bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of Coulomb Interaction in Tunneling Current through Several Energy Levels
Authors: Makoshi Takashi Mii , Shima Nobuyuki
Published: October 2002

Based on the nonequilibrium Anderson model, we discuss the nonlinear property of the current between two electrodes through an atom which has several orbitals with a finite bias voltage. This model is used to study the Coulomb blockade phenomenon from the small system size limit. The Mahanthappa-Baksi-Keldysh Green function formalism is employed to deal with the nonequilibrium system. We give the expression for the current and the number of electrons for each state. Employing the Hartree-Fock approximation, we calculate the tunneling current numerically. To determine the solution uniquely, we extend the free energy for the nonequilibrium case. We can show that the stationary condition of this extended free energy in the Hartree-Fock approximation is equivalent to the Hartree-Fock equation.
Existence of a Critical Size in Fully Symmetrical Semiconductor Quantum Dots
Authors: Shang Yuan Ren Shang Yuan Ren
Published: October 2002

Due to the valence band maximum degeneracy of cubic semiconductors, a critical size might exist in their fully symmetrical quantum dots. When the size of the quantum dots decreases past this critical size, the originally direct semiconductor becomes indirect and the originally indirect semiconductor becomes less indirect.
The Role of Electron Phase Coherence in Quantum Transport through Open Ballistic Cavities
Authors: Bird Jonathan P. , Micolich Adam P. , Akis Richard , Ferry David K. , Newbury Richard , Taylor Richard P. , Olatona Dapsy M. , Wirtz Rene , Ochiai Yuichi , Ishibashi Koji , Yoshinobu Aoyagi Yoshinobu Aoyagi , Takuo Sugano Takuo Sugano
Published: October 2002

We consider the factors which limit electron wave coherence in open quantum dots, through a study of the reproducible fluctuations in their low temperature magneto-resistance. Our investigations indicate that at temperatures well below a degree Kelvin, electrons are able to propagate ballistically while maintaining phase coherence over very long time scales. Indeed, simple calculation reveals that electrons may undergo as many as a hundred collisions with the confining walls before coherence of their wavefunction is fully randomized.
A Scanning Tunneling Microscopy-Reflection High Energy Electron Diffraction-Rate Equation Study of the Molecular Beam Epitaxial Growth of InAs on GaAs(001), (110) and (111)A–Quantum Dots and Two-Dimensional Modes
Authors: Joyce B. A. , Sudijono J. L. , Belk J. G. , Yamaguchi H. , Zhang X. M. , Dobbs H. T. , Zangwill A. , Vvedensky D. D. , Jones T. S.
Published: October 2002

The growth modes of InAs on the three low index orientations of GaAs during molecular beam epitaxy (MBE) are very different, despite a constant lattice mismatch of ≈7%. Coherent three-dimensional (3D) growth occurs only on (001) surfaces; on the other two orientations strain relaxation involves misfit dislocation formation and a continuous two dimensional growth mode. Strain is therefore not a sufficient condition to induce 3D growth. Reflection high-energy electron-diffraction and scanning tunnelling microscopy observations confirm that an intermediate `wetting layer' is formed on (001)-oriented substrates prior to the formation of quantum dots. The thickness and composition of this layer is dependent on both growth temperature and the amount of InAs deposited, but it is always an (In, Ga)As alloy. We have also confirmed that substantial mass transport occurs during quantum dot formation and that the dots themselves have an alloy composition. A model to account for at least some of these effects, based on rate equations, is introduced.
Room Temperature Coulomb Blockade and Low Temperature Hopping Transport in a Multiple-Dot-Channel Metal-Oxide-Semiconductor Field-Effect-Transistor
Authors: Toshiro Hiramoto Toshiro Hiramoto , Hiroki Ishikuro Hiroki Ishikuro , Tomoyuki Fujii Tomoyuki Fujii , Gen Hashiguchi Gen Hashiguchi , Toshiaki Ikoma Toshiaki Ikoma
Published: October 2002

We have investigated the transport properties of an extremely narrow channel metal-oxide-semiconductor field-effect-transistor (MOSFET) fabricated by a novel anisotropic etching technique. The device shows clear Coulomb blockade oscillations at room temperature, while aperiodic sharp peaks are observed at low temperatures. Measurements of temperature dependence and magnetic field dependence reveal that the narrow channel of the MOSFET is separated into quantum dots and that not only the resonant tunneling transport but also the thermally activated hopping conduction plays an important role at low temperatures.
Vertically Coupled Quantum Dot Lasers: First Device Oriented Structures with High Internal Quantum Efficiency
Authors: Zaitsev Sergey V. , Gordeev Nikita Yu. , Kopchatov Vladimir I. , Ustinov Victor M. , Zhukov Alexy E. , Egorov Anton Yu. , Ledentsov Nikolay N. , Maximov Mikhail V. , Kop'ev Peter S. , Kosogov Alexander O. , Alferov Zhores I.
Published: October 2002

Main mechanisms of internal carrier losses and leakage from the ground state of quantum dots have been studied in heterostructure lasers based on vertically coupled quantum dots. It has been shown that the threshold current density may be reduced down to 15 A/cm2 at room temperature by reducing the non-radiative recombination and improving the carrier localization.
Novel Azo Dye-Doped Poly(Methyl Methacrylate) Films as Optical Data Storage Media
Authors: Vinh Phuc Pham Vinh Phuc Pham , Tigran Galstyan Tigran Galstyan , André Granger André Granger , Roger A. Lessard Roger A. Lessard
Published: October 2002

