bluuebunny/crossref_metadata_2025 huggingface dataset:
High-Quality ZnO Layers Grown on 6H-SiC Substrates by Metalorganic Chemical Vapor Deposition
Authors: Ashrafi A. B. M. Almamun , Zhang Bao-ping , Binh Naguyen Thanh , Wakatsuki Kazuki , Segawa Yusaburo
Published: February 2005

In this letter, the 6H-SiC substrate has been studied for the growth of the ZnO layer. The X-ray diffraction measurement clearly showed the c-axis oriented growth of ZnO layers on SiC(0001) substrates. The X-ray rocking curve measurement diffracted a smaller full-width at half maximum of the ZnO layers grown on SiC than that of the same layers grown on the conventional Al2O3 substrate with metalorganic chemical vapor deposition (MOCVD). A distinct free-exciton emission was dominantly observed even at room temperature (RT) while the donor-bound-exciton peaks were disappeared at around ∼120 K. In addition, no deep-level emission was observed even at RT in the ZnO/SiC samples. These optical and crystalline properties have hardly been observed in the ZnO/Al2O3 samples grown by MOCVD. Therefore, the higher quality of the ZnO layers grown on SiC might be attributed to the smaller lattice mismatch of ∼5% as well as the +c surface orientation in ZnO/SiC sample geometry.
Chemical and Structural Stabilities of SiNx Nano-Scale Islands Formed by Ionized N2 Gas at Room Temperature
Authors: Jung Min-Cherl , Han Moonsup
Published: February 2005

Si-based nano-scale islands (NSIs) were formed by means of ionized N2 gas at room temperature (RT) on silicon substrates. The chemical states of the formed samples were found to be resolved to the intermediate states of SiN
x
and the chemically stable state of Si3N4 through the observation of Si 2p and N 1s core-level spectra obtained by X-ray photoelectron spectroscopy. The height of, the lateral size of, and the inter-distance between the NSIs were estimated to be 1.4–4.2 nm, 28–35 nm, and 30–39 nm, respectively, by atomic force microscopy analysis. The height, the lateral size, and the inter-distance decreased as the exposure time of the ionized gas increased beyond 30 min. After annealing at 700°C for 60 min, the height, the lateral size and the inter-distance increased to 4.7–6.6 nm, 36–55 nm, and 58–78 nm, respectively. The chemical compositions were stabilized to the chemically stable state of Si3N4 and meta-stable intermediate states of SiN
x
. This long-time annealing behavior of the NSIs observed in this work is different from that in the case of thermally grown silicon nitride in nitrogen gas atmosphere in which the intermediate states and other interfacial states are rapidly destroyed during high temperature treatment.
Experiments on Ion Beam Deflection Using Ion Optics with Slit Apertures
Authors: Okawa Yasushi , Hayakawa Yukio , Kitamura Shoji
Published: February 2005

An experimental investigation on ion beam deflection by grid translation was performed. The ion beam deflection in ion optics is a desired technology for ion thrusters because thrust vector control utilizing this technique can eliminate the need for conventional gimbaling devices and thus reduce propulsion system mass. A grid translation mechanism consisting of a piezoelectric motor, a ceramic lever, and carbon-based grids with slit apertures was fabricated and high repeatability in beam deflection characteristics was obtained using this mechanism. Results showed that the beam deflection angle was proportional to the grid translation distance and independent of slit width and grid voltage. A numerical simulation successfully reproduced the beam deflection characteristics in a qualitative and quantitative sense. A maximum beam deflection angle of approximately plus or minus 6 degrees, which was comparable to that of the ordinary gimbaling devices used in space, was obtained without a severe drain current. Therefore, the beam deflection by grid translation is promising as a thrust vectoring method in ion thrusters.
Influence of Substrate Biasing on (Ba,Sr)TiO3 Films Prepared by Electron Cyclotron Resonance Plasma Sputtering
Authors: Matsumoto Takeshi , Niino Atsushi , Ohtsu Yasunori , Misawa Tatsuya , Yonesu Akira , Fujita Hiroharu , Miyake Shoji
Published: February 2005

(Ba,Sr)TiO3 (BST) films were deposited by electron cyclotron resonance (ECR) plasma sputtering with mirror confinement. DC bias voltage was applied to Pt/Ti/SiO2/Si substrates during deposition to vary the intensity of bombardment of energetic ions and to modify film properties. BST films deposited on the substrates at floating potential (approximately +20 V) were found to be amorphous, while films deposited on +40 V-biased substrates were crystalline in spite of a low substrate temperature below 648 K. In addition, atomic diffusion, which causes deterioration in the electrical properties of the films, was hardly observed in the crystallized films deposited with +40 V bias perhaps due to the low substrate temperature. Plasma diagnoses revealed that application of a positive bias to the substrate reduced the energy of ion bombardment and increased the density of excited neutral particles, which was assumed to result in the promotion of chemical reactions during deposition and the crystallization of BST films at a low temperature.
Focusing of Soft X-ray using a Grazing Incidence Mirror
Authors: Hayashi Yasushi , Taniguchi Hiroaki , Gohmi Hamid , Sakamoto Nobuhiro , Watanabe Masato , Okino Akitoshi , Shiho Makoto , Horioka Kazuhiko , Hotta Eiki
Published: February 2005

Attempts have been made to focus the light beam of soft X-rays generated from an Ar capillary discharge, using a grazing incidence Wolter-type mirror. A soft X-ray beam with an image of approximately 10 mm in diameter is focused to a spot less than a 1 mm. The result proves that the Wolter-type mirror is technically applicable for the focusing of the soft X-rays generated from a capillary discharge.
Contactless Measurement of Young's Modulus Using Laser Beam Excitation and Detection of Vibration of Thin-Film Microresonators
Authors: Kobayashi Toshihiro , Ohsawa Jun , Hara Tamio , Yamaguchi Naohiro
Published: February 2005

