bluuebunny/crossref_metadata_2025 huggingface dataset:
Material Losses and Compositional Changes in Two-Step Processed CuInSe2 Thin Films
Authors: Alberts V. , Klenk M. , Bucher E.
Published: October 2002

Material losses and the resulting compositional changes in two-step processed chalcopyrite thin films are widely discussed topics in literature. In this study, metallic precursors were selenized in H2Se/Ar at a wide range of processing temperatures between 300°C and 600°C. The composition of the resulting films at different stages of processing were analyzed by electron probe microanalysis (EPMA) and X-ray fluorescence (XRF). Comparison of EPMA and XRF data from identical selenized samples revealed a discrepancy in composition at temperatures at or above a critical point around 400°C. In contrast to the loss of In indicated by EPMA measurements, XRF analysis revealed that the Cu and In Kα1,2 intensity values remained virtually constant, irrespective of the selenization conditions (i.e. no evidence of material losses). The use of more surface sensitive Lα1 line scans clearly revealed a segregation of In away and Cu towards the upper part of the layer with increasing selenization temperature. Based on these results the commonly reported compositional shift due to material losses is interpreted as a measurement artifact of the EPMA technique under typical measurement conditions for two-step processed chalcopyrite absorber films.
Focusing Properties of a Novel Dual-Gate Edge Emitter
Authors: Nicolaescu Dan , Filip Valeriu , Itoh Junji
Published: October 2002

Field emitters are used as distributed electron sources in applications such as field emission displays (FEDs). This study analyzes the deflection and focusing properties of a novel dual-gate edge emitter. The structure considered has the edge of a thin metal layer as emitter and a deflection and focusing electrode lying in the same plane. Linear and circular emitter configurations are comparatively analyzed, the simulation work being performed with the Simion 6.0 software package. The analysis concerns electron-beam pattern, dimensions and incidence angle on the anode plane.
Optimum Conditions for Novel One-Step Cleaning Method for Pre-Gate Oxide Cleaning Using Robust Design Methodology
Authors: Pan Tung Ming , Lei Tan Fu , Chao Tien Sheng , Liaw Ming Chi , Lu Chih Peng
Published: October 2002

A novel one-step cleaning method has been developed for pre-gate-oxide cleaning to replace the conventional RCA two-step cleaning process. Tetramethyl ammonium hydroxide (TMAH) and ethylenediamine tetraacetic acid (EDTA) are added into the RCA SC-1 cleaning solution to enhance cleaning efficiency. We adapt a robust design methodology (Genichi Taguchi method) to analyze the results of our experiments. Using this novel method, it is found that the optimum conditions are A1B2C1D1 (A1: TMAH:NH4OH=1:50, B2: EDTA concentration is 100 ppm, C1: cleaning time is 5 min, and D1: cleaning temperature is 60°C). This novel one-step cleaning method is very promising for future large-sized silicon wafer cleaning processes because it has the advantages of reduced processing time and temperature, cost reduction due to reduced chemical usage and improved performance.
Comparative Study of Hydrido Organo Siloxane Polymer and Hydrogen Silsesquioxane
Authors: Chung Sung-Woong , Kim Sun-Young , Shin Joo-Han , Kim Jun Ki , Park Jinwon
Published: October 2002

Low-k candidate spin-on-glass (SOG) material hydrido organo siloxane polymer (HOSP) was evaluated and compared with flowable oxide (FO
x
). In particular, the chemical nature of the film and the effects of various processing steps on this chemical nature were investigated using Fourier transform infrared spectroscopy (FTIR), thermal desorption spectroscopy (TDS), a C–V meter and a stress gauge. The water absorption after various post-etch treatments was found to be a crucial factor affecting the dielectric properties of the film. HOSP proved to be a dielectric material with a lower k value than FO
x
and is more immune against moisture uptake. However, HOSP becomes more vulnerable to moisture absorption after oxygen plasma treatment. Electrical data from the process integration of HOSP were compared to those of FO
x
and conventional plasma-deposited oxide. The via resistance using HOSP was higher than that using the other materials. In particular, HOSP samples exhibited strong dependence on misalignment in resistance or leakage current measurements. The scanning electron microscope (SEM) image of these samples show that the electrical properties of HOSP samples resulted from a decrease in the actual via metal cross-section area due to via-poisoning.
Does the Macrostructure of Deoxyribonucleic Acid Molecules Adsorbed on Substrates by the Pulse Injection Method Reflect That in Solution?
Authors: Kanno Takashi , Tanaka Hiroyuki , Nakamura Tomohiko , Tabata Hitoshi , Kawai Tomoji
Published: October 2002

In order to investigate whether the concentration-dependent macrostructure of
Deoxyribonucleic acid (DNA) molecules can be retained after pulse injection, as
compared to that originally present in the aqueous solution, we performed scanning
tunneling microscopy (STM) imaging of plasmid DNA pulse-injected from an aqueous
solution containing different DNA concentrations. The observed STM images revealed
the presence of a relaxed circular macrostructure at low concentrations
(1.2 µg/ml of DNA and 0.3 mM of Na+) whereas an entangled circular
macrostructure was observed at high concentration (60 µg/ml of DNA and 15 mM
of Na+). We conclude that plasmid DNA molecules retain the macrostructures
possessed in the aqueous solution even after pulse injection onto a solid surface under
vacuum environment.
Effect of Heat Treatment on Critical Current Density–Magnetic Field Curve for YBa2Cu3O7-δ Single Crystal and Its Microstructure
Authors: Oka Akihiro , Koyama Satoshi , Izumi Teruo , Shiohara Yuh , Shibata Junko , Hirayama Tsukasa
Published: October 2002

