bluuebunny/crossref_metadata_2025 huggingface dataset:
Performance and Stability of MOVPE-Grown Carbon-Doped InP/InGaAs HBT's Dehydrogenated by an Anneal after Emitter Mesa Formation
Authors: Kenji Kurishima Kenji Kurishima , Shoji Yamahata Shoji Yamahata , Hiroki Nakajima Hiroki Nakajima , Hiroshi Ito Hiroshi Ito , Yasunobu Ishii Yasunobu Ishii
Published: October 2002

A high-temperature anneal of 500°C for 5 min after emitter mesa formation is effective in completely reversing the hydrogen passivation of carbon acceptors in InP/InGaAs heterostructure bipolar transistors. Fabricated devices show a base hole concentration as high as 5 ×1019 cm-3 and a maximum oscillation frequency above 200 GHz. However, this technique simultaneously causes damage to the emitter mesa surface and degrades current gain. In order to avoid such undesirable effects, one has to carefully optimize the anneal conditions and/or select the optimum crystallographic orientation of the emitter mesa so as to increase the thermal stability of InP sidewalls. Preliminary bias-temperature stress tests were also performed to examine the stability of base-emitter junctions. The results show that the stability strongly depends on the emitter mesa orientation. Promising results are obtained from devices whose emitter orientation is parallel to the Primary Flat of (100)-oriented InP substrates.
Index-Guide GaInNAs Laser Diode for Optical Communications
Authors: Nakatsuka Shin'ichi , Kondow Masahiko , Kitatani Takeshi , Yazawa Yoshiaki , Okai Makoto
Published: October 2002

An AlGaAs/GaAs/GaInNAs single-quantum-well real-index-guide laser diode with a ridged waveguide structure was fabricated. A threshold current of 24 mA under room-temperature continuous-wave operation was attained with this structure. Obtained device parameters show that this device shows promise for application in optical communication system.
InGaAs/GaAs Vertical-Cavity Surface Emitting Laser on GaAs (311)B Substrate Using Carbon Auto-Doping
Authors: Mizutani Akimasa , Hatori Nobuaki , Nishiyama Nobuhiko , Koyama Fumio , Iga Kenichi
Published: October 2002

We have realized a low threshold InGaAs/GaAs vertical-cavity surface emitting laser (VCSEL) grown on GaAs (311)B substrates by metalorganic chemical-vapor deposition. The lasers exhibited a threshold current of 16 mA and a threshold current density of 810 A/cm2 for a 50 µmφ circular active area device. We obtained low electric resistance of p-type DBRs on GaAs (311)B by using AlAs carbon auto-doping with a hole concentration of 2×1019 cm-3. We also demonstrated a stable polarization operation of (311)B grown VCSELs.
Integrated Twin-Guide Corner Reflector Lasers with Surface-Grating-Etching for Simple Mode Selectivity
Authors: Sung-Kwon Hong Sung-Kwon Hong , Young-Se Kwon Young-Se Kwon
Published: October 2002

We have fabricated an integrated twin-guide (ITG) InGaAs–GaAs 980 nm laser with a surface-grating-etching (SGE) structure for single mode selectivity. It is possible to design the ITG lasers so that only two propagation modes exist in the cavity. It is difficult to fabricate wavelength filters using conventional ITG structures, thus, we introduced SGE in ITG lasers for wavelength selectivity. The threshold gain modulation as a function of wavelength is possible, as a result of the coupling of two propagation modes in twin-guide by the incorporation of SGE. We demonstrate the principle and the possibility of single mode selectivity using a simple fabrication technology.
Very-High-Allowability of Incidental Optical Power for Polarization-Insensitive InGaAs/InAlAs Multiple Quantum Well Modulators Buried in Semi-Insulating InP
Authors: Wakita Koichi , Kotaka Isamu , Matsumoto Shin-ichi , Iga Ryuzo , Kondo Susumu , Noguchi Yoshio
Published: October 2002

Very-low insertion loss (<6 dB) and polarization-insensitive (TE/TM polarization difference loss <1.0 dB) strained InGaAs/InAlAs multiple quantum well (MQW) modulators with high-speed (3-dB bandwidth 18 GHz) and a high-saturation optical power level (16 dBm) have been fabricated and demonstrated. Allowability of incidental optical power for these modulators has been investigated using high-mesas and semi-insulating buried heterostructures (SIBHs). It is confirmed that the upper limit of allowability is determined by the product of absorbed photocurrent and applied voltage and the resulting SIBH is superior to that of high-mesa structures. The MQW layer thickness dependence of the allowability has also been investigated and it has been determined that the optical confinement factor has an important effect on the upper limit of this allowability.
GaN-Rich Side of GaNAs Grown by Gas Source Molecular Beam Epitaxy
Authors: Iwata Kakuya , Asahi Hajime , Asami Kumiko , Kuroiwa Reiko , Gonda Shun-ichi
Published: October 2002

