bluuebunny/crossref_metadata_2025 huggingface dataset:
Behavior of Active and Inactive Boron in Si Produced by Vapor-Phase Doping during Subsequent Hydrogen Annealing
Authors: Kiyota Yukihiro , Nakamura Tohru , Muraki Kazuhiko , Niwayama Hideki , Inada Taroh
Published: October 2002

The behavior of active and inactive boron produced by vapor-phase doping during subsequent hydrogen annealing is investigated. In samples doped at 800° C, there is a great deal of inactive boron at the surface, which gives an exponential profile just after doping. For these samples, fast out-diffusion of inactive boron is observed during subsequent hydrogen annealing at 800° C. After 20 min of subsequent annealing, almost all of the inactive boron diffuses out and the sheet boron concentration becomes identical to the carrier concentration. The out-diffusion of inactive boron does not follow a Gaussian distribution. In samples doped at 900° C, almost complete activation is achieved just after doping. The diffusion of active boron during subsequent annealing can be described as Gaussian: the surface carrier concentration decreases in proportion to the square root of the annealing time. This behavior is not affected by the existence of inactive boron.
Influences of Dark Line Defects on Characteristics of AlGaAs/GaAs Quantum Well Lasers Grown on Si Substrates
Authors: Hasegawa Yoshiaki , Egawa Takashi , Jimbo Takashi , Umeno Masayoshi
Published: October 2002

We report the influences of dark line defects (DLD's) on characteristics of AlGaAs/GaAs quantum well lasers grown on Si substrates under continuous-wave aging operation. Electroluminescence topography revealed that rapid degradation of an AlGaAs/GaAs laser on Si was caused by the rapid growth of <100> DLD's. The generation of <100> DLD's causes the decrease of internal differential quantum efficiency (η i) due to the increased number of nonradiative recombination centers. It also causes decrease of the differential gain coefficient (β) and slow increase of driving current at the initial slow degradation stage. At the subsequent rapid degradation stage, rapid increase of driving current is caused by the drastic increase of internal loss (α i) and decrease of β due to the growth of the DLD's. It is also found that the DLD growth velocity depends more strongly on the injected current density than on the junction temperature.
Effect of Cracks on Stress Reduction in GaAs/Si Heterostructures
Authors: Nakajima Kazuo , Ochiai Shojiro
Published: October 2002

The longitudinal stress distribution in GaAs/Si heterostructure was calculated using improved shear lag analysis. In this analysis, it is assumed that each layer consists of many imaginary thin layers in order to calculate internal stress distributions over the entire the heterostructure. This method is applied to stress calculation in a GaAs/Si heterostructure whose GaAs layer has cracks, in order to determine the effect of cracks on the reduction of stress in the wafer. In the stress distribution in the Si layer close to the heterointerface, a sharp and deep valley of compressive stress appears near cracks. The stress between cracks is maximum in the Si and GaAs layers. The stress in the GaAs layer can be clearly reduced by introducing cracks regardless of wafer length, and it can be greatly reduced by shortening the distance between cracks. The reduction becomes marked for distance less than 100 µ m.
Chemical Structure of As-Stabilized Surface during GaAs Metalorganic Vapor Phase Epitaxy Studied by Surface Photo-Absorption
Authors: Kobayashi Yasuyuki , Uwai Kunihiko , Naoki Kobayashi Naoki Kobayashi
Published: October 2002

As-stabilized surface structures during GaAs metalorganic vapor phase epitaxy (MOVPE) are investigated by taking a difference in surface photo-absorption spectrum between two principal axes, which produces the surface anisotropic spectra mainly due to As dimers on the surface. We established the surface phase diagram as a function of substrate temperature and AsH3partial pressure. Below 630° C, independently of AsH3partial pressure, the surface isc(4×4)-like whose As dimers have a bond axis parallel to [110]. As the substrate temperature increases and the AsH3partial pressure decreases, the surface evolves to (2×4)γ-like which contains As dimers having a bond axis parallel to [1̄10]. At a substrate temperature of around 600° C, a phase diagram comparison between MOVPE and molecular beam epitaxy (MBE) shows that thec(4×4)-like surface is stable in MOVPE, while the (2×4) surface is stable in MBE. The characterization of step structure by atomic force microscopy shows that the difference of As structures has a significant effect on the step straightening mechanism.
Laser-Induced-Fluorescence Study of the SiH2 Density in RF SiH4 Plasmas with Xe, Ar, He, and H2 Dilution Gases
Authors: Kono Akihiro , Koike Naoki , Nomura Hideshi , Toshio Goto Toshio Goto
Published: October 2002

The silylene ( SiH2) density in a parallel-plate RF (13.56 MHz) discharge using monosilane ( SiH4) gas has been measured by using laser-induced fluorescence spectroscopy. The effect of Xe, Ar, He and H2 dilution gases on the SiH2 density was investigated at a total gas pressure of 40 mTorr. In all dilution cases, the SiH2 density was relatively insensitive to the SiH4 fraction (x) in the mixtures for x\gtrsim0.5; however, except in the case of H2 dilution, marked increase of the SiH2 density was observed with decreasing x for x\lesssim0.5. The production and loss mechanisms for SiH2 are discussed on the basis of the observed SiH2 density and supplementary optical emission measurements. The results indicate that, in highly diluted ( x\lesssim0.1)SiH4/Xe and SiH4/Ar mixtures, the production of SiH2 via energy transfer from excited Xe and Ar atoms to SiH4 is dominant over direct electron impact dissociation of SiH4.
Green Photoluminescence from \mbα-Phase ZnAl 2S 4
Authors: Tetsuya Kai Tetsuya Kai , Masakazu Kaifuku Masakazu Kaifuku , Igor Aksenov Igor Aksenov , Katsuaki Sato Katsuaki Sato
Published: October 2002

