bluuebunny/crossref_metadata_2025 huggingface dataset:
Resistivity of Heavily Doped Polycrystalline Silicon Subjected to Furnace Annealing
Authors: Suzuki Kunihiro , Miyata Noriyuki , Kazuo Kawamura Kazuo Kawamura
Published: October 2002

We investigated the dependence of the resistivity of heavily doped polycrystalline silicon (poly-Si) on the doping concentration and annealing conditions. The resistivity of As-doped poly-Si with equal sized grains depends on the annealing temperature when the doping concentration is less than 5×1020 cm-3. This dependence is related to As segregation to the grain boundaries; that is, more As segregates to the grain boundaries as the temperature decreases. When the doping concentration exceeds 5×1020 cm-3, the As concentration in the grain reaches saturation and remains almost constant with increasing temperature. This means that the solid solubility limit is insensitive to the annealing temperature, and the resistivity remains almost constant with increasing annealing temperature. The resistivity of B-doped poly-Si does not depend on the annealing temperature when the doping concentration is less than the solid solubility limit. This indicates that B does not segregate significantly at the grain boundaries. When the doping concentration exceeds the solid solubility limit, the resistivity depends on the annealing temperature, because the solid solubility limit of B depends significantly on the annealing temperature. The solubility limit of B in poly-Si increases from 6×1019 cm-3 at 800° C to 1.5×1020 cm-3 at 1100° C. We proposed an empirical model that explains the experimental data.
Single Junctions in ZnO Varistors Studied by Current-Voltage Characteristics and Deep Level Transient Spectroscopy
Authors: Wang Hsin , Li Wangpei , Cordaro James F.
Published: October 2002

The electronic properties of individual grain boundaries in ZnO varistors were characterized by current-voltage (I-V) measurements and high-temperature zero-bias deep level transient spectroscopy (DLTS). A single-junction electrode pattern was designed using photolithography in order to study these properties. It was found that interface trap energy levels and capture cross sections vary with the polarities of trap filling pulses. The behavior indicates that the grain boundary potential barriers are not symmetric. Asymmetry was also observed inI-Vmeasurements. Intergranular differences in chemical composition, distribution of chemisorbed oxygen, and grain boundary microstructure were suggested to be responsible for the asymmetry in electronic properties.
Strained Lattice Structure Analysis of InGaAsP Multilayers Using Thickness Fringes in Transmission Electron Microscopy Images
Authors: Tsuneta Ruriko , Tsuchiya Tomonobu , Hiroshi Kakibayashi Hiroshi Kakibayashi
Published: October 2002

InGaAsP/InP multilayers were deposited on InP substrates. Multilayer internal stress was controlled by changing the GaAs concentration. The strained lattice structures in InGaAsP/InP multilayers under compresive, tensile, and mixed strain (zero-net strain) are analyzed by using the thickness fringes in bright- and dark-field transmission electron microscope images. The thickness fringe shift near the multilayer/substrate interface shows lattice plane bending in opposing directions for the 0.5% compressive and tensile strained structures. The opposing lattice bending is canceled out in the zero-net strain structure, which results in a transition from cubic to tetragonal lattice distortion in the multilayer. This distortion enlarges the critical thickness to six times that of the compressive or tensile strained structure. The zero-net structure, however, can't maintain greater than ±1.4% strain because the induced stress exceeds the limit of elastic distortion. The influence of strain in these structures, as it corresponds to photoluminescence characteristics is also analyzed.
Breakdown Mechanisms in Pseudomorphic InAlAs/InxGa1-xAs High Electron Mobility Transistors on InP. II: On-State
Authors: Dickmann Jürgen , Schildberg Steffen , Riepe Klaus , Maile Bernd Ernst , Schurr Anton , Arthur Geyer Arthur Geyer , Peter Narozny Peter Narozny
Published: October 2002

A systematic experimental study on the mechanisms inducing device breakdown in the on-state in L
G=0.28µm gate-length pseudomorphic InAlAs/In
x
Ga1-x
As (0.53<x<0.7) high electron mobility transistors (HEMTs) on InP substrate is presented. The study provides comprehensive physical explanation for the mechanisms which limit the breakdown voltage in the open channel condition. The intention of this paper is to provide a profound understanding on the breakdown physics in the on-state of this type of device. From temperature dependent measurements and the evolution of the impact ionization rate as a function of bias we found that in this type of device on-state breakdown is dominated by impact ionization. Thermionic field emission was recognized to be negligible compared to impact ionization. The on-state breakdown voltage drops drastically with increased InAs-mole fraction x. The experimental results also indicate that on-state breakdown occurs in the channel layer. The drain-source breakdown voltages determined at 1% I
DSS where V
DSbr (300 K)=6.8 V, 5.7 V, 4.5 V, 4.1 V, 3.5 V for x=0.53, 0.59, 0.62, 0.65 and x=0.7, respectively.
Current-Voltage and Differential Conductivity-Voltage Measurements in Au/PI/1-Layer Organic Film/Pb Junctions
Authors: Jae Lee Won , Tohru Kubota Tohru Kubota , Mitsumasa Iwamoto Mitsumasa Iwamoto
Published: October 2002

