bluuebunny/crossref_metadata_2025 huggingface dataset:
Piezoelectric Windmill: A Novel Solution to Remote Sensing
Authors: Priya Shashank , Chen Chih-Ta , Fye Darren , Zahnd Jeff
Published: July 2005

This study demonstrates a technology, “Piezoelectric Windmill”, for generating the electrical power from wind energy. The electric power-generation from wind energy is based on piezoelectric effect and utilizes the bimorph actuators. Piezoelectric Windmill consists of piezoelectric actuators arranged along the circumference of the mill in the cantilever form. Using the camshaft gear mechanism an oscillating torque is generated through the flowing wind and applied on the actuators. A working prototype was fabricated utilizing 12 bimorphs (60 ×20 ×0.5 mm3) having a preload of 23.5 gm. Under a nominal torque level corresponding to normal wind flow and oscillating frequency of 6 Hz, a power of 10.2 mW was successfully measured across a load of 4.6 kΩ after rectification. Combined with the wireless transmission, this technology provides a practical solution to the remote powering of sensors and communication devices.
Application of Plasma Jet Crystallization Technique to Fabrication of Thin-Film Transistor
Authors: Higashi Seiichiro , Kaku Hirotaka , Murakami Hideki , Miyazaki Seiichi , Watakabe Hajime , Ando Nobuyuki , Sameshima Toshiyuki
Published: July 2005

The crystallization of a-Si films on glass substrates using the plasma jet crystallization (PJC) technique and its application to thin-film transistor fabrication were studied. Amorphous Si (a-Si) films deposited by plasma-enhanced chemical vapor deposition (PECVD) of 50% SiH4 diluted with H2 were crystallized by thermal plasma jet under the power of 1.6 to 2.6 kW input to the plasma source and the substrate scan speed of 170 to 1000 mm/s. The crystallinity of the films was improved by treating the films at a higher input power for a longer duration. Thin-film transistors (TFTs) fabricated using the crystallized films showed good electrical characteristics. By increasing the input power from 1.86 to 2.29 kW in the crystallization, the average field-effect mobility was increased from 42 to 61 cm2·V-1·s-1, and the threshold voltage was decreased from 4.0 to 3.4 V. These results indicate that the PJC technique is a very promising low-temperature process technology.
Anisotropy and Lorentz-Force Dependences of Critical Current Density in C-Axis-Oriented YBa2Cu3O7-δ Thin Film
Authors: Horide Tomoya , Matsumoto Kaname , Yoshida Yutaka , Mukaida Masashi , Ichinose Ataru , Horii Shigeru , Osamura Kozo
Published: July 2005

The magnetic field angular dependence of J
c(θ) for a c-axis-oriented YBa2Cu3O7-δ (YBCO) thin film was measured using both constant and variable Lorentz force configurations. When the field was tilted from the c-axis within ±30°, J
c(θ) was independent of the intensity of the Lorentz force. This demonstrates that the vortices have bent segments trapped by pinning centers that extend parallel to the c-axis, and J
c(θ) is limited by the depinning of these segments. The effect on J
c(θ) of the two types of pinning centers, i.e., either parallel to the c-axis or to the a
b plane, should be considered when the field is tilted from the a
b plane within ±30°.
Magnetic and Magnetooptical Properties of Co-Al Alloy Thin Films on a Nanostructured Substrate
Authors: Nakatani Morio , Suzuki Yoshihisa , Sumi Satoshi , Tanemura Sakae
Published: July 2005

We investigated magnetic and magnetooptical properties of Co-Al magnetic thin films on a nanostructured substrate. The nanostructured substrate was made of polycarbonate by injection molding. The stamper was made by electron beam cutting. The nanostructured substrate contributed a perpendicular magnetic anisotropy component to the film and decreased the reflectance of the film. The Kerr rotation angle on the nanostructured substrate was greater than that on a glass substrate.
High-Reflectance-Resolution Optical Reflectometry with Synthesis of Optical Coherence Function
Authors: He Zuyuan , Yoshiyama Soshi , Enyama Momoyo , Hotate Kazuo
Published: July 2005

A novel high-reflectance-resolution optical reflectometry technique with the synthesis of the optical coherence function for the diagnosis of fiber optic assembly modules is proposed. In this new scheme, the optical frequency of a light source is modulated doubly: one in a sinusoidal wave to synthesize the coherence function into a peak at an arbitrary position within the region under test for a distributed reflection/scattering measurement and the other in a linear sweep to perform the wavelength domain averaging optically for a high reflectance resolution. This approach is free from the numerical averaging required in conventional methods. A simulation shows that the reflectance resolution can be enhanced to the 0.1 dB level. An experimental demonstration is also presented.
Fabrication of Layer-by-Layer Self-Assembly Films Using Roll-to-Roll Process
Authors: Fujimoto Kouji , Fujita Shiro , Ding Bin , Shiratori Seimei
Published: July 2005

In this research, we fabricated thin films deposited on poly(ethylene terephthalate) (PET) films by a layer-by-layer self-assembly method using a roll-to-roll process and measured the morphology and transmittance of the thin films using atomic force microscopy (AFM) (nanoscope IIIa, Digital Instruments) and UV-vis spectroscopy (Filmetrics, Inc). The thin films consisting of poly(allylamine hydrochloride), (PAH) adjusted to pH 7.5 and poly(acrylic acid) (PAA) adjusted to pH 3.5 showed a textured structure on moving film substrates. From these results, we found that polyelectrolyte multilayer (PEM) thin films showing similar to those structures of the films fabricated using a conventional dipping process were successfully assembled via the roll-to-roll process. We consider that this roll-to-roll process is suitable for fabricating large-area thin films.
Selective Removal of Carbon Nanotubes Utilizing Low-Acceleration-Voltage Electron Irradiation Damage
Authors: Suzuki Satoru , Takagi Daisuke , Homma Yoshikazu , Kobayashi Yoshihiro
Published: July 2005

