bluuebunny/crossref_metadata_2025 huggingface dataset:
Infrared Luminescence from Bismuth-Doped Silica Glass
Authors: Yasushi Fujimoto Yasushi Fujimoto , Masahiro Nakatsuka Masahiro Nakatsuka
Published: October 2002

A new infrared luminescence from bismuth-doped silica glass is discovered. Spectroscopic properties of this glass are different from those of previously reported Bi2+- or Bi3+-doped glasses or crystals. Its luminescence spectrum is wide (full-width at half maximum; about 200 nm), with the peak at 1140 nm with 500 nm excitation. Absorption bands exist between the visible and near-infrared region. The lifetime of bismuth-doped silica glass is 630 µs at room temperature, which is longer than the lifetimes of Bi3+ luminescence reported previously.
An X-Ray Trichrome Imaging `Trinity': Absorption, Phase-Interference and Angle-Resolved Contrast
Authors: Ando Masami , Sugiyama Hiroshi , Zhang Xiaowei , Hyodo Kazuyuki , Maksimenko Anton , Pattanasiriwisawa Wanwisa
Published: October 2002

A newly designed 100-mm-long X-ray trichrome optics for imaging has been proposed. Its working X-ray photon energy is 35 keV. Since this optics has two alternate mirrors, it can simultaneously supply three types of images: absorption, phase-interference and angle-resolved contrast for a sample space of 7 mm width. Examples of imaging by this novel X-ray interferometer in medicine, biology and material science are presented.
Effect of Temperature and Illumination on the Instability of a-Si:H Thin-Film Transistors under AC Gate Bias Stress
Authors: Huang Chun-Yao , Teng Teh-Hung , Yang Cheng-Jer , Tseng Chang-Ho , Cheng Huang-Chung
Published: October 2002

This work investigates the temperature and illumination effects on the a-Si:H thin-film transistors (a-SiH TFTs) under AC gate bias stress to find the larger threshold voltage shift and subthreshold swing change for the bias-temperature-stress (BTS) and bias-illumination-stress (BIS). Excess carriers from thermal-generation electron-hole pairs or photoexcited electron-hole pairs may significantly influence the instability of a-Si:H TFTs during bias stress. The instability mechanisms originate from the carrier-induced defect creation enhanced by thermal generation in the BTS case and also emphasized by photoexcitation for the BIS case. Both stress conditions will induce a larger threshold voltage shift and higher cutoff frequency than those for simple bias stresses.
Monitoring of Two-Dimensional Plasma Uniformity with Electrostatic Probing of Oxidized Wafer Surface
Authors: Mitsuo Yasaka Mitsuo Yasaka , Tomoyuki Kitamura Tomoyuki Kitamura , Masayoshi Takeshita Masayoshi Takeshita , Tanemasa Asano Tanemasa Asano
Published: October 2002

A new method of monitoring the two-dimensional uniformity of plasma for semiconductor processing is proposed. This method measures electric potential distribution of the surface of an oxidized Si wafer exposed to plasma using an electrostatic probe array. The O2 and H2 plasmas generated using a reactive ion etching equipment are tested. It is shown that the measured electric potential distribution agrees well with the distribution of plasma parameters measured using a Langmuir probe. A good correlation between the measured plasma nonuniformity and the degradation of gate SiO2 of metal-oxide-silicon (MOS) structure is demonstrated.
E-J Characteristics and Distribution of Local Jc for Melt-Textured Grown Bulk YBa2Cu3O7 under High Magnetic Fields
Authors: Satoshi Awaji Satoshi Awaji , Kazuo Watanabe Kazuo Watanabe , Mitsuhiro Motokawa Mitsuhiro Motokawa , Akira Kuramochi Akira Kuramochi , Tetsuo Fukase Tetsuo Fukase , Keiichi Kimura Keiichi Kimura
Published: October 2002

In order to evaluate the distribution of flux pinning for a melt-textured grown bulk YBa2Cu3O7 under magnetic fields, the E-J properties for samples prepared under various magnetic fields were measured. The measured E-J properties were analyzed on the basis of a local J
c distribution model proposed by Yamafuji and Kiss [K. Yamafuji and T. Kiss: Physica C 290 (1997) 9]. The distribution of local J
c was found to narrow continuously with increasing magnetic field applied to the melt growth process, independent of the critical current density. The weak links at subdomain boundaries were considered to improve as a result of the change in crystallinity.
Dielectric Properties of Ferroelectric Liquid Crystal Hexakis(4-(4′-((s)-6-methyloctyloxy)biphenoxy)cyclotriphosphazene
Authors: Moriya Keiichi , Ikematsu Hiroshi , Nakagawa Shigekazu , Yano Shinichi , Negita Keishi
Published: October 2002

In the smectic C*(SmC*) phase of hexakis(4-(4′-((s)-6-methyloctyloxy)biphenoxy)cyclotriphosphazene (SMOCP), the temperature dependence of the dielectric constants was measured in the frequency region between 5 and 400 Hz. With decreasing temperature, a peak was observed in the dielectric permittivities, ε
′, and dielectric losses, ε
′′, just below the isotropic liquid (Is)-to-SmC*-phase transition point. Upon lowering the frequency, the peak became higher and its position shifted towards lower temperatures. Using the frequency dependences of ε
′ and ε
′′, a Cole-Cole plot was obtained, which related that the dielectric relaxational intensity Δε was large, and about 270 at 436 K. On the basis of these results, we suggested that the obtained dielectric behaviors were due to the Goldstone mode in the SmC* phase.
Widely Broadened Super Continuum Generation Using Highly Nonlinear Dispersion Shifted Fibers and Femtosecond Fiber Laser
Authors: Norihiko Nishizawa Norihiko Nishizawa , Toshio Goto Toshio Goto
Published: October 2002

