yoshitsugu
Published: February 2005

Dislocations accompanied by stacking faults are found in intragrain regions of polycrystalline YBa2Cu3O7-δ which is prepared by a solid-state reaction process. The process is characterized by the inclusion of high-temperature sintering. Transport critical current density J
c is measured in a liquid nitrogen bath at magnetic fields H up to 1.5 T. J
c at H>0.3 T hardly deteriorates, producing a nearly flat J
c-H characteristic at high fields. The result shows that the dislocations probably act as pinning centers for magnetic flux.
Giant Magnetoresistance in Antiferromagnetic Co/Cu Multilayers Grown on Kapton
Authors: Parkin S. S. P. , K. P. Roche K. P. Roche , Takao Suzuki Takao Suzuki
Published: February 2005

Multilayers of Co/Cu, sputter deposited onto thin kapton films, display very large room-temperature magnetoresistance, almost as large as that found in similar structures prepared on silicon wafers. Such flexible structures suggest a number of intriguing technological applications. Plane-view and cross section transmission electron micrographs reveal a high degree of structural order with grains extending over several hundred angstrom with sharp grain boundaries.
Whiskerizing on Carbon Fibers by Heating with a Carbon Dioxide Laser
Authors: Okada Yoshiki , Takeuchi Kazuo , Yamanashi Hidenori , Ushijima Hitoshi
Published: February 2005

Using a continuous wave CO2 laser, whiskerizing on the surface of carbon fibers was achieved by the catalytic pyrolysis of allene (C3H4). As a catalyst, iron particles generated by laser-induced thermal decomposition of pentacarbonyliron (Fe(CO)5) or ferrocene ((C5H5)2Fe) were used. The whiskers grown on the surface of the carbon fibers were found to have disordered carbon structures, as determined by Raman spectroscopic measurement.
Decomposition Process of Alane and Gallane Compounds in Metal-Organic Chemical Vapor Deposition Studied by Surface Photo-Absorption
Authors: Yoshiharu Yamauchi Yoshiharu Yamauchi , Naoki Kobayashi Naoki Kobayashi
Published: February 2005

We used surface photo-absorption (SPA) to study trimethylamine alane (TMAA) and dimethylamine gallane (DMAG) decomposition processes on a substrate surface in metal-organic chemical vapor deposition. The decomposition onset temperatures of these group III hydride sources correspond to the substrate temperature at which the SPA reflectivity starts to increase during the supply of the group III source onto a group V stabilized surface. It was found that TMAA and DMAG start to decompose at about 150°C on an As-stabilized surface, which is much lower than the decomposition onsets of trialkyl Al and Ga compounds. Low temperature photoluminescence spectra exhibit dominant excitionic emissions for GaAs layers grown by DMAG at substrate temperatures above 400°C, indicating that carbon incorporation and the crystal quality deterioration due to incomplete decomposition on surface is much suppressed by using DMAG. A comparison of AlGaAs photoluminescence between layers by TMAA/triethylgallium and triethylaluminum/triethylgallium shows that the band-to-carbon acceptor transition is greatly reduced by using TMAA. TMAA and DMAG were verified to be promising group III sources for low-temperature and high-purity growth with low-carbon incorporation.
Defect Formation Process during Growth of Hydrogenated Amorphous Silicon at High Temperatures
Authors: Gautam Ganguly Gautam Ganguly , Akihisa Matsuda Akihisa Matsuda
Published: February 2005

The deposition rate dependence of the defect density at elevated substrate temperatures during the preparation of hydrogenated amorphous silicon reveals the importance of reactions of precursors on the growth surface. The concept of precursor assisted defect suppression is delineated and used to prepare materials with defect densities that are significantly lower than those available at present.
Periodic Step and Terrace Formation on Si(100) Surface during Si Epitaxial Growth by Atmospheric Chemical Vapor Deposition
Authors: Izunome Koji , Saito Yoshihiko , Kubota Hiroyasu
Published: February 2005

The surface structure of Si epitaxial film growth achieved by atmospheric chemical vapor deposition on Si(100) with a misorientation is studied by angle-resolved light scattering (ARLS) and atomic force microscopy (AFM). The Si epitaxial surface has a periodic structure consisting of terraces and atomic-steps. The terrace length depends on the substrate misorientation. The step height is independent of the substrate misorientation, and is about 0.3 nm, which corresponds to the double-layer step. The periodic structure is formed during the atmospheric growth process.
Superconductivity in the Gd2-x-yLaxCeyCuOz System
Authors: Sasakura Hiroyuki , Akagi Yoshiya , Yamaguchi Yasuo , Minamigawa Shinnosuke , Inoue Kazuo , Noguchi Satoru , Okuda Kiichi
Published: February 2005

We report the observation of superconductivity for samples with T
′ phase structure in the Gd2-x-y
La
x
Ce
y
CuO
z
system. The samples exhibiting superconductivity lie in a limited composition range. Among them, the sample with the composition of Gd0.72La1.15Ce0.13CuO
z
showed the maximum superconducting onset temperature of about 12 K and the maximum zero resistivity temperature of 6.5 K. The sample was of a single T
′ phase with the lattice parameters of a=0.3969 nm and c=1.220 nm by X-ray diffraction analysis.
Electron Spin Resonance (ESR) Signals in Natural and Synthetic Gypsum: An Application of ESR to the Age Estimation of Gypsum Precipitates from the San Andreas Fault
Authors: Sumiko Ikeda Sumiko Ikeda , Motoji Ikeya Motoji Ikeya
Published: February 2005