A bright green photoluminescence with a peak at 540 nm was observed at low temperature in the α-phase ZnAl2S4 ternary compound grown by heating ZnS, Al and S powders. The emission is interpreted as arising from donor-acceptor(DA)-pair recombination. At room temperature the green emission is dominated by two weak emission bands in the infrared spectral region.
Effect of Annealing on Interface Structure and Giant Magnetoresistance Oscillation in Co/Cu Multilayers
Authors: Nawate Masahiko , Inage Kenji , Imada Ryuji , Itogawa Michiyuki , Shigeo Honda Shigeo Honda
Published: October 2002

The effect of annealing on the oscillatory behavior of giant magnetoresistance (GMR) is studied in Co/Cu multilayers. Annealing at 200° C in vacuum reduces the height of the 1st peak of GMR oscillation significantly. However, the degradation of interface measured by X-ray diffraction is not large compared with the change in GMR.
Microscopic change of the interface state causes ferromagnetic interlayer coupling between adjacent Co layers and diminishes the 1st GMR peak. The 2nd GMR peak, on the other hand, is not so sensitive to the degradation of the interface.
Measurement and Control of Optically Induced Rotation of Anisotropic Shaped Particles
Authors: Yamamoto Akihiro , Ichirou Yamaguchi Ichirou Yamaguchi
Published: October 2002

When a particle of anisotropic shape is trapped by a laser beam, it generally begins to rotate around itself. This self-rotation is caused by the torque resulting from total forces acting on the particle surface. We have measured the rotation rate rapidly and automatically from temporal variation of light scattered from the rotating particle. The rotation rate, which could be measured up to 2200 rpm, has been shown to be linearly dependent on the power of the trapping beam. We controlled the rotation rate by a feedback loop connecting the measured rotation rate and the trapping beam power.
Preparation of Magneto-Optic Single-Mode Buried Channel Waveguides of Lanthanum- and Gallium-Substituted Yttrium Iron Garnet
Authors: Sugimoto Naoto , Katoh Yujiro , Tate Akiyuki , Shintaku Toshihiro , Terui Hiroshi , Atushi Shibukawa Atushi Shibukawa
Published: October 2002

Magneto-optic single-mode buried channel waveguides are prepared using lanthanum- and gallium-substituted yttrium iron garnet [(La, Ga):YIG] liquid-phase-epitaxial film. The film growth conditions, film properties and the core ridge fabrication method are described. The refractive index of the film is controlled with the film growth temperature. The core ridge size is well controlled using ion beam etching. The obtained waveguides provide low loss coupling with a silica-based waveguide, which is a platform waveguide for a hybrid optical integrated circuit. Magneto-optic mode conversion is observed in a weak applied magnetic field, and the conversion efficiency R
max and isolation ratio are evaluated. The relationship between R
max and the stress-induced birefringence is discussed.
Pyrazoline Dimers for Hole Transport Materials in Organic Electroluminescent Devices
Authors: Sano Takeshi , Fujii Takanori , Nishio Yoshitaka , Hamada Yuji , Shibata Kenichi , Kazuhiko Kuroki Kazuhiko Kuroki
Published: October 2002

Dimer structures of pyrazoline derivatives were synthesized in order to obtain stable films and applied to electroluminescent (EL) devices as hole transport material. A device structure of [indium-tin-oxide (ITO)/hole transport layer (HTL)/emitting layer (EML)/MgIn] was employed. When pyrazoline dimer (PYR-D3) and tris(8-hydroxyquinolinate)aluminum ( Alq3) were used as HTL and EML, respectively, the EL device showed a maximum luminance of 12400 cd/m2 at 11 V and a maximum luminous efficiency of 1.5 lm/W at 250 cd/m2. This showed that pyrazoline dimers functioned well as hole transport layers.
Evaluation of Optical Glasses for Low-Loss Fibers: Optical Attenuation and Fiber Drawing Ability
Authors: Todoroki Shin-ichi , Shigeki Sakaguchi Shigeki Sakaguchi , Kiyomasa Sugii Kiyomasa Sugii
Published: October 2002

Optical attenuation of commercial optical glasses with low refractive indices is evaluated on the basis of the measurements for light scattering and infrared absorption. Furthermore, these glasses are drawn into fibers to examine the stability against crystallization in the fiber drawing process. All glasses exhibit light scattering intensity higher than that of silica glass. Fluorophosphate glasses are crystallized during fiber drawing. The present evaluation reveals that silicate glass, C7, is suited for low-loss fibers. The intrinsic minimum attenuation is predicted to be 0.8 dB/km at 1.2 µm, which is somewhat larger than that of silica glass. In addition, the estimations for density and concentration fluctuations indicate that concentration fluctuation dominates the light scattering in multicomponent optical glass.
Property of Radiation-Induced Defects in Germanium Single Crystals
Authors: Fukuoka Noboru , Honda Makoto , Nishioka Yoko , Atobe Kozo , Tokuo Matsukawa Tokuo Matsukawa
Published: October 2002

To study the property of defects produced in high-purity and p-type germanium single crystals by thermal neutron, fast neutron or electron irradiation, annealing experiments on irradiated samples were performed with electrical measurements and a deep-level transient spectroscopy technique. The annealing behavior of defects produced by the recoil energy of (n, γ) reaction in a high-purity sample irradiated with thermal neutrons indicates that interstitial arsenic atoms and interstitial gallium atoms are restored to lattice sites during annealing in the temperature range from 180° C to 240° C and that from 260° C to 340° C, respectively. The defects produced by neutron irradiation were annihilated by annealing for 20 min at 380° C. Two hole traps located at E
v+0.32 eV and E
v+0.53 eV were formed in a high-purity crystal by electron irradiation.
Nitriding of Evaporated-Ti Thin Films by Ion Implantation
Authors: Kasukabe Yoshitaka , Ootubo Junichi , Nagata Shinji , Kishimoto Mokuyoshi , Fujino Yutaka , Yamaguchi Sadae , Yukio Yamada Yukio Yamada
Published: October 2002