A simple method for spatially selective removal of single-walled carbon nanotubes is demonstrated. This method is based on low-acceleration-voltage electron irradiation damage and consists of local electron irradiation of nanotubes and annealing in air. The irradiation damage seems to follow excitation of valence electrons.
Blue, Green and White InGaN Light-Emitting Diodes Grown on Si
Authors: Shih Chaun-Feng , Chen Nie-Chuan , Chang Chin-An , Liu Kuo-Shung
Published: July 2005

High-brightness InGaN light-emitting diodes (LEDs) have been grown on Si substrates by metal-organic vapor phase epitaxy. Both blue and green LEDs with an output power exceeding 0.7 mW and a lifetime exceeding 500 h were achieved. Two factors were analyzed: the difference between identical LED structures grown on Si and sapphire substrates, and the effect of cracking on the performance of LEDs grown on Si. Using a Si substrate, the LED emission showed a shift toward longer wavelength compared with that from a LED grown on sapphire. The presence of cracking, unless serious, showed little effect on the brightness and performance of the LEDs grown on Si. The mechanisms involved are discussed.
Real-Time Observation of Fractional-Order X-ray Reflection Profiles of InP(001) During Step-Flow Growth
Authors: Fujikawa Seiji , Kawamura Tomoaki , Bhunia Satyaban , Watanabe Yoshio , Tokushima Kenshi , Tsusaka Yoshiyuki , Kagoshima Yasushi , Matsui Junji
Published: July 2005

Fractional-order X-ray reflection profiles of (2×1)-InP(001) have been observed for the first time during step-flow growth of metalorganic chemical vapor deposition. Changes of the profiles have revealed that the coverage of (2 ×1) structures during the growth depends on the flow rates of indium and phosphorus sources. After stopping the growth, a slow recovery of peak intensity was observed with a time constant of lager than 1 min which corresponds to the residence time of indium atoms on the surface.
Self-Aligned Planar Double-Gate Field-Effect Transistors Fabricated by a Source/Drain First Process
Authors: Sakamoto Kunihiro , Huda Md. Quamrul , Ishii Kenichi
Published: July 2005

We introduce a new self-aligned process for fabricating planar double-gate metal-oxide-semiconductor field-effect transistors (MOSFETs). The source/drain area is defined first by opening a trench in a silicon-on-insulator layer. In the trench, a bottom gate, a silicon channel and a top gate are stacked up by selective epitaxy, lateral solid-phase epitaxy and a damascene process, respectively. We demonstrate MOSFET operations controlled by a tied double gate and those by independently biased top and bottom gates.
High-Quality GaSb/AlGaSb Quantum Well Grown on Si Substrate
Authors: Akahane Kouichi , Yamamoto Naokatsu , Gozu Shin-ichiro , Ohtani Naoki
Published: July 2005

We fabricate a GaSb/AlGaSb multi-quantum well (MQW) on a Si substrate. A high-quality GaSb/AlGaSb MQW sample can be grown on a Si substrate using an AlSb initiation layer. We can obtain a strong emission of 1.55 µm at room temperature from the sample, which has an 8 nm well width. Furthermore, we can control the emission wavelength by simply changing well width. The emission energy shows a good agreement with the theoretical curve. This indicates that the controllability of this material system is very high even when grown on a Si substrate.
Optimized Coalescence Method for the Metalorganic Chemical Vapor Deposition (MOCVD) Growth of High Quality Al-Polarity AlN Films on Sapphire
Authors: Paduano Qing , Weyburne David
Published: July 2005

Epitaxial Al-polarity AlN films were deposited on (0001) sapphire using a metalorganic chemical vapor deposition process involving a modulated ammonia/trimethyl aluminum flow, a pressure reduction from 150 Torr to 40 Torr after the first stage of growth, and growing the first ∼0.1 µm of AlN at a moderate V/III ratio, followed by a switch to low V/III for the remainder of the growth. Smooth, flat epitaxial films with a full width half maximum of the X-ray rocking curves as low as 177 arcseconds/650 arcseconds for the (0002)/(1012) reflections were obtained.
Synthesis of Tunable Long-Period Fiber Gratings with Inverted Erbium-Doped Fiber Amplifier Spectrum Using Thermal Change Parameters
Authors: Bae Jinho , Kim Kyungsup
Published: July 2005

We propose a new method for synthesizing piecewise-uniform long-period fiber gratings (LPFGs) using thermal change parameters. Previously proposed methods that employ the optimization algorithm based on an extended fundamental matrix model are used to design the equalizer that compensates for the nonflat gain characteristics of erbium-doped fiber amplifiers (EDFAs). We have obtained the design parameters for the thermal changes of the piecewise-uniform LPFGs that fit the inverted gain spectrum of an EDFA over the entire 1524.1 nm–1559.6 nm wavelength range. We have observed that the spectrum obtained by the proposed synthesis method is close to the spectrum measured in the wavelength band of interest.
Film-like Liquid Crystal Displays
Authors: Jeng Shie-Chang , Hsin Lung-Pin , Sha Yi-An , Ding Jau-Min , Wang Hsing-Lung , Hung Yu-Chu , Liao Chi-Chang
Published: July 2005

A novel method of fabricating a film-like liquid crystal display directly on a temporary supporting glass plate is presented. This approach is based on coating a UV-curable adhesive on a glass plate to form a flexible substrate, and a printable polymer-added liquid crystal is then applied on the substrate. By this approach, a flexible liquid crystal display can be fabricated by a cost-efficient coating technique, and it can be scaled up to any size.
Multi-Spectral Two-Photon Excited Fluorescence Microscopy Using Supercontinuum Light Source
Authors: Isobe Keisuke , Watanabe Wataru , Matsunaga Sachihiro , Higashi Tsunehito , Fukui Kiichi , Itoh Kazuyoshi
Published: July 2005

