bluuebunny/crossref_metadata_2025 huggingface dataset:
Cross-Sectional Transmission Electron Microscopy Observations and Selected-Area Electron Diffractions of Interfaces of Epitaxially Grown Diamond Thin Films on Cubic Boron Nitride Substrates
Authors: Tadashi Tomikawa Tadashi Tomikawa , Shin-ichi Shikata Shin-ichi Shikata
Published: February 2005

Diamond thin films grown from low-pressure methane-hydrogen gas mixture utilizing microwave plasma-enhanced chemical vapor deposition (CVD) on sintered polycrystalline cubic boron nitride (c-BN) substrates were examined by conventional and high-resolution transmission electron microscopy (TEM) techniques and also by the selected-area transmission electron diffraction (SATED) technique. On different planes of c-BN, such as (311), (310) and (211), epitaxial growth of diamond films was confirmed. The dislocations correspond to the mismatching of the lattice constants of diamond and c-BN were observed. One dislocation appeared per 82 to 84 diamond lattice planes. Due to the small grain size of the c-BN polycrystalline substrate, other defects, such as micro-twins, slips and stacking faults, were not observed at the interfaces in this investigation.
Preparation of Pb(Zr, Ti)O3 Films on Pt/Ti/Ta Electrodes by Sol-Gel Process
Authors: Sameshima Katsumi , Nakamura Takashi , Hoshiba Kazuhiro , Nakao Yuichi , Kamisawa Akira , Atsuki Tsutomu , Soyama Nobuyuki , Ogi Katsumi
Published: February 2005

PbZr
x
Ti1-x
O3 (PZT) films were prepared on Pt, Pt/Ti or Pt/Ti/Ta electrodes by the sol-gel process using rapid thermal annealing (RTA). In the case of Pt and Pt/Ti electrodes on poly-Si, thermal treatments of PZT films gave rise to interdiffusion between Pt and Si. This exerted an unfavorable influence on the preparation of PZT films with perovskite structure. The barrier effect of Ta films and the effect of Ti films on the crystallization of PZT films were investigated by X-ray diffraction (XRD) and Auger electron spectroscopy (AES). The electrical properties such as dielectric constants and P-E hysteresis curves were measured for PZT films with various Zr/Ti ratios on Pt/Ti/Ta/SiO2/Si(100) substrates.
Dielectric Properties of Lead Zirconate Titanate Thin Film Fabricated on In2O3:Sn Substrate by Sol-Gel Method
Authors: Ohya Yutaka , Toshimasa Tanaka Toshimasa Tanaka , Yasutaka Takahashi Yasutaka Takahashi
Published: February 2005

Lead zirconate titanate (PZT) films with the composition of Pb(Zr
x
Ti1-x
)O3 (x: 0.2-0.8) were fabricated by dip-coating methods. The sol was prepared using ethanolamine as a sol stabilizer. The substrate was In2O3:Sn (ITO) sputtered glass (Corning #7059). PZT was well crystallized by heating at 600°C. After heating, the interface between PZT and ITO was investigated in structural, chemical, and electrical respects. These tests revealed that there is no reaction layer or diffusion layer between the interface. The dielectric constant and loss factor of the films were measured against temperature. From the D-E hysteresis curves, the films were confirmed to be ferroelectric with P
r=5 µC/cm2 and E
c=85 kV/cm.
Critical Current Enhancements in Silver-Clad Bi2Sr2CaCu2Ox Wires Using a Statistical Experimental Design for Heat Treatment Optimization
Authors: Jeffrey C. Bowker Jeffrey C. Bowker , Graham A. Whitlow Graham A. Whitlow
Published: February 2005

A statistically designed experiment was performed to determine the heat treatment conditions giving the highest critical current for single-filament powder-in-tube wires of commercial Bi2Sr2CaCu2O
x
in silver. The variables studied were temperatures of partial melting, temperature of annealing, and duration of anneal. The highest critical currents were obtained when low heat treatment temperatures were used, partial melting at 870°C and annealing at 790°C for 200 h. The highest current obtained was 455 A, corresponding to a critical current density, at 4.2 K and no magnetic field, of about 57000 A/cm2.
Computer-Aided Design of Waveguide Gratings Having Asymmetric Reflectivity Spectra
Authors: Wu Jie , Takashi Kondo Takashi Kondo , Ryoichi Ito Ryoichi Ito
Published: February 2005

An optimization technique for computer-aided design of waveguide gratings is developed to obtain asymmetric reflection characteristics. The optimal grating pattern is constructed by modulating the phase of a dense periodic grating with a complex-valued function. The modulation function is quantized with respect to its phase and represented by a digital vector. The optimization is carried out by simulated annealing. An example of design is presented. Better results are obtained by selecting a larger number of quantized phase levels.
Quadrupled Compact Disk-Read Only Memory Fabricated Using UV Light Source
Authors: Katsuda Shinichi , Ishizuka Kenichi , Ohmura Naoki , Takahashi Junichi , Yokota Hitoshi , Yamada Kazuhiko
Published: February 2005

Quadrupled compact disk-read only-memory (CD-ROM) mastering processes with a 363.8 nm UV light source have been developed. The UV light source exposure power for pit formation is less than that for the 457.9 nm conventional light source, because the photoresist exposure characteristic depends on light source wavelength. The fabricated disk exposed by EFM signals with doubled-linear-density CD format has a 0.8 µm track pitch and about 0.25 µm pit width. Under optimum fabrication exposure power for reduced crosstalk and better modulation amplitude, an excellent jitter value, 10 ns, is achieved for the quadrupled CD-ROM.
Nitrogen Doping of ZnSe and ZnCdSe with the Assistance of Thermal Energy and Photon Energy
Authors: Matsumoto Shigeyuki , Tosaka Hiroyuki , Yoshida Takashi , Masakazu Kobayashi Masakazu Kobayashi , Akihiko Yoshikawa Akihiko Yoshikawa
Published: February 2005