The dependences of critical current density–magnetic field (J
c–H) curves for YBa2Cu3O7-δ (Y123) single crystals on heat treatment processes were studied. The single crystals were annealed by a two-step heat treatment process, during which the crystals were annealed at 873 K for 100 h, followed by annealing at 773 K for 200 h in a pure oxygen gas flow. Furthermore, the single crystals were annealed using three different untwinning processes with uniaxial stress such as a detwinnig process and a twin-free process. The J
c–H curves and their peak effects with the H∥c-axis displayed a large dependence on the heat treatment processes. Furthermore, the microstructures in these single crystals were observed using transmission electron microscopy (TEM). The anti-phase boundaries, which depended on the heat treatment processes, were observed in the crystals. These results suggested that the anti-phase boundaries are responsible for the peak effects, which is attributed to the distribution of the pinning centers of oxygen deficient phases in the crystals.
Measurement and Modeling of Xe Vacuum Ultraviolet Emission and Radiative Transfer in a Plasma Display Panel Discharge
Authors: Tamida Taichiro , Sanders Steven Jay , Tanaka Masaaki
Published: October 2002

A detailed study of radiative transfer of vacuum ultraviolet
emission in a plasma display panel is presented for the first
time. Extensive experimental data obtained from a front panel in a
test chamber are compared with a theoretical model. The model accounts
for radiation trapping and opacity broadening of resonance lines, as
well as the major collisional dynamics among ions, neutrals, and
electrons in a xenon/neon discharge. The model was also used to
predict the panel illumination efficiency, a parameter of prime
importance for display designers. The results from the model yielded
good agreement with experimental results over a wide range of
pressures and cell geometries.
Annealing Effect on Low-Resistance Ferromagnetic Tunnel Junctions
Authors: Ando Yasuo , Kubota Hitoshi , Hayashi Masamitsu , Kamijo Makoto , Yaoita Kazuya , Yu Andrew Chak Chung , Han Xiu-Feng , Miyazaki Terunobu
Published: October 2002

The stacking structure and fabrication process of tunnel junctions were investigated. The stacking structure of the tunnel junctions fabricated was Ta/(Cu,Pt)/Fe20Ni80/IrMn/Co75Fe25/Al-oxide/Co75Fe25/Fe20Ni80/Ta. When the Al thickness, oxidation time, and annealing temperature were 0.8 nm, 15 s (10 s), and 300°C (250°C), the tunnel magnetoresistance (TMR) ratio and the resistance obtained were 49% (31%) and 1.1 kΩµm2 (230 Ωµm2), respectively. In order to investigate the annealing temperature dependence of the TMR ratio, the local electrical properties were measured for a Ta/Fe20Ni80/Pt/Fe20Ni80/IrMn/Co75Fe25/Al-oxide multilayer. The current image became very homogeneous after annealing at around 300°C for 1 h. The increase of the TMR ratio of the junction after annealing can be well explained by taking into account both an increase of barrier height and a decrease of barrier height fluctuation. After further annealing at above 350°C, the barrier height decreased and leakage currents were detected.
Laser Emissions from Disodium Fluorescein-Doped Poly(Vinyl Alcohol) Films
Authors: Yap Seong-Shan , Tou Teck-Yong , Ng Seik-Weng
Published: October 2002

Superradiant-mode laser emissions were obtained from disodium fluorescein (DF)-doped poly(vinyl alcohol) (PVA) films which had been dip-coated on a microscope glass slide. When the film was transversely pumped using a nitrogen laser, superradiant emission was trapped and propagated in the supporting glass slide which acted as a waveguide. The trapped light underwent multiple internal reflections before it exited at both ends of the slide, producing a lasing effect. The laser beam profile varied with the edge condition of the glass slide; a circular beam was obtained with a frosted edge. An output conversion efficiency of 22% was obtained for a fresh sample while its lasing output energy at a localized excitation position, or operating lifetime, decreased at a rate of 0.015% per shot of nitrogen laser. Despite the decrease in output energy, the laser peak wavelength of DF was largely unchanged.
Spatial Spectrum Chirp Characteristic of a Martinez-Type Multipass Pulse Stretcher
Authors: Ohmae Goichi , Yagi Takashi , Nanri Kenzo , Fujioka Tomoo
Published: October 2002

We demonstrated the capability of a Martinez-type multipass pulse stretcher to produce the pulse duration of about 1 ns stretched from 100 fs with well-preserved quality of the beam pattern and spatial spectral uniformity in the multipass configuration. The beam pattern after being stretched through the pulse stretcher depends significantly on the incident angle to the stretcher grating and the accuracy of adjustment of the optical elements. The observed spatial distribution of the wavelength in the beam cross section after being stretched is in good agreement with the simulation results.
Heat-Resistant Liquid Crystal Light Modulator Containing Polymer Network for High-Power Luminaires
Authors: Fujikake Hideo , Tanaka Yoshiaki , Kimura Saburo , Asakawa Hisashi , Tamura Takemi , Kita Hiroshi , Takeuchi Kiyofumi , Ogawa Hiroshi , Nagashima Akio , Utsumi Yozo , Takizawa Kuniharu
Published: October 2002

This paper describes a heat-resistant liquid crystal light modulator, which contains a 20-µm-thick polymer-dispersed liquid crystal film comprising tolane nematic liquid crystal with a high nematic-isotropic phase-transition temperature of 160°C and a three-dimensional fine polymer network of polyacrylate formed by means of photopolymerization-induced phase separation. The light modulator with an electrically controlled light scattering function can operate in the wide temperature range from room temperature to 120°C with excellent thermal stability. A new light-controllable spot luminaire system using the light modulator and a 575 W high-intensity metal halide lamp is also demonstrated with a high extinction ratio of more than 100 for illumination of television studios and stages.
Optical Transmission, Photoluminescence, and Raman Scattering of Porous SiC Prepared from p-Type 6H SiC
Authors: E. Spanier Sangsig Kim , P. Herman Irving
Published: October 2002