Young's modulus of a single-crystal thin silicon film was estimated by a noncontact method. The resonance frequencies of a microresonator fabricated using the film were measured by excitation and detection using multiple laser beams. A special configuration was adopted for the resonator to suppress the heating effect of the excite beam. Clear resonances were observed in the frequency characteristics of vibration. Young's modulus was determined from an elastic modification analysis of a spring-mass system using the resonance frequency together with the geometrical dimensions of the resonator. The deduced value of Young's modulus was 152±17 MPa, which agrees with reported values within experimental errors. The cantilever beams of the resonator had trapezoidal cross sections caused by the reactive ion etching (RIE) used in the fabrication, and their widths showed nonuniformity. The error mainly comes from the nonuniformity of the beam width along the cantilever.
Wafer-Voltage Measurement in Plasma Processes by Means of a New Probe Method and an Impedance Monitor
Authors: Kanno Seiichiro , Tanaka Junichi , Tetsuka Tsutomu , Nishio Ryoji , Yamamoto Hideyuki
Published: February 2005

A new probe method, which can measure wafer voltage directly from the wafer back-side without fluctuating the plasma, was developed. This method clarified the effect of the bias power, gas pressure and gas component on wafer V
pp, V
dc, and V
dc/V
pp. In addition, current, voltage, and phase shift were measured with an impedance monitor (IM) installed between the matching network and the bias electrode. Furthermore, wafer V
pp was calculated from IM data according to a devised equivalent circuit model. It was found that calculated wafer V
pp agrees with actual wafer V
pp within 3.4% when bias power is ranged from 200 W to 500 W.
Hard X-Ray Emission from a Copper Target by Focusing a Picosecond Laser Beam at 3×1013 W/cm2
Authors: Nagao Hirofumi , Hironaka Yoichiro , Nakamura Kazutaka G. , Kondo Ken-ichi
Published: February 2005

Hard X-ray pulses are generated by focusing a picosecond laser beam (25-ps, 1064 nm) on a copper target in air at an intensity of 3×1013 W/cm2. X-ray energy is measured using an X-ray charge-coupled device. The obtained spectrum consists of strong Kα and Kβ emissions and a weak continuum at an energy range of 4–10 keV. The photon numbers of the hard X-rays (4–10 keV) were estimated to be approximately 4000 photons/4πsr/pulse.
Integration Formula of the Magnetic Field Produced by the Finite Size Helical Coil with Arbitrary Polygonal Cross Section
Authors: Todoroki Jiro
Published: February 2005

The formulae for calculating the magnetic field produced by the finite size helical coil with rectangular cross section [J. Todoroki: Kakuyugo Kenkyu 57 (1987) 318] are extended to the case with an arbitrary polygonal cross section. The formulae for the calculation of the vector potential are also presented.
Direct Synthesis of Single-Walled Carbon Nanotubes on Silicon and Quartz-Based Systems
Authors: Murakami Yoichi , Chiashi Shohei , Miyauchi Yuhei , Maruyama Shigeo
Published: February 2005

A newly developed technique of synthesizing single-walled carbon nanotubes (SWNTs) directly on the surface of Si and quartz substrates is introduced in this report. This technique adopted a liquid-based dip-coating method to mount a very small amount of catalyst metals on the surface of substrates using Mo/Co bimetallic acetate solution. The merits of this approach lie in its easy, costless, and geometry-flexible nature compared with conventional sputtering and deposition approaches. We used the alcohol catalytic chemical vapor deposition (ACCVD) method that can produce relatively high-quality SWNTs even at low temperatures down to 600°C. This low-temperature process contributes to the prevention of the agglomeration of catalytic metals on the surface and chemical reaction between catalytic metal and silicon, which helps us to eliminate any kind of intermediating support materials. Thereby synthesized SWNTs on Si and quartz substrates under various CVD conditions are characterized by means of SEM, TEM, Raman scattering, and optical absorbance measurements. The underlying reasons our experimental procedure and choice of catalyst worked for the synthesis of SWNTs are discussed through comparative studies. At the end of this report, some possible applications of this technique are stated.
Purification of Single Wall Carbon Nanotubes Using Gelatin
Authors: Takahashi Teruo , Tsunoda Katsunori , Yajima Hirofumi , Ishii Tadahiro
Published: February 2005

We have developed a simple procedure for the purification of single wall carbon nanotubes (SWNTs) with gelatin as the dispersing reagent. The steps of this procedure were performed in the following order: annealing in air, sonication in an aqueous solution of gelatin, and soaking in hydrochloric acid solution. The advantage of using gelatin as a dispersing reagent is not only that it is useful for untangling the SWNT bundles, but also that the gelatin molecule and the metallic catalyst can be removed using HCl.
Modification of Silicon Optical Properties by 250 keV Electron Irradiation
Authors: Jo Jungyol , Kim Hyo Jin , Nishihara Yoshiaki , Suezawa Hiroki , Lee Jeong Chul , Soghomonian Victoria , Heremans Jean J.
Published: February 2005

We studied the effect of electron irradiation on silicon by measuring X-ray diffraction, solar cell open circuit voltages, and optical transmission. The X-ray diffraction data shows an emerging feature indicating a 0.13% lattice expansion after 250 keV electron irradiation and H2 annealing. Solar cell voltages could be predictably modified through different irradiation and annealing conditions. The optical transmission measured in 1500-Å-thick polycrystalline silicon indicated a 40 meV band-gap widening after 100 keV electron irradiation. We explain the results as being due to the damage and relaxation of the silicon lattice, as induced by electron irradiation and subsequent annealing.
Crystal Defects in Epitaxial Layer on Nitrogen-doped Czochralski-grown Silicon Substrate (I) –Investigation of the Crystallographic Structure–
Authors: Nakai Katsuhiko , Kitahara Koichi , Ohta Yasumitsu , Ikari Atsushi , Tanaka Masahiro
Published: February 2005

