bluuebunny/crossref_metadata_2025 huggingface dataset:
Two-Band Electroluminescent Emission in Organic Electroluminescent Diode with Phthalocyanine Film
Authors: Akihiko Fujii Akihiko Fujii , Masayoshi Yoshida Masayoshi Yoshida , Yutaka Ohmori Yutaka Ohmori , Katsumi Yoshino Katsumi Yoshino
Published: October 2002

An electroluminescent (EL) diode utilizing metal-free phthalocyanine ( H2Pc) has been fabricated by the vacuum evaporation method. The optical characteristics of the EL diode, such as the spectra of absorption, photocurrent and electroluminescence, have been investigated, and their temperature dependence has been discussed. We have found, for the first time, that the EL spectrum has two discrete peaks at around 480 nm and above 800 nm.
Electronic Structures and Effects of S Substitutions in CuIn(S0.875X0.125)2 (X=O, N, P, C, SiorB)
Authors: Yamamoto Tetsuya , Katayama-Yoshida Hiroshi
Published: October 2002

We have studied the electronic structures of CuIn(S0.875X0.125)2 (X=O, N, P, C, Si or B) based on the ab-initio electronic band structure calculations using the augmented spherical wave (ASW) method. For p-type CuInS2 crystals doped with N, P, C, Si or B, compared with the case of undoped CuInS2, we have found a smaller energy difference between the center of gravity of 3 d bands of Cu close to dopants and that of the outermost p bands of ligands of the Cu atoms. We have clarified the mechanism of dependence of the hybridization between Cu 3 d states and the outermost p states of dopants, X, on the Cu to X bond character (ionic or covalent).
Smooth and Precipitate-Free Surface of in situ Superconducting Bi2Sr2CaCu2Oy Epitaxial Thin Films Grown on LaSrGaO4 Substrate
Authors: Shin-ichi Karimoto Shin-ichi Karimoto , Shugo Kubo Shugo Kubo , Koji Tsuru Koji Tsuru , Minoru Suzuki Minoru Suzuki
Published: October 2002

We report that LaSrGaO4 substrates are very effective in attaining a smooth and almost precipitate-free surface in in situ grown superconducting Bi2Sr2CaCu2O

y

thin films. These films are grown epitaxially by computer-controlled two-target magnetron sputtering under a high pressure of 0.3–0.5 Torr on LaSrGaO4 (001) substrates heated to 665°C. X-ray diffraction measurements showed no trace of precipitates nor of other phases. AFM, high-resolution SEM and RHEED observation revealed that the film surface is quite smooth and free from precipitates. The surface roughness is no greater than 1.5 nm, half the c-axis lattice constant. The films have a resistivity of as low as 240 µΩ· cm at 300 K and a T
c of 70–80 K.
Ion Beam Modification of BiSrCaCuO Ultrathin Films of Nearly Three Half-Unit-Cell Thickness
Authors: You Jonghun , Masatsugu Kaise Masatsugu Kaise , Kazuo Saito Kazuo Saito
Published: October 2002

The effects of ion irradiation on superconducting BiSrCaCuO ultrathin films were examined. Superconducting ultrathin films with a nearly three half-unit-cell thickness of ∼50 Å were prepared by rf magnetron sputtering and a precisely controlled multistep heat treatment. The 100 keV Ar ion irradiation followed by short-time annealing of these ultrathin films was found to improve the zero-resistance critical temperature T
c,0 in a significant manner. The T
c,0 improvement was marked in the case of low-T
c,0 multiphase films. The ion beam modification of ultrathin films was interpreted in terms of Ar-ion-induced atomic mixing and reordering within a specific volume containing superconducting phases and nonsuperconducting impurity phases.
White-Light-Emitting Organic Electroluminescent Device Using Lanthanide Complexes
Authors: Kido Junji , Ikeda Wataru , Masato Kimura Masato Kimura , Katsutoshi Nagai Katsutoshi Nagai
Published: October 2002

White-light-emitting organic electroluminescent devices with multilayer structures were fabricated using lanthanide metal complexes as the emitter layers. A device with a structure of glass substrate/indium-tin oxide/tetraphenyldiamine derivative (TPD)/terbium complex (tris(acetylacetonato)(monophenanthroline)Tb(III))/ europium complex (tris(dibenzoylmethanato)(monophenanthroline)Eu(III))/aluminum complex (Alq)/Mg:Ag exhibited white electroluminescence. The spectrum consisted of three discrete peaks at 410–420 nm, 545 nm, and 615 nm, from TPD, Tb complex, and Eu complex, respectively.
Temperature Dependence of Current Transport and Electroluminescence in Vacuum Deposited Organic Light Emitting Devices
Authors: Shen Zilan , Burrows Paul E. , Bulovic Vladimir , McCarty Dennis M. , Thompson Mark E. , Stephen R. Forrest Stephen R. Forrest
Published: October 2002

We measure the temperature dependence of the current-voltage (I-V) and electroluminescence (EL) characteristics of organic light emitting devices based on the molecular compound; tris(8-hydroxyquinoline) aluminum ( Alq3). We find that the current is limited by a large density of traps with an exponential energy distribution below the Alq3 lowest unoccupied molecular orbital. The measured trap density suggests that each molecular site may serve as an electron trap, and that EL arises from the recombination of trapped charge. The relationship between the I-V characteristics and EL provides insight into the optimization of vacuum deposited organic light emitting devices.
Adsorption Structure of Copper-Phthalocyanine Molecules on a Si(100)2×1 Surface Observed by Scanning Tunneling Microscopy
Authors: Maeda Yasushi , Matsumoto Takuya , Megumi Kasaya Megumi Kasaya , Tomoji Kawai Tomoji Kawai
Published: October 2002

Isolated copper-phthalocyanine (CuPc) molecules adsorbed on a Si(100)2×1 surface have been observed by scanning tunneling microscopy (STM). The molecular images indicate three configurations which are dominated by the interaction between the aromatic rings of CuPc molecules and dangling bonds of the Si surface. We suggest that STM images reflect the molecular orbital formed by aromatic rings of CuPc and Si dangling bonds.
Surface Characterization of YBa2Cu3Ox(001) Single-Crystal Substrates for Homoepitaxial Growth
Authors: Zama Hideaki , Wang Furen , Koyama Satoshi , Yuh Shiohara Yuh Shiohara , Tadataka Morishita Tadataka Morishita
Published: October 2002