Radiation-induced defects in natural and gamma-ray-irradiated synthetic gypsums (CaSO4·2H2O) were investigated by electron spin resonance (ESR). The study on the impurity-doped synthetic gypsum revealed that the ESR signal at g
⊥=2.008 and g
//=2.019 is enhanced by the presence of CO3
2- and Ba2+ impurities. A new method for the age estimation of fault displacement using an ESR signal intensity of gypsum precipitates was proposed and applied to the San Andreas fault.
Excitonic Photon Absorption-Emission Characteristics in ZnCdSe-ZnSe Single-Quantum-Well Structures
Authors: Ando Koshi , Akira Ohki Akira Ohki , Sakae Zembutsu Sakae Zembutsu
Published: February 2005

Excitonic photon absorption and emission processes are investigated under zero or external electric fields on MOVPE grown (Zn1-x
Cd
x
)Se-ZnSe:x=0.18 single quantum wells (SQWs). The effects of a dc electric field applied perpendicularly on absorption and emission processes are examined by electric field-controlled photoluminescence (PL), electroreflectance (ER) and photocurrent (PC) spectrum measurements. The characteristics of optically excited spontaneous and stimulated emissions from the SQWs are different in both spectrum peak energies and field effects from those expected in the heavy hole mass (H-H) exciton ground state (n=1) in quantum wells.
Electroluminescent Devices with (Y2O2S:Tb/ZnS)n Multilayered Phosphor Thin Films Prepared by Multisource Deposition
Authors: Ohmi Koutoku , Tanaka Shosaku , Nire Hiroshi Kobayashi
Published: February 2005

An (Y2O2S:Tb/ZnS)
n
multilayered thin-film electroluminescence (TFEL) device has been fabricated by the multisource deposition method. The multilayered TFEL device has shown a maximum luminance of 124 cd/m2 at 5 kHz. It is also seen that the EL characteristics strongly depend on the structure of phosphor layers, and the TFEL device with the Y2O2S:Tb single layer showed nominal EL emission. The excitation mechanism of the (Y2O2S:Tb/ZnS)
n
multilayered TFEL devices is discussed.
Polarization of Stimulated Emission due to the Magnetoelectric-Photo Effect of InSb at the Quantum Limit
Authors: Morimoto Takeshi , Meiro Chiba Meiro Chiba , Shizumasa Ueda Shizumasa Ueda
Published: February 2005

Polarization characteristics have been examined for the stimulated Landau emission from a bulk InSb at 80 K in a quantizing magnetic field of H=6 T in the Voigt configuration, in which excess electrons and holes are excited by passing a current J perpendicular to H through the J×H force excitation. The results indicate that the extraordinary mode (E
rf⊥H) of the emission, which obeys the selection rule ΔM=±1 on the magnetic quantum number M, is the favorable one to undergo selective amplification in the sample at the quantum limit.
Infrared Polarized Reflection Spectra of SrTiO3 Thin Films on Metal/Si
Authors: Myoren Hiroaki , Takeshi Matsumoto Takeshi Matsumoto , Yukio Osaka Yukio Osaka
Published: February 2005

The dielectric properties in the infrared region of SrTiO3 thin film on Pd/Si were studied using reflectance spectra of radiation polarized parallel to the incident plane. The absorption bands of LO (optical phonon) modes increase linearly with increasing incident angle. Maximum sensitivity can be obtained using an incident angle of about 60∼85°. There is sufficient sensitivity at the film thickness of less than 10 nm. These results suggest that p-polarized reflection spectroscopy is a promising technique for estimating dielectric properties for very thin SrTiO3 films on metal/Si.
Comparison of Photoluminescence Lifetimes between As-Prepared and Dry-Oxidized Porous Si
Authors: Yamada Masao , Akira Takazawa Akira Takazawa , Tetsuro Tamura Tetsuro Tamura
Published: February 2005

The photoluminescence decay of both as-prepared and dry-oxidized porous Si excited by a nitrogen laser pulse is not exponential, but is fitted well by two exponential decays with lifetimes ranging from a few nanoseconds to over 100 nanoseconds. Further, those lifetimes do not change with changing excitation power by more than three orders of magnitude. The lifetime of dry-oxidized porous Si is longer than that of as-prepared porous Si. These studies would suggest that the photoluminescence mechanism is basically the same for both as-prepared and dry-oxidized porous Si, and the radiative recombination path is through some luminescence centers lying in the widened band gap owing to quantum size effects.
Fabrication of a Bi-2212/Ag Pancake Coil Generating 6000 G at 4.2 K in 12 T
Authors: Shimoyama Jun-ichi , Morimoto Takeshi , Kitaguchi Hitoshi , Kumakura Hiroaki , Togano Kazumasa , Maeda Hiroshi , Nomura Katsumi , Seido Masahiro
Published: February 2005

A Bi2Sr2CaCu2O
y
(Bi-2212)/Ag single pancake coil with dimensions of 45 mmφ(outer)/13 mmφ(inner)×20 mm was fabricated by the wind, react and wind (W & R & W) method. The critical current of the coil was 230 A at 4.2 K in 12 T assuming the criterion as 10-13 Ω·m. At this moment, a generated field of 6000 G was detected at the center position of the coil by the Hall probe measurement.
Low-Temperature Annealing Effect on Superconducting and Structural Properties of Ion-Irradiated Bi2Sr2CaCu2OxCrystals
Authors: Chenevier Bernard , Kumakura Hiroaki , Ikeda Shozo , Togano Kazumasa , Okayasu Satoru , Kazumata Yukio
Published: February 2005

Samples of a highly textured 15 µm-thick Bi2Sr2CaCu2Oxpolycrystalline layer have been irradiated with 180 MeV Cu11+ions perpendicularly to the surface of the layer. Upon irradiation the intragrainJcvalues of the superconducting material are increased but the critical temperatureTcvalues are depressed. To investigate the influence of stress induced on the crystal structure by irradiation defects, annealing of the irradiated samples at 573 K for 12 hours has been performed. After annealing, a partial recovery of theTcandJcvalues of unirradiated samples is obtained. Residual defects have been observed by high-resolution electron microscopy. It is shown that the amorphous material found in the columnar defects before annealing has partially recrystallized.
Proposal of Integrated Light Emitting Device Array with Shift Register
Authors: Komaba Nobuyuki , Ohno Seiji , Kusuda Yukihisa , Kuroda Yasunao , Ken Yamashita Ken Yamashita , Shuhei Tanaka Shuhei Tanaka
Published: February 2005