1.25–1.95 µm widely broadened and almost flat super continuum is generated using only 5-m-long polarization maintaining highly nonlinear dispersion shifted fiber (PM-HN-DSF) and passively mode-locked Er-doped fiber laser. When the fiber length is 200 m, although there is a large depression around 1.5 µm, the optical spectra are widely broadened from 1.1 to 2.1 µm. The temporal distributions of the spectral components in the super continuum are observed using the technique of cross correlation frequency resolved optical gating. The initial generation process of the super continuum is directly observed.
Morphological Stability of TiO2 Thin Films with Isolated Columns
Authors: Motofumi Suzuki Motofumi Suzuki , Tadayoshi Ito Tadayoshi Ito , Yasunori Taga Yasunori Taga
Published: October 2002

We have investigated the stability of the morphologies of obliquely deposited TiO2 thin films against annealing and humidity. For the thin films with closely distributed columns, the thickness decreases by more than 10% by annealing at 500°C, and the columnar structure is destroyed by exposure to hot water vapor. However, the thin films with isolated columns show no significant change in the thickness and morphology. This can be understood in terms of the stress induced in the thin films with columns which are in contact or isolated. The stable morphologies of the thin films with isolated columns and their shape-related functions are useful for devices that require thermal processing and those used under humid conditions.
Dynamics of Surface-Stabilized Ferroelectric Liquid Crystals at the Alignment Layer Surface Studied by Total-Reflection Ellipsometry
Authors: Toshiyasu Tadokoro Toshiyasu Tadokoro , Ken-ichi Akao Ken-ichi Akao , Toshiaki Yoshihara Toshiaki Yoshihara , Satoshi Okutani Satoshi Okutani , Munehiro Kimura Munehiro Kimura , Tadashi Akahane Tadashi Akahane , Hirokazu Toriumi Hirokazu Toriumi
Published: October 2002

The reorientation dynamics of surface-stabilized ferroelectric liquid crystals (SSFLCs) at the substrate surface have been studied by time-resolved spectroellipsometry (TRSE). The results of total-reflection TRSE indicate that the surface motion of SSFLC molecules is hindered by a strong anchoring system. The observed dependence of the ellipsometric parameter Ψ on the orienting layer material is discussed in terms of the competitive effects of the surface tilt angle and the strength of the surface anchoring effect. It is also demonstrated that TRSE can analyze the mode of motion of SSFLC molecules in three-dimensional space and can therefore characterize the hysteresis properties of the SSFLC cell in terms of its structural changes.
Electrical and Physical Properties of Lead Aluminum Niobate-Lead Titanate Ferroelectric Thin Films Prepared by Chemical Solution Deposition Process
Authors: Zhang Bo-Ping , Iijima Takashi , Yamashita Yohachi
Published: October 2002

A new ferroelectric 0.2Pb1.1(Al1/2Nb1/2)O3-0.8Pb1.1TiO3 thin film with 430 nm thickness was fabricated successfully on Pt(111)/Ti/SiO2/Si substrate using a chemical solution deposition process. This thin film was a perovskite single phase with a <100 > dominating orientation. The dielectric constant and the dielectric loss factor are 600 and 0.015, respectively. A broad peak with a value of about 730 at the Curie temperature of 340°C appeared in the plot of the temperature dependence of the dielectric constant. The remanent polarization (P
r) and the coercive field (E
c) are 12 µm/cm2 and 38 kV/cm, respectively. The addition of Pb(Al1/2Nb1/2)O3 is more effective than individual aluminum or niobium doping in improving the dielectric and ferroelectric properties.
Deep-Level Transient Spectroscopy Detection of Iron in Hydrogenated p+ Silicon
Authors: Tokuda Yutaka , Namizaki Takashi , Murase Tomoki , Hasegawa Takeshi , Shiraki Hiroyuki
Published: October 2002

Heavily boron-doped (100) p+ silicon with the resistivity of 0.01 Ω·cm was hydrogenated in boiling water to reduce the carrier concentration near the surface. Schottky diodes were successfully fabricated on the hydrogenated surface of p+ silicon for deep-level transient spectroscopy (DLTS) measurements. This procedure was applied to intentionally iron-contaminated p+ silicon since no pairing between hydrogen and iron occurs, in contrast with pairing between hydrogen and boron. Iron-boron pairs (E
v+0.10 eV) with the concentration of 4.3×1013 cm-3 were observed for the first time by DLTS in p+ silicon which was iron-contaminated.
Alloy Semiconductor System with Tailorable Band-Tail: A Band-State Model and Its Verification Using Laser Characteristics of InGaN Material System
Authors: Yamaguchi A. Atsushi , Kuramoto Masaru , Kimura Akitaka , Nido Masaaki , Mizuta Masashi
Published: October 2002

In this paper, we present a model for a new class of semiconductor alloy systems that have a tailorable band-tail. The model is constructed from experimentally derived data on the InGaN alloy system and is extended to a general form. The experiment shows that the possible band-edge fluctuation can be grown-in at least between 3 to 170 meV with a single well-defined quasi-Fermi level. For different degrees of compositional fluctuation grown in the InGaN-quantum-well active layers in laser diodes, the differential gain and compositional fluctuation show a strong correlation in full accordance with the theoretical model proposed here for a band-tail modified by In compositional fluctuation. Possible parameters, including differential gain, are discussed for optimization of laser performance.
Electrical Characteristics of Al/CeO2(200)/Si(100) and Al/CeO2(111)/Si(100) Metal-Insulator-Semiconductor Structure
Authors: Leejun Kim Leejun Kim , Jinmo Kim Jinmo Kim , Hunjung Lee Hunjung Lee , Donggeun Jung Donggeun Jung , Yonghan Roh Yonghan Roh
Published: October 2002

