bluuebunny/crossref_metadata_2025 huggingface dataset:
Shape Transition in the Initial Growth of Titanium Silicide Clusters on Si(111)
Authors: Hsu H. F. , Chiang T. F. , Hsu H. C. , Chen L. J.
Published: February 2005

The growth of titanium silicide clusters has been observed for sub-monolayer Ti deposited on Si(111)-7×7. Irregular shape tetragonal Ti5Si4 islands were observed to grow at 600°C. On the other hand, the elongated orthorhombic-Ti5Si4 (O-Ti5Si4) clusters form at 700°C. The clusters underwent a rapid increase in length and slight reduction in width as the cluster area exceeds a critical size (∼15 nm2). The elongated clusters are oriented along three equivalent Si<2-20> directions of the Si(111) surface with O-Ti5Si4 (025)∥Si(2-20). The shape change is in agreement with theoretical prediction based on the strain relief mechanism.
Orientation Control of Molecular Chains in Polymers Using Atomic Force Microscopy
Authors: Kimura Kuniko , Kobayashi Kei , Yamada Hirofumi , Horiuchi Toshihisa , Ishida Kenji , Matsushige Kazumi
Published: February 2005

We successfully controlled the molecular orientation of flat-on lamellar crystals of the ferroelectric copolymer, vinylidenefluoride and trifluoroethylene (P(VDF-TrFE)), on Pt and Au surfaces utilizing atomic force microscopy (AFM). The orientation was controlled by scanning a cantilever tip in contact with the film surface whose temperature was kept at just below its melting point (T
m). The molecules were stretched in the scan direction and new edge-on crystals were subsequently formed, whose lamellar planes were perpendicular to the scan direction. We also attempted to modify an isotactic poly-1-butene (IPB) thin film and a polyaniline emeraldine base (PANI-EB) thin film utilizing AFM. In the case of IPB film, structures similar to edge-on crystals of P(VDF-TrFE) were obtained when modified with the film temperature kept at just below its T
m. The result strongly suggests that this orientation control technique is also applicable to IPB. On the other hand, in the case of PANI-EB film, we could obtain many ellipsoidal grains in the scanned area. One possible mechanism is that PANI-EB molecular chains were stretched parallel to the modification scan to form fibrils or bundles.
The Effect of Pile-Up and Contact Area on Hardness Test by Nanoindentation
Authors: Miyake Koji , Fujisawa Satoru , Korenaga Atsushi , Ishida Takao , Sasaki Shinya
Published: February 2005

We used atomic force microscopy (AFM) for the indentation test evaluating the indentation hardness of materials in the nanometer range. BK7, fused silica, and single-crystal silicon were used as test sample materials. The data analysis processes used to determine the contact area were important in evaluating the indentation hardness of the materials. The direct measurement of the size of the residual hardness impression was useful in evaluating the contact area even in the nanometer region. The results led us to conclude that AFM indentation using a sharp indenter is a powerful method for estimating the indentation hardness in the nanometer range.
Fabricating Five Atomic Force Microscopes with an Extremely Low Budget –A Student Project–
Authors: Mutsuo Tae , Nakazawa Tomonori , Niino Toshiki , Yamamoto Akio , Kim Beomjoom , Hoshi Yasuo , Ikeda Kokichi , Michihata Masahiro , Kawakatsu Hideki
Published: February 2005

At the Graduate School of The University of Tokyo, a technical training course was newly introduced from the summer term of 2003. Its aim was to allow the acquisition of the basics of scientific instrumentation, circuitry and programming. Eighteen students supervised by four professors fabricated five atomic force microscopes with a budget of just under 200,000 yen per microscope. This paper describes the details of the microscopes, how the course was organized, and what was achieved.
Individual Na Adatoms on TiO2(110)-(1×1) Surface Observed Using Kelvin Probe Force Microscope
Authors: Sasahara Akira , Uetsuka Hiroshi , Hiroshi Onishi** Hiroshi Onishi**
Published: February 2005

The work function of Na-deposited TiO2(110) surfaces was mapped using a Kelvin probe force microscope (KPFM). Individual Na adatoms were identified as topographic protrusions on atomically flat terraces of the TiO2 surface. The work function locally decreased by 0.1–0.5 eV on each adatom. The observed modulations of work function were interpreted with the electric permanent dipole moment caused by the electron transfer from the adatom to the substrate.
Structures of Adsorbed Initial Layers of Stearic Acid at the Liquid/Solid Interface
Authors: Takajo Daisuke , Nemoto Takashi , Isoda Seiji
Published: February 2005

The structures of stearic acid adsorbed initially on highly oriented pyrolytic graphite (HOPG) were examined at liquid/solid interfaces by scanning tunneling microscopy (STM). Depending on the concentrations of stearic acid in n-octylbenzene solutions, two structures were observed. For a saturated solution of stearic acid, the observed layer on HOPG was composed of large and stable domains under STM scanning, corresponding with the already reported structure (β-form). For low concentrations, molecular layers were also formed, but at the lowest concentration of 1.7 mM, the molecular layer became porous where an underlying layer with another structure (α-form) was observed. It was concluded that the α-form is the initially adsorbed layer and the second layer is formed as the β-form.
Scanning Tunneling Microscopy Observation of Electron Standing Waves on Au(111) Film with a Superconducting Tip
Authors: Xu Mingxiang , Xiao Zhanwen , Kitahara Masayo , Fujita Daisuke
Published: February 2005