Azo dye-doped polymer (ADP) systems have been shown to be remarkable photosensitive media for holographic recording and optical computing. In this work we have studied the dynamic holographic capabilities of poly(methyl methacrylate) (PMMA) fims doped with five new azo dyes named AZD1-5. The totally reversible trans \rightleftharpoons cis photoisomerization induced by exposure of the ADP samples to actinic light allows recording of holograms in the dye-doped polymer matrices, and diffraction efficiencies up to 10% have been attained. These ADP systems can also be used to perform polarization holographic recordings as they present a photoinduced anisotropy called the Weigert effect. Depending on the intensity of the reading beam, the recorded information can be rapidly erased or stored for a posteriori use. The storage time can be as long as 800 s depending on the azo dye employed. These photosensitive materials can be classified as promising holographic media for optical computing and optical mass storage.
Hydride Vapor Phase Epitaxy of InxGa1-xN Thin Films
Authors: Yuichi Sato Yuichi Sato , Susumu Sato Susumu Sato
Published: October 2002

In this paper, we investigate the growth of In

x

Ga1-
x

N thin films using the hydride vapor phase epitaxy (HVPE) method. Indium is hardly contained in films grown at higher growth temperatures, and phase separation tendencies between InN and GaN are observed in some grown films. In their photoluminescence spectra measured at room temperature, two peaks are observed at 370 nm and 430–440 nm.
Valence Dependence of Electron Energy Loss Spectra of Chromium Oxides
Authors: Satoru Suzuki Satoru Suzuki , Masato Tomita Masato Tomita
Published: October 2002

The core level electron energy loss spectra of nominally tetravalent CrO2and trivalent Cr2O3were measured. The Cr-Lmultiplet structure of CrO2did not show a distinctly different spectrum from that of trivalent Cr2O3, although transition metalLspectra generally vary strongly with the oxidation states. The difference of the oxidation states was clearly observed in the O-Kspectra in contrast to the Cr-Lspectra. The O-Kenergy loss near edge structures revealed that the lowest conduction band of CrO2has a large oxygen 2pcomponent. It is concluded that the weak valence dependence of the Cr-Lspectra is due to the relatively larged3L component in the electron configuration of CrO2.
Electronic Defect Levels in Ultra-Shallow p+n-Junctions Formed by Low-Energy B Ion Implantation into Ge-Preamorphized Silicon
Authors: Benzohra Mohammed , Olivie François , Boussaid Farid , Daniel Alquier Daniel Alquier , Augustin Martinez Augustin Martinez
Published: October 2002

Ultra-shallow p+n-junctions were formed by low-energy boron implantation into n-type monocrystalline silicon preamorphized with germanium. The boron implantation was performed at 3 keV and 1015 cm-2. The crystallization and the electrical activity were obtained by rapid thermal annealing (RTA) at a control thermocouple setting of 950° C for 15 s. In this work, the electrical defects induced by this process were characterized by isothermal transient capacitance (ΔC(t, T)) measurements and deep level transient spectroscopy (DLTS). The electron emission spectrum is dominated by two kinds of defects. The first is classical and is represented by two discrete levels related to germanium implantation. The second, observed for the first time in such structures, seems to be an energy distributed continuum located between 0.18 eV and 0.33 eV below the conduction band edge. It is most probably related to both boron implantation and RTA. Its concentration profile depth of 4 mm within the silicon substrate may be associated with defect complexes originating either from interstitials or vacancies. The profiles were used to distinguish between the two types of defect and to evaluate accurately their signature.
Effects of Post-Annealing on the Conduction Properties of Pt/(Ba, Sr)TiO3/Pt Capacitors for Dynamic Random Access Memory Applications
Authors: Joo Jae-Hyun , Jeon Yoo-Chan , Seon Jeong-Min , Oh Ki-Young , Jae-Sung Roh Jae-Sung Roh , Jae-Jeong Kim Jae-Jeong Kim
Published: October 2002

Pt/(Ba, Sr)TiO3/Pt capacitors were fabricated on TiN/Ti/ Poly–Si/SiO2/Si substrate by sputtering technique and effects of post-annealing conditions on the current vs. voltage ( I–V ) characteristics of the capacitors were investigated. It was found that leakage currents of Pt/BST/Pt capacitors were greatly depended on the annealing sequence as well as annealing atmosphere. BST films annealed under Ar/H2 or N2 showed much higher leakage current than as-deposited films regardless of the fabrication of top electrode. On the contrary, annealing under O2 atmosphere was effective to reduce leakage currents of the BST films if annealing process was carried out after fabrication of top electrode. Leakage current of Pt/BST(50 nm)/Pt capacitors annealed under O2 atmosphere at 500° C for 1 h after fabrication of Pt top electrode was 5×10-7 A/cm2 even at 7 V. In this work, effects of annealing conditions on the I–V properties of Pt/BST/Pt capacitors were explained with energy band diagram in which oxygen vacancies play a key role.
A Method for Determining Elastic Constants of Nematic Liquid Crystals at High Electric Fields
Authors: Ying Zhou Ying Zhou , Susumu Sato Susumu Sato
Published: October 2002

The elastic constants of liquid crystals are very important parameters for physical studies of liquid crystals and for liquid crystal displays. In this paper, a new method of determine the elastic constant ratio K
11/K
33 and the elastic constant K
11 of nematic liquid crystals by measurement of their optical retardation and capacitance at high electric fields is proposed. We derive theoretical formulas for the elastic constants, and then set up an optical retardation and capacitance measurement system. Finally, the experimental results for two commonly used liquid crystal compounds are discussed.
Comparative Role of Metal-Organic Decomposition-Derived [100] and [111] in Electrical Properties of Pb(Zr, Ti)O3 Thin Films
Authors: Chen San-Yuan Chen
Published: October 2002

The effect of composition (phase), texture, microstructure and thickness on electrical properties of Pb(Zr1-
x