Two methods were examined for doping nitrogen into ZnSe and ZnCdSe. N2 gas was thermally excited in the first method. The photoluminescence (PL) spectra showed that acceptor levels were formed in the film; this feature was similar to that observed in the samples doped with nonexcited N2 gas. The second method utilized photoexcited N2O and N2 gases using vacuum ultraviolet (VUV) light. A deuterium lamp was used for the VUV-light source. Deep-emission-dominant PL spectra were observed when films were doped using photoexcited N2O gas. N2O gas was then mixed with N2 gas to control the photodecomposition process and improve the film quality. Samples doped using the mixed gas exhibited well-resolved near-band-edge features. The PL spectrum of the Zn0.9Cd0.1Se sample doped using the photoexcited mixed gas showed donor-acceptor pair emission.
Wafer Temperature Measurement and X-Ray Mask Temperature Evaluation in Synchrotron Radiation Lithography
Authors: Chiba Akira , Motonobu Futagami Motonobu Futagami , Koichi Okada Koichi Okada
Published: February 2005

Temperature rises in a wafer and an X-ray mask membrane have been investigated by means of synchrotron radiation (SR) lithography, using, respectively, experimental and theoretical methods. When considering temperature rise in an X-ray mask, the wafer has been assumed to act as a heat-sink during exposure. In-situ temperature measurement was performed using a wafer with an embedded thermocouple at a 200 mA beam current. The temperature rise to be measured was simulated by a heating model based on a lumped heat capacity system. It was found that SR exposure increased the wafer temperature as well as that of the X-ray mask membrane. The assumption that the wafer acts as a heat-sink during exposure is not valid. The mask temperature rise of ∼0.3°C is estimated from the wafer temperature measurement.
The Effect of Nonuniform Doping Density on Electron States in n-Type Si Inversion Layers
Authors: Shinji Muramatsu Shinji Muramatsu , Toshiyuki Toriumi Toshiyuki Toriumi
Published: February 2005

Self-consistent numerical calculations of coupled Poisson and Schrödinger equations have been performed for electron states in n-type inversion layers on p-type silicon with a nonuniform doping density. The merits of a steplike doping profile consisting of low- and high-density regions are discussed.
A Comparative Study of Visible Photoluminescence from Anodized and from Chemically Stained Silicon Wafers
Authors: Aoyagi Hidekazu , Motohashi Akira , Kinoshita Akira , Aono Tomoyoshi , Satou Akinobu
Published: February 2005

Photoluminescence characteristics of anodized porous layers and chemically stained films are compared. A luminescence and an absorption band observed commonly in both materials suggest existence of similar luminous materials, though anodized samples show additional absorption bands. Consideration of both the properties of porous silicons and anodization conditions suggests that the luminous material contains silicon suboxide. The luminous material, prepared even under pure anodization conditions, is not an anodized product, but a chemical product on the surface of anodized layers, formed simultaneously with anodization.
Toward Insulating Quasicrystalline Alloy in Al-Pd-Re Icosahedral Phase
Authors: Akiyama Hirofumi , Honda Yuko , Hashimoto Tatsuo , Keiichi Edagawa Keiichi Edagawa , Shin Takeuchi Shin Takeuchi
Published: February 2005

The resistivities in Al70Pd20Re10 alloy of the icosahedral phase are quite sample dependent, possibly due to slight variation of the alloy composition. In some samples, the resistivity at room temperature is ∼0.01 Ω·cm and that at 4.2 K is as high as ∼0.1 Ω·cm; these values are much higher than any values reported so far for quasicrystals. The temperature dependence of the conductivity is almost linear above 4.2 K, and the magnetoconductivity is negative. Such dependence is interpreted by the theory of weak localization which takes into account the spin-orbit scattering.
Low Carbon Incorporation in Metalorganic Molecular Beam Epitaxy of GaAs Using Dimethylamine Gallane
Authors: Ishikura Kouji , Hayashi Ken-ichi , Ogawa Tomokazu , Fumio Hasegawa Fumio Hasegawa
Published: February 2005

Dimethylamine gallane (DMAG) was demonstrated to be a promising precursor as a gallium source for metalorganic moleculor beam epitaxy (MOMBE) of GaAs with a low level of carbon incorporaticn. Epitaxial layers of GaAs were obtained at substrate temperatures above 250°C, and the hole concentration decreased with increasing substrate temperature. For the GaAs layer grown at 500°C, the hole concentration and Hall mobility were 1.2×1015 cm-3 and 371 cm2/(V·s), respectively. Low temperature (4.2 K) photoluminescence indicated that the band-to-carbon transition was negligibly small compared with the donor bound exciton peak.
Ambipolar Performances of Novel Amorphous Silicon-Germanium Alloy Thin-Film Transistors
Authors: Hsieh Shou Wei , Chang Chun Yen , Lee Yeong Shyang , Lin Chiung Wei , Wu Biing Sheng , Chen Hsiung Kuang
Published: February 2005

The limitation of low hole mobility in hydrogenated amorphous silicon thin-film transistors (a-Si:H TFTs) was overcome in this present work by utilizing hydrogenated amorphous silicon-germanium (a-Si1-x
Ge
x
:H) alloys as the active channel of TFTs. The performance of hydrogenated amorphous silicon-germanium thin film transistors (a-SiGe:H TFTs) was optimized by switching the germane-to-silane flow ratio. The fabricated a-SiGe:H TFT with 12 at% germanium content was measured as possessing an electron mobility of 0.71 cm2/V·s and a hole mobility of 0.54 cm2/V·s. The on/off current ratio ranging over almost six orders of magnitude in both conduction modes was obtained. Thus a-SiGe:H TFT has offered the opportunity for upgrading of a-Si:H TFTs and would be feasible for application in [CMOS] circuits.
Carrier-Lifetime-Limited Fast Photoconductive Photodetectors on Iron-Diffused GaAs
Authors: Ohsawa Jun , Nobuhiko Hashimoto Nobuhiko Hashimoto , Masatoshi Migitaka Masatoshi Migitaka
Published: February 2005

