bluuebunny/crossref_metadata_2025 huggingface dataset:
New Technique for Suppressing Oxygen Impurity in AlGaAs Layer during Molecular Beam Epitaxy by Surface Segregation
Authors: Naritsuka Shigeya , Kobayashi Osamu , Mitsuda Kazuhiro , Nishinaga Tatau
Published: July 2005

A new technique for decreasing oxygen concentration in the AlGaAs layer during molecular beam epitaxy (MBE) is proposed on the basis of oxygen incorporation. In this technique, the growth temperature is successively decreased at each interface where the AlAs mole fraction is changed. The secondary ion mass spectroscopy (SIMS) analysis indicates that both oxygen concentration near the active layer and the oxygen peaks at each interface, which are commonly observed using the layer grown by a conventional method, are effectively suppressed by the new technique. The laser diode fabricated from the wafer shows characteristics superior to those of the lasers fabricated by a conventional method. For example, the threshold current density is as low as 1.1 kA/cm2.
Suppression of Thermally Induced Leakage of NiSi-Silicided Shallow Junctions by Pre-Silicide Fluorine Implantation
Authors: Tsuchiaki Masakatsu , Ohuchi Kazuya , Nishiyama Akira
Published: July 2005

Thermally unstable NiSi films on shallow junctions induce a large leakage current upon heat treatment. To improve their thermal stability, using damage-free junctions formed by solid-phase diffusion, a sensitive and comparative investigation is conducted on the efficacy of pre-silicide ion implantation (PSII) of fluorine and nitrogen. After annealing NiSi silicided junctions, the basic and systematic monitoring of thermally induced leakage revealed that leakage suppression strongly depends on the element being implanted, i.e., F-PSII is found to be markedly superior to N-PSII. Even at a low F dosage, F-PSII attains a uniform and efficient leakage suppression of up to 6 orders of magnitude. Furthermore, unlike N-PSII, the suppression is achieved without any major disturbances to the critical characteristics of complementary metal-oxide-semiconductor transistors (CMOS) for ULSI application. The distinctive F presence around the NiSi/Si interface confers a substantial thermal stability to the NiSi film. The resulting effective blockage of Ni infiltration into a Si substrate, as well as the complete immobilization of Ni migration inside the Si substrate, leads to a drastic leakage suppression by F-PSII.
Optical Nutation in Cold 85Rb Atoms
Authors: Shim Unyob , Cahn Sidney B. , Kumarakrishnan Anantharaman , Sleator Tycho , Kim Jin-Tae
Published: July 2005

We have observed optical nutation in cold 85Rb atoms with a negligible Doppler broadening. The optical nutation of a two-level atom arranged by optical pumping has been studied as a function of detuning frequency and Rabi frequency. The change of the nutation signal caused by magnetic substate degeneracy has also been observed for σ and π excitations. This can be explained by optical nutation beatings from different transition probabilities among magnetic sublevels. Absolute transition probabilities with σ and π transitions and a branching ratio between them have been measured.
Modeling of Two Different Operation Modes of Phase Change Material for Phase-Change Random-Access Memory
Authors: Zhang Yi , Feng Jie , Wang Hao , Cai Bingchu , Chen Bomy
Published: July 2005

Two basic models for phase-change random-access memory (PRAM) are compared for the first time. Model 1 is based on polycrystalline Ge2Sb2Te5, and the phase change takes place only in some of the film. Model 2 is based on amorphous Ge2Sb2Te5. This work indicates that model 1 has an excellent R
OFF/R
ON, but inferior structure and reset current. Model 2 has superior structure and reset current, but inferior R
OFF/R
ON. Therefore, for model 2, it is important to control the thickness of nonprogrammable volume to ensure sufficient R
OFF/R
ON and the proper range of the ratio of non-programmable volume and programmable volume is calculated as 0.003–1%. The simulation result shows the temperature distribution of model 2 can satisfy the actual requirement well, and the reset current can be reduced to 0.15 mA, much lower than that in model 1.
Study on Oxynitride Buffer Layers in HfO2 Metal–Insulator–Semiconductor Structures for Improving Metal–Insulator–Semiconductor Field-Effect Transistor Performance
Authors: Ota Hiroyuki , Yasuda Naoki , Yasuda Tetsuji , Morita Yukinori , Miyata Noriyuki , Tominaga Koji , Kadoshima Masaru , Migita Shinji , Nabatame Toshihide , Toriumi Akira
Published: July 2005

In this study, we investigate effects of various buffer layers on the electrical properties of HfO2 metal–insulator–semiconductor (MIS) structures under fixed conditions for HfO2 deposition and postdeposition annealing. The buffer layers are prepared using several processes including oxidation, oxynitridation and nitridation. The equivalent oxide thickness (EOT), the flat-band voltage and the flat-band voltage hysteresis of the HfO2 MIS structures depend on the nitrogen density per unit area in oxynitride buffer layers. We reveal that the increase of EOT due to postdeposition annealing is suppressed by a certain amount of nitrogen density in oxynitride buffer layers. Based on the results, we propose an engineering methodology for the nitrogen composition and the physical thickness of the oxynitride buffer layers so as to obtain a high-performance MIS field-effect transistors.
The Instability of Nitrogen Bonds in Oxygen Incorporated InN1-xOx Films
Authors: Yi Yeonjin , Cho Sangwan , Roh Yongsuk , Noh Myungkeun , Whang Chung-Nam , Jeong Kwangho , Shin Hyun-Joon
Published: July 2005

