bluuebunny/crossref_metadata_2025 huggingface dataset:
Structural Investigations on (BaxSr1-x)(ZryTi1-(y+δ)Taδ)O3 Dielectric Resonator Compounds Used for Microwave Applications
Authors: Joseph John , Vimala T. M. , K. C. James Raju K. C. James Raju , V. R. K. Murthy V. R. K. Murthy
Published: October 2002

Structural investigations on ABO3 type perovskite dielectricresonator (DR) compounds, namely (Ba0.29Sr0.71)(Zr_0.973Ti_0.027)O_3 [BSZT] and (Ba_0.29Sr_0.71)(Zr_0.951Ti_0.039Ta_0.01)O_3 [BSZTTa] were carried out using X-ray Rietveld method. The structures were found to be isostructural with SrZrO_3 and belong to the space group Pbnm. In both the structures, the tilt angles of the BO_6 octahedra were lower than that in SrZrO_3. The volume of the octahedron was comparable for all the three. When Ta was substituted in BSZT, dielectric resonator properties of the resulting product BSZTTa improved substantially.
Oxidation Behavior of Ta Thin Films as a Passivation Layer Deposited on Cu
Authors: Ichikawa Takaaki , Mayumi Takeyama Mayumi Takeyama , Atsushi Noya Atsushi Noya
Published: October 2002

The oxidation behavior of Ta films (500 Å) deposited on Cu as a passivation layer to protect Cu from oxidation has been examined. In the present Ta thin films on Cu, the kinetics of oxidation agree well with one reported in the larger thickness range. Although the outdiffusion of a small amount of Cu through the Ta layer is observed, the Ta layer is effective as a passivation layer during oxidation at 450° C for 1 h, where the entire Ta layer is completely oxidized.
Monte Carlo Simulation of Grain Boundary Cross Effect on Hydrogen Diffusivity in Aluminum
Authors: Minoru Ichimura Minoru Ichimura , Yasushi Sasajima Yasushi Sasajima
Published: October 2002

Assuming the jumping of interstitial impurities to neighboring sites, the diffusivity is simulated by the Monte Carlo method based on the random walk theory. The jumping probability along a grain boundary is greater than that in the lattice of an inside grain. The crossing point of grain boundaries has a smaller jummping probability to neighboring sites on the grain boundary than that in the lattice. The results of simulation support the grain boundary cross effect, proposed experimentally by us, on the grain size dependence of hydrogen diffusivity in an aluminum polycrystal. The diffusivity shows a peak at some critical grain size. The peak includes two conflicting effects of grain boundaries: enhancement of diffusion along grain boundaries and suppression of diffusion by trapping at grain boundary junctions.
Quartet ESR Signals Detected from Natural Clay Minerals and Their Applicability to Radiation Dosimetry and Dating
Authors: Tatsuro Fukuchi Tatsuro Fukuchi
Published: October 2002

Some ESR signals have been detected from fault clay gouge of the Nojima Fault exposed by the Hyogo-ken Nanbu Earthquake in 1995. One signal may be attributed to a hydroxyl radical (HOHC; Si–O°H) binding with a H2O+ ion which is obtained by ionizing interlayer water in montmorillonite ( Si–O°H3O+). The oxygen hole center (OHC; Si–O°) combining with a hydronium ion ( H3O+) is split into quartet lines with the intensity ratio of 1:3:3:1 by hyperfine coupling of three equal protons (I=1/2). The quartet signal had often been detected from hydrothermal silicas or weathered feldspars in nature, however its physical model has not yet been established. Another signal is attributable to a CO3
3- radical stabilized by an exchangeable cation existing in the interlayer and detected only by artificial irradiation due to its low thermal stability. These ESR signals uniformly increase upon artificial irradiation with X-rays and are applicable to radiation dosimetry (0.1–20kGy) and dating (0.01–20 Ma).
Diffused Nitrogen-Related Deep Level in N-Type Silicon
Authors: Fuma Naoki , Tashiro Koichiro , Katsunori Kakumoto Katsunori Kakumoto , Yukio Takano Yukio Takano
Published: October 2002

Deep levels are found in n-type silicon that is annealed in N2 and quenched to room temperature. The energy level and capture cross section of the deep levels are estimated to be about E
c-0.42 eV and of the order of 10-17 cm2, respectively. The charge state of the deep levels is determined to be acceptor type by measuring the temperature dependence of the Schottky junction capacitance made in the specimen with the deep levels. The depth profile of the deep level density is found to correspond to that of the complementary error function, and the diffusion coefficient calculated from the profile is in good agreement with that of nitrogen in silicon. It is assumed that generation of deep levels is due to the formation of nitrogen-vacancy complexes, because quenching to room temperature and several hours' storage after quenching are required to form the deep levels. In order to confirm this assumption, we attempted to control the deep level density by changing the vacancy concentration. Oxidation of the specimen surface and formation of oxygen precipitates in silicon are known to decrease the vacancy concentration, since they supply excess interstitials from the oxide and silicon interface. Experimental results clearly show that the deep level density observed in these specimens is very low.
Functionally Gradient NiTi Films Fabricated by Sputtering
Authors: Takabayashi Sotohiro , Tanino Katsumi , Fukumoto Shigeru , Mimatsu Yoshitugu , Yamashita Shinya , Ichikawa Yoshio
Published: October 2002

The processing of homogeneous NiTi film has already been reported, but not that of heterogeneous NiTi film. The deposition and processing of functionally gradient films (FGF) of NiTi are discussed and demonstrated. NiTi-FGF were fabricated by RF magnetron sputtering with control of the input power to a titanium target. Films were heat-treated to induce crystallization and memorization. The characteristics have been investigated using a differential scanning calorimeter (DSC) and an electric resistance meter, respectively. The films that were solution-treated at 700° C had a gradient composition, and they showed two types of crystal structure, namely, a nickel-rich layer and a titanium-rich layer in the film. The entire NiTi-FGF transformed gradually and the temperature range between the start and finish of transformation was twice that of homogeneous film. It was verified that motion of FGF could be controlled easily by current intensity.
Comparative Study of C–V and Transconductance of a Si δ-Doped GaAs FET Structure
Authors: Suzuki Takamasa , Katsuno Motonari , Goto Hideo , Sawaki Nobuhiko , Ito Hiroshi , Hara Kunihiko
Published: October 2002

