bluuebunny/crossref_metadata_2025 huggingface dataset:
Grain Size Dependence of Dielectric Constant for Modified (Pb0.63Ba0.37)(Zr0.7Ti0.3)O3Ceramic Material
Authors: Sato Yuichi , Hideyuki Kanai Hideyuki Kanai , Yohachi Yamashita Yohachi Yamashita
Published: October 2002

The grain size dependence of the dielectric constant for a modified (Pb0.63Ba0.37)(Zr0.7Ti0.3)O3material from -55° C to 150° C has been studied. Grain sizes in the range of 1.2 µ m to 7.0 µ m were prepared by varying the sintering temperature and time. The maximum dielectric constant decreased monotonously as the grain size decreased. The dielectric constant at a lower temperature for the ferroelectric phase (-55° C) also decreased monotonously. However, at a high temperature for the cubic phase (150° C), the dielectric constant was almost constant. This monotonous decrease of the dielectric constant at a lower temperature is the same phenomenon as for the Pb(Mg1/3Nb2/3)O3material. The Curie temperature of the ceramic shifted toward a higher temperature as the grain size was reduced. However, the aging rate was almost independent of the grain size.
Dielectric Constant of Silicon Dioxide Deposited by Atmospheric-Pressure Chemical Vapor Deposition Using Tetraethylorthosilicate and Ozone
Authors: Katsumi Murase Katsumi Murase
Published: October 2002

The dielectric constant of tetraethylorthosilicate (TEOS)/O3 chemical vapor deposited silicon dioxide ( TEOS/O3-NSG) ranges, within the extent of this work, from 4 to 6, depending on both the deposition conditions and the substrate material. Although their influences on the dielectric constant are complicated, changes in the dielectric constant can be described by a single variable: the amount of H2O-elated components in TEOS/O3-NSG. The relationship between the dielectric constant and the amount of H2O-related components is in accordance with the Clausius-Mossotti relationship. The dielectric constant also varies with measurement temperature in line with the Debye orientational polarization. A rough estimate of the concentration of permanent electric dipoles is close to the number of H2O molecules desorbed thermally per unit volume of TEOS/O3-NSG.
Microstructural Characterisation of Hexagonal (Ag, Cu)Zn4Alloys in the Deformed and As-Cast State
Authors: Pal Hiranmay , Swapan Kumar Pradhan Swapan Kumar Pradhan , Madhusudan De Madhusudan De
Published: October 2002

Zn-based ternary alloys containing Ag and Cu as solutes having characteristic hexagonal close-packed (hcp) structure (Ag, Cu)Zn4have been studied for microstructural evolution in the deformed and as-cast state in order to correlate the microstructure with mechanical property of the materials. X-ray diffraction (XRD) line profile analysis, optical microscopy and scanning electron microscopy (SEM) have been used to study the microstructure and the mechanical property studied through the measurement of microhardness. X-ray studies of the deformed alloys reveal increased influence of solute Cu in the generation of deformation stacking fault of density α with increasing solute concentration. A reasonably good estimate of stacking fault energy parameter (γ/µ) for the alloys has also been made. Increased influence of solute Cu has also been observed to control the grain sizes and microhardness. A close correlation could be establised between the microstructural parameters and microhardness signifying the interdependence of mechanical property with microstructure of the alloys.
Measurement of Thermal Conductivity of Ultrapure Copper at Low Temperatures
Authors: Norio Yamamoto Gang Ke
Published: October 2002

Ultrapure copper with purity of 99.99999% (7N) was prepared and its thermal conductivity was measured by a steady-state method, from 4.2 K to 90 K. The apparatus for ultrapure copper measurement is introduced and the measured data are presented in this paper. As a result, the peak of thermal conductivity is measured to be 45200 W/m·K when the temperature is 6.51 K. The measured data are compared with data in literature and with the value calculated by theory.
Solution of Hyperbolic Heat-Conduction Equation with Relaxation Time of High-Speed Thermal Wave
Authors: Kanji Etori Kanji Etori
Published: October 2002

A hyperbolic heat-conduction equation is solved for a solid of finite length at low temperatures using the Laplace transformation with the Fourier series under thermal insulation. As a result, the solution expressed with respect to both relaxation time of a high-speed thermal wave and thermal diffusivity of the solid is compared with that derived from a conventional parabolic heat-conduction equation at high temperatures.
A Comparative High-Resolution Electron Microscope Study of Ag Clusters Produced by a Sputter-Gas Aggregation and Ion Cluster Beam Technique
Authors: Hohl Georg-Friedrich , Hihara Takehiko , Sakurai Masaki , Oishi Takashi , Wakoh Kimio , Kenji Sumiyama Kenji Sumiyama , Kenji Suzuki Kenji Suzuki
Published: October 2002

Ag clusters were formed by a sputter-gas-aggregation process [H. Haberland et al..: J. Vac. Sci. Technol. A 10 (1992) 3266] and the ionized cluster beam (ICB) [T. Takagi: Ionized-Cluster Beam Deposition and Epitaxy (Noyes, Park Ridge, 1988)] technique. The Ag clusters deposited on collodion-coated microgrids were investigated by high-resolution transmission electron microscopy. The diameter of those clusters, d, ranges from 1 nm up to about 10 nm for specimens produced by the sputter-gas aggregation technique, depending on the sputter condition and the deposition time. Comparable times of the ICB deposition lead to a broader distribution up to d≈20 nm, suggesting the formation of islands with extremely flat shapes. High percentages of crystalline particles obtained by both techniques are either single crystals or multiple twins with clear lattice images.
Thermal Stability of W2N Film as a Diffusion Barrier between Al and Si
Authors: Noya Atsushi , Takeyama Mayumi , Sasaki Katsutaka , Aoyagi Eiji , Hiraga Kenji
Published: October 2002