Deep acceptors of iron have been employed to overcompensate n-GaAs epitaxial layers and to reduce its carrier lifetime. The photodetectors exhibited current pulses with full widths at half-maxium (FWHMs) as short as 72 ps in spite of the large spacing of 15 µm between the electrodes. The dependence of response time and responsivity on the bias voltage shows that the carrier lifetime rather than the transit time limits the speed, and that collection efficiency of photogenerated electrons mainly limits the sensitivity. Absence of the usual long tail in the pulse responses might be due to a distinctive optical property of the iron level at E
V+0.52 eV.
Effects of Ion Species on Reactive-Ion-Beam-Sputtered Zr-N Films
Authors: Yoshitake Masaaki , Nosaka Toshikazu , Akio Okamoto Akio Okamoto , Soichi Ogawa Soichi Ogawa
Published: February 2005

Thin films of Zr-N have been prepared by reactive ion-beam sputtering of a Zr target. Two kinds of ion species, Ar ions and nitrogen ions, were used for sputtering. The film structure, composition of film, and electrical and optical properties of Zr-N films were examined to compare the Zr-N films sputtered by nitrogen ion beam with those sputtered by Ar-ion beam in a nitrogen atmosphere. Semitransparent and highly resistive Zr-N films, which had different properties from stoichiometric ZrN films, were obtained when a Zr target was sputtered by a N-ion beam, whereas gold-colored Zr-N films, whose properties were similar to those of ZrN, were obtained by Ar-ion beam sputtering in a nitrogen atmosphere. It was found that the properties of the Zr-N films strongly depend on the ion species used for sputtering.
Growth of [YBa2Cu3O7-δ]M/[PrBa2Cu3-xGaxO7-δ]N Superlattices by Pulsed Laser Deposition
Authors: Contour J. P. , Sant C. , Ravelosona D. , Fisher B. , Patlagan L.
Published: February 2005

PrBa2Cu3-x
Ga
x
O7-δ thin films up to x=0.2 and YBa2Cu3O7-δ/PrBa2Cu2.8Ga0.2O7-δ superlattices have been grown by pulsed laser deposition (PLD) on {100} SrTiO3 substrate. The resitance of PrBa2Cu2.8Ga0.2O7-δ is 500 times higher at 77 K than the one of unsubstituted PrBa2Cu3O7-δ. At a growth temperature of 785°C, the multilayers have c-axis normal to the substrate surface and satellite peaks have been observed up to i=±3 on X-ray diffraction spectra. At a lower growth temperature the structure becomes oriented with a-axis normal to the growth interface. Secondary-ion mass spectrometry reveals no interdiffusion between Y and Pr and no diffusion of Ga into the YBa2Cu3O7-δ layer. The 15% RBS minimum yield reoorded for the superlattice indicates highly oriented growth. T
c is around 10 K lower than the one of the equivalent decoupled multilayers grown from unsubstituted PrBa2Cu3O7-δ.
Single Transverse Mode Microcavity Laser with Ultralow Threshold
Authors: Heitmann Henrich , Kadota Yoshiaki , Kawakami Tsuyoshi , Yoshihisa Yamamoto Yoshihisa Yamamoto
Published: February 2005

We report on experiments with surface emitting microcavity semiconductor lasers with a mesa-like three-dimensional structure. Mode selectivity is introduced by the small diameter of the top mirror, making single transverse mode oscillation possible. This leads to a reduced threshold pump power as compared with a planar sample with the same structure; on optical pumping we observed a threshold power of about 7 µW at 4 K. The observed laser threshold and spontaneous emission coefficient were compared with the theoretical prediction, giving a reasonable agreement.
Electrical Properties of Quasi-One-Dimensional Compound KFe(S1-xSex)2
Authors: Shido Nishioka Shido Nishioka , Kazuyoshi Hirakawa Kazuyoshi Hirakawa
Published: February 2005

Electrical resistivity measurements have been made on KFe(S1-x
Se
x
)2 (0≤x≤0.90) single crystals. The value along the c-axis is on the order of 105 Ω·cm for x=0 at 320 K. All samples exhibit semiconductive dependence on temperature with a large anomaly around room temperature. The substitution of selenium for sulfur causes decrease in both resistivity and activation energy. The susceptibility of the KFe(S0.74Se0.26)2 single crystal shows paramagnetic behaviour with weak temperature dependence without an anomaly. This indicates the existence of a metallic chain in this series of compounds.
Anomalous Behavior of Electron Spin Resonance in KxC60 Film Prepared by Electrochemical Method
Authors: Araki Hisashi , Yamasaki Nobuo , Kawai Tsuyoshi , Zakhidov Anvar A. , Katsumi Yoshino Katsumi Yoshino
Published: February 2005

Anomalous temperature dependence of the relative intensity ratio of three electron spin resonance (ESR) lines was observed in K
x
C60 films prepared by electrochemical doping in a solid electrolyte. From the ESR saturation curves of those lines measured at various temperatures, their spin-lattice relaxation times (T
1) were estimated. Novel changes in the intensity among those lines with increasing microwave power can be explained by taking the difference in T
1 of those lines into consideration. Under a relatively high doping condition the lowest T
1 of 3.5×10-5 s was evaluated at 7.6 K.
Plasma Swelling of Photoresist
Authors: Yue Kuo Yue Kuo
Published: February 2005

A polymer swelling phenomenon in the hydrogen-containing freon plasma has been observed. The new polymer has a mushroom profile and is very resistant to plasma attack. The swelling rate and the new polymer structure are studied. The swelling process includes 1) new bonds formation, 2) fragments loss, and 3) hydrogenation. The top swollen part and the bottom non-swollen part were compared with the LAMMA (Laser Microprobe Mass Analysis) method. The swollen process is probably caused by the strong ion bombardment in combination with hydrogenation reactions. Possible applications of this new structure are discussed.
Formation of Crystalline SiC Buried Layer by High-Dose Implantation of MeV Carbon Ions at High Temperature
Authors: Chayahara Akiyoshi , Kiuchi Masato , Kinomura Atsushi , Mokuno Yoshiaki , Yuji Horino Yuji Horino , Kanenaga Fujii Kanenaga Fujii
Published: February 2005