Anomalous peaks/dips have been found in the transconductance vs gate voltage characteristics of a Si δ-doped GaAs FET (Field Effect Transistor) at 4.2 K. Comparing the characteristics with the C-V concentration as a function of the gate voltage, the origin of the oscillatory behaviour is attributed to the intersubband scattering in the δ-doped layer.
Strain Effects on Interdiffusion in InAs 1-xPx/InP Heterostructures
Authors: J. Tweet Douglas , Hirofumi Matsuhata Hirofumi Matsuhata , Ryu Shioda Ryu Shioda , Hiroyuki Oyanagi Hiroyuki Oyanagi , Hidenori Kamei Hidenori Kamei
Published: October 2002

Using X-ray diffraction and transmission electron microscopy we have found that InAs1-x
Px films deposited on InP(001) substrates with organometallic vapor phase epitaxy grow in an unusual island growth mode characterized by large strain-dependent interdiffusion. Initially, strong interdiffusion occurs between the overlayer and the substrate, producing pseudomorphic islands of higher than intended P composition. These grow only until some point in the relaxation process, possibly a critical value of the strain, after which islands of the intended composition begin to appear. Furthermore, the islands are found to penetrate deeply into the substrate. The resulting phase separation is thus caused by strain-enhanced interdiffusion, and is unrelated to that due to spinodal decomposition in other compound semiconductor systems.
High-Performance Au/Ti/Ge/Pd Ohmic Contacts on n-Type In 0.5Ga 0.5P
Authors: Chai Chun-Yi , Wu Janne-Wha , Guo Jan-Dar , Huang Jung-A , Lai Yong-Lin , Chan Shih-Hsiung , Chang Chun-Yen , Chan Yi-Jen , Huang-Chung Cheng Huang-Chung Cheng
Published: October 2002

High-performance Au/Ti/Ge/Pd ohmic contacts on n+-In0.5Ga0.5P have been fabricated for the first time. Using an n+-In0.5Ga0.5P epitaxial layer grown by low pressure metalorganic chemical vapor deposition (LP-MOCVD) with a Si dopant concentration of about 2×1018 cm-3, the minimum specific contact resistivity is as low as 1.2×10-5 Ω·cm2, which is much lower than that of AuGeNi contacts after rapid thermal annealing at 400°C for 60 s. The thermal stability of the Au/Ti/Ge/Pd system is significantly higher than that of conventional AuGeNi due to the introduction of the Ti barrier layer. Many holes and islands are observed on the surfaces of samples annealed at high temperature. The outdiffusion of P from the decomposed In0.5Ga0.5P substrate and agglomeration of Pd and Ge are the primary causes of contact degradation.
Direct Determination of Relaxation Parameters in Deep-Level Transient Spectroscopy Experiments
Authors: Alejos Óscar , Francisco Carlos de , Herná Pablo , Maríoz José , José Vicente José Vicente , Lourdes Enrí Lourdes Enrí
Published: October 2002

A robust technique for deep-level transient spectroscopy is presented. The method is based on a single temperature scan of capacitance transients. The relaxation parameters, energy trap level, amplitude and pre-exponential factor, can be directly computed from experimental data by means of a set of closed-form expressions. The usefulness of this method is tested by analyzing the deep-level signal on a palladium-doped silicon diode
In Situ Extended X-Ray Absorption Fine Structure Study on the Local Structure around Gallium in Liquid Silicon
Authors: Shinohara Armando Hideki , Omote Kazuhiko , Waseda Soroku Kawanishi
Published: October 2002

The local structure around gallium of 0.5, 1 and 5 at.% in liquid silicon at 1440° C has been investigated by the extended X-ray absorption fine structure (EXAFS). The amplitude of EXAFS oscillations is distinct for the very dilute case of 0.5 at.% gallium. The EXAFS analysis shows that the structural parameters of Ga–Si pairs change from 2.8 atoms at a distance of 2.36 Å to 2.1 atoms at a distance of 2.43 Å with increasing gallium content in liquid silicon. These results suggest that a certain local structure around gallium in liquid silicon is formed at low gallium content and that this structural feature disappears with increasing gallium content.
Effect of Na2O Addition to Ag2O-Doped Phosphate Glasses on Enhancement of Silver Particle Precipitation by Low-Energy Ion Irradiation
Authors: Kitazawa Nobuaki , Yano Tetsuji , Shuichi Shibata Shuichi Shibata , Masayuki Yamane Masayuki Yamane
Published: October 2002

The precipitation of Ag particles in x Na2O– yAg2O– zAl2O3–(1- x- y- z)P2O5 glasses was studied. The volume fraction of quantum-size Ag precipitates was enhanced by nitrogen ion irradiation at room temperature. Ion-irradiation-enhanced precipitation was observed up to a distance of 80 nm from the glass surface. In the absence of Na2O (x=0), Ag was selectively sputtered by the nitrogen ion flux. In glasses containing Na2O, irradiation-induced Ag removal could be suppressed and the amount of precipitates increased. The third-order nonlinear optical susceptibility, χ(3), of the irradiated glasses was estimated to range from 5.5 to 8.8×10-7 esu. The large susceptibilities are consistent with the large amount of Ag precipitates. The irradiation-induced decomposition of Ag2O and Na2O is one possible precipitant-forming mechanism.
Rheological Observation of a New Weak Gel in Agarose Solution
Authors: Satoshi Itou Satoshi Itou , Tatsuya Miyatani Tatsuya Miyatani , Junji Takeuchi Junji Takeuchi , Ken-ichi Tozaki Ken-ichi Tozaki
Published: October 2002