The polycrystalline InN1-x
O
x
films with different oxygen contents were grown by the reactive radio frequency (RF) magnetron sputtering on corning 1737 glass substrates. The chemical composition of each film was measured by the Rutherford back-scattering spectroscopy (RBS). The crystal structure and band gap of each film were examined with X-ray diffraction (XRD) and ultra violet (UV) light transmission spectroscopy, respectively. Results indicated the gradual shift from nitride to oxide as the oxygen incorporation in InN film increased. X-ray absorption spectra identified four possible phases in the film, indium–nitride, indium–oxide, atomic nitrogen and nitrogen–oxygen complex (In–N–O).
Characteristics of the Inter-Poly Al2O3 Dielectrics on NH3-Nitrided Bottom Poly-Si for Next-Generation Flash Memories
Authors: Chen Yeong-Yuh , Chien Chao-Hsin , Lou Jen-Chung
Published: July 2005

The effects of surface NH3 nitridation of the bottom poly-Si film, and post-deposition annealing (PDA) temperature, on the electrical properties and reliability characteristics of aluminum oxide (Al2O3) inter-poly capacitors, were evaluated in this study. The polarity-dependent dielectric properties of Al2O3 inter-poly dielectrics (IPDs) were strongly affected by both surface nitridation and the annealing temperature. For positive gate bias, IPDs with NH3 surface nitridation significantly suppressed the formation of an additional layer with a lower dielectric constant, during the post-annealing process, and obtained a smoother interface, compared to those without nitridation treatment. Furthermore, the presence of a thin Si–N layer made the PDA more effective in eliminating the traps existing in the as-deposited films, and improved dielectric characteristics, under negative polarity. As a result, the smoother interface and smaller electron trapping rate contributed to the drastically reduced leakage current, enhanced breakdown field, and charge to breakdown (Q
bd) of the Al2O3 inter-poly capacitors with surface NH3 nitridation. Moreover, the electrical properties of Al2O3 IPD were heavily dependent upon the PDA temperature. The sample exhibited optimal quality in terms of leakage current, electron trapping rate and Q
bd when annealed at 900°C. X-ray photoelectron spectroscopy and Auger electron spectroscopy analyses have shown that this occurrence arises from various compositions, under different annealing conditions and excess oxygen, which can act as an electron trapping center, playing an important role in determining IPD electrical properties.
Scaling Impacts on Electromigration in Narrow Single-Damascene Cu Interconnects
Authors: Yokogawa Shinji , Tsuchiya Hideaki
Published: July 2005

In this paper, we present scaling impacts on electromigration-induced mass transport in narrow single-damascene Cu interconnects. Linewidths ranging from 0.12 µm to 0.20 µm were used to demonstrate the impacts. Lifetimes that are determined by resistance degradation decrease according to decreasing linewidth at a fixed current density. This is caused by a decrease in effective incubation time and an increase in drift velocity. The product of drift velocity and the square of the linewidth has a linear dependence on current density. The activation energy is 1.2 eV for the effective incubation time, and 1.1 eV for the drift velocity. The values are independent of the linewidth. The activation energy suggests that the effective incubation time is the time to void growth from the Cu/SiCN interface to the trench bottom through Cu grain boundaries. The grain boundaries provide nucleation sites for void growth in bamboo structures. Similarly, interface diffusion at the Cu/metal liner on the sidewalls of the line contributes to void growth.
Deep-Level Defects in AlGaN/GaN Heterostructures Grown Using rf-Plasma-Assisted Molecular Beam Epitaxy
Authors: Park Chan Jin , Park Young Shin , Lee Ho Sang , Yoon Im-Taek , Kang Tae Won , Cho Hoon Young , Oh Jae-Eung , Wang Kang L.
Published: July 2005

Gallium nitride heterostructures sandwiched between AlGaN layers have been grown on sapphire substrates using rf-plasma-assisted molecular-beam epitaxy (MBE), and their electrical properties investigated. Deep-level transient spectroscopy (DLTS) measurements reveal that the activation energies of the two electron levels were 0.21 eV and 0.23 eV relative to the conduction band, with capture cross sections of 5.0×10-15 cm2 and 7.4×10-17 cm2, respectively. From the capture kinetics of the deep-level defects, according to the filling pulse duration and the bias voltage, it is suggested that the 0.21 eV defect is associated with nitrogen vacancies and the 0.23 eV defect is associated with extended defects.
Additional Plasma Surface Texturing for Single-Crystalline Silicon Solar Cells Using Dielectric Barrier Discharge
Authors: Sakoda Tatsuya , Matsukuma Kunihiro , Sung Youl-Moon , Otsubo Kouji , Tahara Minoru , Nakashima Yoshihiro
Published: July 2005

To reduce the light reflection from surfaces of single-crystalline solar cells, a new surface texturing technique using a dielectric barrier discharge was proposed and examined on wet-textured surfaces of single-crystalline Si substrates. Minute uneven structures were additionally formed on the entire area of a wet-textured surface of pyramid-like shape. When the discharge voltage was 3.5 kV, the reflectance was less than 8% at wavelengths from 400 to 1000 nm and showed a minimum of 5.3% at 520 nm.
Optical Characteristics of GaN Films Overgrown on Wet-etched GaN Templates
Authors: Tsai Yu-Li , Gong Jyh-Rong , Lin Kun-Ming , Lin Der-Yuh , Chen Edwin Chinhong
Published: July 2005

GaN films were deposited on wet-etched GaN templates having various etch pit sizes. Improved optical characteristics of the overgrown GaN films were observed including a remarkable increment in photoluminescence (PL) intensity and a considerable reduction in emission linewidth of the near bandedge (BE) emission. Improvement of the optical property of an overgrown GaN film is attributed to a selective elimination of threading dislocations (TDs) which results in a reduction of etching pit density (EPD) count of the overgrown GaN film.
Liquid Phase Epitaxial Growth of (Bi, Lu)3(Fe, Ga)5O12 Films with In-Plane Anisotropy for Magneto-Optical Imaging
Authors: Iida Kazumasa , Kawamae Norio , Hoshi Saburo , Machi Takato , Kono Takeshi , Yoshioka-Kato Junko , Chikumoto Noriko , Koshizuka Naoki , Adachi Nobuyasu , Okuda Takashi
Published: July 2005