We propose two types of new integrated light-emitting device arrays with a shift register for the photo-printer head. The proposed device arrays consist of a self-scanning light-emitting device (SLED) as a shift register and light-emitting thyristors for printing. One of the proposed device arrays, which has 12 bits and a 62.5-µm-pitch thyristor array, was fabricated and demonstrated. It has a wide operating margin of about 2 V, and has a maximum transfer frequency of 10 MHz.
Cathodoluminescence from Porous Silicon
Authors: Pillai S. M. , Xu Z. Y. , Gal M. , Glaisher R. , Phillips M. , Cockayne D.
Published: February 2005

Spatially resolved cathodoluminescence (CL) spectra were measured on porous silicon. The CL spectra showed bands and prominent peaks ranging in energy between 1.45 eV and 3 eV and were unlike the photoluminescence spectra measured on the same samples, which consisted of the well known single, broad band peaking in the visible or near infrared region. Two possible models are discussed to explain these observations.
InP/InAlAs Resonant Tunneling Diodes Grown by Gas Source Molecular Beam Epitaxy
Authors: Yuichi Kawamura Yuichi Kawamura , Hidetoshi Iwamura Hidetoshi Iwamura
Published: February 2005

An InP/InAlAs double-barrier resonant tunneling diode (DB-RTD) is grown by gas source molecular beam epitaxy for the first time. It shows clear negative differential resistance (NDR) at 77 K, and the NDR peak current density agrees well with the value calculated using the conduction band offset (0.35 eV), which is determined from the intersubband absorption measurement. A pseudomorphic InP/AlAs DB-RTD is also fabricated, which shows clear NDR at room temperature.
Low-Threshold GaInAsP/InP Transmission-Type Surface Emitting Laser
Authors: Kubota Shinichi , Fumio Koyama Fumio Koyama , Kenichi Iga Kenichi Iga
Published: February 2005

A transmission-type 1.3-µm GaInAsP/InP surface emitting (SE) laser has been demonstrated for new application of SE lasers. A threshold current density as low as 530 A/cm2 (I
th=2.8 mA) was obtained under the 77 K cw condition. This is the lowest value of 1.3-µm surface emitting lasers ever reported. Some detailed spectral characteristics near the threshold have been measured and the possibility of narrow-band active vertical-cavity filters is suggested.
Microscopic IR-Reflection Study of Oxygen Doping Effect Induced by Laser Irradiation on YBa2Cu3Oy Surface
Authors: Kawabata Keisuke , Tsukui Shigeki , Yamamoto Takao , Imamura Shinichirou , Nagayama Masanori , Hayashi Yoshikazu
Published: February 2005

A study of reflection Fourier Transform IR (FTIR) microscopic analysis with the probe area of 0.1×0.1 mm was conducted on a polycrystalline YBa2Cu3O
y
pellet irradiated with 1060 nm laser light. The presence of a large increase of the broad IR band accompanied by the simultaneous disappearance of the 590 cm-1 phonon band in the CuO2 plane, was found on an insulator sample irradiated in an atmosphere of 650 Torr oxygen gas, but not on a sample in 650 Torr Ar. This suggests that oxygen doping into YBa2Cu3O
y
occurs due to the laser irradiation to result in the increase of charge carriers in the CuO2 plane. A small increase in a narrower IR band showing a peak around 1000 cm-1, and considered to originate from the direct photoexcitation was also found in both of the samples.
Ferromagnetic Resonance in Superlattices Fe/Cr on MgO
Authors: Araki Osamu Kohmoto
Published: February 2005

Measurements of ferromagnetic resonance (FMR), magnetization and magnetoresistance (Δρ/ρ) have been made for Fe(30 Å)/Cr(x) superlattices epitaxially deposited on MgO(001) substrates, to study the antiferromagnetic (AF) coupling between the adjacent Fe layers. For x=6-12 Å films, a large Δρ/ρ (>5%), high saturation field (H
s) and two FMR peaks were observed. A model of strongly coupled AF magnetization explains the high H
s; however, it cannot explain the observed low field values of the secondary FMR peak.
Anchoring Structure of Binary Mixture of Liquid Crystals Studied by Scanning Tunneling Microscopy
Authors: Iwakabe Yasushi , Hara Masahiko , Kondo Katumi , Oh-Hara Syuichi , Sasabe Akio Mukoh
Published: February 2005

The anchoring structures of the binary mixture of 4′-n-octyl-4-cyanobiphenyl (8CB) and 4′-n-decyl-4-cyanobiphenyl (12CB) on molybdenum disulfide (MoS2) are directly observed, with molecular resolution, by scanning tunneling microscopy (STM) for the first time. The STM images indicate that the technique not only resolves the individual molecules, but it also makes a clear distinction between the 8CB and 12CB molecules by their different alkyl chain lengths. The binary mixture takes a bilayer (double-row) structure, consisting of an 8CB subunit and a 12CB subunit, while the pure 8CB molecules do not show a bilayer, but a monolayer (single-row) structure on MoS2. The ratio of 8CB and 12CB adsorbed on MoS2 substrate is different from that in the bulk.
The Effect of Electrochemical Reduction and UV Exposure in H2S Gas on Interface Properties of ZnS/p-Hg1-xCdxTe
Authors: Jeong Jae-Hong , Hee-Chul Lee Hee-Chul Lee , Choong-Ki Kim Choong-Ki Kim
Published: February 2005