We report on a novel technique of multi-spectral two-photon-excited fluorescence microscopy by use of broadband supercontinuum light. A supercontinuum in the near-infrared region is generated in a 4.5-mm-long photonic crystal fiber using a Ti:sapphire femtosecond oscillator. The supercontinuum is used as a multi-spectral excitation light source in a two-photon excited fluorescence microscope. We demonstrate that three-color fluorescence images of organelles in a cell can be simultaneously acquired.
Demonstration of Nonpolar m-Plane InGaN/GaN Light-Emitting Diodes on Free-Standing m-Plane GaN Substrates
Authors: Chakraborty Arpan , Haskell Benjamin A. , Keller Stacia , Speck James S. , Denbaars Steven P. , Nakamura Shuji , Mishra Umesh K.
Published: July 2005

We report the fabrication of nonpolar m-plane InGaN/GaN multiple-quantum well light-emitting diodes (LEDs) on free-standing m-plane GaN substrates. On-wafer continuous wave output power of 240 µW was measured at 20 mA for a 300×300 µm2 device, and output power as high as 2.95 mW was measured at 300 mA. There was no sign of saturation of the output power at high drive currents. An emission peak at 450 nm was obtained on electroluminescence measurements with high drive currents. The current-voltage characteristics of these LEDs showed rectifying behavior with a turn-on voltage of 3–4 V.
A Study on the Performances of White Organic Light-Emitting Diodes and the Morphologies of Their Hole-Blocking Layers
Authors: Han Shiliang , Wang Liduo , Lei Gangtie , Qiu Yong
Published: July 2005

White organic light-emitting diodes (WOLEDs) with improved stability and efficiency based on an aluminum (III)bis(2-methyl-8-quinolinato)4-phenylphenolate (BAlq)-doped 4,7-diphenyl-1,10-phenanthroline (BPhen) hole-blocking layer (HBL) have been fabricated. Compared with the WOLEDs with BPhen hole-blocking layer, approximately 2.6 times the lifetime and 1.4 times the efficiency have been achieved in the WOLEDs adopting the 10 wt% BAlq-doped BPhen layer. Atomic force microscope (AFM) has been used to study the morphologies of BPhen, BAlq and BAlq-doped BPhen layers, which shows that the dopant of BAlq improves the stability of BPhen layer significantly. It is suggested that the improved performance of the WOLEDs is attributed to the stable hole-blocking layer in morphology.
Fractal Roughness of Polymers after Lithographic Processing
Authors: Constantoudis Vassilios , Gogolides Evangelos , Patsis George P. , Sarris Vassilios , Tserepi Angeliki , Diakoumakos Constantinos , Valamontes Evangelos S.
Published: July 2005

The morphology of photoresist polymer surfaces fabricated by lithographic processes is shown to exhibit self-affine behavior for a specific range of scales. The roughness parameters appropriate for the characterization of self-affine surfaces (surface width w, correlation length ξ and roughness exponent α) are found to depend on the exposure dose (i.e. the solubility) involved in the lithography process and to be correlated. A similar dependence and correlation is extracted from a Monte-Carlo simulation of polymer dissolution, thus indicating the pronounced contribution of the dissolution process to the formation of lithographic roughness. The self-affinity and the correlated behavior of the roughness parameters is a general phenomenon for dissolving polymers of varying solubility and not limited to the lithographic process.
35-Channel Multiwavelength Brillouin-Erbium Fiber Laser Utilizing Fiber Loop Mirrors
Authors: Al-Mansoori Mohammed Hayder , Abidin Mohd Shahnan Zainal , Naji Ahmed Wathik , Kadir Muhammad Zamzuri Abdul , Adikan Faisal Rafiq Mahamd , Mahdi Mohd Adzir
Published: July 2005

In this paper, we propose a simple approach for achieving multiwavelength tunable Brillouin-Erbium fiber lasers utilizing fiber loop mirror technique. The impact of Brillouin gain contributed by the change of single-mode fiber length on the number of channels is explained. A low threshold operation of 3.5, 4 and 8 mW is achieved at 25, 8.8 and 1.9 km respectively. Simultaneous oscillation of 20, 21 and 35 channels with equally channel spacing of 0.088 nm is obtained at the optimum Brillouin pump power and Brillouin pump wavelength for 1.9, 8.8 and 25 km respectively.
Direct Formation of Arrays of Prolate Ag Nanoparticles by Dynamic Oblique Deposition
Authors: Suzuki Motofumi , Maekita Wataru , Kishimoto Kazuaki , Teramura Satoshi , Nakajima Kaoru , Kimura Kenji , Taga Yasunori
Published: July 2005

We have demonstrated the direct formation of prolate Ag nanoparticles with a quasi parallel major axis on a template layer of SiO2 having a strongly anisotropic surface morphology. The peculiar nanomorphology of the nanoparticles and template is physically self-organized owing to self-shadowing during oblique vacuum deposition. The resulting films exhibit anisotropic optical absorption due to the plasma resonance that is sensitive to the shape of the nanoparticles. Since our method can be applied to any combination of thin-film materials, it is useful for enabling plasmon-mediated optical phenomena and applying them to the development of various photonic devices such as thin-film polarizers.
Radiation from Tightly Focused Highly Intense Laser Pulse Interaction with Weakly Magnetized Plasma
Authors: Parchamy Homaira , Yugami Noboru , Muraki Takuya , Noda Hajime , Nishida Yasushi
Published: July 2005

From a tightly focused highly intense ultrashort laser pulse interaction with a weakly magnetized plasma, radiations in the microwave frequency range have been observed. To investigate the microwave radiation produced by the laser-plasma interaction, a mode-locked Ti:Sapphire laser beam with a wavelength of 800 nm, a pulse width of 100 fs [full width at half maximum (FWHM)], a maximum energy of 100 mJ per pulse, and a repetition rate of 10 Hz has been employed. Radiation emission characteristics could be explained by the electron motion along the applied magnetic field, where electrons are affected by the electric field created by an ion column. Calculated data of the electron motion are in good agreement with experimental data.
Subwavelength-Resolution Raman Microscopy of Si Structures Using Metal-Particle-Topped AFM Probe
Authors: Poborchii Vladimir , Tada Tetsuya , Kanayama Toshihiko
Published: July 2005