Using polyimide (PI) Langmuir-Blodgett (LB) films as a tunneling barrier, current-voltage (I-V) and differential conductivity-voltage (d2I/dV2-V) characteristics of the junctions incorporating 1-layer organic films were investigated. TheI-Vcharacteristics exhibited a typicalI-Vcharacteristic of ideal tunnel junctions with a noble metal/tunnel barrier/superconductor structure even when the number of deposited PI LB films was less than 10. Several peaks originating in the vibrational modes of the constituent molecules of the 1-layer films were clearly observed in thed2V/dI2-Vcurves. TheI-Vandd2V/dI2-Vcharacteristics of the junctions incorporating a heterostructured film were also examined.
Photoreflectance Study of InP and GaAs by Metal Organic Chemical Vapor Deposition Using Tertiarybutylphosphine and Tertiarybutylarsine Sources
Authors: Kuan Hrong , Su Yan-Kuin , Chang Shoou-Jinn , Wen-Jeng Tzou Wen-Jeng Tzou
Published: October 2002

Two metalorganic sources, tertiarybutylphosphine (TBP) and tertiarybutylarsipe (TBA), have been investigated for their possible use as precursors in the metalorganic chemical vapor deposition (MOCVD) process. The optical properties of epilayers were characterized by photoreflectance (PR) spectra. The V/III ratios were varied at a growth temperature of 600° C and growth pressure of 150 Torr. The broadening parameter Γ of GaAs at 300 K PR was 11.35 meV.
The room-temperature Γ value of InP PR measurement was about 11.46 meV.
Microwave Dielectric Properties and Structure of the Ba6-3xSm8+2xTi18O54 Solid Solutions
Authors: Ohsato Hitoshi , Ohhashi Toshiyuki , Kato Hiromichi , Nishigaki Susumu , Takashi Okuda Takashi Okuda
Published: October 2002

The microwave dielectric properties of the Ba6-3
x

Sm8+2
x

Ti18O54 (0.3≤x≤0.7) solid solutions are studied in relation to the crystal structure. Q·f of suitable materials obtained by optimizing the sintering condition is in inverse proportion to the dielectric constant (ε

r
). With increase of x, ε

r
decreased and Q·f increased. Good-quality microwave resonators with ε

r
=80 and Q·f=9720 GHz can be obtained in the composition range of x=0.5 to 0.7 in the solid-solution region. Substitution of 2Sm3+ for 3Ba2+ in the large cation sites results in the creation of vacancies and crystal distortion, showing that the shrinkage of the TiO6 octahedral site plays an important role for improvement of the microwave dielectric properties.
Photoluminescence of Eu-Doped ZnO Phosphors
Authors: Hayashi Yasufumi , Narahara Hidetoshi , Uchida Teruo , Noguchi Toru , Sumiaki Ibuki Sumiaki Ibuki
Published: October 2002

Characteristic 4f photoluminescence of Eu3+ doped into ZnO was first observed on the red band luminescence. The intensity and fine structures of the Eu3+ luminescence and their temperature dependence are strongly influenced by the doping conditions. In particular, for the increase of the Eu3+ luminescence intensity Li codoping is not effective but stoichiometric control of Zn and O is essential. Moreover, the observed red band luminescence can be considered to be due to excess oxygen.
Novel Europium Complex for Electroluminescent Devices with Sharp Red Emission
Authors: Sano Takeshi , Fujita Masayuki , Fujii Takanori , Hamada Yuji , Shibata Kenichi , Kazuhiko Kuroki Kazuhiko Kuroki
Published: October 2002

A volatile Eu complex, Eu(TTA)3(phen) (TTA=thenoyltrifluoroacetone, phen=1,10-phenanthroline), was synthesized and applied to an electroluminescent (EL) cell structure of [ITO(=indium-tin-oxide)/hole transporting layer/emitting layer (host material=azomethin zinc complex, and dopant= Eu(TTA)3(phen))/MgIn]. The emitting layers were formed by a codeposition technique. A red emission (EL peak wavelength 614 nm) with a very sharp spectral band was observed from the EL cell with 5 wt% Eu(TTA)3(phen), and a maximum luminance of 137 cd/m2 was achieved.
Effects of Titanium Buffer Layer on Lead-Zirconate-Titanate Crystallization Processes in Sol-Gel Deposition Technique
Authors: Aoki Katsuhiro , Fukuda Yukio , Numata Ken , Akitoshi Nishimura Akitoshi Nishimura
Published: October 2002

Effects of the Ti buffer layer on crystallization processes of lead-zirconate-titanate (PZT) films by the sol-gel deposition technique were investigated. The Ti buffer layer was deposited on a Pt/TiN/SiO2/Si substrate by electron beam evaporation at the back-pressure of 1×10-11 Torr. Homogeneous crystalline PZT film of perovskite structure with fine grains were successfully obtained on the substrate with a Ti buffer layer. In contrast, a rosette-structure film which consists of large grains surrounded by a second phase was formed on a pure Pt surface. Ti existing at the interface between Pt and PZT acts as nuclei, and affects the growth of fine grains. Furthermore, leakage current density was drastically reduced from 5×10-5 A/cm2 to 6×10-9 A/cm2 at 4 V for 200-nm-thick film formed on a substrate with a buffer layer. Crystalline orientations and microstructures of PZT films were strongly dependent on the equivalent thickness of the buffer layer and there was an optimum thickness. When the equivalent thickness of the buffer layer was 2 nm, PZT showed <111>-preferred orientation and a homogeneous film structure with fine grains on the <111>-oriented Pt/SiO2/Si substrate.
Measurement of Temperature Behavior of Azimuthal Anchoring Energy at Liquid Crystal/SiO Interface Using New Method
Authors: Iimura Yasufumi , Kobayashi Norihiko , Shunsuke Kobayashi Shunsuke Kobayashi
Published: October 2002

