bluuebunny/crossref_metadata_2025 huggingface dataset:
Enhancement of Small-Signal Gain and Mode-Volume in a FAF CO2 Laser Amplifier due to Cooling of Wall Temperature
Authors: Tsuchida Eiichi , Sato Heihachi
Published: February 2005

Cooling the wall temperature of a fast-axial flow (FAF) CO2 laser amplifier improved both the small-signal gain and its spatial distribution and increased the effective mode-volume significantly under the turbulent flow condition. Considering the dependences of the gain parameter G and the line-shape function denoted by the Voigt function on the wall temperature T
w and the radial distance r, the experimental results of the T
w-dependent small-signal gain γ on the axis and its radial distribution are theoretically explained. On cooling T
w from room temperature to -30°C, about 17% increase of the gain was obtained and its mode-volume was much improved. The spatial distribution of the small-signal gain becomes almost uniform over the cross section of the plasma tube particularly under the turbulent flow region greater than the gas-flow velocity of 170 m/s.
Refractive Index Ellipsoids of a Modified Polycarbonate Magneto Optical Memory Disk Substrate
Authors: Shirouzu Shigenori , Sakamoto Shuji , Shigematsu Kazuyoshi , Nakagawa Takashi , Tagami Sanae
Published: February 2005

The refractive index ellipsoids (RIE) of a magneto optical memory disk substate made by a modified polycarbonate, in which the refractive index anisotropy (RIA) of the constructive units is 1/4 of that for bisphenol-A-polycarbonate (BisAPC), were measured. Similar to the RIE of the BisAPC disk substrate, the RIE of this disk substrate were muffin-shaped; that is, the thickness direction was substantially smaller than the other directions, and its RIA was almost 1/2 of that for BisAPC.1)
High-Pressure Raman Study of Liquid and Molecular Crystal Ethane Up to 8 GPa
Authors: Shimizu Hiroyasu , Shimazaki Izumi , Sasaki Shigeo
Published: February 2005

The Raman scattering of liquid and crystalline ethane has been measured at pressures up to 8 GPa in a diamond anvil cell equipped for loading of condensable gases. Characteristic spectral features of intramolecular modes at 300 K indicate that the pressure-induced liquid→solid II phase transition of ethane occurs at P=2.5 GPa. This result is supported by good agreement with the extrapolation (to 300 K) of the Simon-Glatzel equation previously determined at low temperatures.
Fractal Structure in Focal Conics
Authors: Nakagawa Masahiro
Published: February 2005

In this paper, we shall first report on a fractal structure observed in liquid crystals. For the spatial distribution of the focal conics in a ferroelectric SmC* phase, the fractal dimension is evaluated as ∼1.7 at room temperature. According to a simple statistical analysis, the interaction potential between two focal conics is expected to be inversely proportional to r
3; here r is the relative distance between two focal conics.
Relationship between Surface Treatment of ZuTe Substrates and Morphology of CdSe Epitaxial Layers in Liquid Phase Epitaxy
Authors: Onome Suguru , Yamada Toru , Sano Masatoshi , Aoki Masaharu
Published: February 2005

The epitaxial layers of CdSe were grown on ZnTe at 560°C by liquid phase epitaxy (LPE) from a Te solution in an open tube apparatus. The morphology of the grown layer was greatly influenced by the smoothness of the substrate surface. The effects of the meltback solution and the chemical etchant on the morphology of the grown layer were investigated. The layer grown with the Cd+Zn alloy as a meltback solution had a smooth and flat surface without hollows between the grown layer and the substrate, although there were some hollows near the interface with Te meltback or without meltback. Chemical etching of the substrate also affected the morphology of the grown layer. Etching with a mixture solution of K2Cr2O7 and HNO3 caused the surface of the ZnTe substrate to become mirrorlike and resulted in the growth of CdSe layers with smoother surfaces.
Surface Processes in ALE and MBE Growth of ZnSe: Correlation of RHEED Intensity Variation with Surface Coverage
Authors: Zhu Ziqiang , Hagino Minoru , Uesugi Katsuhiro , Kamiyama Satomi , Fujimoto Masami , Yao Takafumi
Published: February 2005

The surface processes in ALE (atomic layer epitaxy) and MBE (molecular beam epitaxy) are investigated both by numerical calculation for the surface coverage based on the model proposed by the authors and by in situ observation of the RHEED intensity variation. The sublimation process is dominated by the Se sublimation from the surface and the adsorption process is influenced by the desorption of Se from both the surface and the precursor states in the range of practical ALE and MBE growth temperatures. To achieve the layer-by-layer growth during ALE the substrate temperature should be set below 300°C. It is also shown that the RHEED intensity variation corresponds to the change in surface coverage during ALE and MBE growth as determined via comparison of the model calculation for surface coverage with the experimental RHEED data.
Low-Temperature Growth of SiO2/InP Structure Prepared by Photo-CVD
Authors: Su Y. K. , Huang C. R. , Chou Y. C.
Published: February 2005

A low-temperature (25-300°C) growth of silicon dioxide films has been prepared from monosilane (SiH4) and nitrous oxide (N2O) gases by mercury-sensitized photo chemical-vapor deposition (photo-CVD) using a 253.7 nm ultraviolet light lamp. The PHOTOX silcon dioxide (i.e., SiO2 formed by the photo-CVD process) deposited at 250°C has a refractive index of about 1.46 and a breakdown strength of 7.0 × 106 V/cm. Capacitance-voltage measurement of the InP MOS structure yielded a minimum interface state density as low as 1.2 × 1011 cm-2eV-1 when the films were prepared at a substrate temperature of 250°C.
Molecular Dynamics Study of the Structural Changes of Ultra-fine Particles
Authors: Sasajima Yasushi , Arakawa Takushi , Ichimura Minoru , Imabayashi Mamoru
Published: February 2005