We have investigated crystal defects in the epitaxial layer on nitrogen-doped Czochralski-grown silicon (CZ-Si) substrate. It was found that two types of crystal defects are generated in the epitaxial layer on the nitrogen-doped CZ-Si substrate. One is revealed to be a stacking fault and the other is a perfect dislocation pair. The origin of these defects is a rod like void and a dislocation loop in the nitrogen-doped CZ-Si substrate. We discuss the formation mechanism of the crystal defect in the epitaxial layer caused by the grown-in defect.
Al Contamination in InGaAsN Quantum Wells Grown by Metalorganic Chemical Vapor Deposition and 1.3 µm InGaAsN Vertical Cavity Surface Emitting Lasers
Authors: Takeuchi Tetsuya , Chang Ying-Lan , Leary Michael , Mars Dan , Song Yoon Kyu , Roh S. David , Luan Hsin-Chiao , Mantese Lucy-Marie , Tandon Ashish , Twist Rosemary , Belov Svetlana , Bour David , Tan Michael
Published: February 2005

We obtained high-quality InGaAsN quantum wells (QWs) by metalorganic chemical vapor deposition (MOCVD). Our InGaAsN QWs showed low threshold current densities and high-temperature characteristics (550 A/cm2, 150 K at 1275 nm for 3QWs) in broad-area lasers. High output power (2.8 mW at 1280 nm) was also obtained from the room-temperature continuous operation of InGaAsN 3QW vertical cavity surface emitting lasers. We revealed the first solid evidence that unexpected Al incorporation (Al contamination) occurred in InGaAsN QWs continuously grown on GaAs/AlGaAs structures by MOCVD. Our results suggest that Al contamination leads to a rough surface and low photoluminescence intensity of the InGaAsN QWs. By minimizing Al contamination, high-quality InGaAsN QWs were obtained. Al contamination in InGaAsN QWs should be carefully considered in the MOCVD growth of InGaAsN-based devices.
Optical and Structural Characteristics of Virtually Unstrained Bulk-Like GaN
Authors: Gogova Daniela , Kasic Alexander , Larsson Henrik , Pécz Bela , Yakimova Rositza , Magnusson Björn , Monemar Bo , Tuomisto Filip , Saarinen Kimmo , Miskys Claudio , Stutzmann Martin , Bundesmann Carsten , Schubert Mathias
Published: February 2005

Bulk-like GaN with high structural and optical quality has been attained by hydride vapor-phase epitaxy (HVPE). The as-grown 330 µm-thick GaN layer was separated from the sapphire substrate by a laser-induced lift-off process. The full width at half maximum values of the X-ray diffraction (XRD) ω-scans of the free-standing material are 96 and 129 arcsec for the (1 0 -1 4) and (0 0 0 2) reflection, respectively, which rank among the smallest values published so far for free-standing HVPE-GaN. The dislocation density determined by plan-view TEM images is 1–2×107 cm-2. Positron annihilation spectroscopy studies show that the concentration of Ga vacancy related defects is about 1.5×1016 cm-3. The high-resolution XRD, photoluminescence, µ-Raman, and infrared spectroscopic ellipsometry measurements consistently prove that the free-standing material is of high crystalline quality and virtually strain-free. Therefore it is suitable to serve as a substrate for stress-free growth of high-quality III–nitrides based device heterostructures.
Novel Cladding Structure for ZnSe-based White Light Emitting Diodes with Longer Lifetimes of over 10,000 h
Authors: Nakamura Takao , Fujiwara Shinsuke , Mori Hiroki , Katayama Koji
Published: February 2005

We have demonstrated ZnSe-based white light emitting diodes (LEDs) with longer lifetimes of over 10,000 h at 14.5 A/cm2 by introducing an i-ZnMgBeSe/p-ZnMgSe double cladding structure, which includes a very thin i-ZnMgBeSe layer for suppressing electron overflow and a p-ZnMgSSe layer for efficient p-type carrier concentration. By adopting the double cladding layer instead of only the conventional p-ZnMgSSe cladding layer, rapid degradation is suppressed and the lifetime tendency becomes similar to that of the LEDs consisting of a III–V semiconductor system. The device simulation and the temperature dependence of optical power showed that the i-ZnMgBeSe layer played the main role in increasing electron confinement. Our experimental data and reliability test results indicate that the suppression of the electron overflow is essential to achieve a long lifetime acceptable for practical use.
Hot Carrier Degradations of Dynamic Threshold Silicon on Insulator p-Type Metal–Oxide–Semiconductor Field Effect Transistors
Authors: Chao Tien-Sheng , Lee Yao-Jen , Huang Chun-Yang , Lin Horng-Chih , Li Yiming , Huang Tiao-Yuan
Published: February 2005

In this study, we compared the hot carrier effects of T-gate and H-gate Silicon on Insulator p-Type Metal–Oxide–Semiconductor Field Effect Transistors (SOI pMOSFETs) operating under dynamic threshold mode (DT-mode) and normal mode at various temperatures. By operating under DT-mode, the threshold voltage shift is reduced. However, enhanced degradations in maximum transconductance and drive current are observed when operating under DT-mode at room temperature, especially for the T-gate structure. The transconductance enlargement effect for devices operating under DT-mode, together with the non-uniform potential distribution in T-gate structure, are believed to be responsible for the observed enhanced degradations. At elevated temperatures, the hot-carrier-induced degradations are alleviated for devices operating under DT-mode, to levels close to those of the normal mode, due to reduced impact ionization at higher temperature.
Control of Pore Structures in Periodic Porous Silica Low-k Films
Authors: Hata Nobuhiro , Negoro Chie , Yamada Kazuhiro , Kikkawa Takamaro
Published: February 2005