Capacitance–voltage (C–V) and current–voltage (I–V) characteristics of Al/CeO2/Si(100) metal-insulator-semiconductor structures were found to be dependent on the crystal orientations of CeO2 thin films, which were deposited by radio-frequency magnetron sputtering. The C–V curve for the Al/CeO2/Si(100) structure made with CeO2 with (200)-preferred orientation (referred to as CeO2(200)) did not show any notable hysteresis, while the Al/CeO2/Si(100) structure made with CeO2 with (111)-preferred orientation (referred to as CeO2(111)) showed a counter-clockwise hysteresis, whose width was as high as ∼1.5 V. The hysteresis difference between Al/CeO2(200)/Si(100) and Al/CeO2(111)/Si(100) is thought due to the difference in the preferred orientation of the CeO2 layer, and thus the stress between the CeO2 thin film and the Si substrate. The Al/CeO2(111)/Si(100) structure with CeO2 of larger grains showed larger leakage current than the Al/CeO2(200)/Si(100) structure with CeO2 of smaller grains.
Infrared Absorption Spectra of C Local Mode in Si1-x-yGexCy Crystals
Authors: Kanzawa Yoshihiko , Nozawa Katsuya , Saitoh Tohru , Kubo Minoru
Published: October 2002

The local vibration mode of substitutional C atoms (C-LVM) in high-quality Si1-x-y
Ge
x
C
y
crystals was studied by infrared absorption spectroscopy. The peak intensity and full width at half maximum of C-LVM were found to change depending on Ge content as well as substitutional C content. However, the integrated intensity of C-LVM exhibited a linear dependence on the substitutional C content. These results demonstrate that the effective charge of substitutional C atoms in Si1-x-y
Ge
x
C
y
crystals is independent of their atomic configurations. Moreover, the present results clearly indicate that the substitutional C content can be estimated from the integrated intensity of C-LVM.
On-Chip Investigation of Torque/Speed Characteristics on New High-Torque Micrometer-Size Polysilicon Electrostatic Actuators
Authors: Le Moal Patrice , Minotti Patrice , Bourbon Gilles , Joseph Eric
Published: October 2002

In this study, we investigate new-generation high-torque/low-speed electrostatic micromotors as well as original on-chip testing methods for the mechanical characterization of silicon-based microactuators. Torque/speed characteristics of micrometer-size electrostatic actuators are measured for the first time using real-time elastic braking video analysis of polysilicon rotors that are monolithically coupled with elastic mechanical sensors. Loading characteristics measured through on-chip electrostatic probing indicate the potentialities of emerging actuator design methodologies involving frictional stator/rotor contact interactions on the micrometer scale.
Temperature Dependence of TaSiN Thin Film Resistivity from Room Temperature to 900°C
Authors: Oizumi Munenori , Aoki Katsuhiro , Fukuda Yukio
Published: October 2002

The conductivity of TaSiN thin film was investigated in a wide temperature range from room temperature to 900°C, and, based on the measurement, a new model for the temperature dependence of TaSiN thin film conductivity was proposed. TaSiN thin films were deposited on thermally oxidized Si wafers using reactive RF cosputtering. Resistivities of the films were measured from room temperature to 900°C by the four-contact probe method. All the films showed decreases in resistivity as temperature increased. The temperature dependence of conductivity at high temperature was described by a model with two conductors connected in parallel, one proportional to 1/T, another proportional to the Arrhenius-type thermal activation term (exp
(-E/kT)).
Nonlinear Photoluminescence Behavior in Closely Packed CdSe Nanocrystal Thin Films
Authors: Maenosono Shinya , Ozaki Eiji , Yoshie Kenichi , Yamaguchi Yukio
Published: October 2002

We report on the cooperative photoluminescence (PL) properties of closely packed CdSe nanocrystal thin films and propose a model to elucidate the nonlinear PL behavior. The PL exhibits an initial decay and a subsequent enhancement under continuous excitation, which are attributed to the photodarkening and the effects of photooxidation (neutralization and suppression of the photoionization rate). The PL enhancement correlates with the degree of oxidation. X-ray photoelectron spectroscopy (XPS) confirms that photooxidation of nanocrystals proceeds as a function of time.
Thermoelectric Properties of NaCo2-xCuxO4 Improved by the Substitution of Cu for Co
Authors: Ichiro Terasaki Ichiro Terasaki , Yutaka Ishii Yutaka Ishii , Daisuke Tanaka Daisuke Tanaka , Kazumi Takahata Kazumi Takahata , Yoshiaki Iguchi Yoshiaki Iguchi
Published: October 2002

We prepared a set of polycrystalline samples of the thermoelectric oxide Na1.2Co2-x
Cu
x
O4 (x=0, 0.1, 0.2 and 0.3), and investigated the Cu substitution effects on their thermoelectric properties. The substituted Cu significantly enhances the thermopower over the temperature range from 4 to 300 K, whereas it does not appreciably change the resistivity and the thermal conductivity. As a result, the thermoelectric figure of merit increases by five times at 100 K from x=0 to 0.3. The Cu substitution effects observed here are highly incompatible with usual impurity effects that increase the resisitivity leaving the thermopower unchanged. The doped Cu shifts the reflectivity edge to lower energies, implying that it causes a decrease of the carrier concentration and/or an increase of the effective mass.
Temperature Dependence of the Surface Resistance of a Bi–Sr–Ca–Cu–O Whisker Measured by the Probe-Coupled Microstrip Resonator Method
Authors: Kishida Daisuke Okai , Takeshi Hatano Takeshi Hatano
Published: October 2002

The temperature dependence of the surface resistance of Bi–Sr–Ca–Cu–O whiskers measured by the probe-coupled microstrip resonator method was examined. Two kinds of whiskers were measured: plate-like and wire-like. The surface resistances of the plate-like and wire-like whiskers were 0.65 mΩ and 1.6 mΩ at 53 K and 6.9 GHz, respectively. These values were approximately 4 ∼10 times larger than that of a high-quality Bi2Sr2CaCu2O
x
(Bi-2212) single crystal.
Parametric Amplification in a Directly Modulated Semiconductor Laser
Authors: Cho Seong-Dae , Lee Chang-Hee , Shin Sang-Yung
Published: October 2002

