bluuebunny/crossref_metadata_2025 huggingface dataset:
Bending Effect of Organic Field-Effect Transistors with Polyimide Gate Dielectric Layers
Authors: Sekitani Tsuyoshi , Iba Shingo , Kato Yusaku , Someya Takao
Published: July 2005

We manufactured markedly flexible pentacene field-effect transistors (FETs) on a polyethylenenaphthalate base film with polyimide gate dielectric layers, with a mobility of 0.3 cm2/Vs and an on/off ratio of 105. The electric performance of DC current–voltage characteristics was measured by applying compressive and tensile strains while reducing the bending radius down to 3 mm. It was found that the compressive strain leads to an increase in mobility of 10% induced by the change in strain of up to 1.4±0.1%, although the tensile strain leads to a decrease in mobility of 10%. To elucidate the origin of the enhancement of mobility under the compressive strain, we also investigated the strain dependence of capacitance–voltage characteristics for a pentacene channel layer, and almost no change was observed. Our results suggest that the strains markedly affect the spacing between pentacene molecules rather than the number of induced carriers.
Enhanced Luminance Efficiency of Organic Light-Emitting Diodes with Two-Dimensional Photonic Crystals
Authors: Kitamura Masatoshi , Iwamoto Satoshi , Arakawa Yasuhiko
Published: July 2005

Organic light-emitting diodes (OLEDs) with two-dimensional photonic crystal were fabricated to improve their light-extraction efficiency. The electroluminescence (EL) spectra from these OLEDs depended on the lattice constant of the photonic crystal. The relationship between the EL spectra and the lattice constant was investigated. On the basis of this investigation, a lattice constant was optimized to obtain a large improvement in luminance. In addition, OLEDs doped with coumarin 6 provided a larger improvement in luminance than nondoped OLEDs. The coumarin 6 doped OLED with the optimized lattice constant provided improvements of 62% in luminance in the normal direction and 25% in spatially integrated EL intensity.
Silicon-Based Optical Thin-Film Biosensor Array for Real-time Measurements of Biomolecular Interaction
Authors: Fujimura Toru , Takenaka Kei , Goto Yasushi
Published: July 2005

Real-time multi-channel measurements of protein-protein interaction in 1–100 µg/ml antibody solution samples were demonstrated using a reflectometric interference spectroscopy (RIfS) based silicon biochip. Since titanium-oxide film, whose refractive index is 2.2, was chosen for the interference layer of RIfS on the silicon substrate, the layer interference was enhanced in aqueous solutions and the protein-protein interaction on the film could be measured as a shift in interference-peak position in the reflection spectra. To estimate the sensitivity of the sensing system using the RIfS sensor, we simulated the reflection spectra of the biochip. From these results, it was shown that a 0.01-nm shift in the interference-peak position corresponds to a binding amount of protein of approximately 10 pg/mm2. According to this result, the sensitivity of our sensor was estimated to be in the order of 10 pg/mm2 by comparing the simulated and experimental results.
Electronic Structure of Protonic Conductor SrTi0.98Sc0.02O3 Probed by Soft-X-ray Spectroscopy
Authors: Higuchi Tohru , Yamaguchi Shu , Shin Shik , Hattori Takeshi , Tsukamoto Takeyo
Published: July 2005

The electronic structure of a protonic conductor Sc-doped SrTiO3 (SrTi0.98Sc0.02O3) single crystal has been studied by photoemission spectroscopy and X-ray absorption spectroscopy. The holes and acceptor level are observed at the top of the valence band and just above the Fermi level (E
F), respectively, in dried SrTi0.98Sc0.02O3. Their intensities are lower in H2-annealed SrTi0.98Sc0.02O3. The E
F of H2-annealed SrTi0.98Sc0.02O3 shifts to the conduction band side by approximately 0.4 eV compared with that of a dried sample. These findings indicate that the doped hydrogen compensates the existence of the holes.
DNA Analysis Chip Based on Field-Effect Transistors
Authors: Sakata Toshiya , Kamahori Masao , Miyahara Yuji
Published: July 2005

We have been developing a genetic field-effect transistor (FET) based on the potentiometric detection of hybridization and intercalation on the Si3N4gate insulator. In this study, we demonstrated the detection of charge density change as a result of hybridization and intercalation using genetic FETs. Since the electrical output signal is obtained with the genetic FET without any labeling reagent, as compared with the conventional fluorescence-based DNA chips, the genetic FET platform is suitable for a simple and inexpensive system for genetic analysis in clinical diagnostics.
Compact Triangulation Sensor Array Constructed by Wafer Bending
Authors: Endou Satoshi , Ishimori Masahiro , Sasaki Minoru , Hane Kazuhiro
Published: July 2005

An optical triangulation distance sensor array was constructed by bending a silicon wafer. Since bending is the final process in the fabrication sequence, planar photolithography can be included in the fabrication sequence. The elements on the Si wafer are all prealigned under a planar condition, and the position-sensitive detector, mirror, and alignment pit for the collimation ball lens are prepared before bending the wafer. The size of the optical bench produced by the sensor substrate is 1.4 mm deep. By batch fabrication, a 2×2 sensor array was produced. A dynamic range of 4 mm and a noise level of ±1% was confirmed by testing.
In Vivo Batteryless Wireless Communication System for Bio-MEMS Sensors
Authors: Yamada Tomohiro , Uezono Takumi , Okada Kenichi , Masu Kazuya , Oki Akio , Horiike Yasuhiro
Published: July 2005

We propose a batteryless wireless communication system for in vivo healthcare chips. The system uses inductive coupling at 13.56 MHz with internal and external coils, and employs pulse interval modulation (PIM) to endure the large attenuation in the human body. A wireless communication circuit is presented in this paper, and 16 mV of output voltage can be obtained at the external receiver. The antenna coil structure is investigated, and it is found that a tablet structure is suitable for the proposed system.
Degradation in Low-Temperature Poly-Si Thin Film Transistors Depending on Grain Boundaries
Authors: Uraoka Yukiharu , Kitajima Koji , Kirimura Hiroshi , Yano Hiroshi , Hatayama Tomoaki , Fuyuki Takashi
Published: July 2005