Ti

x

)O3 (PZT) films have been evaluated. Zr-rich PZT films with [111] texture have a higher remanent polarization and dielectric constant, but a lower coercive field as compared with PZT[100] films. Ti-rich PZT films with [100] texture have a higher dielectric constant, but a lower remanent polarizalion and coercive field as compared with PZT[111] films. Near the morphotropic phase boundary (MPB) composition, films with a mixed texture of [111] and [100] have a higher dielectric constant than PZT[100] and PZT[111] films even though the values of remanent polarization and coercive field of the mixed textured films are in between those of the other two films. Both remanent and saturation polarization are independent of film thickness, whereas dielectric constant decreases but coercive field increases at very small thickness.
Pattern Classification in a Perceptron Circuit Using Lead Phthalocyanine Films
Authors: Katsuhiro Nichogi Katsuhiro Nichogi , Akihito Miyamoto Akihito Miyamoto , Mutsuaki Murakami Mutsuaki Murakami
Published: October 2002

Evaporated films of lead phthalocyanine (PbPc) show a unique conductivity change after a very slight amount of gases are adsorbed. The change in the conductivity of the films depends on the polarity and the strength of input voltages, and therefore is analogous to the change of synaptic connections in nerve systems. Therefore, a perceptron circuit has been fabricated using PbPc films as synaptic connections. After learning via loading of input signals and teacher signals, this circuit can classify random inputs of eight-dimensional voltage patterns into two categories when the input patterns are linearly separable.
A Compact High-performance Helium Atom Scattering Apparatus for Surface Studies
Authors: Miyake Tatsuya , Edward S. Gillman Edward S. Gillman , Ichirou Oodake Ichirou Oodake , Hrvoje Petek Hrvoje Petek
Published: October 2002

We describe a very compact apparatus developed for high resolution studies of surface structure and phonon spectroscopy by means of diffraction and inelastic scattering of a supersonically cooled He atom beam. The angular and energy resolutions for the specularly reflected beam are 0.13° and ΔE = 0.4 meV, respectively, for an incident energy of E
i = 22 meV. The process of modification of the surface structure by thermal desorption of adsorbates, or irradiation by electron, radical, and ion beams, can be monitored non-destructively under UHV conditions by measurements of the scattered intensity of He atoms. The performance of the apparatus is assessed by measurement of He diffraction and inelastic scattering from the low index single crystal surfaces of copper. The potential of the apparatus for kinetic studies of surface reactions is demonstrated for reduction of a copper oxide surface by a H atom beam.
Characteristics of an ECR Plasma Sputtering Source at Low Ar/N2 Gas Pressures for Thin Film Synthesis
Authors: Shoyama Hiroaki , Mi\usina Martin , Shoji Miyake Shoji Miyake
Published: October 2002

The characterization of electron cyclotron resonance (ECR) plasma with a hollow cathode target for sputtering has been performed with a Langmuir probe. The experiments were carried out at low pressures below 1.2×10-3 Pa at which high ionization rates over 10% were obtained. An ion current density up to 10 mA cm-2 and a target current up to 700 mA were achieved when the input microwave power was 200 W. It was found that a negative bias applied to the target causes significant changes in the spatial distributions of electron density, electron temperature and plasma potential. When a negative bias over a certain value was applied, intense coherent temporal fluctuations in the ion saturation current were observed around the radial center of the plasma column.
Plasma Diagnostics in rf Discharges Using Nonlinear and Resonance Effects
Authors: Klick Michael , Wolfgang Rehak Wolfgang Rehak , Marita Kammeyer Marita Kammeyer
Published: October 2002

In modelling rf discharges, nonlinear phenomena usually are treated as inconvenient effects. A method based on a nonlinear phenomenon is the self excited electron plasma resonance spectroscopy (SEERS). This new method for plasma monitoring allows to determine density and collision rate of the electrons and the power dissipated in the plasma body. Microwave interferometry (MWI) and Langmuir probe (LP) measurements were used to verify this method. This is shown for inert (He, Ar) and electronegative gases ( O2, CF4). Examples of in situ control in plasma etching process are described. The high sensitivity and the capability of endpoint detection are shown.
Parameters Measurement of ECR Silane Plasma
Authors: Morimoto Michikazu , Ueda Yoko , Hiejima Shinya , Itsuo Katsumata Itsuo Katsumata , Yoshinobu Kawai Yoshinobu Kawai
Published: October 2002

An electron cyclotron resonance (ECR) plasma with large diameter was produced using a multi-slot antenna (MSA). The plasma parameters in silane gas were measured as functions of microwave power and gas flow rate with a heated Langmuir probe and a microwave interferometer. The dependences of the plasma parameters on the gas flow rate were studied in detail. As the gas flow rate was increased, the electron temperature decreased and the electron density decreased while the positive ion density initially decreased and finally tended to increase at above 30 sccm. It was also found that the negative ion density is high, and increases with increasing gas flow rate. The ion temperature in He and H2 was measured with an ion sensitive probe (ISP). The features of the I-V curve of the ISP indicate that many negative ions are produced in H2 plasma and that the negative ion density increases with increasing microwave power.
Mode Jumps and Hysteresis in Surface-Wave Sustained Microwave Discharges
Authors: Ivan Ghanashev Ivan Ghanashev , Masaaki Nagatsu Masaaki Nagatsu , Ge Xu Ge Xu , Hideo Sugai Hideo Sugai
Published: October 2002

Various electromagnetic surface modes along a finite area dielectric interface can sustain large area overdense plasmas. Mode jumps between these modes have been reported when changing the gas pressure. In this paper we report similar mode jumps caused by changing the wave power at fixed gas pressure. A simple theoretical analysis is proposed to explain this phenomenon on the basis of the resonance behavior of the chamber impedance and a stability criterion is formulated. The theory predicts a hysteresis in the power-density dependence, which was also observed experimentally.
Pressure and Electrode Distance Effects on Ion Energy Distributions in RF Discharges
Authors: Zeuner Michael , Meichsner Horst Neumann
Published: October 2002