A large variation in wavelength from the ultraviolet to longer than 2 µm could be achieved in the GaN-rich side of the GaN1-x
As
x
alloy due to the large bowing of bandgap energy. Layers of GaN1-x
As
x
are grown on (0001) sapphire substrates by electron cyclotron resonance molecular beam epitaxy (ECR-MBE) using an ion-removed ECR radical cell after the growth of GaN buffer layers. During the growth of GaN1-x
As
x
layers, a streaky reflection high-energy electron diffraction (RHEED) pattern was observed. The excitonic photoluminescence (PL) peak from the GaN-rich side of the GaN1-x
As
x
layer shows a large red shift as the As content changes. When an As content of up to x=0.009 is attained, a bandgap bowing parameter of 19.6 eV is experimentally obtained. Such a large value of the bowing parameter is promising for applications to optical devices operating over wide range of wavelength.
Light Emission before and during Prebreakdown on Polytetrafluoroethylene Surface with Metallized Electrodes under AC Voltage Application in Vacuum
Authors: Yuan-Shing Liu Yuan-Shing Liu , Takehiko Mizuno Takehiko Mizuno , Koichi Yasuoka Koichi Yasuoka , Shozo Ishii Shozo Ishii
Published: October 2002

Light emission before and during electrical breakdown from the surface of polytetrafluoroethylene (PTFE) with metallized electrodes has been investigated with ac electric field application along the polymer surface, using a photon counting method, in order to understand the initiation mechanism of the prebreakdown. Two distinct stages of light emission were observed depending on the applied voltage: a low-level stable light emission, electroluminescence (EL), before prebreakdown and an irregular intense light emission during prebreakdown. Before prebreakdown, charge injection from the electrode directly into the polymer surface layer results in EL emission and the formation of long-term electron space charges away from the electrode. The crucial factor of prebreakdown initiation is the strong modification of the local electric field near the electrode because of space charge formation in the surface layer before prebreakdown. The prebreakdown with intense light emission is initiated by detrapping the long-term trapped electrons toward the electrode via the vacuum and/or the surface layer in the positive half-cycle of ac voltage.
Circuit Simulators Aiming at Single-Electron Integration
Authors: Minoru Fujishima Minoru Fujishima , Shuhei Amakawa Shuhei Amakawa , Koichiro Hoh Koichiro Hoh
Published: October 2002

We have developed two types of single-electron simulators. One is for lower level circuit simulation, denoted as extended single-electron simulator (ESS) and the other is for higher level simulation, denoted as single electron transistor-simulation program with integrated circuit emphasis (SET-SPICE). ESS simulates small-scale arbitrary circuits with precision, performs efficient steady-state analysis besides conventional transient analysis, and visualizes probability distributions. SET-SPICE, on the other hand, simulates large-scale single-electron-transistor circuits with relatively large node capacitances at high speed and performs co-simulation of single electron transistor (SET) and complementary metal oxide semiconductor (CMOS) circuits.
In-Situ Scanning Tunneling Microscope Study of Formation Process of Ultrathin Si Layer by Molecular Beam Epitaxy on GaAs(001)-(2×4) Surface
Authors: Tsurumi Naohiro , Ishikawa Yasuhiko , Fukui Takashi , Hasegawa Hideki
Published: October 2002

In order to understand and to optimize Si interface control layer (Si ICL)-based passivation, the initial formation process of ultrathin Si layer by molecular beam epitaxy (MBE) on GaAs(001)-(2×4) surface at 300°C is studied in-situ by ultrahigh-vacuum (UHV) scanning tunneling microscopy (STM). Si atoms are found to fill the sites at the missing-dimer trenches of the GaAs (2×4) surface initially. As atoms from the background are also found to fill the As sites at the missing-dimer rows when residual As atoms exist in the MBE chamber after the growth of the GaAs layer. By these trench-filling processes, a (2×1) structure is formed. On the (2×1) structure, a disordered (1×2) overlayer is formed by additional Si supply. Further Si deposition leads to the formation of (2×1) and (3×1) overlayers above the disordered (1×2) structure.
Chemical Beam Epitaxy Growth and Characterization of GaNAs/GaAs
Authors: Takeuchi Kanji , Miyamoto Tomoyuki , Kageyama Takeo , Koyama Fumio , Iga Kenichi
Published: October 2002

A GaNAs layer has been grown on a GaAs substrate using chemical beam epitaxy (CBE) with a radio frequency (RF) radical nitrogen source for the first time. The nitrogen (N) composition was well-controlled by the N2 flow rate and was increased up to 2.7%, maintaining a good crystal quality. The maximum N composition was estimated to be 20% by a secondary ion mass spectroscopy (SIMS) measurement. The N composition estimated from both X-ray diffraction measurements and SIMS measurements were in good agreement. This shows that the N composition can simply be determined by X-ray diffraction measurements. The optical absorption measurement of the grown GaNAs was also carried out. The bandgap bowing parameter of GaNAs was found to be not a constant and varied between 15–23 eV for N<2.7%. An empirical expression of bandgap vs. composition was obtained for a N composition below 3%.
Photocurrent and Photoluminescence Affected by Γ-X Electron Transfer in Type-I GaAs/AlAs Superlattices
Authors: Mimura Hidenori , Hosoda Makoto , Ohtani Naoki , Yokoo Kuniyoshi
Published: October 2002

Dips in the photocurrent, and enhancement of both the photoluminescence intensity and lifetime, are observed at resonance voltages between the ground Γ state and the X states in GaAs/AlAs type-I superlattices. These experimental results suggest that electron transfer from the Γ to X states hinders the sweep-out of electrons.
Application of Fluorinated Amorphous Carbon Thin Films for Low Dielectric Constant Interlayer Dielectrics
Authors: Endo Kazuhiko , Tatsumi Toru , Matsubara Yoshihisa , Horiuchi Tadahiko
Published: October 2002

