bluuebunny/crossref_metadata_2025 huggingface dataset:
High-Power GaN P-N Junction Blue-Light-Emitting Diodes
Authors: Nakamura Shuji , Takashi Mukai Takashi Mukai , Masayuki Senoh Masayuki Senoh
Published: February 2005

High-power p-n junction blue-light-emitting diodes (LEDs) were fabricated using GaN films grown with GaN buffer layers. The external quantum efficiency was as high as 0.18%. Output power was almost 10 times higher than that of conventional 8-mcd SiC blue LEDs. The forward voltage was as low as 4 V at a forward current of 20 mA. This forward voltage is the lowest ever reported for GaN LEDs. The peak wavelength and the full width at half-maximum (FWHM) of GaN LEDs were 430 nm and 55 nm, respectively.
Fabrication of Metal-Insulator-Semiconductor Devices Using Polycrystalline Diamond Film
Authors: Kiyota Hideo , Okano Ken , Iwasaki Tatsuya , Izumiya Hiroshi , Akiba Yukio , Tateki Kurosu Tateki Kurosu , Masamori Iida Masamori Iida
Published: February 2005

Metal-insulator-semiconductor (MIS) devices have been fabricated using a polycrystalline diamond film doped with boron. The diamond film has been deposited on Si substrate by a hot-filament chemical vapor deposition method. The SiO2 film has been deposited on the diamond by a plasma-assisted CVD method and aluminum has been evaporated as a gate on the SiO2 film. The MIS capacitance was varied as a function of voltage applied between the gate and substrate. Further, the metal-insulater-semiconductor field-effect transistor has indicated transistor operation capabilities at room temperature. These results suggest a possibility that the polycrystalline diamond film can be used as an electronics material.
Anomalous Critical Temperature over 200 K in Multiphase Tl-Ba-Ca-Cu-O System
Authors: Jyodoi Kouki , Fukushima Keiji , Sonoda Akihisa , Sigeyuki Yasuyama Sigeyuki Yasuyama , Akira Ohyoshi Akira Ohyoshi
Published: February 2005

Anomalous critical temperatures of over 200 K were recorded for multiphase samples with the nominal composition of TlBa2Ca3Cu4O10.5. The formation of the samples was found to be critically dependent on the sintering temperature and time. The results of energy dispersive X-ray spectrometry (EDX) analysis showed that the atomic ratios for these samples were Tl:Ba:Ca:Cu=0.19±0.05:1.94±0.09:2.63±0.16:4.00. The X-ray photoelectron spectroscopy (XPS) spectra of Tl4f, Ba3d, Cu2p and O1s partially consisted of high-binding-energy components. We interpret them to result from an electron transfer reaction such as Tl2O3+2CuO→2Tl2O+Cu2O3.
Low-Resistivity Contact of YBa2Cu3O7-x/Al Joint Bonded at Room Temperature
Authors: Takahashi Yutaka , Eiichi Hosomi Eiichi Hosomi , Tadatomo Suga Tadatomo Suga
Published: February 2005

A joining between YBa2Cu3O7-x
and aluminum was performed at room temperature employing the surface activation method. After surfaces of both samples were sputter-cleaned by an argon beam in vacuum, activated surfaces were pressed to each other at the pressure of 96 MPa. Although the surface of YBa2Cu3O7-x
was very rough, a tight joint was obtained. Interface resistance of the joint was measured by the four-probe method. It decreased as temperature was lowered and it was as low as 6×10-9 Ω·m2 at 77 K. V-I measurement demonstrated, however, that it did not show an exactly ohmic character, but a slight positive dependence on current.
Subpicosecond Photon Echo Quantum Beats in a Dye-Doped Polymer
Authors: Shunsuke Nakanishi Shunsuke Nakanishi , Hiroshi Itoh Hiroshi Itoh
Published: February 2005

Subpicosecond photon echo quantum beats were studied in a dye, Rhodamine 800, doped in a polymer (polyvinyl alcohol) by using an incoherent photon echo technique. At the long-wavelength tail of absorption, photon echo quantum beats were observed as the sinusoidal modulation with the frequency of about 100 cm-1, which resulted from the interference between a single vibronic line and the zero-phonon line. The dephasing time of the vibronic line and its temperature dependence were briefly studied. At nearly the peak of absorption, the quantum beats appeared as more complicated modulation, indicating the contribution from multiple vibronic lines.
Change in Molecular Orientation during Thin Film Growth by Evaporation of Copolymer of Vinylidene Fluoride (80%) and Tetrafluoroethylene (20%)
Authors: Takaharu Okajima Takaharu Okajima , Kunisuke Maki Kunisuke Maki
Published: February 2005

Thin film with an orthorhombic-type polymorph was prepared by evaporating a copolymer of vinylidene fluoride and tetrafluoroethylene powder on Ag-coated glass substrate. The molecular orientation is studied by determining the
thickness dependence of the vibration absorption in the film when the p-polarized infrared rays are incident at an angle of 70°. On the substrate held at 80°C, the regions with the main chain aligned parallel to the surface becomes larger than those on nonheated substrate. This is probably due to some structural relaxation which is caused by the encounter of admolecules with each other and/or with the incoming molecules.
Pyrolysis of Organo-As Precursors Studied by Surface Photo-Absorption
Authors: Yoshiharu Yamauchi Yoshiharu Yamauchi , Naoki Kobayashi Naoki Kobayashi
Published: February 2005

Surface Photo-Absorption (SPA) is an in situ optical technique for monitoring growth processes. It can measure the dynamics of surface reaction on a growth surface. We use SPA to investigate the pyrolysis of As precursors such as organo-arsenic and arsine (AsH3), and estimate the decomposition activation energies of these As precursors. The results indicate that tertiary butylarsine (tBAs), diethylarsine (DEAsH) and AsH3 which all contain a hydrogen-As bond, have lower activation energies than might be expected from the average bond strength, indicating that their pyrolysis processes are well catalyzed by the GaAs surface. On ther other hand, trialkylarsine such as trimethylarsine (TMAs) and triethylarsine (TEAs) have high activation energies. As expected from the low activation energy, high-quality GaAs can be grown using tBAs.
The Effects of Hot Ion-Implantation on the Electrical Properties of Amorphous-Silicon Films Produced by Chemical-Vapor-Deposition Method
Authors: Satoh Tsutomu , Kanoh Hiroshi , Osamu Sugiura Osamu Sugiura , Masakiyo Matsumura Masakiyo Matsumura
Published: February 2005