The dynamics of ultra-fine particles (UFP's) have been studied by the molecular dynamics method. The Morse-type function has been assumed as the interaction potential between the atoms in UFP's. The numbers of atoms of the calculated systems have been 13 to 459. The particles with magic numbers, 13, 55 and 147, have shown the structural change from fcc to icosahedron, while the system of 459 atoms has not.
Plasma Processing Control by a Magnetic Field Crossed to a Sheath Electric Field
Authors: Tanizuka Noboru
Published: February 2005

This paper deals with a theoretical concept and method of control in plasma processing technologies. Its aim is the selection of ion species and the control of ion kinetic energy bombarding a substrate electrode. The selection and the control are practised within the sheath between the electrode and a DC or rf discharge plasma by applying an external magnetic field crossed to the sheath electric field.
On the Determination of the Trap Depths from Thermally Stimulated Currents II
Authors: Maeta Shigeyoshi , Yoshida Fukuzo
Published: February 2005

A new asymptotic estimation method (the H-method), which enables one to estimate the exact energy depth E

t
of a trap from the TSC peak and one of other coordinates of the higher side of the peak temperature T
p, has been proposed. From the establishment of this proposal and the L-method estimated from the lower side, more exact estimation of E

t
and a new application were made possible. The m characteristics that provide a basis for judging whether a TSC curve is contributed by a single trap only or by multiple traps have been reported. They show a perfect flatness with the same E

t
value in the range from ca. 10% to 90% of 1/m if the TSC curve is contributed by a single trap only. The m characteristics of the coefficient C

i
(=E

t
/k
T
p) have been proposed. A simple and convenient equation of the H-method and an expression of the asymptotic estimation method without T
p are presented.
Flame Structure and Diamond Growth Mechanism of Acetylene Torch
Authors: Matsui Yasuji , Yuuki Akimasa , Sahara Mieko , Hirose Yoichi
Published: February 2005

To understand the diamond growth mechanism in C2H2/O2 flame, we carried out gas analyses for various mixture ratios (R=C2H2/O2) with laser-induced fluorescence and mass spectrometric techniques. These measurements show that CO and H2 are the dominant gases in the feather, and that C2H2 and C-containing radicals (e.g., C2H, CR, Cn, n=1-3) are minor species. Their concentrations are found to be consistent with the equilibrium values estimated by the adiabatic calculation. The feather is formed by the inter-diffusion and reactions between these C-radicals and O-radicals (e.g., O and OH), which are produced in the intermediate zone by the oxidation with O2 supplied through the secondary flame. It is also found that R-dependences of the diamond growth rate is in good agreement with those of CH and C2 concentrations in the feather.
Experimental Studies on Biosensing by SPR
Authors: Sun Xiaochun , Shiokawa Showko , Matsui Yosikazu
Published: February 2005

Biosensing using surface plasmon resonance is experimentally studied. The results obtained by detecting the bioresponse of the α-Feto protein system and cyclic experiments show that this technique has potential application in the field of biosensing. The effects of an organic layer on detecting sensitivity and restoration of sensors are also discussed.
Large Quantum-Confined Stark-Effect in Quaternary InGaAlAs Quantum Wells
Authors: Wakita Koichi , Kotaka Isamu , Nakao Masashi , Asai Hiromitsu
Published: February 2005

A large energy shift of excitonic absorption peaks in quaternary InGaAlAs quantum wells operating in the 1.5 µm wavelength region has been demonstrated in a waveguide configuration. Shifts of up to 30 meV (600 Å) and 17 meV (270 Å) have been achieved for the electron-to-heavy-hole and the electron-to-light-hole exciton absorption peaks, respectively. These shifts were obtained using a reverse bias of 6 V and without causing large broadening of exciton features. These values agree well with the calculated values.
Structural Investigation of Si(111) √3×√3-In by Low-Energy Ion-Scattering Spectroscopy
Authors: Izumi Koichi , Takahashi Toshio , Kikuta Seishi
Published: February 2005

The atomic structure of Si(111) √3×√3-In was investigated by low energy ion scattering spectroscopy with 1 keV He+ ions. Azimuthal angular distributions of scattered ions suggest that the In atoms are located in the three-fold sites on top of the second layer Si atoms. Comparing the experimental distribution as a function of the incident angle with the calculation using the Thomas-Fermi-Molière potential taking of the thermal vibrations, the Debye temperature of the surface In atoms and the bond length between the In atom and the first layer Si atom were estimated.
Effect of Carbon and Oxygen Precipitation on Gold Diffusion in Silicon
Authors: Itoh Yoshiko , Sugita Yoshimitsu , Nozaki Tadashi
Published: February 2005

The effect of the precipitation of carbon and/or oxygen on the diffusion of gold in Czochralski(CZ)- and float-zone(FZ) silicon crystals were studied using the neutron activation analysis for gold, infrared spectrophotometry for substitutional carbon and interstitial oxygen and charged-particle activation analysis for total concentration of carbon and oxygen. The diffusion of gold was found to be enhanced by the existence of carbon and/or oxygen precipitates. This enhancement has been related to the precipitation of carbon and oxygen in CZ samples, whereas the gold diffusion in FZ samples, having less oxygen and no carbon precipitation, was not enhanced.
A Study of the Electronic Properties of the GaAs (110) Surface by Using the Cluster-Bethe-Lattice Method
Authors: Lin S. Y.
Published: February 2005