By using a new method, we have measured the temperature dependence of the azimuthal anchoring energy at the interface between the nematic liquid crystal of phenyl-cyanobiphenyl (5CB) and 60° obliquely evaporated SiO film. A detailed comparison of our data with that of Faetti is carried out, and a good agreement between these two sets of data is obtained. This result indicates that the new method is very useful to evaluate the azimuthal anchoring energy at a liquid crystal/solid substrate interface.
(100) Preferred Orientation of Spinel-Type Iron Oxide Films Prepared by Plasma-Enhanced Metalorganic Chemical Vapor Deposition
Authors: Fujii Eiji , Torii Hideo , Tomozawa Atsushi , Takayama Ryoichi , Takashi Hirao Takashi Hirao
Published: October 2002

Spinel-type iron oxide films were prepared on glass substrates at 400° C by plasma-enhanced metalorganic chemical vapor deposition using iron (III) acetylacetonate and oxygen as source gas and oxidizing gas, respectively. The effects of angle (θ) of the source and oxygen gas nozzle to the substrate surface, applied negative dc bias voltage and addition of reducing gas, H2, on the orientation of the films have been investigated. Highly crystalline and (100)-oriented spinel-type iron oxide films were obtained under conventional conditions only when θ was lower than 20°. However, even for θ higher than 20°, highly crystalline and (100)-oriented films could be obtained by applying negative dc bias voltage or adding H2 during the deposition. Magnetic properties and microstructures of the films were also examined.
Effects of Seeding Layer on Orientation and Phase Formation of Sol-Gel-Derived Lanthanum-Modified Lead Zirconate Titanate Films on Glass
Authors: Lee Joon Sung , Kim Chang Jung , Yoon Dae Sung , Choi Chaun Gi , Kwangsoo No Kwangsoo No
Published: October 2002

Sol-gel-derived lanthanum-modified lead zirconate titanate (PLZT) thin films with La/Zr/Ti ratios of 9.5/65/35, 15.5/40/60 and 18/30/70 were prepared on Corning 7059 glass substrates using a seeding layer [PLZT(14/0/100)]. The X-ray diffraction patterns and the microstructures of the films were investigated. The PLZT(9.5/65/35) thin films without the seeding layer consisted of both pyrochlore and amorphous phases. However the PLZT(9.5/65/35) thin films with the seeding layer showed preferred orientation as well as higher perovskite phase content. The orientation of the film varied with the thickness and the heat treatment of the seeding layer. The results will be discussed in terms of the effects of the seeding layer on the orientation and the content of the perovskite phase of the PLZT thin films on glass substrates.
Electrical Properties and Crystal Structure of (Ba0.5Sr0.5)TiO3 Thin Films Prepared on Pt/SiO2/Si by RF Magnetron Sputtering
Authors: Lee Won-Jae , Park In-Kil , Jang Gun-Eik , Ho-Gi Kim Ho-Gi Kim
Published: October 2002

( Ba0.5Sr0.5)TiO3 (BST) thin films have been prepared on Pt/SiO2/Si substrates under various Ar/O2 plasma conditions by the conventional rf magnetron sputtering method using a ceramic target containing excess BaO and SrO. With increasing deposition temperature, the crystallinity of the BST films abruptly increased and change of the preferred orientation was observed. At 650° C, (100)-preferred orientation was obtained. The increase of the crystallinity of films improved the dielectric constant. A 100 nm BST thin film deposited at 650° C with 50% O2 plasma content has a dielectric constant of 725 and a leakage current density of 2.3×10-7 A/cm2 at 2.5 V. In the current-voltage curve of BST film deposited at higher substrate temperature, lower leakage current density in the low bias region and narrower flat region (hopping conduction region) were obtained.
An Improved Method for Determination of Surface Charge Distribution of Weak Spurious Modes in Quartz Plates
Authors: Watanabe Yasuaki , Sekimoto Hitoshi , Yoshimasa Oomura Yoshimasa Oomura
Published: October 2002

The method described here accurately determines the two-dimensional surface charge pattern of a weak mode existing in the vicinity of a strong mode in quartz crystal plate using an equivalent model that suitably approximates the surface charge frequency characteristics in the target modes measured at each measurement coordinate. The surface charge frequency characteristics are measured by an automated measurement system based on the electrical probe method. The temperature characteristics of the measured surface charge pattern of a weak mode near the fundamental thickness-shear mode in a rectangular AT-cut plate demonstrated that even for a weak mode, the present procedure provides patterns clearer than those obtained with a previous technique.
New Tilting Mechanism of Electron Gun for Reflection High-Energy Electron Diffraction
Authors: Toshihiro Ichikawa Toshihiro Ichikawa , Hisashi Oyama Hisashi Oyama
Published: October 2002

A new type of mechanism for tilting a reflection high-energy electron diffraction (RHEED) gun has been designed and constructed, which enables us to change the glancing angle of the primary electron beam when the specimen surface is located not only at a fixed position but also is moved to other positions. This is an advantage when other measurements are simultaneously undertaken with RHEED. RHEED measurements of a Si(110) surface were performed by placing the Si(110) surface at different positions, and the ability was verified.
Development of Mechanical Stress Simulator for Surface-Mount Devices
Authors: Keiji Yamamoto Keiji Yamamoto
Published: October 2002