Thermal stability of the contact system of Al/W2N/Si is studied by characterization techniques of cross-sectional transmission electron microscopy, X-ray diffraction and Auger electron spectroscopy. It is revealed that the effective suppression of grain growth of W2N barrier is important to the total stability of this system.
Photooptical Switching of Polymer Film Waveguide Containing Photochromic Diarylethenes
Authors: Norihisa Tanio Norihisa Tanio , Masahiro Irie Masahiro Irie
Published: October 2002

Fabrication of a photooptical switching device based on the photo-induced refractive index change of polymer film doped with photochromic compounds is described. 1,2-bis(2-methylbenzo[b]thiophen-3-yl) perfluorocyclopentene (BFCP) and 1,2-dicyano-1,2-bis(2,4,5-trimethyl-3-thienyl)ethene (CMTE) were used as the photochromic compounds. A transformation in the compounds from the opened-ring to closed-ring form was induced by irradiation with a He–Cd laser (325 nm) and the reverse reaction with an Ar ion laser (488 nm). The polymer films containing BFCP and CMTE showed a refractive index change, Δn, as large as 5×10-4/ wt% photoisomerized chromophores. Photooptical switching of a prism-coupling device was demonstrated by alternate irradiation with Ar ion and He–Cd lasers, and also by irradiation with a pulsed YAG laser.
Variable-Characteristic Reference Solar Cells by Computer Synthesis
Authors: Kenji Nakahara Kenji Nakahara
Published: October 2002

In this paper we proposes a reference cell with variable spectral response characteristics to be used for measurement of various rypes of solar cells, and describe the design and experimental manufacturing of such a reference cell. The reference cell consists of a c-Si cell, a filter wheel mounted with 15 sharp cut-off filters, and a computer. In this system, characteristic synthesis of output light signals through each filter is done rapidly by the computer, thus realizing a cell having arbitrary characteristics. The composite wavelength ranges from 320 nm to 850 nm with a minimum control width of 40 nm. This system can function as 5 reference cells simultaneously, and has a continuous display with the response rate of once per second. The accuracy of measurement was within ±2%, which proves the practicality of the system.
New Dry Surface-Imaging Process for X-Ray Lithography
Authors: Ogawa Taro , Yamaguchi Atsuko , Soga Takashi , Tachibana Hiroaki , Matsumoto Mutsuyoshi , Oizumi Hiroaki , Eiji Takeda Eiji Takeda
Published: October 2002

Ultra-LSIs (ULSIs) now require innovative microfabrication processes to achieve gigabit-scale integration. In order to meet this requirement, a new surface-imaging process involving the dry development of polysilane resist is investigated for use in X-ray lithography from the viewpoints of achieving a dry development process and of improving resolution. Poly(cyclohexylmethylsilane) (PCHMS) is used for the dry-developing surface-imaging layer. We confirm that PCHMS has positive-tone characteristics by ultraviolet (UV) absorption spectroscopy and photon-stimulated ion desorption (PSD) measurements. PSD analyses also clarify that chain side groups of polysilane are desorbed prior to Si–Si backbone desorption, and that heating drastically improves dry-development sensitivity. PCHMS patterns replicated by dry-development can be transferred to the bottom layer resist by O2 reactive-ion etching and, as a result, high-aspect-ratio resist patterns can be replicated. The possibility of applying this process to X-ray projection lithography is also discussed.
Tunable 397 nm Light Source for Laser Cooling of Ca Ions Based on Frequency Doubling of Diode Laser
Authors: Kazuhiro Hayasaka Kazuhiro Hayasaka , Masayoshi Watanabe Masayoshi Watanabe , Hidetsuka Imajo Hidetsuka Imajo , Ryuzo Ohmukai Ryuzo Ohmukai , Shinji Urabe Shinji Urabe
Published: October 2002

We have fabricated an rf ion trap and laser-cooling light sources to observe shelving transition in a single calcium ion. All the radiation required for laser cooling and observation of the transition can be prepared with diode lasers in this system. Continuous-wave radiation at 397 nm for laser cooling was generated by frequency doubling of a GaAlAs laser in an external enhancement cavity. As a preliminary experiment for observing the shelving transition, laser cooling of one hundred calcium ions was demonstrated using this radiation and another diode laser.
Sum-Frequency Generation near 194 nm with an External Cavity by Simultaneous Enhancement of Frequency-Stabilized Fundamental Lasers
Authors: Watanabe Masayoshi , Hayasaka Kazuhiro , Imajo Hidetsuka , Ryuzo Ohmukai Ryuzo Ohmukai , Shinji Urabe Shinji Urabe
Published: October 2002

Continuous-wave coherent radiation near 194 nm has been generated by sum-frequency mixing with simultaneous enhancement of both fundamental lasers. An output power of 31 µ W was obtained at 194 nm. The frequency of a Ti: sapphire laser, which was used as one of the fundamental lasers, was stabilized with a frequency fluctuation of 80 kHz rms by using a mode-interference method.
Development of All-Semiconductor Laser Sources for Studies of 88Sr+ Ions Confined in RF Trap
Authors: Musha Mitsuru , Zvyagin Andrei , Nakagawa Ken-ichi , Ohtsu Motoichi
Published: October 2002

Semiconductor-laser-based light sources have been developed for cooling and depopulating Sr+ ions confined in an rf trap. Single-mode laser oscillation at 422 nm and 21 µ W power was obtained, which corresponds to transition 5s 2S1/2-5p 2P1/2 of Sr+. An external-cavity-stabilized semiconductor laser with 1.8 mW power has been developed for pumping ions back from the 4d 2D3/2 metastable state to the cooling cycle. In this paper we present the reference spectrum for both lasers, which confirms the laser oscillation at appropriate transition of Sr+.
Computer-Controlled Narrow-Linewidth and Frequency-Stabilized AlGaAs Laser System with Unmodulated Output
Authors: Kawakami Jun , Kourogi Motonobu , Ohtsu Motoichi
Published: October 2002