We measured quasi-simultaneously the energy distributions of positive ions at the powered RF and grounded electrode of a parallel plate 13.56 MHz discharge using an energy selective mass spectrometer. The resulting ion energy distributions show the discharge potential conditions expected from a capacitive sheath model. Effects of the discharge pressure on the collision probability in the sheath, on the tendency of the sheath thickness, and on the effective discharge geometry are clearly demonstrated. The main ionization region is located in front of the powered electrode sheath, and the probability of ions reaching the opposite grounded electrode is characteristically influenced by discharge pressure and electrode distance.
Loss Processes of N 2 (A 3Σu
+) by Harmful Gases
Authors: Susumu Suzuki Susumu Suzuki , Haruo Itoh Haruo Itoh , Hisashi Sekizawa Hisashi Sekizawa , Nobuaki Ikuta Nobuaki Ikuta
Published: October 2002

Loss processes of metastable nitrogen molecules A3 Σu
+ in a Townsend discharge have been investigated in N2/NO, N2/CCl2F2 and N2/CH2FCF3 mixtures. The collisional quenching rate coefficients of N2(A3 Σu
+) by NO, CCl2F2 and CH2FCF3 are determined using a new theory which takes the reflection at the boundary into account in solving the diffusion equation. The collisional quenching rate coefficients of N2(A3 Σu
+) by NO, CCl2F2 and CH2FCF3 are 4.75×10-11, 8.32×10-13 and 2.96×10-15 cm3s-1, respectively.
Surface Reaction Kinetics of CH 3 in CH 4 RF Discharge Studied by Time-Resolved Threshold Ionization Mass Spectrometry
Authors: Masaharu Shiratani Masaharu Shiratani , Jacques Jolly Jacques Jolly , Hervé Videlot Hervé Videlot , Jérôme Perrin Jérôme Perrin
Published: October 2002

The surface loss probability β of CH3 radicals on a-C:H surface is determined by time-resolved threshold ionization mass spectrometry in pulsed RF discharges. In the post-discharge, the β value decreases from 0.011–0.015 to 0.001–0.002 in about 10 ms. This time evolution suggests that the loss probability depends on incoming ion and radical fluxes on the surface. We present a simple model of the surface reaction kinetics in which the number of active chemisorption sites on the surface is determined by the balance between their production, due to ions and/or H, and their annihilation, due to CH3 radicals. The model describes fairly well the observed decay of the CH3 radical density and the time evolution of β determined experimentally in the afterglow. The maximum contribution of the CH3 radicals to the deposition rate of a-C:H films was deduced to be about 60% of the total deposition rate determined experimentally.
Numerical Simulation of Etching and Deposition Processes
Authors: Satoshi Hamaguchi Satoshi Hamaguchi , Anita A. Mayo Anita A. Mayo , Stephen M. Rossnagel Stephen M. Rossnagel , David E. Kotecki David E. Kotecki , Keith R. Milkove Keith R. Milkove , Cindy Wang Cindy Wang , Curtis. E. Farrell Curtis. E. Farrell
Published: October 2002

Accurate numerical simulation of microscopic surface topography evolution can facilitate the development of various etching and deposition processes for microelectronics applications. We have used numerical simulator SHADE, which is based on the shock-tracking method for surface evolution, to simulate processes that involve simultaneous etching and deposition. Examples are taken from two applications: conformal metal liner formation by the ionized magnetron sputter deposition process and Pt etching by ion beam and reactive ion etching processes. The numerical methods used for simulation and comparison between the simulation results and experimental observations are presented.
Simulation of Plasma Production and Chemical Reaction in an Oxide Deposition Apparatus Using Electron Cyclotron Resonance Plasma
Authors: Tamotsu Morimoto Tamotsu Morimoto , Yasuyoshi Yasaka Yasuyoshi Yasaka , Masaki Tozawa Masaki Tozawa , Takashi Akahori Takashi Akahori , Hideaki Amano Hideaki Amano , Nobuo Ishii Nobuo Ishii
Published: October 2002

A two-dimensional fluid simulation code is developed which can predict plasma properties and chemical species transport in gas phase in a realistic configuration of a production-line apparatus. The code is applied to an electron cyclotron resonance plasma reactor for oxide deposition on 20-cm wafers. The predicted density in Ar plasma is in good agreement with the experimental result. Two-dimensional distributions of radical densities in plasmas with gas mixtures of Ar/O2/SiH4 and Ar/O2/SiF4 are obtained, which are in accordance with the measured deposition rates of SiO2 and SiOxFy, respectively.
Monte Carlo Simulation of Discharge Plasmas Using Fine Subslabs
Authors: Makoto Goto Makoto Goto , Yoshiomi Kondoh Yoshiomi Kondoh , Akio Matsuoka Akio Matsuoka
Published: October 2002

A self-consistent Monte Carlo modelling technique has been developed to study discharge plasmas. The fine subslab technique and weight probability method are introduced. These two methods are applied to a DC Ar-like gas discharge simulation. The disharge profiles obtained are in good agreement with the experimental ones. The electron energy loss mechanism in the cathode region is explained in detail. The electron energy distribution variation in the cathode fall and flat plasma density regions are expressed in a wide range of magnitude. The electron mean energy profile has a local minimum point which corresponds to the maximum excitation collision point. An electron group with the energy of 6 to 10 eV is observed in the flat plasma density region. This energy corresponds to the potential differnce from the maximum excitation collision point to this flat region. Electron energy distributions have a wide range of over 6 orders of magnitude with only 5000 test particles.
Reactive Ion Etching of Co–Zr–Nb Thin Film Using BCl3
Authors: Katsutaro Ichihara Katsutaro Ichihara , Michiko Hara Michiko Hara
Published: October 2002