A mechanical stress simulator for surface-mount devices was developed, which employed the finite-element method. The moisture distribution stage can calculate the moisture distribution of the LSI package exposed to temperature and humidity conditions. The heat conduction stage determines the time-dependent temperature distribution of the package immersed in a solder bath. Using the moisture and temperature distributions thus calculated, the mechanical stress stage gives the mechanical stress distribution in the package. Two groups of samples were prepared for solder dipping experiments. In one group, after dry baking for initialization, samples absorbed moisture by exposure at 30°C 85% (absorption process). In the other group, samples were exposed at 85°C 85% for 168 h and then dry-baked at 70°C (desorption process). These two groups have different moisture distributions in their packages. The results of solder dipping experiments are analyzed from the calculated mechanical stress values. In the absorption process, calculated maximum von Mises equivalent stress over the sectional molding compound σ; max increases monotonically with absorption time. Then, σ; max approaches its saturated value as absorption time tends to infinity. In the desorption process, σ; max decreases with desorption time and approaches the thermal stress value when desorption time tends to infinity. These calculations explain the effect of moisture distribution on package cracking.
Generalization of Ramo's Theorem and Its Application to Semiconducting Materials
Authors: Sato Kazunori , Takahashi Miki , Takano Hiroaki , Hashimoto Hajime , Niikura Yuichiro , Matsumoto Teru , Rutchanaphit Phophon
Published: October 2002

Ramo's theorem is generalized for the current statically induced in neighboring conductors by a specified movement of a charge carrier to include the higher frequency domain. As an example of application of the generalized theory, the current associated with carriers generated in a rectangular semiconducting material is computed. When taking the velocity difference between electrons and holes into account, the current normalized at low frequencies due to spatially uniform generation of carrier pairs in an intrinsic semiconductor is formulated as follows: I(ω)=∑
n=1,k
(n/ωτ)2[(1+ jωτ/n)exp
(- jωτ/n)-1], where k(>1) is the ratio of the electron velocity to the hole velocity, ω is the angular frequency, and τ is the transit time for a hole traversing through the device.
Debris Formation from Layered Plate Target by Microprojectile Impact
Authors: Tamura Hideki , Ueda Keiji , Akira B. Sawaoka Akira B. Sawaoka
Published: October 2002

For the feasibility study of the availability of a different-material-laminated spacecraft bumper, double-layered plate targets with the combination of an aluminum sheet and a copper one were prepared and impacted by glass microprojectiles at the velocity of 4 km/s. The morphology of target perforation and debris dispersion were investigated with respect to their dependence on material discontinuity in the target. Obvious difference was observed experimentally in the perforation and debris dispersion at the discontinuity. The difference was discussed qualitatively according to one-dimensional analysis of shock compression and pressure release in the target.
Kinetic-Energy-Enhanced Neutral Etching
Authors: Leone Stephen R.
Published: October 2002

A review is presented of the emerging field of neutral-species kinetic-energy-enhanced etching of silicon. As the gate oxide thickness of metal oxide semiconductor field-effect transistors (MOSFET) is decreased to dimensions of 50 Å or less, the potentially damaging effects of high-kinetic-energy ions in plasma processing become important. New methods are required to remove material in a more refined, selective manner. In this review, the motivations for studies of neutral-species enhanced-kinetic-energy etching are described. Currently available sources of neutral reactive species with enhanced kinetic energies of 1-10 eV are discussed, and published experimental and theoretical investigations of enhanced-kinetic-energy neutral etching are reviewed. Problems associated with neutral species etching are also considered, and some possible future developments in the field are summarized.
Gate Electrode Etching Using a Transformer Coupled Plasma
Authors: Yoshida Kazuyoshi , Miyamoto Hidenobu , Ikawa Eiji , Yukinobu Murao Yukinobu Murao
Published: October 2002

Gate electrode etching using a transformer coupled plasma (TCP) was studied for future device fabrication. The influence of chamber hardware configuration on plasma characteristics and etching performance has been studied for polysilicon and polycide etching. It has been found that etching and plasma uniformities greatly depend upon dielectric plate shape and position of the inductive coil on the dielectric plate, and that distance between the inductive coil and the dielectric plate has a big impact on the etching performance. This impact on the etching performance is caused by changing the capacitively coupled component in the inductively coupled plasma.
Profile Control of poly-Si Etching in Electron Cyclotron Resonance Plasma
Authors: Fujiwara Nobuo , Maruyama Takahiro , Masahiro Yoneda Masahiro Yoneda
Published: October 2002

Recent studies of plasma etching indicate that high-density charge irradiation easily induces radiation damage and local side etch. The local side etch has a characteristic dependence on the pattern layout and plasma conditions. The local side etch observed in poly-Si patterns with various widths of outside space increases with higher electron temperature perpendicular to the surface normal (T
ev) and higher ion current density. The rf bias method is effective for reducing local side etch. However, elimination of side etch with rf bias is due to an increased in ion energy. Thus high selectivity and no local side etch cannot be achieved at the same time. The local side etch with rf bias depends on electron temperature. Lower T
ev is effective for reducing the side etch even in the biased process.
Analysis of Plasma Chemical Reactions in Dry Etching of Silicon Dioxide
Authors: Kazumi Hideyuki , Tago Kazutami
Published: October 2002

A computational model for chemical reactions in plasmas has been developed and applied to the gas-phase chemistry of dry etching of silicon dioxide. An ab-initio molecular orbital method is used to determine the dissociation processes and the threshold energies for gases and neutral radicals. Plasma chemistry is calculated by the plasma chemical kinetic method. The chemical compositions of the dry etching plasmas were investigated for fluorocarbon gases. Calculated ion fluxes, electron temperatures, and densities agreed with experimental results within factors of three. The differences in plasma characteristics between CHF3/CH2F2 and C4F8 were attributed to differences in the products and threshold energies of the dissociation reactions. Correlations could be found between the composition of radicals in a plasma and the etch selectivity in C4F8.
Analysis of Polymer Formation during SiO2 Microwave Plasma Etching
Authors: Gotoh Yasushi , Tokuo Kure Tokuo Kure
Published: October 2002