We have evaluated the properties of YBa2Cu3O

x

(001) single-crystal substrates with areas as large as 10×10 mm. They have good crystallinity with a χ min value of 1.8% determined by Rutherford backscattering spectrometry, grains with areas as large as 5×5 mm confirmed by X-ray topography, and excellent surface morphology with unit-cell steps which were observed by atomic force microscopy. However, approximately one unit-cell-thick degraded layer on the surface, which was observed by angle-resolved X-ray photoelectron spectroscopy, presents problems which must be resolved. These analyses indicate that YBa2Cu3O

x

single crystal grown by the pulling method is a promising substrate material for homoepitaxial growth.
Raman Peak in Low-Frequency Region of Dehydrated Egg-White Gel
Authors: Atsushi Nakamura Atsushi Nakamura , Hirotaka Okabe Hirotaka Okabe , Kazuhiro Hara Kazuhiro Hara , Nobuyasu Hiramatsu Nobuyasu Hiramatsu
Published: October 2002

A new low-lying Raman mode was found in dehydrated heat-treated egg-white gel. The peak position and spectral profile were similar to those observed in polyacrylamide gel. The new mode may be the boson peak which is commonly observed in amorphous materials.
Epitaxial Growth of Er3+-Doped CaF2 by Molecular Beam Epitaxy
Authors: Adachi Kazunori , Yao Takafumi , Taniuchi Tetsuo , Kasuya Atsuo , Miles Richard H. , Uda Satoshi , Tsuguo Fukuda Tsuguo Fukuda
Published: October 2002

Monocrystalline Er3+-doped CaF2 layers are grown on CaF2 substrates by molecular beam epitaxy (MBE) with Er3+ concentration up to 31.2 wt%. The lattice parameter and the crystallinity of the epilayers are investigated by X-ray diffraction analysis, electron probe microanalysis, and scanning electron microscopy. Green light emission at 538 nm is generated by upconversion for the first time, using a 798 nm laser diode pump. Maximum emission intensity at this wavelength is obtained at an Er3+ concentration of 13.3 wt%.
Growth of Single Crystals of C60 and C70
Authors: Shi Jen-Bin , Chang Wen-Yang , Lee Shinn-Rong Su
Published: October 2002

Large, high-quality C60 crystals with fcc structure were grown by modified vapor transport. This technique involving the use of a narrow open tube and flowing helium as a carrier gas enables growth of crystals up to 3.2 mm larger than those grown using a primary vapor trasport growth method. Single crystals of C70 with pure hcp 1 phase were also obtained.
Etching and Surface Modification of GaAs by Hydrogen Radicals Generated by Hydrogen Microwave Afterglow Method
Authors: Nagayoshi Hiroshi , Yuichi Yamamoto Yuichi Yamamoto , Koichi Kamisako Koichi Kamisako
Published: October 2002

We etched crystalline GaAs using hydrogen radicals generated by the hydrogen microwave afterglow method and determined the dependence of etching rate on substrate temperature, microwave power, and sample distance from the quartz tube supplying hydrogen radicals. From the Arrhenius plot, the activation energy was found to be 0.43 eV. The surface morphology could be varied from flat to textured by changing the etching conditions.
Synthesis of RbxC 60 Film by Electrolysis
Authors: Endo Hiraku , Nobunari Yoshiyama Nobunari Yoshiyama , Hiroshi Yamamoto Hiroshi Yamamoto
Published: October 2002

An electrolysis process was used to obtain a Rb1C60 film from an organic electrolyte containing C60 molecules. The solution used was a mixture of 0.3 mM–C60, 0.1 N–RbClO4 and N,N-dimethylformamide (DMF)/toluene (1:1). The particles in the obtained film were spindle-shaped and grew to a size of about 1 µ m, depending on the reaction temperature. The Raman spectra of the obtained films indicated the presence of solid C60 and revealed the characteristics of polymeric Rb1C60, the crystal structure of which was confirmed to be body-centered-orthorhombic by X-ray diffraction analysis.
Si-Doping in GaN Grown by Metal-Organic Vapor Phase Epitaxy Using Tetraethylsilane
Authors: Kaneda Naoki , Detchprohm Theeradetch , Kazumasa Hiramatsu Kazumasa Hiramatsu , Nobuhiko Sawaki Nobuhiko Sawaki
Published: October 2002

A Si-doped GaN layer was grown by MOVPE (metal-organic vapor phase epitaxy) using tetraethylsilane (TeESi) as the dopant. The Hall effect was studied between 11 K and 300 K. The electron concentration was observed to increase with the increase in the TeESi flow rate. The activation energy E
D for ionization of shallow donors was determined to be 27 meV.
Photoluminescence Spectra of Nitrogen-Doped ZnSe by Photoassisted Metal-Organic Chemical Vapor Deposition
Authors: Fujita Yasuhisa , Toshiyuki Terada Toshiyuki Terada , Satoshi Fujii Satoshi Fujii
Published: October 2002

Photoluminescence spectra of nitrogen-doped ZnSe grown by photoassisted metal-organic chemical vapor deposition (MOCVD) at temperatures of 330 and 350° C and with nitrogen concentration ranging from 2.0×1017 cm-3 to 3.0×1018 cm-3 were measured. The spectra of lightly doped samples showed a donor-to-acceptor (D-A) pair emission line at 2.696 eV with LO phonon replicas. The spectra for heavily doped samples were dominated by a broad-band D-A pair emission at longer wavelengths. The comparison of photoluminescence spectra of nitrogen-doped ZnSe grown by MOCVD and molecular beam epitaxy (MBE) is discussed.
4-Monolayer-Height Layer-by-Layer Growth and Increase of the Critical Thickness of Ge Heteroepitaxy on Boron-Preadsorbed Si(111) Surface
Authors: Kumagai Yoshinao , Ishimoto Kouichi , Mori Ryosuke , Tee Keh-Ming , Ishibashi Takayuki , Mitsuo Kawabe Mitsuo Kawabe , Fumio Hasegawa Fumio Hasegawa
Published: October 2002