We investigate the parametric amplification and its saturation characteristics in a directly modulated semiconductor laser. The parametric gain depends on the resonance frequency shift that occurs due to the pump modulation current and the bias current. Also, the parametric gain is a strong function of the phase between the signal and the pump modulation currents. The saturation characteristic of the parametric amplification occurs at a large signal modulation current due to depletion of the pump by an amplified optical signal. We explain the observed behaviors using the analytic results of the nonlinear rate equations of the semiconductor laser.
Diamond Deposition on a Large-Area Substrate by Plasma-Assisted Chemical Vapor Deposition Using an Antenna-Type Coaxial Microwave Plasma Generator
Authors: Taniyama Norikazu , Kudo Minoru , Matsumoto Osamu , Kawarada Hiroshi
Published: October 2002

Diamond deposition on a large area silicon wafer substrate (φ100 mm) is achieved with a methane/hydrogen plasma induced by an antenna-type coaxial microwave plasma generator. Deposition of diamond is observed over the entire substrate. Diamond precursors are emitted radially onto a silicon substrate from the plasma sphere generated at the tip of the antenna. The possibility of diamond deposition outside the plasma sphere is discussed using a semi-empirical equation.
An Improved In0.34Al0.66As0.85Sb0.15/InP Heterostructure Utilizing Coupled δ-Doping InP Channel
Authors: Chen Yeong-Jia , Chen Yen-Wei , Lin Yu-Shyan , Yeh Chia-Yen , Li Yih-Juan , Hsu Wei-Chou
Published: October 2002

A coupled δ-doped In0.34Al0.66As0.85Sb0.15/InP heterostructure field-effect transistor (HFET) has been successfully grown by metalorganic chemical vapor deposition. Electron mobilities can be enhanced without sacrificing the carrier densities. An extremely low gate reverse leakage current of 111 µA/mm at V
gs=-40 V is achieved. The three-terminal on- and off-state breakdown voltages are as high as 40.8 V and 16.1 V, respectively. These characteristics are attributed to the use of the coupled δ-doped structure, InP channel, In0.34Al0.66As0.85Sb0.15 Schottky layer, and to the large conduction-band discontinuity (ΔE
C) at the InAlAsSb/InP heterojunction. In addition, on- and off-state breakdown mechanisms in the InAlAsSb/InP HFET are also studied.
Novel High-Density Microwave Plasma Utilizing an Internal Spoke Antenna for Fast Deposition of Microcrystalline Silicon Films
Authors: Shirai Hajime , Yoshino Koichi , Ohkawara Go , Ueyama Hiroyuki
Published: October 2002

Novel high-density and low-temperature microwave plasma utilizing an internal spoke antenna is demonstrated. No quartz glass plate is required to maintain a high-density plasma using the alumina-ceramic-coated spoke antenna. Consequently, the plasma source is fairly simple. This microwave plasma maintains the uniform state over a diameter of 22 cm with a high electron density of 1011 cm-3 and a low temperature of 1–3 eV as well as a higher traveling efficiency of the microwave power to the chamber than that of the external one. A fast deposition rate of ∼ 40 Å/s is achieved for highly crystallized microcrystalline silicon (µc-Si:H) formation from SiH4 and H2 under lower-power-supply conditions. This high-density microwave plasma utilizing an internal spoke antenna has a high potential for larger-area thin film processing.
Profile Reconstruction Methods for Pulse Reflectometry
Authors: G. Bruskin Leonid , Atsushi Mase Atsushi Mase , Akihide Yamamoto Akihide Yamamoto , Masamichi Ohashi Masamichi Ohashi , Takashi Deguchi Takashi Deguchi
Published: October 2002

We present an analysis of the time delay methods of plasma profile reconstruction applied to ultra-short pulse (USP) reflectometry. As the instantaneous frequencies become poorly localized in the time domain, even the advanced time-frequency analysis fails to produce reliable values of the time delay for corresponding modes. Based on the results of analytical modeling of USP propagation in plasma the signal record analysis method of profile reconstruction is proposed. The method has an advantage of relying on a row signal record rather than on the delay time of each frequency mode, which makes it more robust and reliable for the problem of density profile measurements using USP reflectometry.
Property Improvement of 75 nm-thick Directly-crystallized SrBi2Ta2O9 Thin Films by Pulse-introduced Metalorganic Chemical Vapor Deposition at Low Temperature
Authors: Mitsuya Masatoshi , Nukaga Norimasa , Watanabe Takayuki , Funakubo Hiroshi , Saito Keisuke
Published: October 2002

Crystallized SrBi2Ta2O9 (SBT) films were deposited on (111) Ir/TiO2/SiO2/Si substrates at 650°C by metalorganic chemical vapor deposition (MOCVD). Crystallized SBT films from 75 to 200 nm in thickness were directly deposited, but its remanent polarization (Pr) decreased when the film thickness decreased for the film deposited by conventional continuous-MOCVD. This Pr value was increased by 50% by using the source gas pulse-introduction technique (pulse-MOCVD) at 75 nm thicknesses. Moreover, the leakage current was dramatically improved to be on the order of 10-5 A/cm2 up to 600 kV/cm. This film exhibited strong (103) orientation of the crystal axis, while the continuous gas-introduced film showed a mixture of (00l) and (103) orientations.
(110) NdBa2Cu3O7-δ and YBa2Cu3O7-δ Films Grown on (110) NdBa2Cu3O7-δ Single Crystal Substrates by 90° Off-Axis RF Magnetron Sputtering Methods
Authors: Usagawa Toshiyuki , Yao Xin , Koyama Satoshi , Tanabe Keiichi , Izumi Teruo , Shiohara Yuh
Published: October 2002