Hot ion-implantation into amorphous silicon (a-Si) has been studied for chemical-vapor-deposited films. Conductivity of as high as 0.4 S/cm (100 times higher than the previous result) was achieved at the phosphorus atom concentration of 8×1020 cm-3, when the substrate temperature was elevated up to 450°C during the ion-implantation. Activation energy was 0.12 eV.
Preparation of Superconducting Niobium Nitride Films by Molecular Beam Epitaxy Method
Authors: Kenji Kawaguchi Kenji Kawaguchi , Mitsugu Sohma Mitsugu Sohma
Published: February 2005

Preparation of superconducting niobium nitride (NbN) films was attempted by two kinds of electron-beam deposition methods. One is a molecular beam epitaxy (MBE) method using a radical beam source (RBS). The other is a reactive deposition method assisted by radio frequency plasma. The films grown by the RBS-MBE method showed a clear superconducting transition. The observed maximum superconducting transition temperature (T
c) was 9.5 K.
Promotion of High-Tc Phase in Te-Doped (Bi, Pb)2Sr2Ca2Cu3Oy Superconductors Prepared by the Melt-Quenching Method
Authors: Komatsu Takayuki , Tamoto Nozomu , Sato Ryuji , Matusita Kazumasa , Sawada Kazuhiko , Yamashita Tsutomu
Published: February 2005

We prepared superconducting Bi1.6Pb0.4-x
Te
x
Sr2Ca2Cu3O
y
(x=0.1∼0.4) ceramics by the melt-quenching method and examined the effect of Te addition on the formation of the high-T
c phase. It was found that the onset temperature of partial melting for the glass sample with x=0.1 was the lowest, and the formation of the high-T
c phase was greatly promoted. The bulk ceramics with x=0.1 and 0.2 exhibited superconductivity with a critical temperature of 101∼103 K and a critical current density (77 K, zero magnetic field) of around 200 A/cm2. The main superconducting phase in the ceramics with x=0.4 was the low-T
c phase.
Electroluminescence from Visible to Near-Infrared Spectral Range in Buckminsterfullerene Diode
Authors: Uchida Masao , Yutaka Ohmori Yutaka Ohmori , Katsumi Yoshino Katsumi Yoshino
Published: February 2005

Electroluminescence in Buckminsterfullerene has been reported for the first time. The Buckminsterfullerene electroluminescent diode emits visible to near-infrared light with a dull peak at around 530 nm which corresponds to the energy much larger than the band gap energy. The origin of the wide electroluminescent spectrum has also been discussed in terms of energy band scheme.
Fabrication Technique of High Density Quantum-Wire Arrays by Photolithography and Metalorganic Chemical Vapor Deposition
Authors: Yang S. L. , Barone R. , Chen P. L. Liu
Published: February 2005

We have fabricated GaAs quantum-wire arrays by using photolithography and metalorganic chemical vapor deposition (MOCVD). Multiple quantum-wire structures with lateral dimensions less than 200 Å×1200 Å have been obtained. An area filling factor greater than 50% can be achieved.
Stress and Structural Relaxation in Metallo-Organic Chemical Vapor Deposited SiO2 Films
Authors: Seshu B. Desu Seshu B. Desu
Published: February 2005

Stress relaxation of amorphous silica films deposited by low pressure thermal decomposition of diacetoxy di-t-butoxy silane (DADBS) was studied. Significant reduction in film stress along with structural changes were observed at temperatures as low as 600°C. The activation energy for stress relaxation was found to be 75.8 kJ/mol. The low value of activation energy is attributed to the effect of water which was present in the form of silanol groups. The changes in film stress are attributed in a semi-quantitative manner to the changes in Si-O-Si angle distributions in the film.
GaAs Taper Etching by Mixture Gas Reactive Ion Etching System
Authors: Makoto Hirano Makoto Hirano , Kazuyoshi Asai Kazuyoshi Asai
Published: February 2005

A novel technique is proposed for taper-etching GaAs. The angle of the sidewalls formed by undercutting GaAs can be controlled by adjusting the ratio of He to CCl2F2 used for reactive ion etching (RIE). A negative undercut with a taper angle of 80 degrees is formed with He gas content of 95%. Etched surfaces are analyzed by micro-Auger spectroscopy. The detailed etching conditions for forming taper shapes are described and the mechanism of such formation is also discussed.
Cryogenic Scanning Tunneling Microscopy and Spectroscopy on the Cleaved Surface of Bi-Sr-Ca-Cu-O Down to 4.2 K
Authors: Hasegawa Tetsuya , Masashi Nantoh Masashi Nantoh , Koichi Kitazawa Koichi Kitazawa
Published: February 2005

Atomic resolution has been achieved by a scanning tunneling microscopy (STM) system for the first time on an oxide superconductor at cryogenic temperatures. The atomic corrugation with a periodicity of 0.35 nm and the modulation along the b-axis with a superlattice periodicity of about 2.7 nm have both been clearly observed on the cleaved a-b plane of a Bi-Sr-Ca-Cu-O single crystal. Furthermore, it is found that some features of the spectrum, including the shape of the superconducting gap, depended significantly on the distance between the probe tip and sample surface. Wide scattering of the results so far reported for various types of tunneling methods can be interpreted in terms of this distance dependence of the tunneling spectrum. We conclude that the superconducting gap structure in the spectrum is by far different from the prediction of the BCS weak-coupling theory.
Negative Differential Resistance in GaAs Delta-Doping Tunneling Diodes
Authors: Su Yan Kuin , Ruey Lue Wang Ruey Lue Wang , Yeong Her Wang Yeong Her Wang
Published: February 2005