Heteroepitaxy of Ge was performed onto clean Si(111)7×7 and 1-monolayer (ML) boron-preadsorbed Si(111)√ 3×√ 3R30°–B surfaces held at 500° C. Both cases of growth showed the Stranski-Krastanov (SK) growth mode. On the clean surface, layer-by-layer growth by 2-ML-height two-dimensional (2D) islands lasted for up to 6 ML of Ge growth, and then relaxed 3D islands began to be formed. On the boron-preadsorbed surface, however, critical thickness for the formation of 3D islands increased to 8 ML due to suppression of Ge surface migration by surface-segregated boron atoms. It was confirmed by atomic force microscopy (AFM) that the height of 2D islands appearing in the layer-by-layer growth process changed from the normal 2 ML to 4 ML on the boron-preadsorbed surface.
Influence of the Nonequilibrium Superconductivity Effect on the Quasiparticle Current-Voltage Characteristics of Intrinsic Tunnel Josephson Junctions
Authors: Minoru Suzuki Minoru Suzuki , Keiichi Tanabe Keiichi Tanabe
Published: October 2002

We have numerically evaluated the influence of the nonequilibrium heating effect on the quasiparticle current-voltage (I–V) characteristics of a superconductor-insulator-superconductor tunnel junction made of a two-dimensional d-wave superconductor based on two different models. It is found that the self-injection of quasiparticle current causes significant I–V curve deformation due to the influence of the nonequilibrium superconductivity effect. The results are applied to the I–V curves observed in Bi-2212 intrinsic tunnel Josephson junctions to obtain a good agreement. The difference between the nonequilibrium superconductivity effect and simple Joule heating is discussed.
Development of Integrated Direct Current Superconducting Quantum Interference Device Gradiometer for Nondestructive Evaluation
Authors: Morooka Toshimitsu , Nakayama Satoshi , Odawara Akikazu , Shimizu Nobuhiro , Chinone Kazuo , Kasai Tatsuaki Ataka
Published: October 2002

A Direct Current Superconducting Quantum Interference Device (DC-SQUID) gradiometer for nondestructive evaluation was developed. A pick-up coil and a DC-SQUID were integrated on a 3×3 mm2 Si chip. In order to raise the spatial resolution of the gradiometer, a coplanar concentric second-order derivative coil was adopted as a pick-up coil. The pick-up coil consisted of a one-turn outer coil and a four-turn inner coil connected in series and counterclockwise to each other. The diameters of the outer coil and the inner coil were 2 mm and 1 mm, respectively. The size of the pick-up coil was determined by calculating the spatial resolution in relation to the bottom thickness of the cryostat. The high spatial resolution of the DC-SQUID gradiometer was experimentally confirmed.
Hysteretic Magnetoresistance in Nd1-xSrxMnO3 Films with Controlled Carrier Density
Authors: Kasai Masahiro , Kuwahara Hideki , Moritomo Yutaka , Tomioka Yasuhide , Tokura Yoshinori
Published: October 2002

Magnetotransport characteristics and their nominal hole concentration (x) dependence were investigated in Nd1-
x

Sr

x

MnO3 films. Thermal hysteresis in resistivity indicating the occurrence of a first-order phase transition was observed for x=0.35 and 0.50, but essentially not for x=0.40 and 0.45. The x=0.35 and 0.50 films also show hysteresis in magnetoresistance. Once the resistivity is decreased by an order of magnitude by application of a magnetic field, the low-resistivity state is maintained even after removal of the field below a critical temperature. Observed hysteretic behavior suggests the presence of instabilities which compete with double-exchange interaction in specific hole concentration regions, which may be one of the origins of the colossal magnetoresistance.
Crystal Form of Phosphoric-Acid-Doped Triglycine Sulfate
Authors: Noriyuki Nakatani Noriyuki Nakatani , Masakazu Yoshio Masakazu Yoshio
Published: October 2002

Single crystals of phosphoric-acid-doped triglycine sulfate (TGSP) were grown from aqueous solutions with various concentrations of H3PO4 in the ferroelectric phase. The development of crystal faces is gradually modified as the concentration of H3PO4 in the solution becomes higher. In particular, the {010} faces become more conspicuous with greater doping. A high number of H3PO4 molecules are incorporated into the {010} growth sectors. The general crystal form shows the nonpolar 2/m symmetry similar to that of pure TGS, due to its multidomain structure.
Fine SiO2 Pattern Generation by Electron Beam Direct Writing onto Polysiloxene-Based Thin Films and Its Application to Etch Mask
Authors: Okamoto Katsuhiko , Yamakawa Shinpei , Seiichi Miyazaki Seiichi Miyazaki , Masataka Hirose Masataka Hirose
Published: October 2002

Polysiloxene-based thin films have been grown by an rf glow discharge decomposition of an Si2H6+O2 gas mixture at a substrate temperature of -110° C. The bonded hydrogen in the network is effused by electron beam (EB) irradiation, resulting in local SiO2 network formation. The nonirradiated region is easily etched off by a dilute HF or KOH solution, while the irradiated region is hardly etched. Thus the polysiloxene-based thin film is used as a negative-tone EB resist to generate the 0.1 µ m line-and-space SiO2 pattern, which is used as an etch mask to fabricate a fine silicon structure.
Atomic Force Microscopic Study of Subsurface Ordering and Structural Transforms in n-Alcohol on Mica and Graphite
Authors: Nakada Toshitaka , Miyashita Satoru , Sazaki Gen , Chernov Hiroshi Komatsu
Published: October 2002

Structure forces inn-alcohols (CnH2n+1OH (8≤n≤12)) on the mica or graphite surfaces were investigated using an atomic force microscope (AFM). The structure force on graphite has a periodicity of ∼0.5 nm, which is independent of temperature. The structure force on mica has a periodicity of 0.86 nm whenT<40° C which increases linearly withnin the range 1.7 to 2.3 nm whenT>40° C. This phase transition corresponds to a change in the alignment of molecules on the surface from parallel (lying, atT<40° C) to normal (standing, atT>40° C).
A New Single-Layer Resist for 193-nm Lithography
Authors: Nozaki Koji , Watanabe Keiji , Namiki Takahisa , Igarashi Miwa , Yoko Kuramitsu Yoko Kuramitsu , Ei Yano Ei Yano
Published: October 2002