Nitrogen ions ( N2
+) with 62 keV have been implanted into 100-nm-thick Ti films evaporated on thermally cleaned NaCl substrates. Unimplanted and N-implanted Ti films have been examined by transmission electron microscopy, Rutherford backscattering spectrometry and elastic recoil detection analysis. The analysis has provided evidence that N-implantation results in the epitaxial formation of NaCl-type TiN
y
and simultaneously induces the release of H from evaporated-Ti films containing TiH
x
. The nitriding of evaporated-Ti films is mainly divided into two elemental processes. One is accompanied by the hcp-fcc transformation and the other is not. The formation mechanism for TiN
y
is discussed.
Heteroepitaxial TiN Film Growth on Si(111) by Low Energy Reactive Ion Beam Epitaxy
Authors: Sano Kenya , Oose Michihiro , Takashi Kawakubo Takashi Kawakubo
Published: October 2002

Epitaxial TiN(111) films were grown on Si(111) substrates by low energy reactive ion beam deposition using N2 ion beam irradiation and Ti evaporation. TiN epitaxial film formation was investigated as a function of the substrate temperature (T
s) and the kinetic energy of the ion beam (E
b). Using X-ray diffraction (XRD) and in-situ reflection high-energy electron diffraction (RHEED), the epitaxial relationship was found to be TiN(111)||
Si(111), TiN<110>||
Si<110> above substrate temperature of 400° C. Cross-sectional bright-field transmission electron microscope (TEM) observation has shown that the interface is quite flat and sharp and that four TiN lattice spacings match three spacings of the Si lattice. A lowest resistivity value of 18 µΩ· cm (T
s=600° C, E
b=100 eV) was obtained.
Electric Responses of Odor Sensor Using Vapor-Deposited Copper-Phthalocyanine Film
Authors: Saito Minoru , Koyano Takeshi , Miyamoto Yasuo , Katsuaki Kaifu Katsuaki Kaifu
Published: October 2002

We investigated electric responses of a sensor using a copper-phthalocyanine film to various odorants. The film was deposited on a substrate with a pair of interdigital gold electrodes by vacuum evaporation. This sensor could detect with specificity odorants classified under the amine group and benzaldehyde by monitoring changes in electric resistance.
Temperature Dependence of Photothermal Divergence Signal of GaAs
Authors: Haraguchi Masanobu , Okamoto Hiroyuki , Nunotani Toshiki , Masuo Fukui Masuo Fukui
Published: October 2002

We measured the temperature dependence of the photothermal signal intensity for undoped and doped GaAs samples using the photothermal divergence method proposed by Saito et al. [Appl. Opt. 31 (1992) 2047]. The temperature dependence of signal intensity and cutoff frequency of the signal agreed with a theoretical prediction and enabled determination of the temperature dependence of the thermal conductivity of the samples.
Electron Holographic Interference Micrograph of a Single Magnetic-Domain Particle
Authors: Hirayama Tsukasa , Osakabe Nobuyuki , Ru Qingxin , Tanji Takayoshi , Akira Tonomura Akira Tonomura
Published: October 2002

Electron interference micrographs of a single magnetic-domain particle of barium ferrite are obtained experimentally and theoretically. In the experiment, a hologram of the particle with size about 1 µ m is recorded on film and the phase distribution of the object electron wave is reconstructed digitally by the Fourier transform method. In the theoretical calculation, the phase distribution is obtained by integrating the vector potential around the particle along the electron path, assuming that the particle is spherical and is in the single-domain state. The above two phase distributions are converted to interference micrographs where magnetic flux lines are observed, and compared with each other. The theoretically calculated result agrees well with the experimental one, proving that the particle is in the single-domain state.
Grating-Coupled Surface Plasmon for Measuring the Refractive Index of a Liquid Sample
Authors: Kano Hiroshi , Satoshi Kawata Satoshi Kawata
Published: October 2002

We propose a technique for measuring the refractive index of a liquid sample through the use of a grating-coupled surface plasmon. The surface plasmon is excited on the metallic grating by an incident optical beam. The liquid sample is placed in contact with the grating, and its refractive index is determined from the dependence of the plasmon excitation angle on the refractive index value. The effects of the grating groove pitch and depth on the measured value of the refractive index are analyzed using the mode-matching method. Experimental results are presented for water and ethanol samples.
New Charge Density Modulations in Confined Regions of Reconstructed Pt(100) Surface
Authors: Chia-Seng Chang Chia-Seng Chang , Wei Bin Su Wei Bin Su , Tien T. Tsong Tien T. Tsong
Published: October 2002

In the narrow regions confined by lattice steps or domain boundaries of the reconstructed Pt(100) surface, new periodic structures have been observed with the scanning tunneling microscopy. These structures correlate well, or are commensurate, with the atomic structure of the original reconstructed surface. They can also be shown to arise from a redistribution of the electronic density of states. Thus, these charge density waves are produced by strongly coupled electrons and phonons, but are enhanced by the quantum confinement effect of the barriers. Such structures can also be induced near a domain boundary due to the strain of artificially created nanometer-size holes. Therefore we believe that coupling originates from the strain relief effect of the system reducing its strain and electronic energy.
High-Temperature Scanning Tunneling Microscopy (STM) Observation of Metastable Structures on Quenched Si(111) Surfaces
Authors: Tadatsugu Hoshino Tadatsugu Hoshino , Koichi Kokubun Koichi Kokubun , Keita Kumamoto Keita Kumamoto , Tetsuya Ishimaru Tetsuya Ishimaru , Iwao Ohdomari Iwao Ohdomari
Published: October 2002