A novel surface treatment method for obtaining high quality ZnS/Hg1-x
Cd
x
Te interface is proposed. The treatment procedure includes bromine-methanol etching, electrochemical reduction in an acetate buffer solution, and UV exposure in H2S gas ambient inside a vacuum chamber. After the surface treatment is performed, 4500 Å-thick ZnS film is in situ evaporated on the Hg1-x
Cd
x
Te surface in the same chamber used for the UV treatment without exposing the surface to atmosphere. The interface properties estimated from MIS capacitors show the positive fixed interface charge density of 3×1010 cm-2 and the insulator trap charge density of 1.8×1010 cm-2. The interface trap density is lower than 1012 cm-2·eV-1 over most of the bandgap and the minimum interface trap density is 4.5×1010 cm-2·eV-1 near the middle of the bandgap. The effect of each step of the surface treatment procedure is also investigated by MIS capacitors. All steps seem to be significant.
High Resolution Z-Contrast Observation of GaAs/Si Hetero-Interfaces through Scanning Transmission Electron Microscope
Authors: Takasuka Eiryo , Asai Koyu , Fujita Kazuhisa , Chisholm Matthew F. , Pennycook Stephen J.
Published: February 2005

Interfaces of GaAs/Si(100) grown by molecular beam epitaxy were observed through high resolution Z-contrast imaging in a scanning transmission electron microscope. Such images can be interpreted directly, and provide atomic-scale structural and compositional information. Regions of the interface were observed to be faceted on a fine scale with microtwins often threading from these regions into the film. Low-temperature grown buffer layers were found to be very effective for the suppression of defects grown in the epitaxial layer, even in the presence of the interfacial roughness. This suggests that the threading defects are due to the initial three dimensional growth mode and also due to substrate surface contamination. Interfacial misfit dislocations are clearly found to be located in the GaAs film about 5 Å from the interface. The incoherent images combined with compositional contrast provides much improved atomic-scale characterizations of the hetero-structure.
Origin of External Influences of Domain Stability on Si(100)
Authors: Takaaki Kawamura Takaaki Kawamura , Mark Wilby Mark Wilby
Published: February 2005

In this paper we propose a new mechanism for the induced domain changes on a well orientated Si(100) surface by means of a direct current or applied strain. The process is demonstrated by means of Monte Carlo simulation, where large scale domain changes are observed over long periods of time. The essential element is a small domain dependent perturbation of the surface bonding energy.
Electrical and Magnetic Properties of the High-Tc Superconductors (Y1-xMx)Ba2Cu3Oy and Y(Ba1-xMx)2Cu3Oy (M=Mg, Ca, Sr, Ba)
Authors: Tatsumi Yukichi , Kebukawa Takeji , Fujiwara Yutaka Misawa
Published: February 2005

The superconducting state of YBa2Cu3O
y
substituted at the II a group was investigated by X-ray powder diffraction, iodometric titration, electrical resistivity and magnetization measurements. The T
c is shifted to low temperature by the substitution of Y or Ba from a heavy atom to light atom at x=0.1, and depends on the ionic radius. In the results obtained from the magnetic hysteresis loop, it is interesting that in the case of the substitution of Ca for x=0.1, the magnetization for Y is larger than that for Ba with decreasing temperature, and the magnetization in the case of Ba for Y is rapidly lowered at x=0.1.
Deposition of Aluminum Nitride by Remote Plasma-Enhanced Chemical Vapor Deposition Using Triisobutyle Aluminum
Authors: Matsumoto Akinori , Meikle Scott , Yoichiro Nakanishi Yoichiro Nakanishi , Yoshinori Hatanaka Yoshinori Hatanaka
Published: February 2005

Aluminum nitride thin-film deposition resulting from addition of triisobutyle aluminum (TIBA) to the afterglow of an N2 microwave plasma has been investigated. Chemiluminescence spectra of the downstream reaction indicated that the substrate temperature is one parameter for the decomposition of TIBA. The activation energy for plasma-assisted TIBA decomposition is also evaluated by the chemiluminescence spectra and found to be about 14.8 kJ/mol.
Estimation of Centrifugal-Force Effect on Resist Coat around Wafer Edges
Authors: Shigeki Matsutani Shigeki Matsutani , Shigeyuki Uzawa Shigeyuki Uzawa
Published: February 2005

In exposure equipment for production of semiconductor devices or steppers, the accuracy of the alignment between the mask and wafers is one of the most important factors. Since optical information is used in most methods for measurement of the alignment, there remain some intrinsic errors. For example, since a photosensitive resist is spin-coated, its thickness is not constant due to the centrifugal-force effect, and this variation causes an optical distortion. In this letter, we give an analytical estimation of the centrifugal-force effect on the resist surface profile around wafer edges. We show that due to this effect for a concave wafer pattern, the resist surface has an asymmetrical form proportional to βx
3 where β>0 and x is a position, whereas for a convex pattern it is proportional to -βx
3.
Ion Beam Analysis of ZnSe
Authors: Sasaki Yuichi , Yoshida Kenichiro , Nishiyama Fumitaka , Yao Takafumi , Zhu Ziqiang , Mori Hiroshi , Kawashima Mitsuo
Published: February 2005

The Rutherford Backscattering Spectroscopy (RBS) spectra of Li-doped ZnSe ([Li]≥1018 cm-3) are measured with a He+ ion beam at 2.0 MeV. The backscattering yield for aligned incidence increases with increases in Li concentration. Nuclear reaction analysis of 7Li(p, n)7Be is performed. The angular dependence of the neutron yield around <100> and <110> incidence directions suggests that the lattice site of Li is displaced from the ordinary lattice sites of the ZnSe lattice.
Magnetic Shielding Property of Bi(Pb)-Sr-Ca-Cu-O Superconducting Tube
Authors: Tsukamoto Keizou , Ishii Mamoru , Shimojima Hiromasa , Yamagishi Chitake , Takata Masasuke , Yamashita Tsutomu
Published: February 2005