Atomically flat surfaces of (110) oriented NdBa2Cu3O7-δ and/or YBa2Cu3O7-δ films grown on mechanically polished (110) NdBa2Cu3O7-δ single crystal substrates are confirmed by reflection high energy electron diffraction (RHEED) and scanning electron microscopy (SEM) observations. All of these thin films are grain free “epitaxial” films as smooth as (110) YBa2Cu3O7-δ homoepitaxial films [Usagawa et al..: Jpn. J. Appl. Phys. 36 (1997) L100.]. Our experimental results strongly suggest that the origin of the ultrasmooth surface morphology of (110) YBa2Cu3O7-δ (NdBa2Cu3O7-δ) films will be due to the inherent nature of (110) surfaces of 123 structures.
Photopumped Organic Solid-State Dye Laser with a Second-Order Distributed Feedback Cavity
Authors: Ichikawa Musubu , Tanaka Yuji , Suganuma Naotoshi , Koyama Toshiki , Taniguchi Yoshio
Published: October 2002

We describe a photopumped distributed feedback (DFB) organic solid-state dye laser consisting of an active layer containing a low-threshold gain-narrowing dye and an SiO2 DFB cavity based on second-order diffraction. A second-order diffraction grating is easy to fabricate compared with a first-order one having the same Bragg wavelength. When 4,4′-bis(4-(ditolyamino)styryl)biphenyl was used as the laser material, the threshold of the laser was 0.8 kW/cm2, a low value despite using a low-coupling-coefficient cavity based on second-order diffraction. This was a result of using a low-threshold gain-narrowing dye. Laser-light emission from the surface was observed, indicating that an organic “transverse cavity” surface-emitting laser could be developed using a second-order diffraction grating and a low-threshold gain-narrowing dye.
Cavity-Enhanced Detection System with an Optically-Feedbacked Diode Laser for Faraday Effect Measurements
Authors: Muroo Kazuyuki , Sato Ken , Takubo Yoshitaka
Published: October 2002

We present a cavity-enhanced spectroscopic detection system in which a single cavity serves two functions: signal enhancement and locking of a laser frequency. A GaAlAs diode laser was frequency-locked by optical feedback to the resonance of an external Fabry-Perot optical cavity into which a solenoid filled with air was placed. By measuring the Faraday rotation due to air subjected to a longitudinal magnetic field, we showed that the ratio of the effective optical path length to the single-pass length was 32.
Combinatorial Fabrication Process for a-Si:H Thin Film Transistors
Authors: Aiyer Hemantkumar N. , Nishioka Daikichi , Maruyama Ryuichirou , Shinno Hiroyuki , Matsuki Nobuyuki , Miyazaki Kaori , Fujioka Hiroshi , Koinuma Hideomi
Published: October 2002

A combinatorial approach is proposed and demonstrated for the parallel fabrication of a-Si:H, alloy and a-Si:H based devices, by employing simple masking schemes in conventional plasma-enhanced chemical vapor deposition (PECVD). The results are presented for a-Si:H thin film transistors. A (7×7) combinatorial device library was deposited on a (indium tin oxide/glass) substrate with the thicknesses of a-SiN:H and a-Si:H as combinatorial variables along the X and Y axes, respectively. Different a-Si:H TFTs in the library were evaluated to yield electrical performance with on-to-off current ratios exceeding 104 and threshold voltages from 0.3 to 4.5 V. Combinatorial PECVD offers an efficient and low cost means of studying the a-Si:H device performance and optimization.
Anomalous Transient Currents in Low-Density Polyethylene
Authors: Neagu Eugen R. , Marat-Mendes Jose N.
Published: October 2002

Transient currents in low-density polyethylene have been investigated at various temperatures, field strengths and for nonconditioned and conditioned samples, under vacuum and ambient air conditions. Anomalous charging and discharging currents have been observed. The anomalous discharging current is almost the mirror image of the anomalous charging current. Two patterns have been observed for temperatures below and above 50°C. Three characteristic zones have been identified, from which one may obtain information about dielectric polarization, bulk conduction effects and electrode effects and diffusion.
Fabrication of Defect-Free Surface-Stabilized Ferroelectric Liquid Crystals Using an Intervening Interfacial Layer with a Graded SmA–SmC* Transition Temperature
Authors: Furue Hirokazu , Nishiyama Isa , Yamamoto Jun , Yokoyama Hiroshi
Published: October 2002

Zigzag defects in surface-stabilized ferroelectric liquid crystals (SSFLCs) originate from the structural transformation from C1 to C2 chevrons during the cooling process. This transformation occurs so as to accommodate the increasing cone angle of the FLC under the constraint of the surface anchoring. Based on this scenario of defect formation, we propose a new scheme to obtain zigzag defect-free SSFLCs in which the C1–C2 transformation is suppressed by the use of an interfacial layer that has a gradually decreasing SmA–SmC* transition temperature toward the substrate.
Air Purification Effect of Positively and Negatively Charged Ions Generated by Discharge Plasma at Atmospheric Pressure
Authors: Nishikawa Kazuo , Nojima Hideo
Published: October 2002

In this paper, the air purification effect of positively and negatively charged ions generated by discharge plasma at atmospheric pressure is reported. We have developed a novel ion generation device which consists of a cylindrical glass tube and attached inner and outer mesh electrodes. With the application of AC voltage between the electrodes, positively charged ions and negatively charged ions have been generated at atmospheric pressure. The ion densities of 3.0×104–7.0×104 counts/cm3 have been obtained with the AC voltage of 1.8–2.3 kV (effective value). We have examined the air purification properties of this device. By the operation of this device, the initial oxygen nitride (NO) density of 10 ppm in 1 m3 (in cigarette smoke) was decreased to 1 ppm after 30 min. The number of suspended germs in air has been significantly reduced by the use of this type of ion generation device.
Study on Increasing the SO2 Removal Efficiency with the Radicals Produced by H2O in Pulse Discharge Plasma Process
Authors: Yan Wu , Jie Li , Ninghui Wang , Guofeng Li , Dexuan Xu
Published: October 2002