A positive chemically amplified resist for 193-nm lithography has been developed. The resist consists of a copolymer of tetrahydro-4-methyl-2-oxo- 2H-pyran-4-yl methacrylate and 2-methyl-2-adamantyl methacrylate and a photoacid generator. The acid-catalyzed deprotection of the protective groups leads to a large polarity change in the exposed region of the resist films and it allows for high-contrast patterning with high sensitivity. Using an ArF excimer laser exposure system, a 0.17-µ m lines and spaces pattern has been resolved.
High Peak-to-Valley Current Ratio GaAs/InGaAs/InAs Double Stepped Quantum Well Resonant Interband Tunneling Diodes at Room Temperature
Authors: Yang Chih-Chin , Huang Kuang-Chih , Su Yan-Kuin
Published: October 2002

A high ratio of the peak current density to the valley current density of current-voltage characteristic is accomplished for the double stepped quantum well resonant interband tunneling diode (DSQW RITD). Results for good quantum confinement effect and long drift layer with deep quantum well GaAs/In0.59Ga0.41As/InAs DSQW RITD that has a lower valley current density of about 0.98 A/cm2and a higher peak-to-valley current ratio (PVCR) reached 622 at room temperature than conventionally designed double quantum well resonant interband tunneling diodes (DQW RITDs) are presented. This PVCR value is also the highest value than those of the other resonant tunneling diodes.
Low-Temperature-Processed Polycrystalline Silicon Thin-Film Transistors Using Titanium Disilicide Contacts for Source and Drain
Authors: Sung-Keun Chang Sung-Keun Chang , Ohyun Kim Ohyun Kim
Published: October 2002

We propose a new process without source-drain doping for realization of low-temperature polycrystalline silicon (poly-Si) thin-film transistors (TFT's). The process is based on TiSi2 contacts for source and drain. Titanium disilicide was formed by in situ silicidation using high-temperature magnetron sputtering at 450° C. The new device has demonstrated better leakage characteristics (∼0.4 pA/µ m) and slightly lower ON current compared with standard-processed devices having phosphorus-doped source and drain with a dose of 1×1014 cm-2. The field-effect mobility (∼10 cm2/ V·s) and I
on/I
off current ratio (∼1.2×106) are comparable to those of standard-processed devices.
High-Oxygen-Pressure Synthesis of Superconducting YBa2Cu3O7+y
Authors: Okai Bin , Kato Katsuo , Ono Akira
Published: October 2002

Preparation of the overdoped superconductor YBa2Cu3O7+
y

was reexamined. Heat treatment of YBa2Cu3O7 under high oxygen pressure produces YBa2Cu3O7+
y

along with increasing amounts of other phases: BaO2 and an oxide mixture of chemical composition 1/2Y2O3+3CuO+(0.25∼0.45)O2, as more oxygen is supplied. Even when the oxygen content 7+y far exceeds 7, the onset of the superconducting transition temperature remains unchanged at 91∼92 K, whereas the volume ratio of superconductivity is ultimately reduced to less than 40% of that of YBa2Cu3O7.
Transparent Conducting Al-Doped ZnO Thin Films Prepared by Pulsed Laser Deposition
Authors: Akio Suzuki Akio Suzuki , Tatsuhiko Matsushita Tatsuhiko Matsushita , Naoki Wada Naoki Wada , Yoshiaki Sakamoto Yoshiaki Sakamoto , Masahiro Okuda Masahiro Okuda
Published: October 2002

Thin films of ZnO:Al have been deposited on glass substrates by a pulsed laser deposition technique employing an ArF laser ( λ=193 nm). For all experiments, a repetition rate of 10 Hz, an energy density of 1 J/cm2, and an irradiation time of 20–30 min (12000–18000 shots) were assumed. Optical transmittance of around 90% was observed in the visible region of the spectrum for the 150–200 nm thick film. Resistivities of 1.43×10-4 Ω·cm and 5.62×10-4 Ω·cm were obtained at substrate temperatures of 300°C and room temperature, respectively.
Charge Trapping Properties of uv-Exposed Polyimide Films for the Alignment of Liquid Crystals
Authors: Yang K. H. , Tajima Kenichi , Takenaka Atsushi , Takano Hideo
Published: October 2002

A model has been developed to account for the occurrence of flickers and image-stickings in TN or two-domain TN cells aligned by polyimide (PI) films with one of the films subjected to uv radiations prior to rubbings. The probability of flickers and image-stickings is proportional to the imbalance in the charge densities trapped on the two interfaces between the LC medium and two alignment PI films. Rate equations are established to calculate this charge imbalance for the cases of low-frequency ac voltages applied on the TN cell. The modeled results are in good agreement with the experimental results using various PI material as alignment layers for the TN cells. The mechanism of uv-induced charge-trapping centers on the PI films is discussed.
Preparation of Layered Ferroelectric Bi2SrTa2O9 Single-Crystal Platelets
Authors: Suzuki Masayuki , Nagasawa Naomi , Akio Machida Akio Machida , Takaaki Ami Takaaki Ami
Published: October 2002

Layered ferroelectric Bi2SrTa2O9 is attracting much attention as a fatigue-free material for ferroelectric nonvolatile memory devices. We have successfully synthesized this single-crystal platelet without any impurity phases by the self-flux method. The largest crystals measure about 1 mm×1 mm×5 µ m, and the lattice parameters were estimated to be a=0.5528 nm and c=2.498 nm, assuming a tetragonal cell. The chemical composition is 1.92:1.10:2.00 in an atomic ratio of Bi:Sr:Ta, from ICP-AES analysis. By wet etching, the crystal structure was found to be decomposed anisotropically, leaving only the c-axis framework. The step height of the topmost surface observed by atomic force microscopy (AFM) was 1.2 to 1.3 nm, which corresponds to half of the c-axis length (about 2.5 nm). Through thermal analysis, the thermal anomaly originating in ferroelectric-paraelectric phase transition was not observed and there was little evaporation of Bi compounds.
Pulsed Laser Deposition of Epitaxial Ferroelectric Pb(Zr, Ti)O3 Films on Si(100) Substrate
Authors: Lee Myung Bok , Kawasaki Masashi , Mamoru Yoshimoto Mamoru Yoshimoto , Hideomi Koinuma Hideomi Koinuma
Published: October 2002