A narrow-linewidth semiconductor laser system at 780 nm wavelength was developed, with frequency locked to the saturation absorption resonance frerquency of rubidium ( 87Rb). Optical feedback from an external Fabry-Perot cavity was employed to reduce the linewidth of the laser. The third derivative of the saturated absorption spectrum in 87Rb was used as a frequency demodulator for frequency locking, for which the Zeeman modulation was employed to keep the output power and frequency unmodulated. The minimum of the square root of the Allan variance was 2.1×10-12 at the integration time of 300 s. The full linewidth at half maximum of the field spectrum was measured to be narrower than 170 kHz. A computer-control program was developed for automatic frequency locking to the 87Rb line.
Long-Term Operation and Frequency Stability of an Optically Pumped Cesium Beam Frequency Standard with Sharp-Angle Incidence of Probing Laser Beam
Authors: Dong-Hai Yang Dong-Hai Yang , Yi-Qiu Wang Yi-Qiu Wang
Published: October 2002

In this paper the long-term continuous operation for more than two months of an optically pumped cesium beam frequency standard is described, and the frequency stability for one day of 2×10-13/ day has been obtained for the first time for such a frequency standard. This was achieved by applying digital auxiliary locking loop (DALL) devices for the frequency and temperature controllers of laser diodes, and also by using sharp-angle incidence of the probing laser beam.
Theoretical Analysis of the Power and Linewidth of the Diode-Laser-Pumped Rb87 Maser
Authors: Jinquan Deng Jinquan Deng , Xiwen Zhu Xiwen Zhu
Published: October 2002

We calculated the oscillation power and total linewidth of the diode-laser-pumped Rb87 maser with spatial variations of the pumping rate and the radiative microwave field in the resonance cell. It is found that the maximum oscillation power P
max corresponding to the optimum pumping rate Γ opt does not increase monotonically with the atomic density n
0 and that the short-term frequency stability of the maser corresponding to P
max is about a factor of three better than that currently obtained with a lamp-pumped Rb87 maser. Some results are in fair agreement with our previous experiments. We also examined the variation of the oscillation powers vs light intensity in an average mode for three laser-pumping schemes with different frequencies and polarizations of the diode lasers.
Stress Measurements in Silicon Substrates with TiSi2 Patterns Using Raman Microprobe
Authors: Ito Tadashi , Hirozumi Azuma Hirozumi Azuma , Shoji Noda Shoji Noda
Published: October 2002

The horizontal and depth distributions of the stress induced in silicon substrates with titanium silicide ( TiSi2) patterns were evaluated using the Raman microprobe. Tensile stress is generated beside the TiSi2 pattern. The tensile stress reaches a maximum value of 150–350 MPa at the distance of ∼0.5 µ m from the edge of the TiSi2 pattern, and the range of the tensile stress is as far as 2–4 µ m from the edge. Under the TiSi2 pattern, compressive stress is generated. The compressive stress becomes a maximum value of 25–75 MPa at the TiSi2/Si interface, and the depth of the compressive stress extends to 2–1 µ m.
Analytical Model to Determine the Gate Leakage Current in In0.52Al0.48As/InxGa1-xAs Pseudomorphic Modulation Doped Field-Effect Transistors Caused by Thermionic Field Emission
Authors: Dickmann Jürgen , Daembkes Heinrich , Schildberg Steffen , Fittng Hans-Joachim , Ellrod Peter , Tegude Franz Joseph
Published: October 2002

The gate leakage current of pulse doped In0.52Al0.48As/In

x

Ga1-
x

As pseudomorphic modulation doped field-effect transistors (MODFETs) is analysed by thermionic field emission theory. For the first time, a theoretically based investigation of the leakage current for this type of device is carried out. The influence of parameters of the layer structure design on the gate leakage current such as the thickness of the barrier layer or the doping concentration in the supply layer is predicted. The model adequately predicts the experimental decrease in leakage current with increased thickness of the barrier layer and reduced doping concentration.
A Rutherford Backscattering Spectroscopic Study of the Aluminum Antimonide Oxidation Process in Air
Authors: Shibata Tomohiro , Nakata Jyoji , Yasushi Nanishi Yasushi Nanishi , Masatomo Fujimoto Masatomo Fujimoto
Published: October 2002

The oxidation process of aluminum antimonide (AlSb) in air is investigated in detail using Rutherford backscattering spectroscopy (RBS). It is verified that AlSb is extremely liable to be oxidized by slight exposure to air. The oxidation is found to be a two-step process: an initial fast step and a subsequent slower one. In the initial step, a surface oxide with a thickness of about 150 Å is formed after AlSb is exposed to air for only a matter of minutes. This oxide gradually thickens in the subsequent step, reaching the AlSb/GaSb interface after exposure for about eighty hours. It is also clarified that the oxidized AlSb layer is amorphous and that a partly oxidized region is formed under the amorphous oxidized AlSb layer in a precursory state.
High-Quality Wide-Gap Hydrogenated Amorphous Silicon Fabricated Using Hydrogen Plasma Post-Treatment
Authors: Okamoto Shingo , Hishikawa Yoshihiro , Tsuge Sadaji , Sasaki Manabu , Ninomiya Kunimoto , Masato Nishikuni Masato Nishikuni , Shinya Tsuda Shinya Tsuda
Published: October 2002