The low-temperature poly-Si process is one of the most promising technologies for realizing new displays such as system on panel. For this purpose, an improvement in the reliability, as well as promoting the electric performance is very important. In this work, we attempted to study the degradation in TFTs by hot-carrier and joule heating effects focusing on the crystallinity of poly-Si thin films. For the evaluation of the hot-carrier effect, we found that the grain size dependence of hot-carrier degradation differed between the cases of DC and AC stresses in both n-channel and p-channel thin-film transistors (TFTs). The difference in the grain size dependencies is attributed to the difference between DC and DC stresses in degradation mechanism. For the evaluation of thermal degradation, a universal relationship between the temperature and the amount of the voltage shift in n-channel TFT was observed independent of the crystallinity of the films used. It was considered that electron injection into gate oxides is one of the dominant causes of thermal degradation.
Role of Boron Atoms on Fluorine Diffusion under Various Stages of Annealing
Authors: Tachi Masayuki , Tsuji Hiroshi , Furuhashi Masayuki , Taniguchi Kenji
Published: July 2005

We demonstrate the role of boron atoms on fluorine diffusion through experiments on the preamorphized samples uniformly doped with boron under three stages of annealing. In the preannealing stage, during and after implantation at room temperature, fluorine diffusion is significantly retarded by the high background boron concentrations. Similarly, in the second stage of annealing, at 550°C, the substrate condition remains amorphous and the fluorine migration is suppressed in the presence of boron. We suggest that negatively charged fluorine atoms are trapped at dangling bonds positively charged by boron atoms by the Coulomb attractive force. In the third stage of annealing, at 800°C, fluorine atoms migrate anomalously and accumulate at the 0.8 projected range of fluorine only in the samples doped with boron. This result suggests that the background boron enhances fluorine migration by the dissolution of small defects or the prevention of the formation of small defects in the recrystallized region, resulting in fluorine accumulation at the damaged area associated with the implantations.
Vertical Electrode GaN-Based Light-Emitting Diode Fabricated by Selective Wet Etching Technique
Authors: Kim Seong-Jin
Published: July 2005

In order to improve the device performance and productivity, a sapphire-etched vertical-electrode nitride semiconductor (SEVENS) light-emitting diode (LED) is fabricated by a selective wet-etching technique. The sapphire substrate is removed by chemical wet etching and transferred to a conducting Si substrate with a reflector metal. The SEVENS-LED exhibits excellent device performance. Integral light-output power is approximately 3.5 mW at a 20 mA junction current, which indicates a 6.6% external quantum efficiency (EQE). The light-output power was linearly increased with increasing junction current, and the peak wavelength was saturated even with a higher junction current. The enhanced performance of the SEVENS-LED is attributed to changing the lateral electrode to a vertical electrode and transferring a sapphire substrate to a Si receptor with a reflector metal. The SEVENS-LED technique is anticipated to be useful for improving the performance of GaN-based LEDs for future solid-state general illumination applications.
Precise Determination of Thermal Effect on the Optical Properties of Liquid Crystal Devices Using the Fabry–Perot Interferometry
Authors: Kim Hak-Rin , Jang Eunje , Im Jaehyun , Lee Sin-Doo
Published: July 2005

The thermal effect on the optical properties of liquid crystal (LC) devices was investigated using the Fabry–Perot (FP) Interferometry From thermal variations of the resonant modes in the LC-filled FP cell, the temperature-dependence of the phase retardation and the cell gap variations were precisely measured. Experimental results showed that both the thermal variations of the cell gap and the refractive index variations of the LC with temperature play a critical role in the optical performances of the LC devices.
Low-Temperature Formation of Epitaxial NiSi2 Layers with Solid-Phase Reaction in Ni/Ti/Si(001) Systems
Authors: Nakatsuka Osamu , Okubo Kazuya , Tsuchiya Yoshinori , Sakai Akira , Zaima Shigeaki , Yasuda Yukio
Published: July 2005

The solid-phase epitaxial growth of NiSi2 in Ni/Ti/Si systems has been investigated. Continuous epitaxial NiSi2 layers consisting of pyramidal domains with {111} facets at the Ni-silicide/Si interface can be formed by annealing at a temperature (350°C) lower than that for conventional Ni/Si systems. This NiSi2 layer is transformed to a uniform epitaxial NiSi2 layer with an atomically flat silicide/Si interface by additional annealing at 850°C, while the {111} facets at the NiSi2/Si interface remains in the Ni/Si system under the same annealing conditions. Moreover, the epitaxial NiSi2 layer formed at 350°C exhibits a high thermal robustness even after annealing at higher than 750°C, in contrast to the polycrystalline NiSi layer.
Concise Analytical Threshold Voltage Model for Cylindrical Fully Depleted Surrounding-Gate Metal–Oxide–Semiconductor Field Effect Transistors
Authors: Chiang Te-Kuang
Published: July 2005

On a basis of a quasi-2D potential analysis using the effective conducting path effect (ECPE), a concise analytical model for the threshold voltage in cylindrical fully depleted surrounding-gate (SG) metal–oxide–semiconductor field effect transistors (MOSFETs) is derived. With various depths of the effective conducting path, the minimum channel potential Φ
d
eff,min induced by ECPE is used to develop the threshold voltage model. Besides the increased depth of the effective conducting path, a thin silicon body and a decreased oxide thickness can reduce threshold voltage roll-off simultaneously. It is also observed that the threshold voltage shift depends on the scaling factor. A large scaling factor is preferred to alleviate threshold voltage degradation. This paper not only provides a simple analytical model but also offers an efficient analysis of the threshold voltage of the short-channel cylindrical fully depleted SG MOSFETs.
Studies on the Influences of i-GaN, n-GaN, p-GaN and InGaN Cap Layers in AlGaN/GaN High-Electron-Mobility Transistors
Authors: Arulkumaran Subramaniam , Egawa Takashi , Ishikawa Hiroyasu
Published: July 2005