In this letter, we show GaAs double-barrier quantum well homostructure diodes. The barrier is induced by the δn
+-i-δp
+-i-δn
+ or δn
+-i-δp
+-i-δp
+-i-δn
+ structure grown by the delta-doping technique. The conduction band diagram was simulated with the out-diffusion effect of delta-doping layers taken into consideration. The current-voltage characteristics exhibit the expected N-type negative differential resistance due to the resonant tunneling effect. The room-temperature peak-to-valley current ratios are 1.5 and 1.9 for the two studied devices, respectively.
Electrostatic Force Imaging by Tunneling Acoustic Microscopy
Authors: Takata Keiji , Takehiro Okawa Takehiro Okawa , Masatada Horiuchi Masatada Horiuchi
Published: February 2005

A new method for detecting the electrostatic force between a tip and a sample is presented. A voltage applied to the tip generates a strain which is proportional to the electrostatic force in the sample. By modulating the voltage, the strain is transmitted in the sample as a wave and is detected using a piezoelectric transducer coupled to the sample. This method, as one of the applications of tunneling acoustic microscopy(TAM), enables us to measure electrostatic forces and surface contours simultaneously. It has been proven through this measurement that force sensitivity of up to 10-11N is achieved with TAM. Electrostatic force images and topographies of an ion-implanted silicon are shown.
Photon Stimulated Desorption from Finely Polished Metals Irradiated with Synchrotron Radiation
Authors: Miyauchi Eizo , Okamura Sigeru , Taguchi Takao , Shunji Goto Shunji Goto , Tokushige Hisatsugu Tokushige Hisatsugu
Published: February 2005

Photon-stimulated desorption (PSD) from electrolytic-abrasively polished stainless steel, copper, and titanium was evaluated using synchrotron radiation (SR) in the spectral range of 1-7 A. Typical desorption yield of the finely polished samples, measured with the throughput method, ranges from 2×10-4 to 5×10-4 molecules/photon with desorption species of H2, CO and CO2. The difference in yields among the materials was quite small after considerable irradiation. We also found that the yields of electrolytically and electrolytic-abrasively polished stainless steel are almost the same, except for in the initial period of irradiation. This similarity was consistent with the result of surface inspection with XPS.
Apparent Destruction of Interference by Use of a Partial Absorber in X-Ray Interferometry
Authors: Yuji Hasegawa Yuji Hasegawa , Seishi Kikuta Seishi Kikuta
Published: February 2005

The effect of mixture of the states on the wave field is studied by means of an X-ray interferometer. When an absorber is inserted in a part of one of the splitted beams, recombined state is represented as a mixture of full and reduced oscillating states. An apparent destruction of interference was observed due to the antiphasing oscillations.
Origin of the Reduction of Light-Induced Changes in Plasma-Deposited Hydrogenated Amorphous Silicon Prepared under Visible-Light Illumination
Authors: Sakata Isao , Mitsuyuki Yamanaka Mitsuyuki Yamanaka , Yutaka Hayashi Yutaka Hayashi
Published: February 2005

Experimental studies have been carried out to clarify the origin of the reduction of light-induced changes in plasma-deposited hydrogenated amorphous silicon prepared under visible-light illumination (referred to as illuminated GD a-Si:H in this paper). The changes are smaller in the illuminated GD sample than in the a-Si:H sample deposited in the same run without the illumination even when the content and bonding mode of hydrogen are almost the same in both samples. This implies that the possible reduction of latent sites for the changes by the illumination is an essential origin of the observed reduction.
Laser Etching of Bi-Sr-Ca-Cu-O Superconducting Thin Films
Authors: Oohira Tsunehiro , Sakai Shigeki , Kasai Yuji , Nobufumi Atoda Nobufumi Atoda , Keizo Shimizu Keizo Shimizu
Published: February 2005

Laser etching of the Bi-Sr-Ca-Cu-O superconducting thin films is studied using the second harmonic light of a Nd:YAG laser (530 nm, 40 mW, 2 kHz). With use of a laser beam of high energy density, the etching speed exceeds 10 mm/s, but a region of degradation exists around etching lines and precise control of etching depth is difficult. Under the low-energy and prolonged irradiation condition, there is some enhancement of laser etching by the addition of reactive gases. The result suggests the possibility of very fine etching in a layer-by-layer manner for high T
c superconducting films by the laser assist etching.
Effect of Substrate Bias on In-Plane Uniaxial Magnetic Anisotropy in Amorphous TbCo Films Prepared by DC-Sputtering
Authors: Shiomi Shigeru , Ikeda Takashi , Makoto Koshiro Makoto Koshiro , Morio Masuda Morio Masuda
Published: February 2005

Amorphous TbCo films have been prepared by DC-sputtering. Without substrate bias, films have perpendicular anisotropy K
⊥ larger than 1×106 erg/cm3 and negligibly small in-plane uniaxial anisotropy K
// regardless of film composition. With finite substrate bias, however, K
// up to 9×105 erg/cm3 is induced in Co-rich films. The easy axis is along the magnetic field applied for increasing the ionization efficiency. Both K
// and K
⊥ depend on substrate bias voltage, applied field strength and film composition. K
// can be increased by magnetic annealing with field along the easy axis. Magnetic annealing can rotate the in-plane easy axis.
Electron Acceleration by Beat Wave of Two Gaussian Laser Beams in Vacuum
Authors: Sakai Kazuo , Ogiwara Masanori , Satoshi Takeuchi Satoshi Takeuchi , Michio Matsumoto Michio Matsumoto
Published: February 2005

The electron motions in the beat wave composed of two strong Gaussian laser beams in vacuum are numerically studied with special attention paid to the finite-diameter effects. It is shown that electrons can be strongly accelerated, if they are appropriately injected into the beat wave. The acceleration gradients are obtained for the various values of the laser amplitude. These results are discussed on the basis of the plane wave theory.
Laser-Induced Modulation of Second-Harmonic Light Emission from Ru(II)-Bipyridine Metal Complex in Langmuir-Blodgett Film*
Authors: Sakaguchi Hiroshi , Nagamura Toshihiko , Taku Matsuo Taku Matsuo
Published: February 2005