The optical transmission, temperature-dependence of the photoluminescence (PL), and Raman scattering of porous SiC prepared from p-type 6H-SiC are compared with those from bulk p-type 6H-SiC. While the transmission spectrum of bulk SiC at room temperature reveals a relatively sharp edge corresponding to its band gap at 3.03 eV, the transmission edge of porous SiC (PSC) is too wide to determine its band gap. It is believed that this wide edge might be due to surface states in PSC. At room temperature, the PL from PSC is 20 times stronger than that from bulk SiC. The PL PSC spectrum is essentially independent of temperature. The relative intensities of the Raman scattering peaks from PSC are largely independent of the polarization configuration, in contrast to those from bulk SiC, which suggests that the local order is fairly random.
Laser Short Pulse Heating and Elastic-Plastic Wave Generation
Authors: Yilbas Bekir S. , Arif A. F. M.
Published: October 2002

Laser induced shock processing improves the mechanical and tribological properties of metallic surfaces. During the high power intensity laser beam interaction with the solid substrate ablation of the surface occurs, which in turn results in a recoil pressure developing in the interaction zone. This triggers the generation of elastic-plastic waves that propagate in the solid substrate and as a consequence a plastic region is developed in the vicinity of the substrate surface. In the present study, short pulse laser heating of steel is considered, and the Fourier and the electron kinetic theory models pertinent to laser heating are introduced. The governing equations of heating are solved numerically with the appropriate boundary conditions considered. The recession and vapor front velocities, and vapor pressure and recoil pressures are determined for different laser power intensities. The elastic-plastic wave propagation in the solid substrate is modelled and findings are compared with the results of the previous studies. It is found that the rapid rise of the surface temperature occurs at high laser power intensities and the recoil pressure generated at the interface substantiates, which in turn results in elastic-plastic wave propagation in the solid substrate. This develops a plastic region in the order of 0.9 µm in the surface vicinity of the solid substrate and the time required for this deformation is in the order of 25 ns. In addition, the depth of the plastic region developed in the present study agrees well with the previous results.
Removing Spherical Silica Particles from Si, Ge and NiP Substrates by KrF Excimer Laser
Authors: Zheng Yuan-Wei , Lu Yong-Feng , Mai Zhi-Hong , Song Wen-Dong
Published: October 2002

Particle adhesion and removal are of great interest in IC process and high-density hard disk manufacturing. Increasing effort is required to remove submicron particles. We investigated the adhesion and removal of spherical silica particles from silicon (Si), germanium (Ge) and NiP substrates using a KrF excimer laser. Atomic force microscope (AFM) point-contact mode measurement showed that the tip adhesion force on Ge surface is greater than that on Si or NiP surface, and the Hamaker constant of NiP is about 2/3 of that of Ge substrate. The cleaning efficiency and cleaning thresholds for standard-size particles with a diameter of 1.0 µm were measured. The cleaning efficiency was sensitive to laser fluence. The threshold laser fluences for Si, Ge and NiP are 100, 30 and 8 mJ/cm2, respectively. The different cleaning curves are not only due to the difference in adhesion on the substrates, but also due to the different optical and thermal properties of the substrates.
Direct Measurement and Mechanism of Electro-Chemomechanical Expansion and Contraction in Polypyrrole Films
Authors: Keiichi Kaneto Keiichi Kaneto , Yasuaki Sonoda Yasuaki Sonoda , Wataru Takashima Wataru Takashima
Published: October 2002

Electro-chemomechanical expansion and contraction in polypyrrole films synthesized electrochemically from pyrrole in electrolytes of p-phenolsulfonic (PPS) acid has been measured directly in various supporting electrolytes. It is found that the films maintain a high electro-chemomechanical activity and conductivity in the wide pH range from pH4 to pH10 and also at the reduced and oxidized states studied under the present conditions. The electro-chemomechanical expansion of polypyrrole films is primarily driven by the insertion of bulky ions, regardless of oxidation and reduction. This is different from the mechanism of polyaniline films, in which a conformation change of the polymer structure is involved. The mechanism of electro-chemomechanical deformation in polypyrrole film is discussed, taking the conductivity and conformation of polypyrrole into consideration.
Supercooled Water and Ice Included in Multilamellar L-α, Distearoyl Phosphatidylcholine in Low-Temperature Regions below 0°C
Authors: Utoh Shigenori , Okubo Nobuaki
Published: October 2002

Bilayer, supercooled water and ice states in multilamellar phospholipids are investigated in the low-temperature region from 0°C to -100°C using L-α, distearoyl phosphatidylcholine (DSPC) having water contents of 44 wt% and 15 wt%, by differential scanning calorimeter and X-ray diffraction methods. Multilamellar DSPC contains 44 wt% water in not only the water layer, but also as excess water in the form of stock regions; on the other hand, multilamellar DSPC containing 15 wt% water has no excess water. The difference in water content between these multilamellar DSPCs causes characteristic changes of the H2O molecules and of the phospholipid bilayer in low-temperature regions below 0°C, e.g., ice crystallization inside or outside the multilamellae, changes in the chain packing conformation and changes in the long-range distance. It is confirmed that the supercooled water in the water layer inside multilamellar DSPC containing 15 wt% water continues to exist down to about -45°C during the cooling process and then is frozen into heterogeneous ice or ice nuclei below about -45°C. In the case of multilamellar DSPC with 44 wt% water, although changes of excess water from supercooled water to homogeneous ice with hexagonal symmetry are observed at about -20°C, the water layer inside the multilamellae remains supercooled down to about -45°C. Dehydration of polar head groups due to the appearance of ice in the water layer at around -45°C promotes some movement of polar head groups, thereby inducing changes in the chain packing conformation.
Temperature Dependence of Low Frequency Dielectric Constants in Surface-Stabilized Ferroelectric Liquid Crystal
Authors: Jong-Min Wang Jong-Min Wang , Jong-Jean Kim Jong-Jean Kim
Published: October 2002