The structure of nanometer-size pores in periodic porous silica low-dielectric-constant (low-k) films was investigated by in-plane and out-of-plane X-ray scattering and diffraction. The periodic porous silica films were prepared by spin coating of a tetraethoxysilane (TEOS)-based precursor solution mixed with self-organizing surfactant sacrificial template molecules. TEOS vapor treatment before the removal of the sacrificial templates was shown to help maintain the periodically ordered structure during the template removal process at 673 K. It was demonstrated that a successful control of pore structure is feasible by the selection of pore-generating surfactant template molecules. Namely, the pore diameter, porosity and dielectric constant were controlled successfully by varying the alkyl chain length in the surfactant template molecules.
Minimizing Search Method for Wideband Visible or Wideband Infrared Antireflection Coating Design
Authors: Liou Yeuh-Yeong
Published: February 2005

A design algorithm based on the minimizing search technique was proposed for designing the normal-incidence wideband visible or wideband infrared multilayer antireflection coating. The method utilized a tuning operation of the thickness of sublayers first, and then refined the antireflective performance and simplified the design by a layer minimizing operation. It was shown that the average visible spectral reflectivities of three-material thirty-layer and two-material thirty-layer minimizing search antireflection coating designs for glass substrates were reduced to less than 0.054% and 0.056% with a 12-layer structure, and the average infrared reflectivity of a two-material forty-layer minimizing search antireflection coating design for a germanium substrate over the broadband spectral region of 7.7–12.3 µm was reduced to less than 0.488% with a 22-layer structure.
Fabrication of Semiconductor Laser for Integration with Optical Isolator
Authors: Sakurai Kazumasa , Yokoi Hideki , Mizumoto Tetsuya , Miyashita Daisuke , Nakano Yoshiaki
Published: February 2005

As a preliminary experiment for achieving a monolithic integration of a semiconductor laser and an optical isolator, a Fabry–Perot laser integrated with an optical passive waveguide was fabricated using the wafer grown by a selective-area growth technique. We report the characteristics of the laser diode and the loss estimation in the fabricated device.
All-Optical Switching and Memorizing Devices Using Resonant Photon Tunneling Effect in Multi-Layered GaAs/AlGaAs Structures
Authors: Yamamoto Naokatsu , Ohtani Naoki
Published: February 2005

We propose a new structure for all-optical switch (AOS) and all-optical memory (AOM) devices that use the resonant photon tunneling effect in multi-layered GaAs/AlGaAs structures. Numerical calculations revealed a sharp peak in tunneling probability at a resonant incidence angle in double-barrier AOS structures. The resonance angle can be controlled by changing the refractive index of an active layer. During simulation, we demonstrated that the AOS with the new structure acts as an all-optical NOT gate. We also found that optical bi-stability occurs in the dependence of reflectivity on control light intensity. This bi-stability is caused by the penetration of intense input light to the active layer based on the resonant photon tunneling effect, and it is clear that an AOM can be achieved through this bi-stability effect. These results indicate that the resonant photon tunneling effect in multi-layered semiconductor structures can effectively be used to attain efficient all-optical devices.
A Novel Driving Method for Fast Switching of a π Cell for Display of Moving Pictures
Authors: Lee Seo Hern , Kang Jin-Woo , Lee Gi-Dong , Yoon Tae-Hoon , Kim Jae Chang
Published: February 2005

We propose a novel driving method which is very efficient for the display of moving pictures on a π cell. In the proposed driving method, each scan pulse is divided into two parts for fast switching unlike the conventional active matrix driving method that uses one scan pulse for each frame. By overdriving or underdriving the π cell using an appropriate data voltage during the first scan time and applying a desired data voltage to the cell during the second scan time, we can achieve fast switching between all gray levels within the time between the first and second scan pulse.
A Piezoelectric Micromotor with a Stator of φ=1.6 mm and l=4 mm Using Bulk PZT
Authors: Cagatay Serra , Koc Burhanettin , Moses Paul , Uchino Kenji
Published: February 2005

The smallest discrete piezoelectric ultrasonic motor using bulk ceramics was developed. We are proposing basically a two-part motor: stator and rotor. The stator of the present motor consists of a hollow metal brass tube with outer diameter of 1.6 mm, inner diameter of 0.8 mm and length of only 4 mm with 2 PZT plates bonded onto it. Owing to the asymmetrical stator surface, two degenerated orthogonal bending modes were slightly split, resulting in a wobbling motion. Thus, the motor can be driven by a single driving source. The rotor is a spring, which is basically different from previous designs, pressed at both ends to the stator by a pair of ferrules. Consequently, the length of the whole motor assembly was reduced significantly; a final motor length of only 5 mm was obtained. The working frequency under zero load was approximately 227–233 kHz. Although the size is small, relatively high power was obtained under an optimized load condition: torque of 0.06 mNm, maximum power of 3.2 mW with a speed of 118 rad/s, and maximum efficiency of 11% under 48 Vrms at 221 kHz.
Improvement in Structural and Electrical Properties of (Ba0.5Sr0.5)TiO3 Capacitors Using (Ba0.5Sr0.5)RuO3 Conductive Layers at (Ba0.5Sr0.5)TiO3/Pt Interface
Authors: OH Young-Nam , YOON Soon-Gil
Published: February 2005