Using depolarization of the 364 nm light scattered by a small particle on the (100)Si surface, one can obtain allowed 520 cm-1 Raman signal from the localized area of Si around the particle, while the ordinary Raman signal is forbidden by the polarization selection rules. We have realized this scheme using Ag-particle-topped quartz atomic force microscope (AFM) probe immersed into glycerol droplet on Si surface and applied to local stress measurement. Lateral resolution in the range of 100 nm was demonstrated, and stress variation in a strained Si film was investigated.
Structural and Luminescence Characteristics of Post-Annealed ZnO Films on Si (111) in H2O Ambient
Authors: Lee Ju Young , Kim Hong Seung , Chang Ji Ho , Yang Min , Ahn Hyong Su , Ryu Sang Ouk
Published: July 2005

This letter reports the effects of post thermal annealing in H2O on the structural and optical properties of Zinc oxide (ZnO) films deposited on Si substrate. The properties were investigated by atomic force microscopy (AFM), X-ray diffraction (XRD), transmission electron microscopy (TEM) and photoluminescence (PL) measurements. Our experiments demonstrated that ZnO films have better crystal quality at high annealing temperatures and there are no emission peaks even at the visible region of ZnO films annealed at 900°C. After annealing at 900°C, however, the surface roughness was increased, which seems to have been caused by re-evaporation, and the thick SiO2 and Zn-Si-O mixed layer was formed between the ZnO film and the Si substrate.
A Study on the Crystallization Behavior of Nitrogen Doped Ge2Sb2Te5 Thin Film
Authors: Kim Suk Min , Jun Jin Hyung , Choi Doo Jin , Hong Suk Kyoung , Park Young Jin
Published: July 2005

We investigated the crystallization behaviors of nitrogen doped Ge2Sb2Te5 thin films deposited in various nitrogen gas flow rates by means of the 4-point probe technique, X-ray diffraction and transmission electron microscopy (TEM), and we mapped the change of crystallization behavior on annealing temperatures. Nitrogen doping resulted in an increase of crystallization temperature from amorphous to fcc structure and maintained the fcc structure up to a higher annealing temperature than un-doped film did. However, crystallization behavior in heavily nitrogen-doped film occurred from an amorphous directly to a hexagonal state, skipping the fcc crystallization step.
Doping Concentration and Structural Dependences of the Thermal Stability of the 2DEG in GaN-Based High-Electron-Mobility Transistor Structures
Authors: Feng Zhihong , Zhou Yugang , Cai Shujun , Lau Kei-May
Published: July 2005

The dependences of the stability of the two-dimensional electron gas (2DEG) on the doping concentration and the heterostructure in GaN-based high-electron-mobility transistors were investigated, in an annealing experiment at 500°C under N2 ambient. Both the 2DEG density and mobility decreased after annealing due to the strain relaxation in an AlGaN layer. Moreover, a decrease in 2DEG conductivity was found in samples with different doping concentrations in a Si-doped AlGaN layer. A significant decrease in 2DEG conductivity occurred in a sample with a thicker AlGaN layer due to a larger strain relaxation. We found that a GaN cap layer could enhance the stability of the 2DEG up to 75 h of aging. Relaxation suppression by the GaN cap inducing dislocation pinning is proposed to interpret this effect.
1.2 µm Band GaInAs/GaAs High-Density Multiple-Wavelength Vertical Cavity Surface Emitting Laser Array
Authors: Uchiyama Yasuhiro , Kondo Takashi , Takeda Kazutaka , Matsutani Akihiro , Uchida Takeshi , Miyamoto Tomoyuki , Koyama Fumio
Published: July 2005

We demonstrate a densely packed multi-wavelength GaInAs/GaAs vertical cavity surface emitting laser array emitting in 1200 nm wavelength band. 110-channel emitters could be integrated in a 2.2 mm long bar with spatial spacing of 20 µm and wavelength spacing of 0.1 nm. All the emitters exhibit single mode operation with output power of over 1 mW. The wavelength separation is precisely controlled by adjusting the bias current of each element.
Hillock-Free Homoepitaxial Diamond (100) Films Grown at High Methane Concentrations
Authors: Hamada Mitsuhiro , Teraji Tokuyuki , Ito Toshimichi
Published: July 2005

Improved growth processes for homoepitaxial diamond films with high quality and flat surfaces have been presented. Growth hillocks leading to rough surfaces were almost perfectly suppressed under the new growth processes, where the substrate temperature was set to a particular region. The high quality in electronic states was evidenced by the fact that the homoepitaxial films with thicknesses up to 11 µm gave intense free-exciton recombination emissions in room-temperature cathodoluminescence spectra. It is concluded that lobe-shape marks appearing on the surface after an apparent lateral diamond growth came from defects left on the substrate surface. The origin of the apparent lateral growth observed is discussed in relation to an enhanced speed of the step edge growth at the substrate temperature elevated to ∼1000°C.
Characterization of Thermally Annealed Fluorinated Silicon Dioxide Films Prepared by Liquid-Phase Deposition
Authors: Lee Ming-Kwei , Shih Chung-Min , Chang Shu-Ming , Wang Hong-Chi , Huang Jung-Jie
Published: July 2005