A buried layer of crystalline SiC in silicon wafer is synthesized by 1.5 MeV C+ implantation at a dose of 1.5×1018 ions/cm2 at a high temperature of 880°C. The infrared absorption spectrum and the X-ray diffraction pattern of this sample show formation of 3C-type SiC crystal. The pole figures of X-ray diffraction show that crystallographic orientation of the SiC buried layer is aligned along the lattice of the Si substrate, that is, topotaxial internal growth of crystalline SiC occurs in a single crystal of Si during the high-temperature ion implantation.
Polymerization for Highly Selective SiO2 Plasma Etching
Authors: Furuoya Seiji Samukawa
Published: February 2005

In this letter, we report the relationships between polymerization on Si substrates and the generation ratio for reactive species in fluorocarbon plasma, and reveal essential points for SiO2 etching selectivity to underlying Si. The SiO2 etching selectivity to underlying Si is determined by both the fluoropolymer deposition rate and the sputtering rate on underlying Si. The sputtering rate strongly depends on the F atom concentration in the polymer. Conversely, the deposition rate depends on the CF2 radical density in the plasma. Therefore, control of the generation ratio of CF2 radicals to F atoms is needed to realize highly selective SiO2 etching.
Novel Hexagonal-Facet GaAs/AlGaAs Laser Grown by Selective Area Metalorganic Chemical Vapor Deposition
Authors: Ando Seigo , Naoki Kobayashi Naoki Kobayashi , Hiroaki Ando Hiroaki Ando
Published: February 2005

A GaAs hexagonal prism structure with (110) sidewall facets perpendicular to the (111)B substrate surface is obtained by selective area metalorganic chemical vapor deposition using a SiO2 mask. These (110) sidewall facets are extremely smooth like a cleaved surface, so they can be used as the cavities of a semiconductor laser. A novel hexagonal-facet (HF) GaAs/AlGaAs double heterojunction laser structure is proposed and preliminary lasing characteristics are presented. The average threshold of the optical pumping energy for the HF-laser array is approximately 18 pJ for 416 nm excitation. Single-mode (inscribed hexagonal mode) lasing at 875 nm is obtained at room temperature.
Field Ion-Scanning Tunneling Microscopy Study of C84 on the Si(100) Surface
Authors: Hashizume Tomihiro , Wang Xiang-Dong , Nishina Yuichiro , Shinohara Hisanori , Yahachi Saito Yahachi Saito , Toshio Sakurai Toshio Sakurai
Published: February 2005

Initial stage and monolayer/multilayer adsorption of C84 fullerene on the Si(100)2×1 surface was investigated by field ion-scanning tunneling microscopy. The C84 molecules reside stably at room temperature in the trough formed by Si dimer rows. The nearest neighbour distance of the C84 molecules is approximately 14 Å. For the first and second layers, only the disordered adsorption geometry was observed. When C84 was deposited while keeping the substrate at 100 to 150°C, the fcc crystal formation was observed above the third layer with its lattice constant of 17.1 Å.
Lattice Defects in O+ Implanted Tin-Doped Indium Oxide Films
Authors: Shigesato Yuzo , Haynes David C. Paine
Published: February 2005

In this work we use transmission electron microscopy to identify extended lattice defects which result from O+ ion implantation at a dose of 1.3×1015/cm2 into Sn-doped In2O3 at room temperature. Measurement of the resistivity, mobility, carrier density, and transmissivity to visible light as a function of implant dose (0 to 1.3×1015/cm2) reveals that increasing dose results in a degradation in electronic and optical properties of ITO. Analysis of these results using charged and neutral scattering models reveals that the observed changes in electronic and optical properties may be due to the generation of neutral scattering centers. Transmission electron microscopy analysis of heavily O+ implanted films reveals the presence of intragranular regions of isolated strain contrast indicating lattice damage which may be associated with these neutral scatter centers.
Fabrication of InGaAs Strained Quantum Wire Structures Using Selective-Area Metal-Organic Chemical Vapor Deposition Growth
Authors: Arakawa Taro , Tsukamoto Shiro , Nagamune Yasushi , Nishioka Masao , Jin-Hee Lee Jin-Hee Lee , Yasuhiko Arakawa Yasuhiko Arakawa
Published: February 2005

We fabricated In
x
Ga1-x
As strained quantum wire structures with various In compositions using a selective-area metal-organic chemical vapor deposition growth technique. Photoluminescence (PL) measurements at 14 K demonstrated that strained quantum wires of high quality were obtained when x is less than 0.35. Change of the full width at half-maximum of the PL peaks indicates that the structural dimensions of the quantum wires exceeded the critical thickness at around x=0.4.
Recombination Processes in Anodized Porous-Si as Studied by Optically-Detected Magnetic Resonance
Authors: Yasunori Mochizuki Yasunori Mochizuki , Masashi Mizuta Masashi Mizuta
Published: February 2005

Optically-detected magnetic resonance measurements at 1.6 K on anodized porous-Si are performed, in which the visible and infrared luminescence bands are separately monitored. The Si dangling-bond centers are detected and it is shown that these delects are dominantly linked with the infrared luminescence process providing a competing nonradiative channel. The observed anisotropy of the resonance signal reflects the crystalline environment of the region giving rise to the infrared luminescence. The defect is found to have a negligible interaction with the visible recombination process so that the carriers responsible for this light emission are suggested to be localized in a structurally different region from the infrared-emitting one.
NaCl-Type Oxide Films Prepared by Plasma-Enhanced Metalorganic Chemical Vapor Deposition
Authors: Fujii Eiji , Tomozawa Atsushi , Fujii Satoru , Torii Hideo , Masumi Hattori Masumi Hattori , Ryoichi Takayama Ryoichi Takayama
Published: February 2005