We have found a very weak gel (VWG) state in agarose solution. The VWG was distinguishable from a normal gel due to the following two differences. 1. The VWG has a very low shear modulus (below 10-2 Pa), with slight temperature dependence. 2. The VWG did not react with iodostarch, whereas the ordinary gel did. The viscosity and shear modulus were measured using a new instrument under very low constant shear stress (min., 10-4 Pa). Application of low stress made it possible to distinguish the VWG from the sol state.
Crystal Structure of (NH 4) 3H(SO 4) 2 in Phase I
Authors: Takanori Fukami Takanori Fukami , Keizo Horiuchi Keizo Horiuchi , Keiko Nakasone Keiko Nakasone , Kazuo Furukawa Kazuo Furukawa
Published: October 2002

The crystal structure of triammonium hydrogen disulfate (NH4)3H(SO4)2 in phase I has been studied by single-crystal X-ray diffraction. The space group is assigned as trigonal R\overline3, and the structure parameters are determined. The difference in the structural changes of (NH4)3H(SO4)2 and (NH4)3H(SeO4)2 at the ferroelastic-superionic phase transition is discussed.
Current vs Voltage Characteristics of Al–Al 2O 3–Pd Tunnel Junction Hydrogen Sensor
Authors: Sumio Okuyama Sumio Okuyama , Katsuro Okuyama Katsuro Okuyama , Nobuyuki Takinami Nobuyuki Takinami , Koichi Matsushita Koichi Matsushita , Yasuji Kumagai Yasuji Kumagai
Published: October 2002

The conduction mechanism of an Al–Al2O3–Pd MIM (metal-insulator-metal) junction which can operate as a hydrogen gas sensor was investigated using the logarithmic derivative of the current curve, Fowler-Nordheim plot and temperature dependence of the junction current. Al–Al2O3–Pd junctions showed current-voltage characteristics typical of tunneling conduction at voltages above 3 V. The barrier height of the Pd-Al2O3 contact obtained from the position of the logarithmic derivative maximum of the current was 3.4 eV in vacuum, and decreased to 2.7 eV upon introduction of 40 Pa hydrogen. On the other hand, the barrier height of the Al–Al2O3 contact was 1.8 eV in vacuum and was unchanged even when 40 Pa of hydrogen gas was introduced.
Monte Carlo Simulation for Auger Depth Profiling of GaAs/AlAs Superlattice Structure by Ar+ Ion Sputtering
Authors: Lee Hyung-Ik , Shimizu Ryuichi , Inoue Masahiko , Kajiwara Kazuo , Siegfried Hofmann Siegfried Hofmann
Published: October 2002

A dynamical Monte Carlo simulation including surface recession has been performed to understand the internal atomic mixing process in Auger depth profiling of a GaAs/AlAs superlattice with Ar+ ion sputtering. Results obtained for 1.0 keV Ar+ at an incidence angle of 80° show that the sputtering rates in AlAs layer and GaAs layer are almost the same and the depth resolutions at the GaAs/AlAs interface in the Al depth profile are 2.9 nm and 3.8 nm for low-energy (68 eV) and high-energy (1396 eV) Al Auger peaks, respectively. Although these values are slightly larger than those obtained from experiments, the present model describes the atomic mixing process during sputter depth profiling with considerable success.
Dependence of Characteristics of Br-Type Magnetically Insulated Diode on Configuration of Insulating Magnetic Field
Authors: Chishiro Etsuji , Matsuyama Akira , Katsumi Masugata Katsumi Masugata , Kiyoshi Yatsui Kiyoshi Yatsui
Published: October 2002

Characteristics of B

r
-type magnetically insulated diode have been evaluated for two types of insulating magnetic field geometry. For type 1, where the magnetic flux of the B

r
-field is constant in radius and magnetic field lines are almost parallel to the anode surface, the diode turns on with large delay time. For type 2, where magnetic flux increases with radius, initial irradiation of electrons on the anode occurs in early pulse, which helps to produce anode plasma and reduces turn-on delay. High-efficiency beam generation has been observed in type 2. Using single-particle simulation, the dependence of the characteristics of electron irradiation on the anode was estimated, and the results qualitatively agree with those of the experiment. Beam divergence and deviation angles were measured using a multipinhole energy spectrometer, and no clear difference was observed between the two types of field geometry.
Time-Resolved Observation of Laser-Induced Surface Reaction for Si/Cl2 System Using Second-Harmonic Generation
Authors: Haraichi Satoshi , Sasaki Fumio , Kobayashi Shunsuke , Masanori Komuro Masanori Komuro , Toshiro Tani Toshiro Tani
Published: October 2002

Laser-induced surface reaction for the Si(111)/Cl2 system has been observed using second-harmonic generation (SHG). Chlorine gas molecules are introduced to the clean Si surface and their adsorption, desorption and reaction are indirectly measured by surface SHG. In the case of Nd:YAG laser measurement, SHG output decays rapidly with exposure to Cl2 and is recovered by pump beam irradiation with a power of 65 mJ/pulse. Cl coverage can be estimated from SHG intensity and we determine the mean residence times of adsorbed Cl to be 300 ns and 11.4 s with and without pump beam exposure, respectively, at a sample temperature of 180° C. In the case of Ti-sapphire laser measurement, SHG outputs increase and decay rapidly with exposure to Cl2 as measured by 800 nm and 1300 nm probe beams, respectively.
Verification of Sheath Potential of Processing Plasma in an Electron-Beam-Excited Plasma Apparatus Using a Current Balance Equation
Authors: Miyano Ryuichi , Izumi Shinya , Kitada Ryouji , Fujii Motoyuki , Ito Shunjiro Ikezawa
Published: October 2002