Chlorine-based reactive ion etching (RIE) of a high-permeability Co–Zr–Nb film has been carried out. The etching rate was only about 10 nm/min in pure Cl2 in the temperature range in which anisotropic ion etching was dominant. Addition of BCl3 to the Cl2 resulted in an increase in the etching rate at low temperature. The activation energy in BCl3–Cl2 RIE was about 0.5 eV, whereas that in pure Cl2 RIE was 1.0 eV. The optimum BCl3 content was around 30 vol.%. The etching rate reached 750 nm/min at 1.2 W/cm2 RF power density and 300° C etching temperature. This improvement is due to the heavier mass and the higher ionization rate of BCl3 than those of Cl2. The ratio of the side etching rate to the depth-etching rate was about 30%, when the RF power density was 1.2 W/cm2 in BCl3–Cl2 RIE. The side etching was suppressed by both an increase in the RF power and addition of SiCl4 or SiCl4–O2 to the BCl3–Cl2. Anisotropy was promoted by both an increase in the ion energy and sidewall protection by Si or Si-oxide. An etching rate of 200 nm/min at 150° C and 2 W/cm2 RF power density in BCl3–Cl2–SiCl4 RIE has been achieved. The etching selectivity vs SiO2 was 20 and the side-etching rate was only 2% of the depth-etching rate.
Removal of Carbon Tetrachloride From Air Stream by A Corona Torch Plasma Reactor
Authors: Chang Jen-Shih , Myint Tin , Miziolek Alok Chakrabarti
Published: October 2002

Non-thermal plasma technologies offer an innovative approach to the problem of decomposing various volatile organic compounds (VOCs) in the paint and semiconductor industries. We focussed our attention on corona torch plasma reactors to study the decomposition destruction efficiency for carbon tetrachloride at 400 to 8600 ppm level in dry air. The effects of gas flow rate, concentration and reactor operating conditions on the decomposition and analysis of reactant conversion of carbon tetrachloride were investigated. Experimental results show that the destruction efficiencies of carbon tetrachloride depend nonmonotonically on discharge power or applied voltage and increase with decreasing gas flow rate. No significant O3, NO

x

, N2O and CO are observed as the by-products of discharge in air. CO2, H2O, Cl2 and HCl are observed to be the final products of carbon tetrachloride destruction.
Formulation of Power Loss Equation for an Emitter with Dot Contacts and Proposal of an Improved Emitter Structure in Silicon Solar Cells
Authors: Ohtsuka Hiroyuki , Muramatsu Shin-ichi , Nagata Yasushi , Sakamoto Masahiko , Tsutsui Ken , Tsuyoshi Uematsu Tsuyoshi Uematsu , Terunori Warabisako Terunori Warabisako
Published: October 2002

A new two-dimensional emitter power-loss equation was formulated for a cell with a dot contact and verified numerically. Based on this formulation, the current crowding that occurs in two-dimensional geometry was evaluated. We propose a solar cell structure with line-shaped heavily diffused emitters under the dot contacts. The effectiveness of the proposed emitter geometry was verified by both calculation and measurement, and the formulation was found to be valid.
Writing Bits of Longitudinal Quantized Magnetic Disk Using Magnetic Force Microscope Tip
Authors: Kong Linshu , Shi Rick C. , Peter R. Krauss Peter R. Krauss , Stephen Y. Chou Stephen Y. Chou
Published: October 2002

Longitudinal quantized magnetic disks (QMDs) consisting of discrete single domain Ni bars on a silicon substrate with a density of nearly 2 Gbis/in.2 were fabricated. A magnetic force microscope (MFM) tip with a large magnetic moment has been used to successfully write individual bits of the QMD by simply positioning the tip near one end of a Ni bar. It was found that the MFM tip can write each individual bit perfectly without writing the neighboring bits. This is attributed to the fact that the magnetization of each QMD bit has only two stable quantized values and therefore the writing process is quantized.
Improvement of Cathodoluminescence for ZnGa2O4 Phosphor by Second Fired Process
Authors: Su-Hua Yang Su-Hua Yang , Meiso Yokoyama Meiso Yokoyama
Published: October 2002

This study examines the feasibility of using the emission material of ZnGa2O4 phosphor in field emission display (FED). ZnGa2O4 is a low-voltage cathodoluminescent phosphor having a spinel structure. ZnGa2O4 phosphor obtained from the first fired process has low luminance intensity and low efficiency. Treating the secondary fired process can markedly enhance the crystallization and cathodoluminescent properties of ZnGa2O4 phosphor. Among these improvements include a decrease in the values of full width at half maximum (FWHM) of X-ray diffraction (XRD), along with an obvious increase in the luminance intensity and efficiency of ZnGa2O4 phosphor. The maximum luminance intensity and efficiency of ZnGa2O4 phosphor obtained by the secondary fired treatment processes are 2050 cd/m2 and 0.198 lm/W, respectively. In addition, the CIE chromaticity coordinate of the ZnGa2O4 phosphor is X=0.1696, Y=0.1608. Moreover, the emission color is blue.
β-SiC Photodiodes Prepared on Silicon Substrates by Rapid Thermal Chemical Vapor Deposition
Authors: Wu Kuen-Hsien , Fang Yean-Kuen , Jing-Hong Zhou Jing-Hong Zhou , Jyh-Jier Ho Jyh-Jier Ho
Published: October 2002

β-SiC photodiodes were fabricated on Si substrates by rapid thermal chemical vapor deposition (RTCVD). Experimental results show that the developed photodiodes have a peak photoresponsivity at 575 nm which corresponds to the visible light between yellow and green. These photodiodes display a low dark current of about 10 nA and 5 µ A at reverse biases of 1 V and 10 V, respectively, and have an optical gain of about 97 under an incident light power of 5 µ W and a reverse bias of 14.5 V. Dark-current levels versus reverse bias have also been measured as a function of temperature, and the results indicate that these diodes can operate at elevated temperatures above 200° C. Thus β-SiC is a candidate for optoelectronic devices on Si substrates in applications, where low cost, silicon compatibility, and high-temperature operation are the prime considerations.
Super-Resolution Disk with a Photochromic Mask Layer
Authors: Tsuyoshi Tsujioka Tsuyoshi Tsujioka , Minoru Kume Minoru Kume , Yukio Horikawa Yukio Horikawa , Atsushi Ishikawa Atsushi Ishikawa , Masahiro Irie Masahiro Irie
Published: October 2002