Upon Nd-YAG laser irradiation of a Langmuir-Blodgett film containing Ru(II)-bipyridine metal complex, strong second-harmonic light at 532 nm is observed. The second-harmonic light intensity is remarkably suppressed when the ruthenium complex is excited by other laser pulses (either 355 nm or 460 nm) just before Nd-YAG laser irradiation at 1064 nm. This phenomenon is ascribed to the reduction in hyperpolarizability on going from the ground state to a metal-to-ligand charge-transferred excited state. The optical modulation of SHG becomes possible, for the first time, by the aid of laser-induced electronic transition.
A Broad-Band Traveling-Wave Ti:LiNbO3 Optical Phase Modulator
Authors: Miyamoto Hiroshi , Ohta Hiroshi , Tabuse Kazuhiko , Hideto Iwaoka Hideto Iwaoka , Yoshihide Miyagawa Yoshihide Miyagawa
Published: February 2005

A new-structure traveling-wave z-cut Ti:LiNbO3 optical phase modulator with 50 Ω characteristic impedance and velocity matching without any penalty in driving voltage is designed and fabricated. The study analyzes the device structures and design parameters of the thickness of the electrodes and the buffer layers, and presents experimental results. The modulation response has been measured up to 40 GHz, and 26 GHz on a 3dB bandwidth caused by electrode losses, and the V
π of this device was 17 V at the optical wavelength of 1.5 µm.
Ferroelectric Liquid Crystal Spatial Light Modulator with Gray-Scale Capability
Authors: Gomes Cleber M. , Tsujikawa Susumu , Maeda Hiroki , Sekine Hiroyuki , Yamazaki Takashi , Sakamoto Mikio , Okumura Fujio , Shunsuke Kobayashi Shunsuke Kobayashi
Published: February 2005

Memorized gray-scale capability was demonstrated in a ferroelectric liquid crystal optically addressed spatial light modulator (OASLM) prepared by using polyimide Langmuir-Blodgett films for the orientation of the liquid crystal.
Use of a ReO3 Single Crystal as the Tip for Scanning Tunneling Microscopy
Authors: Ikebe Shin-ichiro , Shimada Daisuke , Akahane Takashi , Nobuo Tsuda Nobuo Tsuda
Published: February 2005

A corner of a ReO3 single crystal was used as the tip for scanning tunneling microscopy (STM). The atomic arrays of graphite and ReO3 were easily observed. The image of the emissive area is round in the former and polygonal in the latter, reflecting, perhaps, the electron distribution in the uppermost band.
An In-Process X-Ray Measuring System with a Heat-Resistant Filter Transmitting Soft X-Rays for Light Elements
Authors: Nakahara Takehiko , Koshinaka Masao , Shinji Badono Shinji Badono , Toshimasa Tomoda Toshimasa Tomoda
Published: February 2005

We constructed a RHEED-Si (Li) SSD measuring system which has the capability to detect, in-process, characteristic X-rays emitted from light elements such as oxygen. The feature of the system is that the X-ray detecting system uses a heat-resistant filter made of an Al film and a BN film in front of the SSD. The filter transmits soft X-rays and blocks light and heat radiation which emanate from processes and influence the SSD performance. It was demonstrated that the measuring system could detect change in the O-Kα X-ray intensity from a SiO2/Si(100) sample when it was heated to and kept at 500°C.
Fabrication of MOS Nanostructure by Employing Electron Beam Lithography and Anisotropic Wet Etching of Silicon
Authors: Kazuhiro Shimizu Kazuhiro Shimizu , Shunri Oda Shunri Oda
Published: February 2005

Ultrafine metal/SiO2/Si (MOS) structures have been fabricated by combining the technologies of electron beam lithography and anisotropic wet etching of Si. The etching condition has been optimized in terms of the composition of the etchant and temperature. A MOS structure of narrower than 20 nm with specular sidewalls has been obtained, which will be useful for the application of ultrasmall devices such as quantum effect transistors of Si.
Atomic Layer Epitaxy of AlAs and (AlAs)n(GaAs)n Superlattices Using Dimethylaluminumhydride as the Al Source
Authors: Ishizaki Mamoru , Kano Nobuo , Junji Yoshino Junji Yoshino , Hiroshi Kukimoto Hiroshi Kukimoto
Published: February 2005

Atomic layer epitaxy (ALE) of AlAs has been achieved by using nominally pure dimethylaluminumhydride as the Al source, instead of its mixing with trimethylaluminum which was used in our previous ALE growth of ALE. Short period superlattices of (AlAs)
n
(GaAs)
n
with n=3, 5 and 10 have been fabricated at 470°C entirely by ALE, for the first time. The periodicity observed by X-ray diffraction measurements was as designed for these superlattices.
Metalorganic Vapor Phase Epitaxy of CuGa(SxSe1-x)2 Lattice-Matched to GaP (100)
Authors: Hara Kazuhiko , Shinozawa Taro , Junji Yoshino Junji Yoshino , Hiroshi Kukimoto Hiroshi Kukimoto
Published: February 2005

CuGa(S
x
Se1-x
)2 epitaxial layers were grown on GaP (100) substrates by metalorganic vapor phase epitaxy. The alloy composition of the grown layers was controlled by the transport rates of H2S and H2Se. A dramatic improvement in the crystalline quality of the CuGa(S
x
Se1-x
)2 layer lattice-matched to the substrate was evidenced by the narrow linewidth of the double-crystal X-ray rocking curve and the smooth surface. The lattice-matching conditions can be discussed in terms of crystal orientation, lattice parameter and thermal expansion coefficient.
Effect of Ni Substitution for Cu in 110 K Phase of (Bi, Pb)-Sr-Ca-Cu-O Superconductors
Authors: Natsume Hidetaka , Kishimoto Takeshi , Enomoto Hiroyuki , Shin Jae Soo , Takano Yoshiki , Mori Natsuki , Hajime Ozaki Hajime Ozaki
Published: February 2005

The effect of Ni substitution for Cu in the 110 K phase of (Bi, Pb)-Sr-Ca-Cu-O superconductor was investigated. Samples of Bi1.84Pb0.34Sr1.91Ca2.03(Cu1-x
Ni
x
)3.06O
y
were prepared. The single phase was obtained up to a Ni concentration of x=0.015. The zero-resistance temperature T
c decreased monotonically in the region of x≤0.03 and became 90 K at x=0.03. T
c remained constant at 89 K in the region of 0.03<x≤0.10. Through X-ray photoelectron spectroscopy measurements, the Cu 2p core level was found to shift toward lower binding energy with the increase of x, which shows the Ni substitution for Cu.
Bi2(Sr, Ca)3Cu2Ox and Bi2(Sr, Ca)4Cu3Ox Thin Films with (11n) Orientation
Authors: Kuroda Ken'ichi , Wada Osamu , Kojima Kazuyoshi , Tanimura Junji , Kataoka Masayuki , Takami Tetsuya , Yokoyama Kazuo , Ogama Tetsuo , Koichi Hamanaka Koichi Hamanaka
Published: February 2005