High temperature scanning tunneling microscopy (STM) observation has been performed to investigate the energetic stability of metastable structures of Si(111) surfaces. Upon supercooling from 1100°C, 5×5 and 9×9 structures have been observed at 600°C, as well as the reconstructed 7×7 and disordered 1×1 areas. The 5×5 and 9×9 areas shrink to disappear as a consequence of the growth of 7×7 domains. The smaller domain size and the faster shrinking speed of the 9×9 structure indicate its lower stability compared to the 5×5 structure. The 11×11 and 13×13 DAS structures were occasionally observed at above 500°C, however, suggesting lower stability than the (2n+1)×(2n+1) DAS structures with smallern. The √3×√3 structures also appear at high-temperatures below 550°C, whereas the 2×2,c2×4, andc2×8 structures are observed only at room temperatures. Clear STM images of the √3×√3 structure can rarely be obtained at temperatures higher than 600°C, which is considered to be due to the thermally excited random motion of Si adatoms.
Investigations of Electronic Structures of Defects Introduced by Ar Ion Bombardments on MoS 2 by Scanning Tunneling Microscopy
Authors: Naohisa Sengoku Naohisa Sengoku , Keiichi Ogawa Keiichi Ogawa
Published: October 2002

We have investigated the defects introduced by Ar ion bombardment on cleaved MoS2 surface by scanning tunneling microscopy (STM). The resultant defects have been observed at room temperature as dark regions typically 6–8 nm in diameter and their contrast is found to depend on the sample bias voltage (SB). The high-temperature STM observations at 600°C and 800°C show a reduction of the diameter to 2–4 nm. Based on these experimental results it is concluded that the S atom complex produced at the defect site is partially negatively ionized and a depletion region of conduction electrons is produced around it. The observed lateral extent of the depletion region is in good agreement with that calculated from the repulsive Coulomb potential due to the negatively charged complex. The calculated screening length, however, disagrees with the observed size of the dark region.
Role of Diffusion in Atomic Manipulation on Silicon by Scanning Tunneling Microscope
Authors: Dehuan Huang Dehuan Huang , Francois Grey Francois Grey , Masakazu Aono Masakazu Aono
Published: October 2002

Recent time-resolved experiments to modify the Si(111)7 × 7 surface on the atomic scale by scanning tunneling microscope reveal the role of field-assisted diffusion in this process. Here we summarize experimental evidence for field-assisted diffusion, and comment on its implications for atomic-scale engineering.
Recent Advances in Nanostructural Investigations and Modifications of Solid Surfaces by Scanning Probe Methods
Authors: Roland Wiesendanger Roland Wiesendanger
Published: October 2002

We have studied the nanometer-scale structure of bare substrates as well as of thin films by a variety of scanning probe methods and have correlated their nanostructural and nanophysical properties. Nanomechanical properties, e.g. of thin fullerene films, have been probed by scanning and lateral force microscopy. In particular, we have addressed the question of whether the spherically shaped C60 molecules can act as molecular-scale ball bearings, thereby exhibiting exceptional lubricating behavior. Nanomagnetic properties, e.g. of magnetite, have been studied by magnetic force microscopy (MFM) and spin-polarized scanning tunneling microscopy (SPSTM) from the micrometer scale down to the atomic level. The complementary nature of the information from MFM and SPSTM data is discussed. Nanoelectronic properties, e.g. of nitride-oxide-silicon (NOS) heterostructures, have been probed by scanning capacitance microscopy (SCM). Charge storage on a submicrometer scale in NOS heterostructures has been achieved by applying voltage pulses to the SCM tip. Finally, mechanical nanofabrication based on scanning force methods has been combined with conventional photolithography to obtain superconducting micro- and nanobridges with potential applications for superconducting nanoelectronic devices.
Effect of a Wire on the Electromagnetic Field in an Accelerating Cavity in the Coaxial-Wire Method
Authors: Takanori Toyomasu Takanori Toyomasu , Masaaki Izawa Masaaki Izawa , Yukihide Kamiya Yukihide Kamiya
Published: October 2002

A wire used in the coaxial-wire method to measure the characteristics of an accelerating cavity cannot be treated as a perturbator. Using a pill-box model, we analytically studied the electromagnetic field of a cavity with a wire. By this analysis, the effect of the wire on the resonance frequencies and Q-values of the cavity modes was clarified.
Dual Optical Levers for Atomic Force Microscopy
Authors: Hideki Kawakatsu Hideki Kawakatsu , Hannes Bleuler Hannes Bleuler , Takashi Saito Takashi Saito , Kougami Hiroshi Kougami Hiroshi
Published: October 2002

Development of micro machined cantilever and optical lever detection system has greatly facilitated the operation of atomic force microscopy. However, since the detection system measures only the deflection of the cantilever at one set point where the laser beam is focused, care must be taken in implementing force control or in interpreting the acquired data. In this paper, a dual optical lever detection system is introduced, which has the potential to resolve the deformation of the cantilever with multidegree of freedom and thus detect the position of the tip end point with resolution in the 10 pm order. The detection system proved to be effective in real-time monitoring of the behavior of the tip end point while scanning, and in explaining the scanning direction dependence of the acquired images.
Improvement of Kelvin Probe Force Microscope (KFM) System
Authors: Masatoshi Yasutake Masatoshi Yasutake
Published: October 2002