Fluorinated amorphous carbon thin films (a-C:F) for use as low-dielectric-constant interlayer dielectrics are deposited by helicon-wave plasma-enhanced chemical vapor deposition using fluorocarbon compounds as a source material. The a-C:F films can be grown from C4F8 at a high deposition rate (above 400 nm/min) and they are thermally stable up to 350°C. The addition of bias power to the substrate makes it possible to completely fill gaps in the wiring (space 0.35 µm, height 0.65 µm) with the a-C:F film. To protect the a-C:F film during further processing, a SiO2 film is deposited to add mechanical strength and resistance to the oxygen plasma used to remove resist materials. The adhesion between the a-C:F and SiO2 films is dramatically improved by inserting an adhesion promoter consisting of a-C:H and Si-rich SiO2. By using the a-C:F and SiO2 dielectrics and chemical mechanical polishing (CMP) process, globally planarized 3-level metallization is achieved. The a-C:F dielectric can reduce inter-line capacitance close to a half value as compared with the conventional SiO2 dielectrics.
Optical Absorption and Electron Spin Resonance Studies of Nonlinear Optical Crystal Li3VO4 Grown by the Floating-Zone Method
Authors: Murata Takuya , Fujimoto Akira , Miki Toshikatsu , Sakata Shin'ichi
Published: October 2002

The optically nonlinear Li3VO4 crystal grown by the floating-zone (FZ) method has been characterized by optical absorption and electron spin resonance (ESR) spectroscopy. The as-grown single crystals grown in gaseous argon exhibit a broad absorption extending from the uv to near-infrared light regions and an absorption band at about 3 eV. Postoxidation reduces the whole optical absorption and reveals an additional 1.9 eV band. ESR detects several signals associated with transition-metal ions in as-grown and reduced crystals, i.e., Fe3+, Mn2+ and Cr3+ ions. The Mn2+ and Cr3+ signals are absent in well-oxidized crystals, while the Fe3+ signal shows no significant change. The reduced crystals have three absorption bands associated with transition-metal impurities and oxygen vacancies. The diffuse reflectance spectra of transition-metal-doped Li3VO4 polycrystals were also measured to examine the effect of the presence of Fe3+, Mn2+ and Cr3+. The origin of the optical absorption in as-grown, oxidized and reduced Li3VO4 are discussed in terms of unexpectedly doped iron-group transition-metals and oxygen vacancies. The 3 eV and 1.9 eV absorption bands and the broad band extending from the uv to near-infrared regions are suppressed in the well-oxidized crystals subjected to repeated zone refining, indicating that multiple zone refining and complete oxidation are important in obtaining optical-quality Li3VO4 single crystals.
Double Optical Phase Transition of GeSbTe Thin Films Sandwiched between Two SiN Layers
Authors: Tominaga Junji , Nakano Takashi , Atoda Nobufumi
Published: October 2002

Crystallization mechanism of Ge2Sb2Te5 thin films sandwiched between SiN layers was optically investigated and double transition temperatures were observed in the case of Ge2Sb2Te5 film thickness of more than 20 nm. The activation energies were estimated by both Kissinger's and Johnson-Mehl-Avrami equations, and it was found that the reaction order was 2 for the first crystallization and 1 for the second transition. The lower transition temperature was strongly affected by the top SiN film thickness, and it was suggested that crystallization occurred at the interface between the recording film and the top SiN layer. The second crystallization occurred at the interface between the bottom SiN and the recording layers, which was not greatly affected by the thicknesses of both films.
Study on Crystallinity of Tin-Doped Indium Oxide Films Deposited by DC Magnetron Sputtering
Authors: Song Pung Keun , Shigesato Yuzo , Yasui Itaru , Ow-Yang Cleva W. , Paine David C.
Published: October 2002

Tin-doped indium oxide (ITO) films were deposited by dc magnetron sputtering using oxide (ITO) or alloy (IT) targets. The ITO films sputter-deposited using Ar at total pressure (P
tot) lower than 1.2 Pa showed polycrystalline structure, whereas entirely amorphous films were deposited at P
tot higher than 1.4 Pa, indicating that the crystallinity of the ITO films were heavily affected by P
tot. This was quantitatively explained in terms of the kinetic energy of sputtered particles reaching to the substrate surface, which decreased due to an increase in collision frequency between the sputtered particles and sputtering gas molecules. ITO films were also deposited using Xe or He as sputtering gases, where amorphous films were deposited at P
tot higher than 0.7 Pa (Xe) and 12 Pa (He), respectively. Based on a hard sphere collision model, the energy loss rates of the sputtered particles due to collision with sputtering gas molecules were estimated to be consistent with the experimental results for the case of using He, Ar or Xe gases.
Laser-Induced Bulk Damage of Various Types of Silica Glasses with Fundamental and Higher Harmonics of Nd:YAG Laser
Authors: Kuzuu Kunio Yoshida
Published: October 2002

The laser-induced damage threshold (LIDT) of various types of silica glass at 1064, 532, 355, and 266 nm was investigated. At 1064 nm, no difference in the LIDT was observed for all samples. In the range of 1064–355 nm, LIDTs of synthetic fused silica (SFS) were proportional to λ0.5, where λ is the wavelength. The LIDTs at 532 and 355 nm of fused quartz (FQ) and SFS containing 1000 ppm of Cl and no OH at 355 nm were slightly less than those of other SFSs. The mechanism of bulk damage at the 266 nm beam must be different from that at a longer wavelength, because the LIDT is considerably smaller than that of the value extrapolated from the λ0.5 dependence of SFS.
Impact of Surface Band Bending at the Rear Si–SiO2 Interface on Conversion Efficiency of Rear Locally-Contacted Silicon Solar Cells
Authors: Iwata Hideyuki , Ohzone Takashi
Published: October 2002

