bluuebunny/crossref_metadata_2025 huggingface dataset:
Ultra-Small GaAs-Photonic-Crystal-Slab-Waveguide-Based Near-Infrared Components: Fabrication, Guided-Mode Identification, and Estimation of Low-Loss and Broad-Band-Width in Straight-Waveguides, 60°-Bends and Y-Splitters
Authors: Inoue Kuon , Sugimoto Yoshimasa , Ikeda Naoki , Tanaka Yu , Asakawa Kiyoshi , Maruyama Taishi , Miyashita Kazuya , Ishida Koji , Watanabe Yoshinori
Published: February 2005

We designed and fabricated ultra-small photonic-crystal (PC)-waveguide (WG)-based components of straight-WGs, 60°-bends and Y-splitters, utilizing single-line-defect in the air-bridge type GaAs PC, and revealed their optical properties in detail by observing a transmittance (T) spectrum over a broad wavelength-region from 850 to 1600 nm. For this purpose, we developed a halogen-lamp-based spectrometer for an ultra-thin slab-sample, which has turned out very useful. We also calculated the corresponding T-spectrum by using three-dimensional finite-difference-time-domain method. In all cases where comparison is possible, the observed spectrum agrees essentially with the calculated one. Owing to these broad spectra, we have unambiguously identified the high-T region due to single guided-mode in the respective components. Comparisons of the spectrum between different samples or components, such as the straight-WGs with much different lengths, or the straight-WG and the sharp bend have also helped to reasonably interpret the observed spectra, allowing a comprehensive understanding of optical properties of those components. The propagation loss and the band width in each component could also be estimated from the comparison. The loss is estimated as 1.5 ±0.5 dB/mm for the straight-WG, while less than 1 dB/bend, if it exists, for the bend WG, and both band-widths are broader than 40 nm. We also find that the Y-splitter is capable of dividing light into two ports almost equally in intensity with a total transmittance of more than 85%; the band-width is broader than 40 nm. As a result, we have found that all those should be useful as key components in future ultra-fast planar optical integrated circuits.
Resonant Frequency Control of a Microspherical Cavity by Temperature Adjustment
Authors: Chiba Akito , Fujiwara Hideki , Hotta Jun-ichi , Takeuchi Shigeki , Sasaki Keiji
Published: February 2005

We demonstrate frequency tuning of whispering-gallery mode resonances in a fused-silica microsphere by means of temperature control. Scattering spectra of the microsphere are measured using a tunable narrow-linewidth diode laser, and the frequency scale is precisely calibrated from a simultaneously observed spectrum of rubidium vapor. The resonant frequencies of whispering-gallery modes can be varied linearly by temperature elevation and lowering, at a rate of -2.6 GHz/K for a 190 µm sphere.
A Bright Reflective Full-Color Liquid Crystal Display Using Optically Compensated Bend Cell with High Contrast Ratio and Wide Viewing Angle Range
Authors: Ishinabe Takahiro , Miyashita Tetsuya , Uchida Tatsuo , Suzuki Makoto
Published: February 2005

We have proposed a novel full-color reflective liquid crystal display (LCD) using a hybrid aligned LC cell, color filters of red, green and blue, a mirror electrode inside the cell and a light-diffusing film. In this paper, we describe a design concept for improving the contrast ratio of this reflective LCD. In addition, we propose an advanced reflective full-color LCD using a light-control film instead of a Gaussian-type light-diffusing film. This reflective LCD has a wide viewing angle, a high contrast ratio and a high resolution and is promising as a high-quality reflective full-color LCD for next-generation portable information systems.
Blue Luminescence from Divalent Europium Supported by Anodic Alumina
Authors: Tanigawa Go , Morisaki Shigeyoshi
Published: February 2005

The fluorescence of divalent europium is important in blue luminescence such as that used in plasma displays. This research aimed to develop a useful method for producing divalent europium fluorescence. Anodic alumina was used as a support material and the conditions under which divalent europium is stable were examined. The design of material by DV-Xα molecular orbital simulation and the structure of aluminum oxide in which divalent europium ions are stable were examined. The electroluminescence of divalent europium was confirmed.
Finding Electrical Characteristics of a Piezoelectric Transformer through Open-Circuit Operation
Authors: Chang Kuo-Tsi
Published: February 2005

In this paper we investigate the electrical transient responses of a piezoelectric transformer (PT) under open-circuit operation and its response times. The transient responses are induced on both sides of the PT immediately after the AC voltage applied to the PT is switched off. An equivalent circuit with initial conditions is expressed first. Then, the equivalent circuit is used to derive an input voltage transient response and its response times. Moreover, an AC power supply system with a control switch is used to determine the transient responses, and an oscilloscope with a smoothing-and-filtering function is used to measure the transient responses and their DC components. Furthermore, the effects of load resistance, switching-off time and operating frequency on the transient responses are measured and discussed. From the measured results, the DC component of each output voltage transient response is almost zero and the AC response time of the output transient response is greatly decreased from 11.5 ms under an output open to 3.0 ms by adopting a 1 MΩ load resistance.
Difference in Thermal Degradation Behavior of ZrO2 and HfO2 Anodized Capacitors
Authors: Kamijyo Masahiro , Onozuka Tomotake , Yoshida Naoto , Shinkai Satoko , Sasaki Katsutaka , Yamane Misao , Abe Yoshio
Published: February 2005