Fluorinated silicon dioxide films were prepared by liquid phase deposition method using hydrosilicofluoric acid and ammonium hydroxide aqua as sources. The quality of fluorinated silicon dioxide films can be improved by N2 thermal annealing. It is in an attempt to evaluate the feasibility of this material as a candidate for inter-metal dielectrics in ULSIs. The obtained results were the relative dielectric constant of 3.2, and the leakage current density measured at the electric field of 1.5 MV/cm about 1×10-7 A/cm2 at the annealing temperature of 350°C. It has potential for inter-metal dielectric applications.
Supercritical Improvement of Resist Patterns by Introducing Functional Molecules
Authors: Namatsu Hideo , Sato Mitsuru
Published: July 2005

A new performance enhancement technique for resists has been developed that involves the use of supercritical fluid and functional molecules. Because it is an excellent solvent, the supercritical fluid dissolves the molecules, which provide functions originally lacking in the resist material; and the good diffusivity of supercritical fluid distributes the molecules throughout the resist. Thus, functions can be added to a resist without degrading its sensitivity or development characteristics because the process is performed after exposure and development. Furthermore, since the molecules are dispersed uniformly, there is no change in the line width of resist patterns. This advanced technique for improving resists using supercritical fluid has great potential to change the current concept of resist processes.
Fabrication and Characterization of InN-Based Quantum Well Structures Grown by Radio-Frequency Plasma-Assisted Molecular-Beam Epitaxy
Authors: Kurouchi Masahito , Naoi Hiroyuki , Araki Tsutomu , Miyajima Takao , Nanishi Yasushi
Published: July 2005

InN/In
x
Ga1-x
N quantum well structures have been successfully fabricated on InN templates grown on (0 0 0 1) sapphire substrates by RF plasma assisted molecular beam epitaxy for the first time. The structure was confirmed by observing the 1st and 2nd satellite peaks of X-ray diffraction. From InN/In0.8Ga0.2N single quantum well structures with the different well widths of 2.3, 3.4 and 5.7 nm, photoluminescence (PL) emission from the well layers was observed at 77 K, and the PL peak energy slightly lowered with increasing well width. This dependence can be explained by combined effects of the quantum size effect, quantum confinement Stark effect, and band filling effect.
A Pd–Cu–Ni Ternary Alloyed Membrane on Porous Nickel Support Prepared by Sputtering and Copper Reflow
Authors: Kim Dong-Won , Um Ki-Youn , Kim Heung-Gu , Lee In-Seon , Kim Sang-Ho , Park Jong-Soo , Ryi Shin-Kun , Cho Sung-Ho
Published: July 2005

We propose a ternary, Pd–Cu–Ni, alloyed membrane on porous nickel support that dramatically enhances the hydrogen selectivity by using sputtering and copper reflow. Porous nickel support made by sintering shows strong resistance to hydrogen embrittlement and thermal fatigue. To improve the hydrogen selectivity of the membrane, fabricated the layer sequence of Cu/Pd/Ni on porous nickel support replaced that of conventional Pd/Cu/Ni and then reflow was performed at 700°C. Consequently, copper was reflowed unilaterally into Pd/Ni layer, thereby avoiding delamination by the interlayered copper and enabling infinite hydrogen selectivity because of extremely dense coatings.
Effect of Capacitance-Voltage Sweep on the Flat-Band Voltage of Metal-Oxide-Semiconductor Device with High-k Gate Dielectric
Authors: Yang Hyundoek , Son Yunik , Choi Hyejung , Choi Sangmoo , Hwang Hyunsang
Published: July 2005

The capacitance-voltage (C-V) characteristics with and without light illumination were evaluated for a capacitor with a Pt gate on the atomic-layer-deposited HfO2 dielectric. The flat-band voltage (V
fb) is conventionally determined by a C-V curve. However, the extracted values of V
fb were dependent on the C-V sweep direction and the starting voltage of the sweep (V
start). The increasing differences between V
start and intrinsic V
fb (V
fb,i) results in the increasing deviations of V
fb from V
fb,i. Therefore, the value of V
start should be close to V
fb,i and different values of V
start must be applied to the devices with significantly different V
fb,i.
Freestanding GaN Substrate by Advanced Facet-Controlled Epitaxial Lateral Overgrowth Technique with Masking Side Facets
Authors: Bohyama Shinya , Miyake Hideto , Hiramatsu Kazumasa , Tsuchida Yoshihiko , Maeda Takayoshi
Published: July 2005

We propose here an advanced facet-controlled epitaxial lateral overgrowth (FACELO) technique for obtaining a GaN layer with a low threading dislocation (TD) density. In the selective-area-growth (SAG) GaN with (11–22) facets, TDs from the underlying GaN are bent horizontally, i.e., toward the <11–20> or <1–100> direction. In the advanced FACELO technique, TDs are terminated by SiO2 masks on (11–22) facets. Except for coalescence regions, the TD density of the surface was less than 106 cm-2 for the GaN layer grown by MOVPE using the advanced FACELO technique. The side masks have an additional benefit of contributing to the void formation which facilitates the separation of the thick GaN films from the sapphire substrate.
Characteristics of Organic Light Emitting Diodes with Al-Doped ZnO Anode Deposited by Atomic Layer Deposition
Authors: Park Sang-Hee Ko , Lee Jeong-Ik , Hwang Chi-Sun , Chu Hye Yong
Published: July 2005

Transparent conductive, Al-doped ZnO films (ZnO:Al) have been deposited by means of an atomic layer deposition method with the surface chemical compositions of ZnO (film A) and Al2O3 (film B). The sheet resistance, surface work function, and structure characteristics of ZnO:Al films have been investigated. Organic light emitting diodes (OLEDs) were fabricated on glass substrates using two different ZnO:Al anodes. The devices fabricated with them exhibited higher current and luminance with higher external quantum efficiencies below approximately 5000 cd/m2, than those fabricated with a conventional tin-doped indium oxide (ITO) anode. The external quantum efficiencies of the devices with film A, film B, and ITO were 1.86, 1.97, and 1.74%, respectively.
Improved Height Measurement of Single CdSe Colloidal Quantum Dots by Contact-Mode Atomic Force Microscopy Using Carbon Nano-Tube Tips; for the Investigation of Current-Voltage Characteristics
Authors: Tanaka Ichiro , Kajimoto Kaori , Uno Kazuyuki , Ohtsuki Osamu , Murase Tomohide , Asami Harumi , Hara Masahiko , Kamiya Itaru
Published: July 2005