Super-resolution readout for read-only optical disks was demonstrated using a photochromic mask layer. Nonlinear transmittance change, which is desirable for effective super-resolution readout, was achieved using a the photochromic mask layer with an optical density of 0.5. The photochromic super-resolution method is expected to increase the recording density of not only read-only disks, but also magneto-optical and phase change disks.
The Hydrophilization of Process Wafers in Dilute Hydrogen Peroxide Solutions and Ozonated Deionized Water and Its Effects on Defects and Gate Oxide Integrity
Authors: Jin-Goo Park Jin-Goo Park
Published: October 2002

The purpose of this study is to explore the effect of hydrophilization of wafer surfaces on defects and gate oxide integrity in metal-oxide semiconductor (MOS) devices. After HF treatment, dilute H2O2 solutions and ozonated deionized (DI) water were used as the final cleaning chemical to hydrophilize wafer surfaces. The defects created on patterned hydrophilic wafers were the least compared with patterned hydrophobic wafers or wafers with a mixture of both surfaces. The defects created on spin dried patterned hydrophobic wafers were water marks. The concentrations of Al, Ca and K observed in dilute H2O2 solutions and ozonated DI water were slightly higher than in DI water. Minority carrier lifetime values were the highest in HF last treated wafers and the lowest in those treated in dilute H2O2 solutions. MOS capacitors were fabricated to evaluate the gate oxide integrity when different cleaning procedures were applied. The distribution of breakdown range of devices shifted to a higher region on the application of HF and ozonated DI water. Dilute H2O2 solutions resulted in a poor breakdown field distribution. Ozonated DI water treated wafers showed higher breakdown field distributions than HF-last.
1.95-µm-wavelength InGaAs/InGaAsP Laser with Compressively Strained Quantum Well Active Layer
Authors: Dong Jie , Akinori Ubukata Akinori Ubukata , Koh Matsumoto Koh Matsumoto
Published: October 2002

In this study, we demonstrate the low pressure metalorganic chemical vapor deposition growth of highly compressively strained quantum well structures with large well thickness for extending the emission wavelength of InGaAs/InGaAsP lasers. By comparing the photoluminescence characteristics of quantum wells grown at different temperatures, it is clarified that a relatively high quality quantum well layer emitting at 2.0 µ m can be obtained at a growth temperature of 650° C. At 20° C, an 880-µ m-long double quantum-well laser operating at 1.946 µ m exhibits a threshold current as low as 14.6 mA, maximum output power higher than 10 mW and external differential quantum efficiency of 18.5%. The characteristic temperature is as high as 50 K.
Two Step Rapid Heating Reflow of Borophosphosilicate Glass and Estimation for a Coefficient of Heating Delay by Thermal Analyses
Authors: Furukawa Masakazu , Kamegaya Hiroshi , Haruna Ikuo Ono
Published: October 2002

The reflow of borophosphosilicate glass (BPSG) was studied by the rapid heating technique in two step irradiations using a halogen lamp. Pre-annealing (800° C, 30 s) during the first step irradiation, which aims to reduce the heating delay for the BPSG film, was carried out prior to high temperature heating (1050–1200° C, 20 s). The reflow angle with pre-annealing is consistently smaller than that without pre-annealing. Moreover, the reflow difference between with pre-annealing and without pre annealing decreases with increasing temperature because the heating delay for the BPSG film increases. The heating delay is primarily caused by thermal resistance between the film and the silicon wafer because, as the result obtained from the finite element method indicated, the heat conduction delay between the film surfaces was negligibly small. The equation for heat resistance can be solved analytically and the thermal resistance coefficient can be estimated by this solution, using the physical parameters of the film and the experimental results.
Partial-Response Maximum-Likelihood Detection Method for Magneto-Optical Recording
Authors: Narahara Tatsuya , Aratani Katsuhisa , Atsushi Fukumoto Atsushi Fukumoto , Shin Masuhara Shin Masuhara
Published: October 2002

We detected bits sized at 0.237 µm bit length and 0.85 µm track pitch recorded by magnetic field modulation on a magneto-optical disk with a 690-nm laser diode and 0.60-numerical-aperture-objective using a partial-response maximum-likelihood detection method. We confirmed that the optimum partial-response for this high linear density had four coefficients of 1 by analyzing difference metrics of error critical paths. The recorded bits with areal density of 5.6 bit/µm2 were also detected at a low error rate, which combination is 0.237-µm bit length and 0.75-µm track pitch. Its write power tolerance is limited to ±22%.
Highly Selective SiO2 Etch Employing Inductively Coupled Hydro-Fluorocarbon Plasma Chemistry for Self Aligned Contact Etch
Authors: Iijima Yukio , Ishikawa Yoshio , Yang Chan-lon , Chang Mei , Okano Haruo
Published: October 2002

An inductively coupled plasma chemistry including hydro-fluorocarbon gas ( CHF3, CH2F2 or CH3F) in addition to C4F8 and Ar was developed for the self aligned contact process of LSI. The additional gases effectively reduces the etch rate of the nitride stopper in the contact hole resulting an increased selective ratio. The effect becomes more marked with higher H numbers. The optical emission signals of both F radical and carbon, including radicals such as C2, CF and CF2, were decreased by the addition of CH3F. The improved selectivity is considered to be due to the increased concentration of radicals with C–H bonding. The effect of C–H including radicals was explained by the enthalpy of reaction with oxygen and nitrogen atoms to form CO or CN bonding, and an improved step coverage of the polymerized film protecting the nitride surface.
Characterization of Silicon Native Oxide Formed in SC-1, H2O2 and Wet Ozone Processes
Authors: Ohwaki Takeshi , Takai Mikako Takeda
Published: October 2002