The dependence of the conversion efficiency of rear locally-contacted p-type silicon solar cells on surface band bending at the rear Si–SiO2 interface is studied for several substrate resistivities and rear oxide thicknesses through two-dimensional device simulations. Conventionally, the cell efficiency was thought to increase as the band bending induced by work function difference and positive oxide charge increases. However, this is not necessarily true. Under the assumption of asymmetrical capture cross sections (σn/σ
p
=102 at midgap) at the rear interface, the cell efficiency has a maximum value and then decreases gradually as the band bending increases. This is because a large number of generated electrons (minority carriers) are pulled into the rear surface and the greater part of the accumulated electrons flow into the rear p+-contact for large band bending.
Modeling on the Resistivity-Temperature Properties of (Pb0.6Sr0.4)TiO3 Materials Prepared by the Rapid Thermal Sintering Process
Authors: Hsiu-Fung Cheng Hsiu-Fung Cheng , Chen-Ti Hu Chen-Ti Hu , Yen-Yi Lin Yen-Yi Lin , I-Nan Lin I-Nan Lin
Published: October 2002

A core-shell microstructure is adopted to account for the unique resistivity-temperature (ρ–T) behavior of (Pb0.6Sr0.4)TiO3 materials prepared by the rapid thermal sintering (RTS) process. Instead of a V–shaped temperature coefficient of resistivity (VTCR) with critical temperature (T
′
c1) at around 220°C, commonly observed for the materials prepared by conventional sintering process, a ρ–T curve with single high T
c2\cong440°C is obtained. Moreover, the cooling rate after the RTS process markedly influences the ρ–T behavior. The apparent resistivity and the negative temperature coefficient of resistivity (NTCR) decrease as the cooling rate increases. The critical temperature (T
c2) for abrupt resistivity jump is insignificantly varied. These phenomena are ascribed to the modification of the thickness of the shell region due to the interdiffusion between the core and shell materials during the cooling stage. A simplified microstructural model is used to simulate the temperature dependence of resistivity and clearly explains the electrical behavior of these RTS samples.
Charge Trapping in Molecularly Doped Polymers
Authors: Borsenberger P. M. , Magin E. H. , Visser S. A.
Published: October 2002

Hole mobilities have been measured in di-p-tolylphenylamine doped poly(styrene) containing p-diethylaminobenzaldehyde diphenylhydrazone (DEH), an 0.32 eV trap. A DEH molar concentration of 10-5 decreases the mobility by a factor of two. For concentrations in excess of 10-5, the mobilities decrease with increasing concentration as approximately c
-1.4, the field and temperature dependencies remaining essentially unchanged. For concentrations in excess of 10-1, transport is dominated by trap-to-trap hopping and the mobility increases with increasing trap concentration. The results are discussed within the framework of the Hoesterey-Letson formalism and the recent simulations of Wolf et al.. and Borsenberger et al..
Characterization of Pb1- xLa xTiO3 Thin Films by the Radio Frequency Magnetron Sputtering Technique
Authors: Park Sang-Shik , Chae Su-Jin , Yoon Soon-Gil
Published: October 2002

Microstructures and electrical properties of polycrystalline and oriented (Pb1-x
Lax)TiO3 (PLT) thin films deposited by rf magnetron sputtering using a ceramic (Pb0.7La0.3)TiO3 target having 20 mol% excess PbO were investigated. The grain size of oriented films deposited on La0.5Sr0.5CoO3(LSCO)/MgO was larger than that of polycrystalline PLT films on LSCO/Pt/Ti/SiO2/Si substrates. The dielectric constant and the dissipation factor of polycrystalline films measured at 10 kHz were 340 and 0.014, respectively. On the other hand, the dielectric constant and the dissipation factor of oriented films were 810 and 0.08, respectively. Both the polycrystalline and the oriented PLT films deposited at 500°C exhibited a paraelectric properties. The leakage current densities of the polycrystalline and the oriented PLT films were about 8.0 × 10-8 and 2.5 × 10-7 A/cm2 at 10 kV/cm, respectively.
Scanning Tunneling Microscope Tip Current Excited by Modulated X-Rays
Authors: Tsuji Kouichi , Nagamura Toshihiko , Wagatsuma Kazuaki
Published: October 2002

We measured the current passing between a sample and a scanning tunneling microscope (STM) tip under conditions of X-ray irradiation. As shown in our previous reports, this STM tip current originated from electron emission on the sample surface. For high precision STM tip current measurement, we applied an X-ray modulation technique using an X-ray chopper and a lock-in amplifier. X-rays modulated by the X-ray chopper irradiated the sample surface of the STM, and the STM tip current was detected using the lock-in amplifier. The largest and most stable output from the lock-in amplifier was obtained under the experimental conditions of low modulation frequency (∼10 Hz), strong X-ray intensity, and high STM bias voltage. Compared with measuring the STM tip current directly without the modulation technique, the precision of this measurement is threefold better.
Estimation of Laser-Induced Breakdown Threshold of Microparticles in Water
Authors: Izumida Shin-ya , Onishi Kin-ya , Saito Mitsunori
Published: October 2002