We have investigated the distribution of measured heights of single CdSe colloidal quantum dots (QDs) by contact-mode atomic force microscopy. The dot heights measured with metal-coated Si tips, with which large adhesive force is measured between the tip and sample, are much smaller than that expected from optical absorption. This discrepancy could be due to the dot position fluctuation that occurs when the tip is in contact with the dot because the height distribution of the QDs covered with very thin SiO2 layer is in agreement with the optical measurement. On the other hand, when conductive carbon nano-tube (CNT) tips are used, the adhesive force is reduced significantly, and the measured dot heights become close to the expected value. Thus, the measurement of QD height is greatly improved in accuracy with CNT tips. As a result, the current flowing through the QD can be measured, and conductance changes attributed to electron resonant tunneling through the QD are observed.
Field Emission Properties of the Nonaligned Multiwalled Carbon Nanotube Films with Different Length
Authors: Feng Wei , Araki Hisashi , Ozaki Masanori , Yoshino Katsumi
Published: July 2005

The field emission properties of the multi-walled carbon nanotubes (MWNT) with different length were studied. The results exhibit that the emission properties of these carbon nanotube films are intensively dependent on the length of carbon nanotubes and density of the film. The morphology of the different length MWNT films was investigated by scanning electron micrograph (SEM) and X-ray diffraction (XRD). Large differences of field emission characteristics among these MWNTs are observed, and explained in terms of a variation of the field enhancement factor. The longest MWNT exhibits the best field emission characteristics among all of the MWNTs studied. As a consequence, the field emission characteristics can be optimized by controlled the physical parameter of MWNT such as the tip density and the nanotube length, and the density of its film.
Crystallinity of NiO Nanowires Grown at Step Edges of Sapphire Substrate
Authors: Sasaki Atsushi , Akiba Shusaku , Matsuda Akifumi , Hara Wakana , Sato Shuhei , Yoshimoto Mamoru
Published: July 2005

NiO nanowires were formed along atomic step edges on the ultrasmooth sapphire (0001) substrates by laser molecular beam epitaxy. From atomic force microscopy, the nanowires were found to be ∼20 nm in width and ∼0.5 nm in height along the straight, 0.2 nm-high step edges of the substrate. The crystal structure of NiO nanowires was examined by in situ coaxial impact collision ion scattering spectroscopy (CAICISS). The CAICISS results on the azimuth dependences of Ni signal for the NiO nanowires as well as NiO (111) epitaxial thin films indicate that the NiO nanowires were epitaxially grown with (111) orientation under in-plane stress.
Arsenic Doping of n-Type β-FeSi2 Films by Sputtering Method
Authors: Liu Zhengxin , Osamura Masato , Ootsuka Teruhisa , Kuroda Ryo , Fukuzawa Yasuhiro , Mise Takahiro , Otogawa Naotaka , Nakayama Yasuhiko , Tanoue Hisao , Makita Yunosuke
Published: July 2005

High quality epitaxial n-type β-FeSi2 thin films prepared by alternate Fe/Si multilayer deposition were doped with arsenic as impurity by sputtering method. Doping sources were heavily arsenic-doped silicon chips placed on the surface of silicon target. The starting β-FeSi2 films before doping were typically n-type with a residual electron concentration of about 1.0 ×1017 cm-3 and a mobility of about 260 cm2/V·s. When arsenic concentration changed from 7.0 ×1017 to 1.9 ×1018 cm-3, net electron concentration increased from about 2.0 ×1017 to 4.0 ×1017 cm-3, and electron mobility decreased from 250 to 160 cm2/V·s. Secondary ion mass spectroscopy (SIMS) measurements showed a homogeneous arsenic distribution in β-FeSi2 films and a small diffused region (about 50 nm) at the interface between β-FeSi2 and a Si substrate. Arsenic-doped β-FeSi2 films exhibited epitaxial growth in the (110)/(101) orientation and a continuous structure without cracks. However, other crystalline orientations together with pinholes appeared when the arsenic doping concentration increased.
Growth of MnGeP2 Thin Films by Molecular Beam Epitaxy
Authors: Minami Kazuyuki , Jogo Jumpei , Smirnov Valery , Yuasa Hideki , Nagatsuka Toshikazu , Ishibashi Takayuki , Morishita Yoshitaka , Matsuo Yuriko , Kangawa Yoshihiro , Koukitu Akinori , Sato Katsuaki
Published: July 2005

Epitaxial growth of the Mn-containing novel ternary compound MnGeP2 has been investigated. Prior to the growth experiments, theoretical studies using an ab initio calculation were carried out, on the basis of which the stable existence of MnGeP2 with a chalcopyrite structure was predicted. Growth experiments of Mn-Ge-P were performed on GaAs(001) and InP(001) substrates using a molecular beam epitaxy (MBE) technique, in which Mn and Ge were supplied from solid sources and P from a tertiary butyl phosphine (TBP) gas source. The optimum growth condition has been estimated on the basis of X-ray diffraction studies. Oriented overgrowth of MnGeP2 was confirmed from a reciprocal lattice mapping (RLM) on X-ray diffraction (XRD) analyses, and lattice constants have been determined to be a=0.569 nm and c=1.13 nm based on the assumption that the material has a tetragonal crystal structure.
Lock-in Phenomena of Josephson Vortices under Vicinal Layer Parallel Magnetic Field
Authors: Hatano Takeshi , Kim Sunmi , Urayama Shinya , Wang Huabing , Inomata Kunihiro , Nagao Masanori , Yun Kyungsung , Kawae Takeshi , Takano Yoshihiko , Tachiki Masashi , Yamashita Tsutomu
Published: July 2005