Microcrystalline ZrO2 and HfO2 thin film capacitors were prepared by anodizing sputter-deposited Zr and Hf films. The thermal degradation behavior of both anodized capacitors was clarified by the measurement of their capacitance properties and Auger depth profiles before and after heat treatment in air. As a result, it is confirmed that the heat-resistance property of the HfO2 anodized capacitor is superior to that of the ZrO2 capacitor. In addition, it is revealed that the thermal degradation of the ZrO2 anodized capacitor is caused by the diffusion of Zr atoms from the underlying layer into the ZrO2 anodized layer, while that of the HfO2 anodized capacitor is caused by the diffusion of oxygen atoms from the anodized layer into the underlying Hf layer.
Determination of Anchoring Energy in Nematic Liquid Crystal Cells with Controllable Twist Angles Using a Stokes Parameter Method
Authors: Kawamura Marenori , Goto Yoshiaki , Sato Susumu
Published: February 2005

An accurate measurement method for determining the two-dimensional distribution of an azimuthal anchoring energy is developed by continuously controlling the combination angle between two rubbing alignment films of a sample liquid crystal cell. The anchoring energy can be precisely obtained by measuring actual cell parameters, such as cell thickness and the twist angle of the liquid crystal (LC) cell by torque balance and Stokes parameter methods.
Effect of Non-DC Voltage Applied during N*–SmC* Phase Transition on Alignment of Half-V-Shaped Switching Ferroelectric Liquid Crystal
Authors: Hotta Aira , Hasegawa Ray , Takatoh Kohki
Published: February 2005

In a half-V-shaped switching ferroelectric liquid crystal (half-V FLC), a liquid crystal material with N*–SmC* phase transition is used. When the material is cooled from N* phase to SmC* phase without an applied electric field, two types of domain with spontaneous polarization (Ps) in the upward or downward direction to the substrate plane are formed. In the conventional half-V FLC, a DC voltage is applied to the liquid crystal during the phase transition to form either type of domain selectively. Is the DC voltage application indispensable for selecting one domain? To clarify this point and to reduce the expected residual charge due to the application of the DC voltage, various waveforms of non-DC voltage were studied. We achieved the formation of one type of domain by applying an asymmetric rectangular waveform adjusted to cancel the effective DC component, and the generation of residual charge was avoided. The obtained half-V FLC alignment showed desirable black appearance in the crossed polarizers.
Preparation of BaTiO3 Thin Films of Micrometer Range Thickness by Pulsed Laser Deposition on (001)LaAlO3 Substrates
Authors: Yeung Kai-Ming , Mak Chee-Leung , Wong Kin-Hung , Pang Geoffrey Kin-Hung
Published: February 2005

Thick BaTiO3 (BTO) films of up to 2.5 µm thickness have been deposited on (001)LaAlO3 (LAO) substrates using pulsed laser deposition (PLD). The evolution of structural properties with film thickness was investigated by X-ray diffraction (XRD) analysis, Raman spectroscopy, scanning electron microscopy (SEM) and atomic force microscopy (AFM). XRD and Raman analyses show that BTO films, with a thickness of up to 2.5 µm, are all c-oriented and epitaxially grown on LAO. No impurity (non-BTO) phase in the films has been detected. It is noted that the crystalline quality of the BTO films, as revealed by the narrowing of the full width at half maximum (FWHM) of the rocking curves, increases with film thickness. Moreover, SEM and AFM results demonstrate that large grain size and a rough surface are observed in thick films. On the basis of these results, it can be concluded that growing thick BTO films by PLD can produce improved crystalline qualities but decreased surface smoothness due to enhanced columnar grain growth.
Improvement in Laser-Induced Damage Threshold of Antireflection Coatings for High-Power UV Lasers by Removing Subsurface of Large lenses
Authors: Otani Minoru , Fujimura Hidehiko , Ishikura Junri , Yoshida Kunio
Published: February 2005

We improved the laser-induced damage threshold (LIDT) of antireflection coatings for a wavelength of 355 nm by removing the subsurface of the substrate with an ion beam etching system. The ion beam etching system is set up in a coating chamber to etch 1000 mm optics uniformly. The antireflection coating composed of MgF2, Al2O3 and SiO2 layers has an excellent LIDT of 9.2 J/cm2 which is the highest reported LIDT in the world (355 nm, 0.3 ns pulsed laser).
Redshift and Blueshift Due to Interaction between C–H Bond of Methyl Radicals and Highly Electronegative Oxygen
Authors: Oh Teresa , Lee Kwang-Man , Kim Kyung-Sik , Choi Chi Kyu
Published: February 2005

Conventional chemical shifts in organic compounds usually consist of a redshift; however, hybrid-type SiOC films were found to exhibit a redshit and a blueshift. These chemical shifts originate from the interaction between the C–H bond and highly electronegative oxygen. The bonding structures of SiOC films can be divided into two types depending on the observed chemical shifts and consist of a Si–O–C cross-link structure and a Si–O–C cage-link structure. The blue shift in SiOC films is associated with the porosity due to an increase in the number of electron-rich groups, such as methyl radicals, resulting in the formation of a Si–O–C cage link structure. On the other hand, the Si–O–C cross-link structure associated with a redshift is generated from the adhesion due to C–H bond elongation.
High-Resolution Imaging of Recording Marks on Phase-Change Film by Lateral Force Microscopy
Authors: Ishiyama Osamu
Published: February 2005

Recording marks on a phase-change optical disk were observed by lateral force microscopy (LFM), and the images were compared with those obtained by Kelvin force microscopy (KFM). The spatial resolution of LFM was considerably better than that of KFM. Therefore it is expected that LFM will become one of the effective techniques for evaluating the shapes of recording marks in next-generation phase-change optical disks.
Formation of Aluminum Schottky Contact on Plasma-Treated Cadmium Telluride Surface
Authors: Toyama Hiroyuki , Nishihira Atsushi , Yamazato Masaaki , Higa Akira , Maehama Takehiro , Ohno Ryoichi , Toguchi Minoru
Published: February 2005