The Kelvin probe force microscope (KFM) is a useful tool that measures the surface potentials of both conducting and nonconducting materials. Recently, we have succeeded in improving the accuracy of potential measurements and increased the lateral resolution of the topographic image. Furthermore, Z axis servo control was improved to prevent the tip from coming into contact with the sample surface during scanning. Finally, the force gradient between the tip and the sample became steeper during the acquisition of the topographic image due to the inactivation of the modulation AC voltage. As a result, the potential resolution was less than 1 mV and the lateral resolution of the topographic image was improved to as high as 10 nm.
Chemical Approach to Nanofabrication: Modifications of Silicon Surfaces Patterned by Scanning Probe Anodization
Authors: Hiroyuki Sugimura Hiroyuki Sugimura , Nobuyuki Nakagiri Nobuyuki Nakagiri
Published: October 2002

Scanning probe microscope-induced local oxidation of a material surface with adsorbed water is a recent nanolithographic technology. We applied this technique to the nanoscale patterning of hydrogen-terminated silicon (Si-H) surfaces. Using the silicon oxide (SiO
x
) patterns as masking, examples of two types of pattern transfer method through area-selective chemical modification were demonstrated. Nanostructures of substrate Si or deposited gold were fabricated by wet chemical etching or electroless plating, respectively. These area selectivities arose from the difference in surface chemical reactivities between anodic SiO
x
and the surrounding Si-H. The oxidation chemistry is discussed in terms of anodization.
Back-Gating Effects on the Ga 0.1In 0.9P/InP/InGaAs High-Electron-Mobility Transistor
Authors: Lin Kun-Chuan , Chang Chun-Yen , Wu Chang-Cherng , Chen Horng-Dar , Chen Po-An , Chan Shih-Hsiung , Wu Janne-Wha , Chang E-Yi
Published: October 2002

Pseudomorphic GaInP/InP/InGaAs high electron mobility transistors (HEMT) with improved Schottky contacts and excellent electrical characteristics are grown by low-pressure metal-organic chemical vapor deposition (LP-MOCVD) on the InP substrate. These HEMTs with 1.7 µ m gate length have an average extrinsic transconductance of 225 mS/mm. The back-gating effects of this device structure are investigated for the first time in this structure. Both positive and negative bias are applied to the ohmic and Schottky back-gate contacts of these devices. The positive back-gate bias has no effect on the drain current or the output transconductances of these devices. The effect of the negative back-gate bias is very similar to that when negative bias is applied on the gate of these HEMTs.
Using Carbon Tetrachloride for Carbon Doping AlXGa1-XAs Grown by Metalorganic Chemical Vapor Deposition
Authors: Kohama Yoshitaka , Amano Chikara , Ohiso Yoshitaka , Takashi Kurokawa Takashi Kurokawa
Published: October 2002

Carbon doped Al

X

Ga1-
X

As was grown by metal organic chemical vapor deposition, using liquid carbon tetrachloride ( CCl4) as a p-type dopant, in the aluminum content range of 0 to 1 and growth temperature range 600 to 750° C. By using the diluting line for CCl4 a remarkably wide range of carrier concentration was obtained at 700° C: the third order range of 1×1016 to 2×1019 cm-3 for GaAs, and the second order range of 1×1017 to 5×1019 cm-3 for Al

X

Ga1-
X

As (X≤0.3). This indicates that carbon is a promising dopant for optoelectronic devices, such as lasers and detectors, that have a relatively high aluminum content and are grown at a higher growth temperature.
Optical Kerr Shutter Operable with Two Colinearly Polarized Beams and Utilizing Optical Rotatory Dispersion
Authors: Yokozawa Tadahiro , Matsumoto Yukio , Ashitaka Hidetomo , Yokoh Yasuhiko , Kuwata-Gonokami Makoto
Published: October 2002

We present a new scheme for an optical Kerr shutter operating with colinearly polarized pump and probe beams. When a nonlinear optical medium has optical rotatory dispersion (ORD), an optical Kerr shutter can be operated with two colinearly polarized beams, each having a different wavelength, because the pump polarization rotates relative to the probe polarization by ORD.
We estimate the efficiency of the ORD-Kerr shutter as a function of the rotational angle |Δη0| of the pump polarization relative to the probe polarization at the exit. The optimized |Δη0| is 66.5° and the signal intensity is 52% that of the conventional 45° Kerr shutter. This effect is experimentally demonstrated with solutions of optically active hexahelicene in CS2. The ORD-Kerr shutter signal is observed clearly and the signal intensity agrees with the calculated value.
Grating-Type Soft-Focus Filter for Improving Picture Quality of Liquid Crystal Displays
Authors: Fujisawa Katsuya , Masao Uetsuki Masao Uetsuki
Published: October 2002

A grating-type soft-focus filter was fabricated from a polymer film to transform the discontinuous picture of a liquid crystal display (LCD) into a continuous one. The soft-focus filter having a two-dimensional grating pattern with a sinusoidal cross section was photochemically formed on the film by proximity exposure through a photomask to ultraviolet light. When the LCD surface was covered with the soft-focus filter, the output light beam from the LCD was transformed into mainly nine beams as a result of (0, 0)- to (±1, ±1)-order diffractions with nearly equivalent intensities. Thereby, the picture discontinuity caused by the black matrix of the LCD was removed at a small expense of picture contrast.
Effects of Molecular Configurations on the Electrical Resistivity of Titanylphthalocyanine Thin Films
Authors: Kontani Tomonori , Muranoi Tetsuo , Kikuma Isao , Masui Masayoshi , Manabu Takeuchi Manabu Takeuchi
Published: October 2002