BST thin films and BSR interlayers were deposited by pulsed laser deposition (PLD) and liquid-delivery metalorganic chemical vapor deposition (LDMOCVD) onto Pt/TiO2/Si substrates, respectively. Ultrathin BSR conductive layers were inserted at the BST/Pt interface to improve the dielectric properties of BST thin films. BST films deposited on ultrathin BSR interlayers showed an improvement in roughness and microstructure compared with those without BSR layers in an overall range of BST film thickness. The temperature-independent interface capacities in BST/Pt and BST/BSR/Pt structures are approximately 8.9 and 20 µF/cm2, respectively. The dielectric properties of BST films were improved by the increase in interface capacity as well as roughness and microstructure using the BSR conductive layer which is similar to BST in crystal structure and chemical composition.
Crosstalk Studies of In-Plane Switching Mode under Different Pixel- and Common-Electrode Configurations
Authors: Lin Jiunn-Shyong , Yang Kei-Hsiung , Chen Shu-Hsia
Published: February 2005

In thin-film-transistor liquid-crystal display (TFT-LCD), particularly pixel-electrode configuration of in-plane switching (IPS) mode, crosstalk caused by capacitive coupling between pixel electrodes and data lines could result in image degradation. We derived the capacitive coupling ratio (CCR) of the IPS cell and analyzed the CCR of three conventional TFT-IPS pixel- and common-electrode structures to quantify the crosstalk properties. The effect of coupling voltage on electro-optics characteristics has been investigated. Our results showed that a common electrode placed adjacent to the data line could shield capacitive coupling between the data line and the pixel electrodes, and reduce CCR from 13% to 2.4% and crosstalk intensity ratio (CIR) from 21.2% to 3.9%. We also report the common-overlapping-pixel structure that not only increases the aperture ratio by 1.28 times but also reduces CCR from 13% to 9.1%.
Non-Contact Thermophysical Property Measurements of Liquid and Undercooled Alumina
Authors: Paradis Paul-Francois , Ishikawa Takehiko , Saita Yutaka , Yoda Shinichi
Published: February 2005

The density and the isobaric heat capacity of alumina in its liquid and undercooled states were measured using an electrostatic levitation furnace. Over the 2175 to 2435 K temperature interval, the density can be expressed as ρ(T)=2.93×103-0.12(T-T
m) (kg·m-3) with T
m=2327 K, yielding a volume expansion coefficient α(T)=4.1×10-5 (K-1). In addition, the isobaric heat capacity can be estimated as C
P(T)=153.5+3.1×10-3(T-T
m) (J·mol-1·K-1) if the hemispherical total emissivity of the liquid remains constant at 0.8 over the 2120 K to 2450 K interval. The enthalpy and entropy of fusion have also been calculated respectively as 109.0 kJ·mol-1 and 46.8 J·mol-1·K-1.
Lamb Waves Propagating in an LiNbO3 Plate under the Mechanical and Dielectric Loadings of a Fluid
Authors: Yang Che-Hua , Lai Yu-An
Published: February 2005

This research is focused on exploring the fluid loading effects on the dispersion spectra of Lamb modes propagating in a piezoelectric (X-LiNbO3) plate. Theoretical calculations based on a partial wave analysis are used to characterize the shifting behaviors of dispersion spectra caused by the loading fluid with mechanical/dielectric properties. On the other hand, the fluid loading effects are experimentally investigated by measuring the dispersion spectra of an X-LiNbO3 plate with free and immersed boundary conditions. Results of the theoretical calculations are supported by the measurement. It is also found that, for the case of water as a common immersion fluid for an X-LiNbO3 plate, the dielectric loading effect dominates the shifting of the dispersion spectra, while the mechanical density loading effect can be neglected.
Laser Ablation Condensation and Transformation of Baddeleyite-Type Related TiO2
Authors: Chen Shuei-Yuan , Shen Pouyan
Published: February 2005

A high-pressure phase of TiO2 with a baddeleyite-type related structure has been synthesized via very rapid heating-cooling under energetic Nd-YAG laser pulse irradiation of the Ti target in oxygen ambient. Spherical nanoparticles transformed martensitically into baddeleyite-type and then α-PbO2-type structures with accompanied transformation twinning, shearing and shape change into ellipsoid upon electron irradiation. The relatively large particles followed the same transformation path yet with alternative lattice correspondence and additional multiple deformation twinning of the baddeleyite type.
Effect of Buffer Layer on Epitaxial Growth of YSZ Deposited on Si Substrate by Slower Q-switched 266 nm YAG Laser
Authors: Kaneko Satoru , Akiyama Kensuke , Shimizu Yoshitada , Ito Takeshi , Yasaka Shinji , Mitsuhashi Masahiko , Ohya Seishiro , Saito Keisuke , Watanabe Takayuki , Okamoto Shoji , Funakubo Hiroshi
Published: February 2005

Yttria-stabilized zirconia (YSZ) was grown on Si(100) substrate by pulsed laser deposition (PLD). The laser used in this study was a 266 nm YAG laser with a second function generator modulating only the Q-switch while the primary generator modulated the flash lamp (slower Q-switch). Epitaxial growth was verified on YSZ film deposited without oxygen gas followed by primary deposition in oxygen atmosphere on Si substrate with a ∼0.4-nm-thin oxide layer. The crystallinity was strongly dependent on the thickness of the buffer layer deposited prior to the primary deposition of YSZ. The epitaxial growth was confirmed by φ scan, and ω scan (rocking curve) showed the full width at half maximum (FWHM) of 1.1 deg. The required oxygen pressure for epitaxial growth was quite high compared to that of excimer deposition.
Improved Resonance Characteristics by Thermal Annealing of W/SiO2 Multi-Layers in Film Bulk Acoustic Wave Resonator Devices
Authors: Kim Dong-Hyun , Yim Munhyuk , Chai Dongkyu , Park Jin-Seok , Yoon Giwan
Published: February 2005