Systematic studies were performed on the influence of different cap layers of i-GaN, n-GaN, p-GaN and InGaN on AlGaN/GaN high-electron-mobility transistors (HEMTs) grown on sapphire by metal organic chemical vapor deposition. The decrease of maximum extrinsic transconductance (g
m) and maximum drain current density (I
Dmax) values agrees with the product values of two-dimensional electron gas (2DEG) mobility (µH) and 2DEG sheet concentration (n
s) of AlGaN/GaN HEMT structures. An improved Schottky barrier height with low surface roughness has been observed in AlGaN/GaN HEMT structure with i-GaN and n-GaN cap layers. The HEMTs with i-GaN cap layer exhibited low gate leakage current with high breakdown voltage among the other HEMTs. Though the HEMTs with n-GaN cap layer and without cap layers exhibited good µH, g
m, I
Dmax values, the ac characteristics are not up to the extent of HEMTs with i-GaN cap layer. All the devices except the HEMTs with InGaN cap layers were operational even up to the measurement temperature of 350°C. The HEMTs with i-GaN cap layer exhibited collapse-free I
DS–V
DS characteristics with small I
D hysteresis width variations among the other HEMTs. The observation of small threshold voltage variation, small drain current hysteresis width and small white light illumination effects confirms the existence of small trapping effects in HEMTs with i-GaN cap layers. Only one thermally activated trap level at -0.161 eV was observed on AlGaN/GaN HEMTs with i-GaN cap layer. However, each of the three trap levels has been observed in HEMTs with other cap layers and HEMTs without cap layers. From this, it is concluded that the collapse-related traps are screened/passivated from two-dimensional electron gas by the addition of thin i-GaN cap layer on AlGaN/GaN HEMTs. The cap layer i-GaN (3 nm) is a promising candidate to get collapse-free AlGaN/GaN HEMTs.
Variable Optimization for Chemical Mechanical Polishing
Authors: Liao Shan-Hui , Fu Ming-Nan , Hou Kung-Hsu , Li Ching-Chung
Published: July 2005

Slurry is often used in chemical mechanical polishing (CMP) as a polishing additive. When a spinning wafer carrier applies a pressure on a wafer toward a pad, the wafer carrier in the polishing process will drag the slurry sputtered on the pad into the narrow gap between the wafer and the pad. In this study, we determine the features of the slurry transports between the pad and the wafer by conducting experiments to develop a method of decreasing the nonuniformity of the polishing process. In this study, we apply experimental design methods to the statistical analysis of chemical mechanical polishing in manufacturing for each operation parameter. The four design parameters of CMP include the rotation speed of the pad, injection position, the rotation speed of the wafer, and slurry mass flow. The procedure for optimization search for the minimum object value and its corresponding input set values was validated and compared with that for the same search for the original experimental data. Performance indexes were improved. The procedure provided an easy and feasible approach to CMP system design.
Low-Damage Damascene Patterning Using Porous Inorganic Low-Dielectric-Constant Materials
Authors: Yonekura Kazumasa , Goto Kinya , Matsuura Masazumi , Fujiwara Nobuo , Tsujimoto Kazunori
Published: July 2005

The degradation of porous low-dielectric-constant (low-k) materials, such as porous methyl silsesquioxane (MSQ) and porous chemical-vapor-deposited SiOCH films, by damascene etch and ash processes has been investigated. The influence of etch damage becomes relatively stronger as ash damage improves. The etch damage to porous low-k dielectric is found particularly at the sidewall of the isolated lines. By investigating the influence of etch conditions on the damage, it is found that O2 and Ar addition causes large sidewall damage. O2-added etch condition, as well as the O2 ash process, produces oxygen radicals, which extract CH3 groups from porous low-k films. On the other hand, Ar plasma does not efficiently extract CH3 groups differently from O2 plasma, but it changes the bonding states of CH3 groups and causes H2O adsorption. This change in film characteristics increases dielectric constant. Finally, we successfully achieved low-damage dual damascene patterning using a porous SiOCH material whose dielectric constant is 2.2.
Effect of Dopants on Microwave Dielectric Properties of Ba(Zn1/3Ta2/3)O3 Ceramics
Authors: Varma Manoj Raama , Raghunandan Resmi , Sebastian Mailadil Thomas
Published: July 2005

Ba(Zn1/3Ta2/3)O3 (BZT) has been prepared with various amounts of different dopants such as oxides of divalent, trivalent, tetravalent, pentavalent and hexavalent elements. Effect of these dopants on microwave dielectric properties of BZT is investigated. Some of the dopants are found to increase quality factor (Q). Most of the dopants increase the temperature coefficient of resonant frequency (τ
f
). Annealing undoped BZT increased the order parameter and quality factor. Small amounts of dopants such as that of oxides of Zr, Ga, Cr, Ce, Sn, In, Mn and Sb increased the quality factor. The doped ions substitute for the ordered B ions decreasing the order parameter. Annealing Ga and In doped BZT decreased the Q factor where as it increased for Zr, Cr, Ce, Sn, Mn, Sb doped samples. Doping BZT with Zr, Ga, Cr, Ce, Sn, In, Mn, Sb decreased the order parameter but at the same time increased the quality factor indicating that order parameter alone is a poor indicator of quality factor. The quality factor is found to depend on the dopant ionic radii and dopant concentration. The quality factor increased when the ionic radius of the dopant is close to the ionic radius of the B site ions Zn or Ta.
Effect of Ground-Wall Structure in Capacitive Fingerprint Sensor on Electrostatic Discharge Tolerance
Authors: Shigematsu Satoshi , Tanabe Yasuyuki , Shimoyama Nobuhiro , Morimura Hiroki , Okazaki Yukio , Machida Katsuyuki
Published: July 2005