We have studied the effect of plasma treatment on the rectification property and performance of the CdTe radiation detector with the Al Schottky electrode. The Te-rich layer on the CdTe surface etched with Br-methanol caused the degradation of the rectification property of the Al/CdTe Schottky contact. To remove the Te-rich layer, plasma treatment was carried out. The plasma treatment did not roughen the CdTe surface, and it removed the Te-rich layer. In terms of current–voltage characteristics of the Al/CdTe Schottky contact, the leakage current of the samples with plasma treatment was lower than that of the samples without plasma treatment. Moreover, in terms of detector performance, the samples with plasma treatment showed a higher energy resolution than those without plasma treatment. We achieved a high energy resolution of 1.6 keV FWHM at 59.5 keV using the plasma-treated Al/CdTe/Pt detector, which is comparable to the value obtained using a conventional Schottky-type In/CdTe/Pt detector.
Ozone Generation by a DC Driven Micro-Hollow Cathode Discharge in Nitrogen-Mixed Oxygen Flow
Authors: Yamatake Atsushi , Yasuoka Koichi , Ishii Shozo
Published: February 2005

The ozone generation characteristic of a DC driven micro-hollow cathode discharge was studied in nitrogen-mixed oxygen gas flow. An ozone concentration of 13.7 g/Nm3 was obtained at an efficiency of 97 g/kWh in pure oxygen. However, ozone concentrations of 8.2 g/Nm3 and 25 ppm ozone were obtained in gas mixtures of 4% and 80% N2-mixed oxygen gases, respectively. There was a threshold specific energy above which ozone concentration markedly decreased. High-energy electrons dissociate the nitrogen molecules and generate NO and NO2 which accelerate the ozone decomposition in high-power-density plasmas such as a micro-hollow cathode discharge.
Polymer Treatment by Plasma Immersion Ion Implantation of Nitrogen for Formation of Diamond-Like Carbon Film
Authors: Tan Ing Hwie , Ueda Mario , Kostov Konstantin , Nascente Pedro Augusto P. , Demarquette Nicole Raymonde
Published: February 2005

Nitrogen ions were implanted by plasma immersion in Kapton, Mylar and polypropylene, with the objective of forming a diamond-like carbon layer on these polymers. The Raman spectrum of the implanted polypropylene showed typical Diamond-Like Carbon (DLC) graphite (G) and disorder (D) peaks, with an sp3/sp2 hybridization ratio of approximately 0.4 to 0.6. The XPS analysis of the three implanted polymers also showed peaks of C–C and N–C bonds in the sp3 configuration, with hybridization ratios in the same range as the Raman result. The implanted polymers were exposed to oxygen plasma to test the resistance of the polymers to oxygen degradation. Mass loss rate results, however, showed that the DLC layer formed is not sufficiently robust for this application. Nevertheless, the layer formed can be suitable for other applications such as in gas barriers in beverage containers. Further study of implantation conditions may improve the quality of the DLC layer.
Observation of Ripplon on the Liquid Droplet Adhered to the Tip of an Optical Fiber
Authors: Mitsui Takahisa
Published: February 2005

Using Michelson interferometry, we have observed thermal vibrations on the surface (ripplon) of a liquid droplet adhered to the tip of an optical fiber. By causing the liquid droplet to adhere to the tip of an optical fiber, we are able to observe the ripplon with a very small quantity (10-7 cm3) of liquid. Moreover, the measurement is possible without being influenced by the direction of gravity or the vibration of the measurement environment, since the liquid adheres strongly to the optical fiber by intermolecular force. The ripplon spectrum on the surface of the oil droplet adhered to the tip of an optical fiber of diameter 80 µm was observed to be uniform up to 1 kHz and decreased as 1/f above 1 kHz. We observed the ripplon standing waves at nearly 20 kHz on surfaces of ethanol, methanol and water.
Analytical Study of Acoustic Mechanism of “Suikinkutsu”
Authors: Watanabe Yoshio
Published: February 2005

In this report, I describe an experimental analysis of the acoustic mechanism of the suikinkutsu. The sound of the suikinkutsu consists of an original sound generated by water drops striking the surface of the water in the suikinkutsu and a reverberant sound generated by the original sound. The reverberant sound is the sound we hear through the observation holes of the suikinkutsu. The body of the suikinkutsu also has its own natural frequencies and vibrates in synchronism with the natural frequencies of the oscillation modes of air inside it, affecting the tonal quality of the sound emitted from the suikinkutsu. If all of the natural frequencies and time constants of the reverberant sound are optimized, the suikinkutsu can produce a sound of good tonal quality. In this study, we investigate the relationships between the original sound and the reverberant sound emitted from the suikinkutsu. We propose an experimental formula representing the natural frequencies of the suikinkutsu and examine the validity of this formula.
A New Spectral Imaging Ellipsometer for Measuring the Thickness of Patterned Thin Films
Authors: Chegal Won , Cho Yong Jai , Kim Hyun Jong , Cho Hyun Mo , Lee Yun Woo , Kim Soo Hyun
Published: February 2005

We proposed spectral imaging ellipsometry that uniquely combines one-dimensional imaging and spectroscopic ellipsometry. This type of ellipsometry enables the measurement of the optical parameters and dimensional structures of patterned or multilayered thin films. We demonstrated the result of the measurement of the thickness of patterned SiO2 layers with 3 nm accuracy and 200 µm spatial resolution.
Detection of 5.5 MeV α-particles with a Magnetic Calorimeter
Authors: Sato Kosuke , Ishikawa Teru , Ishisaki Yoshitaka , Ohashi Takaya , Oshima Tai , Yamasaki Noriko Y.
Published: February 2005