The mechanism of C
x
F
y
fluorocarbon deposition during SiO2 etching is analyzed using a test sample with an overhang mask. For C4F8, CHF3, and CH2F2, only C
x
F
y
deposition was observed at 0 W of substrate-bias rf power, and the deposition profiles were similar. At a higher rf power, reaction phenomena changed to those of SiO2 etching. The standard deviation σ of the etching-ion incident angle was measured as less than 2°. On the other hand, σ
d
e
p
o
measured from the deposition profile was about 20°. This difference may be caused by surface migration. This migration is thought to be a key factor in excess deposition at the bottom of a high-aspect-ratio hole. Etching rates of the deposit increased in the order of C4F8>CHF3>CH2F2. Therefore, SiO2-etching gases, such as C4F8, which form easily removable deposits, reduce RIE lags for contact hole patterning.
Mechanism of Reactive Ion Etching Lag for Aluminum Alloy Etching
Authors: Sato Tetsuo , Fujiwara Nobuo , Masahiro Yoneda Masahiro Yoneda
Published: October 2002

It is well known that aluminum anisotropic etching with a photoresist mask is accomplished using a sidewall passivation film which is composed of fragments of photoresist sputtered by ion bombardment. As a result, the selectivity of aluminum to photoresist is reduced under such conditions. Under these conditions, it is thought that the effect of reactive ion etching (RIE) lag becomes a serious problem. We study the dependence of the aluminum etch rate and RIE lag with photoresist and SiO2 masks on etching parameters. The RIE lag strongly depends on rf bias and the materials of the etching mask. This phenomenon corresponds to the deposition of fragments of mask material sputtered by ion bombardment on the aluminum surface. Moreover, the deposition rate strongly depends on the distance from the pattern edge of the mask. This is that the etch rate in a narrow space pattern is lower than that in an open space pattern.
Laser-Diode-Based Mode-Shape Measurement System for Very-High-Frequency Quartz Resonators
Authors: Watanabe Yasuaki , Sekimoto Hitoshi , Yoshimasa Oomura Yoshimasa Oomura
Published: October 2002

A laser-diode-based system for measuring the patterns of in-plane vibrational displacement in quartz resonators is described. This system utilizes the force-frequency effect in detecting the displacement. Its employment of a semiconductor laser-diode module makes the measurement fixture very simple and compact. The experimental results for a very-high-frequency AT-cut quartz resonator demonstrate the validity of this system.
Charge State Dependences of Positron Trapping Rates Associated with Divacancies and Vacancy-Phosphorus Pairs in Si
Authors: Kawasuso Atsuo , Hasegawa Masayuki , Suezawa Masashi , Yamaguchi Sadae , Koji Sumino Koji Sumino
Published: October 2002

Charge state dependences of positron trapping rates associated with divacancies and vacancy-phosphorus pairs in Si have been studied by controlling the Fermi level systematically. The specific trapping rates of both a divacancy and a vacancy-phosphorus pair increase with an increase in the negative charge on them. A positively charged divacancy shows no detectable positron trapping. Such charge state dependences of the positron trapping rates clearly show that the long-range Coulomb interactions between a positron and a charged divacancy or a charged vacancy-phosphorus pair play an important role in the trapping process.
Electrical Studies of Rapidly Annealed Ni and Pd/n-GaAs Schottky Diodes
Authors: Ghader Eftekhari Ghader Eftekhari
Published: October 2002

The effects of rapid thermal annealing 1-100 s on the electrical characteristics of Ni and Pd contacts on n-GaAs are studied. At annealing temperature (Ta) of 300° C and 450° C the contacts remained quite stable. At annealing temperature of 600° C the contacts showed sign of degradation if they are annealed for more than 40 s. Degradation in Pd contacts was more pronounced than in Ni contacts. Consumption of GaAs and formation of different reactions at the interface, resulting in a layer containing defects and inhomogeneity are used to explain the observations.
Theoretical Study for Drastic Improvement of Solar Cell Efficiency
Authors: Hideki Matsumura Hideki Matsumura , Hiroto Kasai Hiroto Kasai
Published: October 2002

A new technique to improve the energy conversion efficiency of thin-film solar cells such as amorphous silicon cells is theoretically studied. In the technique, thin trap layers are introduced in a depletion region of p-n or p-i-n structure. The traps act as stepping stones in two-step excitation of electrons from valence to conduction bands, and thus, sunlight with photon energy less than the energy of the band gap can be utilized to improve cell efficiency. It is found that if the energy level of traps is located far from the center of the band gap, the probability of two-step excitation through traps becomes dominant over that of carrier recombination. This new technique is effective to improve solar cell efficiency drastically, for instance, the efficiency of amorphous silicon solar cells is expected to be about twice by this technique in some special cases.
Si/1ML-Ge/Si(001) Interface Structure Characterized by Surface X-Ray Diffraction and X-Ray Standing-Wave Method
Authors: Takahasi Masamitu , Nakatani Shinichiro , Takahashi Toshio , Zhang Xiaowei , Ando Masami , Fukatsu Susumu , Shiraki Yasuhiro
Published: October 2002

The structure of a δ-doped crystal, Si(800Å)/Ge(1ML)/Si(001), grown by molecular beam epitaxy has been studied by surface X-ray diffraction and X-ray standing-wave method. The positions of the Ge layer and the Si capping layer are determined with respect to the Si substrate. In the analysis, the roughnesses of the interface and the surface are considered. The distance between the bottommost capping layer and the topmost substrate layer is 2.068±0.002 in units of the interlayer spacing of Si(004), while the distance between the Ge layer and the topmost Si substrate layer is 1.058±0.001. The former value corresponds to an averaged structure where the macroscopic elastic theory is applicable to the evaluation of the strain and the latter value corresponds to a microscopic structure where the bulk bond length is conserved. Coexistence of the two kinds of structures is made possible by the interfacial roughness.
Characterization of Abrasively Processed Surface of Si(100) Wafer
Authors: Ogasawara Toshihide , Tsuchida Masahiko , Yagi Hideichi , Kuroda Tsukasa , Mori Hirotaroh , Iwakuro Hiroaki , Tamaki Shozo
Published: October 2002