This paper describes the electrostatic discharge (ESD) tolerance of capacitive fingerprint sensor or sensor/identifier LSIs in which the sensor is stacked on a CMOS LSI. The ground-wall structure that we proposed as a capacitive sensor structure for ESD tolerance was investigated. The contact discharge method was used for the fingerprint sensor ESD test. The dependence of ESD failure voltage on the distance between the sensor surface and the ESD electrode was measured. In the planar-type structure, ESD failure voltage decreased as the electrode approached the sensor surface and reached its minimum when the electrode touched the surface. Results for the ground-wall type show a high ESD tolerance regardless of the distance. Moreover, in the test on the fingerprint sensor and sensor/identifier LSIs, the ground-wall effect was obtained with a high ESD tolerance. In conclusion, it was revealed that fingerprint sensor LSI or the fingerprint sensor/identifier LSI with a ground-wall structure has a high ESD tolerance of more than ±20.0 kV.
Investigation of Terahertz Emission Phenomena of High-Tc Superconductors
Authors: Murakami Hironaru , Tominari Yukihiro , Tonouchi Masayoshi , Uchiyama Tetsuji , Iguchi Ienari , Wang Zhen
Published: July 2005

The c-axis transmission spectra of underdoped Bi2Sr2CaCu2O8+δ (BSCCO) and YBa2Cu3O7-δ (YBCO) thin films were measured in the frequency range from 0.1 to 1.5 THz to investigate the mechanism of terahertz (THz)-pulse emission from high-T
C superconductors (HTSs). The transmission spectra showed different properties depending on both the kind and hole-doping level of HTS thin film. A relatively strong shielding effect was observed for THz waves below the characteristic frequency f
0, which almost corresponds to the cutoff frequency f
c in the THz-wave radiation spectrum. The observed THz-pulse transmission and emission properties are explained by the intrinsic anisotropic characteristic peculiar to each HTS sample. Particularly, the magnitude of the superconducting order parameter that is induced in the insulating barrier layer between CuO2 double layers plays an important role in determining the cutoff frequency f
c.
Frictional and Removal Rate Studies of Silicon Dioxide and Silicon Nitride CMP Using Novel Cerium Dioxide Abrasive Slurries
Authors: Zhuang Yun , King Deanna , Kido Takanori , Philipossian Ara
Published: July 2005

Novel slurries containing cerium dioxide particles as the abrasives were used for silicon dioxide and silicon nitride CMP in this study. Real-time frictional force was measured during polishing. Slurries with varying ceria abrasive concentrations achieved different friction forces during the silicon dioxide and silicon nitride polishing. The effects of the ceria abrasive concentration on the silicon dioxide and silicon nitride removal rates were also investigated. The silicon dioxide removal rates exhibited non-Prestonian behavior, which was attributed to the additives used in the slurries. Being specially formulated for shallow trench isolation (STI) applications, these novel slurries achieved high oxide-to-nitride removal rate selectivities.
Formation of L10-type Ordered FePd Phase in Multilayers Composed of Fe and Pd
Authors: Endo Yasushi , Yamanaka Yuji , Kawamura Yoshio , Yamamoto Masahiko
Published: July 2005

We have investigated the magnetic properties and structure of [Fe (2.50 nm)/Pd (t
Pd nm)]8 multilayers for a series of Pd layer thicknesses in order to study the formation of the L10-type ordered FePd phase in Fe/Pd multilayers as a function of annealing temperature. It is found that the bcc-Fe phase and fcc-Pd phase in the as-deposited Fe/Pd multilayer do not transform to the disordered Fe–Pd phase or L12-type ordered FePd3 phase but transform directly to the L10-type ordered FePd phase with increasing annealing temperature above 673 K for the Pd layer thickness range between 3.00 nm and 3.50 nm. The value of (S
Lattice)2 for a 3.25-nm-thick Pd layer, namely, the degree of order obtained for specific lattice parameters is evaluated to be approximately 0.17 at the annealing temperature of 673 K, and is then enhanced to nearly 1.0 with increasing annealing temperature above 823 K. The formation temperature of the L10-type ordered FePd phase in the Fe/Pd multilayer becomes low. The thickness range of the Pd layer for the formation of the fully L10-type ordered FePd phase in the Fe/Pd multilayer becomes narrow.
Effects of SiO2 Addition on Microstructure and Magnetic Properties of Yttrium Iron Garnet
Authors: Kim Dong-Young , Lee Hong-Yeol , Jun Dong-Suk , Lee Sang-Seog
Published: July 2005

Pore free Yttrium Iron Garnet (YIG) ceramics with high density and low magnetic loss were manufactured by conventional ceramic processing. By small additions of SiO2, pores captured inside grains were effectively eliminated, and the number of pores in grain boundaries was markedly reduced. The density of specimens was 99.6% of the theoretical density. The FMR linewidth of a specimen was 47 Oe, which is comparable to that of other YIG specimens produced by more expensive and elaborate process such as hot pressing. However, adding more than 1 mol% SiO2 deteriorated the sintering characteristics of the YIG specimen. The added SiO2 may segregate at grain boundaries and inhibit the grain growth. As a result, the average grain size and sintered density were reduced in the case of SiO2 addition more than 1 mol%.
Comparison Study of Subsonic and Transonic Mixing in a Multi-Kw Grid-Nozzle Supersonic Chemical Oxygen Iodine Laser
Authors: Vyskubenko Oleg , Sugimoto Daichi , Watanabe Goro , Tei Kazuyoku , Nanri Kenzo , Fujioka Tomoo
Published: July 2005