The structures of silicon native oxides formed in the SC-1, H2O2 and wet ozone processes were characterized using X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy (FT-IR). Spectral simulation was performed to clarify the FT-IR spectra, assuming that the native oxide was pure silicon dioxide. Effective medium theories were applied to understand deviations of the observed spectra from the calculated ones. The deviations between the native oxide thickness evaluated by XPS and the absolute thickness obtained by TEM were also discussed. These deviations can be explained if the void is incorporated in the native oxides and the interface between the native oxide and the basal silicon obtained by the wet ozone process has a relatively smooth surface and a structure more similar to that of pure silicon dioxide, compared with that obtained by SC-1 or H2O2 treatment.
Characterization of 3C-SiC Epitaxial Layers on TiC(111) by Raman Scattering
Authors: Harima Hiroshi , Nakashima Shin-ichi , Carulli John M. , Jr. Charles P. Beetz, , Yoo Woo S.
Published: October 2002

3C-SiC epitaxial layers of 0.3–4 µ m thickness deposited on TiC(111) have been investigated by Raman microprobe. Relatively thick layers showed TO- and LO-phonon bands with peak frequencies higher than those of bulk reference by about 5.8 cm-1 and 3.6 cm-1, respectively. This frequency upshift is due to residual stress in the epi-layers. The in-plane, compressive, biaxial stress is estimated to be 1.7 GPa, and there are 0.24% in-plane compressive strain and 0.10% tensile strain in the normal direction. The in-plane strain is 2–3 times smaller than those expected from the lattice mismatch, or from the difference in thermal expansion coefficient between the epi-layer and the substrate. In spite of a small lattice mismatch between 3C-SiC and TiC, the residual in-plane stress is larger than that reported for 3C-SiC on Si which has much larger lattice mismatching.
Energy Transfer from Eu2+ to Mn2+ in MgS:Eu2+, Mn2+
Authors: Nobuhiko Yamashita Nobuhiko Yamashita , Atsumi Takagoshi Atsumi Takagoshi
Published: October 2002

Photoluminescence and excitation spectra are observed for MgS: EuF3 (0.01 mol%) and MgS: EuF3 (0–0.05 mol%), MnF2 (1 mol%) powder phosphors at 10, 80 and 300 K. At 300 K, the emission spectra of the doubly activated phosphors of MgS: Eu2+, Mn2+ consist of three bands at 592 nm (attributed to Eu2+), 700 nm (attributed to Mn2+) and 820 nm. Their shapes depend on the Eu2+ concentration and the excitation wavelength. We can see direct evidence of the energy transfer from Eu2+ to Mn2+ in the emission and excitation spectra of MgS: Eu2+, Mn2+. The new emission band observed at 820 nm is attributed to the center associated with both Eu2+ and Mn2+, e.g. the paired-ion center of the Eu2+ and Mn2+ ions.
Crystal Orientation Dependence of Piezoelectric Properties in Lead Zirconate Titanate: Theoretical Expectation for Thin Films
Authors: Du Xiao-hong , Uma Belegundu Uma Belegundu , Kenji Uchino Kenji Uchino
Published: October 2002

Crystal orientation dependence of piezoelectric properties has been calculated phenomenologically for lead zirconate titanate (PZT) in the three-dimensional space. The calculation has been made for tetragonal PZT 40/60 (40% PZ and 60% PT) and rhombohedral PZT 60/40 compositions. The maximum longitudinal piezoelectric constant d
33 and electromechanical coupling factor k
33 in the rhombohedral composition were found to be at 57° and 51° angles, respectively, canted from the spontaneous polarization direction. This suggests that thin film piezoelectric actuators or sensors should employ a rhombohedral composition with the perovskite [100] epitaxially-oriented configuration.
Effect of a TiO2 Buffer Layer on the C–V Properties of Pt/PbTiO 3/TiO 2/Si Structure
Authors: Chulsoo Byun Chulsoo Byun , Yong-Il Kim Yong-Il Kim , Won-Jong Lee Won-Jong Lee , Byong-Whi Lee Byong-Whi Lee
Published: October 2002

Metal/ferroelectric/insulator/semiconductor (MFIS) capacitors were prepared by depositing PbTiO3 and TiO2 layers on Si(100) wafers at 450 and 550°C using metal organic chemical vapor deposition (MOCVD). The C–V properties of the capacitors depend on the quality of TiO2 films and TiO2/Si interfaces. The TiO2 film could serve as an effective buffer layer against the Pb diffusion and provide good C–V properties as long as it was deposited at proper substrate temperature with proper thickness.
Characterization of Epitaxial ZnSe/GaAs (100) Interface Properties and Their Control by (HF+Se)-Pretreatment
Authors: Yamagata Yuji , Sawada Takayuki , Suzuki Kazuaki Imai
Published: October 2002

Interface properties of molecular beam epitaxy (MBE)-ZnSe/GaAs (100) substrate systems formed after various pretreatments of the substrate surface, including standard chemical etching, and (NH4)2S

x

-, HF-, Te-, Se- and (HF+Se)-pretreatments, have been characterized by C–V, deep level transient spectroscopy (DLTS) and I–V measurements. A comparative study of the quality of the grown epilayer has also been made by X-ray diffraction (XRD) and Raman scattering measurements. It is found that the (HF+Se)-pretreatment gives superior interface with minimum interface state density, N
ss,min, which is smaller than 1×1011 cm-2 eV-1 below the midgap of GaAs. The value is about a thirtieth of the standard chemically etched sample. The influence of interface states on I–V characteristics across the interface is also analyzed on the basis of a model which takes interface charge into consideration. The excess voltage drop at the interface is considerably reduced for the Se-pretreated sample, which is in agreement with the present model. The quality of the ZnSe epilayers assessed by XRD and Raman spectra is firmly correlated with the interface quality.
Breakdown Characteristics of RF Argon Capacitive Discharge
Authors: Masumi Sato Masumi Sato , Masafumi Shoji Masafumi Shoji
Published: October 2002