High-density reactive processing plasmas are used to fabricate new materials in electron-beam-excited plasma (EBEP) apparatus, and sheaths have become important in processing plasmas because an ion sheath surrounds the substrates. In order to determine the relationship between the sheath potential and the electron energy distribution function (EEDF), the measured sheath potentials are compared with those calculated using a theoretical current balance equation at the sheath edge in the EBEP, using the experimentally obtained parameters. The results show that monochromatic electron beam current is assumed, and that the profile of the sheath potential depends on the beam potential (E
b') at the sheath edge in the plasma.
Simulation of a Pulse Time-Modulated Bulk Plasma in Cl2
Authors: Yokozawa Ayumi , Hiroto Ohtake Hiroto Ohtake , Seiji Samukawa Seiji Samukawa
Published: October 2002

A simulation of a time-modulated (TM) ECR plasma in Cl2 is presented. The behavior of electrons in the bulk plasma is simulated by taking account of diffusion of electrons from the ECR region and confinement of electrons by the sheath electric field. The positive and negative ion densities are deduced from the total number of collisions of ionization, attachment, and detachment by electrons. A simulation is performed for a plasma with a pressure of 2 mTorr, microwave power of 500 W and a pulse duration time of 100 µ s. The calculated time constants of the electron density and temperature, and the saturation current ratio between the positive ions and electrons agree well with the results of probe measurements. The positive ion density shows little time variation. The negative ion density decreases in the power-on period because electron detachment from negative ions increase due to high energy electrons diffusing from the ECR region, but in the power-off period, the negative ion density significantly increases since attachment collisions increase as the electron temperature decreases. This variation in the negative ion density corresponds to the variation in etching rate of Si with pulse interval observed in a previous experiment. This indicates that negative ions contributes to the etching reaction in a TM Cl2 plasma.
SiO2 Etching Employing Inductively Coupled Plasma with Hot Inner Wall
Authors: Chinzei Yasuhiko , Ichiki Takanori , Kurosaki Ryo , Kikuchi Jyun , Ikegami Naokatsu , Fukazawa Takayuki , Shindo Haruo , Yasuhiro Horiike Yasuhiro Horiike
Published: October 2002

The selective etching of SiO2 on Si employing C4F8/H2 inductively coupled plasma (ICP) was studied based on measurements of radical and ion densities, flow rate and wall temperature. Since polymer films were not deposited when the reacter wall was heated to temperatures above 200° C, CF1 radical density at 200° C was one order higher than that at the wall temperature of 30° C. Thus both Si and SiO2 etch rates decreased rapidly with increasing H2 concentration in C4F8, and Si etching stopped at 15% H2. The etch stop was attributed to insufficient removal of polymer with a reduced amount of ions and was suppressed considerably by increasing the RF power to generate a large amount of ions. The use of poly-Si masks reduced the microloading effect in comparison to resist masks and a contact hole feature with 0.2 µ m size and aspect ratio of 6 was successfully obtained.
Characterization of Stable Fluorine-Doped Silicon Oxide Film Prepared by Biased Helicon Plasma Chemical Vapor Deposition
Authors: Tamura Takahiro , Inoue Youichi , Satoh Makoto , Hikaru Yoshitaka Hikaru Yoshitaka , Junro Sakai Junro Sakai
Published: October 2002

Fluorine-doped silicon oxide (SiOF) film prepared by biased helicon plasma chemical vapor deposition with SiF4 and O2 is characterized. In this characterization, the SiOF film is compared with that prepared using a nonbiased plasma. SiOF films prepared using a biased plasma are stable in air. Whereas films prepared using a nonbiased plasma are not stable in air and the relative dielectric constant and stress vary in the ranges 3.2 to 3.5 and from -35 MPa to 0 MPa, respectively. Analysis Fourier transform infrared (FT-IR) and thermal desorption mass spectroscopy (TDS) spectra, clarifies the following. (1) Si-F bonds are formed in SiOF films prepared using a biased plasma. (2) Not only Si-F bonds but also F-Si-F bonds are formed in SiOF films prepared using a nonbiased plasma. (3) The F-Si-F bond structure formed in SiOF films absorbs water easily.
Reaction Mechanism and Electrical Properties of (Ba,Sr)TiO3 Films Prepared by Liquid Source Chemical Vapor Deposition
Authors: Yamamuka Mikio , Kawahara Takaaki , Akimasa Yuuki Akimasa Yuuki , Kouichi Ono Kouichi Ono
Published: October 2002

The reaction mechanism in liquid source chemical vapor deposition (CVD) of (Ba,Sr)TiO3 [BST] films has been studied using dipivaloylmethanato (DPM) source materials. Effects of substrate temperature and deposition atmosphere on film characteristics were investigated, such as deposition rate of each source material, step coverage, and electrical properties of the film deposited. The decomposition of DPM source materials for BST film deposition was found to be enhanced in O2 atmosphere, as compared with that in N2 atmosphere. Furthermore, the source materials were easier to decompose at higher substrate temperatures. The BST film step coverage became less conformal at higher temperatures and in O2 atmosphere, implying that more precursors with large sticking probabilities were produced therein. Although O2 gas was not necessary to form the BST crystalline structure and to improve the step coverage, the addition of O2 during deposition was found to be necessary to improve the crystallinity and electrical properties of CVD-BST films.
A Fabrication Process of Self-Aligned Tantalum-Silicide Gate Gallium-Arsenide Metal-Semiconductor Field Effect Transistors with Tantalum-Silicide Cap-Annealing Technique
Authors: Hsu Wan-Thai , Tu Chuan-Cheng , Chen Wei-Su , Fon-Shan Huang Fon-Shan Huang
Published: October 2002