The magnetic shielding property of a Bi(Pb)-Sr-Ca-Cu-O superconducting tube was examined. The measured internal magnetic flux density of the tube, as a function of the applied magnetic field, agreed with the critical state model calculated with the consideration of the hysteresis of the critical current density on the magnetic field.
Low-Temperature119Sn-Mössbauer Study of Superconducting Bi4Sr3.5Ca2.5Cu4Sn0.015O16-yCeramic (2212 Phase)
Authors: Nishida Tetsuaki , Katada Motomi , Miura Norio , Deshimaru Yuichi , Yamazoe Noboru , Matsumoto Yasukuni , Yoshimasa Takashima Yoshimasa Takashima
Published: February 2005

The119Sn-Mössbauer spectra of superconducting Bi4Sr3.5Ca2.5Cu4Sn0.015O16-yceramic (2212 phase,Tc: 77 K), measured between 298 K and 7 K, consist of singlet peaks of Sn4+with the δ′s and Γ′s of -0.01-0.07 and 1.05-1.27 mm·s-1, respectively. The lnA(absorption area)-vs-Tplot shows that the recoil-free fractionfincreases with decreasing temperature, and that the Debye and Einstein temperatures are 340 and 185 K, respectively. The ΘDof 340 K suggests that the Sn4+is in the BiO5pyramids. The lnAshows a “normal” lattice vibration probably because of the long Cu-O(3) distance and the displacement of O(3).
High Jc Y-Ba-Cu-O Thin Film on Metal Substrates Prepared by Chemical Vapor Deposition
Authors: Aoki Shin-ya , Yamaguchi Taichi , Iijima Yasuhiro , Kagawa Akira , Kohno Osamu , Nagaya Shigeo , Inoue Toshio
Published: February 2005

High J
c superconducting Y-Ba-Cu-O (YBCO) thin films were prepared on metal substrates at 700°C under low oxygen partial pressure by chemical vapor deposition (CVD). Two kinds of substrates were used. One is a polycrystalline Hi-based alloy (Hastelloy C-276) with YSZ and Ag buffers, and another is the same alloy with a biaxially aligned YSZ(100) buffer. The biaxially aligned YSZ(100) buffer layer was formed by ion-beam-assisted deposition (IBAD). According to X-ray diffraction (XRD) analysis, these films were c-axis oriented. The YBCO film on Hastelloy C-276 with YSZ and Ag buffers had a critical temperature (Tc) with zero resistivity at 84.5 K and a critical current density (J
c) of 5.7×103 A/cm2 (77.3 K, 0 T). YBCO film on Hastelloy C-276 with a biaxially aligned YSZ(100) buffer had a T
c at 87.5 K and J
c of 7.1×104 A/cm2 (77.3 K, 0 T) and 3.0×103 A/cm2 (77.3 K, 7 T).
Time-Resolved Pulse Response of Electroluminescence in Poly(3-alkylthiophene) Diodes
Authors: Ohmori Yutaka , Morishima Chikayoshi , Masao Uchida Masao Uchida , Katsumi Yoshino Katsumi Yoshino
Published: February 2005

Pulse response of electroluminescence in poly(3-alkylthiophene) diodes has been investigated. The response consists of two independent parts, that is, fast and slow transition parts. The fast response corresponds to carrier transit between electrodes. On the other hand, the anomalous slow response which becomes marked at higher current is explained by the temperature change of the diode junction. Carrier mobility of the poly(3-alkylthiophene) has been estimated from the fast part, which coincides with that evaluated from the characteristics of poly(3-alkylthiophene) field-effect transistors. Temperature dependence of the electroluminescence intensity in poly(3-alkylthiophene) diode has been discussed.
Dielectric Properties of Perovskite Lead Indium Niobate and Tantalate Prepared by Fast Firing Technique
Authors: Yasuda Naohiko , Hiroshi Inagaki Hiroshi Inagaki , Susumu Imamura Susumu Imamura
Published: February 2005

Perovskite Pb(In1/2Nb1/2)O3 and Pb(In1/2Ta1/2)O3 compounds were successfully prepared with the aid of wolframite phase oxide, utilizing a fast firing technique. Dielectric properties of Pb(In1/2Nb1/2)O3 and Pb(In1/2Ta1/2)O3 compounds prepared by such a technique were found to be typical of ferroelectric relaxors exhibiting a broad maximum of permittivity and a strong dielectric dispersion.
Effect of Starting Oxide on Electrical Characteristics of Metal-Reoxidized Nitrided Oxide-Semiconductor Devices Prepared by Rapid Thermal Processes
Authors: Kuei-Shu Kuei-Shu , Chang-Liao Chang-Liao , Jenn-Gwo Hwu Jenn-Gwo Hwu
Published: February 2005

The electrical characteristics of metal-reoxidized nitrided oxide (RNO)-semiconductor devices which employ furnace oxide (OF) and rapid thermal oxide (OR) as starting oxides are investigated. It is found that the RNO structure which uses OF as a starting oxide and with nitridation carried out at a sufficiently high temperature, exhibits the lowest initial interface traps in comparison with other RNO structures. Metal-oxide-semiconductor (MOS) devices which use pure OR as a gate oxide are worthy of note due to their good hot-electron and radiation hardnesses. The gate-area dependence of radiation hardness for various structures is also discussed.
Metal-Insulator-Superconductor Field-Effect-Transistor Using SrTiO3/YBa2Cu3Oy Heteroepitaxial Films
Authors: Fujii Tatsuhiko , Sakuta Ken , Awaji Takahiro , Matsui Ken-ichi , Hirano Takashi , Yasuyuki Ogawa Yasuyuki Ogawa , Takeshi Kobayashi Takeshi Kobayashi
Published: February 2005