The hydrogen plasma post-treatment of hydrogenated amorphous silicon (a-Si:H) has been investigated to obtain high-quality wide-gap films. The hydrogen plasma treatment after film deposition substantially increases the hydrogen content and the optical gap of a-Si films without deteriorating their optoelectric properties within the range of treatment conditions in this study, where no microcrystallization of the films is observed. A photoconductivity of ∼10-5 Ω-1 cm-1 and a photosensitivity (the ratio of photoconductivity to dark conductivity) of >106 are obtained for a-Si:H films with an optical gap of >1.7 eV from the (αhν)1/3 plot (>2.0 eV from Tauc's plot) under AM-1, 100 mW/cm2 illumination. An extremely high open circuit voltage of >1 V is obtained for an a-Si single-junction cell whose i-layer was fabricated using the hydrogen plasma treatment.
Enhanced Two-Dimensional Electron Gas Concentrations and Mobilities in Multiple δ-DopedGaAs/In0.25Ga0.75As/GaAs Pseudomorphic Heterostructures
Authors: Shieh Hir-Ming , Wu Chang-Luen , Hsu Wei-Chou , Yue-Huei Wu Yue-Huei Wu , Ming-Jer Kao Ming-Jer Kao
Published: October 2002

Selectively multiple δ- doped GaAs/In0.25Ga0.75As/GaAs pseudomorphic heterostructures grown by low-pressure metalorganic chemical vapor deposition (LP-MOCVD) for improving two-dimensional electron gas (2DEG) concentrations and mobilities were demonstrated. All the multiple δ- doped structures revealed significantly higher 2DEG concentration and mobility than those of single δ- doped and conventional homogeneously doped GaAs/InGaAs structures. The structure with double δ- doped GaAs layers grown symmetrically on both sides of the channel showed extremely high 2DEG concentrations of 6.2(4.1)×1012 cm-2 and mobilities of 4630(19100) cm2/ v· s at 300(77) K. Meanwhile, a peak extrinsic transconductance of 390 mS/mm, maximum effective saturation current density of 880 mA/mm, with broad and high transconductance region at 300 K, were achieved in this symmetrically δ- doped GaAs structure.
Low-Temperature-Processed Poly-Si Thin-Film Transistors Using Solid-Phase-Crystallized and Liquid-Phase-Deposited Gate Oxide
Authors: Yeh Ching-Fa , Chen Chun-Lin , Yang Yu-Chi , Lin Shyue-Shyh , Tzung-Zu Yang Tzung-Zu Yang , Tzy-Yan Hong Tzy-Yan Hong
Published: October 2002

Poly-Si thin-film transistor (TFT) devices using solid-phase-crystallized and liquid-phase-deposited gate oxide are, for the first time, realized by low-temperature processes (LTP) (<625° C) for future LCDs and 3-D integrated circuits. The method of liquid-phase deposition of SiO2 ( LPD-SiO2) is described. The physical, chemical and electrical properties of the new dielectric layer are clarified. The TFT (W/L=200 µ m/10 µ m) having an on-off current ratio of 106 at V
D=5 V, a field-effect mobility of 15 cm2/ V· s at V
D=0.1 V, a threshold voltage of 5.6 V, and a subthreshold swing of 1.6 V/decade, exhibits sufficient performance for pixel transistors. The field-effect mobility is strongly dependent on channel length. Effective passivation of defects by plasma hydrogenation will be very essential to achieve higher performance.
Simultaneous Stress-Induced Al Extrusion and Void Formation Caused by High Temperature Annealing after Via-Hole Opening in Al Interconnects with Via-Holes
Authors: Shibata Hideki , Tadashi Matsuno Tadashi Matsuno , Kazuhiko Hashimoto Kazuhiko Hashimoto
Published: October 2002

A new reliability issue caused by high temperature annealing after via hole opening has been investigated and characterized. For the first time, it was found that a high temperature anneal above 450° C causes simultaneous Al extrusion at the via hole interface and void formation in Al interconnects, drastically degrading the reliability of Al lines with vias. Based on in situ observation of extrusion/void formation and two-dimensional elastic deformation analysis, it was confirmed that this phenomenon is due to the movement of Al atoms towards the via hole interface resulting from the thermal expansion and the stress gradient formed in the Al line near the via hole during the anneal sequence. Specific experimental results and the influence of such an anneal process on the reliability of Al lines will be discussed in detail.
Decay Behavior of Light-Induced ESR in Hydrogenated Amorphous Silicon-Nitrogen Alloys
Authors: Zhang Jinyan , Minoru Kumeda Minoru Kumeda , Tatsuo Shimizu Tatsuo Shimizu
Published: October 2002

Light-induced ESR signals created by short-time illumination in Si-rich hydrogenated amorphous silicon-nitrogen films do not completely disappear after cessation of illumination. The remaining fraction of light-induced ESR spin density increases with increasing illumination time and illumination intensity, suggesting that a structural change proceeds with illumination.
Preparation of Alkaline-Metal-Doped C60 Superconducting Film and Its Stabilization in Air with Protective Coatings
Authors: Okuda Nobuyuki , Kugai Hirokazu , Uemura Takasi , Okura Kengo , Yoshinobu Ueba Yoshinobu Ueba , Koji Tada Koji Tada
Published: October 2002

Preparation conditions of C60 film were studied by varying substrates, substrate temperature and the rate of evaporation. Crystalline C60 thin films were prepared on GaAs(100) at the substrate temperature of 100° C in order to obtain superconductors by alkaline metal doping. The Rb/Cs-doped film showed a superconducting transition with T
c( onset)=24±3 K and T
c( zero)=8 K. The composition of the superconducting film was measured by micro-Auger electron spectroscopy. Air stability of Rb3C60 superconducting film with protective coatings applied was studied. A Si protective film maintained superconductivity for 220 min in air. In addition a Si/Al protective coatings maintained superconductivity for 8 h.
Effectiveness of High-Pressure Synthesis of Bulk High-Temperature Superconductors of Hg–Ba–Ca–Cu–O System
Authors: Nakajima Satoru , Kikuchi Mami , Atou Toshiyuki , Masae Kikuchi Masae Kikuchi , Yasuhiko Syono Yasuhiko Syono
Published: October 2002