Laser-induced breakdown of microparticles in ultrapure water was studied using a focused pulse laser of 532 nm wavelength. The transient acoustic signal generated by breakdown was detected on a nanosecond time scale using a fast-response polymer transducer. The temporal distribution of the acoustic pulses depends on not only the breakdown threshold of particles but also the spatial energy distribution of the laser beam around the focal point. The laser breakdown thresholds of various particles were estimated by analyzing the temporal distribution of the acoustic pulses. The breakdown threshold was higher in the order of silica, polystyrene, magnetite and gold particles.
A Simple Wire-Tension Measurement System
Authors: Kohzaburo Fujimoto Kohzaburo Fujimoto , Masashi Hirose Masashi Hirose , Kenji Inami Kenji Inami , Akimasa Ishikawa Akimasa Ishikawa , Iku Nagai Iku Nagai , Takayoshi Ohshima Takayoshi Ohshima
Published: October 2002

Using an oscilloscope as a differential amplifier, we built a simple and easily constructed system for wire-tension measurements by means of detecting the 3rd-harmonic signal of a mechanically vibrating wire, caused by an oscillating electric force.
Disk Mastering Process with an All-Solid-State Ultraviolet Laser
Authors: Kaneda Yushi , Kubota Shigeo , Yamatsu Hisayuki , Furuki Motohiro , Kurokawa Koutaroh , Kashiwagi Toshiyuki
Published: October 2002

The mastering process of the optical disk is demonstrated using an all-solid-state ultraviolet
laser for the first time. A 355-nm emission is obtained by the nonlinear frequency mixing
between 1064 nm and 532 nm using β-BaB2O4 crystal in an external resonator. The laser head
is efficient hence it does not require water cooling. A 30% improvement over the argon ion gas
lasers is obtained in the track pitch variation with the 0.74 µm-pitch-tracks. The absence of the
water flow for the cooling is the reason for the improvement. The optics designed at 351 nm
turned out to be compatible with the 355-nm laser source.
Modelling of Magnetic Multivalued Recording in Granular Materials
Authors: Hiroshi Mizuseki Hiroshi Mizuseki , Keiko Kikuchi Keiko Kikuchi , Kazumi Tanaka Kazumi Tanaka , Masahito Ishihara Masahito Ishihara , Yoshiyuki Kawazoe Yoshiyuki Kawazoe
Published: October 2002

A new method of magnetic recording using granular materials is proposed. In this study, hysteresis and remanence curves for granular materials are obtained by the Monte Carlo method to investigate micromagnetic behavior during the recording process. The relation between micromagnetics and ferromagnetic distribution is studied and the feasibility of the use of granular materials as a recording medium is clarified.
Short Wavelength Phase-Change Recording
Authors: Woudenberg Roel van
Published: October 2002

We discuss phase-change recording at blue wavelengths at densities
corresponding to that of a (read-only) digital versatile disk (DVD), and beyond.
We demonstrate in-groove recording on a 0.60-mm-thick, 120-mm-diameter disk
with a capacity of 6 Gbyte, achieved with a wavelength of 488 nm
and a numerical aperture of 0.60.
We discuss our results in relation with recently standardized rewritable
phase-change disks for red wavelength and the implications for systems
at even shorter wavelengths.
Accuracy Depending on Scanning Angle in Dynamic Spot Size Measurement Method for an Optical Disk Drive
Authors: Sugiura Akinobu , Kubo Takahiro , Ogawa Akihito , Kaneko Toru
Published: October 2002

The spot size has been measured by chopping the beam spot with
a knife edge on an optical disk. Tangential and radial spot sizes are
measured with different two angled knife edges: θ1-edge and θ2-edge. In
this paper, the errors in the measurement of spot sizes caused by the
error in the scanning angle and the scanning velocity are described. The
result of the theoretical analysis gives the best combinations of the
scanning angles which are θ1=0°, θ2=±45° with the radial direction. For
example, if the angle error of θ1 and θ2 obtained experimentally 0.64°,
then the calculated error of the radial spot size is 2.2%. The analyzed
error shows a good agreement with the experimental results. It was
analytically observed that the influence of the scanning velocity error on
the error of the measured spot sizes can be practically ignored using
this method.
One-Pass Variable Bit Rate MPEG2 Video Coding Method for Digital Video Recording
Authors: Satoshi Kondo Satoshi Kondo , Hideki Fukuda Hideki Fukuda
Published: October 2002

A real-time coding that performs, in one coding pass, a
variable bit rate coding that capitalizes on the MPEG2
video coding is proposed. In this method, the
relationship between quantization scale and generated bits
is modeled as a function to assign bit amounts. Based on
this bit amount assignment function, the quantization
scale is determined for each picture frames and coding is
performed with this quantization scale. To verify this
method, computer simulations were performed and MPEG2
real-time encoders were built to serve as the hardware of
this method. From the results, it was confirmed that:
1. this method's assignment of bit amounts is executed in
a similar fashion to that achieved in conventional 2-pass
variable bit rate coding; 2. image quality can greatly be
improved over the quality achieved in constant bit rate
coding; and 3. coding performance remains stable even over
extensive coding durations.
Narrow Pitch Tracking Using Optical Head for Recording with Atomic Force Microscopy
Authors: Nakamura Kimio , Koyanagi Hajime , Hosaka Sumio
Published: October 2002