Planar-type metal-insulator-superconductor field-effect-transistors (MISFET) were fabricated and their current modulation characteristics were investigated. The FET had a structure of Al-gate metal/(100)SrTiO3-gate insulator/(001)YBa2Cu3O
y
-channel, where the oxide layers were grown by selective heteroepitaxy employing pulsed ArF excimer laser deposition. The FET gate was 10 µm long and 100 µm wide. Apparent field-effect modulation of drain current was seen in both the normal (T>T
c) and superconducting (T<T
c) states. In the superconducting state, not only the critical current but also flux-flow resistance were appreciably changed according to the applied gate voltage.
Different Defect Patterns in Stacked Silicon Films Obtained by Radiative-Heating Zone-Melting Recrystallization
Authors: P. W. Mertens P. W. Mertens , H. E. Maes H. E. Maes
Published: February 2005

The simultaneous zone melting recrystallization of two stacked silicon layers is reported. Branching subgrain boundaries were revealed in the bottom film. Considerably more subtle, straight, parallel, non-branching defect trails were observed in the top layer. The present experiments prove that previous models that attribute this difference to the macroscopic in-plane thermal stress field cannot account for this large difference. The typical defect structure obtained in the top film is thought to be (directly) related to the radiative type of heating applied to this top layer.
Damage during Microchanneling Analysis Using 400 keV Helium Ion Microprobe
Authors: Hirai Kouichi , Takai Mikio , Atsushi Kinomura Atsushi Kinomura , Susumu Namba Susumu Namba
Published: February 2005

Sample damage induced by 400 keV He+ microprobe irradiation during channeling measurements was studied on GaAs and Si. The minimum scattering yield as a function of microprobe dose was measured to investigate the influence of flux densities in GaAs and Si. Threshold doses for damage formation in GaAs were 3×1017-1.2×1018 He+/cm2, depending on flux densities within a range of 1-15 pA/µm2. The threshold dose in Si was 1.6×1018 He+/cm2, independent of flux densities within a range of 0.4-10 pA/µm2. The threshold doses in GaAs were lower than those in Si.
High-Power Continuous-Wave Ultraviolet Generation by Frequency Doubling of an Argon Laser
Authors: Yoichi Taira Yoichi Taira
Published: February 2005

Continuous-wave 257-nm coherent light with a power of 1.2 W is generated by using an intracavity frequency doubling argon laser. In the laser resonator, an elliptical focusing technique is employed to minimize the risk of optical damage to a beta barium borate (BBO) nonlinear optical crystal without sacrificing the frequency conversion coefficient.
Multimode Small-Signal Analysis of Side-Mode Injection-Locked Semiconductor Lasers
Authors: Jhy-Ming Luo Jhy-Ming Luo , Marek Osiński Marek Osiński
Published: February 2005

Temporal response of side-mode injection-locked semiconductor lasers is studied using a small signal analysis of multimode rate equations. The relaxation oscillation frequency and the decay rate are shown to be sensitive to the choice of the injection target mode. Modes with shorter wavelengths have higher relaxation frequencies due to their larger differential gain. Maximum enhancement of the relaxation frequency occurs within that group of target modes. The analysis, together with the previously predicted enhancement of stable locking range, suggests feasibility of applying the side-mode injection technique to increase the modulation bandwidth of semiconductor lasers and hence the transmission speed in optical communication systems, while preserving the usual benefits of injection locking.
Magnetoresistance of Metallic Multilayers
Authors: Okiji Ayao , Nakanishi Hiroshi , Ken Sakata Ken Sakata , Hideaki Kasai Hideaki Kasai
Published: February 2005

The results of a model calculation are reported for magnetoresistance of artificial metallic multilayers. In the model, the main origin of the giant magnetoresistance in the multilayer is considered to be random distribution of magnetic and nonmagnetic ions at the interface. The effect of the random distribution of ions on the resistivity is estimated by the coherent potential approximation in each layer. The pattern behavior of the observed magnetoresistance seems to be reproduced qualitatively.
Preparation of n-ZnO/p-Si Heterojunction by Sol-Gel Process
Authors: Okamura Takeshi , Seki Yoji , Nagakari Shoken , Hideyo Okushi Hideyo Okushi
Published: February 2005

N-type ZnO thin films with a crack and columnar-free structure were successfully prepared on p-type Si substrates by the sol-gel process. The current-voltage (I-V) characteristics of the heterojunction of n-ZnO/p-Si show a rectification with strong electrical breakdown strength of higher than 107 V/cm. The capacitance-voltage (C-V) characteristics show an approximate linear C
-2-V relationship in the reverse bias condition. These results indicate that the ZnO films prepared by the sol-gel process are good enough to be used as a semiconducting material in electrical devices.
Electron Velocity Overshoot Effect in Collector Depletion Layers of InP/InGaAs Heterojunction Bipolar Transistors
Authors: Kurishima Kenji , Nakajima Hiroki , Fukai Yoshino K. , Yutaka Matsuoka Yutaka Matsuoka , Tadao Ishibashi Tadao Ishibashi
Published: February 2005

InP/InGaAs heterojunction bipolar transistors with a 550-Å-thick base and 3000-Å-thick collector layers are fabricated to study the electron velocity overshoot effect in collector depletion layers. The intrinsic delay time evaluated at room temperature measurement remains almost constant at 0.7-0.8 ps in the investigated base/collector bias range of 0 to 1.1 V at a collector current density of 1×105 A/cm2. According to Monte Carlo simulation results, such bias-independent behavior is associated with the sufficiently large overshoot effect caused at high collector biases, where the overshoot velocity is enhanced by the high electric field.
Scanning Tunneling Microscopy Image of GeSb2Te4 Thin Films
Authors: Tominaga Junji , Haratani Susumu , Tokuhiko Handa Tokuhiko Handa , Katsuaki Yanagiuchi Katsuaki Yanagiuchi
Published: February 2005

A scanning tunneling microscopy image of thin film sputtered by a GeSb2Te4 target was obtained in oil conditions. The phase change of the films was confirmed from STM images when the films were heated at 250°C for 2 and 4 minutes. The arrangement of the atoms constituting the surface of the films was inferred through the consideration of the topographic image height with each different work function of the atoms.
Morphology of C60 Single Crystals
Authors: Yositaka Yosida Yositaka Yosida
Published: February 2005