The present study compares the laser medium properties for subsonic and transonic iodine injection schemes of a multi-kW grid-nozzle supersonic chemical oxygen iodine laser (COIL). Two supersonic nozzles of similar geometry having subsonic or transonic iodine injectors were investigated in the present study. Small signal gain (SSG) and internal cavity temperature (ICT) were experimentally measured as a function of the iodine flow rate and coordinate in the direction of the gas flow. Dissociated fraction of iodine F and the number N of O2(1Δ) molecules consumed for the dissociation of one iodine molecule were estimated by an analytical method, utilizing SSG and ICT as input parameters. Both gain and temperature were measured by diode laser spectroscopy. Pressure broadening of the spectroscopic line of iodine atom was taken into account when calculating the gas temperature in the cavity.
High-Transmittance Phase-Change Media with TiO2 Film for Rewritable Dual-Layer Blu-ray Discs
Authors: Nishihara Takashi , Kojima Rie , Miyagawa Naoyasu , Yamada Noboru
Published: July 2005

We have developed a semitransparent layer structure that is ideally suited to the laser-incident-side (front-side) recording layer of a rewritable dual-layer Blu-ray Disc (BD-RE). A TiO2 top film and a memory film of GeTe–Sb2Te3 characterize this layer structure. The TiO2 film has a large refractive index, which works to increase the transmittance of the entire recording layer to more than 50%. It simultaneously increases the reflectivity contrast, defined by (R
cry-R
amo)/(R
cry+R
amo), where R
cry and R
amo (R
cry>R
amo) are the reflectivities of the optical disc in the crystalline and amorphous parts, respectively. The GeTe–Sb2Te3 memory film has optical constants that are appropriate for balancing the transmittance between the crystalline part (T
cry) and the amorphous part (T
amo) in the laser wavelength region of approximately 405 nm. Our experimental dual-layer disc shows high transmittances of T
cry=51.6% and T
amo=52.0% and a high reflectivity contrast of 0.71 in the laser-incident-side layer. Dynamic examination showed that both recording layers have a good jitter value, satisfying the BD-RE specifications; more specifically, the laser-incident-side layer jitter value is 7.4% (spec.: 8.5%) and the back-side layer jitter value is 6.4% (spec.: 6.5%) through the front-side layer.
Optical Sensing Directional Acoustic Transducer with Grating Diaphragm Using Complementary Metal Oxide Semiconductor Compatible Micromachining Techniques
Authors: Suzuki Kazuhiro , Funaki Hideyuki , Naruse Yujiro
Published: July 2005

In this paper, we present a new directional acoustic transducer using complementary metal oxide semiconductor (CMOS)-micro electro mechanical system (MEMS) micromachining techniques. The diaphragm of the acoustic transducer has a diffraction grating fabricated by the CMOS process requiring only a small number of post processes. The MEMS-based optical acoustic transducer transfers the displacement signal of the diaphragm with a grating pattern to a photodetector, which detects the vibrational displacement of the diaphragm based on changes in optical intensity. The same space conditions for the front and rear surfaces of the diaphragm can be achieved easily in this optical acoustic transducer. This arrangement allows a high directionality without sensitivity for side-on sounds, because the front and rear pressures of the diaphragm are in phase. The directional characteristics of our prototype acoustic transducer were measured, and a high directivity (6 dB attenuation at 30 deg) was confirmed.
Molecular Iodine Spectra and Laser Stabilization by Frequency-Doubled 1534 nm Diode Laser
Authors: Cheng Wang-Yau , Shy Jow-Tsong , Lin Tyson , Chou Che-Chung
Published: July 2005

By using the second harmonic radiation of a 1543 nm diode laser, several predicted rovibronic transitions of molecular iodine were observed for the first time. We demonstrated that the absolute frequency of a 1534 nm external-cavity diode laser could be frequency-stabilized to a 1 MHz instability (for one second averaging time) by locking the frequency of the second harmonic generation to the dense rovibronic spectrum of127I2. Our scheme shows one possible means of generating a frequency grid in the entire wavelength region of optical communications.
Fabrication of Zn-Indiffused LiNbO3 Optical Waveguides Using ZnS as Diffusion Source
Authors: Selvan Jayaraman Senthil , Fujimura Masatoshi , Suhara Toshiaki
Published: July 2005

Fabrication of Zn-indiffused LiNbO3 waveguides using ZnS as a diffusion source is proposed and demonstrated for the first time. Possibility of Zn diffusion into Z-cut LiNbO3 using ZnS was examined. The diffusion in low-pressure atmosphere produced Zn-diffused crystals with a smooth surface. Single-mode waveguiding for transverse magnetic (TM) and transverse electric (TE) modes was achieved at 1.5 µm wavelength in the channel waveguides fabricated by the diffusion of ZnS film at 890°C for 30 min in oxygen at 1 Torr pressure.
Diagnostics for Liquid Samples by Laser-Pumped Photo-Thermal Method
Authors: Kim Changsu , Kubota Toshio , Tsuji Ryusuke , Shiraishi Masatake , Fujii Kan-ichi
Published: July 2005

A laser pumped-thermal lens system as a tool for the measurement of liquid samples was constructed. The clear distinction of three different liquids at the stationary state was demonstrated. An example of the time-course feature at the transient state of diffusion when an impurity droplet was dropped into water was traced, exhibiting a time of about 5 s to the end of diffusion. The intensity of thermal lens signal versus the mixing rate of liquid samples in water at the steady state was measured with good reproducibility.
Transflective Liquid Crystal Display with Single Cell Gap and Single Gamma Curve
Authors: Lim Young Jin , Song Je Hoon , Lee Seung Hee
Published: July 2005