Thin films of MgO, NiO and CoO with NaCl-type structure were prepared by plasma-enhanced metalorganic chemical vapor deposition using metal acetylacetonato complexes as source materials. Soda-lime glass, Si(111), stainless steel and fused silica were used as the substrates. X-ray diffraction patterns indicated that (100) preferred-orientation NaCl-type oxide films were obtained at substrate temperatures of 150°C or above, independent of the kind of substrate. Scanning electron microscopy images showed that each film had a smooth surface and a columnar structure with growth perpendicular to the film surface.
Improvement of Jc of Ag-Sheathed Bi-2212 Tapes Using Melt-Growth Technique under Reduced Oxygen Partial Pressure
Authors: Masashi Yoshida Masashi Yoshida , Akihiko Endo Akihiko Endo
Published: February 2005

The growth behavior of Bi-2212 under the oxygen partial pressure of 0.01 atm has been investigated using Ag-sheathed tapes. In the partial melt state, a Cu-free phase and (Sr, Ca)CuO2 have been observed as solid phases. The Cu-free phase has been assigned, tentatively, as Bi2Sr2CaO6. The grain size of the Cu-free phase has been found to depend critically on the starting composition. It decreases as the Sr content increases and the Ca content decreases, and accordingly, J
c of the melt-processed tapes increases. The optimum composition is Bi2Sr2.3Ca0.85Cu2O
z
and the maximum J
c is 1.5×105 A/cm2 at 4 K.
Transient Light Scattering in Antiferroelectric Liquid Crystal
Authors: Moritake Hiroshi , Cho Sungkeun , Masanori Ozaki Masanori Ozaki , Katsumi Yoshino Katsumi Yoshino
Published: February 2005

Transient light scattering has been observed for the first time in the antiferroelectric liquid crystal. The scattering depends on the frequency of the applied triangular wave. Two dips in the light transmission are observed at low frequency. These dips are due to the light scattering in the stripe domains at the ferroelectric-antiferroelectric phase transition. As frequency increases, a new sharp transmission dip appears in addition to those dips. To clarify the origins of these dips, the simultaneous measurement of transmission change and polarization reversal current has been carried out. It is found that the sharp dip is due to transient light scattering caused by switching between two ferroelectric uniform states.
A Novel Atomic Force Microscopy Observation Technique for Secondary Defects of Ion Implantation, using Anodic Oxidation
Authors: Fujii Shinji , Fuse Genshu , Yoshikazu Harada Yoshikazu Harada , Morio Inoue Morio Inoue
Published: February 2005

A novel observation technique for secondary defects of ion implantation has been developed. Stripping of the surface by means of a combination of anodic oxidation and removal of the oxide has been found to expose the buried secondary defects induced by ion implantation. The defects observed by means of atomic force microscopy (AFM) show craterlike forms created by enhanced oxidation around the secondary defects. Detection of the defects with this technique is complementary to conventional transmission electron microscopy (TEM) observation. The technique is a promising method for clarifying the depth distribution of various defects. The technique has also been found to be advantageous for planar TEM observation.
Critical Current Densities at 77 K in Ba2YCu3O7-y-Ag Films Prepared by Dipping-Pyrolysis Process
Authors: Kumagai Toshiya , Yamasaki Hirofumi , Endo Kazuhiro , Manabe Takaaki , Niino Hiroyuki , Tsunoda Tatsuo , Wakichi Kondo Wakichi Kondo , Susumu Mizuta Susumu Mizuta
Published: February 2005

Excellent critical current behavior at 77 K in magnetic fields up to 14 T has been obtained for Ba2YCu3O7-y
(BYCO)-Ag films prepared by dipping-pyrolysis process. The films were epitaxially grown on SrTiO3(100) substrates using a two-step annealing (low-p(O2)/pure O2) method at 770°C. The best values of critical current density at 77 K under a 2-µV/cm criterion were 1.2×106 A/cm2 in a self field and 1.0×105 and 3.8×104 A/cm2 at 8 T and 14 T, respectively, when the field was applied parallel to the a-b plane.
Time Difference in Stimulated Emission from Fluorescent Dye-Doped Small-Size Liquid Droplets
Authors: Hiroshi Taniguchi Hiroshi Taniguchi
Published: February 2005

Observation of the time difference due to varying pumping intensities in the stimulated-emission process from fluorescent dye-doped liquid droplets is reported. It is suggested that the time difference is related to the round-trip time required to support lasing in the droplet.
Acceptor Concentration Control of P-ZnSe Using Nitrogen and Helium Mixed Gas Plasma
Authors: Tosaka Hiroyuki , Nagatake Tsuyoshi , Yoshida Takashi , Masakazu Kobayashi Masakazu Kobayashi , Akihiko Yoshikawa Akihiko Yoshikawa
Published: February 2005

Nitrogen and helium mixed gas plasma was used to grow p-ZnSe. Using the mixed gas, the acceptor concentration can be controlled from 6×1016 to 7×1017 cm-3 while films doped using the nitrogen plasma exhibited the acceptor concentration of 3×1017 cm-3. Doping characteristics such as the acceptor concentration and the PL properties depend on the gas mixing ratio and the rf power. p-ZnSe layers grown with this technique were used for blue-green laser structures. Lasing was observed at 77 K under pulse operation.
Active-Nitrogen-Doped P-Type ZnSe Grown by Gas-Source Molecular Beam Epitaxy for Blue-Light-Emitting Devices
Authors: Imaizumi Masayuki , Endoh Yasuyuki , Ohtsuka Ken-ichi , Toshiro Isu Toshiro Isu , Masahiro Nunoshita Masahiro Nunoshita
Published: February 2005