Scanning electron microscope (SEM) observations have been made for pure C60 (99.8%) single crystals. Morphological features obtained from SEM images were compared to those of a truncated octahedron, which is one of the habits of face-centered cubic crystals. Experimental results of interfacial angles between facets showed excellent agreement with those expected from the model.
Effects of Impurity Scattering on Resonant Transmission Coefficients in GaAs/AlAs Double-Barrier Structures
Authors: Fukuyama Hiroyuki , Takao Waho Takao Waho , Takashi Mizutani Takashi Mizutani
Published: February 2005

We investigate the effects of impurity scattering on resonant transmission coefficients in GaAs/AlAs double-barrier structures. The coefficients are estimated from d2
I/dV
2-V characteristics of resonant tunneling diodes, using a recently introduced method. To our knowledge, this is the first time that resonance level broadening due to ionized impurity scattering has been shown experimentally.
Third-Order Optical Nonlinearities in a Photocrosslinkable Polymer
Authors: Li Lian , Lee Junyoung , Zhu Xiaofan , Tripathy Jayant Kumar
Published: February 2005

Quadratic electro-optic coefficient measurements on a dye doped photocrosslinkable nonlinear optical (NLO) polymer-PVCN (polyvinylcinnamate)/CNNB-R (3-cinnamoyloxy-4-[4-(N,N-diethylamino)-2-cinnamoyloxy phenylazo] nitrobenzene) at different dye concentrations are reported. No phase segregation was observed for dye concentrations up to 67 wt% in this polymer system. Large quadratic electro-optic coefficients were measured at 633 nm with a Michelson interferometer.
Electrical Conductivity and ESR Spectrum of Buckminsterfullerene-Doped Poly(3-alkylthiophene)
Authors: Morita Shigenori , Zakhidov Anvar A. , Kawai Tsuyoshi , Hisashi Araki Hisashi Araki , Katsumi Yoshino Katsumi Yoshino
Published: February 2005

Buckminsterfullerene (C60) is effectively doped in poly(3-alkylthiophene). However, the characteristics of C60-doped poly(3-alkylthiophene) are different from the typical behavior observed in the case of conventional dopants. Electrical conductivity of poly(3-alkylthiophene) increases upon C60 doping and decreases again at higher concentration of C60. Its temperature dependence is also anomalous. The absorption spectrum changes markedly upon C60 doping. ESR linewidth decreases from 7.1 G to 1.9 G upon C60 doping. Spin density, evaluated by ESR, is enhanced upon C60 doping. These doping characteristics are tentatively explained by taking electronic energy diagrams of both poly(3-alkylthiophene) and C60 into consideration.
Grazing Exit X-Ray Fluorescence Spectroscopy for Thin-Film Analysis
Authors: Noma Takashi , Ino Hirokatsu Miyata
Published: February 2005

Under the grazing exit condition, X-ray fluorescence (XRF) experiments have been performed for metal thin films (Cu, Ni) on glass substrates. The XRF intensity was measured as a function of the exit angle for nearly normal X-ray incidence. The angular dependence of the grazing exit XRF intensity showed a sharp increase at the critical angle of Kα radiation for the metal film. A three-media model was used to calculate the angular dependence of the XRF intensity. The effects of the film thickness on the XRF intensity curve were also discussed. The applicability of the grazing exit XRF for thin-film analysis was clearly demonstrated.
Study of Magnetic Stray Field Measurement on Surface Using New Force Microscope
Authors: Hosaka Sumio , Kikukawa Atsushi , Yukio Honda Yukio Honda , Hajime Koyanagi Hajime Koyanagi
Published: February 2005

Surface magnetic stray fields are studied using a new force microscope with an optical beam deflection force detector. The measurements are made possible by using both a constant repulsive force control and a magnetic force gradient measurement. The microscope can simultaneously provide a magnetic force gradient image and a surface structure image. Initial results demonstrate that the surface magnetic stray field and the surface structure image of a magneto-optical disk can be obtained. The new method provides feasibility of measuring the surface magnetic stray field.
Fabrication of Periodic Submicron Dot Structures of N-InP by Laser-Induced Surface Electromagnetic Wave Etching
Authors: Kumagai Hiroshi , Ezaki Mizunori , Obara Koichi Toyoda
Published: February 2005

Periodic submicron dot structures were fabricated by laser-induced surface electromagnetic wave etching of indium phosphide substrates. The shape of the dot was observed as a cone whose diameter at the half maximum was about 0.2 µm. Periods along two perpendicular axes were 0.38 µm and 0.57 µm, respectively. The periods were nearly in agreement with the calculation.
Thickness Dependence of Levitation Forces Acting on Magnets over a Thin Superconducting Sheet
Authors: Zhong Jin Yang Zhong Jin Yang
Published: February 2005

Based on the London theory of superconductivity, we have previously introduced a theoretical approach to the calculation of the levitation forces acting on magnets placed above an infinite superconducting plane. Developing this theory, in this letter, we have calculated the thickness dependence of the levitation force. The theoretical approach has also been applied to the calculation of the thickness dependence of the force between the tip of a magnetic force microscope (MFM) and a thin superconducting sheet due to the diamagnetic response of the superconductor to the stray field of the tip.
Bismuth Valence Studies of As-Grown Superconducting Bi-Sr-Ca-Cu-O Thin Films with Tc(zero) from 98 K to 66 K
Authors: Ohbayashi Kazushige , Yoshida Kenji , Anma Masatoshi , Takai Yoshiaki , Hayakawa Hisao
Published: February 2005