The tight-binding/cluster-Bethe-lattice approach is used to study the electronic properties of the GaAs (110) surface. Two different sets of tight-binding parameters are used in this study. They are the sp3 model and the sp3s* model.
The density of states for the GaAs Bethe lattice and the surface atoms are calculated. The ideal surface has two sharp features in the energy gap. The relaxed surface is studied by using different tilted angles of the surface bond. It is found that the surface states are very sensitive to the angle of relaxation. The two sharp features in the gap shift toward either the valence band or the conduction band gradually as the tilted angle is increased and merge in the bands when the angle is 20°. The resonant feature at 2 eV below the VBM as found by experiments is produced in our calculation except for the full relaxation. The desired tilted angle lies between 20° and 34°.
Phosphorus Doping and Photoinduced Changes in Hydrogenated Amorphous Silicon-Carbon Alloy Films
Authors: Basu N. , Ganguly Gautam , Ray Swati , Barua A. K.
Published: February 2005

Hydrogenated amorphous silicon carbon alloy films have been prepared by the RF glow discharge technique. The effect of phosphorus doping on the optoelectronic properties has been studied at different silane/methane flow compositions. The reduction of doping efficiency in wider-band-gap material has been attributed to increasing disorder with carbon incorporation. The spectral photoresponse data have been analysed to show that the effect is consistent with current models for doping in tetrahedral amorphous semiconductors. The light-induced changes in the properties have been explained in terms of the relative effects of phosphorus and/or carbon incorporation.
Heteroepitaxial Growth of GaAs Films on CaF2/Si(511) Structures Prepared with Rapid Thermal Annealing
Authors: Asano Tanemasa , Ishiwara Hiroshi , Furukawa Seijiro
Published: February 2005

Heteroepitaxial growth of CaF2 films on (511)Si and GaAs films on CaF2 /Si(511) structures is investigated. CaF2 films and GaAs films are grown by vacuum evaporation and molecular beam epitaxy, respectively. Ion channeling measurements and replica transmission electron microscopy show that CaF2 films having good crystalline quality and surface steps can be formed by annealing at 900°C for 30 s after the growth at 550°C. GaAs films having smooth surfaces and good crystalline quality can be grown on the annealed CaF2/Si(511) structures. Differences in crystalline defects between GaAs films grown on (511) substrates and those on (100) substrates are discussed based on results obtained from cross-sectional transmission electron microscopy.
Injection Controlled Superconducting Links
Authors: Takeuchi Kiyoshi , Okabe Yoichi
Published: February 2005

This paper concerns a three-terminal superconducting device which is called an injection-controlled link. First, experimental static characteristics of the device made of Nb and Al are presented and discussed. Then, the performance of the device as a switching element is theoretically calculated, and it is shown that a switching delay of less than 1 ns is possible. Finally, the hot-spot growth speed, which partly determines the switching delay, is measured and compared with the simulation results.
Structure-Parameter Dependence of Modality of Macroscopic Quantum Effect in Superconductor Junction (I) –Tunnel-Type Junction–
Authors: Sugahara Masanori , Yoshikawa Nobuyuki
Published: February 2005

Quantum mechanical analysis of charge and flux fluctuation in a superconductor tunnel junction shows that the combination of conductance and capacitance parameter of the junction determines the modality of the macroscopic quanturn effect: flux-quantization type or charge-quantization type.
Preparation and Properties of (NiZn)Fe2O4 Film by RF Reactive Sputtering
Authors: Chen Qing , Tsujimoto Hiroaki , Shirae Kimisuke
Published: February 2005

A reactive rf-sputtering method is used for depositing polycrystalline (NiZn)Fe2O4 films. The relations between the magnetic properties of the ferrite films and the sputtering conditions are examined in detail. The best condition of rf-sputtering, under which the magnetization of the films as well as the bulks is obtained and the initial relative permeabilities amount to 50∼100 even in the frequency region over the Snoek's limit, is found. Finally, the way to improve the preparation of the films is discussed.
Uniaxial Magnetostatic Anisotropy of Assemblies of Single-Domain Particles
Authors: Masuda Morio , Shiomi Shigeru
Published: February 2005

The magnetostatic energy was derived theoretically for an assembly in which single-domain particles of rectangular parallelepipeds form a three-dimensional periodic array in a nonmagnetic substance. The present theory predicts that the material of such a magnetic assembly exhibits uniaxial magnetic anisotropy if its external shape is ellipsoidal. It was found that the uniaxial anisotropy energy density of the magnetic assembly according to Néel's model corresponds to a special one of assembly configurations used in the present model. The uniaxial anisotropy constant observed on thin discs of Alnico single crystal was also found to be interpreted well by the present theory.
Deep Levels in Electron-Irradiated GaP at 10 MeV
Authors: Endo Tamio , Hirosaki Yuushi , Uchida Eiji , Miyake Hideto , Sugiyama Koichi
Published: February 2005

Deep levels in the electron-irradiated n-type GaP at 10 MeV were investigated by deep-level transient spectroscopy (DLTS). The DLTS spectrum depends strongly on the sample species. A total of seven different electron traps were detected from the various samples. The activation energies of the traps are 0.16, 0.26, 0.32, 0.38, 0.44, 0.62 and 0.71 eV. The individual introduction rate of the traps ranges from 0.27 to 0.73 cm-1, and the total introduction rate ηtotal is 1.4 cm-1. The depth distribution of the trap densities indicates the high mobility of the defects under the irradiation. The experimental results suggest that the majority of radiation defects undetected by DLTS agglomerate to form very complex defects or damaged regions, and they form very deep energy levels. Broadening of the DLTS spectrum was observed.
Polarization Reversal in an Amorphous Copolymer of Vinylidene Cyanide and Vinyl Acetate Studied by Means of Measurement of Second Order Dielectric Response
Authors: Ikeda Susumu , Kiba Hisanaga , Kutani Masayuki , Wada Yasaku
Published: February 2005