In this paper, the method of generating the radicals from H2O with positive DC corona discharge and the influence of the pin-plane electrode system on SO2 removal efficiency in the process of SO2 removal with pulse corona discharge were experimentally studied. The following results are obtained: the yield of the radicals produced by H2O was increased by the pin-plane electrode system, and the SO2 removal efficiency was increased by 10%; The total SO2 removal efficiency achieved was above 90%.
Mn-Activated Y2O3–GeO2 Phosphors for Thin-Film Electroluminescent Devices
Authors: Minami Tadatsugu , Yamazaki Masashi , Miyata Toshihiro , Shirai Tetsuya
Published: October 2002

A new multicomponent oxide phosphor, Mn-activated Y2O3–GeO2, is demonstrated to be very promising as the thin-film emitting layer for thin-film electroluminescent (TFEL) devices. High-luminance yellow emissions were obtained in TFEL devices using (Y2O3–GeO2):Mn thin films prepared with a GeO2 content of 0 to 100 mol%: 1756, 2500, 758 and 1629 cd/m2 in 1-kHz-driven TFEL devices fabricated using Y2O3:Mn, Y4GeO8:Mn, Y2GeO5:Mn and Y2Ge2O7:Mn phosphor thin films, i.e., a GeO2 content of 0, 33, 50 or 67 mol%, respectively. In addition, high luminous efficiencies of 2.8, 3.4, 1.5 and 4.5 lm/W, respectively, were obtained in these TFEL devices using a driving voltage at 60 Hz.
Fabrication of Novel Active Resistor Using Selective Metal Organic Chemical Vapor Deposition (MOCVD) for Monolithic Integration
Authors: Young-Jae Lee Young-Jae Lee , Young-Se Kwon Young-Se Kwon
Published: October 2002

Using selective epitaxial growth, we fabricated an active resistor in the floated electron channel field effect transistor(FECFET) structure. Compared to the active resistor in the metal semiconductor FET(MESFET) structure, it has large sheet resistance, depending on the number of stripes and etching time. For two SiO2 stripes, it is 600 Ω/w=50 µm and for twenty SiO2 stripes, its sheet resistance can reach 6000 Ω/\Box. Under light illumination, its current increases nonlinearly with the input light power like two-terminal FET without a gate.
Raman Spectroscopic Fingerprint of Ferroelectric SrBi2Ta2O9 Thin Films: A Rapid Distinction Method for Fluorite and Pyrochlore Phases
Authors: Osada Minoru , Kakihana Masato , Mitsuya Masatoshi , Watanabe Takayuki , Funakubo Hiroshi
Published: October 2002

We present the use of Raman spectroscopy as a rapid and sensitive means for the phase characterization of ferroelectric SrBi2(Ta1-x
Nb
x
)2O9 (SBTN) thin films. It is shown that frequency shifts, together with Raman selection rules, are characteristic of layered perovskite, fluorite and pyrochlore structures, and thus the Raman spectra can be used as a fingerprint of the symmetry of the examined film. We also find the enormous potential of Raman spectroscopy to detect and quantify fractions of the fluorite and pyrochlore phases coexistent with the SBTN phase.
Divalent Counterion Effect on the Electrostatic Persistence Length of Polyelectrolyte Chains: An Electric Birefringence Study
Authors: Frusawa Akihiro Fukagawa , Ito Kohzo , Hayakawa Reinosuke
Published: October 2002

We prepared salt-free polystyrenesulfonate (PSS) solutions with various ratios α of univalent and divalent counterions, i.e., X0.5αNa1-αPSS (X=Mg,Ca), and investigated them in the dilute region by means of the electrostatic birefringence spectroscopy that detects the rotational relaxations of polyelectrolyte chains. The obtained relaxation spectra show that, with replacing univalent counterions by divalent ones, the relaxation strengths decrease and the relaxation times gradually shift to higher values. From the rotational relaxation times, the electrostatic persistence length L
p for 0≤α≤1 is also evaluated using the worm-like chain model, which reveals that L
p with divalent counterions (i.e., α=1) becomes approximately half of that with univalent ones (α=0). The result suggests that the divalent counterion effect on conformations of intrinsically flexible polyelectrolyte is weaker than that expected from theoretical considerations.
Operation of InGaAs/InP-Based Ballistic Rectifiers at Room Temperature and Frequencies up to 50 GHz
Authors: M. Song Aimin , Pär Omling Pär Omling , Lars Samuelson Lars Samuelson , Werner Seifert Werner Seifert , Ivan Shorubalko Ivan Shorubalko , Herbert Zirath Herbert Zirath
Published: October 2002

Novel semiconductor rectifiers based on ballistic electron transport are fabricated from a high electron-mobility InGaAs/InP wafer. Because the device sizes are sufficiently small, operations at room temperature are achieved. Furthermore, the devices are shown to work not only at least up to 50 GHz but also with a sensitivity roughly the same as commercial microwave diodes, despite the fact that the devices have not yet been optimized. Aspects of using the devices in microwave applications are discussed in terms of the physical mechanism of the novel rectifying effect.
Anomalous Transport Behavior of a Binary Cd-Yb Icosahedral Quasicrystal
Authors: J. Sato Ryuji Tamura , Pan Tsai Ang
Published: October 2002

Electronic properties of the recently discovered binary Cd-Yb icosahedral(i) phase have been found to be strikingly different from those of ternary i-phases studied so far: The resistivity decreases rapidly (by 10–80% depending on the composition) with decreasing temperature down to about 10 K and levels off below 10 K. A giant magnetoresistance reaching as high as 200% at 9 T is observed at low temperatures. The electronic specific heat coefficient γ is very large, i.e., 2.87 mJ/(mole·K2), and the Debye temperature ΘD is as low as 140 K, which are in striking contrast with the trend observed in ternary i-phases. These anomalous features indicate that a different transport mechanism other than those proposed for ternary i-phases has to be considered for the present binary i-phase.
Latent Iron in Silicon
Authors: Choi Byoung-Deog , Schroder Dieter K. , Koveshnikov Sergei , Mahajan Subhash
Published: October 2002