Bulk superconductors of nominal compositions of tetragonal HgBa2Ca

n
-1Cu

n

O

y

(n=1–3) have been synthesized by a sealed quartz tube technique and high-pressure technique. In the present study nearly single-phase HgBa2CuO

y

was rather easily obtained by the former technique, but HgBa2CaCu2O

y

and HgBa2Ca2Cu3O

y

phases were formed by high-pressure technique which presumably prevents decomposition of HgO.
Relaxation Mechanism of Free Radicals in Silica Glass Studied by Pulsed-ESR Spectroscopy
Authors: Mizuta Yukio , Masahiro Kohno Masahiro Kohno , Kanae Fujii Kanae Fujii
Published: October 2002

The defects in γ- irradiated silica glass were investigated using the pulsed ESR technique. By exciting the spin packets both selectively and nonselectively, it was found that spin relaxation was induced mainly by the dipole-dipole interaction between electron spins of the identical species. By analyzing the dipole-dipole interaction between electron spins, the flip-flop phenomenon between them was found to be the main cause of electron spin relaxation.
Dependence of Coercivity on Co Layer Thickness in (111)Pd/Co Superlattices Grown by Molecular-Beam Epitaxy
Authors: Toshiki Kingetsu Toshiki Kingetsu
Published: October 2002

The magnetic and structural properties of (111)Pd/Co superlattices were studied. The samples were grown on reconstructed 7×7-(111) Si substrates with Ag seed layers by molecular-beam epitaxy. The dependence of the coercivity (H
c) of the Pd/Co superlattices on the Co layer thickness (t) is presented in detail. The H
c does not exhibit a t
-5/2 dependence that was previously reported in an epitaxial Pd/Co/Pd wedge-shaped sandwich structure.
Thermal Effect in a Lamp-Pumped Continuous-Wave Alexandrite Laser
Authors: Torizuka Kenji , Yabiku Mikio Yamashita
Published: October 2002

Output-power saturation of a lamp-pumped continuous-wave alexandrite laser was observed. From the measurement of transient responses of the laser, it is found that the power saturation is due to a thermal effect. A model of the laser is introduced, which takes into account rod heating by laser reabsorption. Model analysis explains the saturated laser power and laser wavelengths that were measured under different rod-cooling conditions, output transmissions and pumping power.
Optical Study of Photon-Trapped Porous Silicon Layer
Authors: Chen Liang-Yao , Hou Xiao-Yuan , Huang Da-Ming , Hao Ping-Hai , Zhang Fu-Long , Feng Xing-Wei , You-Hua Qian You-Hua Qian , Xun Wang Xun Wang
Published: October 2002

Porous-Si samples were optically studied by using the photoluminescence, Raman scattering, the absolute reflectance and ellipsometry methods. Results show that the porous Si has low optical constants, and can trap more than 95% of the visible photons, but give no evidence of a strong interband transition existing in the visible region, especially at the 1.8-eV PL peak position, as suggested by the quantum size effect. The Lorentz oscillator and Bruggeman effective medium approximation (EMA) models were used in data analyses. Calculations indicate that if strong interband transition occurs, an optical structure can be recognized in the spectra, but it was not seen in the experiments. Therefore, a contradiction exists in the PL and optical absorption experiments. Except for other mechanisms, the calculations show that the layer dispersion effect may result in a shift of the luminescence peak for the porous Si. The 1.8-eV PL peak, not always shifted significantly but often seen with consistency in other material structures, strongly indicates the same origin of visible luminescence as those suggested in the literature. A possible mechanism for the luminescence and Raman enhancement as well as the photon trap phenomenon was discussed, and was attributed mainly to random multiple micro-reflections occurring in the porous-Si layer that has extremely large internal micro surfaces.
Electron Paramagnetic Resonance Studies of Defects in CdIn2S4 Single Crystals
Authors: Takeo Takizawa Takeo Takizawa , Eric Christoffel Eric Christoffel , Alfred Goltzené Alfred Goltzené , Claude Schwab Claude Schwab
Published: October 2002

Defect centers in CdIn2S4 single crystals have been investigated using 9 GHz electron paramagnetic resonance (EPR). Experiments have been performed over the 4.2 to 100 K temperature range on both as-grown and electron-irradiated samples in the dark and under illumination with band-gap energy light ( λ= 530 nm). Before illumination, most as-grown samples show only weak signals. During illumination, two symmetric, isotropic lines are observed: S1 at g = 2.019±0.003 and S2 at g = 1.660±0.003 each with a linewidth (ΔH) of about 300 G. From the similar thermal decay and photoquenching characteristics, S1 and S2 are considered to arise from an acceptor and a shallow donor, respectively. Electron irradiation (1.8 MeV) induces two new lines in the dark. At low doses S3 with g = 1.766±0.001 and ΔH = 75 G is observed, while SF2 with g = 1.665±0.001 and ΔH = 15 is observed at high doses. The broad S2 disappears and the narrow SF2 appears with increasing electron doses. SF2 is then associated with Fermi-level modification by irradiation-induced donors.
Mechanism of Diffuse Phase Transition in Relaxor Ferroelectrics
Authors: Tsurumi Takaaki , Soejima Kouji , Toshio Kamiya Toshio Kamiya , Masaki Daimon Masaki Daimon
Published: October 2002

Dielectric properties of lead magnesium niobate (PMN) and Ta-bearing strontium barium niobate (SBNT) were measured as a function of temperature, and the crystal structure of PMN was refined by the Rietveld analysis method. The results of structure refinement indicate that the volume of polar microregions (PMR) increases with decreasing temperature. The dielectric properties of PMN and SBNT are well explained by an advanced theory of dielectric dispersion. The anomalous behavior in dielectric permittivity (ε) observed on the low temperature side of T
m, the temperature of ε maximum, is explained by simple dielectric relaxation, while on the high-temperature side of T
m is explained by the volume increase of PMR. It is concluded that these is no phase transition around T
m, and the diffuse phase transition is an overlapping phenomenon of volume increase of PMR, freezing process of fluctuating dipoles in PMR and dielectric dispersion around the measuring frequrncy. A model of diffuse phase transition and relaxor ferroelectrics is proposed. The difference between normal ferroelectrics and relaxor ferroelectrics is discussed from the viewpoints of spreading of soft-mode phonons and disorder in the crystals.
Measurement of Thin Oxide Films on Implanted Si-Substrate by Ellipsometry
Authors: Chao Tien Sheng , Lei Tan Fu , Lee Chun Yun Chang
Published: October 2002