The tantalum silicide ( TaSi

x

) was investigated for the application of self-aligned gate (SAG) GaAs metal-semiconductor field-effect transistors (MESFET). TaSi

x

film was deposited by sputtering with substrate bias from -100 V to +75 V. The optimal condition of substrate bias voltage is +50 V for MESFET process according to AES, XRD, and resistivity analysis. The Si+ implantation at 80 keV with dose 4×1013 cm-2 through thin TaSi

x

film was adopted for the channel doping. For the gate patterning, reactive ion etching (RIE) of TaSi

x

was performed in CF4+O2 (15% O2) mixture at total pressure 40 mTorr with RF power 60 W. A 2 µ m×50 µ m TaSi

x

SAG GaAs MESFET was then successfully fabricated. In this process, the TaSi

x

film was used for the gate material, encapsulating layer, and film for through implantation. This new method simplifies the fabrication process of self-aligned GaAs MESFET.
Second-Harmonic Generation in Vertical-Cavity Surface-Emitting Laser
Authors: Yamada Norihide , Ichimura Yoshikatsu , Nakagawa Shigeru , Kaneko Yasuhisa , Tetsuya Takeuchi Tetsuya Takeuchi , Nobuo Mikoshiba Nobuo Mikoshiba
Published: October 2002

A concept for a short-wavelength compact laser is proposed, in which second-harmonic coherent light is produced by converting fundamental light lased in a vertical-cavity surface-emitting laser. A layer is incorporated inside the laser cavity particularly for efficient second-harmonic generation. This layer consists of second-order optical nonlinear crystals which are preferably III–V- or II–VI-system compound semiconductors epitaxially grown with crystal orientation tilted from <100>. Simulation indicates that the device will produce several hundred µ W with AlAs/GaAs alternating layers for second-harmonic generation and an InGaAs active layer for lasing.
Composition Control of Lead Zirconate Titanate Thin Films in Electron Cyclotron Resonance Plasma Enhanced Chemical Vapor Deposition System
Authors: Kim Jae-Whan , Shin Joong-Shik , Wee Dang-Moon , Kwangsoo No Kwangsoo No , Won-Jong Lee Won-Jong Lee
Published: October 2002

Lead zirconate titanate (PZT) thin films were fabricated on Pt/Ti/SiO2/Si substrates by electron cyclotron resonance plasma-enhanced chemical vapor deposition (ECR-PECVD). Lead β-diketonate ( Pb(DPM)2, zirconium t-butoxide ( Zr(OC4H9)4) and titanium i-propoxide ( Ti(OC3H7)4) were used as metalorganic (MO) precursors. Perovskite single-phase PZT films were obtained at temperatures below 500° C when the Pb/(Zr+Ti) concentration ratio was close to 1. The cation concentrations in the PZT films were successfully controlled by adjusting the flow rate of each MO source. The variation in composition and structure with the process temperature and the MO source flow rates was discussed.
Preparation of Ordered Vacancy Chalcopyrite Thin Films by RF Sputtering from CuInSe2 Target with Na2Se
Authors: Tanaka Tooru , Demizu Yasutaka , Yamaguchi Toshiyuki , Akira Yoshida Akira Yoshida
Published: October 2002

A new method for preparation of ordered vacancy chalcopyrite (OVC) thin films by rf sputtering is presented. From X-ray diffraction analyses, all thin films prepared from a CuInSe2 and Na2Se mixture target with [Na]/[CuInSe2] ratio above 1% show an OVC structure, and the lattice parameters of the thin films are slightly smaller than that of CuInSe2, suggestive of the OVC model. The optical absorption coefficients above the fundamental band edge exceed 3×104 cm-1 and the optical band gap increases from 1.02 eV to 1.33 eV with increasing [Na]/[CuInSe2] ratio from 0% to 10% in the target.
Search for Time-Correlated Fast Neutrons from DD Fusion at Room Temperature
Authors: Choi Eunjoo , Ejiri Hiroyasu , Hideaki Ohsumi Hideaki Ohsumi , Tadafumi Kishimoto Tadafumi Kishimoto
Published: October 2002

A time-correlated spectrum of fast neutrons from the electrochemically loaded Pd-D system was measured by a low-background high-resolution Ge detector surrounded by neutron scatterers. Time correlation of fast neutrons was obtained by measuring the time correlation of γ-rays following inelastic scattering of fast neutrons. The measurement shows no evidence for neutron burst during the electrolysis of the Pd-D system at room temperature.
Decomposition of Chlorofluorocarbon by Pulse High-Current Discharge and Fast Burning through Spark Discharge
Authors: Nakagawa Yoshiro , Singo Adachi Singo Adachi , Akito Kohchi Akito Kohchi
Published: October 2002

Decomposition of Freon-12 by pulse high-current discharge (100 kV, 60 kA, 1 µ s, stored energy, 3.6 kJ) and by fast burning through spark discharge was compared. Freon-12 of pressure 60–160 mmHg was decomposed with an efficiency of about 14 nmol/J by applying an pulse-discharge. With addition of 30% each of hydrogen and oxygen to Freon-12, the efficiency of decomposition for the first shot was remarkedly increased to 118 nmol/J. Further increase in the concentration of hydrogen and oxygen led to fast burning through electric spark discharge in the mixture of hydrogen (200 mmHg), oxygen (100 mmHg) and Freon (100–300 mmHg). The efficiency of decomposition for the spark discharge (stored energy; 0.23 J) was 1.4×107 nmol/J, which was 106 times larger than the efficiency of the pulse high-current discharge. The reaction process was estimated from the decomposition products such as CO2, CO, HCl and large molecules containing C, Cl, and F, which were measured by a quadrupole mass analyzer and an infrared spectrophotometer.
Parameter Change of Magneto-Plasma-Dynamic Arc-Jet Plasma on a Flow-Facing Plate
Authors: Ishiyama Osamu , Tamura Hideki , Akira B. Sawaoka Akira B. Sawaoka , Masanari Tamaru Masanari Tamaru
Published: October 2002

Electron temperature and density of plasma flow, which was obtained from a magneto-plasma-dynamic (MPD) arc jet, were measured by the triple-probe method. In order to apply the MPD arc jet to thin-film processing, the changes in the plasma parameters on a processing substrate were investigated.
Use of Langmuir Probe in an Electron Plasma
Authors: Akira Tsushima Akira Tsushima
Published: October 2002