The key factors in the liquid phase epitaxial growth of (Bi, Lu)3(Fe, Ga)5O12 garnet films with in-plane anisotropy for magneto-optical imaging, MOI, have been investigated. The role of stress induced magnetic anisotropy caused by the lattice misfit between the film and substrate, in particular, was examined. We found that it was necessary to control precisely the lattice misfit in the operating temperature region of the MOI indicator. The (100) orientation of Gd3Ga5O12(GGG) substrates is preferable to the (111) orientation for the fabrication of in-plane films in case of the same saturation magnetization. By using the film, magnetic flux penetration through the grain boundaries of an Y–Ba–Cu–O bulk sample was observed clearly with high resolution.
Analytic Calculation of Absorption Efficiency for Double-Clad Fibers Using Modal Method
Authors: Wang Zi Hua , Xu Sheng
Published: July 2005

The absorption efficiency for circular or offset double-clad optical fibers is investigated with modal analysis method. First, calculate the number of all the propagating modes approximately using WKB method and derive the analytic formulas for calculating the number of propagating modes that can't be absorbed by active core. Then the absorption efficiency can be obtained analytically. Comparison of modal method with the ray optics method is made and the condition of using both methods is also discussed.
Optimizing the Universal Visible Antireflection Coating Design for Substrates by Exchanging Search Algorithms
Authors: Liou Yeuh-Yeong , Liu Yu-Tsung
Published: July 2005

A design algorithm, based on the exchanging search technique, was used for optimizing the visible antireflection coating design of substrates with refractive indices ranging from 1.45 to 1.784. In this method, a tuning operation for the layer thicknesses of a two-material multilayer assembly was first carried out, followed by an exchanging operation for further refining the visible antireflection performance and simplifying the design structure. The average visible reflectivities of two-material thirty-layer exchanging search universal antireflection coating designs for a set of eight different substrates with indices 1.45, 1.50, 1.55, 1.60, 1.65, 1.70, 1.75 and 1.784 were reduced to approximately 0.172–0.174% with 12–14 layer structures.
Development of Distributed-Feedback Tunable Blue-Violet Waveguide Plastic Laser Based on Fluorene Compound
Authors: Oki Yuji , Sato Hitoshi , Abe Aki , Watanabe Hirofumi , Era Masanao , Maeda Mitsuo
Published: July 2005

The distributed feedback plastic lasers for blue-violet were developed. The developed fluorene molecules for electroluminescence devices were adopted and doped in poly(methymethacrylate:2-hydroxyethylemethacrylate). Laser operation was confirmed at a wavelength of about 410 nm using frequency-tripled and passively Q-switched Nd:Cr:YAG laser. A laser threshold of 70 nJ and the longest lifetime of 3000 shots were demonstrated.
Development of Nd-doped Optical Gain Material Based on Silica Glass with High Thermal Shock Parameter for High-Average-Power Laser
Authors: Fujimoto Yasushi , Yoshida Hidetsugu , Nakatsuka Masahiro , Ueda Tetsuji , Fujinoki Akira
Published: July 2005

In this paper, we report a demonstration of amplification at 1.06 µm in a bulk-type Nd-doped silica glass (Nd2O3: 1.25 wt%, Al2O3: 2.72 wt%, SiO2: 96.03 wt%) with a high thermal shock parameter for the first time. The optical gain of 1.75 was obtained in a 93-mm-long sample with a flash lamp pumping at 1.9 kJ, corresponding to a gain coefficient of 0.06 cm-1. The thermal shock parameter of Nd-doped silica glass was measured to be 12.0 W/cm, which is thirty times greater than that of phosphate glass and one and a half times greater that of Nd:YAG. We carried out a quick quenching experiment to determine the thermal shock toughness of Nd-doped silica glass, and the experiment demonstrated that the thermal shock toughness of Nd-doped silica glass was superior to that of the phosphate laser glass. We also calculated the thermal stress distribution in Nd-doped silica glass with a simple model for comparison with the experimental results; the model well explains the experimental results. These results indicate that Nd-doped silica glass can produce a compact, high-energy density, and high-average-power laser.
Electric Field Imaging Using Intense Half-Cycle Terahertz Pulses
Authors: Rungsawang Rakchanok , Tukamoto Keiji , Hattori Toshiaki
Published: July 2005

Characteristics of terahertz (THz) imaging using approximately half-cycle THz pulses were studied using a large-aperture biased photoconductive antenna which emits an intense THz field with a large THz beam. Studies of the dependence of the THz image quality on delay time show that real-time imaging is possible if the probe pulse is timed appropriately. The best images were observed at a time window when the THz field had a steep transient. This allows two-dimensional imaging in a fixed-time mode, which enables observation of a nonstationary object. Using phase-sensitive electrooptic detection and scanning a delay time, not only two-dimensional time-domain spectroscopy is possible, but frequency-resolved images are also available. Depending on the frequency, we found that images of the actual shape or the edge of an object were obtained.
Polarization-Independent Tuning of Widely Tunable Vertically Coupled Microring Resonator Using Thermo-Optic Effect
Authors: Sekiguchi Go , Yamagata Shunichi , Kokubun Yasuo
Published: July 2005

The polarization independent tuning of the resonant wavelength of a vertically coupled microring resonator (VCMRR) filter is demonstrated using the thermo-optic effect in a polymer ring core. The polarization dependence of the tunability of a TO-tunable microring resonator was reduced to 3% using a new polymer with a high index contrast and a small birefringence for the ring core. Approximately 12.9 nm tuning was successfully demonstrated.
Microlenses Fabricated on Silicone Rubber Using F2 Laser
Authors: Takao Hiromitsu , Miyagami Hideyuki , Okoshi Masayuki , Inoue Narumi
Published: July 2005