The second order dielectric constant of a copolymer of vinylidene cyanide and vinylacetate is presented as a function of a bias electric field. The results suggest that the polarization reversal occurs in the copolymer with a polarization-electric field hysteresis. The polarization reversal switching time of the copolymer is observed from the temporal change of the linear dielectric constant and is found to be much longer than that of conventional ferroelectric polymers. These facts suggest that this amorphous copolymer behaves like a ferroelectric material with a long relaxation time of polarization reversal.
Viscoelastic Properties of the Smectic A* and C* Phases Studied by a New Dielectric Method
Authors: Gouda F. , Skarp K. , Andersson G. , Kresse H. , Lagerwall S. T.
Published: February 2005

A method for the determination of rotational viscosity and elasticity associated with the director rotation on the C
* cone is proposed. The method is based on measurements of the Goldstone mode dielectric strength and relaxation frequency, supplemented with values for spontaneous polarization, tilt angle and pitch. Furthermore, the temperature dependence of the soft mode dielectric strength and relaxation frequency has been measured in the A
* and C
* phases. From the measurements in the A
* phase we have evaluated the temperature dependence of the soft mode rotational viscosity which was found to exhibit a critical behaviour of the form γθ≈(T-T
c)-0.25.
Monte Carlo Evaluation of a New Track-Finding Method for the VENUS Muon Detector
Authors: Asano Yuzo , Hatanaka Makoto , Koseki Tadashi , Mori Shigeki , Shirakata Masashi , Yamamoto Kazumichi
Published: February 2005

A new method of finding a track is devised for the VENUS muon detector composed of eight-cell drift-tube modules, each cell having a rectangular cross section of 5×7 cm2. The new method, in which fourth-order equations are solved by the Ferarri-Cardano method, is especially powerful for a track having a large incident angle with respect to the line normal to the anode-wire plane of a drift tube, compared to the presently used method in which a track is determined by the intersecting points of an equi-drift-distance circle and the anode-wire plane. Cosmic-ray test data for the forward-backward part muon detector support these simulation results.
Time-Resolved Electron Energy Distribution Function in Time-Varying Weakly Ionized Plasmas
Authors: Ohe Kazuyuki , Kimura Takashi
Published: February 2005

A method for detecting the time-resolved electron energy distribution function for periodically varying plasmas is proposed. The method is applied to detecting the time-resolved distribution function for ionization wave packets externally excited in the helium positive column. The distribution function shifts to a higher one with increasing wave amplitude, yielding the two-humped distribution in a certain duration of the negative phase of fluctuated electric field due to the increase in acceleration of electrons.
Coupling to the Fast Wave by the Phased Dipole Array Antenna near the Lower Hybrid Frequency
Authors: Matsumoto Kazunori , Ohkubo Kunizo
Published: February 2005

A simplified fast wave coupling theory for a phased dipole array is described with non zero poloidal wave number for the step-plus-ramp density model, taking boundary conditions of fields into consideration. The coupling property looking from the transmission line is also derived since characteristic impedance of the coaxial feeder is, in general, different from the antenna impedance. The numerical calculations on coupling are carried out and compared with experimental results on the global reflection coefficient.
Sub-Half-Micron i-Line Lithography by Use of LMR-UV Resist
Authors: Jinbo Hideyuki , Yamashita Yoshio , Endo Akihiro , Nishibu Satoshi , Umehara Hiroshi , Asano Takateru
Published: February 2005

Negative photoresist, LMR-UV, has been developed for i-line lithography. It resolves isolated 0.3 µm space and 0.35 µm hole patterns of 1.0 µm thickness by using a 0.42-numerical-aperture i-line reduction projection aligner. LMR-UV gives overhung profiles because of its large absorption coefficient of 3.8 µm-1 at the i-line. New phase-shifting mask patterns which are adapted to isolated space and hole patterns for negative resist have been developed. By use of this mask, LMR-UV clearly resolves 0.25 µm space and 0.3 µm hole patterns by using the i-line aligner. This phase-shifting mask improves both resolution and focus margin.
Development of Scanning µ-RHEED Microscopy for Imaging Polycrystal Grain Structure in LSI
Authors: Tsubouchi Kazuo , Masu Kazuya , Tanaka Masanori , Hiura Yohei , Ohmi Tadahiro , Mikoshiba Nobuo , Hayashi Shigeki , Marui Takao , Teramoto Akira , Kajikawa Tetsuo , Soejima Hiroyoshi
Published: February 2005

A new type of scanning µ-RHEED (reflection high energy electron diffraction) microscope has been developed. Three diffraction spots of a RHEED pattern were simultaneously selected for imaging. The scanning µ-RHEED images were obtained from the intensity change of the diffraction spots. The distribution of normally rotated micrograins inside the same plane's grain parallel to the surface was successfully observed from the scanning µ-RHEED images. Micrograin structures of poly-Si and Cu thin films were observed with a resolution of less than one micron.
A Beamline and Its Components for SR Lithography
Authors: Kaneko Takashi , Itabashi Seiichi , Saitoh Yasunao , Yoshihara Hideo , Kitayama Toyoki
Published: February 2005