Using low-temperature scanning tunneling microscopy (LT-STM) with normal metal tungsten tips and superconducting niobium tips, we have observed in real space the formation of electron standing waves by the scattering of surface state electrons at surface defects and step edges on a Au (111) surface. From constant-current STM images of the Au(111) surface observed at low temperature with both tips, we have observed the strong effects of tip materials on the interference of the two-dimensional (2D) electron waves. Compared with using tungsten tips, enhanced electron standing waves have been clearly observed using niobium tips at 4.2 K. A simple model has been proposed to explain these observed effects.
Miniaturized Optical Pickup and Mechanism for Mobile Optical Disc Drive
Authors: Togashi Mitsuhiro , Sasaoka Takayuki , Lee Ho-Cheol , Jeong Ho-Seop
Published: February 2005

Recently, the market for portable instruments has been increasing markedly. If a very small optical disc drive can be realized, it is expected that a new market for memories will be created, because the running cost of an optical disc is very low. The main issues in such realization are miniaturization of a loading mechanism with a disc cartridge and recording density growth. In this paper, we propose a miniaturized optical pickup and mechanism that realizes a 5-mm-high drive usable with a cartridge disc. An optical axis shift using a prism pair is introduced for using conventional optical parts. A plano-concave lens and a hologram lens are used to compensate for achromatic aberration. Finally, signals reproduced by the miniaturized pickup are showed. Data-to-clock jitter was 6.3% for Blu-ray Disc (BD) storage density.
Photo Replication of Birefringent Phase Structures
Authors: Verstegen Emile J. K. , Hendriks Benno H. W. , As Marco A. J. van , Tukker Teus W.
Published: February 2005

Dual layer blu-ray disc (BD) and dual layer small form factor optical drive (SFFO) as well as BD / digital versatile disc (DVD) / compact disc (CD) compatible systems, require phase structures to cope with the different amount of spherical aberration for the various different operating modes. Birefringent phase structures open up to the possibility to cope with these different amounts of aberration in the various readout modes, but so far no manufacturing methods are known which lead to low cost and stable structures. A novel replication method, based on the photo-polymerization of a liquid crystalline monomer is presented to make birefringent phase structures. Apart from enabling mass production, the process allows a phase structure to be directly produced on top of an ordinary objective lens, allowing weight and size reduction of the compatible optical pick up.
Recording of Multi-Level Run-Length-Limited Modulation Signals on Compact Disc/Digital Versatile Disc Rewritable Discs
Authors: Lo Feng-Hsiang , Kuo Ji-Wen , Tseng Nai-Heng , Ju Jau-Jiu , Howe Dennis
Published: February 2005

Multi-level (ML) recording technology increases the capacity of standard compact disc (CD) and digital versatile disc (DVD) rewritable systems with no change to the optical/mechanical unit. The feasibility of applying ternary run-length-limited (3L-RLL) modulation to recording/playback on standard CD/DVD phase change discs is discussed. The use of 3L-RLL modulation increases the recording density 50% relative to conventional binary RLL (2L-RLL) modulation currently used in CD and DVD systems.
Optimization of Write Conditions with a New Measure in High-Density Optical Recording
Authors: Ogawa Masatsugu , Nakano Masaki , Ohkubo Syuichi , Honma Hiromi , Ichimura Tsutomu , Iwanaga Toshiaki
Published: February 2005

We defined a new measure called the partial response signal-to-noise ratio (PRSNR) to evaluate signal quality in partial response maximum likelihood (PRML) detection, instead of measuring jitter. This PRSNR was adapted to optimize the write conditions of high-density optical recording in a PR(12221)ML system with blue laser detection. We confirmed that optimum power control (OPC) with PRSNR was able to accurately search for the optimum power of discs and that it was able to do this in a short time occupying less disc area. These results denote that it was sufficiently useful for actual optical disc drives. We also confirmed the feasibility of adjusting a write strategy with PRSNR.
Dependence of Differential Phase Detection Signals on Astigmatism in a Focused Spot
Authors: Shinoda Masahisa , Nakai Kenya , Mori Kazuo
Published: February 2005

We have simulated the differential phase detection (DPD) signal characteristics in the presence of astigmatism in the focused spot of an optical pickup for a DVD player. Both DPD signals generated from four elements and two elements of a four-segment photo-diode have been simulated. The DPD signal level and the offset level depend on the direction of astigmatism and the type of detection. In the two-element detection, astigmatism of 45 deg against the tangential direction of an optical disk deteriorates the DPD signal characteristics more severely than that of 0 deg along the tangential direction.
Soft-Output Decoding of 17 Parity Preserve/Prohibit Repeated Minimum Transition Runlength (PP) Code
Authors: Miyauchi Toshiyuki , Iida Yasuhiro , Watanabe Tetsu , Urakawa Yoshiyuki
Published: February 2005

We propose a novel trellis decoding technique for soft-output decoding of 17 parity preserve/prohibit repeated minimum transition runlength (PP) code. The trellis of the 17 PP code has 21 states and 79 branches. We applied the Bahl-Cocke-Jelinek-Raviv (BCJR) algorithm to the trellis to obtain a soft-input soft-output (SISO) decoder. Using this SISO decoder, we have developed a turbo-coded 17 PP system for optical recording. It is experimentally confirmed that the turbo-coded 17 PP system effectively improves the bit error rate (BER) of high-density optical storage.
System Stability against Fingerprints on Blu-ray Disc System
Authors: Higuchi Takanobu , Kobayashi Hideki , Takahashi Kazuo , Imai Tetsuya
Published: February 2005