Pb(Zr0.52Ti0.48)O3 (PZT)/ SrTiO3/TiN trilayered films were grown heteroepitaxially on Si(100) substrate by pulsed laser deposition. The TiN layer was employed as a bottom electrode for the PZT capacitor and the thin SrTiO3 layer was used as a seed layer for epitaxial growth of PZT. Good crystallinity and sharp interfaces of the structure were verified by X-ray diffraction analysis and secondary ion mass spectrometry, respectively. Polarization-electric field ( P-E) curve showed a remanent polarization of 12 µ C/ cm2 and a coercive field of 130 kV/cm for a PZT film of 400 nm thickness. Leakage current at E=400 kV/cm was less than 10-7 A/cm2.
Site-Specific Characteristic of the Kikuch-Like Bands in High-Angular-Resolution X-Ray Photoelectron Diffraction
Authors: Ichinohe Yuji , Ishii Hideshi , Owari Masanori , Yoshimasa Nihei Yoshimasa Nihei
Published: October 2002

Fine-mesh two-dimensional measurements of Ca2p and F1s X-ray photoelectron diffraction (XPED) patterns from a CaF2(111) surface were performed with high angular resolution. These measurements revealed a great deal of fine structure including many Kikuchi-like bands and circular patterns. On comparing the Ca2p and F1s XPED patterns, an energy dependence of the Kikuchi-like bands and circular patterns was observed. Furthermore, the Kikuchi-like bands associated with the (111) plane differed substantially between the Ca2p and F1s XPED patterns. This is the first report of the site-specific characteristic of the Kikuchi-like bands in XPED.
Growth of Transparent Conductive Oxide ZnO Films by Atomic Layer Deposition
Authors: Baosheng Sang Baosheng Sang , Makoto Konagai Makoto Konagai
Published: October 2002

ZnO films have been grown by atomic layer deposition (ALD) using diethylzinc (DEZn) and H2O as reactant gases. Self-limiting growth occurred at substrate temperatures ranging from 105 to 165° C. Self-limiting growth was also achieved when the flow rates of DEZn and H2O were varied. It was found that the orientation and surface morphology of the films were strongly dependent on the substrate temperature. A high electron mobility of 30 cm2/V·s was obtained for undoped ZnO films only 220 nm thick. The mobility of films was higher than that of films grown by MOCVD.
High-Density GaAs/AlAs Quantum Wires Grown on (775)B-Oriented GaAs Substrates by Molecular Beam Epitaxy
Authors: Masataka Higashiwaki Masataka Higashiwaki , Masanori Yamamoto Masanori Yamamoto , Takahiro Higuchi Takahiro Higuchi , Satoshi Shimomura Satoshi Shimomura , Akira Adachi Akira Adachi , Yasunori Okamoto Yasunori Okamoto , Naokatsu Sano Naokatsu Sano , Satoshi Hiyamizu Satoshi Hiyamizu
Published: October 2002

GaAs/AlAs quantum wires (QWRs) were found to be naturally formed by a regularly corrugated AlAs/GaAs interface and a flat GaAs/AlAs interface in an AlAs/GaAs/AlAs quantum well with a well width of 3.3 nm grown on a (775)B GaAs substrate by molecular beam epitaxy. The lateral period and vertical amplitude of the AlAs/GaAs interface corrugation were 12 nm and 1.2 nm, respectively. The QWRs were formed side by side with an extremely high density of 8×105 QWRs/cm. A photoluminescence peak at λ=715 nm from the QWRs with a cross section of about 12×3 nm2 showed a polarization degree of (I
∥ - I
⊥) / (I
∥ + I
⊥) = 0.11 and a very small full width at half maximum of 15 meV at 4.2 K.
Relaxation of Trapped Magnefic Field in a Bi-2212/Ag Solenoidal Coil with Persistent Current Switch
Authors: Michiya Okada Michiya Okada , Keiji Fukushima Keiji Fukushima , Kazuhide Tanaka Kazuhide Tanaka , Hiroaki Kumakura Hiroaki Kumakura , Kazumasa Togano Kazumasa Togano , Tsukasa Kiyoshi Tsukasa Kiyoshi , Kiyoshi Inoue Kiyoshi Inoue
Published: October 2002

We succeeded in the persistent current mode operation of a small Bi2Sr2Ca1Cu2O

x

(Bi-2212) solenoidal coil with persistent current switch (PCS). The coil and the PCS were fabricated using silver sheathed Bi-2212 multifilamentary tape. We confirmed the ability to trap a 1000 G magnetic field with a persistent current of 30 A. From the relaxation of persistent current up to 50 h, a relaxation time was estimated to be τ>800 ks, showing a resistance in overall current loop below 0.2 n Ω. The average rate of magnetic relaxation was 0.4%/h with a inductance L of 0.2 mH. The relaxation was able to explain by means of the thermally assisted flux creep model. The pinning potential U
0 was estimated from the relaxation curve to be 6 meV.
Low-Threshold 1.3 µm Wavelength, Strained-Layer InGaAsP Multi-Quantum Well Lasers Grown by All Solid Source Molecular Beam Epitaxy
Authors: Mika Toivonen Mika Toivonen , Pekka Savolainen Pekka Savolainen , Harry Asonen Harry Asonen , Richard Murison Richard Murison
Published: October 2002

We report the growth, by all solid source molecular beam epitaxy (SSMBE) of low-threshold 1.3 µ m wavelength strained-layer InGaAsP multi-quantum well lasers. A threshold current density of 400 A/cm2 was achieved for a 1600 µ m long broad-area laser, and a threshold current of 18 mA was measured for a 5×320 µ m as-cleaved ridge waveguide laser. These are the lowest values reported for SSMBE grown material, and the fabricated lasers compare favorably to the best devices grown by other techniques.
Observation of Silicon Surfaces Using Ultrahigh-Vacuum Noncontact Atomic Force Microscopy
Authors: Shin'ichi Kitamura Shin'ichi Kitamura , Masashi Iwatsuki Masashi Iwatsuki
Published: October 2002