Si(100) wafer was abrasively processed (ground or lapped), and the crystallographic and electroconductive properties of the surface were investigated. Large surface crystallites formed by grinding gave a large contact resistance between the surface and the deposited Ti film. Surfaces which had been made polycrystalline by grinding or lapping showed small resistances. The processing can be used for a high-yield production of thin power metal-oxide semiconductor field effect transistors.
Averaging Effect on Current-Voltage Characteristics of ZnO Varistors
Authors: Wang Hsin , Schulze Walter A. , Cordaro James F.
Published: October 2002

Surface electrode patterns with systematic changes of electrode gap distances and widths have been developed to investigate the averaging effect in the current-voltage ( I-V ) measurements of ZnO varistors. Varistor breakdown voltages, V
B, and the nonlinear exponent, α, were obtained from the I-V measurements. The α vs voltage plots showed multiple breakdown peaks when the gap distances were greater than 2.5× the average grain diameter. A decrease in α due to the lower-voltage breakdowns was also observed. The same effect was obtained when single-junction I-V results were used in simulating the junction network on a computer. The broad distribution of grain size is considered as the main cause of multiple breakdowns. The small amount non-switching and short-circuited junctions also play an important role in the device I-V characteristics.
Effect of Preoxide on the Structure of Thermal Oxide
Authors: Nohira Hiroshi , Saito Kenji , Sakusabe Kenichi , Makihara Koji , Morita Mizuho , Ohmi Tadahiro , Takeo Hattori Takeo Hattori
Published: October 2002

It is found from X-ray photoelectron spectroscopy study on the chemical structure of silicon dioxide, whose thickness is in the range of 1.2 nm to 8.6 nm, that the oxidation-induced chemical shift depends mainly on the distance, and that 0.4- and 0.6-nm-thick preoxide, which is formed in dry oxygen at 300° C, modifies the structure of oxide near the surface.
Relationship between Transition Temperature and x in V1-xWxO2 Films Deposited by Dual-Target Magnetron Sputtering
Authors: Jin Ping , Sakae Tanemura Sakae Tanemura
Published: October 2002

Thin films of V1-
x

W

x

O2 were deposited on glass and Si by dual-target sputtering and characterized by thin film X-ray diffraction (XRD), Rutherford backscattering spectrometry (RBS) and spectrophotometry. The relationship between x (0-0.026) and the phase transition temperature τ c (0-67° C) in the most applicable range for advanced window coatings was clarified by formation of a single-phase film and precise determination of the amount of doping. Tungsten doping linearly decreases τ c by 23° C/at.%W and also significantly reduces the thermal hysteresis loop width in optical transmittance.
Numerical Analysis of Electrical Breakdown Induced by Laser Irradiation in N2/O2Gas Mixture
Authors: Takahashi Akihiko , Kiyoto Nishijima Kiyoto Nishijima
Published: October 2002

This paper presents a theoretical investigation on the electrical breakdown process of air induced by intense pulsed laser beams. We develop a computer simulation model including both the Boltzmann equation and the rate equations. The calculations are performed for different laser wavelengths of 308 nm (XeCl), 694 nm (ruby), 1.06 µ m (YAG) and 10.6 µ m ( CO2). The result on the laser wavelengths is qualitatively consistent with the experimental result. The laser-induced breakdown process is discussed in detail.
Ferroelectric Materials for Electromechanical Transducer Applications
Authors: Leslie Eric Cross Leslie Eric Cross
Published: October 2002

Many advantages of ferroelectric compositions in the lead zirconate:lead titanate (PZT) solid solutions for both sensing and actuation are explored. The state of understanding of both intrinsic single domain and extrinsic domain wall and phase boundary contribution to response is described, and the composition manipulations used to modifiy the extrinsic responses explored. In lead magnesium niobate (PMN) based solid solution a nanometer scale ordering of Mg:Nb cations breaks up the conventional ferroelectric coupling leading to glass like relaxor ferroelectric response. The fact that problems arising from density and rigidity of PZT for large area transducers are markedly worked out in piezoceramic:polymer composites is also briefly explored.
Simulation of Chaotic Behavior in Piezoelectric Resonators
Authors: Yutaka Abe Yutaka Abe
Published: October 2002

Nonlinear resonant structures in a thickness-shear-mode quartz resonator under intense excitation are investigated by numerical simulation. It is indicated that a dynamical symmetry breaking precursor generates driving forces in addition to primary driving force, which leads to period-doubling bifurcation. We also demonstrate suppression of the chaotic instabilities by means of a small periodic perturbation to the primary driving force.
An Ultrasonic Monitoring of the Sol-Gel Process in Silicon Alkoxide Solutions
Authors: Matsukawa Mami , Nagai Isao , Yuko Tanaka Yuko Tanaka
Published: October 2002