The lock-in phenomena of Josephson vortices have been studied under the vicinal layer parallel magnetic field in a field cooling experiment. As a sign of the lock-in state, Josephson vortex-flow voltage was measured with c-axis bias current in an in-line type intrinsic Josephson junction formed on a single-crystal Bi2Sr2CaCu2O8+δ superconductor. On cooling, vortex-flow voltage appears at the lock-in transition of the vortices which takes place at the temperature T when the lower critical field H

c1(T) grows as high as the c-axis component of the magnetic field. This can be understood as the pancake vortices being expelled from the superconducting double CuO2 layers by the Meissner effect. The temperature dependence of H

c1(T) was observed by the lock-in transition at various offset angles.
Influence of Gas Pressure on 147 nm Emission Properties of Plasma Display Panel
Authors: Uhm Han S. , Choi Eun H. , Jung Kyu B.
Published: July 2005

The influence of gas pressure on the emission properties of vacuum ultraviolet light (VUV) with a wavelength of 147 nm is investigated for the electrical discharge in plasma display panel (PDP) cells. The emission properties are studied in terms of the xenon mole fraction in a neon-xenon mixture. It is shown using a theoretical model that the xenon mole fraction corresponding to the peak emission intensity decreases as the gas pressure p increases. Moreover, the emission intensity at a high xenon mole fraction decreases more significantly as the gas pressure increases. Experimental observations agree well with theoretical predictions.
1-kHz Real-Time Imaging Using a Half-Cycle Terahertz Electromagnetic Pulse
Authors: Rungsawang Rakchanok , Mochiduki Aya , Ookuma Shin-ichi , Hattori Toshiaki
Published: July 2005

Real-time high-speed terahertz (THz) two-dimensional imaging at a frame rate as high as 1 kHz was performed using intense half-cycle THz electromagnetic pulses. The THz source was a 3-cm-gap photoconductive antenna. The distribution of THz electric field was detected by a single optical probe pulse using a high-speed charge–coupled device camera by adopting a phase-sensitive electrooptic detection method. Using the system, we demonstrated imaging of a moving metal object by observing the transmitted beam. The time delay of optical pulses was fixed to probe the THz pulse at the time when the axial THz waveform has the steepest transient, which yields a good image quality. This research opens the window of high-speed imaging in the THz frequency regime.
Photoluminescence Properties from β-FeSi2 Film Epitaxially Grown on Si, YSZ and Si//YSZ
Authors: Akiyama Kensuke , Kaneko Satoru , Terai Yoshikazu , Maeda Yoshihito , Funakubo Hiroshi
Published: July 2005

We have succeeded in expitaxial growth of (101) and (110)-oriented β-FeSi2 films on (111)Si, (111)Si-buffered (111)YSZ and (111)YSZ substrates by metal organic chemical vapor deposition (MOCVD). All the films showed highly perfection in orientation irrespective of the substrate. After annealing at 900°C in Ar atmosphere, their photoluminescences (PL) around 1.54 µm were observed in the β-FeSi2 films grown on (111)Si and (111)Si-buffered (111)YSZ substrates, except for the film on (111)YSZ substrates. This suggests that the β-FeSi2/Si interface is a crucial structure for enhancement of PL and that the Si atom diffuses into β-FeSi2 is important factor to 1.54-µm PL.
Microscopic Study of Work Function of Ag-Deposited Pt(111) and Ag/Pt Surface Alloy
Authors: Miya Kenta , Sinsarp Asawin , Sasaki Masahiro , Yamamoto Shigehiko
Published: July 2005

The microscopic work function distributions of Ag-deposited Pt(111) surfaces and Ag/Pt surface alloy have been studied through local tunneling barrier height (LBH) imaging by means of scanning tunneling microscopy (STM). The difference in microscopic work function between Ag and Pt clusters in the Ag/Pt surface alloy is much smaller than that between Ag large islands and Pt terraces on a Ag-deposited Pt(111) surface although their Ag coverages as well as macroscopic work functions are the same. This features which occurrs when the dimensions of the clusters are a few nanometers is due to the long-range effect of work function reduction which is observed for the Cs-adsorption surfaces.
Tilted Homeotropic Alignment with High Reliability of Liquid Crystal Molecules Adsorbed on Anodic Porous Alumina in a Magnetic Field
Authors: Maeda Tsuyoshi , Hiroshima Kohki
Published: July 2005

Tilted homeotropic alignment with a good uniformity on an anodic porous alumina (Al2O3) film was realized with liquid crystal (LC) molecules adsorbed unidirectionally in a magnetic field. The LC pretilt angle can be controlled by the surface topology of the anodic porous alumina film and by the direction of the magnetic field at a virgin LC adsorbed on the film. This tilted LC alignment remains very stable even when subjected to external forces such as a heat cycle treatment or irradiation by a projection light source. An LC light valve with the porous alumina film is particularly promising for use in high-quality projection systems because of its high reliability and good uniform alignment.
Si Island Formation on Domain Boundaries Induced by Ar Ion Irradiation on High-Temperature Si(111)-7 ×7 Dimer-Adatom-Stacking Fault Surfaces
Authors: Uchigasaki Makoto , Tomiki Kenichi , Kamioka Takefumi , Nakayama Eiji , Watanabe Takanobu , Ohdomari Iwao
Published: July 2005

Using a low-energy ion gun/high-temperature scanning tunneling microscope combined system (IG/STM), we observed the atomic scale behavior of a Si surface kept at 500°C before, during and after Ar ion irradiation. We found that Si islands grew up within ion irradiation selectively along the boundaries of domains of 7 ×7 dimer-adatom-stacking (DAS) faults. The Si islands were 1 double atomic layer high and had the 7 ×7 DAS reconstruction. The area of the islands increased linearly with ion doses up to 2.5 ×1014 cm-2.
Pt/C-Electrocatalyst Painting on Polymer Electrolyte Membrane by Electrostatic Spray Deposition
Authors: Umeda Minoru , Kawaguchi Syunsuke , Yamada Akifumi , Uchida Isamu
Published: July 2005