To realize a cartridge-free Blu-ray disc system, we investigated the behavior of a servo system with fingerprint contamination, and the correlations between the system stability and shapes of fingerprints. As a result, we found that the primary factors of servo failure were not only reflectivity changes but also wavefront aberration caused by the presence of fingerprints. Useful parameters for detecting serious fingerprint contamination were focus and tracking servo error signals standardized by the focus sum signal and the ratio of the width to pitch of fingerprints. Finally, we fabricated test disks with artificial fingerprints to design drive systems for the cartridge-free Blu-ray disc system.
New High Speed File Format for High Definition Television Optical Disks
Authors: Ishikawa Kiyohiko , Koide Daiichi , Kishida Masahiko , Tokumaru Haruki , Nakamura Shoich
Published: February 2005

Optical disk systems have advantages over video cassette recorders for broadcasting because they provide excellent random access, reliability and archiving performance. However, the transfer data rates of optical disks are inadequate for use in broadcasting applications. An optical disk medium, a servo system and signal processing techniques were developed for a 200 Mbps read/write system with two optical heads that was aimed at application to high definition television (HDTV) news gathering. We also developed an original disk format (ODF) that features a new high speed file format which has two new characteristics for HDTV. One is a guaranteed minimum extent length and the other is separation of the recording areas for files and directories. Our high-speed optical disk emulator proved that ODF is requiered to achieve a consecutive data transfer rate of more than 200 Mbps per head.
Format of Optical Disk with Limited Number of Playback Times
Authors: Wu Guo-Zua , Chao Zu-Wen , Wang Yi-Jung , Tseng Nai-Heng , Chen Shu-Ching , Chen Yen-Lin , Hsu Wen-Hsing
Published: February 2005

To limit the number of playback times of a read-only-memory (ROM) disk, a new optical disk, wherein a part is designed to be made of rewritable material, is proposed and experiments on its feasibility have been carried out.
More than 20 GB Capacity Rewritable Disk with the Same Physical Parameters as that of Digital Versatile Disc, Using a New Recording Method and Domain Wall Displacement Detection
Authors: Miyakoshi Toshimori , Miyaoka Yasuyuki , Shiratori Tsutomu
Published: February 2005

We have developed a new light intensity modulation recording method called domain tail erasing method. This new recording method enables high-density recording far beyond the optical resolution limit with a medium combining the layer structure of domain wall displacement detection (DWDD) with that of light intensity modulation direct overwrite (LIMDOW). A recording performance nearly identical to that using magnetic field modulation (MFM) was confirmed with this method, using conventional optics with a wavelength of 660 nm and NA of 0.60.
Microexplosion Recording in Spin-Coated Polymer Films Including ZnO Nanoparticles for Three-Dimensional Optical Memory
Authors: Shiono Teruhiro , Yamamoto Hiroaki , Nishino Seiji
Published: February 2005

As a microexplosion recording material, we propose polymer films including ZnO nanoparticles (ZnO polyester composite) for write-once multilayered recording media. These media with the ZnO composite material can be fabricated by a spin-coating method and can be read at the violet wavelength of 0.405 µm. By the electromagnetic analysis of diffraction loss, we clarified the pit design and the optical performance for void formation recording. From the results of experiments performed using three kinds of mode-locked pulsed lasers (pulse widths of 150 fs, 16 ps and 6 ns), with a clear reflection microscope image of submicrometer pits, the microexplosion sensitivity was confirmed to be greatly improved by 14, 38 and 50 times, respectively.
Multilayer Optical Read-Only-Memory Disk Applicable to Blu-ray Disc Standard Using a Photopolymer Sheet with a Recording Capacity of 100 GB
Authors: Shida Noriyoshi , Higuchi Takanobu , Hosoda Yasuo , Miyoshi Hiroko , Nakano Akio , Tsuchiya Katsunori
Published: February 2005

We have been investigating a multilayer optical disk applicable to Blu-ray Disc (BD) standard using a photopolymer (2P) sheet in order to realize a recording capacity of 100 GB on a 12-cm-diameter disk. We had already developed a 2P sheet utilizing the multilayer disk. In this study, we developed a BD-type quad-layer disk using the 2P sheet, and investigated readout signals from each layer. The jitter values of layer 0 (L0), layer 1 (L1), layer 2 (L2) and layer 3 (L3) in the quad-layer disk were 6.5%, 7.1%, 7.3% and 6.6%, respectively. According to the analysis of the components of jitter values, the main factor behind the deterioration of jitter values is the crosstalk from adjacent layers. However, the jitter value of each layer was sufficient to reproduce the recorded data. From these results, we proved the feasibility of realizing the BD-type multilayer read-only-memory (ROM) disk with the recording capacity of 100 GB.
New Improvement Methods for Multispeed Initialization-Free Phase-Change Optical Disk
Authors: Miao X. S. , Shi L. P. , Tan P. K. , Li J. M. , Lim K. G. , Chong T. C.
Published: February 2005

Disk structure optimization, thermal balance design and a new writing strategy are proposed to further widen the speed range of multispeed recording for an initialization-free phase-change disk. Simulated results show a high cooling rate. Experimental results show that the initialization-free phase-change disk with three improvement methods has a broad range of recording speeds from 3.49 to 20.94 m/s, which correspond to a rotation speed of 1 to 6 times that of digital versatile disk-read only memory (DVD-ROM), respectively.
Super-Resolution Near-Field Phase Change Disk with Sb70Te30 Mask Layer
Authors: Shi Luping , Chong Towchong , Tan Pik Kee , Hu Xiang , Li Jianming , Miao Xiangshui , Yuan Hongxing , Yao Haibiao
Published: February 2005