As-grown Bi2(Sr, Ca)3Cu2O
x
and Bi2(Sr, Ca)4Cu3O
x
thin films with the (11n) orientation were formed on SrTiO3(110)
substrates by consecutive sputtering. RHEED patterns and XRD analysis indicated that the c-axis of the Bi2(Sr, Ca)3
Cu2O
x
and Bi2(Sr, Ca)4Cu3O
x
films are tilted against the substrate surface by approximately 41° and 45°, respectively.
The Bi2(Sr, Ca)3Cu2O3 film was found to have mainly a (117) orientation, whereas the Bi2(Sr, Ca)4Cu3O
x
film is considered to have mainly a (1110) orientation.
Electro-Optical Q-Switched Tunable Forsterite Laser
Authors: Sugimoto Akiko , Segawa Yusaburo , Nobe Yukio , Yamagishi Kiyoshi , Yamaguchi Yasuhide
Published: February 2005

The tunable Q-switching operation of forsterite (Cr:Mg2SiO4) laser was demonstrated. The typical Q-switched pulse was 60 ns to 80 ns in width, varied with lasing wavelength. A smooth tuning curve that extends from 1206 nm to 1264 nm was obtained.
High Speed Cleaning of Boronized Wall with a CF4 Containing Plasma
Authors: Toyoda Hirotaka , Hanami Atsuo , Masashi Yamage Masashi Yamage , Hideo Sugai Hideo Sugai
Published: February 2005

Rapid cleaning of boron-thin-film deposited walls with use of a CF4 containing plasma was demonstrated. An extremely high removal rate (∼40 Å/min) of the films was obtained by a dc glow discharge of a CF4 and H2 mixture. Moreover, a 2-3% addition of oxygen enhanced the removal rate by a factor of two, which is about two orders of magnitude larger than that obtained by a conventional H2 discharge. The mass spectroscopic measurement revealed that the film is removed as BF3. The time evolution of gas composition during the cleaning suggests that the oxygen addition suppresses the surface coverage with carbon layers.
Growth of Tungsten Film by Focused Ion Beam Induced Deposition
Authors: Takahashi Yoshio , Yuuichi Madokoro Yuuichi Madokoro , Tohru Ishitani Tohru Ishitani
Published: February 2005

Growth of tungsten film by focused-ion-beam (FIB) induced deposition is studied using scanning electron microscope. A 30 kV Ga+ beam with a current density of 14 mA/cm2 is used to deposit a tungsten film on a SiO2 substrate in a tungsten hexacarbonyl (W(CO)6) gas environment. The resistivity of the film shows a sharp decrease around a dose of 0.6×1017 cm-2, and the resistivity becomes almost constant (at about 120 µΩ·cm) at a larger dose. The film has island structures during the early stages of deposition. The sharp decrease in its resistivity corresponds to coalescence of the islands.
Direct Observation of Strain Distribution in InP/In1-xGaxP Heterointerfaces by the Compositional Analysis by Thickness Fringe Method
Authors: Itoh Hiroshi Kakibayashi
Published: February 2005

Compositional analysis by the thickness-fringe (CAT) method is applied to evaluate the strain distribution at the InP/In1-x
Ga
x
P heterointerface in the direction of epitaxial growth. It has been found that the strain due to the lattice mismatch between In1-x
Ga
x
P and InP is clearly detectable as a bending of the equal-thickness fringe in the CAT image. The crystal planes in the strain field bend as a result of lattice distortion, causing both change in the Bragg condition of the electron diffraction and fringe bending. The fringe bending depends on the amount of lattice mismatch. The strain distribution is analyzed by comparing observed and simulated CAT images. The CAT method is also useful for evaluating the strain distribution with a high spatial resolution.
Preparation and Properties of InxGa1-xAs Microcrystallites Embedded in SiO2 Glass Films
Authors: Tsunetomo Keiji , Masaki Yamamoto Masaki Yamamoto , Yukio Osaka Yukio Osaka
Published: February 2005

In
x
Ga1-x
As microcrystallites were successfully doped into SiO2 glass films by the rf-magnetron sputtering technique. These microcrystallites exhibited a variety of narrow band-gap structures which were affected not only by the quantum size effect but by the composition of these microcrystallites. The composition of the microcrystallite in these films depended on the sputtering target composition, and the average diameter of In
x
Ga1-x
As microcrystallites estimated from X-ray diffraction spectra was controlled by the substrate temperature. The optical absorption spectra of these films clearly exhibited the shift of the absorption edge caused by the quantum size effect.
Signal Observation from a Pulsed Ionization Chamber Filled with Tetramethyl Germanium
Authors: Yuta Haruo , Abe Koya , Hasegawa Katsuo , Suekane Fumihiko , Neichi Kazushi , Katayama Jimitsu , Higuchi Masato , Hoshi Yoshimoto , Masuda Kimiaki , Doke Tadayoshi , Kikuchi Ryusaburo , Miyano Kazumasa
Published: February 2005

Ionization signals from 207Bi conversion electrons were observed in a pulsed ionization chamber filled with purified tetramethylgermanium liquid. The free ion yield at zero field was measured as 0.57. The lifetimes of drifting electrons in the liquid were measured as 0.99, 3.99 and 4.32 µs for increasing purification cycles.
Representative Figure Method for Proximity Effect Correction
Authors: Abe Takayuki , Yamasaki Satoshi , Ryoichi Yoshikawa Ryoichi Yoshikawa , Tadahiro Takigawa Tadahiro Takigawa
Published: February 2005