We have studied the temperature dependence of two low-frequency dielectric relaxation modes in a surface-stabilized ferroelectric liquid crystal (SSFLC): space charge accumulation and X modes. From investigation of Cole–Cole plots the temperature dependence of dielectric strength Δε and relaxation frequency ωr for the two low-frequency modes was obtained. The relaxation frequency follows the Arrhenius relation in the respective asymptotic regions far from the phase transition temperatures. From the Arrhenius plots the activation energies for the space charge accumulation mode and the X-mode were obtained as 0.42 eV and 0.13 eV, respectively. Temperature dependence of rotational viscosity in the smectic C* (SmC*) phase conformed with the temperature dependence of the X-mode parameters in the effective Debye relaxation regime, which implicates a common origin of azimuthal molecular rotation for both the Goldstone mode and the X-mode. However, the X-mode is irrelevant to the symmetry breaking phase transition and continues to be observed at all temperatures far from the phase transition.
Evaluation of the Disadvantage of Radio Frequency Plasma Treatment on Polymer using Equivalent Circuit Model of Capacitor
Authors: Lee Moon-Keun , Lee Gon-Jae , Choi Duck-Kyun
Published: October 2002

The surface modification by plasma treatment is recently preferred to improve adhesion of metal on polymer. However, it may degrade the electrical or dielectric properties. To verify the drawbacks of surface modification, we compared biphenyldianhydride phenylenediamine (BPDA-PDA) polyimide after radio frequency (RF) Ar plasma treatments with as-baked polyimide. The confirmation of degrading the electrical properties of which surface is modified was attempted by means of equivalent circuit model of capacitor. Judging from that theory, we hypothesized that the electrical degradation can be easily checked out only by measuring resonance frequency. Capacitor before RF Ar plasma treatments showed the resonance frequency of 40.5 MHz (estimated). RF Ar plasma treatments for improving adhesion of metal on polyimide, however, lowered resonance frequency of polyimide to 34–35 MHz. From X-ray photoelectron spectroscopy (XPS) analysis, we certified that the degradation of electrical properties is derived out from the accumulated carbon atoms on the destroyed surface of polyimide layer. We deduced that although plasma treatments definitely did not affect the bulk dielectric constant of polyimide, it degraded the electrical properties of polyimide by lowering resonance frequency. Consequently, just measuring resonance frequency of capacitor can estimate the degradation of the electrical properties.
Effect of CaCN2 Addition on the Densification Behavior and Electric Properties of AlN Ceramics
Authors: Wang Moo-Chin , Hong Chieh-Kao , Tsai Ming-Sung , Wu Nan-Chung
Published: October 2002

Calcium cyanamide (CaCN2) has been used as a sintering aid as well as a dopant for AlN. The effect of CaCN2 addition on the densification behavior and electric properties of liquid-phase sintered AlN ceramics was investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM) and scanning electron microscopy (SEM), dielectric and electric resistance measurements. Dense sintered specimens (relative density > 97.0%) were obtained using 1.0 to 2.0 wt% CaCN2 additives. With 0.5 to 3.0 wt% added CaCN2 and sintering at 1600 to 1700°C, only the AlN phase was observed in the XRD patterns. In the TEM and electron diffraction (ED) patterns, the minor phase, 3CaO·Al2O3, appeared around the AlN grain boundaries. Based on the SEM observation, the well-faceted grain morphology was considered to be due to a predominant intergranular fracture. The dielectric constant of the AlN specimens were about 8.6 and 8.2 for 150 kHz to 10 MHz, respectively, when the samples were sintered at 1650°C for 1, 3 and 6 h. The electric resistance of the AlN specimens approached 3.87×1012 Ω. The trend of the electric resistance variation in the specimens was the same as that of the linear shrinkage and relative density of the specimens.
Studies on Meniscus and Diameter Stability during the Growth of Fiber Crystals by the Micro-Pulling-Down Method
Authors: Rudolph Peter , Yoshikawa Akira , Fukuda Tsuguo
Published: October 2002

The stable capillary growth conditions for pulling, from melt, 500-mm-long fiber crystals with constant diameter in the region 150–270 µm by the micro-pulling-down method are investigated. As a model, a substance with the sapphire/YAG eutectic composition is used. The experimental results are compared with theoretical predictions. In order to obtain long fibers with a fine eutectic microstructure, these studies were focused on the meniscus stability at high growth rates of up to 20 mm min-1. A well-adapted relation between heating power and pulling velocity was ascertained. The results are also generally applicable for fiber crystal growth of other materials.
Single-Oriented Growth of (111) Cu Film on Thin ZrN/Zr Bilayered Film for ULSI Metallization
Authors: Hideto Yanagisawa Hideto Yanagisawa , Katsutaka Sasaki Katsutaka Sasaki , Hidekazu Miyake Hidekazu Miyake , Yoshio Abe Yoshio Abe
Published: October 2002