The sol-gel process in silicon alkoxide solutions (TEOS(silicon tetraethoxide)- HCl-H2O-C2H5OH) has been investigated using an ultrasonic longitudinal pulse technique. The process under isothermal conditions was monitored non-destructively and continuously by changes in ultrasonic wave velocity. The velocity changes in the solution was clearly found to depend on the experimental system. In case of open system measurements, the velocity at first increased and slightly decreased after gelation. However in the closed system, the velocity gradually decreased. The velocity difference between the open and closed system would seem to result from the evaporation of solvent, as suggested by changes in the temperature and weight of the solutions used.
Thermal Diffusivity Measurement of Liquid Samples by Inverse Photopyroelectric Detection
Authors: Morioka Naoki , Yarai Atsushi , Takuji Nakanishi Takuji Nakanishi
Published: October 2002

This paper describes a new method for measuring the thermal diffusivity of liquid samples through inverse photopyroelectric detection measurement. It is proven that thermal diffusivity values can be obtained with both amplitude signals and phase signals in a low frequency range. At around 3 Hz, these values are found to correspond to their theoretical values. We experimentally prove that the piezoelectric effect, which films are known to exhibit, is negligibly small compared with the photopyroelectric effect.
A Method of Adjusting Frequency Temperature Coefficients and Resonant Frequency for NS-GT Cut Quartz Crystal Resonators
Authors: Hirofumi Kawashima Hirofumi Kawashima
Published: October 2002

This paper describes a method of adjusting the frequency-temperature coefficients and resonant frequency of NS-GT cut quartz crystal resonators. It is well known that NS-GT cut resonators show good frequency-temperature behavior because the first-, second- and third-order temperature coefficients α+, β+, γ+ for principal vibration can be approximately zero. However, a distribution of frequency-temperature behavior takes place in production. In order to obtain resonators with better and stable frequency-temperature behavior within +/-2.5 ppm over a temperature range of -30 to +85° C in production, an absolute value of α+ must be less than 5×10-8/° C. The adjustment method described makes it possible to control α+ easily. The NS-GT cut resonators' frequency-temperature characteristics were found to be mostly within +/-1.0 ppm in the above-mentioned temperature range.
Finite-Element Analysis of Trident-Type Tuning Fork Resonator for Vibratory Gyroscope
Authors: Akira Satoh Akira Satoh , Kazumasa Ohnishi Kazumasa Ohnishi , Katsutoshi Sakurai Katsutoshi Sakurai , Yoshiro Tomikawa Yoshiro Tomikawa
Published: October 2002

We have investigated the possibility of producing a highly stable piezoelectric vibratory gyroscope. In order to achieve such a gyroscope, a trident-type tuning fork resonator was adopted, because it has good inherent vibrational characteristics for its support conditions. However from a practical viewpoint, the tuning fork must be studied with the aim of achieving very high stability, and high performance as an angular rate sensor. Therefore, we investigated the detailed vibrational displacement characteristics using finite-element methods and showed that unnecessary vibration of the tuning fork influenced the sensitivity of the gyroscope. That is, this paper concerns the dimensional conditions of the tuning fork for decreasing vibrational displacements at its base portion. We also report the measured characteristic of the angular rate sensor using such an improved tuning fork.
Surface Acoustic Wave Propagation Characterisation by Finite-Element Method and Spectral Domain Analysis
Authors: Endoh Gou , Ken-ya Hashimoto Ken-ya Hashimoto , Masatsune Yamaguchi Masatsune Yamaguchi
Published: October 2002

This paper proposes a method of deriving the discrete Green function for the analysis of surface acoustic wave (SAW) propagation and excitation under metallic-grating structures with finite thickness. The method uses the finite-element method (FEM) for the analysis of the grating electrode region, while the spectral domain analysis (SDA) is used for the analysis of the substrate region. This approach takes account of the mass-loading effect of grating electrodes as part of electrical quantities in a substrate, and makes it possible to employ Blφtekjær et al.'s theory for rapid computation. Rayleigh SAWs and leaky SAWs propagating under metallic-grating structures on 128°Y
X- LiNbO3 and 36°Y
X- LiTaO3 (36-LT), respectively, were analysed. The dispersion relation calculated by the present method agreed very well with that obtained by the perturbation theory. It is also shown that the electromechanical coupling factor for leaky SAWs on 36-LT increases with the thickness of grating electrodes, which is primarily due to the change in the SAW energy concentration near the surface.
Fabrication of Diffraction Grating Assisted by Surface Acoustic Wave
Authors: Yasuhiko Nakagawa Yasuhiko Nakagawa , Mitsuhiro Gunzi Mitsuhiro Gunzi , Shouzi Kakio Shouzi Kakio
Published: October 2002

It was found for the first time that a diffraction grating was formed by perturbation in film thickness and refractive index with period of half the wavelength of surface acoustic waves, when thin film was deposited on substrate in which standing surface wave was excited. No such phenomenon has been reported so far, and its application to optical elements is hoped to be a new applications of surface acoustic waves.
Experimental Studies on Nonlinear Dispersive Surface Acoustic Waves for Solitons
Authors: Kavalerov Vadim , Katoh Hideki , Kasaya Naohito , Inoue Mitsuteru , Toshitaka Fujii Toshitaka Fujii
Published: October 2002

Nonlinear dispersive surface acoustic waves propagating on LiNbO3 single-crystal plates were studied. In order to control the dispersion, a thin SiO2 overlay was applied. Harmonic generation measurements in the crystals without SiO2 overlay show that the second-harmonic amplitude exceeds that of the fundamental wave when the initial wave amplitude exceeds 40 Å, and the spatial periodicity length of harmonic generation varies depending on power. In the samples with 500-Å-thick SiO2 coatings, no significant change of the periodicity length with power has been detected. In both cases we observed an increase of phase velocity with acoustic power. Comparison of the experimental data with the spectrum of Korteweg-de Vries solitons suggests the presence of surface acoustic wave solitons.
A Study on Measuring Techniques of Phase Velocities of Surface Acoustic Waves
Authors: Kouji Taki Kouji Taki , Atsuhiro Nishikata Atsuhiro Nishikata , Yasutaka Shimizu Yasutaka Shimizu
Published: October 2002