Microlenses are fabricated on silicone rubber surfaces employing phenomena in which silicone rubber swells and is modified to SiO2 by F2 laser irradiation at a laser fluence lower than the ablation threshold. In this method, silicone rubber is irradiated using a F2 laser beam through a mask which has circular apertures 10, 20, and 25 µm in diameter. Since silicone rubber swells by laser irradiation, it is necessary to separate the mask from the silicone rubber surface. The swelling is spherical and its surface becomes smooth when the distance between the mask and the silicone rubber surface is very small. The focal lengths of the microlenses are 10–170 µm, which are controlled by adjusting the number of irradiated pulses. Additionally, a 790 nm femtosecond laser beam is focused by the fabricated microlenses, and enables the microdrilling of fluorinated rubber.
Thermal Expansion of Nonlinear Optical Crystal La2CaB10O19
Authors: Jing Fangli , Wu Yicheng , Fu Peizhen , Guo Rui
Published: July 2005

The thermal expansion coefficients of the nonlinear optical crystal La2CaB10O19 (LCB) were measured along three crystallographic axes (a, b, c) and in another direction marked with d, which lay in the (010) plane with the angle between a and d equal to 45°. Thermal expansion measurements were carried out in the temperature range between 25°C and 300°C. The experimental data obtained were 8.642×10-6, 8.387×10-6, 2.266×10-6 and 5.813×10-6 K-1, respectively. The changes of lattice constants for a, b, and c were calculated. The three principle expansion coefficients were calculated to be 8.665×10-6 K-1, 8.387×10-6 K-1 and 2.261×10-6 K-1, respectively. The anisotropy of the structure of the La2CaB10O19 crystal leads to the anisotropic thermal expansion property.
Multiple-Beam Liquid Crystal Grating for the Recordable Optical Pickup Head
Authors: Shih Hsi-Fu
Published: July 2005

By combining the technology of a liquid crystal diffractive optical element with that of a multiple-beam grating, a novel multiple-beam liquid crystal grating is proposed for the application of recordable optical pickup heads. This grating has the function of generating seven diffracted beams with equal intensity in each order while applying a voltage to the device. It provides the switching ability between the single beam and multiple beams for writing data and reproducing data, respectively.
Efficient Polarized Backlight for Transflective Liquid Crystal Display Illumination
Authors: Chien Ko-Wei , Shieh Han-Ping D. , Cornelissen Hugo J.
Published: July 2005

A collimated backlight was designed for high-efficiency transflective liqud crystal display (LCD) illumination. Additionally, polarization separation was achieved by selective total internal reflection at microgrooves in polymeric foils, which were stretched to be anisotropic materials for easy fabrication and tunable birefringence. A lenticular lens array was then utilized to collect the collimated light of the polarized backlight to further improve light utilization efficiency. Therefore, gains of 2.91 and 1.37 in light utilization efficiency were obtained for transmissive and reflective modes, respectively.
Physical Properties of Bi-Based Rhodium Oxides with RhO2 Hexagonal Layers
Authors: Okada Satoshi , Terasaki Ichiro
Published: July 2005

We have synthesized polycrystalline samples of (Bi1-x
Pb
x
)1.8Sr2Rh1.6O
y
(x=0, 0.1, 0.2) by solid-state reaction. This compound is the first synthesized misfit oxide without cobalt. The obtained X-ray diffraction pattern indicates that this compound has the same structure as the thermoelectric oxide Bi2Sr2Co2O
y
. The thermopower and the resistivity are 125 µV/K and 0.47 Ωcm at room temperature, respectively. We have further prepared polycrystalline samples of Bi1.8Ba2Rh1.9O
y
, and have found that the thermopower and resistivity of Bi1.8Ba2Rh1.9O
y
are 86 µV/K and 19 mΩcm at room temperature, respectively. These data are comparable to those of the thermoelectric Co oxides.
Effects of Glass Addition on Microwave Dielectric Properties of Zn0.95Mg0.05TiO3 + 0.25TiO2 Ceramics
Authors: Lee Ying-Chieh , Lee Wen-Hsi
Published: July 2005

The effects of Bi2O3 addition on the microwave dielectric properties and the microstructures of Zn0.95Mg0.05TiO3 + 0.25TiO2 with 1 wt% 3ZnO–B2O3 (ZnBO–ZMT') ceramics prepared by conventional solid-state routes have been investigated. In a preliminary study, it was shown that ZnBO–ZMT' ceramics can be sintered to a theoretical density higher than 95% at 900°C. In this study, the effects of Bi2O3 additions of up to 10 wt% on the sintering characteristics of the ZnBO–ZMT' ceramics was investigated at the sintering temperatures ranging from 860 to 960°C. Sintered ceramic samples were characterized by X-ray diffraction and scanning electron microscopy (SEM). It was found that as the content of Bi2O3 increases, the density of the sintered ceramics increases, and the sintering temperature can be lowered to 880°C by adding 5 wt% Bi2O3. The ZnBO–ZMT' ceramic with 5 wt% Bi2O3 addition sintered at 880°C exhibits the optimum dielectric properties: Q×f=4000 GHz, ε
r=24.6, and τf=-14 ppm/°C. Unlike the ZnBO–ZMT' ceramic without Bi2O3 addition sintered at above 920°C, the ceramics with Bi2O3 additions show no Zn2TiO4 existence at 960°C sintering. It is therefore demonstrated that the addition of Bi2O3 can suppress the formation of Zn2TiO4 in ZnBO–ZMT' ceramics.
Using Shear Horizontal Surface Acoustic Wave with Polyaniline Film as Ammonia Sensor
Authors: Shen Yu-Tang , Huang Cheng-Liang , Wu Long
Published: July 2005