In this study, the thickness of oxide film which is deposited by low-temperature chemical vapor deposition (LTCVD) on an implanted silicon substrate was measured by multiple-angle incident (MAI) ellipsometry. By using this method, the refractive index, thickness, and the effective index of the substrate can be calculated simultaneously. It is found that the thickness of oxide film on an implanted silicon substrate is only 4% different from that on a nonimplanted silicon substrate under the same deposition conditions. The result shows that a higher implantation energy results in a higher effective substrate index. Even with a high temperature and long annealing process, the refractive index of the implanted silicon substrate cannot recover to the value of nonimplanted silicon substrate.
Breakdown Characteristics of SF6Gap Disturbed by a Metallic Protrusion under Oscillating Transient Overvoltages
Authors: Kawamura Tatsuo , Lee Bok-Hee , Nishimura Takahiko , Ishii Masaru
Published: October 2002

This paper deals with the experimental investigations of particle-initiated breakdown of SF6gas stressed by the oscillating transient overvoltage and non-oscillating impulse voltages. The experiments are carried out by using hemisphere-to-plane electrodes with a needle-shaped protrusion in the gas pressure range of 0.05 to 0.3 MPa. The temporal growth of the prebreakdown process is measured by a current shunt and a photomultiplier. The electrical breakdown is initiated by the streamer corona in the vicinity of a needle-shaped protrusion and the flashover of test gap is substantially influenced by the local field enhancement due to the space charge formed by the preceding streamer corona. The dependence of the voltage-time characteristics on the polarity of test voltage is appreciable, and the minimum breakdown voltage under the damped oscillating transient overvoltage is approximately the same as that under the standard lightning impulse voltage. In presence of positive polarity, the dielectric strength of SF6gas stressed by the oscillating transient overvoltage is particularly sensitive to the local field perturbed by a sharp conducting particle. The formative time lag from the first streamer corona to breakdown is longer in negative polarity than in positive polarity and the field stabilization of space charge is more pronounced in negative polarity.
Separate Measurement of Two Components of Blood Flow Velocity in Tissues by Dynamic Light Scattering Method
Authors: Kashima Susumu , Ono Yoshiko , Akihiko Sohda Akihiko Sohda , Toshihiko Ohsawa Toshihiko Ohsawa
Published: October 2002

Blood flow velocity depends on the size and type of blood vessel. If the distribution of the blood flow velocity in a tissue can be measured, the vascular structure may be estimated. The dynamic light scattering method allows us to measure the flow velocity and the number density of moving erythrocytes by analyzing the power spectrum of the light scattered from a tissue. To estimate the vascular structure, the regression analysis method was applied to separate the power spectrum resulting from different flow velocities. The theoretical model was verified by experimental results using a tissue blood flow model system. The results show that two velocities may be measured separately if there is a large difference between them. The cutaneous blood flow of a finger and a forearm was analyzed and compared using the proposed method.
Evaluation of Plasma-Induced Damage by Medium-Energy Ion Scattering
Authors: Yokoyama Shin , Radzimski Zbigniew J. , Ishibashi Kensaku , Miyazaki Seiichi , Hirose Masataka
Published: October 2002

The plasma-induced Si surface damage in CF4+H2 and Ar plasmas which are used for the SiO2 contact hole etching and Si surface cleaning, respectively, have been studied by using the medium-energy ion scattering (MEIS) measurement. It was found that the Si damage induced by the CF4+H2 plasma treatment is relatively small compared with the Ar-ion-induced damage because of the formation of CF2 monomers on the Si surface. For the Ar plasma cleaning, the damage is increased with the self-bias. The small damage induced by Ar plasma at self-biases less than -80 V was detected by the MEIS. The MEIS results have been compared with electrical characteristics of Al/n-Si Schottky diodes for which the Si surface was Ar plasma cleaned. The leakage current and the barrier height of the Al/n-Si Schottky diodes exhibit good correlations with the MEIS data.
Translational-Energy-Induced Anisotropic Etching of Poly-Si by Cl2 Supersonic Molecular Beams
Authors: Yuden Teraoka Yuden Teraoka , Iwao Nishiyama Iwao Nishiyama
Published: October 2002

A high-translational-energy Cl2 neutral beam created in a Cl2-seeded He supersonic molecular beam has been applied to poly-Si etching. Translational-energy-induced etching was observed at a substrate temperature of 530° C with a translational energy threshold of 0.7 eV. From the temperature dependence of the etch rates, the etching reaction was found to be composed of two thermal desorption processes with activation energies of 2.8 eV and 0.9 eV, corresponding to gas etching and translational-energy-induced etching, respectively. Anisotropic etching profiles were achieved with complete selectivity against SiO2 due to the fact that the etching was induced by translational energy.
Interfacial Defects Related to the Substrate Treatment in Molecular Beam Epitaxial Silicon
Authors: Sheng Chi , Gong Dawei , Wei Xin , Lu Fang , Wang Qinhua , Henghui Sun Henghui Sun , Xun Wang Xun Wang
Published: October 2002

Interfacial defects related to the residual carbon on the hydrogenterminated Si(100) surface have been studied using the deep-level transient spectroscopy (DLTS) technique. The defect level is found to be donorlike which compensates the acceptor impurity at the interface. With a fast load-in and a two-step annealing, the defect density can be suppressed below the DLTS detection limit of 1012 cm-3.
Modelling and Application of Synchronization of Nucleation by Means of Intermittent Radiant Heating
Authors: Mats I. Larsson Mats I. Larsson , Göran V. Hansson Göran V. Hansson
Published: October 2002