The vertical electric field-driven transflective nematic liquid crystal display with dual orientation has a problem that the voltage-dependent transmittance and reflectance curves do not match each other. Thus a dual driving circuit is required. This study shows that optimization of the surface pretilt angle in the transmittance solves this problem so that the transflective display with a single cell gap and single gamma curve for reflective and transmissive region is possible.
Electron–Phonon Scattering in a Disordered Ti41V41Al18Alloy
Authors: Biswas Debasish , Meikap Ajit Kumar , Chattopadhyay Sukanta Kumar , Chatterjee Sanat Kumar
Published: July 2005

The results of a systematic study of electron–electron interaction and weak localization on Ti41V41Al18alloy are being reported in this work. The results indicate an anomalous resistivity behaviour with variation in temperature that follows aT2variation at high temperature and shows aT1/2variation at low temperature. Attempt has been made to explain this anomalous behaviour of resistivity with the help of the existing theories concerning low temperature physics. The low field magnetoresistivity is described by weak localization theory under strong spin–orbit interaction. The electron–phonon scattering rate obeys aT4dependence, which is interpreted by the existing theories of electron–phonon interaction.
Densification Kinetics and Electrical Properties of Buried Resistors in Low-Temperature Cofired Ceramics
Authors: Cheng Ching-Tai , Lin Jiang-Tsair
Published: July 2005

The densification kinetics and electrical properties of buried resistors in low-temperature cofired ceramics (LTCCs) have been investigated. Activation energy analysis shows that the calculated activation energies, 254–301 kJ/mol, are close to that of the viscous flow of PbO–SiO2–Al2O3 glass, 246 kJ/mol, suggesting that the predominant mechanism of densification is the viscous flow of glass due to either melt formation or glass redistribution. From microstructural observations, it is further identified that glass redistribution is the rate-limiting step on the basis of the densification mechanism in the glass-ruthenium oxide system. Decreases in resistance and increases in the temperature coefficient of resistance (TCR) with increasing sintering temperature and time were observed. This result is attributed to the porosity and pore size on the basis of the analysis using the glass redistribution equation and microstructural observations. With higher porosity or smaller pore size, the probability of electron conduction is therefore decreased, resulting in a higher electrical resistance and a lower high-temperature coefficients of resistance (HTCR).
Effect of B2O3 and CuO on the Sintering Temperature and Microwave Dielectric Properties of Ba(Zn1/3Ta2/3)O3 Ceramics
Authors: Kim Min-Han , Nahm Sahn , Lee Woo-Sung , Yoo Myong-Jae , Kang Nam-Kee , Kim Hyo-Tae , Lee Hwack-Joo
Published: July 2005

Sintering temperature of the Ba(Zn1/3Ta2/3)O3 (BZT) ceramic is about 1550°C and it decreased to 950°C when B2O3 was added. The BaB4O7 second phase whose melting temperature is 889°C was found in the B2O3 added BZT ceramics. The BaB4O7 second phase assisted the sintering of the BZT ceramics at 950°C. However, the B2O3 added BZT ceramic was not sintered below 950°C and the microwave dielecric properties were not satisfactory. On the other hand, when the B2O3 and the CuO were added, the BZT ceramic was sintered even at 870°C. The BaCu(B2O5) phase which was found in the CuO and B2O3 added BZT ceramics, existed as the liquid phase during the sintering and helped the densification of the BZT ceramics at temperatures lower than 950°C. Good microwave dielectric properties of Q×f=11,000 GHz, ε
r=26 and τf=0.0 ppm/°C were obtained from the BZT + 5.0 mol% B2O3 + 10.0 mol% CuO ceramic sintered at 870°C for 2 h.
Preparation of Ba(Ti,Zr)O3 Thick-Film Microactuators on Silicon Substrates by Screen Printing
Authors: Sakai Yuichi , Futakuchi Tomoaki , Iijima Takashi , Adachi Masatoshi
Published: July 2005

BaTi0.975Zr0.025O3 thick-film microactuators were fabricated by combining screen printing and silicon micromachining. The electric properties of BaTi0.975Zr0.025O3 thick films with a small area on a Pt bottom electrode using silicon substrates prepared by screen printing were investigated. The thick films were fired in the temperature range from 1310 to 1370°C. The remanent polarization P
r and coercive field E
c were 6.2 µC/cm2 and 1.8 kV/cm at the firing temperature of 1350°C, respectively. The effective piezoelectric constant d
33 calculated from a unipolar signal curve was approximately 120 pm/V for the thick film fired at 1350°C. After measuring the electric properties of BaTi0.975Zr0.025O3 thick films, microactuators were fabricated by etching the substrates. The displacement of a microactuator that has a 0.3×0.3 mm2 area membrane and is driven at 40 Vpp and 4 kHz was approximately 0.12 µm. This indicates the possibility of applying this microactuator in lead-free micropump or micromixer devices.
Orientation of Liquid Crystal Molecules Evaporated onto Rubbed and Photoaligned Polymer Surfaces
Authors: Shioda Tatsutoshi , Okada Yoshinori , Takanishi Yoichi , Ishikawa Ken , Park Byoungchoo , Takezoe Hideo
Published: July 2005

Second-harmonic generation (SHG) and polarized ultraviolet-visible (UV-VIS) absorption have been used to study the orientational distribution function of 5CB (4'-n-pentyl-4-cyanobiphenyl) liquid crystal (LC) molecules adsorbed on rubbed and photoaligned photoisomerizable polyamic acid layers. The simultaneous analysis of SHG and polarized UV-VIS absorption data using the maximum entropy method shows that the anisotropic distribution of 5CB molecules along the rubbing direction tilts up from the surface plane as the molecular density increases. More interestingly, the anisotropy is relatively low at the first stage of the evaporation and becomes gradually pronounced, indicating an important role played by the long-range intermolecular interaction among LC molecules for LC surface alignment. No orientation formation of non-liquid crystalline 4CB (4'-n-butyl-4-cyanobiphenyl) molecules on the treated surfaces supports this conclusion. It is important to emphasize that a relatively small fraction of molecules contribute to give a polar order, but the rest form dimers even at the early stage of the evaporation. This tendency is particularly marked on the photoaligned surface; no SHG activity arises irrespective of the amount of evaporated molecules.
Control of Polymer Structures in Phase-Separated Liquid Crystal-Polymer Composite Systems
Authors: Wang Qingbing , Park Jung O. , Srinivasarao Mohan , Qiu Liou , Kumar Satyendra
Published: July 2005