A shear horizontal surface acoustic wave (SH-SAW) sensor coated with polyaniline (PANI) was investigated in this study. The SH-SAW phase and attenuation were measured using a network analyzer. The sensor presented a sensitivity of 0.23 deg/ppm at 25°C. The minimum detection level was estimated to be 0.07 ppm at 25°C. Otherwise, the response of the SH-SAW sensor immediately followed the ammonia gas concentration. Hence, the SH-SAW coated with PANI exhibited an excellent response for detecting ammonia at room temperature.
Preparation and Characterization of Ceramic/Ceramic Composite Films
Authors: Cheung Mei-Kuen , Kwok Kin-Wing , Chan Helen L. W. , Choy Chung-Loong
Published: July 2005

A new sol–gel-based method has been developed for fabricating dense and crack-free ceramic/ceramic composite films. The new method simply combines the modified sol–gel method together with the infiltration technique. A slurry comprising lead zirconate titanate (PZT) ceramic powder dispersed in a PZT precursor solution was first prepared and deposited on a silicon substrate by the spin-coating technique to form a composite film. The large number of pores generated in the film was then infiltrated by the subsequent deposition of a diluted PZT precursor solution. This additional infiltration process has been shown to be successful and effective in reducing porosity and the resulting PZT/PZT composite films retain good dielectric, ferroelectric and pyroelectric properties. Our results also reveal that the relative permittivity and pyroelectric coefficient of composite films increase as the PZT powder volume fraction φ increases, in accordance with similar dependences predicted by the theoretical models. For a PZT/PZT composite film with φ=0.37 and a thickness of 2.5 µm, the observed relative premittivity, dielectric loss, remanent polarization and pyroelectric coefficient are 1150, 0.037, 21 µC/cm2 and 188 µC/m2K, respectively.
Longitudinal and Lateral Vibrations of a Planar Piezoceramic Transformer
Authors: Karlash Valeriy
Published: July 2005

Recently, the author has investigated the characteristics of Rosen-type piezotransformer with accounting the difference in elastic compliances of input and output sections. The refined formula has been derived for a transform ratio. It was established that a transform ratio is inversely proportional to a square frequency. This fact explains why an operation of the planar transformers at higher modes of vibrations is not effective. The longitudinal mechanical stresses in excite and generate sections of the transformer are axisymmetric in respect to the separating line that is in good matching with the experimental data. In this paper, the previous authors results are used for analyse of the modes of vibrations, frequency behaviour of the transform ratio and input admittance of transverse-longitudinal transformer. The spectrum of vibrations of the piezotransformer compares with that of rectangular piezoelectrtic plate. It is shown that piezoplate has more rigid spectrum than piezotransformer. The coupling between lateral and longitudinal vibrations in piezoplate and piezotransformer is similar.
Liquid Crystal Alignment Control Using Polymer Filament and Polymer Layers Coated on Substrates
Authors: Murashige Takeshi , Fujikake Hideo , Sato Hiroto , Kikuchi Hiroshi , Kurita Taiichiro , Sato Fumio
Published: July 2005

We investigated liquid crystal (LC) alignment in LC cells containing an aligned cellulose filament sandwiched by thin polymer layers coated on substrates. Three types of polymer material, namely polystyrene (PS), polyvinyl alcohol (PVA) and polyimide (PI), were used as polymer layers. LC alignment areas induced on both sides of the filament were large in the order of PS, PVA and PI. In the case of the PS layer, the average LC alignment area reached approximately 100 µm in the direction perpendicular to the polymer filament. The molecular interaction between the LC and the PS layer is thought to be weak and it does not disturb the LC alignment due to the polymer filament. On the other hand, rubbed PS layers were used as polymer layers of the LC cell, where the LC alignment direction induced by the rubbed PS layer was perpendicular to the polymer filament. It was found that the LC alignment near the polymer filament gradually bent in the cell plane. The result suggests that various three-dimensional LC alignments can be realized by the combination of the polymer filament and substrate surface.
Novel Structure for Reduced Operating Voltage in Fringe-Field Switching Mode with Negative Liquid Crystal
Authors: Park Jun Baek , Kim Hyang Yul , Kim Kwi Hyun , Kim Seo Yun , Lim Young Jin
Published: July 2005

A novel structure for the fringe-field switching (FFS) mode for negative liquid crystal is proposed to lower the operating voltage compared to that of conventional structures. The novel structure consists of a patterned oxide layer between pixel electrodes (second ITO) and the decrease of oxide thickness between common (first ITO) and pixel electrodes. The electric field strengthened by the novel structure results in higher transmittance, especially at the center position of the electrode space at low voltage; as a result, V
op at that position decreases, but the maximum transmittance decreases because of an increase in the retardation and a decreasing slope of V–T curve over V
op at that position becomes steeper. Finally, the total V
op decreases primarily because of the decrease in V
op at the center position of the electrode space.
Two-Domain Hybrid-Aligned Nematic Cell Fabricated by Ion Beam Treatment of Vertical Alignment Layer
Authors: Gwag Jin Seog , Park Kyong-Ho , Lee Jong Lac , Kim Jae Chang , Yoon Tae-Hoon
Published: July 2005

Organic materials for vertical alignment can be used to align liquid crystals horizontally by irradiating an ion beam on the surface under appropriate conditions. Using this technique, we can achieve easily a multidomain alignment for a hybrid-aligned nematic (HAN) cell. We found that a two-domain HAN cell obtained by ion beam exposure shows excellent electro-optical characteristics. The use of the same alignment material in a HAN cell could reduce the cost of production and generation of DC offset voltage.
Structure of Oxygen-Related Defect Centers in Ge1-xSix Alloys Studied by Extended Energy-Loss Fine Structure Analysis
Authors: Muto Shunsuke , Sugiyama Hiroshi , Yonenega Ichiro , Tanabe Tetsuo
Published: July 2005