We report on the detection of signals from 5.5 MeV α-particles with a Au:Er magnetic calorimeter. Since this device shows strong temperature dependence on magnetization, the incident particle energy is measured by a change in the degree of magnetization using a superconducting quantum interference device (SQUID). We fabricated a sensor made of Au doped with ∼0.3% Er in our laboratory, and irradiated it with 241 Am in a dilution refrigerator. The detected signals showed an average pulse height of 7 mV, corresponding to a 2 pA m2 change in the magnetic moment of the sensor, at a bath temperature of 80 mK under an external magnetic field of 0.1 mT.
Epitaxial PbTiO3 Thin Films on SrTiO3(100) and SrRuO3/SrTiO3(100) Substrates Deposited by a Hydrothermal Method
Authors: Morita Takeshi , Cho Yasuo
Published: February 2005

Lead titanate (PbTiO3) thin film is a promising material for ultrahigh-density ferroelectric data storage systems, pyroelectric sensors and ferroelectric optical devices. In this study, high-quality epitaxial PbTiO3 thin films were deposited on SrTiO3(100) and SrRuO3/SrTiO3(100) by a hydrothermal method. The crystal orientation of the deposited film was investigated with a high-resolution X-ray diffraction mapping system. The full width at half maximum (FWHM) of the rocking curve of the (002) PbTiO3 film on SrTiO3 was 0.060°. The reciprocal space mappings of (103) verified that the PbTiO3 films had perfect c-axis orientation. The self-aligned polarization was confirmed with observation using a scanning nonlinear dielectric microscope. The PbTiO3 on SrRuO3/SrTiO3(100) was used for the D-E hysteresis curve measurement and the remanent polarization was 96.5 µC/cm2. Domain patterning was applied to a 50-nm-thick PbTiO3 film using a conductive cantilever probe. The minimum radius of the nano domain dot was 12 nm, corresponding to a data density of 1 Tbit/inch2.
Preparation of m=1–2 Series Natural-Superlattice-Structured Bismuth-Layer-Structured Ferroelectric Thin Films
Authors: Shibuya Akira , Noda Minoru , Okuyama Masanori , Saito Keisuke
Published: February 2005

C-axis-oriented epitaxial natural-superlattice-structured Bi2MoO6–Bi3TiNbO9 (BM–BTN) (m=1–2) and Bi2WO6–Bi3TiNbO9 (BW–BTN) (m=1–2) films are grown by pulsed-laser deposition (PLD) on SrTiO3 (001) substrates. The c-lattice constant (6.738 nm) of the BM–BTN film is very close to that (6.54 nm) of the superlattice structure of one BM unit cell and two BTN unit cells. The c-lattice constant (2.089 nm) of the BW–BTN film is very close to that (2.07 nm) of the superlattice structure of one BW unit cell and one BTN unit cell. The long-range natural-superlattice-structure of BM and BTN films have been prepared on Pt(111)/TiO2/SiO2/Si substrates by PLD and oxygen postannealing at 650°C. X-ray diffractions clearly show the formation of the long-range superlattice of the 15.5 nm iterative layer, which corresponds to 50 unit cells consisting of (113)-oriented BM and (115)-oriented BTN. These BM BTN thin films exhibit good ferroelectricity with a 2P

r
of 40 µC/cm2.
Synthesis of Bi(FexAl1-x)O3 Thin Films by Pulsed Laser Deposition and Its Structural Characterization
Authors: Okada Morihiro , Yoshimura Takeshi , Ashida Atsushi , Fujimura Norifumi
Published: February 2005

We have been attempting to synthesize perovskite BiAlO3 as a new lead-free piezoelectric material. No indication of the formation of the BiAlO3 phase by the bulk ceramic processing or thin film processing has been obtained. Therefore, we undertook to synthesize a solid solution of BiAlO3 and BiFeO3, which has a stable perovskite structure and contains Bi as a component element. Bi(Fe
x
Al1-x
)O3 solid solution could not be obtained by bulk ceramic processing. However, we succeeded in the fabrication of single-phase Bi(Fe
x
Al1-x
)O3 thin films on (001) SrTiO3 substrates by pulsed laser deposition. The crystal structure was revealed to be rhombohedral at x=1 and tetragonal at x=0.9.
Influence of Mixing Condition and Nonstoichiometry on Piezoelectric Properties of (K, Na, Pb)NbO3 Ceramics
Authors: Tashiro Shinjiro , Nagata Kunihiro
Published: February 2005

To obtain a uniform mixture of raw material powders including K2CO3 and Na2CO3, the raw material powders were ball-milled in a mixture of water and methanol (first-stage mixing). After the first-stage mixing, the dried powders were mixed again by ball-milling in acetone (second-stage mixing). Samples were fabricated using the two mixing methods, one-stage mixing and two-stage mixing. In the material composition formula, (Pb0.03K0.47Na
x
)Nb0.994O3, the composition was changed from A-site rich to B-site rich by reducing Na content in steps of 0.01 from x=0.50. The change in the piezoelectric properties of these samples was measured. As the B-site ion concentration exceeds A-site ion concentration, the crystal structure changed from pseudocubic to orthorhombic. The electromechanical coupling factor and remanent polarization of the samples increased in accordance with the change in crystal structure. The defect structure having A-site vacancies due to a B-site-rich composition is effective in inducing ferroelectricity.
Theoretical Study of Atomic Relaxation in 90° Domain Walls of Ferroelectric Perovskite Films
Authors: Ricinschi Dan , Ishibashi Yoshihiro , Okuyama Masanori
Published: February 2005

In this work we study the extent of atomic relaxation in the 90° domains of a ferroelectric film assumed to be in the tetragonal phase, epitaxially grown on a cubic substrate. The problem is solved within the framework of a Frenkel-Kontorova-type model, that is, a discrete chain of atoms harmonically coupled and subjected to the periodical action of an on-site substrate potential. The equilibrium atomic displacements as a function of the model parameters, including film and substrate lattice constants, have been analytically calculated by solving the Euler-Lagrange equations and minimizing total energy. We have applied the model for calculating atomic displacements in PbTiO3 and BaTiO3 thin films constrained to typical substrates. Predictions are made concerning the optimal substrate period ensuring the coherent matching between atoms in the ferroelectric layer and substrate atoms.
Raman Scattering Behaviors of GaN Single Crystal Grown by a Na Flux Method
Authors: Park Sang Eon , Cho Chae-Ryong , Cho Yong Chan , Jeong Se-Young
Published: February 2005