Bismuth valence of Bi-Sr-Ca-Cu-O superconducting film has been studied by X-ray photoemission spectroscopy. As-grown highly oriented Bi-Sr-Ca-Cu-O 2223 single-phase films with various critical temperatures from 98 K to 66 K were prepared by changing the Bi content. The Bi 4f core level electron spectra are decomposed into two components. These components are assigned to BiO and to Bi2O3 which is located at an energy higher than the peak of BiO by about 1 eV. Then it was empirically determined that the critical temperature can be controlled by the Bi mean valence, and changes irrespective of the number of Cu-O planes. The critical temperature of the film increases with a decrease in the Bi mean valence which was calculated from the ratio of BiO/Bi2O3.
Fabrication of YBCO/CeO2/YBCO Multilayer Junctions and Their Characteristics
Authors: Takeshi Kusumori Takeshi Kusumori , Ienari Iguchi Ienari Iguchi
Published: February 2005

The fabrication of YBCO/CeO2/YBCO multilayer junctions (YBCO: YBa2Cu3O7-y
) grown by the in situ vacuum deposition technique is reported. The measurements yield reproducible characteristics. The observed phenomena appear either in the tunneling regime or in the Andreev-reflection-like regime depending on the magnitude of the junction resistance. Prominent gaplike structures around 10 mV and 20 mV and additional structures are observed. Temperature dependence of the gap structures is nearly BCS-like. The results are discussed in terms of an anisotropic conduction model.
Electronic Polarizabilities of Transition Metal Ions and Rare-Earth Ions in II-VI Semiconductors
Authors: Sang Ho Sohn Sang Ho Sohn , Yoshihiro Hamakawa Yoshihiro Hamakawa
Published: February 2005

A theoretical estimate for the electronic polarizabilities αs of structural isoelectronic impurities such as transition metal ions and rare-earth ions in II-VI semiconductors has been made in the frame of Ruffa's second-order perturbation theory. The energy levels of the partly filled-inner shells of structural isoelectronic impurities are analyzed on the basis of the change of the effective Madelung energy and the ionization potential energy, which leads to the approximational estimates for αs. The estimated results are compared with some experimental data and found to be in good agreement.
Characterization of Surface Energetic Behavior by Atomic Force Microscopy
Authors: Kawai Akira , Takata Hitoshi Nagata
Published: February 2005

Inorganic solid surfaces which have various surface free energies, 30∼65 dyn/cm, were probed using a Si3N4 cantilever tip. It was found that the attractive force (∼10-7 N), which is generated when a cantilever tip moves away from a solid surface after making contact, is more sensitive to the behavior of surface free energy than that (∼10-9 N) which is generated when the tip moves toward the surface. The relationship between the elastic potential energy of the cantilever and the adhesion energy of the tip-surface system is also discussed.
Scanning Tunneling Microscopy of C60 on the Si(111)7×7 Surface
Authors: Wang Xiang-Dong , Hashizume Tomihiro , Shinohara Hisanori , Saito Yahachi , Yuichiro Nishina Yuichiro Nishina , Toshio Sakurai Toshio Sakurai
Published: February 2005

Adsorption of C60 molecules on the Si(111)7×7 surface was investigated using a field ion-scanning tunneling microscope. C60 adsorbs preferentially on the faulted half of the 7×7 unit and stays still without rotation at room temperature, implying the reasonably strong interaction with the Si substrate. The internal structure of individual C60 molecules can be understood if we assume that the C=C double bonds are imaged brightly. Unlike the case of its adsorption on the Si(100)2×1 surface, C60 do not form ordered mono/multi layers on the 7×7 surface.
Fabrication of Sub-100 nm Wires and Dots in GaAs/AlGaAs Multiquantum Well Using Focused Ion Beam Lithography
Authors: Kitada Hideki , Arimoto Hiroshi , Tackeuchi Atsushi , Yamaguchi Yasuhiro , Nakata Yoshiaki , Akira Endoh Akira Endoh , Shunichi Muto Shunichi Muto
Published: February 2005

We describe a new lateral patterning technique using focused ion beam (FIB) lithography and also two subsequent pattern transfer processes consisting of reactive ion etching and reactive ion beam etching. In the FIB lithography we used a trilevel resist structure consisting of a CMS resist, an Al film, and an SiO2 film. This technique provided 60-nm-wide wires and 100 nm dots in a GaAs/AlGaAs multiquantum well (MQW). Twenty-five-nm-wide wires are also fabricated in GaAs by narrowing the SiO2 mask laterally by wet etching.
Analysis of Resistance Data on a Good Ceramic Sample of YBa2Cu3O7-x
Authors: David M. Eagles David M. Eagles
Published: February 2005

Resistance data between 91.4 and 200 K on a ceramic sample of YBa2Cu3O7-xare analysed using a two-band model for normal-state conductance plus the Lawrence-Doniach theory for effects of superconducting fluctuations. The data is fitted to a root-mean-square accuracy of 0.16% of the resistance in the middle of the temperature range. The steepest slope of the resistance of the sample occurs at 91.13 K, and the analysis shows that the critical region extends to less than 0.3 K aboveTc. Values of parameters found indicate that defect or impurity scattering within grains is unusually small in this sample. Some difficulties in understanding Hall data using either simple two-band models or more sophisticated one-band models are discussed briefly.
Effects of Fe Buffer Layer Thickness on Magnetoresistance in Ni-Fe/Cu Multilayers
Authors: Dei Toshiyuki , Ryoichi Nakatani Ryoichi Nakatani , Yutaka Sugita Yutaka Sugita
Published: February 2005

We present the magnetoresistance and film structure in Ni-Fe/Cu multilayers depend on the Fe buffer layer thickness. With 5-8 nm thick Fe buffer layers, the multilayers have <100> preferred orientations and show high magnetoresistance ratios. On the other hand, when the thickness is 0-4 or 9-10 nm, they have <111> preferred orientations and show low magnetoresistance ratios. The Fe buffer layer thickness affects the preferred orientation, furthermore the preferred orientation strongly correlates to the MR ratio.