Active-nitrogen-doped p-type ZnSe epitaxial layers were grown by gas-source molecular beam epitaxy using H2Se. Electrical properties of the N-doped ZnSe layers changed drastically depending on the growth temperature and the VI/II ratio. With decreasing growth temperature, the net acceptor concentration increased. At the growth temperature of 300°C, the net acceptor concentration was as high as 1.02×1018 cm-3. Using this technique, p-n junction diodes with an active layer of ZnCdSe/ZnSe multiple quantum wells were fabricated. These diodes emitted clearly visible blue light (477 nm) at room temperature.
Extremely Flat Interfaces in GaAs/AlGaAs Quantum Wells Grown on GaAs (411)A Substrates by Molecular Beam Epitaxy
Authors: Shimomura Satoshi , Wakejima Akio , Adachi Akira , Okamoto Yasunori , Sano Naokatsu , Murase Kazuo , Hiyamizu Satoshi
Published: February 2005

GaAs/Al0.3Ga0.7As quantum wells (QWs) grown on (411)A-oriented GaAs substrates by molecular beam epitaxy (MBE) showed extremely flat interfaces over a macroscopic area (about 200 µm φ) even for the case of no growth interruption, which is mainly due to the intrinsically large migration of Ga atoms and layer growth in the step-flow mode on the (411)A plane. Photoluminescence linewidths at 4.2K were almost the same as or better than the narrowest linewidths reported for GaAs/AlGaAs and GaAs/AlAs QWs grown on GaAs (100) substrates with growth interruption at each GaAs/AlGaAs(AlAs) interface. Only one sharp luminescence peak was observed for each QW on the (411)A substrates, in contrast with three luminescence peaks for the QWs on the (100) substrates, indicating that extremely flat and uniform interfaces over a macroscopic area of laser excitation (200 µm diameter) are realized in the GaAs/AlGaAs QWs grown on (411)A GaAs substrates.
High-Temperature Absorption by Pure CO2 Far Line Wings in the 4 µm Region
Authors: Tsuboi Takao , Hartmann Naoko Arimitsu
Published: February 2005

We present, for the first time, shock-tube measurements of the absorption of infrared radiation by pure CO2 near 4 µm up to the temperature of 1200 K. The experimental values are in good agreement with previous determinations up to 800 K. These results demonstrate the interesting point of this new measurement technic and the investigated temperature and pressure ranges are extended toward those of the combustion media. Comparisons with calculations confirm the strongly sublorentzian behavior of the far wings of CO2 absorption lines; the accuracy of previously published models based on empirical corrections to the Lorentzian profile is also shown.
Effect of Ethane Addition to Argon in Etching of BiSrCaCuO Superconducting Thin Films
Authors: Oishi Toshiyuki , Takami Tetsuya , Kojima Kazuyoshi , Wada Ken'ichi Kuroda
Published: February 2005

Addition of ethane to argon is found to be very useful in the dry etching of BiSrCaCuO superconducting thin films. BiSrCaCuO thin films are selectively etched with 2.4-20% ethane ratio, because hydrocarbon polymer thin films are deposited on resist masks. The morphology of the surface etched by ethane-argon mixture is smooth, while that by neat argon is rugged.
New Concerted Mechanism of the Cl-Removal Reaction Induced by H2 in Chloride Atomic Layer Epitaxy
Authors: Mochizuki Yuji , Usui Toshikazu Takada
Published: February 2005

A new concerted mechanism is proposed to explain the Cl removal from the adsorbed GaCl on the outermost As surface, by the ab initio configuration interaction (CI) calculations on the simple model system of H2GaCl+H2. The proposed reaction scheme is written as >GaCl+H2→>GaH+HCl which occurs through the single-site collision of H2 with the adsorbed GaCl on the surface. Concerted electron delocalizations induced by H2 is the driving force to proceed the reaction. The present calculation predicts that the reaction is endothermic with an energy of 29 kcal/mol and has a four-centered transition state. The estimated activation energy is 83 kcal/mol, which will be reduced by improving the present cluster model.
Preparation and Time-Resolved Photoluminescence Study of CdTe/Cd1-xMnxTe Single Quantum Wells
Authors: Akinaga Hiroyuki , Shirai Yutaka , Takita Kôki , Nakayama Takeshi , Minami Fujio , Inoue Kuon
Published: February 2005

In this letter, we report the preparation of CdTe/Cd0.81Mn0.19Te single quantum wells (SQW's) whose quantum well thicknesses are determined precisely. The SQW sample has been grown on a GaAs(100) substrate by means of molecular beam epitaxy. A temporal energy shift of the exciton emission is observed in a time-resolved photoluminescence measurement. The shift increases with the decrease of the well thickness. Compared with the result reported previously in the CdTe/Cd0.79Mn0.21Te SQW's with a similar well thickness on a CdTe substrate, the present energy shifts are larger. It is considered that the energy shifts observed in the present study are caused by a magnetic polaron formation of the excitons in the CdTe quantum well layers, whose wave functions penetrate into the Cd1-x
Mn
x
Te layer. The reason for the energy shift enhancement observed in the SQW's grown on the GaAs substrate is discussed.
Planar-Doping of Molecular Beam Epitaxy Grown ZnSe with Plasma-Excited Nitrogen
Authors: Matsumoto Shigeyuki , Tosaka Hiroyuki , Yoshida Takashi , Masakazu Kobayashi Masakazu Kobayashi , Akihiko Yoshikawa Akihiko Yoshikawa
Published: February 2005

Planar doping of nitrogen into ZnSe is examined. The dependence of doping efficiency on the particular surface termination (Zn- or Se-stabilised) on (100) ZnSe is investigated through capacitance-voltage measurement and low-temperature photoluminescence (PL) spectroscopy. Using planar doping on the Zn surface, we achieved a hole concentration of 4.5×1017 cm-3, and the PL spectrum is dominated by strong donor-acceptor pair (DAP) emissions. By contrast, the film planar-doped on the Se plane shows rather low hole concentration, and the spectrum is dominated by excitonic features along with very weak DAP emissions.
Schottky Barrier Height of Phosphidized InGaAs
Authors: Sugino Takashi , Yoshifumi Sakamoto Yoshifumi Sakamoto , Junji Shirafuji Junji Shirafuji
Published: February 2005