Bulk GaN single crystals above 4 mm in size were grown by a Na flux method. Micro-Raman scattering from bulk GaN crystals was performed over the temperature range from 80 K to 300 K. The results obtained reveal that Raman phonon frequency decreases with increasing temperature. This temperature dependence of optical phonons is well described by an empirical relationship that has proved to be effective for other semiconductors. Small 667 cm-1 peaks appeared systematically on every piece of bulk GaN. We suggest that lattice-disorder-induced modes are mainly responsible for the 667 cm-1 peaks associated with the presence of Fe and Cr ions in the GaN crystals grown by the Na flux method.
Novel Method of Intrinsic Characteristic Extraction in Lightly Doped Drain Metal Oxide Semiconductor Field Effect Transistors for Accurate Device Modeling
Authors: Tada Kenshi , Matsuoka Toshimasa , Taniguchi Kenji , Maeda Kazuhiro , Sakai Tamotsu , Kubota Yasushi , Imai Shigeki
Published: February 2005

A lightly doped drain (LDD) region, particularly a gate-overlapped LDD (GOLD) region, is subjected to a gate electric field and its gate-controlled resistance affects the device characteristics. We developed a new extraction method for determining the intrinsic characteristics of LDD MOSFETs using a simple series resistance model, in which the GOLD region is assumed to be a depletion MOSFET with a negative threshold voltage derived from C–V measurement. Polycrystalline-silicon (poly-Si) TFTs with a channel length of 4–100 µm were used for the test LDD samples, particularly GOLD MOSFETs. It was demonstrated that the new proposed method precisely extracts the intrinsic characteristics of poly-Si GOLD TFTs by comparing them with the intrinsic characteristics of poly-Si Self-Aligned (SA) TFTs extracted by the conventional method.
Reduced Defect Densities in Cubic GaN Epilayers with AlGaN/GaN Superlattice Underlayers Grown on (001) GaAs Substrates by Metalorganic Vapor Phase Epitaxy
Authors: Sugiyama Mutsumi , Nosaka Taiki , Suzuki Tomonori , Koida Takashi , Nakajima Kiyomi , Aoyama Toyomi , Sumiya Masatomo , Chikyow Toyohiro , Uedono Akira , Chichibu Shigefusa F.
Published: February 2005

The effects of Al
x
Ga1-x
N/GaN superlattice (SL) insertion on the structural homogeneity, photoluminescence (PL) lifetime (τPL), and defect densities were studied in cubic (c-) GaN epilayers on (001) GaAs substrates grown by low-pressure metalorganic vapor phase epitaxy. Values of the full-width at half maximum (FWHM) of both the (002) X-ray diffraction peak and near-band-edge excitonic PL peak were significantly decreased by the insertion of appropriate short-period AlGaN/GaN SLs between the c-GaN epilayer and the c-GaN template layer prepared on a substrate-decomposition-shielding GaN layer deposited at a low temperature. The density or size of Ga-vacancy (V
Ga)-related defects in the c-GaN epilayer was significantly reduced. Simultaneously, the value of excitonic PL lifetime at 293 K was improved from approximately 20 ps to 230 ps, indicating a tremendous reduction of the nonradiative defect density.
Universal Visible Antireflection Coating Designs by Tuning Iteration Technique
Authors: Liou Yeuh-Yeong
Published: February 2005

A simple straightforward design algorithm based on the tuning iteration search is applied to design universal visible antireflection coatings for substrates with indices in the range of 1.45 to 1.784. The method uses a two-material multilayer system starting with a binary code of alternating high and low indices and with all sublayers initially set at equal physical thickness. The thicknesses of all layers are subsequently tuned one by one and one at a time to improve the average reflectivity over the visible spectral region until the antireflection performance stabilizes. It is found that the 30-layer tuning iteration designs for visible antireflection coating 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 lead the final designs to 10–12 layer structures and the average visible spectral reflectivities for the substrates are reduced to approximately 0.173–0.190%.
GaN-Based White-Light-Emitting Diodes Fabricated with a Mixture of Ba3MgSi2O8:Eu2+ and Sr2SiO4:Eu2+ Phosphors
Authors: Kim Jong Su , Kang Ji Young , Jeon Pyung Eun , Choi Jin Chul , Park Hong Lee , Kim Tae Whan
Published: February 2005

The photoluminescence (PL) spectra of Ba3MgSi2O8:Eu2+ show one peak at 442 nm and two unresolved peaks at 505 nm. The 442 nm peak is attributed to the 4f→5d transition of the Eu2+ ion doped in the Ba2+(I) site with a weak crystal field, while the 505 nm peak originates from Eu2+ ions on the Ba2+(II) or the Ba2+(III) site with a strong crystal field. The PL spectra of the Sr2SiO4:Eu2+ show two emission peaks at 470 nm and 560 nm. The emission intensity at 470 nm decreases with increasing Eu2+ concentration, while that at 560 nm increases. This can be understood by considering the energy transfer from the 470 nm band to the 560 nm band through multipolar interaction. The GaN-based white-light-emitting diode (LED) fabricated using a mixture of Ba3MgSi2O8:Eu2+ and Sr2SiO4:Eu2+ phosphors has a broad-band spectrum, higher color rendering index and higher color stability against forward bias currents than Y3Al5O12:Ce3+-based white-LEDs.
High-Power, High-Brightness 1 cm Laser Diode Bar with V-Shaped Optical Waveguide Structure
Authors: Miyajima Hirofumi , Watanabe Akiyoshi , Matsuura Masaaki , Kan Hirofumi
Published: February 2005