We investigated the influence of ZrN/Zr bilayered film thickness on the (111) Cu orientation and the thermal stability of the Cu/ZrN/Zr/Si contact system by X-ray diffraction and Auger electron spectroscopy analyses. We confirmed that the single-oriented growth of (111) Cu can be realized by interposing the ZrN (400 Å)/Zr (200 Å) bilayered film between Cu and Si. It was revealed that the (111) Cu/(111) ZrN/(002) Zr/(001) Si contact system is satisfactorily stable up to 600°C without undesirable interfacial reaction and interdiffusion, maintaining the low contact resistivity of the ZrSi2 adhesion layer at the Si interface and the single-oriented state of the (111) Cu overlayer.
Composition Control of NiTi Shape Memory Alloy Films Formed by Sputter Deposition with a Composite Target
Authors: Takeda Fumio , Yamazaki Toshinari , Nakajima Takayoshi
Published: October 2002

In order to obtain NiTi films by magnetron sputtering, the authors devised a target composed of Ti and Ni rings and a Ti disk. The fabricated films were analyzed by energy-dispersive X-ray analysis (EDX) and Rutherford backscattering spectrometry (RBS). X-ray diffraction measurements (XRD) of the films were also carried out. It was shown that the composition of the film formed with the target was easily controlled with an accuracy of 0.5 at.% by changing the electric current flowing through the solenoid coil of an electromagnet. The composition of the film was affected by the Ar gas pressure. It was also shown that a film with an in-depth composition gradient was easily formed. The obtained films were confirmed by a bending test to show the shape memory effect.
Ion Irradiation Effect on the Microscopic Potential Distribution of MgO Surface
Authors: Tomohiro Yamada Tomohiro Yamada , Yasushi Motoyama Yasushi Motoyama , Youichi Ikarashi Youichi Ikarashi , Masahiro Sasaki Masahiro Sasaki , Junji Itoh Junji Itoh , Shigehiko Yamamoto Shigehiko Yamamoto
Published: October 2002

The microscopic surface potential images of ion-bombarded MgO films, as a model of the protecting layer of a plasma display panel (PDP) in operation, are observed for the first time with a scanning Maxwell-stress microscope. From the obtained images and their temporal variations, we find that ion bombardment induces the uniform shift and the speckled distribution of the MgO surface potential, which are considered to be due to weakly bound and strongly trapped charges, respectively. The results indicate that ion bombardment causes the modification of the local electronic structure and the huge electric patch field near the surface.
Improving the Oxidation Resistance of Base Metal Powders
Authors: Tsur Yoed , Adair James H. , Randall Clive A.
Published: October 2002

A straightforward technique was used to improve the oxidation resistance of base metal fine powders. It is based on using a very thin (monolayer) coating of a noble metal on base metal particles. In all examples experimentally evaluated, improvement of the oxidation behavior was achieved. The cementation process involved for the coating is described. The thermodynamic and kinetic differences between the treated and base metal powders are referred to phenomenologically. Some possible technological applications, in particular in the multilayer devices arena, are discussed.
Production of Pure Electron Plasmas Using a Field Emitter Array
Authors: Hitoshi Tanaka Hitoshi Tanaka , Tatsuya Sodekoda Tatsuya Sodekoda , Takashi Maekawa Takashi Maekawa , Souichirou Yamaguchi Souichirou Yamaguchi , Makoto Asakawa Makoto Asakawa , Yasushi Terumichi Yasushi Terumichi
Published: October 2002

A field emitter array (FEA) is found to be useful for the production of pure electron plasmas. The FEA is robust and easy to handle under the ultra-high vacuum condition. The electrons from the FEA are accumulated in the trap and the accumulated electron number can be easily controlled by varying the potential depth of the trap.
Simulated Noncontact Atomic Force Microscopy Images of Si(001) Surface with Silicon Tip
Authors: Tagami Katsunori , Tsukada Masaru
Published: October 2002

We simulated the noncontact atomic force microscopy (nc-AFM) images of Si(001) surfaces using the Si tip based on the tight-binding model. We find that only up dimer atoms are observed slightly outside the dimer sites. This outward shift is explained based on two points. One point is that the dangling bonds on the up dimer atoms, which interact with the tip apex, are tilted outward. The other point is that the space between the adjacent dimer rows looks slightly bright on the c(4 ×2) phase, since the tip located above the midpoint of the two dimer rows is subjected to attractive forces from the up dimer atoms on both sides.
Growth Rate and Crystallinity of Nanocrystalline Silicon Film Grown by Electron Beam Excited Plasma Chemical Vapor Deposition
Authors: Ito Tadashi , Imaizumi Mitsuru , Yamaguchi Koji , Okitsu Kazuhiko , Konomi Ichiro , Yamaguchi Masafumi , Hara Tamio , Ban Masahito , Tohkai Masakuni , Kawamura Kazuhiko
Published: October 2002

Using electron beam excited plasma chemical vapor deposition, nanocrystalline Si films can be grown without H2 dilution. This paper describes the effects of growth parameters on the growth rate and the crystallinity of Si films.
Production of Vanadium–Carbon Clusters Using DC Arc Discharges with Pulsed Helium/Methane Gas Injection
Authors: Nagatsu Masaaki , Kitagawa Nobuhiko , Takada Noriharu
Published: October 2002