An efficient beamline for synchrotron radiation (SR) lithography has been built for the synchrotron radiation facility at NTT's Atsugi R & D Center. The relationship between the reflectivity and the surface roughness of the platinum-coated X-ray mirror, one of the key components of the beamline, is measured. The results confirm that it is necessary for the grazing angle of the mirror to be smaller than 2°. A beamline consisting of two X-ray mirror optics and two X-ray windows is proposed for exposure in an atmospheric environment. The optimum mirror optics for converging and collimating the X-ray beam are investigated using a ray-tracing technique, and their feasibility is experimentally confirmed.
Current Transients due to Delayed Charge Injection
Authors: Chen Inan
Published: February 2005

The anomalous current pulses observed in the time-of-flight experiments on layered organic photoconductors and doping modulated amorphous multi-layers have been shown to arise from the delayed injection of charge carriers by mathematical simulations. The similar but not identical features observed in the two types of samples can be accounted for by the same log-normal distribution of charge injection with the time of most probable injection in two different regimes with respect to the transit time.
Microlithography Resists Containing Poly(1,1-dimethylsilazane)
Authors: Hiraoka Hiroyuki , Ladabaum Uri
Published: February 2005

Poly(1,1-dimethylsilazane), PDMZ, mixes well with most of resist materials, cresol-formaldehyde novolak resins, poly(hydroxystyrene), chlorinated poly(1,1-methyistyrene) and others. The mixed resist solution provides uniform films when it is spin-coated on a substrate like a silicon wafer. Although it may form a C-T complex with diazonaphtho-quinone photosensitizers, the mixed photoresist keeps its photosensitivity for several weeks. Resist with PDMZ can be used as an imaging layer in RIE bilayer resist systems. Its silicon content is enriched in resist surface layers. After oxygen reactive ion etching, resist surfaces were covered with silicon oxide layers.
Ashing of Ion-Implanted Resist Layer
Authors: Fujimura Shuzo , Konno Jun'ichi , Hikazutani Ken'ichi , Yano Hiroshi
Published: February 2005

The stripping method of high-dose ion-implanted resist layers was studied on the basis of the chemical structure of carbonized layers formed by ion implantation and that of residues remaining on the wafer surface after O2 plasma ashing. The chemical structure of the carbonized layer was observed with solid NMR and that of residues was analyzed with XPS. A decrease in the etching rate of the high-dose ion-implanted resist was caused by carbonization of polymers of the resist. Residues were mainly formed during O2 plasma ashing by chemical reaction between oxygen and implanted species, i.e., the main component of residues was oxide of the implanted species. On the basis of these results, to remove the high dose ion implanted resist without damage, we developed a two-step ashing process which was composed of H2 RIE and downstream ashing, and achieved the purpose.
Very High Selective n+ poly-Si RIE with Carbon Elimination
Authors: Nakamura Moritaka , Iizuka Katsuhiko , Yano Hiroshi
Published: February 2005

The effect of carbon contamination was studied in low-temperature HBr RIE of n+-doped poly-Si etching. With a resist mask, which is a notable carbon source, selectivity (poly-Si/SiO2) was 10 to 20. With a SiO2 mask and carbon elimination from various sources such as gas, piping system and reactor wall, SiO2 etching rate was suppressed, and selectivity of more than 300 was achieved with a self-bias voltage of 400 V. Addition of a small amount of oxygen after carbon elimination removed residual carbon and enhanced the selectivity up to 3000. The anisotropic profile was not affected by carbon elimination since the side-wall protection by reaction products (SiBr
x
) was the mechanism of anisotropy. The effect of carbon on the selectivity was explained by the thermodynamics on the basis of bond strengths of reaction products.
Low Temperature Deposition of Silicon Nitride by the Catalytic Chemical Vapor Deposition Method
Authors: Matsumura Hideki
Published: February 2005

A new low temperature deposition method named “catalytic chemical vapor deposition (Cat-CVD or CTL-CVD)” is applied to obtain silicon nitride films. In the method, a N2H4, N2, and SiH4 gas mixture is decomposed by the catalytic or pyrolytic reaction with a heated catalyzer placed near substrates, so that silicon nitride films are deposited at substrate temperatures as low as 300°C with deposition rates near 1000 A/min, without plasma nor photochemical excitation. It is found that the resistivity, breakdown electric field and hydrogen content of the films are almost equivalent to those of thermal CVD films deposited at about 700°C, and that the diffusivity of depositing species appears large enough to obtain good stepcoverage.
Direct Formation of Three-Dimensional Structures in GaAs by Excimer Laser Doping
Authors: Sugioka Koji , Toyoda Koichi
Published: February 2005

Direct formation of three-dimensional structures of Si in GaAs by excimer laser doping has been demonstrated. The doped Si is limited in a very shallow region (30∼110 nm) of GaAs with very high concentration (>1×1020 cm-3) that might be controlled easily by laser irradiation conditions. By using a thin solid Si dopant source, linewidths as narrow as 0.3 µm are achieved. On the other hand, the linewidths of 0.76 µm are obtained by projection patterned doping in SiH4 gas ambient. The linewidths of the doped regions are discussed relating to the lateral profiles of the calculated transient temperature rise of the substrates.
Radiation Damage in SiO2/Si Induced by VUV Photons
Authors: Yunogami Takashi , Mizutani Tatsumi , Suzuki Keizo , Nishimatsu Shigeru
Published: February 2005