Super-resolution near-field phase change optical disks with a new mask layer of Sb70Te30 were studied. Disks with two different structures were analyzed using optical and thermal simulation methods. The simulation results showed that the optical disk exhibited maximum response when nearly half the laser spot was covered by the mask. The fast response depended on optimizing both the disk structure and reading power to match a certain speed because the effect of super-resolution near-field structure (super-RENS) was related to the position between the laser beam and the hole formed in the mask layer. Experimental results showed that the disk with a thermal shield layer, which was inserted into the dielectric layer located between the mask layer and the phase change layer, demonstrated a better thermal stability than the disk without the thermal shield layer. This is in good agreement with simulation results. Recording marks as small as 62 nm were observed.
Study on 100 Gbit/inch2 Density Molding Using Double-Sided Heat Insulated Mold
Authors: Inoue Kazuo , Hayashi Kazuhiro , Kawasaki Yoshihiro , Ohno Eiji , Masuhara Shin , Kaneko Masahiko
Published: February 2005

Previously we showed substrates without any pit deformation in the case of injection molding a 40 Gbit/inch2 read only memory (ROM) substrate using the single-sided heat insulated mold, in which a heat insulating plate was located below a stamper, and the slow mold opening method. This type of mold is characterized by the fact that pits on the substrates can be replicated at a low mold temperature, to avoid the twisting of substrates. However, it was found that the radial tilt was large. Therefore, we investigated this phenomenon using simulations, and fabricated a double-sided heat insulated mold with a symmetric structure in the thickness direction of the substrates. We showed that performing injection molding using this double-sided mold rendered the radial tilt of substrates controllable, so that it was possible to obtain flat disks. Furthermore, we obtained a 120-mm-diameter 100 Gbit/inch2 ROM substrate, which had no pit deformation over the entire pit area even though the pit wall angle was greater than 80 deg. This density corresponds to approximately 140 Gbyte.
Enhancement of Electrical Conductivity in Thermoelectric [Ca2CoO3]0.62[CoO2] Ceramics by Texture Improvement
Authors: Itahara Hiroshi , Sugiyama Jun , Tani Toshihiko
Published: February 2005

In the preparation of textured ceramics of [Ca2CoO3]0.62[CoO2] (CCO-3-layer) by the reactive-templated grain growth (RTGG) method using β-Co(OH)2 templates, we have examined the effect of processing conditions on the orientation degree and thermoelectric properties of the resultant ceramics. All the RTGG-prepared ceramics showed a high degree of orientation with the Lotgering's factor reaching approximately 1. It was found, however, that texture differences detected by rocking curve measurement (in terms of the (004) plane of the CCO-3-layer) significantly affect the in-plane electrical conductivity, σ
a
b
. An increase in the orientation degree of β-Co(OH)2 templates in a green compact increased the orientation degree of the resultant CCO-3-layer ceramic that is formed on the templates by heat treatment. Furthermore, an increase in pressure and duration time of uniaxial pressing during heat treatment was found to increase the orientation degree of the CCO-3-layer ceramic. As a result, a ceramic with improved texture exhibited a rocking curve FWHM(004) of ∼6.0° (FWHM: full width at half maximum), and σ
a
b
(at 1060 K) of 2.61 ×104 S/m, which is approximately 1.7 times as large as that of the RTGG-prepared ceramic before refining the processing conditions.
In situ Observation of Clusters in Gas Phase during 4H-SiC Epitaxial Growth by Chemical Vapor Deposition Method
Authors: Ishida Yuuki , Takahashi Tetsuo , Okumura Hajime , Arai Kazuo , Yoshida Sadafumi
Published: February 2005

We have performed in situ observation of the chemical vapor deposition (CVD) of silicon carbide (SiC), and investigated the relationship between the growth conditions and generation of clusters in the gas phase of the H2–SiH4–C3H8 gas system to realize the high-speed growth of SiC by CVD. It was found that cluster generation can be suppressed by decreasing the partial pressure of the process gases, i.e., increasing the H2 carrier gas flow rate, and decreasing the pressure and process gas flow rate. We concluded that clusters in the gas phase consist of not only Si droplets, but also SiC particles.
Resonant Tunneling Transmission Characteristics and Tunneling Time in Asymmetrical Double-Barrier Structures with Multiple Prewells
Authors: Hamaguchi Hiroki , Yamamoto Hiroaki , Yamada Norifumi
Published: February 2005

Resonant tunneling phenomenon in the asymmetrical double-barrier structures with multiple prewells is studied theoretically. First, analytical expressions for the tunneling transmission coefficient and the resonance condition are derived. Second, analytical expressions for the dwell time and for the shortest dwell time condition are obtained. It is found that the dwell time in the main well region decreases greatly with increasing number of prewells, and that there exists an optimum number of prewells which makes the dwell time in the whole region shortest.
Influence of Bottom Electrodes and Interface Layers on (Ba,Sr)TiO3 Thin Film Leakage Current
Authors: Yamato Masaki , Yamada Hiroshi , Kikkawa Takamaro
Published: February 2005