Experimental studies of the synthesis of new types of vanadium–carbon clusters have been carried out using dc arc discharges, where a pair of graphite rods mixed with the vanadium carbide (VC) powders were used as the electrodes. A high-pressure pulsed gas injection technique, where pulsed He gases were periodically injected into the dc arc plasma to cool the excited carbon and vanadium atoms, was used. The effect of an addition of carbon atoms on cluster production was also examined by injecting pulsed CH4 gases in addition to high-pressure He gas pulses. The soots produced in the dc arc discharges were analyzed using a laser desorption reflectron type time-of-flight (TOF) mass spectrometer. Experimental results show that when CH4 gas was added to He gas with a partial pressure of 15%, enhanced V
n
C2n
clusters with a VC2-mass spacing of Δm/z=75 were detected in the mass range of 225<m/z<675. Experiments show that these vanadium–carbon clusters are formed by the vanadium atoms evaporated from the electrodes and the carbon atoms supplied from the injected CH4 gas.
Ionization Coefficient in Gases under Nonuniform Electric Fields
Authors: Date Hiroyuki , Ikuta Nobuaki , Kondo Keiichi , Satoh Kohki , Shimozuma Mitsuo , Tagashira Hiroaki
Published: October 2002

A one-dimensional nonuniform electric field model between parallel plane electrodes is used to study the behavior of electron swarms in spatially distorted electric fields such as that in the dc-sheath region near the anode. We investigate electron kinetics in the nonuniform field, taking into account the α-parameter associated with the ionization and the drift processes of electrons. The general expression of the α-parameter in the Boltzmann equation analysis using the arrival-time spectra (ATS) method is presented. Then, a demonstration of the swarm behavior is carried out using a Monte Carlo simulation to examine the validity of the parameter description.
Cross-coupling Properties of Ultrasonic Phased Array Probe
Authors: Adachi Hideo , Funakubo Tomoki
Published: October 2002

The frequency dependence of cross-coupling is described for a phased array probe developed for sector-scanning endoscopic ultrasonic diagnosis. The sweep frequency range is set from 0.5 MHz to 10.5 MHz for a 48-element phased array transducer with a center frequency of 5 MHz. Cross-coupling measurements were carried out on various piezoelectric elements at different positions in the probe. The relationship between the cross-coupling and the position of piezoelectric elements as determined by the measurements shows good agreement with the results of static-mode finite-element method (FEM) calculations.
A Simulation Study of the Global Orbit Feedback System for Pohang Light Source
Authors: Kim Kukhee , Shim Kyuyeol , Choi Jinhyuk , Cho Moohyun , Namkung Won , Ko In Soo
Published: October 2002

This paper describes the simulation of the global orbit feedback system using the singular value decomposition (SVD) method, the error minimization method, and the neural network method. Instead of facing unacceptable correction result raised occasionally in the SVD method, we choose the error minimization method for the global orbit feedback. This method provides minimum orbit errors while avoiding unacceptable corrections, and keeps the orbit within the dynamic aperture of the storage ring. We simulate the Pohang Light Source (PLS) storage ring using the Methodical Accelerator Design (MAD) code that generates the orbit distortions for the error minimization method and the learning data set for neural network method. In order to compare the effectiveness of the neural network method with others, a neural network is trained by the learning algorithm using the learning data set. The global response matrix with a minimum error and the trained neural network are used to the global orbit feedback system. The simulation shows that a selection of beam position monitors (BPMs) is very sensitive in the reduction of rms orbit distortions, and the random choice gives better results than any other cases.
Scanning Photoluminescence Microscope with Sub-micron Resolution and High Optical Throughput at a Low Temperature
Authors: Yoshimoto Masahiro
Published: October 2002

A new photoluminescence (PL) microscope has been developed with a conventional optical system to obtain a monochromated PL image at a low temperature with a spatial resolution in sub-micron range. The objective and sample were put in the identical vacuum chamber to ensure thermal insulation between them. The spatial resolution at 15 K was confirmed to be almost equal to the diffraction limit, i.e., 0.3 µm, at a wavelength of 488 nm.
Construction of Electric-Field-Modulated Picosecond Time-Resolved Fluorescence Spectrometer
Authors: Yamaguchi Shoichi , Sasaki Yutaka
Published: October 2002

We have developed a new electric-field-modulated picosecond time-resolved fluorescence spectrometer using a streak scope. We can obtain an electric-field-induced change of a fluorescence lifetime and that of an amplitude as low as 1% without losing the two-dimensional multichannel advantage of the streak scope. The spectrometer enabled us to observe electric-field-induced fluorescence quenching of titanyl phthalocyanine and obtain valuable information on the mechanism of photocarrier generation.
Emission Spectrochemical Analysis in Dry Etching Process of InP by Cl2 Inductively Coupled Plasma
Authors: Matsutani Akihiro , Ohtsuki Hideo , Koyama Fumio , Iga Kenichi
Published: October 2002

We carried out a diagnostic study of the Cl2 inductively coupled plasma (ICP) etching process by means of spectrochemical analysis using a narrow-field optical fiber probe. Many elements including etching products such as Cl+, Si, In and SiCl
x
were observed in the etching plasma. It was found that the state of the plasma is strongly dependent on the monitoring distance normal to the sample. To stabilize the dry etching process, it is important to monitor the plasma at the spot of the reaction between sample and plasma.
Characteristic Time Required to Achieve Uniform Temperature in Thermal Conduction of N-Dimensional Sphere Heated from Surface
Authors: Osuga Toshiaki
Published: October 2002

The thermal conduction of an n-dimensional sphere heated from its surface at a constant temperature was numerically analyzed using a difference scheme, where the maximum dimension number n is 100. The initial and final states of the n-dimensional sphere have uniform temperature profiles of zero and surface temperature, respectively. The characteristic time required to achieve uniform temperature inside the n-dimensional sphere was defined as the time when the temperature difference between the center and the surface is 1/100 of the surface temperature. A power law was found wherein the characteristic time was proportional to the dimension number n to the power of -1.24, which was supported by the finding that the surface area-to-volume ratio was proportional to n. By regarding slab, cylindrical and spherical thermal conduction as the heating modes of one-, two- and three-dimensional spheres, respectively, the characteristic times during heating of the one- to three-dimensional spheres, which were analytically obtained, were included in the power law.
Investigation on the Fully- and Partially-Depleted Thin-Film Silicon-on-Insulator Power Metal-Oxide-Semiconductor Field-Effect-Transistors for High-Frequency Applications
Authors: Matsumoto Satoshi , Sakai Tatsuo , Yachi Toshiaki
Published: October 2002