It is usually assumed that the iron in iron-contaminated, boron-doped silicon exists as FeB pairs. The iron can be cycled between its interstitial (Fei) and paired (FeB) states with the total density Fei+FeB remaining constant. We have discovered that iron can also exist in other paired states, which we believe to be Fe-vacancy or Fe-implant damage pairs. When these pairs are destroyed and subsequently when FeB pairs form, we have observed an increased density. We refer to the excess iron (ΔFeB) after re-formation as “latent” iron.
Quaternary AlInGaN Multiple Quantum Wells for Ultraviolet Light Emitting Diodes
Authors: Zhang Jian Ping , Adivarahan Vinod , Wang Hong Mei , Fareed Qhalid , Kuokstis Edmundas , Chitnis Ashay , Shatalov Maxim , Yang Jin Wei , Simin Grigory , Khan Muhammad Asif , Shur Michael , Gaska Remis
Published: October 2002

We report on a novel pulsed atomic layer epitaxy (PALE) growth technique for quaternary AlInGaN films for ultraviolet optoelectronics applications. Using the PALE approach, quaternary AlInGaN/AlInGaN multiple quantum wells (MQWs) were successfully grown over sapphire substrates. These were characterized using X-ray diffraction, atomic force microscopy, and photoluminescence to establish structural and optical quality. Incorporating the PALE grown quaternary MQWs as the active layer we also demonstrated ultraviolet electroluminescence at 343 nm with an output power up to 0.12 mW at room temperature.
Novel Ridge-Type InGaN Multiple-Quantum-Well Laser Diodes Fabricated by Selective Area Re-Growth on n-GaN Substrates
Authors: Kuramoto Masaru , Kimura Akitaka , Sasaoka Chiaki , Arakida Takahiro , Nido Masaaki , Mizuta Masashi
Published: October 2002

A novel ridge structure fabricated by selective-area epitaxial re-growth is proposed for InGaN multiple-quantum-well (MQW) laser diodes (LDs). This technique is capable of precisely controlling the active ridge width and height, thus enabling stable single tran sverse-mode operation. Together with a backside n-contact on a low-dislocation-density GaN substrate, this structure provides high productivity and performance for GaN-based blue-violet LDs. A stable fundamental transverse mode up to 40 mW was demonstrated for the certain range of ridge dimensions. The minimum aspect ratio of the far-field patterns (FFPs) was about 2.1 in the fabricated ridge-type InGaN MQW LDs.
High-Efficiency Low Energy Neutral Beam Generation Using Negative Ions in Pulsed Plasma
Authors: Samukawa Seiji , Sakamoto Keisuke , Ichiki Katsunori
Published: October 2002

To prevent several kinds of radiation damage caused by charge build-up and by ultraviolet and X-ray photons during etching processes, we have developed a high-performance, neutral-beam etching system. The neutral-beam source consists of an inductively coupled plasma (ICP) source and top and bottom carbon parallel plates. The bottom carbon plate includes many apertures for extracting neutral beams from the plasma. By supplying a positive or negative direct current (DC) bias to the top and bottom carbon plates in the pulsed SF6 plasma, the generated positive or negative ions are respectively accelerated towards the bottom plate. The negative ions are more efficiently converted into neutral atoms in comparison with the positive ions, either by neutralization in charge-transfer collisions with gas molecules during the ion transport or with aperture sidewalls in the bottom plate. The neutralization efficiency of negative ions was more than 98% and the neutral flux density was equivalent to 4 mA/cm2.
Cosmology with the Sunyaev-Zel’dovich Effect
Authors: Carlstrom John E. , Holder Gilbert P. , Reese Erik D.
Published: October 2002

▪ Abstract  The Sunyaev-Zel'dovich effect (SZE) provides a unique way to map the large-scale structure of the universe as traced by massive clusters of galaxies. As a spectral distortion of the cosmic microwave background, the SZE is insensitive to the redshift of the galaxy cluster, making it well-suited for studies of clusters at all redshifts, and especially at reasonably high redshifts (z > 1) where the abundance of clusters is critically dependent on the underlying cosmology. Recent high signal-to-noise detections of the SZE have enabled interesting constraints on the Hubble constant and on the matter density of the universe using small samples of galaxy clusters. Upcoming SZE surveys are expected to find hundreds to thousands of new galaxy clusters, with a mass selection function that is remarkably uniform with redshift. In this review we provide an overview of the SZE and its use for cosmological studies, with emphasis on the cosmology that can, in principle, be extracted from SZE survey yields. We discuss the observational and theoretical challenges that must be met before precise cosmological constraints can be extracted from the survey yields.
Stellar Radio Astronomy: Probing Stellar Atmospheres from Protostars to Giants
Authors: Güdel Manuel
Published: October 2002

▪ Abstract  Radio astronomy has provided evidence for the presence of ionized atmospheres around almost all classes of nondegenerate stars. Magnetically confined coronae dominate in the cool half of the Hertzsprung-Russell diagram. Their radio emission is predominantly of nonthermal origin and has been identified as gyrosynchrotron radiation from mildly relativistic electrons, apart from some coherent emission mechanisms. Ionized winds are found in hot stars and in red giants. They are detected through their thermal, optically thick radiation, but synchrotron emission has been found in many systems as well. The latter is emitted presumably by shock-accelerated electrons in weak magnetic fields in the outer wind regions. Radio emission is also frequently detected in pre–main sequence stars and protostars and has recently been discovered in brown dwarfs. This review summarizes the radio view of the atmospheres of nondegenerate stars, focusing on energy release physics in cool coronal stars, wind phenomenology in hot stars and cool giants, and emission observed from young and forming stars.