The method of synchronization of nucleation (SN) by means of periodically altering the substrate temperature has been studied theoretically by using a simple Monte Carlo simulation model and by applying a realistic temperature function. SN has also been studied experimentally using reflection high energy electron diffraction (RHEED) intensity oscillations. Results for SN applied to growth of Si and Si1-
x

Ge

x

on Si(111) are presented. Our growth simulations of Si on Si(111) support the experimental results that an improved layer-by-layer growth below the step flow regime can be obtained using SN.
Parametric Investigation of Si1-xGex/Si Multiple Quantum Well Growth
Authors: Thompson Phillip E. , Godbey David , Hobart Karl , Glaser Evan , Kennedy Thomas , Simons Mark Twigg
Published: October 2002

Si0.8Ge0.2/Si multiple quantum wells (3 nm/30 nm) have been grown by molecular beam epitaxy and have been characterized using photoluminescence (PL), secondary ion mass spectrometry, and transmission electron microscopy. A parametric investigation relating the growth conditions to the PL was carried out. The existence of phonon-resolved band-edge PL appears to be strongly related to the background impurity concentration. The connection between phonon-resolved band-edge PL and higher substrate growth temperatures is probably due to the temperature-dependent incorporation of impurities. In the as-grown samples a correlation of the broad PL with platelet density in the quantum wells was observed. The broad PL may be associated with Cr at the platelets since a high temperature ( 710° C) anneal extinguished the broad PL and caused a reduction in the Cr found in the quantum wells, but had no effect on the platelet density.
High Resolution X-Ray Triple Axis Diffractometry of Short Period SimGen Superlattices
Authors: Koppensteiner Ewald , Bauer Günther , Holy Vaclav , Kasper Erich
Published: October 2002

Double crystal and triple axis X-ray reciprocal space mapping were used to characterize in detail the structural properties of short period Si9Ge6 superlattices grown by molecular beam epitaxy (MBE) on 1.3 µ m thick step-graded SiGe alloy buffers resulting in reduced dislocation densities. Precise strain data were extracted from two-dimensional reciprocal space maps around (004) and (224) reciprocal lattice points (RELP's). From the distribution of diffusely scattered intensity around reciprocal lattice points the correlation function of the deformation field due to structural defects was calculated using a model based on the kinematical theory of X-ray diffraction and on a formalism from statistical optics. Two types of extreme models were defined for the defect structure, and from simulations to the correlation function calculated from the diffuse X-ray scattering (DXS) limiting mosaicity parameters were extracted.
Electron Transitions in Si1-xGex/Ge Multiple Quantum Wells Grown on Si(001) Substrates
Authors: Lee Chanho , Sang K. Chun Sang K. Chun , Kang L. Wang Kang L. Wang
Published: October 2002

The intersubband absorption by an optical field corresponding to normally incident light has been observed in the conduction band of Si1-
x

Ge

x

/Ge quantum wells grown on Si(001) substrates using a Si molecular beam epitaxy (MBE) system. Normal incidence electron transitions are allowed due to the coupling of the optical field parallel to quantum well planes and the nonzero off-diagonal terms of the inverse effective mass tensor which are caused by the energy ellipsoids tilted toward the [001] growth direction. The quantum wells were formed by the conduction band offset of SiGe heterostructure and Sb δ-doping. An absorption coefficient of 17000 cm-1 has been obtained as measured with a Fourier-transform infrared (FTIR) spectrometer. Absorption peaks in the range of 5∼10 µ m have been obtained for a variety of samples studied. The detection range can be easily controlled by changing either the doping concentration or the band offset, or both. The results offer the opportunity for the application of focal plane arrays with Si integrated circuits built on Si(001) substrates.
Thermal Stability Characterization of Doped Layers and Heterostructures Grown by Si-Molecular Beam Epitaxy
Authors: Sardela Jr. Mauro R. , Radamson Homayon H. , Ni Wei-Xin , Jan-Eric Sundgren Jan-Eric Sundgren , Göran V. Hansson Göran V. Hansson
Published: October 2002

The thermal stability of layers grown by Si-molecular beam epitaxy is reported in a comparative study of strain induced in Si by heavy B doping and by Si1-
x

Ge

x

alloying. High-resolution X-ray diffraction mapping was employed as the major analytical tool. The strain relaxation under high-temperature annealing is shown to be dominated by the formation of precipitates and by diffusion in the case of heavy doping but with a negligible amount of dislocations. In the Si1-
x

Ge

x

/Si heterostructures, the process is dominated by strain relaxation via formation of misfit dislocations.
Thermally Induced Precipitation of Silicon Carbide in a Semiconductor Matrix-Application to Nanoparticle Fabrication
Authors: Powell Adrian R. , LeGoues Francoise K. , Iyer Subramanian S. , Bruce Ek Bruce Ek
Published: October 2002

In this work the Si1-
y

C

y

random alloy is used as a starting point for the creation of nano particles of β-SiC with the same lattice orientation as the Si lattice in which they are grown. These nano particles are between 3 and 8 nm in diameter and are randomly dispersed throughout the Si1-
y

C

y

region, where 0.005<y<0.05. This ability to produce quantum antidots of wide bandgap material within the Si matrix should enable the exploration of mesoscopic phenomena.
High-Mobility p-Channel Metal-Oxide-Semiconductor Field-Effect-Transistor on Strained Si
Authors: Nayak Deepak K. , Woo Jason C. S. , Park Jin S. , MacWilliams Kang L. Wang
Published: October 2002