In this paper, we, for the first time, present the effects of the thermal annealing of the W/SiO2 multi-layer Bragg reflectors on the resonance characteristics of the ZnO-based film bulk acoustic wave resonator (FBAR) devices. In order to improve the resonance characteristics of the FBAR devices, we employed a thermal annealing process after the Bragg reflectors were formed on a silicon substrate using a radio frequency (RF) magnetron sputtering technique. As a result, the resonance characteristics of the FBAR devices were observed to strongly depend on the annealing conditions applied to the Bragg reflectors. The FBAR devices with the Bragg reflectors annealed at 400°C/30 min showed excellent resonance characteristics as compared to those with the non-annealed (as-deposited) Bragg reflectors. The newly proposed simple thermal annealing process will be very useful to more effectively improve the resonance characteristics of the future FBAR devices with multi-layer Bragg reflectors.
Metal/Semiconductor Interfaces Studied by Transmitted X-ray Reflectivity
Authors: Takahashi Isao , Inoue Koji , Kitahara Amane , Terauchi Hikaru , Sakata Osami
Published: February 2005

Buried metal/Si interfaces were studied by X-ray reflectivity (XR) for samples which have macroscopically thick metal overlayers with rough surfaces. XR under transmission geometry (transmitted X-ray reflectivity (TXR)) was conducted so as to avoid the troublesome effects caused by the thick and rough overlayers. A 40-µm-sized X-ray beam of short wavelength (λ=0.06 nm) emitted from an undulator in a synchrotron radiation facility was used effectively. TXR of a [Au layer consisting of Au fine particles]/Si interface indicates a sharp contrast to the conventional XR scattered from the Au layer surface: The former (TXR) shows a distinct specular reflectivity from the interface. However, the latter (XR) indicates very weak specular reflectivity above the critical angle due to the microscopic surface roughness of the overlayer. Quantitative analysis of diffuse scattering in TXR profiles yielded a precise electron density at the interface. Both the specular and diffuse TXR from a [liquid Ga]/Si interface support an intermediate layer of approximately 2 nm thick. By considering the average electron density, it is most likely that Ga is sorbed to a large extent in the native oxide at unexpectedly low temperatures (<400 K).
Postgrowth Irradiation of Hydrogenated Amorphous Carbon thin Films by Low-Energy Ion Beam
Authors: Song Kie Moon , Rho Soon Joon , Ahn Han Jin , Kim Kyung Chan , Baik Hong Koo , Hwang Jeoung-Yeon , Jo Yong-Min , Seo Dae-Shik , Lee Se Jong
Published: February 2005

Liquid crystal (LC) alignment property was investigated on hydrogenated amorphous carbon (a-C:H) thin films. a-C:H thin films were deposited by a remote plasma-enhanced chemical vapor deposition (RPECVD) method with C2H2 and He gases. The surface property of a-C:H thin films was controlled by low-energy Ar ion beams. Ion beam irradiation results in the decrease in optical band gap and transmittance, and the increase in the I
D/I
G ratio of a-C:H thin films. LC alignment was generated by ion beam irradiation on the surface of a-C:H thin films. LC alignment property was affected by ion-beam-induced anisotropic sp2 structures on the surface of a-C:H thin films.
Relationship between the Photocatalytic Characteristics and the Oxygen Partial Pressure of TiO2 Thin Films Prepared by a DC Reactive Sputtering Method
Authors: Noguchi Daisuke , Kawamata Yoshio , Nagatomo Takao
Published: February 2005

It was confirmed that the oxygen partial pressure that is used during DC reactive sputtering can influence the generation of oxygen defects on TiO2 thin films and/or the surface structure, which then affects the photocatalytic characteristics. TiO2 films were deposited by DC reactive magnetron sputtering on a Si wafer at 250°C under oxygen partial pressures of 0.1 Pa, 0.5 Pa and 0.8 Pa. Structural analysis of the TiO2 thin films was conducted using X-ray diffraction (XRD), field-effect scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS), the photo luminescence method (PL). Characterization of the photocatalytic properties was performed by measuring the concentration change of methylene blue (wet methylene blue method) and the change of the contact angle with pure water. All films showed a polycrystalline anatase structure. TiO2 thin films deposited under reducing conditions (an oxygen partial pressure of 0.1 Pa) exhibited peaks that are characteristic of Ti3+ and can also contain a number of oxygen defects. The domain size was about 150–300 nm, and the domain boundaries were unclear. On the other hand, for TiO2 thin films deposited in oxidizing mode (oxygen partial pressures of 0.5 Pa and 0.8 Pa), the peak corresponding to Ti3+ was not observed. The domain size was between 300–1000 nm and the boundaries were clear. TiO2 thin films exhibit better photocatalytic properties when the domain size is large and there are fewer oxygen defects in the film. It has been suggested that the decreasing proportion of domain boundaries, which act as trapping centers for electrons, and the lower concentration of oxygen defects, which act as recombination centers for electron-hole pairs, improved the photocatalytic characteristics.
Breakdown Characteristics of Porous Metals
Authors: Furuya Seizo , Takano Saburo , Irisawa Juichi
Published: February 2005

We have investigated the breakdown characteristics of porous metals as discharge electrodes, for applications to multichannel arc gaps. We examined a single-needle/plane gap as a nonuniform electric field gap and a sphere/plane gap as a uniform one using a mirror-finished brass plate and a porous metal as plane electrodes. First, we examined the breakdown characteristics of the single-needle/plane gap. The characteristics we investigated are the DC flashover voltage of the gap, and the formative and statistical time lags of flashover when a flat-top nanosecond pulse was applied to the gap. We predicted that the formative and statistical time lags decrease when porous metals are used as a discharge electrode instead of a mirror-finished electrode. However, contrary to our prediction, a significant difference was not observed in the needle/plane experiments. Then we examined a sphere/plane gap. In this case, a significant difference was observed. Therefore, we confirm that the porous metal is a suitable electrode material for the rail gap.
Effects of Substrate Temperature on the Properties of Alq3 Amorphous Layers Prepared by Vacuum Deposition
Authors: Chung Jia-Ming , Luo Ying-Zi , Jian Zhi-An , Kuo Ming-Chin , Yang Chu-Shou , Chou Wu-Ching , Chiu Kuan-Cheng
Published: February 2005