The formation of different structures in phase-separated composite films (PSCOFs) from formulations of liquid crystals and photocurable monomers has been investigated using polarizing optical and scanning electron microscopies. Two processes, spatially nonuniform polymerization and diffusion of small molecules, play important roles in determining a specific PSCOF polymer structure. The variations in UV irradiation intensity and temperature, at which phase separation is carried out, strongly influence these two processes and can change the resultant structure from a homogeneous PSCOF bilayer structure to a heterogeneous polymer dispersed liquid crystal (PDLC) structure. A variation in cell thickness changes the distance through which small molecules have to diffuse during phase separation and, thus, affects the structure obtained in thick and thin cells.
13C-NMR Spin Lattice Relaxation Time Observation on the Smectic A and Smectic C* Phases of a Chiral Smectic Liquid Crystal, (S)-4-(1-methylhexyloxycarbonyl)phenyl 4'-octyloxybiphenyl-4-carboxylate
Authors: Miyayama Koji , Shikayama Yoshitaka , Iwahori Aya , Nose Takuhei , Hiraoka Kazuyuki
Published: July 2005

In order to study molecular rotation around the long axis in chiral smectic phases, the temperature dependence of the spin-lattice relaxation time T
1 is investigated in a ferroelectric liquid crystal, (S)-4-(1-methylhexyloxycarbonyl)phenyl 4'-octyloxybiphenyl-4-carboxylate (S-MH(6)POBC) by means of solid-state 13C-NMR spectroscopy. The spin-lattice relaxation time T
1 of the aromatic core increases with increasing temperature in the smectic A (SmA) and chiral smectic C (SmC*) phases, because the frequency of the molecular rotation dominating the spin-lattice relaxation process is higher than the Larmor frequency ω0 of 100 MHz in the present measurement. In addition, the temperature dependence of T
1 reveals that the activation energy of the molecular rotation in the SmC* phase is lower than that in the SmA phase.
Cell-Gap Measurement of Reflective Twisted-Nematic Liquid Crystal Display with Internal Surface-Roughened Reflector
Authors: Satake Tetsuya , Nishioka Takahiro , Kurata Tetsuyuki , Maehara Toshiaki
Published: July 2005

A new cell-gap measurement method is described for reflective twisted-nematic liquid crystal displays (TN-LCDs). The behavior of reflected-light intensity in the cell-gap measurement shows that the surface reflection of the display has a decisive influence on the obtained cell gap. The new measurement method, which takes into account the surface reflection, exhibits a good cell-gap agreement with a transmissive cell-gap measurement in an experiment using transmissive LC cells and an external reflector. Signal reflected-light intensity depends on the measurement point in the case of a display having a surface-roughened reflector. The signal becomes smaller on the slant face than both at the top and bottom of the reflector. Correction for signal variation is also included in the new method. The method is applied to microscopic cell-gap mapping using a microscope and a charge-coupled device (CCD) camera system. The cell-gap map obtained is consistent with the shape of the reflector.
High-Pressure Synthesis of Superhard Material from C60
Authors: Horikawa Takashi , Suito Kaichi , Kobayashi Michihiro , Oshima Ryuichiro
Published: July 2005

Fullerene, C60, has been investigated at a high pressure of 15 GPa and at a high temperature of 800°C using an octahedral anvil press. Samples retrieved after being heated to temperatures between 165 and 700°C under pressures from 10 to 15 GPa were found to be very hard, exhibiting micro-Vickers hardness ranging from 40 to 100 GPa. The hardness was governed by the pressure and temperature conditions studied as well as the duration of the high-temperature treatment. X-ray diffraction analysis and Raman scattering studies revealed that the hard products contained amorphous carbon consisting of s
p
2-bonded clusters with a small persistence of unknown phase.
New Dielectric Material System of La(Mg1/2Ti1/2)O3–CaTiO3 at Microwave Frequencies
Authors: Huang Cheng-Liang , Chen Yuan-Bin , Lo Ching-Wen
Published: July 2005

The dielectric characteristics and microstructures of xLa(Mg1/2Ti1/2)O3–(1-x)CaTiO3 ceramics with B2O3 additive (0.25 wt%) prepared by the conventional solid-state method were investigated. Doping with B2O3 (0.25 wt%) effectively improves the densification and the dielectric characteristics of xLa(Mg1/2Ti1/2)O3–(1-x)CaTiO3 ceramics. xLa(Mg1/2Ti1/2)O3–(1-x)CaTiO3 ceramics can be sintered at 1400°C because of the liquid phase effect of B2O3 addition observed by scanning electron microscopy. At 1450°C, 0.5La(Mg1/2Ti1/2)O3–0.5CaTiO3 ceramics with 0.25 wt% B2O3 additive have a dielectric constant (ε
r) of 43, a Q×f value of 24470 (at 8 GHz) and a temperature coefficient of resonant frequency (τf) of -8.94 ppm/°C. As the content of La(Mg1/2Ti1/2)O3 increases, the highest Q×f value of 38000 (GHz) for x=0.7 is achieved at the sintering temperature of 1475°C.
Time Dependence of the Growth Morphology of GaN Single Crystals Prepared in a Na–Ga Melt
Authors: Yamane Hisanori , Aoki Masato , Yamada Takahiro , Shimada Masahiko , Goto Hiroki , Goto Takenari , Makino Hisao , Yao Takafumi , Sarayama Seiji , Iwata Hirokazu , DiSalvo Francis J.
Published: July 2005