Probe measurement in an electron plasma is discussed in terms of a potential distribution near a biased electrode and a probe current. Results of an experiment are also shown.
X-Ray Mask Distortion Induced in Back-Etching Preceding Subtractive Fabrication: Resist and Absorber Stress Effect
Authors: Shinji Tsuboi Shinji Tsuboi , Yoshio Yamashita Yoshio Yamashita , Tadashi Matsuo Tadashi Matsuo , Tsuneaki Ohta Tsuneaki Ohta , Tsutomu Shoki Tsutomu Shoki , Takuya Yoshihara Takuya Yoshihara , Takao Taguchi Takao Taguchi , Soichiro Mitsui Soichiro Mitsui , Shuichi Noda Shuichi Noda , Kazuo Suzuki Kazuo Suzuki , Hiroshi Hoga Hiroshi Hoga , Yoh-ichi Yamaguchi Yoh-ichi Yamaguchi , Katsumi Suzuki Katsumi Suzuki
Published: October 2002

The influence of resist and absorber stress distributions on X-ray mask distortion induced during back-etching preceding subtractive fabrication is analyzed experimentally and simulated. The stress distribution (gradient) in a resist and/or that in an absorber film causes larger pattern displacement rather than the film average stress. Some resists have considerably high stress after coating on a wafer, and this stress also changes during exposure, causing local pattern displacements. However, use of chemically amplified resist systems, in which the reaction after exposure is limited to a small amount acid generation, might solve this problem. Low-stress positive-tone resists should thus be developed.
Fast Proximity Corrections for Electron-Beam-Fabricated High Resolution and High-Aspect-Ratio Fresnel Zone Plate
Authors: Di Fabrizio Enzo , Grella Luca , Baciocchi Marco , Gentili Massimo , Peschiaroli Daniela , Luigi Mastrogiacomo Luigi Mastrogiacomo , Romano Maggiora Romano Maggiora
Published: October 2002

Fast proximity corrections for electron beam (e-beam) patterning with circular symmetry are implemented. Calculations are applied particularly to the Fresnel zone plate (FZP). Considerable reduction of numerical data is obtained by exploiting the symmetry of the FZP; the typical calculation time for a FZP with 300 zones is of the order of 30 min. Two accelerating voltages, 40 keV and 50 keV, were used to test the reliability of proximity corrections. It was demonstrated that in both cases, proximity corrections are necessary; at 40 keV, FZPs with 0.1 µ m resolution and high aspect ratio of 5 were fabricated, whereas at 50 keV, a resolution of 70 nm and high aspect ratio greater than 7 was attained. Comparison between experimental and theoretical evaluations of parameters related to the optical efficiency of the FZP, such as, zone line-width accuracy and line/space ratio, reveal them to be very close to their ideal values. According to an accurate metrological study by means of a scanning electron microscope (SEM), the zone line-width errors are within the SEM measurement accuracy where that for the outermost zones (line-widths between 70 nm and 100 nm) is better than 10 nm.
Raman Scattering Study of Boson Peak in Barium Borate Glass
Authors: Kodama Seiji Kojima
Published: October 2002

The borate anomaly in barium borate glass was studied using Raman scattering spectroscopy. The main features of the the boson peak were reproduced by the disorder induced model with an exponential correlation function. An additional peak appears in the shoulder of the boson peak at about 210 cm-1, and increases in intensity markedly above x
m=0.32, where the sound velocity shows a maximum. The obtained intermediate correlation length l
c is nearly equal to the Ba-Ba distance. The dependence of internal vibration modes on the composition of barium was also studied.
Conducting Polypyrrole-Silica Glass Composite Films Prepared by Electrochemical Polymerization
Authors: Onoda Mitsuyoshi , Tetsuro Matsuda Tetsuro Matsuda , Hiroshi Nakayama Hiroshi Nakayama
Published: October 2002

The electrochemical behavior of the exchange process for dopant anions in polypyrrole (PPy)-silica glass composite film in acetonitrile solution was analyzed by cyclic voltammetry. This film can be simply prepared by carrying out the electrochemical polymerization of PPy simultaneously with the synthesis of silica glass by means of sol-gel processing. It was found that dopant anions in the PPy-silica glass composite film could be exchanged relatively easily with electrolyte anions in acetonitrile solution by potential sweeping. However, dopant anions in the PPy film could not be easily exchanged in acetonitrile solution. Application of this new type of PPy-silica glass composite film to the ionic sensor which responds to specific ions has also been proposed.
Reflection of Plane Acoustic Waves at a Seawater-Marine Sediment Interface
Authors: Masao Kimura Masao Kimura
Published: October 2002

The dependence of reflection coefficients on the angle of incidence and the frequency, for the three typical kinds of marine sediments-silt, very fine sand, and medium sand, is calculated using the Biot-Stoll model. The effects of frequency on the angle of incidence characteristics are investigated and the difference between the frequency characteristics of the reflection coefficients for silt and for sand is demonstrated.
Power Durability of Highly Textured Al Electrode in Surface Acoustic Wave Devices
Authors: Matsukura Noritsugu , Kamijo Atsushi , Ootsuka Eiichi , Takahashi Yoshihiro , Sakairi Natsuhiko , Yamamoto Yasushi
Published: October 2002

Highly textured Al[111] films have been grown on an ultrathin metal underlayer by ion-beam sputtering technique regardless of substrate material and its cutting angle. Surface acoustic wave filters with the highly textured Al[111] electrodes were fabricated and the power durability was investigated. They have lifetimes more than 3000 times longer than those with evaporated polycrystalline Al electrodes.
Damped Capacitance Elimination in Piezoelectric Vibrator Using Operational Amplifier Circuit
Authors: Yoshiro Tomikawa Yoshiro Tomikawa , Chiharu Kusakabe Chiharu Kusakabe , Kazumasa Ohnishi Kazumasa Ohnishi , Katsutoshi Sakurai Katsutoshi Sakurai , Masayuki Tanaka Masayuki Tanaka
Published: October 2002