Measured breakdown characteristics of a capacitively coupled rf argon discharge at 13.56 MHz are compared with breakdown criterion derived from the electron balance model in which the difference between the longitudinal and transverse electron diffusion coefficients is taken into account. For the right-hand branch of the minimum of V-shaped breakdown voltage curves, good agreement between the observed and predicted criteria is found in the case of short electrode separations when the electron formation rate is calculated in terms of the time-averaged ionization frequency.
High Density Optical Recording on Dye Material Discs: An Approach for Achieving 4.7 GB Density
Authors: Hamada Emiko , Fujii Toru , Iimura Yuji Tomizawa
Published: October 2002

High density optical media is proposed together with a recording method for achieving a density of 4.7 GB per single 12 cm diameter disc at a recording speed of 3.5 m/s.
Development of Low Dielectric Constant Ferroelectric Materials for the Ferroelectric Memory Feild Effect Transistor
Authors: Yoshikazu Fujimori Yoshikazu Fujimori , Naoki Izumi Naoki Izumi , Takashi Nakamura Takashi Nakamura , Akira Kamisawa Akira Kamisawa , Yasuhiro Shigematsu Yasuhiro Shigematsu
Published: October 2002

In this paper
we discuss ferroelectric materials suitable for a metal-ferroelectric-metal-
insulator-semiconductor feild effect transistor (MFMIS FET).
It is important for a ferroelectric material to have a low dielectric constant
to enable the application of
sufficient electric field to a ferroelectric layer.
Films of Sr2Nb2O7 and Sr2(Ta1-x
Nbx)2O7
were prepared by the sol-gel method on Pt/IrO2 electrodes for an MFMIS FET.
The ferroelectricities of Sr2(Ta1-x
Nbx)2O7 films were confirmed
to be in the range of x=0.1–0.3.
In the case of x=0.3, the largest remanent polarization was obtained in the
hysteresis loop.
The values of the remanent polarization and the coercive field are
0.5 µC/cm2 and 44 kV/cm, respectively.
The film has a low dielectric constant (ε r=53).
The characteristics of Sr2(Ta1-x
Nbx)2O7 thin films
are suitable for MFMIS FET.
Low-Temperature Mixed Sintering of Pb(Zr1-xTix)O3–Pb(Zn1/3Nb2/3)O3 Ceramics and Their Pyroelectric Properties
Authors: Futakuchi Tomoaki , Tanino Kastumi , Sawasaki Hironobu , Adachi Masatoshi , Kawabata Akira
Published: October 2002

Low-temperature mixed sintering in the preparation process of
Pb(Zr1-
x

Ti

x

)O3–Pb(Zn1/3Nb2/3)O3 ceramics has been examined.
Dense composite ceramics having x=0.02, 0.03 and 0.04 with
fine grains were obtained at firing temperatures from 900° C to
950° C by adding PbO as a lower-melting-point sintering aid. The
pyroelectric coefficient of this mixed sintered ceramic fired at
900° C was above 60 nC/( cm2· K) in the temperature range of 15° C to
50° C. These low-temperature mixed sintering pyroelectric
materials are very promising for use in the fabrication of highly
sensitive infrared detectors.
The Effects on Metal Oxide Semiconductor Field Effect Transistor Properties of Nitrogen Implantation into p+ Polysilicon Gate
Authors: Yasuoka Akihiko , Kuroi Takashi , Shimizu Satoshi , Shirahata Masayoshi , Okumura Yoshinori , Inoue Yasuo , Inuishi Masahide , Tadashi Nishimura Tadashi Nishimura , Hirokazu Miyoshi Hirokazu Miyoshi
Published: October 2002

We have studied in detail the effects of nitrogen implantation into a p+ polysilicon gate on gate oxide properties for the surface p-channel metal oxide semiconductor (PMOS) below 0.25 µm. The nitrided oxide film can be easily formed by the pile-up of nitrogen into the gate oxide film from the polysilicon gate. It was found that boron penetration through the gate oxide film can be effectively suppressed by nitrogen implantation into a p+ polysilicon gate because nitrogen in the polysilicon film can suppress boron diffusion, and the nitrided oxide film can also act as a barrier to boron diffusion. Moreover the hot-carrier hardness can be remarkably improved by the nitrided oxide film since interface state generation can be suppressed by the nitrided oxide film. Furthermore the number of electron traps in the gate oxide film can also be reduced by nitrogen implantation.
Near-Band-Edge Photoluminescence of GaAs Epitaxial Layers Grown at Low Temperature
Authors: Abe Hajime , Shin-ichi Nakashima Shin-ichi Nakashima , Hiroshi Harima Hiroshi Harima
Published: October 2002

Photoluminescence and reflectance spectra in a near-band-edge region have been measured for homo-epitaxial GaAs layers grown at low temperature (LT-GaAs layers; temperatures from 200 to 265°C). It is found that the photoluminescence spectrum depends strongly on the growth conditions. A narrow hole (dip) is observed in the emission band for samples prepared under certain growth conditions. The dependence of the dip profile on the ambient temperature, excitation power, excitation energy and growth conditions has been studied in detail. The spectral hole is attributed to the free exciton absorption in the top layer for luminescent light emitted from the underlying layer of LT-GaAs. The experimental results show that the spectral profile of the photoluminescence reflects the crystal quality and microstructure of the LT-GaAs layers.