Oxygen atoms dissolved near the surface regions in Ge1-x
Si
x
alloys were studied by extended energy-loss fine structure (EXELFS) analysis using electron energy-loss spectroscopy (EELS) and the local structures around oxygen were determined. Oxygen preferentially formed Si–O–Si centers, rather than Si–O–Ge or Ge–O–Ge. The O–Si bond length was increased with decreasing the Si content, in accordance with the increase in the Si–Si, Si–Ge and Ge–Ge bond lengths. The increase in O–Si bond length is much more significant than that expected from the changes in Si–Si, Si–Ge and Ge–Ge bond lengths. The derived local atomic configuration of the Si–O–Si center changed with increasing Si content, which corresponds well to the surface oxidization process of crystalline silicon.
Structural Analysis of LiTaO3(0001) Surfaces Using Low-Energy Neutral Scattering Spectroscopy
Authors: Kawanowa Hitoshi , Ozawa Hidenori , Gotoh Yoshihiko , Souda Ryutaro
Published: July 2005

The atomic structure of the LiTaO3(0001) surface was investigated by low-energy neutral scattering spectroscopy (LENS). LENS was developed for surface-structure and -composition analyses, particularly of highly insulating materials, and was successfully applied to the structural analysis of the LiTaO3(0001) surface. The polar angle dependences of scattered He0 intensities indicate that O atoms cover the surfaces. The surface structure is almost the same as the bulk structure truncated at the (0001) plane, and the layer spacings between the first Li, the Ta and the outermost O layer are 0.01±0.01 nm and 0.09±0.01 nm, respectively.
In situ Monitoring of Surface Processes in Plasma by Coaxial Impact-Collision Ion Scattering Spectroscopy
Authors: Fujii Shunjiro , Katayama Mitsuhiro , Michishita Yusuke , Oura Kenjiro
Published: July 2005

We demonstrated in situ monitoring of surface processes in plasma, using coaxial impact-collision ion scattering spectroscopy (CAICISS) operable in a gas atmosphere, taking the plasma nitridation processes of Si surfaces with (111) and (001) faces as examples. From the results of real-time monitoring of CAICISS spectra, it was found that (1) the top layer of the Si(111) surface is readily nitrided even at room temperature, while the Si(001) surface requires thermal activation for its nitridation and that (2) at a high temperature, the nitridation of Si(001) proceeds to layers deeper than in the case of Si(111).
Evaluation of the Correspondence between Carbon Incorporation and the Development of c(4×4) Domains
Authors: Harashima Masayuki , Yasui Kanji , Moriyama Manabu , Takata Masasuke , Akahane Tadashi
Published: July 2005

Using the temperature programmed desorption (TPD) method and a scanning tunneling microscope (STM), the correspondence between carbon incorporation into a Si(001) substrate and the development of a c(4×4) area on a surface has been investigated. In TPD spectra, γ peaks have been observed for substrates exposed to various amounts of monomethylsilane (MMS) at 660°C, which indicates the occurrence of carbon incorporation into the subsurface layer. From estimations, it has been found that the area of a γ peak is increased with exposure time. On the other hand, STM images have revealed that a c(4×4) surface consists of both (2×1) domains and c(4×4) domains. As the amount of MMS exposure increases, the c(4×4) domain expands and the entire surface is covered with a c(4×4) structure at 280 L. By comparing the area of a γ peak with the c(4×4) coverage at each exposure condition, it has been found that the relationship between them is approximately linear.
Fabrication of Zinc Oxide Transparent Thin-Film Transistor with ZrO2Insulating Layer by Sol–Gel Method
Authors: Ohya Yutaka , Kume Takashi , Ban Takayuki
Published: July 2005

A thin-film transistor consisting of a ZnO active layer and a ZrO2insulating layer was fabricated on a tin-doped indium oxide sputtered glass substrate as well as on a SiO2/Si wafer. The ZnO and ZrO2layers were deposited by a sol–gel, dip-coating procedure. The resultant ZrO2layer was about 150 nm thick and the ZnO layer 70 nm thick. The ZnO layer consisted of a single-grain thickness while the ZrO2layer consisted of about 10 nm grains and was rather porous. The multilayered film consisting of ZnO/ZrO2/ITO/glass was transparent with 60–85% transmittance in the visible region and exhibited characteristics of a field-effect transistor. The multilayered film of the ZnO/ZrO2/SiO2/Si wafer was also examined and the behavior of the thin-film transistor was confirmed. The ZrO2layer deposited on the SiO2/Si wafer minimized leakage through the insulating layer.
Moisture-Resistive Properties of SiNx Films Prepared by Catalytic Chemical Vapor Deposition below 100°C for Flexible Organic Light-Emitting Diode Displays
Authors: Heya Akira , Niki Toshikazu , Takano Masahiro , Yonezawa Yasuto , Minamikawa Toshiharu , Muroi Susumu , Minami Shigehira , Ikari Tokuo , Izumi Akira , Masuda Atsushi , Umemoto Hironobu , Matsumura Hideki
Published: July 2005

Silicon nitride (SiN
x
) films were deposited on Si and polycarbonate (PC) substrates at temperatures below 100°C by a catalytic chemical vapor deposition (Cat-CVD) method. By adding H2 to source gases, SiH4 and NH3, it was possible to prevent the deterioration of film qualities in low-temperature deposition processes. H atoms produced from H2 are effective for increasing the film densities and improving passivation properties. The water vapor transmission rate of SiN
x
films on PC substrates deposited at 80°C was lower than 0.3 g/m2day; the detection limit for a cup method. It is concluded that the Cat-CVD method with H2 dilution is a promising technique for preparing highly moisture-resistive SiN
x
films at low temperatures.
Crystallization and Structural Phase Transformation in Sub-100-nm-Thick SrBi2Ta2O9 Thin Film
Authors: Kohno Atsushi , Sakamoto Hideo , Matuo Kazuhiro
Published: July 2005