In this study, various Alq3 amorphous layers are prepared by vacuum deposition at different substrate temperatures T
sub. The surface morphology, structural information, and electrical and optical properties of these as-deposited layers are studied by atomic force microscopy, X-ray diffraction, J–E curves, and photoluminescence studies, respectively. The optimum deposition conditions for Alq3 amorphous layers with respect to T
sub are also discussed.
Two-Dimensional Linear Birefringence Vector Measurement by Polarization-Stepping Interferometer
Authors: Lang Kuo-Chen , Teng Hui-Kang , Chang Hsiu-Fong , Han Chien-Yuan , Chou Chien
Published: February 2005

A simple polarization-stepping technique in combination with a common-path homodyne interferometer is proposed in order to measure the phase retardation and the fast-axis angle, which are defined as the linear birefringence vector (LBV), of a wave plate (WP). At three different orientation angles of the linear polarization of incident laser beam, two-dimensional (2-D) interference patterns with respect to different orientation angle are recorded by using a CCD camera. Thus, 2-D phase retardation and fast-axis angle distributions of WP are determined simultaneously. In addition, the elliptical polarization and misalignment of the orientation angle of the incident laser beam induced errors on LBV measurement are discussed.
Instability of Field Emission from a Standalone Multiwalled Carbon Nanotube with an Insulator Barrier
Authors: Tanaka Hiroyoshi , Akita Seiji , Pan Lujun , Nakayama Yoshikazu
Published: February 2005

The instability of the electron field emission from a standalone multiwalled carbon nanotube with and without an insulator barrier has been investigated. The insulator barrier is an amorphous carbon layer formed by electron beam induced deposition and removed by a heat treatment during the field emission in situ. It is found that the emission current is quite noisy when the tip is covered with the amorphous carbon layer but stable after removing it. The instability is discussed in term of the applied voltage dependence of the noise frequencies and the behavior of the bright spots in the field emission microscope images.
Production of Carbon Mesocell by Arc Electric Discharge
Authors: Yoshimura Toshihiko , Yamashita Youji , Inami Kazunori , Kato Hiroyuki , Tsutsumoto Takahiro
Published: February 2005

The generation of a carbon nanotube and the first stage of carbon nanotube or carbon fiber formation were investigated in arc electric discharge in a gas mixture of helium and atmosphere with a negative carbon electrode containing lithium or potassium. A carbon stick with lithium and a carbon stick with potassium appeared to accelerate the generation of the carbon nanotube. It was found that the generation of the carbon nanotube is restricted in the range of atmospheric partial pressure from 10 kPa to 20 kPa, and an ideal spherical substance with a size from one hundred nanometers to five micrometers was generated. If the atmospheric partial pressure is lower than that range, the spherical substance changes into a carbon nanotube or carbon fiber. The carbon mesocell, which includes various kinds of elements, can be produced by choosing a carbon stick with additional elements.
Nanometer Trench Fabricated by Atomic Force Microscopy
Authors: Yukiya Tokio , Aizawa Kouji , Fujihashi Chugo
Published: February 2005

Nanometer trenches were successfully produced by NaOH etching of the Ti oxide lines produced by atomic force microscopy (AFM) anodization on Ti thin films of 6 nm thickness on Si thermal oxidation films. The full width at half maximum (FWHM) of a nanometer trench is estimated to be approximately 20 nm, which is comparable to the radius of curvature of the AFM cantilever. It is found that the etching rate of the Ti oxide lines produced by AFM anodization depends on oxide lines height. The selection ratio of etching rate of the Ti thin film and oxide lines is 10 for oxide lines of 2 nm height, the etching rates being approximately 0.08 and 0.87 nm/min, respectively. Ti nanometer wires having 20 nm FWHM could be formed from two nanometer trenches placed close together in parallel.
Intelligent BSIM4 Model Parameter Extraction for Sub-100 nm MOSFET Era
Authors: Li Yiming , Cho Yen-Yu
Published: February 2005

We present, in this paper, an intelligent extraction technique for obtaining a set of optimal model parameters of the Berkeley short-channel insulated gate field effect transistor model 4 (BSIM4) for sub-100 nm metal-oxide-semiconductor field effect transistors (MOSFETs). Based on the genetic algorithm (GA), the monotone iterative Levenberg-Marquardt (MI-LM) method, and the neural network (NN) algorithm, this novel approach can perform simultaneous BSIM4 parameter extraction with more than 16 sub-100 nm MOSFETs in a global sense. Before extraction, all input measured I-V data are preprocessed by statistical reduction and sampling procedures. The GA and MI-LM method are then applied to calculate all parameters. The NN algorithm is used to trace the errors of I-V curves and their first derivatives, and also to inspect the variations of physical quantities. Once parameters are found, the postprocess will identify a sensible searching path so that the solution engine continues evolution until parameters reach specified stopping criteria. Good accuracy is obtained for the 90 nm NMOSFETs by several testing cases. Compared with manual fitting processes, this methodology overcomes the conventional inconvenience and is cost-effective in automatic parameter extraction. It bridges device fabrication technology and system-on-a-chip (SOC) design.
Optimization of The Ultra-Low Dark Current Complementary MOS Image Sensor Cell Using n+ Ring Reset
Authors: Huang Po-Hao , Cheng Hsiu-Yu , Chiang Wen-Jen , Lai Cheng-Hsiao , King Ya-Chin
Published: February 2005