The Schottky barrier height of phosphidized InGaAs has been studied. The surface of InGaAs (In 53%) lattice-matched to InP is treated with gentle phosphine plasma. Schottky junctions are then formed on phosphidized InGaAs by evaporating various metals such as Au, Cu, Ti and Ag. True barrier heights estimated from the Richardson plot are found to be significantly dependent on the metal work function. Phosphidization forms a thin phosphorus layer in addition to substitution of phosphorus for arsenic, resulting in formation of metal-insulator-semiconductor (MIS) Schottky junctions. An effective barrier height as high as 0.7 eV is attained for Au/InGaAs MIS Schottky junctions as measured from the room temperature current-voltage characteristic, while the true barrier height of 0.55 eV, which is close to the Schottky limit, is estimated from the Richardson plot.
1.5-GHz Band-Pass Microstrip Filters Fabricated Using EuBaCuO Superconducting Films
Authors: Nagai Yasuhiro , Itoh Keiichiro , Suzuki Naobumi , Michikami Osamu
Published: February 2005

This letter reports the properties of 1.5-GHz band-pass microstrip filters fabricated using EuBacuO superconducting films. Although 3- and 4-pole filters constructed using a superconductor and a silver ground plane exhibited good reproducibility and very low insertion loss of 3∼5 dB at 70 K, in comparison with Cu filters with 16∼27 dB loss at 77 K, the insertion loss was almost constant at temperatures below 70 K. In contrast, the insertion loss in the 4-pole filter with a superconductive ground plane was 1.2 dB at 70 K and 0.6 dB at 28 K. The center frequency and bandwidth at -3 dB were, respectively, 1.45 GHz and 1.4% at temperatures below 70 K.
Discriminating Molecular Length of Chemically Adsorbed Molecules Using an Atomic Force Microscope Having a Tip Covered with Sensor Molecules (An Atomic Force Microscope Having Chemical Sensing Function)
Authors: Nakagawa Tohru , Ogawa Kazufumi , Kurumizawa Toshimitsu , Ozaki Shinji
Published: February 2005

A novel atomic force microscope (AFM) having a chemical sensing function has been proposed. Using an AFM having a tip on which surface sensor molecules were immobilized, the molecular lengths of chemically adsorbed molecules on the solid surface were discriminated for the first time.
Nanoscale InP Islands for Quantum Box Structures by Hydride Vapor Phase Epitaxy
Authors: Ahopelto Jouni , Yamaguchi A. Atsushi , Nishi Kenichi , Akira Usui Akira Usui , Hiroyuki Sakaki Hiroyuki Sakaki
Published: February 2005

A novel method utilizing the island formation in hydride vapor phase epitaxy (VPE) is used to fabricate structures in which nanoscale InP islands are buried in InGaP. The method allows the structures to be grown without using photolithography or etching steps. An intense, island-related photoluminescence is observed from the structures. The emission is blueshifted from the InP bulk emission wavelength and shows dependence on the island size. The island formation dependence on growth conditions is investigated in the attempt to be able to control the size and the density of the islands.
Preparation of Phthalocyanine-Dispersed Polymer Thin Film by Solvent-Free Process with Vapor Deposition Polymerization
Authors: Sakakibara Youichi , Iijima Masayuki , Tsukagoshi Kiyomi , Takahashi Yoshikazu
Published: February 2005

We report our success in the solvent-free preparation of copper phthalocyanine (CuPc)-dispersed polymer thin film using a vacuum process. CuPc was coevaporated at the same time polyurea film was formed by the vapor deposition polymerization method. Transparent films were formed uniformly on glass substrates. Film thickness and concentration of CuPc were controlled through the deposition time and deposition rate. CuPc was found to disperse in needlelike microcrystalline form within polyurea, as determined by electron microscopy. The structure of polyurea and CuPc microcrystals was discussed, using infrared and visible absorption spectra.
V-Shaped Gate High Electron Mobility Transistor (VHEMT)
Authors: Ishii Masami , Matsumoto Kazuhiko , Morozumi Hidehiro , Yoshinobu Sugiyama Yoshinobu Sugiyama , Tsunenori Sakamoto Tsunenori Sakamoto
Published: February 2005

V-shaped gate high electron mobility transistor (VHEMT) is proposed and demonstrated for the first time. The V-shaped trench fabricated by an anisotropic selective etching was used to reduce an effective gate length below the lithography limit. The transconductance of the VHEMT fabricated exceeds 400 mS/mm, and the effective gate length comes to 20 nm.
A New Resonant Tunneling Logic Gate Employing Monostable-Bistable Transition
Authors: Koichi Maezawa Koichi Maezawa , Takashi Mizutani Takashi Mizutani
Published: February 2005

This letter describes a new resonant tunneling logic gate. The concept of the proposed gate has two features: 1) to employ the monostable-to-bistable transition of a circuit consisting of two N-type negative differential resistance (NDR) devices connected serially, and 2) to drive the logic gate by oscillating the bias voltage to produce the transition. This mode of operation has a significant advantage in that a large number of fanouts is possible without sacrificing the high-speed operation. Serially connected resonant tunneling field effect transistors having p+-junction gates were fabricated to test the above operation principle. The inverter operation of the proposed logic gate has been successfully achieved at room temperature.
Large-Area High-Speed Diamond Deposition by Rf Induction Thermal Plasma Chemical Vapor Deposition Method
Authors: Kohzaki Masao , Uchida Kiyoshi , Kazuo Higuchi Kazuo Higuchi , Shoji Noda Shoji Noda
Published: February 2005

By introducing methane as a sheath gas and by reducing the reactor chamber pressure to 150 Torr in an rf induction thermal plasma chemical vapor deposition (CVD) method, a large volume of the thermal plasma was stabilized and elongated to reach far into the reactor chamber where a molybdenum substrate was placed. This made it possible to deposit diamond films uniformly on a substrate as large as 100 mm in diameter at a high deposition rate of 30 µm/h. This deposition area is the largest one of diamond films ever deposited by the rf induction thermal plasma CVD method.
Wide Band Erbium-Doped Fluoride Fiber Optical Amplifier at 2.7 µm with Fluoride Fiber Wavelength-Division Multiplex Coupler
Authors: Yamamoto Takashi , Tetsurou Komukai Tetsurou Komukai , Yoshiaki Miyajima Yoshiaki Miyajima
Published: February 2005