In this paper we describe a narrow pitch tracking method for data storage
using an atomic force microscope (AFM) probe head. A track position of the
AFM head on a recording disk was controlled by an optical tracking method.
Narrowing of the track pitch was achieved by locating eight recording
tracks in one groove of the disk. These track positions were controlled by
eight phase tracking-error signals which were created from one groove of
the disk. In writing, we used the force modulation recording method which
forms written pits by applying force pulses between the AFM tip and the
polycarbonate recording disk. Using the recording system, we achieved 200 nm
pitch tracking control and readout from written pits as small as 40 nm
in diameter. A scanning electron micrograph of the written pits showed that the tracking accuracy was about 20 nm.
WSi2/Poly-Si Gate Etching Using a TiON Hard Mask
Authors: Tabara Suguru , Hibino Satoshi , Nakaya Hiroshi
Published: October 2002

We found that the WSi2 etch selectivity over TiON was high enough in
Cl2/O2 plasma to allow the use of TiON as an etching mask for
WSi2/polysilicon gate etching. The high content of Ti–O bonds in TiON films
is assumed to be the reason why TiON films can serve as etching masks.
Anisotropic etching down to a line width of 0.06 µm was achieved using
TiON thin films as etching masks. We can also avoid charging damage from
the electron shading effect by using thin TiON films as etching masks. In a
photolithographic context, we can expect to obtain improved critical
dimension controllability by adopting an organic antireflecting coating
(ARC)/TiON stacked layer as an antireflecting layer for WSi2/polysilicon
gate definition.
High Performance Etching Process for Organic Films using SO2/O2 Plasma
Authors: Ohkuni Mitsuhiro , Kugo Shunsuke , Sasaki Tomoyuki , Tateiwa Kenji , Nikoh Hideo , Matsuo Takahiro , Kubota Masafumi
Published: October 2002

The anisotropic etching of organic films such as anti reflective coating (ARC) and
resist for dry development using inductively coupled plasma (ICP) was studied. In
ARC etching, the controllability of critical dimension (CD) and the selectivity to
underlayers were investigated for O2 based gas chemistries by adding N2, He,
CHF3, Cl2, HBr and SO2. The SO2/O2 chemistry has the advantage of both the CD
controllability and the selectivity to underlayers. Field emission Auger electron
spectroscopy (FE-AES) analysis revealed that the SO2 gas is useful for sidewall
protection due to the sulfur deposition. In dry development etching, the controllability
of the etched profile was investigated. It was dicovered that the Vpp (peak to peak
voltage of RF bias) increases with increasing SO2 flow ratio to O2 so that a
recession occurs in the silylated layer due to high ion energy. A vertical profile was
obtained for a 0.13 µm pattern of resist and poly-Si optimizing SO2/O2 gas
chemistry.
Real-Time Monitoring and Control of Plasma Etching
Authors: Sarfaty Moshe , Baum Chris , Harper Michael , Hershkowitz Noah , Shohet Juda L.
Published: October 2002

Real-time etch rate of thin transparent films is determined
within seconds by an in-situ two-color laser interferometer.
The use of two colors improves the accuracy of the calculated rates,
provides an absolute measure of film thickness for endpoint prediction,
and differentiates between etching and deposition.
The tool state parameters, rf power to the antenna and the wafer stage,
gas pressure and flow rates, are computer controlled and monitored.
Real-time etch rate characterization is obtained by monitoring the etch
dependence on varying tool state parameters.
The density of the etch radicals, chlorine and fluorine, is obtained with
xenon and argon actinometry using optical emission and mass spectra.
An etch rate model, based on the input power to the wafer stage and
the relative density of the etch radicals, is used to develop
a model-based real-time control algorithm.
This algorithm has been used to control the etch rate of unpatterned
polysilicon and SiO2.
Production and Control of Low-Pressure Ar and CF4Plasmas Using Surface Waves
Authors: Nagatsu Masaaki , Ghanashev Ivan , Morita Shin , Sugai Hideo
Published: October 2002

Production and control of surface wave (SW) plasma at low pressures (∼10 mTorr) were studied using slot antenna excitation. High-density (>1011cm-3) planar plasmas (with a diameter of 22 cm) were produced in Ar or CF4gases using slot antenna excitation techniques. On increasing the microwave power or adjusting the tuner, we observed a mode jump from a low-density to an overdense (ωpe>ω) SW plasma mode. The observed mode jump is consistent with the results of a simplified theoretical eigenmode analysis under the assumption of uniform density distribution in the plasma (the two-interface model).
Investigation of Vacancy-Type Defects in P+-Implanted 6H-SiC Using Monoenergetic Positron Beams
Authors: Akira Uedono Akira Uedono , Takeshi Ohshima Takeshi Ohshima , Hisayoshi Itoh Hisayoshi Itoh , Ryoichi Suzuki Ryoichi Suzuki , Toshiyuki Ohdaira Toshiyuki Ohdaira , Shoichiro Tanigawa Shoichiro Tanigawa , Yasushi Aoki Yasushi Aoki , Masahito Yoshikawa Masahito Yoshikawa , Isamu Nashiyama Isamu Nashiyama , Tomohisa Mikado Tomohisa Mikado
Published: October 2002

Vacancy-type defects and their annealing properties for 200 keV P+-implanted 6H-SiC were studied using monoenergetic positron beams. For the specimen with a dose of 1×1013/cm2, the mean size of the open volume of defects was estimated to be close to that of divacancies. Based on the annealing behavior of theSparameter corresponding to the annihilation of positrons trapped by vacancy-type defects, the temperature range for the annealing of vacancy-type defects was divided into three stages. Annealing behavior in stages I (200–700°C) and II (700–1000°C) was identified as the agglomeration of defects due to migrations of monovacancies and vacancy complexes such as divacancies, respectively. In stage II, near the defect-free region, the agglomeration of defects was suppressed by recombination of vacancy-type defects and interstitials. Stage III (1000–1300°C) was assigned to be the formation of extended defects and their recovery processes. The annealing behavior of the amorphous region introduced by ion implantation was also discussed.
An Evaluation of High Acceleration Voltage Electron Beam Writing on X-Ray Masks
Authors: Kise Koji , Aya Sunao , Yabe Hideki , Kitamura Kaeko , Marumoto Kenji
Published: October 2002