Quantitative measurements of radiation damage in SiO2/Si systems induced by VUV photons generated in various microwave plasmas are performed. The SiO2/Si system is irradiated by monochromatic VUV photons, and its flat-band voltage shift (Δ
V
FB) is measured by the C-V method. The number of effective positive charges generated in the SiO2 layer by a single VUV photon (R
f) is evaluated from the Δ
V
FB and the total VUV dose. A VUV photon is found to generate effective positive charges in SiO2 when its energy (E
p) is larger than the SiO2 band gap energy (E
g=8.8 eV). The value of R
f is on the order of 10-3∼10-2 and increases in proportional to the energy difference between E
p and E
g . A model is proposed to explain these phenomena. The model states that a VUV photon with energy E
p(>E
g) generates an electron-hole pair in the SiO2 and the holes that are not recombined are trapped in the energy state near the SiO2/Si interface.
A Transit-Time Dispersive Multi-Channel Voltage Contrast Detector
Authors: Khursheed A. , Dinnis A. R.
Published: February 2005

This paper presents the design of a new voltage contrast detector. It is proposed that voltage contrast measurements be made by recording transit times of secondary electrons as they are emitted from a specimen and collected above the final lens of an SEM. The study shows that such a voltage contrast detector can be designed to combine a high spatial resolution with a large field of view: voltage measurements using sub-micron probe-sizes can be maintained over a 6 mm by 6 mm square region. The detector is also predicted to require 16 to 20 times less electrons to attain the same voltage resolation perfomance as conventional retarding-field type voltage contrast detectors. The new detector is thus expected to speed up data-acquisition times by a factor of 16 to 20.
Fabrication of Ballistic Quantum Wires and Their Transport Properties
Authors: Takagaki Yukihiko , Wakaya Fujio , Takaoka Sadao , Gamo Kenji , Murase Kazuo , Namba Susumu
Published: February 2005

Quantum wires with width less than the elastic mean free path and comparable to the Fermi wavelength are fabricated using high resolution electron beam lithography and ion beam etching. The low temperature magnetotransport properties of the quasi-ballistic channels reveal novel phenomena resulting from the ballistic motion of electrons. We propose new side-gate transistors. The two dimensional electron gas remaining at both sides of the channel is utilized to narrow the conduction width. This technique may open the way to control electrostatically an Aharonov-Bohm phase shift in the GaAs-AlGaAs loop.
Wet Chemical Etching for Ultrafine Periodic Structure: Rectangular InP Corrugations of 70 nm Pitch and 100 nm Depth
Authors: Inamura Etsuko , Miyamoto Yasuyuki , Tamura Shigeo , Takasugi Teruhisa , Furuya Kazuhito
Published: February 2005

Rectangular corrugations of 70 nm pitch and 100 nm depth were formed on InP using electron beam lithography and two-step wet chemical etching. In electron beam lithography, line distributions were measured to estimate the narrowest possible period, and a fine periodic resist pattern with a 50 nm period was formed. It is pointed out that two-step wet chemical etching with a thin epitaxial mask has the advantage of suppressing the undercut etching because of good adhesion of the epitaxial mask. This etching method was applied to InP etching by HCl utilizing the material-selective and anisotropic properties. Compositions of etchant were optimized to overcome the deformation of mesas in the nanometer range.
Resonant Tunneling in Double-Barrier Structures with Trapezoidal Potential Profiles
Authors: Inaba Hirokazu , Kurosawa Kou , Okuda Masahiro
Published: February 2005

Transmission coefficients and current-voltage characteristics have been calculated for double-barrier diodes with trapezoidal potential profiles. The potential profiles have been taken up as a model for structures in which the flat interfaces have been disturbed through roughened surfaces and interdiffusion of the constituent atoms. The time-independent one-dimensional Schrödinger's equation has been numerically solved using Airy functions. Studying the effects of the slope widths on the diode characteristics for a particular case of the AlAs/GaAs/AlAs double-barrier structure having the barrier width of 23 Å and the well width of 50 Å, we have shown that a slope region less than 6 Å does not significantly change the characteristics.
Crystallization Induced by Laser Irradiation in Ba-Y-Cu-O Superconducting Films Prepared by Laser Ablation
Authors: Otsubo Shigeru , Minamikawat Toshiharu , Yonezawa Yasuto , Maeda Toshihiro , Morimoto Akiharu , Shimizu Tatsuo
Published: February 2005

Ba2YCu3O
x
superconducting films were prepared by laser ablation with some newly developed laser processing techniques. First, we revealed that a rapid postannealing by laser irradiation converts an amorphous film to a crystallized superconducting one. Second, we tried the in situ preparation without a high-temperature postannealing. To reduce the substrate temperatures T
s for the film preparation, we examined the effect of the laser irradiation on the growing film surface. We found that in situ excimer laser irradiation of the growing film surface improves the superconducting properties and the surface morphology of the films prepared at a relatively low T
s. This improvement is brought about mainly by the enhancement of the film crystallization, rather than by providing additional oxygen atoms to the film.
Electron Density Measurements in UV-Preionized XeCl and CO2 Laser Gas Mixtures
Authors: Takagi Shigeyuki , Sato Saburo , Goto Tatsumi
Published: February 2005

A Langmuir probe technique has been used to measure electron densities and temperatures in UV-preionized XeCl excimer and CO2 laser gas mixtures in a laser tube. For this experiment, only pin electrodes (preionization sparks) were operated with no discharge between the main electrodes. The measured electron densities were about 108 cm-3 in both the excimer and CO2 laser gases, compared with 1010 cm-3 in pure He gas. The electron density was found to increase due to the proximity of the main electrodes. The coefficients of absorption for excimer and CO2 laser gas were obtained from the characteristics of the electron densities vs the distance from the UV source. Based on the absorption coefficient for XeCl, 0.9 cm-1 atm-1, we propose pin-electrode arrangements for spatially uniform preionization.
Comparison of Temporal Changes of Molecular Alignments in a Twisted Nematic with a Supertwisted Nematic Liquid Crystal
Authors: Yamashita Masafumi , Yukinari Toshiro , Tako Toshiharu
Published: February 2005