Noncontact imaging has been developed for atomic force microscopy in ultrahigh vacuum in order to avoid the damage to the sample surface caused by the intense interaction between the clean surfaces of the sample and probe tip, which is a problem commonly observed in contact imaging. Initially it was thought that the noncontact (NC) mode might fail to achieve atomic level resolution due to the long distance between the tip and sample. Recently, it has been proved that this is not so. We used an FM detection system utilizing an oscillating cantilever with a constant-amplitude voltage supplied to the piezotransducer; and successfully obtained NC-mode stable atomic-resolution AFM images of the 2×1 structure of the Si(100) surface as well as the 7×7 structure of the Si(111) surface. We also compared AFM and STM images of the 7×7 structure in the same area of view.
High-Density Layer at the SiO2/Si Interface Observed by Difference X-Ray Reflectivity
Authors: Awaji Naoki , Ohkubo Satoshi , Nakanishi Toshiro , Sugita Yoshihiro , Kanetake Takasaki Kanetake Takasaki , Satoshi Komiya Satoshi Komiya
Published: October 2002

We have developed a high-accuracy difference X-ray reflectivity (DXR) method using intense synchrotron radiation for the evaluation of ultrathin thermal oxides on Si(100). By carefully analyzing DXR data for gate oxides with thicknesses of 40 Å and 70 Å grown at 800° C to 1000° C, the existence of a dense ( ∼2.4 g/cm3), thin (∼10 Å) layer at the S
i
O
2/S
i interface has been revealed. The thickness of the interfacial layer decreases with increasing oxidation temperature. Oxides grown in O3 or HCl/O2 have a thinner interfacial layer compared to those grown in O2.
Thermodynamic Analysis of InxGa1-xN Alloy Composition Grown by Metalorganic Vapor Phase Epitaxy
Authors: Koukitu Akinori , Takahashi Naoyuki , Tetsuya Taki Tetsuya Taki , Hisashi Seki Hisashi Seki
Published: October 2002

A thermodynamic analysis of alloy composition is described for metalorganic vapor phase epitaxy (MOVPE) of In

x

Ga1-
x

N. The vapor-solid distribution relationship is discussed in comparison with the experimental data reported in the literature. It is shown that the solid composition of In

x

Ga1-
x

N alloy grown by MOVPE is thermodynamically controlled. The origin of the deviation of the solid composition from the linear relation is also discussed.
Free Electron Laser Annealing of Amorphous Silicon Carbide
Authors: Ohyama Hideaki , Suzuki Toshiji , Nishi Kazuhisa , Tsuneo Mitsuyu Tsuneo Mitsuyu , Takio Tomimasu Takio Tomimasu
Published: October 2002

We have applied a free electron laser (FEL) to crystallize amorphous silicon carbide (a-SiC) at room temperature. The FEL has two main characteristics, wavelength tunability and ultrashort-pulse operation (∼10 ps) with intense peak power ( ∼MW). The wavelength was selected to be 12.6 µ m which corresponds to the energy of the Si–C stretch mode in order to excite the lattice vibration directly. FT-IR measurements of the a-SiC film showed that the broad peak in the absorption spectrum became sharp after irradiation with the FEL. X-ray diffraction measurements of the irradiated sample revealed a peak related to SiC crystals. These measurements suggest that crystallization of a-SiC occurs at room temperature when irradiation with a FEL.
Nonscalability of Alpha-Particle-Induced Charge Collection Area
Authors: Takashi Tanii Takashi Tanii , Takashi Matsukawa Takashi Matsukawa , Shigetaka Mori Shigetaka Mori , Meishoku Koh Meishoku Koh , Bungo Shigeta Bungo Shigeta , Kai Igarashi Kai Igarashi , Iwao Ohdomari Iwao Ohdomari
Published: October 2002

The scalability of alpha-particle-induced soft errors has been evaluated. We have irradiated individual sites in and near a PN-junction area with single alpha particles and measured the charge collected at the junction. As the PN-junction size is reduced, the charge collected by diffusion upon the incidence of alpha particles at the outer area around the junction increases relative to the charge collected upon direct incidence at the junction area. This suggests that the soft-error-sensitive area is not scaled down even if memory cell size is reduced.
A Repetition-Rate Stabilized and Tunable, Regeneratively Mode-Locked Fiber Laser Using an Offset-Locking Technique
Authors: Nakazawa Masataka , Yoshida Eiji , Eiichi Yamada Eiichi Yamada , Yasuo Kimura Yasuo Kimura
Published: October 2002

The repetition rate of a regeneratively and harmonically mode-locked fiber laser at 10 GHz has been successfully stabilized by using an offset locking technique. The clock frequency which deviates from a standard frequency is converted into a voltage signal using a double balanced mixer and an F/V converter. This voltage signal, after passing through electrical control units, is fed back to the PZT on which part of the fiber cavity is wound. In this way, a repetition-rate stability of more than 10-9 was achieved.
Microscopic Mechanism of Electrical Noise in Co/Si Thin Film Structures
Authors: Cho Nam-Ihn , Hyoung Gin Nam Hyoung Gin Nam , Soon Jae Yu Soon Jae Yu
Published: October 2002

A microscopic mechanism of the production of electrical fluctuations in noncrystalline structures has been studied by measuring 1/f noise parameters and analyzing microstructure of Co/Si interfaces along the silicide nucleation reaction path. The measured noise power spectral density presents the largest fluctuations near the structural (noncrystalline-to-crystalline) transition and the electronic (semiconducting-to-metallic) transition region. The amplitude of the noise spectral density at the frequency of 1 Hz drops more than 3 orders after the nucleation of the first cobalt silicide phase. The variation of the noise parameter is assumed to be an indication of the phase transformation along the nucleation reaction path in a Co/Si thin film system. Structural studies suggest that the observed electrical noise might originate from cobalt atom movements in reversible processes between different chemical structures.
Control of Thickness Variation in Si-on-Insulator Bonded Wafers by Applying Voltage during KOH Etching
Authors: Atsushi Ogura Atsushi Ogura
Published: October 2002