The effect of bottom electrodes of (Ba,Sr)TiO3 (BST) thin film capacitors on leakage current characteristics was investigated. Iridium (Ir), titanium (Ti) and tantalum (Ta) bottom electrodes and SiN interface layer were deposited prior to BST deposition. On the basis of time-dependent and temperature-dependent leakage current characteristics, the leakage mechanism was investigated. It is found that the leakage current in BST with the Ta bottom electrode (Ir/BST/Ta/Si) is dominated by dielectric relaxation current due to the existence of thick TaO
x
. Leakage currents in BST with the Ir bottom electrode (Ir/BST/IrO
x
/Ir/Si) and BST on Si substrate (Ir/BST/SiO2/Si) were determined by dielectric relaxation characteristics at low electric field and by Poole–Frenkel emission at high electric field. The leakage current in BST with the Ti bottom electrode (Ir/BST/Ti/Si) was dominated by Poole–Frenkel emission at the range of applied field.
Line Narrowing and Injection Locking of F2 Lasers
Authors: Ariga Tatsuya , Hotta Kazuaki
Published: February 2005

To realize an ultranarrow-linewidth and high-output-power F2 laser for next-generation lithography, line narrowing in a F2 laser injection locking system (ILS) that consists of a line-narrowed oscillator and an amplifier with a resonator was investigated. We found out that the time-resolved instantaneous spectrum of the oscillator laser pulse narrows from a start time of discharge and scarcely depends on laser pulse shape. Furthermore, the spectral shape of the ILS is locked to the instantaneous spectral shape of the line-narrowed injection laser when the amplifier discharge starts. We first realized a F2 laser with a linewidth (FWHM) below 0.2 pm and a pulse energy of more than 5 mJ (25 W at 5 kHz repetition rate).
Red-Emitting Phosphor Particles with Spherical Shape, Dense Morphology, and High Luminescent Efficiency under Ultraviolet
Authors: Kang Yun Chan , Roh Hyun Sook , Park Seung Bin , Jung Kyeong Youl
Published: February 2005

Gd2O3:Eu phosphor particles of spherical shape, filled morphology, and high brightness were prepared by large-scale spray pyrolysis. The morphology control of Gd2O3:Eu particles was attempted by adding organic precursors in a spray solution. The influence of chain length of organic additives and introduction of esterification reaction within the droplet on the morphological and luminescent characteristics of Gd2O3:Eu particles was studied. The particles prepared from aqueous solution with no organic additive showed the hollow and porous shell structure and poor brightness, while those particles prepared from solutions with only polyethylene glycol (PEG) exhibited relatively filled structure and high brightness. The longer the chain length of added PEG is, the better morphological and luminescence characteristics the particles showed. The introduction of esterification reaction within the droplet by adding citric acid (CA) and ethylene glycol (EG) or PEG with various molecular weight enhanced the morphological characteristics and significantly improved photoluminescence characteristics regardless of chain length of PEG. The particles prepared from solution containing 0.1 M CA and 0.1 M PEG (M.W. 1500) showed the maximum photoluminescence intensity, which was 148% that of commercial product.
Micro/Millimeter-Wave Generation with Injection-Locked Four-Wave-Mixing Conjugate Modes in a Semiconductor Laser
Authors: Kim Ajung , Seo Young-Kwang
Published: February 2005

A novel method of optical generation of micro/millimeter-wave signals using directly modulated semiconductor lasers is suggested. The sideband modes and the four-wave-mixing conjugate modes in the semiconductor laser are injection-locked by the simple control of the applied modulation power. The signals at 15 GHz with a phase noise level of -96 dBc/Hz at an offset frequency of 100 kHz and signals at 30 GHz with phase noise of -81 dBc/Hz at 100 kHz offset were experimentally obtained.
Spatial Frequency Filtering Characteristics of Three-Phase and Two-Phase Two-Dimensional Gratings
Authors: Go Chun-Soo , Lim Sungwoo , Oh Yong-Ho , Lee Jai-Cheol
Published: February 2005

Spatial frequency filtering by three phase and two phase gratings was theoretically analyzed. The 3-phase grating is a two-dimensional extrapolation of a one-dimensional binary phase grating, and the two phase grating has a phase structure which is simplified into two phases. Their optical transfer functions (OTF) were derived from the Fourier transform of their Fraunhofer diffraction patterns for various phase steps and widths. The most remarkable point is that their on-axis OTF graphs consist of only straight-line segments. Since this graph exhibits a trend for the changes in phase difference and width, we can express the on-axis OTF as an analytic function. By expanding in a Fourier series, the analytic function is proved to be the OTF of these gratings with arbitrary phase difference and width. We also proved that the two types of gratings have the same on-axis OTF graph.
Electronic Structure in the Band-Gap Region of Protonic Conductor SrZr0.90Y0.10O3-δ
Authors: Higuchi Tohru , Matsumoto Hiroshige , Shimura Tetsuo , Yashiro Keiji , Kawada Tatsuya , Mizusaki Junichiro , Shin Shik , Tsukamoto Takeyo
Published: February 2005

The electronic structure in the band-gap region of protonic conductor SrZr0.90Y0.10O3-δ was studied by soft-X-ray absorption spectroscopy (XAS). The O 1s XAS spectrum of air-annealed SrZr0.90Y0.10O3-δ exhibits three distinct features, namely, the holes on top of the valence band, acceptor-induced level just above the Fermi level and Zr 4d defect-induced level at the bottom of the conduction band, which are lower in the O 1s XAS spectrum of wet-annealed SrZr0.90Y0.10O3-δ. These findings directly indicate that the doped hydrogen compensates the presence of the holes.
Picosecond Time-Resolved X-ray Diffraction from a Laser-Shocked Germanium Crystal above Hugoniot Elastic Limit
Authors: Nakamura Kazutaka G. , Kawano Hidetaka , Kishimura Hiroaki , Okano Yasuhisa , Hironaka Yoichiro , Kondo Ken-ichi
Published: February 2005