Carrier transport in titanylphthalocyanine (TiOPc) thin films was studied. TiOPc thin films of various crystallinities were prepared by vacuum evaporation at substrate temperature varying from -160 to 20° C. The film deposited at the substrate temperature of 20° C was polycrystalline, while the films deposited at lower substrate temperatures were amorphous. The resistivity perpendicular to the film plane was lower than that parallel to the film plane for the polycrystalline TiOPc films. The difference in the resistivities between perpendicular and parallel to the film plane decreased with a decrease in the film crystallinity. A molecular configuration model for the TiOPc thin films, which explains the anisotropy of the film resistivity, has been proposed. In order to validate the model, the carrier mobility in the TiOPc thin films was determined by time-of-flight measurements.
Wave Propagation in a Cylindrical Electron Cyclotron Resonance Plasma Chamber
Authors: Watanabe Iwao , Nishimura Hiroshi , Seitaro Matsuo Seitaro Matsuo
Published: October 2002

Wave propagation characteristics in a cylindrical chamber filled with uniform magnetized plasma are investigated numerically. When the magnetic field strength is greater than the electron cyclotron resonance (ECR) condition and the plasma frequency is higher than the wave frequency, not only right-hand (n=1) but also left-hand (n=-1) waves can propagate in the plasma chamber. Moreover, in a small-radius cylindrical chamber in which no modes or only one-mode wave can propagate, several modes waves can propagate when it is filled with a plasma having an anisotropic dielectric property. This tendency is probably due to the high conductivity of the magnetized plasma along the magnetic lines of force and to the dielectric property perpendicular to the lines. A peculiar mode of a right-hand (n=1) wave where the wave has a localized electric field at the plasma chamber surface is shown to occur.
Pulsed Laser Segregation of C60 from SiC
Authors: Koinuma Hideomi , Kim Min-Sung , Mamoru Yoshimoto Mamoru Yoshimoto
Published: October 2002

The mass spectrometry of pulsed-laser-deposited SiC films led us to the serendipitous discovery of C60 formation from sintered SiC solid due to pulsed KrF excimer laser ablation. Micro-Raman spectroscopy indicates a phase separation or compositional segregation into carbon-rich and Si-rich domains in the laser-deposited SiC films. From other metal carbides such as TiC and WC, C60 could also be produced in the same way. Thus, the pulsed excimer laser ablation is found to provide not only a new route to C60 but also a unique applicability for laser segregation or distillation of solid solutions.
Change of Inelastic Electron Tunneling Spectra of Organic Ultrathin Films by Voltage Pulses and Application to High-Density Recording Systems
Authors: Kudo Kazuhiro , Kuniyoshi Shigekazu , Kuniaki Tanaka Kuniaki Tanaka
Published: October 2002

Electron tunneling spectroscopy is important from both characterization and potential application viewpoints because it provides valuable information about the structure, orientation, and interactions of molecules in organic thin films. In particular, inelastic electron tunneling spectroscopy (IETS) using a scanning electron tunneling microscope reveals spatial and spectral information and is attractive as a high-density storage system. We describe the basic experimental results of changes in IETS patterns of organic monolayers induced by the voltage pulse, and the potential for application to high-density recording systems.
Photoelectrochemical Behaviors of Orientation-Controlled Thin Films of N,N′-Substituted Perylene-3,4:9,10-bis(dicarboximide)
Authors: Yanagi Hisao , Toda Yasuhiro , Noguchi Toru
Published: October 2002

Orientation-controlled thin films of N,N′-dimethylperylene- and N,N′-dibutylperylene-3,4:9,10-bis(dicarboximide) (Me-PTCDI and Bu-PTCDI) were prepared by vapor deposition onto a (001) cleaved surface of KCl. As the substrate temperature increased, the film structure changed from homogeneous-amorphous to inhomogeneous polycrystalline, then to epitaxially grown states. In the epitaxial films the molecular planes of Me-PTCDI are cofacially stacked parallel to the KCl substrate, whereas the Bu-PTCDI molecules oriented standing on the substrate. In a photoelectrochemical cell of indium tin oxide (ITO)/PTCDI/I3
-,I-/Pt, the homogeneous-amorphous films showed anodic photocurrents corresponding to their n-type semiconduction, whereas the polycrystalline and epitaxial films exhibited cathodic photoresponse due to iodine doping from the electrolyte solution. The photo-response of Bu-PTCDI was much lower than that of Me-PTCDI because of its high excited-state relaxation through fluorescence emission. The epitaxial film exhibited higher fluorescence emission than the polycrystalline films; however the epitaxial orientation, especially the parallel molecular stacking in the Me-PTCDI film, improved the photoelectrochemical efficiency.
Transient Photoelectric Responses in Organic Dye Langmuir-Blodgett Films
Authors: Kazuhiro Saito Kazuhiro Saito
Published: October 2002

Schottky-type photoelectric cells with a photoconductive layer made of organic dye Langmuir-Blodgett films were fabricated to investigate transient photoelectric responses. Three types of amphiphilic merocyanine derivatives with different substituents were employed to investigate the effect of aggregate formation, and a lightly substituted copper phthalocyanine derivative was employed to investigate the influence of alkyl chains on the responses. Each cell showed dispersive conduction. The results suggest that alkyl chains dominate the conduction process rather than aggregate formation. In addition, the possible application of the dispersive conduction to a fractal device is also discussed based on the experimental results.
Molecular-Scale Structures of Langmuir-Blodgett Films of Fatty Acids Observed by Atomic Force Microscopy
Authors: Nakagawa Yoshitsugu , Shimizu Aya , Sugiyama Naoyuki , Soeda Fusami , Akira Ishitani Akira Ishitani
Published: October 2002