We have developed a V-shaped optical waveguided laser diode (LD) and dramatically improved the brightness of LD output. Due to the V-shaped ridge structure, spatial lasing modes in the LD cavity were effectively selected using a combination of the total internal reflection and the apex of the V-shaped waveguide. We fabricated 164 strips of 30 µm V-shaped LD emitters on a 1 cm LD bar and achieved an optical output power of more than 95 W with an electricity-to-light conversion efficiency of approximately 30%. The divergence angle in the slow-axis direction of each LD measured 2.0 deg (34.9 mrad) in full-width at half maximum (FWHM) at an output power of 30 W, and 2.5 deg (43.6 mrad) or less even at output powers above 80 W. The brightness, defined by the power divided by the beam parameter product (BPP), reached 80 W/436 mm*mrad, which is approximately fivefold that of conventional LD bars with broad-area LDs (∼50 W/1400 mm*mrad).
Effects of Dye on Formation and Properties of Light-Induced Self-Written Waveguide
Authors: Shioda Tsuyoshi , Watanabe Noritoshi , Ozawa Hideaki , Mikami Osamu
Published: February 2005

The effects of rhodamine 6G dye on the formation and properties of a light-induced self-written waveguide (LISW) were demonstrated. We dispersed the 0.01 wt% dye in a conventional UV-curable resin and formed the LISW using a green laser. The excessive laser irradiation, which decomposed the dye, induced the solid cladding of the LISW at a wavelength which was shorter than the optical absorption peak. Thus, the dye was used not only as a sensitizer but also as the dominant factor for controlling the refractive index difference between the core and the solid cladding of the all-solid LISW.
Optical “NOT” Operation in a Light Transducer in which a High-gain Photoresponsive Organic Heterojunction Device is Combined with an Organic Electroluminescent Diode
Authors: Hiramoto Masahiro , Motohashi Yoshihito , Nagayama Norio , Kumaoka Hiroyuki , Yokoyama Masaaki
Published: February 2005

A multilayered device combining an organic electroluminescent (EL) diode with a high-gain organic photoresponsive heterojunction between phthalocyanine and perylene pigments was fabricated. The EL output under red light irradiation was reversibly erased by superimposing blue light irradiation, due to the photo-suppression of the photocurrent multiplication phenomenon at the organic/organic heterojunction. The spatial resolution for image conversion was confirmed to be finer than 280 µm. The present function can be regarded as an optical “NOT” operation.
Surface Smoothing Mechanism of AlN Film by Initially Alternating Supply of Ammonia
Authors: Yan Fawang , Tsukihara Masashi , Nakamura Akihiro , Yadani Takayuki , Fukumoto Tetsuya , Naoi Yoshiki , Sakai Shiro
Published: February 2005

A buffer technique that initially alternates supply of ammonia (IASA) is employed for AlN film growth on sapphire substrate by metalorganic chemical vapor deposition (MOCVD). Atomic force microscopy (AFM) study reveals that step-flow-like growth morphology is achieved for the AlN film with the root-mean-square (rms) roughness as small as 0.336 nm. In contrast, the surface morphology of thick AlN film grown directly on sapphire substrate shows rough grainy feature with a large rms value of 28.9 nm. The mechanism leading to superior morphology by introducing IASA process is investigated using transmission electron microscopy (TEM), hot wet chemical etching and scanning electron microscopy (SEM) techniques. Evidence is presented that their morphological differences are attributed to strain reduction and polarity inversion. The present work provides insight into the AlN epitaxial growth and indicates that IASA is an effective method to realize atomically smooth AlN film.
Effect of Molecular Weight of Surfactant in Nano Ceria Slurry on Shallow Trench Isolation Chemical Mechanical Polishing (CMP)
Authors: Kang Hyun-Goo , Katoh Takeo , Lee Myung-Yoon , Park Hyung-Soon , Paik Ungyu , Park Jea-Gun
Published: February 2005

We examined the effect of the molecular weight of surfactants in ceria slurry during chemical mechanical polishing (CMP) for shallow trench isolation (STI). We found that for a surfactant with a higher molecular weight, the oxide removal rate decreased drastically as the surfactant concentration increased, but in the case of a lower molecular weight, it only slightly decreased. In addition, slurries whose surfactants had lower molecular weights maintained a higher nitride removal rate with increasing surfactant concentration. The results showed that the molecular weight and surfactant concentration have complex effects on the oxide removal rate and the oxide-to-nitride removal selectivity.
Significantly Enhanced Coupling Efficiency in 2D Photonic Crystal Waveguides by Using Cabin-Side-Like Tapered Structures at Two Terminals
Authors: Chau Yuan-Fong , Yang Tzong-Jer , Gu Ben-Yuan
Published: February 2005

We report that using a cabin-side-like tapered structure, containing only one pair of defects, can markedly enhance the coupling efficiency at the entrance and exit terminals of planar photonic crystal waveguides (PPCWGs). The PPCWGs are composed of circular dielectric rods set in 2D triangular lattices. By means of simulations, we find that the transmission efficiency reaches up to 90%. Moreover, the suggested structures possess other advantages, such as the shortness of the taper, the ease of fabrication, and its low cost. It is anticipated that the proposed structures might be feasibly be applicable to the integrated optical circuits compatibility.
Low-Acceleration-Voltage Electron Irradiation Damage in Single-Walled Carbon Nanotubes
Authors: Suzuki Satoru , Kanzaki Kenichi , Homma Yoshikazu , Fukuba Shin-ya
Published: February 2005