A new thinning technique is developed to control thickness variation in Si-on-insulator (SOI) bonded wafers. During KOH etching, voltage is applied between the supporting substrate and the etchant. Excellent SOI thickness variation of less than ±0.1 µm is achieved by etching 4±0.5 µm thick, 150 mmφ SOI bonded wafers. The resulting film thickness after etching is controlled from 0.8 to 2.6 µm by changing the applied voltage from 50 to 75 V.
Optical Characterization of Srm-3Bi4TimO3m+3 (m=4, 5, 6) Thin Films Grown by Pulsed Laser Deposition Method
Authors: Tachiki Minoru , Kazuyuki Yamamuro Kazuyuki Yamamuro , Takeshi Kobayashi Takeshi Kobayashi
Published: October 2002

Sr

m
-3Bi4Ti

m

O3
m
+3 (m=4, 5, 6) thin films were grown on (100)MgO and (100)Pt/(100)MgO substrates by the pulsed laser deposition (PLD) method. X-ray diffraction (XRD) revealed c-axis-oriented crystal growth of each Sr

m
-3Bi4Ti

m

O3
m
+3 film. Reflection high-energy electron diffraction (RHEED) from the films showed a streak pattern which indicates the epitaxial ordering of the fabricated thin films. Fundamental optical absorption of SrBi4Ti4O15, Sr2Bi4Ti5O18 and Sr3Bi4Ti6O21 films started at 3.4, 3.5 and 3.7 eV, respectively. Moreover, the Fourier transform infrared (FTIR) spectra also revealed a systematic change in their LO-phonon absorption dip structure.
Time-Resolved X-Ray Absorption Spectroscopy for Laser-Ablated Silicon Particles in Xenon Gas
Authors: Tetsuya Makimura Tetsuya Makimura , Tamaki Sakuramoto Tamaki Sakuramoto , Kouichi Murakami Kouichi Murakami
Published: October 2002

We developed a laboratory-scale in situ apparatus for soft X-ray absorption spectroscopy with a time resolution of 10 ns and a space resolution of 100  µm. Utilizing this spectrometer, we have investigated the dynamics of silicon atoms formed by laser ablation in xenon gas. It was found that 4d-electrons in the xenon atoms are excited through collision with electrons in the laser-generated silicon plasma.
Gain Curves of a Microchannel Plate Ion Detector for Measurement of End-Loss Ions in the Tandem Mirror
Authors: Tetsuya Goto Tetsuya Goto , Kameo Ishii Kameo Ishii , Toshiki Takahashi Toshiki Takahashi , Akira Abe Akira Abe , Yuzo Katsuki Yuzo Katsuki , Nagayoshi Kikuno Nagayoshi Kikuno , Yasuhiro Goi Yasuhiro Goi , Yoshihiro Ono Yoshihiro Ono , Nobutsugu Ishibashi Nobutsugu Ishibashi , Yousuke Nakashima Yousuke Nakashima , Kiyoshi Yatsu Kiyoshi Yatsu , Teruo Tamano Teruo Tamano
Published: October 2002

A microchannel plate (MCP) is used as an ion detector in the end-loss energy component analyzer, which has been developed in order to measure velocity distribution functions of end-loss ions in the tandem mirror GAMMA10. The gain of the MCP depends on variable parameters of the incident ion energy, the incident ion current density, and the MCP bias voltage. The gain characteristics was obtained using a hydrogen beam test stand, and the gain curves were described as a function of the parameters for the purpose of the quantitative evaluation of end-loss ions.
Enhancement of the Transport Critical Current Density in a YBa2Cu3Ox Ceramic by Electron Irradiation under Remanent Magnetic Fields
Authors: Kensuke Shiraishi Kensuke Shiraishi
Published: October 2002

The transport critical current density of YBa2Cu3O

x

ceramic was measured at zero external field and various temperatures from 15 to 90 K and then at temperatures from 90 to 15 K, after application of a constant magnetic field of 1.0 T at about 15 K. The critical current density was enhanced by 3 MeV electron irradiation at doses of up to 4.0×1021 m-2 during cooling from 90 to 15 K under the remanent magnetic fields induced by externally applied fields of up to 0.05 T, whereas the critical current density deceased markedly at low temperatures during heating to 90 K.
Size Reduction of Silver Particles in Aqueous Solution by Laser Irradiation
Authors: Takami Akinori , Yamada Hirotoshi , Kaoru Nakano Kaoru Nakano , Seiichiro Koda Seiichiro Koda
Published: October 2002

The effect of pulsed laser irradiation on silver particles in aqueous solution was investigated. The particle size decreased and the size distribution became narrower after irradiation for 15 minutes using third harmonics of a pulsed YAG laser. The number of the aggregated particles also decreased after the irradiation.
Low-Crosstalk Acoustooptic Wavelength Filter Composed of Cascaded Dissimilar Mode Converters
Authors: Hideaki Okayama Hideaki Okayama , Takeshi Kamijoh Takeshi Kamijoh
Published: October 2002

We developed a low-crosstalk, narrow-linewidth guided-wave acoustooptic filter. To decrease the sidelobe level, cascaded filters with different mode converter lengths and conversion strengths were used. We attained a sidelobe level below -20 dB using the device in which the first- to second-stage mode converter length ratio was 0.8, and attained a transmission peak full width at half-maximum of 1 nm.
In Situ Transmission Electron Microscopy Observation of Au–Si Interface Reaction
Authors: Ishikawa Yukari , Tomohiro Saito Tomohiro Saito , Noriyoshi Shibata Noriyoshi Shibata
Published: October 2002

Cross-sectional transmission electron microscopy (TEM) was used to observe Au–Si reaction and Si pyramid formation processes in situ. The Au–Si reaction occurred in three stages in a heating process; Au and Si layers reacted through a rough Au/Si interface, the rough Au/Si interface suddenly became flat, and single-crystal Si suddenly changed into a microcrystalline Au–Si layer. Si pyramids were formed in the Au layer in a cooling process, although Au pyramids were formed in the Si substrate by annealing in air. It is concluded that Au- and Si-pyramid formation depends on the Au and Si concentrations in the reaction area, which vary with the degree of surface oxidation.
In Situ Monitoring of Adsorption and Desorption of Atomic Nitrogen on GaAs (001) and (111)A Surfaces
Authors: Yoshiharu Yamauchi Yoshiharu Yamauchi , Kunihiko Uwai Kunihiko Uwai , Naoki Kobayashi Naoki Kobayashi
Published: October 2002