Crystal phase and structural properties in sub-100-nm-thick SrBi2Ta2O9 (SBT) thin films deposited on silicon substrates have been quantitatively investigated by X-ray diffraction (XRD) and X-ray reflection (XRR) analyses. The simulation fitting of XRR showed that the density and the surface roughness of the SBT film increased and saturated as the annealing temperature increased, indicating the phase transformation from fluorite to Aurivillius and the grain growth were enhanced by the high-temperature annealing. The SBT film was composed of small crystals of fluorite-type and Bi-layered Aurivillius phase after crystallization at temperatures of 730–785°C for 1 h. When annealing temperature was higher than 800°C, the film crystallized into a single phase of Bi-layered Aurivillius. It was also shown that the average crystal size in the SBT film increased with annealing temperature and saturated to be ∼75 nm at annealing temperatures higher than 800°C. The annealing temperature dependence of the integrated intensity of the diffraction suggested that the activation energy of the crystallization into the Aurivillius phase was significantly changed at ∼800°C. The change in the activation energy had a close relationship with the structural phase transformation of fluorite to Aurivillius and the grain growth.
Estimation of Feasibility for 100 Mbps High Data-Transfer Rate on an Optical Disk with High Areal Density Using Multilevel Recording
Authors: Nishida Tetsuya , Shintani Toshimichi , Maeda Takeshi
Published: July 2005

We developed a method and a new read-out tester to estimate the feasibility of achieving a high data-transfer rate in the case of multilevel recording. We introduced a second harmonic generation (SHG) laser as a light source and a developed preamplifier having the characteristics of low noise and a wide bandwidth into the tester. We also demonstrated the feasibility of 100 Mbps data transfer using a read only memory (ROM) disk with areal densities corresponding to 40 Gbit/in2 and 100 Gbit/in2 using single-carrier independent pit-edge recording/two-dimensional partial response maximum likelihood (SCIPER/2DPRML) format.
Transition of Roughness Evolution in Cu–In Alloy Films by the Formation of Intermetallic Compounds
Authors: Nakano Takeo , Mizuhashi Hiroshi , Baba Shigeru
Published: July 2005

The evolution of the surface morphology of Cu–In alloy film has been studied using an atomic force microscope. Samples of Cu–In were prepared by sequential vacuum deposition: copper was deposited to 10–40 nm thick first on a glass substrate, followed by the deposition of various amounts of indium to make the indium composition in the range of 0–75 at.%. Samples were prepared under three different conditions: A) deposited at room temperature (RT); B) deposited at RT and annealed at 120°C in vacuo; and C) deposited at 120°C. Samples formed by A and B (series A and B) showed a growth with a dynamical exponent β of ∼0.3 while the atomic ratio In/Cu was less than 2. The formation of CuIn2 intermetallic compound was observed by X-ray diffraction as the atomic ratio approached 2. After that, β suddenly increased to ∼0.7, which was attributed to the segregation of excess indium atoms to form cap-shaped islands. For samples grown by C (series C), the roughness initially increased more rapidly with β∼0.7 and decreased above In/Cu∼1. It showed a minimum at In/Cu=2 and finally increased again with β∼0.7 by forming indium islands, as in series A and B.
New Electrodeposition Technique for Controlling Depth Profile of CuInSe2 Thin Films for Solar Cell Application
Authors: Nakamura Sigeyuki
Published: July 2005

It is known that the efficiency of CuInSe2 (CIS)-based solar cells can be improved using a CIS layer with a composition that can be modulated to be In-rich near the pn junction interface. In this work, a new electrodeposition technique for preparing CIS thin films with a controlled composition depth profile was developed. CIS thin films having a bilayer structure, that is, with the Cu-rich and In-rich layers, were successfully deposited from one electrolyte only by changing the substrate potential during electrodeposition.
Oxidation and Morphology Change of Ru Films Caused by Sputter Deposition of Ta2O5 Films
Authors: Abe Yoshio , Kawamura Midori , Sasaki Katsutaka
Published: July 2005

Ta2O5 films were sputter deposited on Ru films and Ta2O5/Ru double layers were prepared as a model capacitor. The effects of Ta2O5 deposition temperature on oxidation of the Ru films and surface morphology of the double layers were examined. The surface roughness of the double layers increased with increasing deposition temperature of the Ta2O5 films. 1) Crystallization of Ta2O5 films, 2) crystal grain growth of Ru films, and 3) formation of RuO2 due to the oxidation of Ru were found to be the reasons for surface roughening.
Improvement of Deposition Rate by Sandblasting of Tungsten Wire in Catalytic Chemical Vapor Deposition
Authors: Heya Akira , Niki Toshikazu , Takano Masahiro , Doguchi Yoshiteru , Yonezawa Yasuto , Minamikawa Toshiharu , Muroi Susumu , Minami Shigehira , Izumi Akira , Masuda Atsushi , Umemoto Hironobu , Matsumura Hideki
Published: July 2005

The effects of sandblasting of tungsten wires were investigated to increase the deposition rate in catalytic chemical vapor deposition (Cat-CVD). The tungsten wires were sandblasted using silicon carbide powder. Both the surface area and surface roughness increased by this treatment. The deposition rate increased with the surface roughness when the input electric power was kept constant.
Long Line-Shaped Microwave Plasma Generation Employing a Narrow Rectangular Waveguide
Authors: Fukasawa Takayuki , Fujii Syuitsu , Shindo Haruo
Published: July 2005