Picosecond time-resolved X-ray diffraction has been performed on a 300-ps laser-irradiated germanium crystal at 1.2 GW/cm2. Lattice deformation due to shock compression and the propagation of shock waves are directly observed. The observed lattice compression is 4.3% at maximum, which is higher than that at the Hugoniot elastic limit (HEL). The data suggest that the germanium-crystal lattice behaves elastically under shock compression at 7.5 GPa (above HEL) for 27 ps.
Deposition and Characterization of Low-Stress Plasma Enhanced Chemical Vapor Deposition of Tetraethoxysilane Oxide for Micro-Electro-Mechanical-Systems Applications
Authors: Chang Chin-Piao , Wang Yeong-Shing , Huang Ruey-Shing
Published: February 2005

Micro-electro-mechanical systems (MEMS) often use insulated suspended microstructures such as cantilever beams, bridges and membranes for supporting the functional active part of devices. Moreover, these structures are themselves functional devices. In this paper we report a comprehensive study of low-stress plasma-enhanced chemical vapor deposition (PECVD) tetraethoxysilane (TEOS) oxide with respect to the relationship of its deposition process parameters with its properties after deposition such as stress, deposition rate and etching rate in buffered oxide etchant (BOE) or N2H4 silicon etchant. The effect of annealing on the oxide stress is also studied. Low-stress, low-temperature oxides which are resistant to N2H4 silicon micromachining etching were obtained and demonstrated in the fabrication of long and thin cantilever beams. The same technology can also be used for the deposition of thick oxides as a sacrificial layer in MEMS applications.
Single-Molecule Force Microscopy of Circularly Permuted Green Fluorescent Protein
Authors: Wang Tong , Nakajima Ken , Kogure Takako , Yokokawa Shinobu , Miyawaki Atsushi , Hara Masahiko
Published: February 2005

We introduced new termini on surface loops of green fluorescent protein (GFP) by linking the original ones. The mechanical properties of two circularly permuted GFPs (cpGFPs) were examined by atomic force microscopy (AFM) and compared with those of the base GFPs. The unfolding results revealed different levels of the reduced mechanical stability of cpGFPs, and these levels were related to the proximity of the newly introduced termini to the central `β-can'.
In Situ Measurements of Etching Species in SF6 Microwave Downstream Plasma by Ion Attachment Mass Spectroscopy
Authors: Fujiwara Kazuya , Shindo Haruo
Published: February 2005

In situ measurements of etching species in a SF6 downstream plasma are performed by employing a new type of mass spectrometer, the Li ion attachment mass spectrometer. Since the problem of fragment ion generation is less important in this type of mass spectrometer, the etching species can be directly detected. In particular, the etching product SiF4 is detected with the addition of Li+, not in the form of SiF3
+ which is usually detected using a conventional mass spectrometer employing electron impact ionization. Another new finding is that the F radical is the only etching species measured with the same level under two conditions, with and without a silicon substrate.
Combinatorial Ion Implantation Techniques Application to Optical Characteristics of ZnO
Authors: Sakaguchi Isao , Hishita Syunichi , Haneda Hajime
Published: February 2005

We report on the application of combinatorial ion implantation techniques such as the moving mask system and the digital scanning system. The combinatorial library formed by ion implantation was used to optimize the green light emission from ZnO thin films.
Operational Performance of A0-mode Lamb Wave Interdigital Transducers Under Water-Loaded Condition
Authors: Fujita Takeshi , Toda Kohji
Published: February 2005

The operational performance of an A0-mode Lamb wave interdigital transducer is described in a delay line structure. The delay line is composed of two interdigital transducers (IDTs) on a thin piezoelectric ceramic plate, under the air- or water-loaded condition. The A0-mode Lamb wave device has two frequency ranges in the forms of nonleaky and leaky Lamb waves. The boundary frequency is related to the longitudinal wave velocity in water. The basic performance of the A0-mode delay line is presented with measured results in the vicinity of the transition region, where the A0-mode Lamb wave velocity is near the longitudinal wave velocity in water. The A0-mode IDT operates efficiently as an underwater transducer with a shallow radiation angle in the operation region as the leaky wave.
Preparation and Magnetotransport Properties of Alpha-Fe Nanoparticles Dispersed in AlN Granular Films
Authors: Kawaai Yumi , Yamada Atsushi , Takeda Takashi , Kikkawa Shinichi
Published: February 2005

The structure and magnetotransport properties of alpha-Fe (hereafter denote as α-Fe) nanoparticles in reactively cosputter-deposited Al1-x
Fe
x
N films (0.18≤x≤0.91) were studied after their annealing. α-Fe-dispersed crystalline AlN films were obtained by annealing in the temperature range between 300°C and 500°C in hydrogen. A magnetoresistance of 0.82% at room temperature was observed on the granular film annealed at 400°C. This value increased to 2.16% at 77 K.
Long-Period Waveguide Gratings
Authors: Chiang K. S. , Lor K. P. , Liu Q. , Chow C. K. , Chu Y. M. , Chan H. P.
Published: February 2005

In this paper, we review our research efforts in the development of long-period waveguide gratings (LPWGs). We describe LPWGs fabricated in slab and channel waveguides with polymer and glass by conventional photolithography and reactive ion etching to demonstrate the flexibility of the technology, which leads to many advantages of LPWGs, compared with long-period fiber gratings. In particular, we show that an LPWG can function as a widely tunable filter and it is possible to control its wavelength tunability and polarization sensitivity by controlling the dimensions of the waveguide cladding. We also present an LPWG written in a polymer-clad waveguide by a UV technique. Furthermore, we illustrate experimentally the principle of light coupling among an array of parallel waveguides with identical LPWGs. LPWGs can serve as building blocks for the realization of a wide range of integrated optic devices.
Integration of Microoptics in Bio-Micro-Electro-Mechanical Systems towards Micro-Total-Analysis Systems
Authors: Camou Serge , Tixier-Mita Agnès , Fujita Hiroyuki , Fujii Teruo
Published: February 2005