The lagging effect of LC molecular alignments was studied through conoscopic figures in both a twisted nematic liquid crystal (TN LC) and a supertwisted nematic (STN) LC. The time required for the effect to show in STN LC was shorter than the time in TN LC. The time difference depended on film structure and the applied voltage, but it did not depend on the duration after the voltage was applied. It was qualitatively expressed by an equation of alternating current circuit considering the inductance which represents the inertial force. It became clear that the energy required for a tilt angle of 90 degrees could be reduced by using a double-block-pulse method instead of the method of a continuously applied electric field.
Transmission Electron Microscopic Study on Electroless Plated Nickel-Molybdenum-Phosphorus Alloy Film
Authors: Osaka Tetsuya , Arai Katsuya , Yamazaki Yohtaro , Namikawa Tatsuru
Published: February 2005

In order to clarify the cause of the particular annealing behavior of resistivity of electroless Ni–Mo–P alloy films, the film structure after various heat treatment of a typical crystalline Ni-Mo-P alloy film by electroless plating was investigated by transmission electron microscopy (TEM). In the Ni–Mo–P film under as-plated conditions, the lattice image is observed, but it contains some regions having no lattice images due to amorphous conditions. The structure of small grains is kept even after heat treatment at 400°C, but the nonuniformity of Mo concentration is confirmed to exist in the film. After heat treatment at 700°C, the grains become larger and crystals with complete lattice images and no defects are observed. The results support the annealing effect of resistivity of the crystalline Ni–Mo–P alloy film, which shows a maximum upon heat treatment at around 400–500°C.
Fabrication of an Axisymmetric Wolter Type I Mirror with a Gold Deposited Reflecting Surface
Authors: Ninomiya Ken , Honda Kazunari , Aoki Sadao , Nishimatsu Shigeru , Suzuki Keizo
Published: February 2005

A small axisymmetric Wolter type I mirror was fabricated by a new film deposition method for an X-ray reflecting surface. In the film deposition, a gold (Au) electrode was inserted into a glass replica of the mirror. An Ar discharge was generated inside the replica at a discharge pressure of 44 Pa when a 40 kHz radio-frequency high voltage (-1.5–-3 kV) was supplied to the electrode. As a result of Au sputtering in the discharge, a 30 nm-thick Au film was deposited on the replica inner surface. The Au deposited surface had a surface roughness of 5–10 nm (peak to valley). A 300 µm-diameter X-ray beam with a reflectivity of 20% was obtained using a 6 mm-diameter MgKα X-ray (1253.6 eV) source. The present deposition method is suitable for producing metal deposited reflecting surfaces of axisymmetric X-ray mirrors.
Development of an Electrostatic Fogliquefier and Its Field Experiments
Authors: Uchiyama Haruo , Jyumonji Masanori
Published: February 2005

A new fogliquefier has been developed and demonstrated in a laboratory and an outdoor field. Fog charged by corona discharge is attracted toward the inversely polarized electrode and instantaneously liquefild. Outdoor experiments were successfully performed at a rice field with a newly invented electrostatic fogliquefier.
Spectroscopic Measurements and a New Monitor System of ECR Discharge Cleaning in the Tandem Mirror GAMMA 10
Authors: Okazaki Kiyohiko , Sakamotot Yuichi , Yamaguchi Naohiro , Inutake Masaaki , Nakashima Yousuke , Yatsu Kiyoshi , Miyoshi Shoichi
Published: February 2005

Spectroscopic measurements of a plasma of ECR discharge cleaning in GAMMA 10 device are described. It is shown that the spectrum of OH molecule is observed and that its intensity has a strong correlation with the partial pressure of the M=18 component. A new simple monitor system for OH band intensity has been constructed and shown to be effective.
Measurement of Piezoelectric Constants of a Crab Shell
Authors: Yamashiro Tomonobu
Published: February 2005

The piezoelectric constant d
14 and g
14 and dielectric constant ε
T of five layers separated from a crab shell were measured. The piezoelectric constant d
14 of the 5th (innermost) layer was 7×10-13 C/N, while those of the 3rd and 4th layers were both 12×10-13 C/N. The piezoelectricity of these three layers was found to be of the shear type. The other layers showed almost no piezoelectricity.
Shape Data Operations for VSB LB Data Conversion Using CAD Tools
Authors: Koyama Kiyomi , Ikenaga Osamu , Takigawa Tadahiro , Kobayashi Yuuichi , Sakamoto Shinji , Watanabe Susumu
Published: February 2005

For fast electron beam (EB) data conversion, an improved system of hierarchical process has been constructed. Several functions have been added to hierarchically perform shape data operations with increased efficiency. The added functions aim to cut redundant checks in oversizing, to reduce shape data expansion in array data handling and to speed cell overlap checks. These functions were implemented on a computer-aided design (CAD) system utilizing software tools available on it. The new system was applied to the variable shaped beam (VSB) EB data conversion and demonstrated to have better performance. A 16 Kbit SRAM design, conventionally degenerated near a flat level process, was successfully processed in a hierarchical manner, and performance gains of 1.6 to 3.1 were obtained.
Synchrotron Radiation Lithography for DFB Laser Gratings
Authors: Nishida Toshio , Nakao Masashi , Tamamura Toshiaki , Ozawa Akira , Saito Yasunao , Nishimura Kazuyoshi , Yoshihara Hideo
Published: February 2005