We discuss the elimination of damped capacitance from the equivalent circuit of a piezoelectric vibrator, which is achieved using an operational amplifier circuit. First, we describe the theoretical principle of a basic damped capacitance elimination circuit, and then report the experimental investigation of the circuit. We conclude that the circuit proposed here is very effective in eliminating the damped capacitance in a piezoelectric vibrator and therefore the range of application of vibrators can be increased.
New Ultrasonic Level Gauge Using Standing Waves of Bending Modes
Authors: Soramoto Seiki , Sato Michio , Ito Toshiaki , Yamaguchi Shin-ichi , Nagasaka Tokiyoshi , Yamada Ken , Nakamura Kiyoshi
Published: October 2002

A new ultrasonic level gauge using standing waves of bending modes has been developed. This level gauge is based on the variation of the resonance frequencies of a waveguide rod immersed in the water. In this paper, the principle and the fundamental experiments are reviewed, and the feasibility of the new ultrasonic level gauge is demonstrated.
Ultrasonic 3-Dimensional Range-Variant Inverse Filtering in Near-Field Range of Array Transducer
Authors: Kazuhide Kimizuka Kazuhide Kimizuka , Shin-ichi Yagi Shin-ichi Yagi
Published: October 2002

One aim of recent ultrasonic tissue characterization is the quantitative imaging of tissue acoustic parameters. In order to obtain a straightforward image of physical constants the range-variant acoustic field characteristics, such as grating lobe, prefocused beam and diffraction effect due to the finite aperture on the array transducer have to be corrected. We propose 3-dimensional range-variant Gaussian shaped inverse filtering by digital signal processing of complex echoes as a means of correcting these characteristics in the near-field range of an ordinary array transducer .
Low-Temperature Elastic Moduli and Dilational and Shear Internal Friction of Polycarbonate
Authors: Mikio Fukuhara Mikio Fukuhara , Asao Sampei Asao Sampei
Published: October 2002

Longitudinal and transverse wave velocity, and five kinds of elastic parameters (Young's, shear and bulk moduli, Lamè parameter, Poisson's ratio) for polycarbonate were simultaneously measured over a temperature range of 68 to 434 K, using the ultrasonic pulse method. All elastic moduli decrease with increasing temperature, suggesting the lowering of molecular bonding strength, accompanied by fluctuation of density due to loosely packed chains. From dilational and shear internal frictions, the 201, 313, 359 K peaks, an abrupt increase from 421 K and a decrease to 148 K are interpreted as free motion of carbonate group in the main chain (γ dispersion), motion of molecular chains between weak intermolecular bonds (β dispersion), dipole-dipole association between ester side chains (β' dispersion), glass transition (α dispersion) and a δ peak, respectively.
Derivation of a Force Factor Equation for a Langevin-Type Flexural Mode Transducer
Authors: Yoshikazu Koike Yoshikazu Koike , Takeshi Tamura Takeshi Tamura , Sadayuki Ueha Sadayuki Ueha
Published: October 2002

We propose a calculation method for the force factor of a Langevin-type flexural mode transducer. In this proposed method, after calculating the flexural vibration mode and the resonance frequency using the analytical solution given by Miklowitz for the Timoshenko beam theory, the force factor is calculated by substituting the obtained vibration distribution into the piezoelectric equation. In the calculation of vibration distribution, piezoelectric elements bound by metal blocks are considered using the matrix expression of the Miklowitz solutions. Differences between calculation results and measurements are within 35% for several bonded transducers. Therefore, this calculation method is useful for the design of Langevin-type flexural mode transducers.
Precipitation of Cu and Fe in Dislocated Floating-Zone-Grown Silicon
Authors: Shen Bo , Sekiguchi Takashi , Zhang Rong , Shi Yi , Shi Hongtao , Yang Kai , Zheng Youdou , Sumino Koji
Published: October 2002

Precipitation behaviors of Cu and Fe in dislocated Floating-zone-grown silicon crystals are investigated by means of transmission electron microscopy (TEM) and the electron-beam-induced-current (EBIC) technique. Cu precipitation on dislocations is affected significantly by the cooling rate of a specimen after contamination. Cu develops precipitate colonies at some special sites on dislocations and does not decorate other parts of dislocations if the specimen is cooled slowly. These preferential precipitation sites are suggested to be non-dissociated edge-type dislocation segments. The fast cooling of a specimen leads to that Cu precipitates on all of dislocations. Fe decorates all of dislocations uniformly, irrespective of the cooling rate of a specimen.
Evaluation of GaAs Wafer Using Noncontact Capacitance/Voltage Measurement
Authors: Sakai Takamasa , Kohno Motohiro , Hirae Sadao , Nakatani Ikuyoshi , Hideaki Matsubara Hideaki Matsubara , Tatsufumi Kusuda Tatsufumi Kusuda
Published: October 2002

A new noncontact capacitance/voltage ( C–V ) measurement technique which enables the application of semiconductor materials without insulator film on the surface is introduced. The applicability of this technique has been verified by measuring oxidized silicon wafers whose characteristics were well investigated. Based on the general theory of metal-oxide-silicon (MOS) system, the derivation of ideal C–V curves under various conditions was discussed for the analysis of the measured C–V curves. Then, GaAs wafers subjected to various processing steps were evaluated. The behaviors of the measured C–V curves not only agreed with the results reported earlier but led to detection of the thermal annealing effect of the interface traps at low temperature. Furthermore, the ionized impurity concentration was determined from the (1/C)2 plots and the inversion capacitance, and it was found that the difference between their determined values was related to the density of the bulk traps.
Growth and Characterization of High-Speed Carbon-Doped-Base InP/InGaAs Heterojunction Bipolar Transistors by Metalorganic Chemical Vapor Deposition
Authors: Ito Hiroshi , Yamahata Shoji , Shigekawa Naoteru , Matsuoka Kenji Kurishima
Published: October 2002