Low-acceleration-voltage electron irradiation effects on single-walled carbon nanotubes were studied by resonant Raman spectroscopy. The irradiation at acceleration voltages of 0.5 to 25 kV was found to extinguish the characteristic optical property of the nanotubes and reduce their tolerance against annealing in air, indicating that the nanotubes are inevitably damaged by ordinary scanning electron microscope observation. The acceleration voltage of around 1 kV caused the most extensive damage. Less defective SWNTs were found to have a higher tolerance against the irradiation damage.
Immobilization of Probe DNA on Ta2O5 Thin Film and Detection of Hybridized Helix DNA using IS-FET
Authors: Ohtake Toshihito , Hamai Chiho , Uno Takeshi , Tabata Hitoshi , Kawai Tomoji
Published: February 2005

We demonstrated developments of a non-labeling DNA (deoxyribonucleic acid) sensor by using a commercially available ion-sensitive field-effect transistor (IS-FET). A single strand DNA was immobilized on a Ta2O5 thin film on a gate electrode in the IS-FET, and the surface of the thin film was confirmed by XPS measurements. The results indicated that the DNA was immobilized on the Ta2O5 thin film. To detect the hybridization of DNA, we carried out measurements of I
drain-V
gs properties of IS-FETs immobilized by ss-DNA and ds-DNA hybridized by complemental target DNA. Then, the difference in threshold voltage was evaluated to be about 10 mV, and the amount of immobilized DNA as 6.3×107 [molecules/cm2]. Consequently, the non-labeling IS-FET DNA sensor is expected to be a novel measurement tool for diagnosing diseases.
Photochemical Deposition of ZnS Thin Films by Intermittent Illumination
Authors: Ichimura Masaya , Kobayashi Ryohei , Miyawaki Tetsuya
Published: February 2005

We prepared ZnS thin films by photochemical deposition (PCD) using continuous and intermittent illumination. The aqueous solution used for the deposition contains ZnSO4 and Na2S2O3, and H2SO4 for pH adjustment. The solution is illuminated with light from an ultrahigh-pressure mercury arc lamp. When the illumination is continuous, the deposited film is black and not transparent because of excess zinc in the film. When the illumination is turned on and off periodically by a mechanical shutter, the deposited film becomes gradually transparent with increasing “off” time. The film deposited by the intermittent illumination has an optical absorption edge near 350 nm and shows photoconductivity.
The Electrical and Material Properties of HfOxNy Dielectric on Germanium Substrate
Authors: Zhang Qingchun , Wu Nan , Zhu Chunxiang
Published: February 2005

Hafnium oxynitride (HfO
x
N
y
) film was investigated as a possible gate dielectric of germanium metal–oxide–semiconductor (MOS) device. The thin HfO
x
N
y
dielectric was prepared using reactive sputtering, followed by post deposition annealing (PDA). The dependence of the equivalent oxide thickness (EOT) on PDA condition was investigated. A small EOT of 19.7 Å with a low leakage current of 3.1×10-5 A/cm2 (V
g=1 V) was achieved with PDA at 600°C. In addition, the material properties of HfO
x
N
y
on germanium were analyzed by X-ray photoelectron spectroscopy. The nitrogen is found to pile up at the dielectric/substrate interface and to form Ge-N bonds, which contribute to the interfacial layer (IL) suppression.
Enhancement of Surface-Damage Resistance by Removing Subsurface Damage in Fused Silica and Its Dependence on Wavelength
Authors: Kamimura Tomosumi , Akamatsu Shigenori , Horibe Hideo , Shiba Haruya , Motokoshi Shinji , Sakamoto Takayasu , Jitsuno Takahisa , Okamato Takayuki , Yoshida Kunio
Published: February 2005

A combination of several surface etching techniques and a superprecise polishing process was used to remove subsurface damage from fused silica surface. The effect of subsurface damage removal on laser-damage resistance was determined by measuring the laser-induced damage threshold (LIDT) at 1064 nm, 532 nm, 355 nm and 266 nm. Surface-damage resistance was enhanced as the irradiated laser wavelength shortens. At 266 nm, the greatest advantage was obtained from virtually subsurface removed surfaces. The surface LIDT improved 2.8-fold compared with that of conventionally polished fused silica surfaces.
Group-Delay Properties of Coupled-Defect Structures in Photonic Crystals
Authors: Fukamachi Toshihiko , Hosomi Kazuhiko , Katsuyama Toshio , Arakawa Yasuhiko
Published: February 2005

Changes in group-delay properties of coupled-defect structures formed in one-dimensional photonic crystals were systematically studied. It was found that the edge region of the photonic crystal plays an essential role in forming a smoothed wavelength-dependence of the group delay, which is important for avoiding degradation of the light-pulse transmission. Utilizing this knowledge, the authors designed an optimized structure that is composed of SiO2/Ta2O5 layers and produces the transmittance of nearly 100% and the smoothed group-delay curve. A fabricated sample structure confirmed the designed characteristics and, thus, shows the potential applications of the coupled-defect structure to optical devices such as dispersion compensators.
GaInNAs Intermediate Layer for Improvement of Lasing Characteristics of GaInNAs Quantum Well Lasers
Authors: Kawaguchi Masao , Miyamoto Tomoyuki , Saitoh Atsushi , Koyama Fumio
Published: February 2005

We report on GaInNAs intermediate layer (IML) structures for improving the lasing characteristics of GaInNAs quantum well (QW) lasers. Either lattice-matched or strained (∼0.65%) GaInNAs IMLs were inserted at GaInNAs/GaAs interfaces. The elongation of the emission wavelength of IML QW structure was observed while maintaining the photoluminescence (PL) emission efficiency in comparison with that of the GaAs barrier QW structure. The elongation of the lasing wavelength of GaInNAs QW lasers without a threshold penalty was also demonstrated by employing a GaInNAs IML. The IML QW exhibited a reduction in the amount of the wavelength blue shift due to postgrowth thermal annealing.
Room-Temperature Hydrogen Sensor Based on Pd-Capped Mg2Ni Thin Film
Authors: Yoshimura Kazuki , Yamada Yasusei , Okada Masahisa , Tazawa Masato , Jin Ping
Published: February 2005