High acceleration voltage electron beam (EB) writing on X-ray
masks was evaluated. Normalized dose latitudes of 100 keV for the
0.15 µm line and space (L&S), isolated lines and isolated space
patterns were 3.5, 2.7 and 7.6 times larger than those of 25 keV,
respectively. It was also found that the back-scattered electrons
extend over a range of 10 µm in 100 keV writing. The maximum mesh
size in the pattern area density method for proximity effect
correction was evaluated by Monte Carlo simulation. When a ±10%
pattern size error was permitted for a 0.1 µm line pattern, the 0.3 µm
mesh size in 50 keV writing was markedly improved to 5 µm at a
higher voltage of 100 keV. Reducing the beam size by half from 60 nm
(2σ) in 100 keV writing also increases the mesh size from 0.4 to
5 µm. Moreover, the fine W–Ti patterns of 0.06–0.14 µm were formed
using 100 keV Gaussian EB writing and electron cyclotron resonance
(ECR) etching systems, where good linearity and linewidth deviations
within 9 nm (3σ) were obtained.
Proposal for a Beat Oscillating Superconducting Quantum Interference Device
Authors: Furukawa Hisao , Tomiyama Shinji , Hatono Itsuo , Tamura Hiroyuki
Published: October 2002

We describe a new dc-superconducting quantum interference device (SQUID) circuit of the FM
type, which has a large coefficient for converting an applied magnetic flux into a frequency of
MHz band or a lower band. The circuit consists of a SQUID amplifier composed of two stages,
formed by a superconducting weak link and two dc-SQUID elements with nonhysteretic characteristics.
In the first stage, the weak link and dc-SQUID elements are connected in parallel and
operated by a common bias voltage. Since the respective elements oscillate with high frequencies
by the ac Josephson effect, the two frequencies interact with each other, so that, the first
stage generates a beat signal of a lower frequency. In the second stage, the other dc-SQUID
element with a intrinsic flux gain enhances the beat signal generated during the first stage. A
theoretical analysis of the circuit with computer simulation shows that the beat frequency is a
periodical function of the magnetic flux, and the SQUID amplifier with two stages can improve
the flux sensitivity.
Hydrogen Chloride Gas Monitoring at 1.74 µm with InGaAs/InGaAsP Strained Quantum Well Laser
Authors: Ubukata Akinori , Dong Jie , Masusaki Hiroshi , Satoh Takayuki , Matsumoto Koh
Published: October 2002

A distributed feedback laser with 1.9% compressive strain in the InGaAs/InGaAsP
quantum wells is demonstrated at 1.74 µm. The characteristic temperature was 66 K,
and the wavelength tuning rate was 0.016 nm/mA. A laser monitoring system of
hydrogen chloride gas and the laser shows a good linear calibration curve from 10 ppm
to 1% concentration of hydrogen chloride gas diluted in nitrogen. The detection limit of
HCl/N2 was 0.7 ppm for the present experimental setup.
Predischarge Models in Dielectric Liquids
Authors: Fofana Issouf , Beroual Abderrahmane
Published: October 2002

This study presents self-consistent models of streamer growth using an equivalent
electrical network, the only input data being the electrode geometry and the applied voltage
waveform. The growth of filamentary and bushlike discharge structures are simulated. The
initiation and the development of streamers are taken into account using field criteria. The
streamer instantaneous propagation velocity is obtained using a model based on energetic
considerations. In the case of filamentary streamers, each branch is assumed to be a
cylindrical channel represented by an R
C cell (R and C are, respectively, the resistance and
the capacitance associated with each branch). The hazardous discharge propagation is also
taken into account. In the case of bush-like structures, the envelope of streamers is
assumed to be approximately spherical. For given experimental conditions (such as applied
voltage and electrode geometry), we determine the streamer characteristics such as the
shape and amplitude of the streamer current, the electrical charge, the velocity, power and
energy injected in the gap. The developed models also enable the simulation of an image
converter working in streak or frame mode and the streamer trajectory plotted in real time.
An estimate of the pressure within bushlike streamer envelope is given. A good agreement
between computed and experimental results has been obtained.
Evaluation of Tilt Angles of Nematic Liquid Crystal Molecules on Polyimide Langmuir-Blodgett Films using the Attenuated Total Reflection Measurement Method
Authors: Baba Akira , Kaneko Futao , Shinbo Kazunari , Kato Keizo , Kobayashi Satoshi , Wakamatsu Takashi
Published: October 2002

The tilt angles of liquid crystal molecules, 5CB, have been
investigated in liquid crystal cells with rubbing-free aligning
layers of polyimide (PI) Langmuir-Blodgett (LB) films on
aluminum electrodes using the attenuated total reflection (ATR)
measurement method. The surface plasmon polariton (SPP)
and/or the guided wave excitation modes (GWEM) were
observed in the ATR curves of the liquid crystal cells when
various DC voltages were applied to the cell. The ATR properties
were evaluated from the SPP and the GWEM. The tilt angles of
the liquid crystal molecules were calculated by fitting the
theoretical ATR curves to the experimental ones using various
models of the liquid crystal layer structure. Furthermore, the
electric field intensities in the cell were calculated at several
incident angles in the ATR curves. The ATR measurement is very
useful for evaluating the alignment properties of liquid crystal
molecules in liquid crystal cells.
Sub 100 Nanosecond Pretilted Planar-to-Homeotropic Reorientation of Nematic Liquid Crystals under High Electric Field
Authors: E. Maclennan Hidehiko Takanashi , A. Clark Noel
Published: October 2002