An enhancement-mode high-mobility p-channel metal-oxide-semiconductor field-effect-transistor (MOSFET) is fabricated on strained Si layer for the first time. A biaxially strained thin Si layer is pseudomorphically grown on a relaxed GeSi buffer on Si substrate by molecular beam epitaxy (MBE). MOSFETs are fabricated using conventional Si process technology. It is found that low-field channel mobility of PMOSFET on strained Si is 50% higher than that of PMOSFET on bulk Si.
In-Situ Control of Strained Heterostructure Growth
Authors: Yasuyuki Kobayashi Yasuyuki Kobayashi , Naoki Kobayashi Naoki Kobayashi
Published: October 2002

This paper reports the metalorganic vapor phase epitaxial growth of pseudomorphic InAs/InP single quantum wells (SQWs) on (001) InP substrates using in-situ surface photo-absorption (SPA) monitoring, and reports on the optical characterization of them. By adjusting the arsine flow rate, arsine exposure time and substrate temperature on the basis of in-situ SPA monitoring, we are able to grow pseudomorphic InAs/InP SQWs comprising up to 10-monolayer InAs wells having metallurgically abrupt and atomically flat strained heterointerfaces. Photoluminescence excitation measurement for an 8-monolayer InAs well shows energy splitting as large as 0.4 eV between heavy and light holes subbands, indicating the InAs well layer is coherently strained to a maximum extent within the critical layer thickness.
Optical Constants of 6H–SiC Single Crystals
Authors: Susumu Ninomiya Susumu Ninomiya , Sadao Adachi Sadao Adachi
Published: October 2002

The complex dielectric functions of 6H–SiC for light polarized perpendicular and parallel to the optic axis c were measured using spectroscopic ellipsometry. The measurements were made on the (0001) and (011̄0) surfaces of 6H–SiC in the photon energy range between 1.2 and 5.4 eV at room temperature. The measured dielectric-function spectra were fitted with a classical Lorentz-type oscillator model. The indices of refraction in the transparent region (E < 4.5 eV) were also analyzed using the first-order Sellmeier equation. From this analysis, we obtained the high-frequency dielectric constants ε
∞ of 6H–SiC as 6.59 for E ⊥c and 6.67 for E //c. Using the Lyddane-Sachs-Teller relation, we also obtained the static dielectric constants ε
s as 9.76 for E ⊥c and 9.98 for E //c.
Analysis of Phase Breaking Effect in Resonant Tunneling Diodes Using Correlation Function
Authors: Kazuhito Furuya Kazuhito Furuya , Nobuya Machida Nobuya Machida , Young-Cheul Kang Young-Cheul Kang
Published: October 2002

Resonant characteristics in double-barrier tunneling structures are analyzed taking the effects of phase breaking into consideration. The correlation function is used to express the degree of phase coherence during the multiple reflection, in the Fabry-Perot resonator. This treatment promises preservation of the probability current and describes broadening of the resonant peak due to phase breaking.
New Polysilicon-Oxide-Nitride-Oxide-Silicon Electrically Erasable Programmable Read-only Memory Device Approach for Eliminating Off-Cell Leakage Current
Authors: Lin Jyh-Kuang , Chang Chun-Yen , Huang Heng-Sheng , Chen Kun-Luh , Kuo Dah-Chih
Published: October 2002

A new polysilicon-oxide-nitride-oxide-silicon (SONOS) electrically erasable programmable read-only memory (EEPROM) device, which eliminated off-cell leakage current, has been described and fabricated. The leakage current is easily encountered in metal-nitride-oxide-silicon (MNOS)-type EEPROMs. Two parasitic transistors, which are in parallel with the desired variable V
t cell, are responsible for the leakage current. We demonstrated that the parasitic transistors are caused either by the nearly constant-threshold-voltage parasitic transistors surrounding the active region or by the “fringing effect” in poly-Si gate edges. The on-state and off-state I-V curves of the cell are shown and compared with those of two other different devices. The results reveal that the off-cell leakage current, which is observed in the other two devices, is completely eliminated in the proposed cell.
Experimental Corroboration for a Ferrite-Core Model of High-Tc Bulk Superconductor Lenses (Supertrons)
Authors: Matsuzawa Hidenori , Kobayashi Hiroaki , Mochizuki Hiroaki , Yoneyama Naoyuki , Ohshima Akihito , Hirano Susumu , Mori Eiji , Horigome Gakuji , Yutaka Ishida Yutaka Ishida , Yukio Chino Yukio Chino
Published: October 2002

High-T
c bulk superconductor lenses (Supertrons) for electron beams were operated over a temperature range from 65 to 130 K. The experimental results support a ferrite-core model of the lenses: Lenses for single short electron pulses are composed of fine grains of superconductors, as are ferrite cores. The lenses examined were Y-based 945°C and 750°C-sintered powder-pressed ones, an Y-based melt-processed one, a Bi-based 850°C-sintered powder-pressed one, and copper-block-made and copper-powder-pressed ones. Both the Bi-based and the Y-based 750°C-sintered lenses realized thinner electron beams ( ∼340 keV, ∼10 ns, ∼1.4 kA) with decreasing operation temperatures, especially below their T
c's. The copper-powder pressed lens also worked better with falling temperatures, but was inferior to the Bi-based lens. These behaviors are understandable in view of the similarity in operation between ferrite cores and Supertrons.
Direct Measurement of Subnetwork Exchange Coupling Constant for Ferrimagnets
Authors: Fu Hong , Te-ho Wu Te-ho Wu , M. Mansuripur M. Mansuripur
Published: October 2002

We show that the subnetwork exchange coupling constant λ of ferrimagnetic films is equal to the slope of the plot of the magnetic field H applied in the film plane versus the in-plane magnetization M
// at compensation temperature T
comp, i.e. H=λM
// at T
comp. This finding enables the direct measurement of λ for ferrimagnetic magneto-optical recording thin films, regardless of the complexity of the two-subnetwork problem. The experimental results are within the range predicted by the mean-field theory.