We compared fully-depleted (FD) and partially-depleted (PD) thin-film silicon-on-insulator (SOI) power metal-oxide-semiconductor field-effect transistors (MOSFETs). The MOSFETs were fabricated by using a sub-micron rule complementary metal-oxide-semiconductor field-effect transistor (CMOSFET) process and a reversed silicon wafer direct bonding technique. The FD MOSFET suppressed the short channel effect more effectively than the PD one. The on-resistance of the PD MOSFET was lower, and it demonstrated better high-frequency performance when the source-to-drain breakdown voltage was taken into account.
Oxygen-Related Defects Introduced by As+-Implantation through Cap Layers in Si Probed by Monoenergetic Positron Beams
Authors: Uedono Akira , Muramatsu Makoto , Ubukata Tomohiro , Tanino Hirotoshi , Tanigawa Shoichiro , Nakano Akihiko , Yamamoto Hidekazu , Suzuki Ryoichi , Ohdaira Toshiyuki , Mikado Tomohisa
Published: October 2002

The depth distributions and species of defects in 50 keV As+-implanted Si with a cap layer (SiO2 or SiN) were determined from measurements of the Doppler broadening spectra of the annihilation radiation and the lifetime spectra of positrons. Before annealing, the main species of defects below the amorphous region was determined to be divacancies. Upon annealing at 800°C, oxygen-related defects were introduced into the subsurface region (<20–40 nm). The species of these defects was identified as oxygen microclusters. The positrons were trapped by the open spaces adjacent to the clusters, and the size of these spaces was estimated to be close to that of monovacancies. The oxygen-related defects were annealed out after rapid thermal annealing at 1050°C (10 s). As+-implantation through the SiN film suppressed the introduction of recoiled oxygen atoms; as a result, the concentration of the oxygen-related defects was decreased.
Observation of Transient Enhanced Diffusion in B+-Implanted Si by Buried Boron Isotopes
Authors: Chang Ruey-Dar , Chiang Hsiao-Pai , Liu Hsien-Wen , Ho Li-Wei , Chiang Po-Chen , Tsai Jung-Ruey , Lin Jengping
Published: October 2002

A method was developed to investigate the transient enhanced diffusion (TED) of implanted boron by observing the redistribution of buried boron isotopes in the implanted region. The buried layer was created by 10B+ implantation and the implant damage was induced by 11B+ implants at various doses. With low-dose ion implantation, implanted dopants exhibit similar TED behavior as embedded dopants. For implant doses higher than 5×1014 cm-2, the uphill diffusion of 10B near the immobile 11B peak indicates the presence of TED under boron interstitial clustering. The presence of TED remains in the projected range for the high-dose implantation at 25 keV even though dense dislocations exist. However, as the implant energy decreases to 15 keV, TED is prohibited from the surface to the project range.
Design of Single-Wafer Furnace and Its Rapid Thermal Processing Applications
Authors: Yoo Woo Sik , Fukada Takashi , Kuribayashi Hiromitsu , Kitayama Hirofumi , Takahashi Nobuaki , Enjoji Keiichi , Sunohara Kiyoshi
Published: October 2002

A resistively heated, vacuum- and atmospheric-pressure-compatible, single-wafer furnace (SWF) system is designed to improve the operational flexibility of conventional furnaces and the productivity of single-wafer rapid thermal processing (RTP) systems. The heat source design and system operation concepts are described. The temperature measurement/control techniques and thermal characteristics of the heat source are described. The heat transfer mechanism between the heat source and Si wafer is discussed. Temperature and process uniformity in SWF were demonstrated in TiSi formation, implant annealing and thin-oxide formation. The defect-generation phenomenon in Si wafers during atmospheric pressure RTP in a SWF system is investigated as a function of temperature, process time, wafer handling method and speed. Highly repeatable slip-free RTP results were achieved in 200-mm-diameter Si wafers processed at 1100°C for 60 s (up to 5 times) through the optimization of the wafer handling method and speed.
Metalorganic Vapour Phase Epitaxy Growth of InP-based Heterojunction Bipolar Transistors with Carbon Doped InGaAs Base Using Tertiarybutylarsine and Tertiarybutylphosphine in N2 Ambient
Authors: Keiper Dietmar , Velling Peter , Prost Werner , Agethen Michael , Tegude Franz-Josef , Landgren Gunnar
Published: October 2002

A process for growth of heterostructure bipolar transistors (HBT) using tertiarybutylarsine (TBA) and tertiarybutylphosphine (TBP) in N2 ambient is realised, which is compatible with a high temperature overgrowth, thus suitable for the vertical integration of a laser structure on top of an HBT. A high growth temperature for the C–InGaAs base is favourable, to ensure no degradation during subsequent growth. Increasing the growth temperature after the base from 500°C to 680°C within the emitter layer instead of at the base-emitter interface was found to improve the ideality factors, the dc gain and the turn-on voltage.
Theoretical Analysis of Polarization Insensitive InGaAsP Multiple-Quantum-Wells Eletroabsorption Modulators with Negative Chirp
Authors: Guo Chun-Lei , Sun Chang-Zheng , Hao Zhi-Biao , Luo Yi
Published: October 2002