The synchrotron radiation lithography process of grating fabrication for distributed feedback (DFB) laser diodes is described. By finely controlling the field size in electron beam writing of the X-ray mask, the grating period can be arbitrarily varied with an accuracy of less than 0.1 nm . Gratings of 0.24-µm period with a λ/4 shift are formed in the Ta absorber X-ray mask, and transferred to the laser substrate by SR exposure. This process is successfully applied to the fabrication of 20-wave-length DFB-LD arrays.
Pressure-Controlled Wavelength Stabilization of a KrF Excimer Laser with Narrowed Bandwidth
Authors: Shimada Yasuhiro , Wani Koichi , Ogata Yoshiro
Published: February 2005

A spectrally narrowed and wavelength-stabilized KrF excimer laser has been developed. The spectral bandwidth of the laser output was narrowed to 3 pm FWHM using a set of two intracavity air-spaced etalons. An air pressure control system for providing automatic feedback to the intracavity etalons is described. The center wavelength was stabilized to within ±0.5 pm under feedback control both in a continuous running mode and in an intermittent burst mode.
Particle Detection for Patterned Wafers Using Hybrid Optical-Digital Image Processing
Authors: Nakata Toshihiko , Akiyama Nobuyuki
Published: February 2005

A particle detection method for patterned wafers has been developed. This method achieves much better sensitivity by using hybrid optical-digital image processing. Optical image processing employs newly developed 45° diagonal illumination combined with spatial frequency filtering, to reveal the presence of particles with minimal loss of light energy. Digital image processing is characterized by a two-chip comparison procedure insensitive to positional mismatching between the two chips, and eliminates residual pattern information which could not be completely eliminated by optical image processing alone. This method is performed so as to detect 0.5 µm particles on patterned wafers.
Tunneling Structures Fabricated by Silicon Wafer Direct Bonding
Authors: Stengl R. , Ahn K.-Y. , Mii T. , Yang W.-S. , Gösele U.
Published: February 2005

Tunneling diodes with highly doped and abrupt pn-junctions, and p+nn+ diodes were fabricated by bonding 4 inch silicon wafers at room temperature. After low temperature annealing (300–800°C) the electrical properties of the bonding interface could be changed by applying high currents up to 500 A/cm2. For tunneling diodes stressed with high current densities negative resistance effects have been obtained. The p+nn+ diodes with bonded n+ and p+ emitters showed S-shaped current switching observed in p-n-I-M structures. It is shown that due to the presence of an oxide at the bonding interface the current is limited in bonded pn-junctions.
Defect Characterization of GaAs on Si Grown by MOCVD
Authors: Soga Tetsuo , Nozaki Shinji , Noto Nobuhiko , Nishikawa Hironobu , Jimbo Takashi , Umeno Masayoshi
Published: February 2005

Defects in GaAs grown on a Si substrate with various intermediate layers by metalorganic chemical vapor deposition were studied. In the two-step growth method, the EPD (etch pit density) and the X-ray FWHM (full width at half maximum) decrease with increasing growth temperature. The lowest EPD of GaAs grown at 800°C on Si by the two-step growth method is 3.6×107 cm-2. When an Al
x
Ga1-x
P intermediate layer is used, both the EPD and the X-ray FWHM of GaAs on Si decrease with increasing x and have minima at about x=0.5 because the growth mode of Al
x
Ga1-x
P changes from three-dimensional to two-dimensional. The EPD becomes smaller when GaP/GaAsP and GaAsP/GaAs SLS's are grown directly on GaP, and is about 2×107 cm-2. A further reduced EPD, 3×106 cm-2, was obtained by in-situ thermal-cycle annealing.
Platinum-Platinum Oxide Gate pH ISFET
Authors: Tsukada Keiji , Miyahara Yuji , Miyagi Hiroyuki
Published: February 2005

Platinum-platinum oxide gate ISFETs (ion sensitive field effect transistors) have been designed and fabricated for a stable pH microsensor. The platinum oxide layer, formed by a new fabrication process using an RF sputtering technique, was identified as PtO2 by X-ray photoelectron spectroscopy. The pH response of the platinum-platinum oxide gate ISFET was linear in the pH range between 1 and 10, and a sensitivity of 40.5±4.0 mV/pH was obtained. The ISFET developed had better stability than a conventional Si3N4 bare gate ISFET.
Modeling of Charge Conservation in Isolated Silicon Regions
Authors: Kircher R. , Bergner W.
Published: February 2005

A simple model for charge conservation in isolated silicon regions is presented, which allows to determine the exact value of the Fermi-potential at any bias condition in steady state from an integral boundary condition. The model is not restricted to a certain charge state of the isolated region. It has been implemented in a two-dimensional general purpose device simulator, and the sophisticated numerical algorithm shows excellent convergence properties even for extreme bias conditions and poor initial values of the electrostatic potential and the Fermi-potentials. The model and its algorithm are illustrated by two specific examples which allow to study the physics of isolated silicon films or regions and the electrical coupling to other active device regions.
Effect of Sn on the Superconductivity of the DyBa2Cu3O7-δ System
Authors: Wang C. , Chen L. T. , Chang H. L. , Chu M. L. , Hsu F. W. , Chen T. M. , Yang T. J. , Gou Y. S. , Uen T. M.
Published: February 2005

The tin-substituted superconducting system DyBa2Cu3-3x
Sn3x
O
y
was investigated from x=0.025 to x=0.4 by measurements of electrical resistivity and ac susceptibility, X-ray diffraction, and Mössbauer spectroscopy. It was found that the substitution of Cu by Sn does not affect the zero-resistance temperature until x≥0.25 and results in the presence of a second phase. An anomaly in the temperature dependence of the Mössbauer recoil-free fraction near 70 K was observed for the sample with nominal composition DyBa2Sn3O
y
.