Long line-shaped microwave plasma is generated employing a narrow rectangular waveguide. The wavelength of a microwave in a waveguide increases in accordance with the narrowing of the width of the waveguide. A narrow and flat rectangular waveguide is produced with internal dimensions of 500 mm length, 62 mm width and 5 mm height. The waveguide is connected to a TE10 mode rectangular waveguide (WST-AD standard). Two types of line-shaped plasmas are generated; one being a cavity type and the other a slit type. The cavity type line-shaped plasma has a quartz tube in the waveguide as a discharge tube and helium gas is supplied into the quartz tube through orifices of the waveguide. The slit type line-shaped plasma has a slit on its side. A quartz tube as a discharge tube is set beside the slit and helium gas is supplied into it. Electric field intensity and optical emission intensity are then measured. Uniform line-shaped plasmas are generated by varying the width of the waveguide and the microwave power in both types of line-shaped plasmas.
Particle-In-Cell Monte-Carlo Simulation of Capacitive RF Discharges: Comparison with Experimental Data
Authors: Kim Hyun Chul , Manuilenko Oleg , Lee Jae Koo
Published: July 2005

Particle-in-cell (PIC) simulations with Monte Carlo collision (MCC) are performed in argon capacitive rf discharges for the comparison with experimental data. The electron density and electron temperature along with the electron energy probability function are calculated for various gas pressures. It is shown that the sufficient number of simulation particles is one of the critical conditions for the reliability of PIC-MCC simulation. From the simulation with a large number of superparticles, a good agreement with experimental data measured by Godyak et al. [Phys. Rev. Lett. 65 (1990) 996] is obtained.
Experimental Study of Secondary Streamer Energy in Pulsed Corona Discharge
Authors: Bingyan Dong , Jie Li , Yan Wu , Guofeng Li
Published: July 2005

Secondary streamer discharge in a wire-plate pulsed streamer corona reactor can decrease the energy utilization efficiency of DeSO2. The influences of wire-to-wire spacing, wire-to-plate spacing, pulse-forming capacitance and discharge voltage on secondary streamer energy have been studied in air at atmospheric pressure. Increasing wire-to-plate spacing and decreasing pulse-forming capacitance and discharge voltage can decrease secondary streamer energy. Under the optimal wire-to-wire spacing which is 0.8–1.2 times the wire-to-plate spacing, the secondary streamer energy decreases.
High-Sensitivity Detection of Methane Near 6106 cm-1 Using Tunable External-Cavity Diode Laser
Authors: Ma Weiguang , Yin Wangbao , Dong Lei , Wang Lirong , Li Changyong , Jia Suotang
Published: July 2005

An external-cavity diode laser (ECDL) was employed to acquire spectrally resolved absorption profiles of methane lines in the R (9) manifold of the 2ν3 band near 6106 cm-1. The profiles were applied to high sensitivity detection of methane by low-frequency wavelength modulation spectroscopy (WMS) and harmonic detection (HD). In this study, the absorption profile near 6105.625 cm-1 is adopted. By measuring variations of signal amplitude at low concentrations of gas and background noise with frequency modulation amplitude (FMA), a group of optimum FMAs was obtained for 2f, 4f and 6f harmonic signals. Under these optimum conditions, minimum detectable absorbences (MDAs) of 4.7×10-4, 1.6×10-4 and 6.5×10-5, respectively, were realized; however 1.4×10-3 was obtained for direct absorption (DA).
Temperature Dependence of Photoluminescence Lifetime and Quantum Efficiency in Neat fac-Ir(ppy)3 Thin Films
Authors: Kobayashi Takashi , Ide Noritaka , Matsusue Noriyuki , Naito Hiroyoshi
Published: July 2005

Temperature dependences of lifetime and intensity of photoluminescence have been investigated in neat fac-Ir(ppy)3 thin films, which have a nonradiative decay channel due to aggregate quenching. Both temperature dependences can be well understood by a model which consists of three substates of the triplet metal-to-ligand-charge-transfer (3MLCT) state and a nonemissive state. Good agreement between the experimental results and the calculations based on the model suggests that nonradiative decay occurs through a higher lying excited state in fac-Ir(ppy)3 molecules, and that the nonemissive excited state has a decay rate of 3.1×109 s-1 and is located at 0.12 eV above the lowest substate of the 3MLCT state.
Read/Write Mechanism for a Scattered Type Super-Resolution Near-Field Structure Using an AgOx Mask Layer and the Smallest Mark Reproduced
Authors: Ukita Hiroo , Ueda Yasushi , Sasaki Mai
Published: July 2005

A working mechanism for a scattered type super-resolution near-field structure (super-RENS) disk using a silver oxide (AgO
x
) mask layer has been studied experimentally. The AgO
x
mask layer has five possible states depending on the laser power: AgO
x
(as-depo), uniformly dispersed Ag particles (after the initialization of 3.5 mW), Ag cluster (4–5 mW), Ag diffusion (5.5–7.5 mW), and a Ag ring structure (greater than 8 mW) for an objective lens numerical aperture of 0.5, a laser wavelength of 826 nm and a medium velocity of 2 m/s. On the other hand, the GeSbTe recording layer has the following possible states: crystal, halfway amorphous, completely amorphous, and gas bubble associated with Ag particles. For super-resolution read power (4 mW), the mask layer will have a Ag ring structure that increases both the signal carrier to noise ratio and the resolution limit. We improve the resolution limit of 413 nm to 50 nm at the duty ratio of 10% for the write optical pulse.
Side Chain Length Dependence of Optical Properties of Polyanions Based on Poly( p-phenylenevinylene) and Their Self-Assembled Multilayer Structures
Authors: Nishimura Tetsuharu , Yoshida Yuichi , Fujii Akihiko , Ozaki Masanori , Yoshino Katsumi
Published: July 2005

Polyanions based on carboxy-substituted poly( p-phenylenevinylene)s (PPVs) with various side chain lengths have been synthesized, and their optical properties investigated. Alternating periodic multilayer structures consisting of PPV and PPV polyanions have been fabricated by a self-assembly method on quartz or indium–tin–oxide-coated glass substrates. The dependence of the optical properties on the side chain length of carboxylic substituents or alkoxy substituents has been discussed.