The phase velocities of surface acoustic waves (SAWs) determined by simply measuring the phase characteristics of SAW devices are not accurate. One of the error facters is the nonlinearity of the phase characteristics of SAW devices due to the interdigital transducers (IDTs). The phase velocities have been determined from direct or indirect phase measurements of IDTs. Correction is made for those velocities by using Smith's equivalent circuit of the IDT in order to eliminate the errors. This method is as accurate as Hirabayashi's method, which is designed to cancel the nonlinear effect of IDTs. Moreover, it is simpler than the conventional method since it does not require special IDTs or additional circuits.
Characteristics of Surface Acoustic Wave on AlN Thin Films
Authors: Kobayashi Yasumi , Tanaka Naoki , Okano Hiroshi , Takeuchi Kousuke , Usuki Tatsuro , Kenichi Shibata Kenichi Shibata
Published: October 2002

A surface acoustic wave (SAW) on a (00·1) plane of hexagonal aluminum nitride (AlN) deposited on R-plane sapphire ( (1\bar1·2)Al2O3) with an inclination of about 26 degrees to the substrate was analyzed. A Rayleigh wave and shear-horizontal-type (SH-type) wave were found. The phase velocity of these was 5400-5800 m/s and 6100-6600 m/s, respectively. To confirm this results, the propagating characteristics of both SAW modes were measured by input admittance of single interdigital transducers (IDT) and by transmission characteristics between two IDTs. The phase velocity of the Rayleigh wave and the SH-type wave was 5600 m/s and 6500 m/s, respectively, and the propagation loss was 0 dB/λ and 0.04 dB/λ, respectively. These measured characteristics approximately agree with the results of the simulation.
Concentration and Fractionation of Small Particles in Liquid by Ultrasound
Authors: Yasuda Kenji , Umemura Shin-ichiro , Takeda Kazuo
Published: October 2002

The efficacy of the ultrasonic standing plane wave in concentrating small particles was theoretically evaluated and compared with experimental results. Acoustic energy density was estimated by measuring the ultrasonic absorption, and particle distribution was observed by dark-field microscopy. The theory predicts that diffusion is negligible in concentrating polystyrene spheres larger than 5 µ m in diameter when they are subjected to 2 J/m3 ultrasound. The half-width of the steady-state particle distribution was of the same order of magnitude as the theoretical value for the particles of 1 µ m and 2 µ m diameter. We also applied this concentrating technique to fractionation of polystyrene spheres 10 µ m in diameter, and more than 90% of the particles in the laminar flow were successfully collected.
Simplified Equivalent Circuit of Ultrasonic Motor and Its Application to Estimation of Motor Characteristics
Authors: Manabu Aoyagi Manabu Aoyagi , Yoshiro Tomikawa Yoshiro Tomikawa
Published: October 2002

This present paper deals with a simplified equivalent circuit of an ultrasonic motor and its application to the estimation of motor characteristics. Investigation of this equivalent circuit is conducted from the viewpoint of systematization of research on ultrasonic motors. The equivalent circuit must show the principle of motor operation and must be expressed simply. In this paper, we propose simplified equivalent circuits of two types of ultrasonic motors which have different combinations of vibrations used. As a result, it has been proven that these equivalent circuits are similar to each other in spite of the difference in the vibrations used. In this paper, moreover, measurement points of an ultrasonic motor for estimation of its characteristics are clarified.
Translation of an Object Using Phase-Controlled Sound Sources in Acoustic Levitation
Authors: Matsui Takayasu , Ohdaira Etsuzo , Masuzawa Nobuyoshi , Masao Ide Masao Ide
Published: October 2002

Acoustic levitation is used for positioning materials in the development of new materials in space where there is no gravity. This technique is applicable to materials for which electromagnetic force cannot be used. If the levitation point of the materials can be controlled freely in this application, possibilities of new applications will be extended. In this paper we report on an experimental study on controlling the levitation point of the object in an acoustic levitation system. The system fabricated and tested in this study has two sound sources with vibrating plates facing each other. Translation of the object can be achieved by controlling the phase of the energizing electrical signal for one of the sound sources. It was found that the levitation point can be moved smoothly in proportion to the phase difference between the vibrating plates.
Measurement Method of Ultrasonic Velocity in Liquid and Solid Using Continuous Wave Signal
Authors: Imano Kazuhiko , Hiroshi Inoue Hiroshi Inoue
Published: October 2002

The measurement principle of ultrasonic velocity in liquids and solid with the continuous wave signal is suggested using a transmission line model of the ultrasonic system. The measurement system, including network analyzer, ultrasonic transducer, backing, sample and reflector, is successfully configured to evaluate the ultrasonic velocity by the S-parameter. Experiments with liquid and solid samples show agreement between our method and the correlation method within 4 m/s. The features of our method are also discussed.
Ultrasonic Velocity Measurement Using Optical Beam Deflection
Authors: Tatsuro Matsuoka Tatsuro Matsuoka , Akihiro Kumata Akihiro Kumata , Shinobu Koda Shinobu Koda , Hiroyasu Nomura Hiroyasu Nomura
Published: October 2002

A newly designed apparatus for measurement of ultrasonic velocity in liquids based on the optical beam deflection technique is constructed. This method relies on the phase-sensitive detection of the optical deflection angle. The apparatus is suitable for measurements in the frequnecy range from 5 MHz to 75 MHz. In this study, application of this apparatus to water and diisobutylphthalate is described.