Nitridation of GaAs (001) and (111)A surfaces grown by molecular beam epitaxy (MBE) is investigated by in situ Fourier transform infrared spectroscopy. Nitridation is carried out by exposing the GaAs surface to atomic nitrogen in the same MBE chamber used for growth using a tungsten filament resistively heated to 2100°C. After nitridation for 90 minutes, the infrared reflectance spectra indicate that nitridation of the As-rich (2×4) surface at 450°C results in two IR reflectance peaks at 1200 and 1000 cm-1. On the other hand, nitridation of the Ga-rich (4×2) surface at 530°C and the (111)A surface at 490°C results in a single peak at 1200 cm-1. These results indicate that the peak at 1200 cm-1 is attributed to the Ga-N bond, and that at 1000 cm-1 to the As-N bonds. Nitrogen desorption from the nitrided surface is found to occur at 450°C and is induced by atomic hydrogen.
Effects of Oxidation on Electronic States and Photoluminescence Properties of Porous Si
Authors: Koizumi Tomohiro , Obata Koji , Tezuka Yasuhisa , Shin Shik , Nobuyoshi Koshida Nobuyoshi Koshida , Yoshiyuki Suda Yoshiyuki Suda
Published: October 2002

Oxidation states of porous Si, oxidized by oxygen excited by electron impact, have been analyzed using synchrotron radiation photoemission spectroscopy (SR-PES), Auger electron spectroscopy (AES), and Fourier transform infrared (FTIR) techniques, and the relationship between the oxidation states and PL properties has been investigated. The energy band gap, peak energy and full width at half-maximum (FWHM) of the PL spectrum are almost unchanged throughout the oxidation process. These results suggest that oxygen bonding itself basically does not affect the transition levels and that its levels are less sensitive to the surface states. The results of these analyses also imply that the skeletal structure of PS crystallites is important in PL mechanisms.
First-Principles Calculations on Mg Impurity and Mg–H Complex in GaN
Authors: Okamoto Yasuharu , Saito Mineo , Oshiyama Atsushi
Published: October 2002

First-principles calculations are performed in order to investigate the atomic geometry and stability of the Mg impurity and Mg–H complex in GaN. We find that a doped Mg atom is stable at a Ga substitutional site with only slight lattice relaxation, suggesting that the Mg impurity induces a shallow acceptor level. It is also found that this Mg impurity forms a very stable complex with an incorporated hydrogen; the hydrogen atom intervenes between the N and Mg atoms to form the stable Mg–H complex. The formation of this stable Mg–H complex is expected to be the reason for the experimental result that the acceptor is passivated by the hydrogen. Local vibrational frequencies of the Mg–H complexes are also discussed.
Effect of Growth Interruption during GaAs/AlGaAs Molecular Beam Epitaxy on (411)A Substrates
Authors: Yamada Takumi , Hiroshi Yamaguchi Hiroshi Yamaguchi , Yoshiji Horikoshi Yoshiji Horikoshi
Published: October 2002

We have studied the photoluminescent properties of AlGaAs/GaAs quantum wells grown by molecular beam epitaxy on (411)A GaAs substrates. We found that growth interruption with As supply degrades, whereas that under As-free or low-pressure As conditions improves the flatness of the heterointerface. These characteristics are very different from those for (100) GaAs substrates. The flattening transition under As-free conditions appeared to be related to Ga desorption during the growth interruption. We believe that Ga desorption plays an important role in maintaining flat (411)A surfaces.
Full-Color Fluorescent Display Devices Using a Near-UV Light-Emitting Diode
Authors: Yuichi Sato Yuichi Sato , Nobuyuki Takahashi Nobuyuki Takahashi , Susumu Sato Susumu Sato
Published: October 2002

Full-color fluorescent display devices are demonstrated using a near-UV (n-UV) light-emitting diode (LED) and various fluorescent films. ZnS:Ag (blue), ZnS:Cu,Al (green) and ZnCdS:Ag (red) powdered fluors and mixtures of them are dispersed in poly-vinyl-alcohol aqueous solutions, and fluorescent films are prepared by spin coating the suspensions to glass slides. The n-UV light emitted from a blue LED with a high injection current is irradiated onto the films, and the three primary colors and white color are easily obtained.
Double-Pass Confocal Absorption Microscope with a Phase Conjugation Mirror
Authors: Nakamura Osamu , Fujita Katsumasa , Yoshimasa Kawata Yoshimasa Kawata , Satoshi Kawata Satoshi Kawata
Published: October 2002

A new double-pass confocal absorption microscope is proposed where a phase conjugation mirror is used instead of the plane or concave mirror commonly employed in a conventional double-pass optical design. A practical system using a BaTiO3 crystal is developed to verify the effectiveness of the proposed principle. Using a diatom material as sample, a comparison is made between the image produced by our new microscope with those obtained using a conventional double-pass microscope, and a single-pass non-confocal microscope.
Direct Observation of Developed Plastic Deformation and Its Application to Nondestructive Testing
Authors: Yoshida Sanichiro , Widiastuti Suprapedi , Pardede Marincan , Hutagalong Septriyanti , S. Marpaung Julinda , A. Faizal Muhardy A. Faizal Muhardy , Anung Kusnowo Anung Kusnowo
Published: October 2002

A band pattern representing what we believe to be a developed, localized plastic deformation has been discovered in a fringe system formed by electronic speckle-pattern interferometry. Time historical tracing of this pattern enables us to predict the location and timing of material fracture before any other visible indication appears. Application of this observation to nondestructive testing is discussed.
Chemically Assisted Ion Beam Etching of GaAs/AlGaAs Using Chlorine Ions
Authors: Kawanishi Hidenori , Morioka Tatsuya , Shimonaka Atsushi , Mototaka Taneya Mototaka Taneya , Akira Suzuki Akira Suzuki
Published: October 2002

Chemically assisted ion beam etching of GaAs/AlGaAs has been studied using chlorine gas and chlorine/argon ions. The use of chlorine ions results in a very smooth surface after etching at an ion energy of 400 eV. By contrast, a porous surface appears when argon ions are used, unless the ion energy is increased to 700 eV. The smooth etching characteristics in the former case have been ascribed to the effective removal of Al2O3, which is formed on the AlGaAs surface and acts as a micromask, by chemically reactive chlorine ions.