An ultra low dark current pixel has been developed for embedded active-pixel complementary metal oxide semiconductor (CMOS) image sensors using a standard CMOS logic process. Conventional CMOS image sensors suffer from high dark current as a result of the high interface state density at the field oxide edge. In the proposed novel pixel, the photo-sensing diode is surrounded by a ring-shaped poly-silicon reset gate which isolates the photo-sensing area from the field oxide edge. Hence, the dark current level can be effectively reduced. However, in the novel pixel, the large overlap capacitance between the reset poly-gate ring and the sensing node can severely affect the output swing. To optimize this novel pixel, the poly-silicon gate is limited to isolate the photo-sensing area from the field oxide edge. Furthermore, a constant bias voltage applied to the poly-silicon gate provides an additional advantage of extended dynamic range. The effects of technology scaling on the pixel performance are investigated as well.
Trench Insulated Gate Bipolar Transistor for the Improved Short Circuit Capability Employing Curved Junction and Wide Cell Pitch
Authors: Kim Soo-Seong , Ha Min-Woo , Choi Yearn-Ik , Han Min-Koo
Published: February 2005

A trench insulated gate bipolar transistor (IGBT) employing the curved p-well junction and wide cell pitch, which improves the short circuit capability, is proposed and verified by the 2D numerical simulation. The wide cell pitch improves the short circuit immunity of the proposed IGBT due to the reduced current level under the short circuit condition. The curved p-well junction and the carrier stored layer (CSL) move the highly resistive region toward the surface so that the saturation voltage of the proposed IGBT is slightly higher than that of the conventional IGBT. The short circuit withstanding time of the proposed IGBT is 2.4 times higher than that of the conventional one without any increase of the conduction loss.
Optimization of Active Geometry Configuration and Shallow Trench Isolation (STI) Stress for Advanced CMOS Devices
Authors: Lin Tony , Gong Yoyi , Tseng Jung-Tsung , Yu Lorenzo , Shen Tzermin , Chen Daniel , Chen T. P. , Kuo Chien-Li , Shiau Wei-Tsun , Jung Le-Tien , Chen J. K. , Chien S. C. , Sun S. W.
Published: February 2005

Mechanical stress induced by active geometry is optimized for minimum variation of complementary metal oxide semiconductor (CMOS) electrical characteristics with varying active profiles. In this study, wafers with two different shallow trench isolation (STI) stress levels were investigated. By co-optimizing the active profile and STI stress level of model test structures, less than 3% device deviation is achieved when compared with simulation program with integrated circuit emphasis (SPICE) model in the full breadth of N channel and P channel metal oxide semiconductor (N/PMOS) geometry.
Stable Extraction of Threshold Voltage Using Transconductance Change Method for CMOS Modeling, Simulation and Characterization
Authors: Choi Woo Young , Woo Dong-Soo , Choi Byung Yong , Lee Jong Duk , Park Byung-Gook
Published: February 2005

We proposed a stable extraction algorithm for threshold voltage using transconductance change method by optimizing node interval. With the algorithm, noise-free g
m2 (=dg
m/dV
GS) profiles can be extracted within one-percent error, which leads to more physically-meaningful threshold voltage calculation by the transconductance change method. The extracted threshold voltage predicts the gate-to-source voltage at which the surface potential is within k
T/q of φs=2φf+V
SB. Our algorithm makes the transconductance change method more practical by overcoming noise problem. This threshold voltage extraction algorithm yields the threshold roll-off behavior of nanoscale metal oxide semiconductor field effect transistor (MOSFETs) accurately and makes it possible to calculate the surface potential φs at any other point on the drain-to-source current (I
DS) versus gate-to-source voltage (V
GS) curve. It will provide us with a useful analysis tool in the field of device modeling, simulation and characterization.
Ni-Salicided Poly-Si/poly-SiGe-Layered Gate Technology for 65-nm-node CMOSFETs
Authors: Muto Akiyoshi , Ohji Hiroshi , Maeda Takeshi , Torii Kazuyoshi , Kitajima Hiroshi
Published: February 2005

A poly-Si/poly-SiGe-layered gate electrode with a high Ge content that is suitable for Ni silicidation has been examined. The optimum Ge content for suppressing gate depletion was found to be 30%. It was found that the in situ deposition of a thin Si layer after SiGe deposition was effective in suppressing void formation. A smooth Si0.7Ge0.3 film without voids was obtained as either polycrystalline or amorphous. The enhancement of boron activation in poly-Si0.7Ge0.3 was confirmed while gate depletion became large for α-Si0.7Ge0.3 because of its lower boron diffusivity. Stable Ni silicidation over the 300 mm wafers was achieved by using a poly-Si/poly-Si0.7Ge0.3-layered gate electrode.
Advanced PMOS Device Architecture for Highly-Doped Ultra-Shallow Junctions
Authors: Surdeanu Radu , Pawlak Bartlomiej J. , Lindsay Richard , Dal Mark van , Doornbos Gerben , Dachs Charles J. J. , Ponomarev Youri V. , Loo Josine J. P. , Cubaynes Florence N. , Henson Kirklen , Verheijen Marcel A. , Kaiser Monja , Pages Xavier , Stolk Peter A. , Taylor Bill , Jurczak Malgorzata
Published: February 2005

In this paper we study the integration of Boron ultra-shallow junctions (USJ) obtained by Germanium pre-amorphization, Fluorine co-implantation and fast ramp-up and ramp-down anneals into advanced p-channel metal-oxide-semiconductor (PMOS) devices. Several integration issues associated to these USJ are investigated: short-channel effects control, implantation tilt angle influence, junction de-activation, thermal budget, silicide process. We show that remarkable PMOS device performance enhancement (I
on=450 µA/µm at I
off=250 nA/µm for devices with L
g\cong50 nm) can be achieved when full potential of highly-active and abrupt USJ is exploited by combining it with a low thermal budget integration scheme and a low contact resistance NiSi.