The yields of GaN prepared in a Na–Ga melt at 700–800°C and 1–5 MPa of N2 for 200 h were measured. The morphology of the GaN crystals changed from pyramidal (yields 6–13%) to prismatic (yields 19–100%), and finally to thin platelets (yields 61–100%) with increasing temperature and N2 pressure. A time dependence of the morphology was observed for the sample prepared at 750°C and 5 MPa of N2. The morphology changed from pyramidal, prismatic to thick platelets with heating times up to 50 h. The yield of GaN increased linearly during this period. The formation rate of GaN increased after 50 h, and the crystal growth perpendicular to the c axis was enhanced. The crystal growth was completed within 200 h, and thin platelet single crystals with a size of 1–2 mm were formed. Microphotoluminescence spectra were measured at the cross section of a thin platelet GaN crystal. A large broad luminescence peak at 3.26 eV, probably associated with Mg or Si acceptors, was observed in the spectra obtained from the regions near the (0001) Ga polar plane.
Cavitation Bubble Streaming in Ultrasonic-Standing-Wave Field
Authors: Nomura Shinfuku , Mukasa Shinobu , Kuroiwa Masaya , Okada Yasuyuki , Murakami Koichi
Published: July 2005

The mechanism of cavitation bubble streaming by ultrasonic vibration in a water tank was experimentally investigated. A standard ultrasonic cleaner unit with a resonant frequency of 40 kHz was used as an ultrasonic generator. The behavior of the streaming was visualized by the schlieren method and sonochemical luminescence, and the velocity of the streaming was measured by laser Doppler velocity measurement equipment (LDV). The cavitation bubble streaming has two structures. A cavitation cloud, which consists of many cavitation bubbles, is shaped like a facing pair of bowls with a diameter of approximately 1/3 the wavelength of the standing wave, and moves inside the standing-wave field with a velocity of 30 to 60 mm/s. The cavitation bubbles move intensely in the cloud with a velocity of 5 m/s at an ultrasonic output power of 75 W. The streaming is completely different from conventional acoustic streaming. Also the cavitation bubble is generated neither at the pressure node nor at the antinode.
Thermotropic Liquid Crystal Film Underwater
Authors: Uto Sadahito , Nakanishi Yuuji , Matsumoto Takahumi
Published: July 2005

A thermotropic liquid crystal film was produced in distilled water successfully. A lecithin suspension was utilized to make the film. Polarizing microscopic observations were carried out. The molecular arrangement was seemed to be homeotoropic. An expected electrooptic response of the film underwater was confirmed.
Electron Spin Resonance Study of Gamma-Ray-Irradiated Prince Rupert's Drops for Confirmation of Stress Effects on Paramagnetic Defect Formation in Borosilicate Glass
Authors: Murata Keisuke , Katsura Makoto
Published: July 2005

A kind of thermally tempered glass grains known as “Prince Rupert's drops” were irradiated with gamma rays and investigated by electron spin resonance (ESR). Using these drops, the irradiation and ESR measurements could be performed without changing the internal stress. It was confirmed that the residual internal stress in Pyrex (Corning 7740) glass affects the formation and thermal stability of boron oxygen hole centers, a kind of radiation-induced paramagnetic center.
Protein Crystal Growth Using Laser-Processed Seed Crystals
Authors: Takeuchi Kengo , Kitano Hiroshi , Adachi Hiroaki , Mori Yusuke , Sasaki Takatomo , Matsumura Hiroyoshi , Inoue Tsuyoshi , Murakami Satoshi , Doi Masaaki , Koga Yuichi , Takano Kazufumi , Kanaya Shigenori
Published: July 2005

We demonstrate the use of crystals processed by a pulsed UV laser as seeds for protein crystallization. A hen-egg-white lysozyme crystal, which was successfully laser-processed without causing significant damage, was seeded and grown larger than its original size. Polarized light microscopy and X-ray diffraction analysis showed that the crystal grown by seeding was a single crystal of suitable quality for X-ray crystallography. The results support the effectiveness of UV-laser processing for protein crystals. Furthermore, this seeding technique, which we call laser-cut seeding, will be useful for the production of a seed of suitable size and shape in macroseeding, for the elimination of a damaged section in a growing crystal, and for removing useless crystals from polycrystals.
Effects of Ag Thickness and Deposition Temperature on Prevention of Cu Diffusion in Cu/Ag/Si System
Authors: Yukawa Motonobu , Kitagawa Hiroki , Iida Shoji
Published: July 2005

The introduction of copper (Cu) wiring or electrodes for LSI is advanced by using a buffer layer of a material such as SiO2, TiN or TiSiN to prevent the formation of copper silicide on a silicon (Si) substrate. When metal silver (Ag) serves as a buffer between Cu and a Si substrate, the Cu might remain stable on the Ag film. A fundamental study was performed on the necessary Ag thickness for preventing Cu diffusion into the Si substrate at room temperature and 300°C; the effect of lapse time after deposition was also studied. When Ag was deposited on the Si substrate with a thickness of less than 22 nm at room temperature, Ag islands with nearly round shapes were formed and many gaps were observed between them. Cu deposited on the Ag film reached the Si surface through these gaps and diffused into the Si substrate. When the Ag film was more than 30 nm thick, the Ag islands increased in size, the Ag film became thicker, and they came into contact with each other. The gaps between the Ag islands also narrowed, preventing the diffusion of Cu. The depth profile of the Cu deposited six months prior showed no change. When the deposition was carried out at a temperature of 300°C, Ag islands grew into tall three-dimensional (3D) islands, and the gaps between them broadened. Cu diffused deeply into the Si substrate.