In this article we present how the integration of optics into bio-microsystems can significantly enhance the performance of devices. In the field of micro-electro-mechanical systems (MEMSs), the recent progress of semiconductor technologies has led to the fabrication of devices down to the biological cell scale and to the study of specimens up to the molecular level. By combining these microtools with optical detection, new fields of research have been opened. In particular optical detection performed inside micro-fluidic systems has shown to have various applications that take advantage of both fields. As a consequence a new concept of a miniature, autonomous and integrated laboratory, called a “lab-on-chip” or “micro-total-analysis system” (µ-TAS), has emerged recently. In this field, many studies have been carried out to integrate all elements for the optical detection of substances in micro-fluidic devices. An overview of this field of research gives an idea of its challenges and promises.
Quantization Error Reduction in the Measurement of Fourier Intensity for Phase Retrieval
Authors: Yang Shiyuan , Takajo Hiroaki
Published: February 2005

The quantization error in the measurement of Fourier intensity for phase retrieval is discussed and a multispectra method is proposed to reduce this error. The Fourier modulus used for phase retrieval is usually obtained by measuring Fourier intensity with a digital device. Therefore, quantization error in the measurement of Fourier intensity leads to an error in the reconstructed object when iterative Fourier transform algorithms are used. The multispectra method uses several Fourier intensity distributions for a number of measurement ranges to generate a Fourier intensity distribution with a low quantization error. Simulations show that the multispectra method is effective in retrieving objects with real or complex distributions when the iterative hybrid input-output algorithm (HIO) is used.
Investigation of Photonic Crystals with a Low In-Plane Index Contrast
Authors: Augustin M. , Iliew R. , Fuchs H.-J. , Peschel U. , Kley E.-B. , Nolte S. , Lederer F. , Tünnermann A.
Published: February 2005

The investigation of photonic crystal waveguides and bends realized in glass-like amorphous materials has been performed theoretically and experimentally. Efficient photonic crystal waveguide bends with transmissions up to 75% per bend and low loss photonic crystal waveguides with propagation losses as low as 1.7 dB/mm were realized.
Nanostructured Organic/Inorganic Composites as Transparent Materials for Optical Components
Authors: Mataki Hiroshi , Yamaki Shigeru , Fukui Toshimi
Published: February 2005

It has been found that nanostructured organic/inorganic composites, in which nanometer-sized inorganic inclusions are uniformly dispersed in and fixed to a matrix polymer, can modify the property of the matrix polymer while suppressing Rayleigh scattering to exhibit preferable transparency. Rather, when compared with the transparency of a matrix polymer alone, the composite could exhibit better transparency as the content of inorganic inclusions increases. Furthermore, because the refractive index of the composite agrees well with the Maxwell-Garnett model, it is suggested that synergetic effects obtained by the bulk properties of both the matrix polymer and inorganic inclusions can be exhibited. Such a potential has been verified by applying the composites to optical waveguides and optically athermal materials.
Optical Memory with Store/Forward Using All-Optical Triode Based on Tandem Wavelength Converter in Reflective Semiconductor Optical Amplifiers
Authors: Maeda Yoshinobu
Published: February 2005

An all-optical triode based on a tandem wavelength converter was realized using cross-gain modulation in two reflective InGaAsP/InP semiconductor optical amplifiers. The reflective semiconductor optical amplifiers were utilized to improve output extinction ratio as well as logic operation output performance. The output signal power and extinction ratio from the first stage wavelength conversion were critical to the achievement of all-optical logic AND operation. The optical output power at the 1555 nm wavelength could be varied from 0.1 to 3.3 mW by a control beam which had the same wavelength. The output-input gain parameter can be changed from 0 to 1.6 when the average control power is altered from 0 to 48 µW. An optical memory with store/forward functions was demonstrated using the optical triode and a feedback system of the fiber.
Optical Chaotic Communication Using Laser Diode Transmitter/Receiver Array
Authors: Ebisawa Satoshi , Komatsu Shinichi
Published: February 2005

We propose a new scheme of digital chaotic communication using the array of transmitter/receiver that consists of two self-pulsating laser diodes (LDs), i.e., a receiver LD and a transmitter LD. Part of the output of a transmitter LD is injected into the corresponding receiver LD that receives a chaotically encoded signal. A neutral density (ND) filter is placed after each transmitter LD to control the amount of light transmitted to and then injected into the corresponding receiver LD. According to the amount of the transmitter output which is injected into the receiver LD, two kinds of chaotic states with different Lyapunov exponents are induced in the receiver LD, and they are utilized to represent a binary digit. In addition, the distribution of the coupling factor between transmitter and receiver is used as a “key”. Only the proper receiver who has been previously given the “key” is able to choose an appropriate threshold of the Lyapunov exponent calculated from the detected chaotic signal that is necessary to decipher each binary bit and to decode finally the entire message. By numerically analyzing the bit error rate, particularly its dependence on the error of the optical confinement coefficient as well as on that of the injection current, we confirmed that the present scheme can provide superior security compared to the conventional chaotic masking scheme.
Characteristics of Indium Bump for Flip-Chip Bonding Used in Polymeric-Waveguide-Integrated Optical Interconnection Systems
Authors: Chu Kun-Mo , Lee Jung-Sub , Cho Han Seo , Rho Byung Sup , Park Hyo-Hoon , Jeon Duk Young
Published: February 2005