A 2.7 µm band optical amplifier composed of an erbium doped fluoride fiber and a low loss fluoride fiber wavelength-division multiplex (WDM) coupler is reported. A maximium gain of 35.9 dB was obtained. An optical gain of more than 20 dB was obtained over a 90 nm wavelength range from 2.72 to 2.81 µm with a pump of 200 mW at 0.647 µm. The saturation output signal power was -2 dBm, and was independent of the pump power.
MEMBRANE-ASSOCIATED GUANYLATE KINASES REGULATE ADHESION AND PLASTICITY AT CELL JUNCTIONS
Authors: Funke Lars , Dakoji Srikanth , Bredt David S.
Published: February 2005

▪ Abstract  Tissue development, differentiation, and physiology require specialized cellular adhesion and signal transduction at sites of cell-cell contact. Scaffolding proteins that tether adhesion molecules, receptors, and intracellular signaling enzymes organize macromolecular protein complexes at cellular junctions to integrate these functions. One family of such scaffolding proteins is the large group of membrane-associated guanylate kinases (MAGUKs). Genetic studies have highlighted critical roles for MAGUK proteins in the development and physiology of numerous tissues from a variety of metazoan organisms. Mutation of Drosophila discs large (dlg) disrupts epithelial septate junctions and causes overgrowth of imaginal discs. Similarly, mutation of lin-2, a related MAGUK in Caenorhabditis elegans, blocks vulval development, and mutation of the postsynaptic density protein PSD-95 impairs synaptic plasticity in mammalian brain. These diverse roles are explained by recent biochemical and structural analyses of MAGUKs, which demonstrate their capacity to assemble well-defined—yet adaptable—protein complexes at cellular junctions.
Lipids, Lipases, and Lipid-Modifying Enzymes in Plant Disease Resistance
Authors: Shah Jyoti
Published: February 2005

Lipids and lipid metabolites influence pathogenesis and resistance mechanisms associated with plant-microbe interactions. Some microorganisms sense their presence on a host by perceiving plant surface waxes, whereas others produce toxins that target plant lipid metabolism. In contrast, plants have evolved to recognize microbial lipopolysaccharides (LPSs), sphingolipids, and lipid-binding proteins as elicitors of defense response. Recent studies have demonstrated that the plasma membrane provides a surface on which some plant resistance (R) proteins perceive pathogen-derived effectors and thus confer race-specific resistance. Plant cell membranes also serve as reservoirs from which biologically active lipids and precursors of oxidized lipids are released. Some of these oxylipins, for example jasmonic acid (JA), are important signal molecules in plant defense. Arabidopsis thaliana is an excellent model plant to elucidate the biosynthesis and metabolism of lipids and lipid metabolites, and the characterization of signaling mechanisms involved in the modulation of plant defense responses by phytolipids. This review focuses on recent studies that highlight the involvement of lipids and lipid metabolites, and enzymes involved in lipid metabolism and modification in plant disease resistance.
Ten- to 12-Hz EEG Oscillation in the Rat Hippocampus and Rhinal Cortex That Is Modulated by Environmental Familiarity
Authors: Nerad Luděk , Bilkey David K.
Published: February 2005

A characteristic feature of the electroencephalogram (EEG) of the hippocampus and rhinal (entorhinal and perirhinal) cortex of the freely moving rat is theta rhythm, a prominent oscillation of ∼8 Hz. Here we demonstrate that a novel rhythm that occurs at the border between the theta and alpha range of frequencies (10–12 Hz) can also be recorded from these structures. This rhythm (referred to here as “flutter”) appears to be of non-theta origin as it can occur simultaneously with theta and it does not display the phase inversion across the hippocampus that characterizes theta activity. Flutter is observed in locomoting rats that are foraging for food reward in a familiar environment. Flutter disappears when rats are placed into a novel (although visually identical) environment, even though their foraging behavior does not appear to be altered. It is, at the present time, unclear what function flutter subserves. The presence of flutter may relate to a particular motivational state of the animal or to a particular type of information processing.
Modulation of Spontaneous Firing in Rat Subthalamic Neurons by 5-HT Receptor Subtypes
Authors: Xiang Zixiu , Wang Lie , Kitai Stephen T.
Published: February 2005

The subthalamic nucleus (STN) is considered to be one of the driving forces in the basal ganglia circuit. The STN is innervated by serotonergic afferents from the raphe nucleus and expresses a variety of 5-HT receptor subtypes. We investigated the effects of 5-HT and 5-HT receptor subtype agonists and antagonists on the firing properties of STN neurons in rat brain slices. We used cell-attached, perforated-patch, and whole cell recording techniques to detect changes in firing frequency and pattern and electrical membrane properties. Due to the depolarization of membrane potential caused by reduced potassium conductance, 5-HT (10 μM) increased the firing frequency of STN neurons without changing their firing pattern. Cadmium failed to occlude the effect of 5-HT on firing frequency. 5-HT had no effect on afterhyperpolarization current. These results indicated that the 5-HT action was not mediated by high-voltage–activated calcium channel currents and calcium-dependent potassium currents. 5-HT had no effect on hyperpolarization-activated cation current ( IH) amplitude and voltage-dependence of IH activation, suggesting that IH was not involved in 5-HT–induced excitation. The increased firing by 5-HT was mimicked by 5-HT2/4 receptor agonist α-methyl-5-HT and was partially mimicked by 5-HT2 receptor agonist DOI or 5-HT4 receptor agonist cisapride. The 5-HT action was partially reversed by 5-HT4 receptor antagonist SB 23597-190, 5-HT2 receptor antagonist ketanserin, and 5-HT2C receptor antagonist RS 102221. Our data indicate that 5-HT has significant ability to modulate membrane excitability in STN neurons; modulation is accomplished by decreasing potassium conductance by activating 5-HT4 and 5-HT2C receptors.