Eines habe ich in einem langen Leben gelernt, nämlich, dass unsere ganze Wissenschaft, an den Dingen gemessen, von kindlicher Primitivität ist—und doch ist es das Köstlichste, was wir haben.

One thing I have learned in a long life: that all our science, measured against reality, is primitive and childlike—and yet it is the most precious thing we have.

   A. Einstein 1951, in a letter to H. Mühsam, Einstein Archive 36-610
Theory of Giant Planets
Authors: Hubbard W. B. , Burrows A. , Lunine J. I.
Published: October 2002

▪ Abstract  Giant planet research has moved from the study of a handful of solar system objects to that of a class of bodies with dozens of known members. Since the original 1995 discovery of the first extrasolar giant planets (EGPs), the total number of known examples has increased to ∼80 (circa November 2001). Current theoretical studies of giant planets emphasize predicted observable properties, such as luminosity, effective temperature, radius, external gravity field, atmospheric composition, and emergent spectra as a function of mass and age. This review focuses on the general theory of hydrogen-rich giant planets; smaller giant planets with the mass and composition of Uranus and Neptune are not covered. We discuss the status of the theory of the nonideal thermodynamics of hydrogen and hydrogen-helium mixtures under the conditions found in giant-planet interiors, and the experimental constraints on it. We provide an overview of observations of extrasolar giant planets and our own giant planets by which the theory can be validated.
The Evolution of X-Ray Clusters of Galaxies
Authors: Rosati Piero , Borgani Stefano , Norman Colin
Published: October 2002

▪ Abstract  Considerable progress has been made over the past decade in the study of the evolutionary trends of the population of galaxy clusters in the Universe. In this review we focus on observations in the X-ray band. X-ray surveys with the ROSAT satellite, supplemented by follow-up studies with ASCA and Beppo-SAX, have allowed an assessment of the evolution of the space density of clusters out to z ≈ 1 and the evolution of the physical properties of the intracluster medium out to z ≈ 0.5. With the advent of Chandra and Newton-XMM and their unprecedented sensitivity and angular resolution, these studies have been extended beyond redshift unity and have revealed the complexity of the thermodynamical structure of clusters. The properties of the intracluster gas are significantly affected by nongravitational processes including star formation and Active Galactic Nuclei (AGN) activity. Convincing evidence has emerged for modest evolution of both the bulk of the X-ray cluster population and their thermodynamical properties since redshift unity. Such an observational scenario is consistent with hierarchical models of structure formation in a flat low-density universe with Ωm ≃ 0.3 and σ8 ≃ 0.7–0.8 for the normalization of the power spectrum. Basic methodologies for construction of X-ray–selected cluster samples are reviewed, and implications of cluster evolution for cosmological models are discussed.
Human Endothelial Nitric Oxide Synthase Gene Delivery Promotes Angiogenesis in a Rat Model of Hindlimb Ischemia
Authors: Smith Robert S. , Lin Kuei-Fu , Agata Jun , Chao Lee , Chao Julie
Published: October 2002

Objective—

Endothelium-derived NO has been shown to mediate the mitogenic effect of vascular endothelial growth factor on cultured microvascular endothelium. To evaluate the role of endothelial NO synthase (eNOS) in angiogenesis in the ischemic hindlimb, we engineered an adenovirus containing human eNOS cDNA.

Methods and Results—

After gene transfer, expression of eNOS in cultured cells was detected by increased intracellular cGMP and nitrate/nitrite levels and NO synthase activity. Adenovirus containing either the eNOS or luciferase gene was injected into the adductor muscle of rat hindlimbs immediately after femoral artery removal. Human eNOS protein was detected throughout the course of the experiment by immunostaining. Significant increases in blood perfusion were monitored by laser Doppler imaging from 2 to 4 weeks after gene delivery in the ischemic hindlimb of rats receiving eNOS compared with control rats receiving the reporter gene. An increase in regional blood flow was also detected after eNOS gene transfer by a fluorescent microsphere assay. eNOS gene delivery in the ischemic hindlimb resulted in significant increases in intracellular cGMP levels and in capillary density identified by anti–CD-31 immunostaining. Angiogenesis was further confirmed in mice after eNOS gene transfer by increased hemoglobin content in Matrigel implants.

Conclusions—

Taken together, these results indicate that eNOS enhances angiogenesis and raises the potential of eNOS gene transfer for modulation of vascular insufficiency.
Application of Ex Vivo Flow Chamber System for Assessment of Stent Thrombosis
Authors: Sakakibara Mamoru , Goto Shinya , Eto Koji , Tamura Noriko , Isshiki Takaaki , Handa Shunnosuke
Published: October 2002

Objective—

Factors influencing platelet accumulation around stents were to be investigated by an ex vivo flow chamber system.

Methods and Results—

Platelet accumulations on collagen surfaces under flow conditions were augmented in the presence of stents, especially at sites downstream from coil stents. Densitometric analysis revealed that 4.9±0.8 times more platelets accumulated downstream from coil stents than were formed downstream from tube stents (
P
<0.01), suggesting that stent morphology is an important determinant factor of its thrombogenicity. Platelet accumulations around stents were significantly inhibited by a combination of ticlopidine and aspirin, whereas aspirin alone produced only modest inhibition. Anti–glycoprotein IIb/IIIa (abciximab) inhibited platelet accumulation around stents in a dose-dependent manner, whereas the antibody blocking von Willebrand factor binding to glycoprotein Ibα, which had been shown to inhibit platelet thrombus formation under high shear rates, did not inhibit the accumulation downstream from the coil stents. Our results suggest that the important characteristics of in vivo stent thrombosis, ie, augmented platelet accumulation with coil stents and the strong antithrombotic effect of the combination antiplatelet agents and an anti–glycoprotein IIb/IIIa, can be reproduced in ex vivo perfusion model.

Conclusions—

We conclude that an ex vivo perfusion system is useful in the assessment of the thrombogenicity of various stents and in the screening of effective antiplatelet agents.