We have flip-chip-bonded vertical-cavity surface-emitting laser (VCSEL) arrays on polymeric-waveguide-integrated optical interconnection systems. Using indium solder bumps, thermal damage to the polymeric waveguide can be avoided. Fracture occurs between the indium solder bumps and the VCSEL chip pad during the die shear test. It is inferred that both the low bonding temperature and the oxide layer formed on the surface of the indium solder prevent the bump from interacting with the chip pad. To reveal the microstructures of the joints between the bump and the chip pad, several specimens are cut into cross sections and polished. Scanning electron microscopy (SEM) with an energy dispersive X-ray (EDX) spectroscopic system is used to examine the microstructures and analyze the element compositions. Also, the optoelectronic characteristics of VCSEL arrays that were flip-chip-bonded under different bonding conditions are compared by current-voltage (I-V) and light-current (L-I) inspection.
Fluid Dynamic Assembly of Semiconductor Blocks for Heterogeneous Integration
Authors: Soga Ikuo , Ohno Yutaka , Kishimoto Shigeru , Maezawa Koichi , Mizutani Takashi
Published: February 2005

We have studied the fluidic assembly (FA) technique for heterogeneous integration. In this technique, device blocks, the size of which ranges from a few tens of microns to a few hundreds of microns, are arranged onto another material substrate in fluid. Here, we propose a novel technique to improve FA, called fluid dynamic assembly (FDA), which employs fluid dynamic effects. In the FDA, a special structure is fabricated on the block, which stabilizes the posture of the blocks falling in the fluid. This can be used to control the face of assembled blocks. In this paper, the feasibility of the FDA is discussed on the basis of fluid dynamic simulation and experiments. The numerical simulations revealed that the face control can be carried out for the block having ringlike (O-type) structures on it. Then we carried out the FDA experiments using thin disk-shaped GaAs blocks with O-type structure, and demonstrated an 87% face control ratio for the blocks with 7.5-µm-thick structure. Moreover, the less symmetric C-type structure was examined, and demonstrated even a high face control ratio of 96%.
Carrier Transport in Polycrystalline Silicon Thin Film Solar Cells Grown on a Highly Textured Structure
Authors: Honda Shinya , Takakura Hideyuki , Hamakawa Yoshihiro , Muhida Riza , Kawamura Tomohiro , Harano Tomokazu , Toyama Toshihiko , Okamoto Hiroaki
Published: February 2005

Photovoltaic performance of polycrystalline silicon (poly-Si) thin film solar cells deposited by plasma enhanced chemical vapor deposition at a low temperature of ∼200°C have been investigated as a function of surface structures of textured substrates, which are needed for enhancing the light trapping effect. With increasing surface roughness of the substrate, the light trapping effect is increased, while the photovoltaic performance is decreased because the carrier transport in the poly-Si photovoltaic layer depends on the poly-Si microstructures which are significantly deteriorated by the surface texture. To quantify the effect of the surface roughness, a simple one-dimensional simulation model consisting of two regions, i.e., the initial growth region near the substrate with poor crystallinity and the postgrowth region, is proposed for the photovoltaic performance of the poly-Si thin film solar cells with different poly-Si layer thicknesses. The simulation result reveals that the carrier transport in the initial growth region more strongly depends on the surface roughness compared with that in the postgrowth region.
High-Performance SiOF Film Fabricated Using a Dual-Frequency-Plasma Chemical Vapor Deposition system
Authors: Yoda Takashi , Fujita Keiji , Miyajima Hideshi , Nakata Rempei , Nishiyama Yukio , Nakasaki Yasushi , Hayasaka Nobuo
Published: February 2005

With the use of a newly developed dual-frequency-plasma chemical vapor deposition (DFP-CVD) system, an advanced SiOF film of k = 3.4, which exhibits excellent resistance for moisture absorption, was developed. The physical and chemical properties of the SiOF film were compared to those of typical SiOF films deposited by both conventional high-density-plasma CVD (HDP-CVD) and plasma-enhanced CVD (PE-CVD) systems, with the same k value. The DFP-CVD SiOF film appears to be significantly superior to the HDP-CVD SiOF film, as revealed by the following results. The moisture absorption rate measured by thermal desorption spectroscopy (TDS) (after 4 days of air exposure) is about 5 times lower, the hardness was 1.8 times higher, and the hygroscopicity (after 1 hour of boiling) was 2.6 times lower. These results confirm that the DFP-CVD SiOF film is applicable to Al and Cu interconnect structures for devices of the 130 nm scale and beyond.
M–H Loop Slope and Recording Properties of Perpendicular Media
Authors: Nakamura Atsushi , Igarashi Masukazu , Hara Miki , Sugita Yutaka
Published: February 2005

The slopes of the M–H loop of perpendicular magnetic recording media were estimated by micro-magnetic simulation for various inter-grain exchange couplings, grain aspect ratios and inter-grain spacings. The slope of the M–H loop depends not only on inter-grain exchange coupling but also on grain aspect ratio and inter-grain spacing. The simulation revealed that the required head field decreases with increasing inter-grain exchange coupling. The optimum value of the slope was slightly larger than 1.0 for compromising resolution and SNR by changing the inter-grain exchange coupling. The simulation results also indicated that the inter-grain spacing improves both resolution and SNR.