Pd-capped Mg2Ni alloy thin films were prepared by DC magnetron sputtering using Mg, Ni and Pd targets, and their hydrogen sensing characteristics have been investigated. Pd-capped Mg2Ni films with thicknesses of 10 nm Pd and 40 nm Mg2Ni show a good hydrogen sensing property for hydrogen-containing air at room temperature. Their sensing range is from 0.01% to 10% hydrogen in air. These films are supposed to be candidates for low-cost room temperature hydrogen sensor.
Improving the Quality of Protein Crystals Using Stirring Crystallization
Authors: Adachi Hiroaki , Matsumura Hiroyoshi , Niino Ai , Takano Kazufumi , Kinoshita Takayoshi , Warizaya Masaichi , Inoue Tsuyoshi , Mori Yusuke , Sasaki Takatomo
Published: February 2005

Recent reports state that a high magnetic field improves the crystal quality of bovine adenosine deaminase (ADA) with an inhibitor [Kinoshita et al.: Acta Cryst. D59 (2003) 1333]. In this paper, we examine the effect of stirring solution on ADA crystallization using a vapor-diffusion technique with rotary and figure-eight motion shakers. The probability of obtaining high-quality crystals is increased with stirring in a figure-eight pattern. Furthermore, rotary stirring greatly increased the probability of obtaining high-quality crystals, however, nucleation time was also increased. The crystal structure with the inhibitor was determined at a high resolution using a crystal obtained from a stirred solution. These results indicate that stirring with simple equipment is as useful as the high magnetic field technique for protein crystallization.
InGaAsP/InP Laser Diodes Monolithically Integrated with Waveguide-Type Light Deflectors
Authors: Kim Kang Ho , Kwon Oh Kee , Kim Jong-hoi , Kim Hyun Soo , Sim Eun Dok , Kim Sok Won , Oh Kwang Ryong
Published: February 2005

A ridge waveguide-type InGaAsP/InP laser diodes monolithically integrated with light deflectors (DLDs) were fabricated and light deflection was demonstrated, for the first time. The light deflection was simulated and measured in a fabricated device. The output beam deflection in a fabricated device was controlled by carrier induced refractive index change of the deflector. The maximum beam deflection angle of 3.12° was obtained at an applied current of 15 mA.
Effect of Far-Infrared Light Irradiation on Water as Observed by X-Ray Diffraction Measurements
Authors: Shimokawa Shigezo , Yokono Tetsuro , Mizuno Tadahiko , Tamura Hiroki , Erata Tomoki , Araiso Tsunehisa
Published: February 2005

X-ray diffraction measurements were made on water irradiated with far-infrared (FIR) light. It was found that the X-ray diffraction intensity at a 2θ angle of 30° increased by about 2 times with the irradiation. The increase in the X-ray diffraction intensity was interpreted in terms of the destruction of water clusters.
Electro-Optical Properties of Reverse Mode Polymer Dispersed Liquid Crystal Films
Authors: Chen Tien-Jung , Chen Yu-Fan , Sun Chia-Hsing , Wu Jin-Jei
Published: February 2005

We employ biphenyl methacrylate type monomer with varied functional groups to make the reverse mode polymer dispersed liquid crystal (PDLC) films. The films under investigation are formed with various composite ratios of liquid crystal and monomer. The experimental results demonstrate significantly improved contrast ratio and driving voltage.
Bright White Organic Light-Emitting Diodes Based on Anthracene Derivatives and Rubrene
Authors: Wang Liduo , Duan Lian , Lei Gangtie , Qiu Yong
Published: February 2005

Highly efficient and chromatically stable white organic electroluminescence (EL) devices based on blue-emitting anthracene derivatives doped with yellow-orange-emitting 5,6,11,12-tetraphenylnaphthacene (rubrene) are described. The relative intensities of the blue and orange-yellow emissions could be fine tuned by varying the doping concentration of the rubrene in the host to achieve pure white emission in a simple single-emissive-layer device structure. A double-doped device with 9,10-di-(2-naphthyl)-anthracene (D2NA): 2.5% 9,10-di-(2-naphthyl)-2-terbutyl-anthracene (D2NBA): 0.025% rubrene as the emissive layer shows a maximum brightness of 20,100 cd/m2, a peak external quantum efficiency of 2.4% (5.6 cd/A) at 9 V with Commission Internationale de L'Eclairage (CIE) coordinates of (0.32, 0.34) independent of the luminance output.
Fixing Atmospheric Nitrogen into Alcohol and Simultaneous Generation of Hydrogen on the Atomic Force Microscopy (AFM) Tip
Authors: Matsuura Hiroshi , Tanikawa Tamio , Kondou Kazutaka , Takaba Hiromitsu
Published: February 2005

We demonstrate plasma-induced fixing of atmospheric nitrogen during 1-butanol polymerization. Nitrogen atoms of 13 to 47 weight percent were fixed to 1-butanol polymer during this reaction, and the ratio of nitrogen atoms in the polymer was adjusted by the emission time of the electrons. The method can also be applied to other sets of solutions and gases.
Transmission Characteristics of Smiling Pattern Resonators
Authors: Hsu Yi-Jang , Chern Jyh-Long
Published: February 2005

We propose and experimentally verify a novel metallic-microstructure composite that consists of smiling-pattern resonators to broaden the bandwidth of resonance, in contrast to the well known narrow-band split ring resonators in the field of meta-materials and left-handed negative-index media. The underlying idea is to introduce multiple interaction scales to the resonator. Our microwave analog experiment shows that the range of resonant frequencies could also be extended apparently with double resonance bands. Furthermore, this smiling-pattern resonator is superior in manufacturing for its simplicity in structure.