The dependences of the hole concentration and hydrogenation ratio in C-doped InGaAs on growth parameters such as growth temperature, V/III ratio, and CBr4 flow rate are clarified. The hydrogenation ratio is shown to increase with increasing carbon concentration in InGaAs. Several annealing procedures in different ambients and with different cap layers are examined to establish a procedure to effectively re-activate hydrogenated carbons in InGaAs base of heterojunction bipolar transistor (HBT) structure. It is revealed that the re-hydrogenation of C acceptors at the growth of emitter layer determines the final hole concentration in the base layer. With an annealing in H2 with a growth interruption at the emitter/base interface, an as-grown hole concentration of 1.1×1019/cm3 is obtained in the device structure. An HBT with a 1.6×9.6-µ m2 emitter area exhibits f
T and f
max
values of 185 and 105 GHz.
Analysis of Scattering Light from Magnetic Material with Land/Groove by Three-Dimensional Boundary Element Method
Authors: Ogawa Masatsugu , Nakada Masafumi , Katayama Ryuichi , Mitsuya Okada Mitsuya Okada , Masaki Itoh Masaki Itoh
Published: October 2002

A calculation method with three-dimensional Boundary Element Method (BEM) has been developed for analyzing scattering light from a magnetic material, in order to determine the contribution of land/groove shapes and incident beam polarization to Kerr rotation. A product of scattering beam intensity and the Kerr rotation angle (R·θ
k
) has been calculated in the case that 680 nm wavelength Gaussian beam is focused on 680 nm or 1360 nm width land/groove, which has 85 nm depth or height. The land or groove shapes have been varied from rectangular shapes to V-shapes. Regardless of the land/groove shapes, the R·θ
k
of lands is larger than that of grooves in TM-polarization and smaller in TE-polarization. The results in verification experiments well met the calculated ones, i.e., the carrier level of lands is higher than that of grooves in almost the entire range of recording frequency for TM-polarization light, and it is lower for TE-polarization.
Excellent Emission Characteristics of Tunneling Oxides Formed Using Ultrathin Silicon Films for Flash Memory Devices
Authors: Wang Ping-Wei , Ku Tzu-Kun , Su Huan-Ping , Hong Gary , Huang-Chung Cheng Huang-Chung Cheng
Published: October 2002

A novel technique using oxidized ultrathin rugged polysilicon films on silicon substrates has been appied to significantly improve the tunneling efficiency of thin oxides. As compared with oxidized amorphous silicon films, these rugged polysilicon films can achieve a higher emission current. High-resolution transmission electron microscopy (HRTEM) was used to observe the atomic-scale microtips at the SiO2/Si and polysilicon/ SiO2 interfaces. According to the extracted geometry parameters of the microtips, a two-dimensional numerical simulator based on the finite difference method using the curved emitting surface of microtips can well explain the remarkable current asymmetry of the dielectrics. This suggests that the oxidized rugged polysilicon films can form higher microtips and smaller tip angles, resulting in better emission characteristics that will enable potential applications to future 5-V-only nonvolatile memories.
Imagings of Picosecond-Photoexcited Carriers and Enhanced Auger Recombination Rate by Transient Reflecting Grating Measurements
Authors: Tanaka Takayuki , Akira Harata Akira Harata , Tsuguo Sawada Tsuguo Sawada
Published: October 2002

Photoinduced dynamic processes at a silicon surface were investigated by time-resolved measurements of a transient reflecting grating with 532 nm excitation and detection. The signal caused by photoexcited carriers was separated from signals due to thermal and acoustic effects. The carrier signal was found to be more sensitive to ion induced damages than the thermal and acoustic effect signal. Use of the carrier signal provided an in-plane distribution image of near surface damage induced by helium ion implantation (energy, 200 keV; dose, 1015 atoms/cm2). The cause of the contrast formation was found to be the change of Auger recombination rate γ3. The obtained γ3 for intrinsic silicon was 4.0×10-29 cm6/s which was two orders of magnitude larger than the bulk value. The results indicated defects near the surface region ( ∼100 nm) accelerated γ3.
A Walk-Off Plate for Magneto-Optical Disk System
Authors: Wiechmann Werner , Naoya Eguchi Naoya Eguchi , Shigeo Kubota Shigeo Kubota
Published: October 2002

The application of a birefringent plate to magneto-optical disk readout system is described: The so-called walk-off plate is tilted 45° with respect to an incident converging light beam. Refraction at the crystal surfaces as well as the walk-off effect cause not only separation into an ordinary and an extraordinary polarized light beam, but also beam aberrations such as astigmatism and coma. We utilized beam separation and astigmatism to combine the functions of the polarizing beam splitter and cylindrical optics of a conventional magneto-optical disk system into a single optical element. The comparison between the carrier-to-noise ratios measured when using the conventional readout optics and when employing the birefringent plate indicates that applying the birefringent plate to magneto-optical disk readout systems is feasible.
Scanning Tunneling Microscopy Observation of Copper-Phthalocyanine and Nucleic Acid Base Molecules on Reduced SrTiO3(100) and Cu(111) Surfaces
Authors: Hiroyuki Tanaka Hiroyuki Tanaka , Tomoji Kawai Tomoji Kawai
Published: October 2002

In order to examine how both adsorbed molecules and underlying substrates affect the appearance of scanning tunneling microscopy (STM) images and the arrangement of the molecules on the surface, copperphthalocyanine (CuPc) and the nucleic acid base molecules are deposited on the chemically active reduced SrTiO3(100) √5×√5- R26.6° and chemically less active Cu(111) surfaces. STM images of CuPc and the nucleic acid base molecules on SrTiO3(100) have revealed that the substrate anchors the molecules stably for observation by STM, and each molecule is discriminated according to its shape and size in the image. The molecule of bases adsorbed on the chemically less active Cu(111) surface can diffuse over the surface to self-assemble into novel low-dimensional structures.