Langmuir-Blodgett films of arachidic acid, barium arachidate, and a mixture of arachidic and behenic acids on a chemically flattened silicon substrate were observed by atomic force microscopy. The films were found to contact tightly with the substrate with a molecular slip at its steps. Lattice expansion due to barium ions was found on the barium arachidate film but not on the pure acid film. In addition, the 2×2 superlattice was found on the barium arachidate film. The superlattice structure may be caused by the formation of a hydrogen salt. Although no phase separation was found on the film made of a 9:1 mixture of the acids, the image of the expected molecular mixture has not been obtained so far.
Fabrication and Control of Two-Dimensional Crystalline Arrays of Protein Molecules
Authors: Nagayama Kuniaki , Takeda Shigeki , Endo Shigeru , Hideyuki Yoshimura Hideyuki Yoshimura
Published: October 2002

Fabrication methods to produce two-dimensional (2D) crystalline arrays of protein particles are reported. The key innovation in this fabrication is the spreading wetting process which uses the deformable substrate surface such as mercury surface (mercury method) or the air-water interface (subphase method), where protein solution spread to yield a thin liquid film. The thin film of protein solution leaves a monolayer state of protein molecules, for example 2D crystalline films, after the condensation of solute protein molecules by solvent removal by evaporation. The significance of the film fabrication lies in its active natures to harness the directional transport of particles driven by spreading or convective flow of the solution. Wild type and mutant ferritins were employed to spread their solution on substrates and align them to 2D arrays. The control of crystal forms, say hexagonal or tetragonal, has been pursued by changing the interprotein interaction through mutagenic replacements of amino acids at specific sites on the protein surface. With recombinant ferritins, conversion of crystal forms from hexagonal to oblique is observed by eliminating strong interaction of salt bridge kind between adjacent molecules in the crystal.
Dynamics of Granular Matter
Authors: Hayakawa Hisao , Nishimori Hiraku , Sasa Sin'ichi , Taguchi Y-h.
Published: October 2002

Granular matter is a typical example of a new topic in statistical (phenomenology) mechanics. Reconsidering granular matter from the physical point of view, several new aspects have been clarified, although granular matter has been studied by engineers for a long (period of) time. This review examines three topics: (1) pattern dynamics of sand ripples and dunes, (2) mathematical structure of a fluidized bed, and (3) convection and turbulence in a vibrating bed. Investigating these topics, it is found that the dynamics of granular matter exhibits many typical nonlinear phenomena, for example, formations of pattern, localized states, and turbulence.
Surface Contamination and Interface Abruptness on Si/SiGe Epitaxial Layers Related to Vacuum Quality of Chemical Vapor Deposition Reactors
Authors: Kiyohisa Fujinaga Kiyohisa Fujinaga
Published: October 2002

We investigated Ge contamination on the surface of Si/SiGe grown at 550° C by using two low-pressure chemical vapor deposition (LPCVD) reactors. Ge of one tenth of a monolayer or less was found to be contaminated on the surface for the high base-pressure reactor but no Ge for the low base-pressure reactor. This report shows that Ge contaminants on the as-grown surface can be removed by etching silicon oxide a few nm thick formed by acid or thermal oxidization. The Si/SiGe interface abruptness was greatly improved (the 1/e decay length, λ=0.61 nm) by LPCVD and not affected by the vacuum quality of the reactors. This is because the surface segregation of Ge is suppressed by H atoms terminating the surface that originate from the decomposition of Si2H6 and because the surface coverage of contaminants during growth is fairly less than that of the H.
This paper also demonstrates the good structural quality and crystalline quality of the quantum wells by transmission electron microscope (TEM) views and photoluminescence (PL) spectra.
Mössbauer Study of Single Crystal Bi2Sr3Fe2OxIsostructural with Bi2Sr2CaCu2O8+x
Authors: Sedykh Vera , Fujita Francisco E. , Smirnova Irina S. , Dubovitskii Aleksei V. , Narymbetov Bakhyt Zh. , Veniamin Sh. Shekhtman Veniamin Sh. Shekhtman
Published: October 2002

Single and polycrystalline samples of Bi2Sr2SrFe2Ox(232Fe) are synthesized and studied by Mössbauer spectroscopy. The structure of 232Fe is similar to that of 2212Cu except for a commensurate structure modulation arising from the replacements of the latter's Cu and Ca atoms by Fe and Sr. The Mössbauer spectra of the single crystals show two doublets with different parameters. Calculation of electric field gradient based upon the structure data confirms that the two doublets arise from two different Fe environments induced by the modulation wave: at the antinodes of the wave the oxygen coordination octahedrons are largely distorted and at the nodes far less. The experimental data are well explained accordingly. The Fe valence, isomer shift values, line widths and other Mössbauer data in comparison with the 2212Cu compound are also discussed.
Time-of-Flight Distributions of Si Atoms Ejected by KrF Laser Ablation of Si 3N 4
Authors: Yoshiki Nakata Yoshiki Nakata , Tatsuo Okada Tatsuo Okada , Mitsuo Maeda Mitsuo Maeda
Published: October 2002

The time-of-flight (TOF) distributions of nonemissive Si atoms ejected from a KrF laser-ablated Si3N4 ceramics target were measured by laser-induced fluorescence spectroscopy (LIF). Bimodal velocity distribution was observed and measured velocity at the peak of the distribution, which increased with fluence, reached 15 km/s at an ablation fluence of 3.0 J/cm2.
Electrooptic Properties of the Two-Stage Sintered Ba(La1/2Nb1/2)O3-Pb(Zr, Ti)O3 Ceramics
Authors: Ryu Ki Won , Lee Young Hie
Published: October 2002