An electrocatalyst painting technique for use in a limited surface area of a polymer electrolyte membrane has been developed by employing electrostatic spray deposition (ESD). ESD is a process in which an aerosol of a solution is ejected from a metal syringe nozzle with a high applied voltage under atmosphere to obtain a thin film on the counter electrode. First, a dispersion containing Pt-loading carbon (Pt/C) powder and Nafion solution was sprayed by using the ESD technique. As a result, the dispersion was deposited over the entire surface area of a polymer electrolyte membrane of Nafion that was placed on the counter Au electrode, whereas, the dispersion was neither deposited on an electric-insulating poly(ethylene telephthalete) (PET) nor on the Nafion membrane on the PET. For the experiment, the Nafion membrane was pretreated to give it ionic conductivity. Next, a dye solution containing Rhodamine B was sprayed in the same manner, with the same result. In the case where the sizes of Nafion membrane and Au electrode were the same, the deposition only occurred on the Nafion/Au layered structure. According to these results, the aerosol generated at the syringe nozzle is introduced to the conductive area and kept away from the insulating area. Finally, for the untreated Nafion membrane on which a water droplet was placed, ESD of the Pt/C dispersion was conducted. Consequently, an electrocatalyst layer was successfully formed only at the wetted point of the Nafion membrane. This technique enables the painting of an electrocatalyst layer over a limited area without the use of any surface mask.
Anneal-Induced Degradation of Amorphous Selenium Characterized by Photoconductivity Measurements
Authors: Saito Ichitaro , Oonuki Kousuke , Yamada Takatoshi , Aono Masami , Butler Tim , Rupesinghe Nalin L. , Amaratunga Gehan A. J. , Milne William I. , Okano Ken
Published: July 2005

Photoconductivity measurements of amorphous selenium (a-Se) and arsenic selenide (a-As2Se3) were carried out. Samples where annealed from 333–358 K at 5 K step for 5 minutes and the photoconductivity was measured after each annealing step. It was found that the dark current increases permanently for a-Se and the photoconductivity ratio increased drastically after 338 K, but drops after further annealing. Amorphous-As2Se3 however, has no noticeable change in the dark current neither in the photoconductivity ratio. Arsenic is introduced into a-Se to prevent degradation, which causes loss of image quality, but the volume must be controlled in order to maintain high photoconductivity.
Room-Temperature Operation of Current Switching Circuit Using Integrated Silicon Single-Hole Transistors
Authors: Saitoh Masumi , Harata Hidehiro , Hiramoto Toshiro
Published: July 2005

We report the first room-temperature (RT) circuit operation using two integrated silicon single-hole transistors. We have developed a controllable fabrication process for silicon single-hole transistors (SHTs) in the form of ultranarrow-wire-channel metal-oxide-semiconductor field-effect transistors (MOSFETs) whose channel is formed by reactive ion etching, wet etching, and slight thermal oxidation. Ultralarge Coulomb blockade (CB) oscillation with a peak-to-valley current ratio of over 103 (highest ever reported) is observed at RT in a fabricated SHT. A current switching circuit using two SHTs integrated under a single gate is successfully operated at RT. We also demonstrate the technique for controlling CB oscillation peaks by charge injection into silicon nanocrystal floating gates embedded in the gate oxide of SHTs at RT.
Influence of Oxygen Flow Ratio on Properties of Zn2SnO4 Thin Films Deposited by RF Magnetron Sputtering
Authors: Satoh Kazuo , Kakehi Yoshiharu , Okamoto Akio , Murakami Shuichi , Uratani Fumihiro , Yotsuya Tsutom
Published: July 2005

Zinc stannate (Zn2SnO4) thin films were deposited by RF magnetron sputtering on silica substrates at various [O2/(Ar+O2)] flow ratios. The influences of the [O2/(Ar+O2)] flow ratio on the crystalline structure, and the optical and electrical properties have been investigated. No sharp X-ray diffraction (XRD) peaks were observed in as-deposited thin films. After postdeposition annealing in air at 750°C, the thin films showed a preferred orientation of (111). The thin films exhibited a high transmittance in the visible spectrum irrespective of the [O2/(Ar+O2)] flow ratio or postdeposition annealing. The optical band gap was estimated to be 4.1 eV by analyzing the optical spectra of thin films annealed at 750°C. The composition ratio of Zn/Sn for thin films deposited in an Ar/O2 mixture was 2.0 and their electrical resistivity was on the order of 105 Ω·cm. In contrast, the composition ratio of Zn/Sn for a thin film deposited in pure Ar was 1.5 and an electrical resistivity of 4.1 ×10-2 Ω·cm was observed.
Formation of Hexagonal GaN Pyramids by Photo Assisted Electroless Chemical Etching
Authors: Fu Dejun , Park Young Shin , Panin Gennady N. , Kang Tae Won
Published: July 2005

Hexagonal GaN pyramids were formed by the photo enhanced chemical etching of GaN epilayers grown on sapphire by molecular-beam epitaxy. Defective areas of the epilayers were selectively etched in a mixed solution of KOH and K2S2O8 under ultraviolet illumination, producing submicron-size pyramids nonuniformly distributed on the substrate. The cathodoluminescence of the pyramids was redshifted compared with that of the sample before etching. Atomic force microscopy suggested the facets of the pyramids to be (1012) oriented. High-resolution X-ray diffraction showed that the width of the (105) plane of the etched sample is smaller than that of the unetched sample. A larger quantity of K2S2O8 added to the KOH solution led to a high etching rate and the etched sample exhibited a strong cathodoluminescence.