A new concept for proximity effect correction (the representative figure method) is proposed in order to greatly reduce the correction time. The method assigns only one representative rectangle within a small area whose size is sufficiently smaller than the backscattering range of electrons. Proximity effect correction is carried out by using representative figures instead of the original patterns. This method eliminates the pattern density dependence of the correction time because the pattern density of the representative figures does not exceed the number of small areas. The relative error caused by the representative figure method is at most ±1% for a Ghost-scheme exposure and ±3-4% for the dose correction method.
Slow Positron Pulsing System for Variable Energy Positron Lifetime Spectroscopy
Authors: Suzuki Ryoichi , Kobayashi Yoshinori , Mikado Tomohisa , Ohgaki Hideaki , Chiwaki Mitsukuni , Tetsuo Yamazaki Tetsuo Yamazaki , Takio Tomimasu Takio Tomimasu
Published: February 2005

A positron pulsing system has been constructed for variable energy positron lifetime spectroscopy. The system consists of a reflection type chopper, a sub-harmonic prebuncher, and a double harmonic buncher. By operating the system with an intense slow positron beam generated by an electron linac, positron lifetime spectra have been successfully measured in an extended time range of more than 45 ns with a good time resolution (250 ps). Furthermore, Doppler broadening profiles of annihilation radiations can be obtained simultaneously with the lifetime measurements.
1H Nuclear Magnetic Resonance Study of Hydrogen Distribution in Partially Deuterated Hydrogenated Amorphous Silicon
Authors: Hayashi Shigenobu , Hayamizu Kikuko , Mashima Satoshi , Suzuki Atsushi , Mcelheny Peter J. , Yamasaki Satoshi , Matsuda Akihisa
Published: February 2005

Hydrogen distribution in partially deuterated hydrogenated amorphous silicon has been studied by means of 1H nuclear magnetic resonance. It has been demonstrated that the incorporation of D atoms changes the H distribution in the film.
Dynamics of Resonant Tunneling in Double-Barrier Structures with Trapezoidal Potential Profile
Authors: Inaba Hirokazu , Nakagawa Jun , Kou Kurosawa Kou Kurosawa , Masahiro Okuda Masahiro Okuda
Published: February 2005

We investigate time-dependent tunneling of wave packets through double-barrier structures by taking into account that the effective mass of electrons in the barriers is different from that in the well. Time-dependent Schrödinger's equation, using effective mass approximation, is solved numerically. We show that the dynamics of resonant tunneling are significantly influenced by the effective mass in the barriers.
Flux Creep, Pinning Potential and Critical Current Density in Bi2Sr2Ca1Cu2Ox Single Crystals
Authors: Nagano Yoshihisa , Tatsuhiko Fujii Tatsuhiko Fujii , Junji Shirafuji Junji Shirafuji
Published: February 2005

Flux creep characteristic at 4.4 K in Bi2Sr2Ca1Cu2O
x
single crystals grown by flux method has been measured as a function of magnetic field applied parallel to the c-axis. The logarithmic relaxation rate of the magnetization dM/d ln t is analyzed on the basis of the flux creep model in combination with an extended Bean's critical state model in which n-th power dependence (0≤n≤1) of critical current density on magnetic field is assumed. The pinning potential and the zero-temperature critical current density are estimated to be 0.014∼0.056 eV and 104∼105 A/cm2, respectively, depending on oxygen partial pressure of the crystal growth environment.
BiSrCaCuO Thin Film Grown on SrTiO3 Substrate with Off-Oriented (110) Surface
Authors: Kuroda Ken'ichi , Wada Osamu , Tanimura Junji , Kojima Kazuyoshi , Takami Tetsuya , Kataoka Masayuki , Ogama Tetsuo , Koichi Hamanaka Koichi Hamanaka
Published: February 2005

A Bi2(Sr, Ca)3Cu2O
x
thin film with the (117) orientation was formed on a slightly off-oriented (110) SrTiO3 substrate by single-target sputtering. The (110) substrate off-oriented by 5° is considered to have limited film growth in one direction. From RHEED and cross-sectional TEM observations, it was found that the c-axis of the film tilts against the substrate surface by 46-47° and the SrTiO3(110) plane by 41-42°. Also, the surface morphology observed by SEM has been much improved.
An Ultimately Low-Threshold Semiconductor Laser with Separate Quantum Confinements of Single Field Mode and Single Electron-Hole Pair
Authors: Yamamoto Masamichi Yamanishi
Published: February 2005

A novel semiconductor surface-emitting laser structure is proposed. All spontaneous emission is coupled into a single lasing mode by means of a quantum microcavity, and discrete electron-hole pair emission is made free of absorption by means of a dc-biased quantum dot. The quantum microcavity modifies the angle distribution of a vacuum field fluctuation that is a source of spontaneous emission. The dc-biased quantum dot separates the emission and absorption lines by image-charge-induced change in the electric field. The threshold current of such a semiconductor laser can be reduced to below 100 nA.
Current versus Light-Output Characteristics with No Definite Threshold in pnpn Vertical to Surface Transmission Electro-Photonic Devices with a Vertical Cavity
Authors: Numai Takahiro , Sugimoto Mitsunori , Ogura Ichiro , Hideo Kosaka Hideo Kosaka , Kenichi Kasahara Kenichi Kasahara
Published: February 2005

We demonstrate surface-emitting laser operation in pnpn structure vertical to surface transmission electro-photonic devices (VSTEPs) with a vertical cavity, i.e., VC-VSTEPs. Continuous-wave (cw) laser operation at room temperature is achieved with a VC-VSTEP mounted directly on a glass sheet with no heat sink. The threshold current is 3 mA for a 10 µm square device. In pulsed operation, this device shows current vs light-output characteristics with no definite threshold. The light output spectrum shows single mode operation in which the spectral width is the same value as the resolution of a spectrometer.
Fabrication and Characteristics of Schottky Gated Poly(3-alkylthiophene) Field Effect Transistors
Authors: Ohmori Yutaka , Takahashi Hiroyuki , Muro Keiro , Uchida Masao , Tsuyoshi Kawai Tsuyoshi Kawai , Katsumi Yoshino Katsumi Yoshino
Published: February 2005