Transparent Ba(La1/2Nb1/2)O3-Pb(Zr, Ti)O3 electrooptic ceramics (BLN-PZT) were fabricated by the two-stage sintering method, and the optical and electrooptic properties were investigated for various compositions. Refractive indices at 633 nm wavelength were about 2.4 for all compositions, and a high optical transmittance of more than 56% at 633 nm wavelength was observed for 9.0/65/35 composition. Linear and quadratic electrooptic coefficients, r
C and R, were 6.01×10-10 m/V and 10.535×10-16 m2/V2, respectively, for 9.0/50/50 and 9.0/55/45 compositions near the morphotropic phase boundary (MPB) region.
Characterization of Nickel Contamination in Float Zone and Czochralsky Silicon Wafers by Using Electrolytic Metal Tracer or Microwave Photoconductivity Decay Measurement
Authors: Walz Dieter , Joly Jean-Pierre , Falster Robert , Kamarinos Georges
Published: October 2002

The influence of nickel contamination on the free carrier recombination lifetime and on the electrolytic diodes reverse dark current of electrolytic metal tracer (ELYMAT) have been studied on both float zone (FZ) and Czochralsky Conductivity Decay (CZ) wafers. The reverse currents of the ELYMAT electrolytic cell's measured on moderately doped FZ wafers are clearly increasing with nickel concentration. The recombination lifetime in both FZ wafers, and CZ wafers after oxygen precipitation (Internal gettering) treatments is influenced by nickel contamination. In CZ wafers with oxygen precipitation nickel contamination causes a drop of the lifetime which is directly related to the oxygen precipitate density. The characteristic variation of recombination lifetime dominated by oxygen precipitates as a function of injection level changes significantly after intentional nickel contamination. All these results bring new insights for the fast identification of Ni contamination in device fabrication lines.
CuIn(SxSe 1-x) 2 Thin Films by Sulfurization
Authors: Tsuyoshi Ohashi Tsuyoshi Ohashi , Arnulf Jä Arnulf Jä , Tsutomu Miyazawa Tsutomu Miyazawa , Yoshio Hashimoto Yoshio Hashimoto , Kentaro Ito Kentaro Ito
Published: October 2002

Polycrystalline films of the quaternary alloy CuIn(SxSe1-x
)2 with a thickness of 1 to 3 µm have been synthesized by sulfurization of InSe/Cu precursors. The films have been characterized with respect to their composition and their optical and their electronic properties. X-ray diffraction measurements of the CuIn(SxSe1-x
)2 alloy films showed a shift of their (112) diffraction peaks corresponding to the S/(S+Se) composition ratio between 0.5 and 0.9. The optical transmission measurements revealed that the band gap of the alloy films shifts from 1.24 to 1.48 eV with increase of the composition ratio. All CuIn(SxSe1-x
)2 alloy films prepared by this method exhibited p-type conduction which was determined using a thermoprobe. Electrical transport properties were assessed by Hall measurements in the van der Pauw geometry.
Characterization of Metal/Ferroelectric/Insulator/Semiconductor Structure with CeO2 Buffer Layer
Authors: Hirai Tadahiko , Teramoto Kazuhiro , Nagashima Kazuhito , Koike Hiroshi , Yasuo Tarui Yasuo Tarui
Published: October 2002

A PbTiO3 ferroelectric film 813 Å thick was grown on a CeO2/Si(100) substrate by the digital chemical vapor deposition method. As the buffer layer between the perovskite PbTiO3 film and Si substrate, a CeO2 intermediate layer was grown on the Si(100) substrate using an ultrahigh vacuum (UHV) system. The density of surface states at the CeO2/Si(100) interface was estimated from the capacitance-vs-voltage (C-V) characteristics of Al/CeO2/Si(100) samples to be 8×1011/cm2 eV, and CeO2 films on Si(100) are therefore expected to be suitable as gate oxides for metal/ferroelectric/semiconductor-field-effect transistors (FETs). Experimental results derived from the C-V characteristics of metal/ferroelectric/insulator/semiconductor (MFIS)-structured samples show that the MFIS structure has ferroelectric switching properties, as demonstrated by the roughly 2.4 V threshold hysteresis in its C-V characteristics (“memory window”). Furthermore, the retention time of the MFIS sample was estimated to be 100,000 s by measuring the time dependence of capacitance at the voltage at the centuer of the memory window. Interfacial lines of the MFIS structure were clear in a transmission electron microscope image, and an amorphous CeO

x

layer and an amorphous SiO2 layer were seen between the Si substrate and PbTiO3 film. Secondary ion mass spectroscopy revealed that there was little diffusion of Si atoms into the PbTiO3 layer on the CeO2/Si substrate.
Scanning Tunneling Microscopy Investigations of Colloidal Silver: Surface Structure and Aggregation Behavior Induced by Chlorion
Authors: Fang Ye , Bai Chunli , Wei Ying , You-Qi Tang You-Qi Tang
Published: October 2002

The surface structure and aggregation behavior induced by NaCl of colloidal silver particles have been investigated by scanning tunneling microscopy (STM) and transmission electron microscopy (TEM). The TEM and STM results clearly revealed that the yellow silver colloid consists of nanometer-scale particles with sizes ranging from 5 to 15 nm in diameter. In the case of STM images of the Ag particles, we found that the Ag particles were firmly attached to the highly oriented pyrolitic graphite (HOPG) surfaces. Moreover, STM images with up to atomic resolution showed that the surfaces of the silver particles are not very flat, however, individual adatoms on the Ag surfaces can be distinguished. Furthermore, the change of the aggregation state of Ag colloids induced by the addition of NaCl, from primary dispersed grains to rodlike clusters, was also demonstrated by absorption spectroscopy, TEM and STM.
An Empirical Model for Planarization with Polymer Solutions
Authors: André Schiltz André Schiltz
Published: October 2002

In our search for a simple equation of use to technologists, an empirical model has been developed based on the calculation of a unique planarization constant specific to the polymer solution. The model enables calculation of the degree of planarization (DOP) over isolated lines as well as over periodic lines, and is observed to fit experimental data for various polymer solutions, with varying film thicknesses and over various sizes of isolated and periodic features.