Polarization sensitivity of InGaAsP electroabsorption (EA) modulators is analyzed by the fractional-dimensional approach. Chirping parameter α is then calculated using Kramers-Krönig relations. It is found that polarization-insensitive and negative chirp operation can be realized simultaneously for InGaAsP multiple-quantum-wells (MQW) EA modulators with optimized well width and amount of strain. We propose a polarization-insensitive InGaAsP EA modulator with 9-nm-wide 0.38% tensile strained quantum wells. The chirping parameter α is estimated to be around -2 for the first 3 dB of transmission, while the modulation characteristics remain polarization-independent up to 80 kV/cm, corresponding to an extinction ratio of over 15 dB.
Metalorganic Molecular Beam Epitaxy of GaN Thin Films on a Sapphire Substrate
Authors: Kim Min-Ho , Lee Sung-Nam , Park Nae-Man , Park Seong-Ju
Published: October 2002

A metalorganic molecular beam epitaxy (MOMBE) system equipped with a radio frequency plasma cell was employed to grow GaN films at a low temperature of 650°C. The structural and optical properties of GaN films were studied by X-ray diffraction, scanning electron microscope, and photoluminescence (PL). The GaN films were epitaxially grown on the nitridated sapphire substrate with a wurtzitic single crystalline phase. The atomic nitrogen flux was found to be closely related to the GaN growth, particularly in the crystal quality of the GaN layers. An efficient emission line, which is associated with the recombination of the free-excitions, was observed at 10 K PL and a strong bandedge emission was also obtained even at room temperature PL.
Investigation of Hydrogen Chemisorption on GaAs (111)A Ga Surface by In Situ Monitoring and Ab Initio Calculation
Authors: Yuriko Matsuo Yuriko Matsuo , Mikihiko Nimura Mikihiko Nimura , Akinori Koukitu Akinori Koukitu , Yoshinao Kumagai Yoshinao Kumagai , Hisashi Seki Hisashi Seki , Seiichi Takami Seiichi Takami , Momoji Kubo Momoji Kubo , Akira Miyamoto Akira Miyamoto
Published: October 2002

Hydrogen chemisorption on the GaAs (111)A Ga surface is investigated under atmospheric pressure using an in situ optical monitoring system which consists of GaAs halogen transport atomic layer epitaxy (ALE) and surface photoabsorption (SPA) systems. The results of the in situ monitoring indicate the existence of a stable hydrogen-terminated surface. It is shown that hydrogen in the carrier gas reacts dissociatively with the (111)A Ga surface, and the relationship between the surface hydrogen coverage and hydrogen partial pressure is explained well by the Langmuir isotherm with dissociation. Atomic configuration on the surface is examined further by means of ab initio molecular dynamics calculation. The total energy change due to the calculated process is very close to the standard enthalpy of adsorption obtained by the experiment.
The Influence of Cu and Au on Field Aided Lateral Crystallization of Amorphous Silicon Films
Authors: Lee Chan-Jae , Lee Jae-Bok , Chung Yong-Chae , Choi Duck-kyun
Published: October 2002

The effect of Cu and Au on field aided lateral crystallization (FALC) process of amorphous silicon films was investigated. Although both Cu and Au induced the crystallization of a-Si in contact with those metals, only Cu was able to induce the lateral crystallization toward a metal-free region. Especially, the crystallization caused by Cu atoms was noticeably accelerated at the edge near the negative electrode side in every pattern under the electric field, while the lateral crystallization was retarded at the positive electrode side. The crystallization velocity increased with the applied field intensity and the annealing temperature, but it decreased with the size of test pattern. However, electric field did not affect the crystallization by Au. The maximum crystallization velocity using Cu was 770 µm/h at 500°C in the electric field of 4 V/cm and the lateral crystallization was achieved at a temperature as low as 450°C.
Spectroscopic Ellipsometry Studies on Ultrathin Hydrogenated Amorphous Silicon Films Prepared by Thermal Chemical Vapor Deposition
Authors: Hazra Sukti , Yamanaka Mitsuyuki , Sakata Isao , Tsutsumi Toshiyuki , Maeda Tatsuro , Suzuki Eiichi
Published: October 2002

Ultrathin amorphous silicon films prepared by the thermal chemical vapor deposition (CVD) have been investigated using a spectroscopic ellipsometer. The analysis of ultraviolet-visible (UV-VIS) spectroscopic ellipsometric data reveals the morphology of the ultrathin films. To determine the optical functions of such films from ellipsometric data, a new parameterization, i.e., the Sellmeier law with four Lorentz oscillators, has been successfully introduced. A direct correlation has been made between the new parameters and the change of optical functions with the thickness of ultrathin a-Si:H films. By the analysis of ellipsometric data, it has been shown that the formation of dense Si matrices with low structural disorder is possible when the thickness of a-Si:H is more than about 8 nm, and the film with a thickness of less than around 3.5 nm develops voids.
Analysis of a Novel Self-Aligned Elevated Source Drain Metal-Oxide-Semiconductor Field-Effect Transistor with Reduced Gate-Induced Drain Leakage Current and High Driving Capability
Authors: Kim Kyung-Whan , Choi Chang-Soon , Choi Woo-Young
Published: October 2002

A new self-aligned elevated source drain (E-S/D) metal-oxide-semiconductor field-effect transistor (MOSFET) structure which can effectively reduce the gate-induced drain leakage (GIDL) current without sacrificing the driving capability is proposed and analyzed. Proposed E-S/D structure is characterized by sidewall spacer width and recessed-channel depth which are determined by dry etching process. Elevation of the Source/Drain extension region is realized so that the low-activation effect caused by low-energy ion implantation can be avoided. The GIDL current in the proposed E-S/D structure is reduced as the region with the peak electric field is shifted toward the drain side.