Fabrication and characterization of Schottky gated poly(3-alkylthiophene) field effect transistors have been reported. The transistors have been realized using free-standing poly(3-alkylthiophene) films with Schottky gated electrode configuration with low drive voltages. From the FET characteristics, the carrier mobility is evaluated to be 3×10-3 cm2/V·s.
Electric-Field-Dependent Tilt (Cone) Angle in a Chiral Smectic C Liquid Crystal Showing Electroclinic Effect in the Smectic A Phase
Authors: Yang Ying-Bao , Mochizuki Akihiro , Naoto Nakamura Naoto Nakamura , Shunsuke Kobayashi Shunsuke Kobayashi
Published: February 2005

A liquid crystal mixture (764E, BDH) exhibiting a remarkable electroclinic effect in the smectic A phase is shown to reveal a fairly large electric-field-dependent tilt (cone) angle in the chiral smectic C phase. A phenomenological theory called the Garoff-Meyer-Okano theory is successfully applied to explain the observed results qualitatively.
Preparation of Plasma Chemical Vapor Deposition Silicon Nitride Films from SiH2F2 and NH3 Source Gases
Authors: Watanabe Nobuaki , Yoshida Mamoru , Jiang Yi-Chao , Tutomu Nomoto Tutomu Nomoto , Ichimatsu Abiko Ichimatsu Abiko
Published: February 2005

Fluorinated silicon nitride films are prepared by plasma chemical vapor deposition (PCVD) of the difluorosilane (SiH2F2)-ammonia (NH3) system. The films deposited with varied gas-phase composition were characterized by means of infrared spectroscopy (IR) and Auger-electron spectroscopy (AES). It is shown that the deposition rate, refractive index and density of silicon nitride films depend on the SiH2F2-NH3 ratio of the input gases. It is further shown that the stress, resistivity and dielectric breakdown strength do not depended on it. The resistivity and breakdown strength were observed to be as high as 1016 Ω·cm and 5 MV/cm, respectively.
Preferential Sputtering of Oxygen from SiO2 by Low-Energy Ion Beam and Neutral Beam Bombardment
Authors: Tatsumi Mizutani Tatsumi Mizutani
Published: February 2005

Rutherford backscattering and Auger-electron spectroscopy measurements reveal that low-energy (500 eV) neutral Ne° beam bombardment on a SiO2 surface does not cause preferential sputtering of oxygen, whereas Ne+ ion beam bombardment of the same energy causes significant preferential sputtering. The results strongly suggest that the ionic charge plays the dominant role in the preferential sputtering of oxygen from SiO2. In addition, neutral-beam bombardment modifies the SiO2 surface to be resistant to reduction by the subsequent ion beam bombardment. It is argued that neutral-beam bombardment produces densified SiO2.
Preparation of Highly Soluble N-Substituted Polyanilines and Their Novel Solvatochromism
Authors: Oka Osamu , Yoshino Osamu Kiyohara
Published: February 2005

Poly(N-dodecylaniline), poly(N-dodecylaniline-co-aniline) and poly(N-octanoylaniline-co-aniline) were prepared from reduced polyaniline using the elimination reaction of hydrogen halide of 1-bromododecane or octanoyl chloride. They are soluble in several organic solvents. Solvatochromic shifts of spectra of their solutions have been observed and analyzed in terms of various solvent parameters. The linear relationships between the energy of absorption maxima and donor number of solvents or Taft's β parameters have been found. Color changes of solutions are explained by the changes in solute-solvent interactions.
Optical Induced Insolubilization of Soluble Conducting Polymer by Doping and Its Application for Recording
Authors: Yoshino Katsumi , Sugimoto Hiroyuki Takahashi
Published: February 2005

Soluble conducting polymer such as poly(3-alkylthiophene) has been found to become insoluble by induced doping upon light irradiation. Application of this phenomenon for optical recording has been proposed.
Enhanced Thermal Oxidation of Silicon by UV-Irradiation
Authors: Ishikawa Yutaka , Shibamoto Tsuyoshi , Takeshi Uchihara Takeshi Uchihara , Ichiro Nakamichi Ichiro Nakamichi
Published: February 2005

Silicon can be thermally oxidized at low temperatures under dry O2 or N2O flow with UV-irradiation. The oxide thickness is about 9.0 nm in 4 h at 500°C on dry O2+UV oxidation. The oxide formed by dry O2+UV is thicker than that formed by N2O+UV at a relatively long oxidation time. The main oxidation species are ozone for dry O2+UV and excited-state 1D oxygen atoms for N2O+UV. The quality of oxide film formed by dry O2+UV is equal to that formed by common oxidation in dry O2 without UV.
Low Threading Dislocation Density GaAs on Si(100) with InGaAs/GaAs Strained-Layer Superlattice Grown by Migration-Enhanced Epitaxy
Authors: Kazuhiko Nozawa Kazuhiko Nozawa , Yoshiji Horikoshi Yoshiji Horikoshi
Published: February 2005

This paper reports on a new approach for reducing the threading dislocation density in GaAs on Si. We have used In
x
Ga1-x
As/GaAs strained-layer superlattices (SLSs) grown on GaAs/Si at 300°C by migration-enhanced epitaxy as threading dislocation barriers. Different from conventional high-temperature-grown SLSs, the low-temperature-grown SLSs are only slightly relaxed by misfit dislocation formation at GaAs/SLS interfaces. Thus, considerable strain can be accumulated in SLS. In addition, new threading dislocation generation due to the misfit dislocation can be suppressed. These factors lead to effective threading dislocation bending and to significant reduction in the dislocation density. For the samples with a SLS of x=0.3, the average etch-pit density is 7×104 cm-2, which is the lowest value ever reported.
Fabrication of a-Si:H Thin Film Transistors on 4-inch Glass Substrates by a Large Area Ion Doping Technique
Authors: Yoshida Akihisa , Nukayama Masaaki , Andoh Yasunori , Masatoshi Kitagawa Masatoshi Kitagawa , Takashi Hirao Takashi Hirao
Published: February 2005

We developed a large area ion doping apparatus with an rf ion source of 50 cm in diameter. Charge accumulation during ion doping was suppressed by using a double grid. We fabricated a-Si:H TFT's on a 4-inch glass substrate by using the doping apparatus. By optimizing the thickness of the passivation film of TFT's, a field effect mobility, threshold voltage and an ON/OFF current ratio of 0.6 cm2/V·s, 4.9 V and 107, respectively, were obtained. We confirmed the uniformity of electrical properties for TFT's on 4-in. glass substrates to be about ±2%. These characteristics of TFT's are suitable for switching elements in a large area LCD.
Initial Stages of GaAs Molecular Beam Epitaxy Growth on Porous Si
Authors: Maehashi Kenzo , Sato Masamichi , Hasegawa Shigehiko , Nakashima Hisao , Ito Toshimichi , Hiraki Akio
Published: February 2005

The initial stages of GaAs films on porous Si grown by molecular beam epitaxy (MBE) have been investigated using reflection high-energy electron diffraction and ultraviolet photoemission spectroscopy. We found that the surface morphology of porous Si layers was deteriorated by annealing both with and without arsenic exposure, resulting in highly microfaceted surfaces and causing large-size island formation at the initial stages of MBE growth. Such deterioration is considered to introduce numerous defects in GaAs/porous Si interfaces.
Magnetic Detector Using Bi-Pb-Sr-Ca-Cu-O Superconductive Film
Authors: Tsukamoto Keizou , Shimojima Hiromasa , Mamoru Ishii Mamoru Ishii , Chitake Yamagishi Chitake Yamagishi
Published: February 2005

The Bi-Pb-Sr-Ca-Cu-O film prepared by rf magnetron sputtering was annealed at 780°C for 2 h and 828°-847° for 160 h (two-step annealing). The obtained film made use of a magnetic detector, based on the magnetoresistive effect in the oxide superconductor. Sensitivity to a magnetic field was measured for the obtained films. The 842°C annealed film showed an excellent property as a magnetic detector, and its magnetic field resolution estimated from the sensitivity to the magnetic field and the voltage noise was 1.82×10-6 G/√Hz at 100 Hz. This film was mainly composed of plate like crystals which were partially parallel and partially perpendicularly oriented to the surface of the MgO substrate. It is considered that the grain boundaries between the grains with different crystal axes act as weak links in this compound.
Preparation of BiSrCaCuO Superconducting Thin Film by Molecular Beam Epitaxy with NO2
Authors: Ogihara Mitsuhiko , Hitoshi Abe Hitoshi Abe , Tomoyuki Yamada Tomoyuki Yamada
Published: February 2005

A BiSrCaCuO superconducting thin film was prepared in situ by molecular beam epitaxy with nitric dioxide gas (NO2). Metal sources were coevaporated onto the MgO (100) substrate at the substrate temperature of ∼700°C under the background pressure of the growth chamber of ∼5×10-6 Torr. The deposition speed was ∼1.8 Å/s and the thickness of the thin film was ∼3000 Å. The zero resistance was obtained at 65 K without the annealing steps. The quality of the BiSrCaCuO superconducting thin film prepared with NO2 is comparable to that prepared with distilled ozone under identical growth condition except for the distilled ozone flux intensity. Oxidation behaviors of NO2 were studied and are compared with those of distilled ozone.
Microstructure and Microwave Properties of YBa2Cu3O7-δ Thin Film on CaNdAlO4(001)
Authors: K. H. Young K. H. Young , G. V. Negrete G. V. Negrete
Published: February 2005

High-quality YBa2Cu3O7-δ thin films have been grown on CaNdAlO4 (001) substrates by in situ laser ablation. The best transition temperature determined by AC susceptibility midpoint was 88.3 K with a critical current density of 1.0×106 A/cm2 at 77 K. The full width at half maximum of the X-ray rocking curve of the YBCO (004) peak was 0.33°. The film crystallinity was slightly worse than those grown on LaAlO3 and NdGaO3 judging from electron channeling pattern. A 2.3 GHz resonator made from a YBCO film on CaNdAlO4 exhibited a low power Q of 3,945 which is worse than films on LaAlO3 (Q∼18,000) and also lower than the expected value from loss tangent data.
Laser Excitation Effects on Laser Ablated Particles in Fabrication of High Tc Superconducting Thin Films
Authors: Chiba Hiroshi , Murakami Kouichi , Eryu Osamu , Shihoyama Kazuhiko , Mochizuki Takayasu , Kohzoh Masuda Kohzoh Masuda
Published: February 2005

Improvement in the characteristics of YBa2Cu3O
y
superconducting thin films was performed by a second laser irradiation method. Particles in the laser ablated plume were decomposed and/or excited by the second laser irradiation. By controlling a time delay of the second laser from the ablation laser, ablated particles with average velocities of 1×106 cm/s and 2×105 cm/s were irradiated with the second laser. Notable improvement was observed when the slower ablated particles were irradiated with the second laser.
119Sn-Mössbauer Study on the Normal Lattice Vibration of Superconducting Bi(Pb)2Sr2Ca2Cu3Sn0.015O10-y
Authors: Nishida Tetsuaki , Katada Motomi , Miura Norio , Deshimaru Yuichi , Otani Tetsuya , Yamazoe Noboru , Matsumoto Yasukuni , Yoshimasa Takashima Yoshimasa Takashima
Published: February 2005

The119Sn-Mössbauer spectrum of superconducting Bi(Pb)2Sr2Ca2Cu3Sn0.015O10-yceramic, having theTcof 108 K, consists of an intense doublet peak with the δ of 0.18 mm·s-1and the Δ of 1.01 mm·s-1at room temperature. The δ and Δ indicate that the Sn4+is substituted for the copper ion in the triangular CuO3site of the CuO4layer. The δ and the absorption area increase gradually with decreasing temperature and become saturated at about 30 K, being consistent with the theoretical curves obtained from the “combined Debye and Einstein model”. Only the normal vibration without the softening is observed in the CuO4layer.
A Convenient Method for Estimating the Inclination of Recorded Magnetization Using the Bitter Technique
Authors: Osamu Kitakami Osamu Kitakami
Published: February 2005

A simple method for estimating the inclination of recorded magnetization using the Bitter technique is proposed. Based on the theory of Bitter pattern evolution, the pattern of a recording medium with inclined magnetization is calculated. The pattern generally becomes asymmetric with respect to recording transitions after applying an external field during the pattern evolution. The pattern only becomes symmetric, however, when the field is in the direction determined by the inclination of recorded magnetization. Measuring this field direction enables us to determine the inclination of the recorded magnetization.