The pretilted planar-to-homeotropic reorientation transition of nematic liquid crystals with positive dielectric anisotropy is achieved with a record fast risetime, as fast as 40 ns, by employing a customized electro-optic cell with small area and cell gap and with metal-coated electrodes and by applying electric fields up to several hundred volts/micron. The risetime dependence on the applied electric field is compared to a uniform director model which ignores surface and flow effects, based on Leslie-Ericksen continuum theory.
Piezoelectric Properties in α-, Incommensurate- and β-Phases of Quartz SiO2
Authors: Ochiai Tsutomu , Ohya Masaharu , Nishikawa Tetsuhiro , Sasaki Yukihiko , Abe Kohji , Shigenari Takeshi
Published: October 2002

Piezoelectric properties of quartz SiO2 were obtained using a
self-resonance method at 150–200 kHz over a range from room
temperature to 960°C, and in detail particularly in the
incommensurate phase. Their large elastic anomalies were observed.
Piezoelectricity was found to be preserved up to 960°C. The
“tridymite phase” was not detected.
Quasi-Medium Energy Ion Scattering Spectroscopy Observation of a Ge δ-doped Layer Fabricated by Hydrogen Mediated Epitaxy
Authors: Fuse Takashi , Kawamoto Kiyoshi , Shiizaki Takashi , Tazou Eisuke , Katayama Mitsuhiro , Oura Kenjiro
Published: October 2002

We have observed the behavior of Ge δ-doped layers in Si(001) by Quasi-medium
energy ion scattering spectroscopy (Q-MEIS). The δ-doped layers
were fabricated by hydrogen mediated epitaxy (HME) of Si. We found that,
in the δ-doped layers fabricated by HME, the surface segregation of Ge atoms
was reduced compared with that by conventional molecular beam epitaxy
(MBE). The Ge atoms, however, were widely spread in the growing film. We
assume that in the HME sample, hydrogen atoms are segregated to the top-most layer of the growth surface. Moreover, the Si buffer layer has a
comparatively good crystalline quality in the HME sample.
The Effect of Radiation Trapping in Gain for Ne-like Kr
Authors: Kim Dae-Soung , Kim Dong-Eon
Published: October 2002

The effect of radiation trapping in the atomic transitions of Ne-like Kr
plasma has been investigated theoretically. First, the relative sublevel
populations and gains for some specific 3s–3p transitions in the 27
levels of 2p
6 and 2p
5 3l configurations were calculated in the
range of electron density 1018–1023 cm-3 for the electron
temperature of 1 and 3 keV. Next, the influence of resonance radiation
trapping was approximated by introducing the effective rates for
some spontaneous emissions. Then, we recalculated the gains with
these modified rates. It is noted that the effect of radiation
trapping becomes significant at high electron densities and even
increases the gain for some lasin transitions
High-Repetition High-Duty Tokamak Discharge with Long Duration
Authors: Kobayashi Masahiro , Tashiro Kenji , Takamura Shuichi
Published: October 2002

A long duration of high-repetition high-duty discharge was successfully obtained up to 60 s in a small research toroidal device, current sustaining tokamak in Nagoya University (CSTN-III), by employing a compact pulse width modulation (PWM) invertor power supply. Slow variations of plasma parameters over the whole duration have been observed. The device has a useful potential for studying a long pulse discharge behaviour which is one of the critical issues for long or steady-state operation of magnetically confined fusion reactors.
A Contribution to the Development of Devices Transforming Optical Signals into Pneumatic Ones
Authors: Belforte Guido , Eula Gabriella
Published: October 2002

The development of ever more refined construction techniques and
scientific research has led to a renewed interest in physical
phenomena such as the photothermic effect, discovered last century.
Using these phenomena it has been possible to establish particular
steps for transforming an electric or electronic signal into a
pneumatic one. Once this conversion goes through an intermediate
phase where the signal becomes an optical one, the transformation
favours the transmission of the signal itself in hazardous
enviroments, with explosion risk or electromagnetic noise, and in this
case fibre optics can be used. This work sets out the results obtained
from a study carried out on an optopneumatic system based on the
photothermic effect. It is able to be piloted by an infrared Light
Emitting Diode and to be used, for the absence of electrical signals, in
every kind of enviroments.
Three Asymptotical Stability Theorems on Partial Region with Applications
Authors: Ge Zheng-Ming , Yu Jung-Kui , Chen Hsien-Keng
Published: October 2002

For a long time, all stability theorems are concerned with the stability of the zero solution of
the differential equations of disturbed motion on the whole region of the neighborhood of the
origin. But for various problems of dynamical systems, the stability is actually on partial region.
In other words, the traditional mathematical model is unmatched with the dynamical reality and
artificially sets too strict demand which is unnecessary. In order to fill the gap between the
traditional mathematical model and dynamical reality of various systems, three asymptotical
stability theorems on partial region are given and nine applications are presented.
Concentration of Ultrasonic-Velocity Invariant with Respect to Temperature Observed in Alcohol-Water Mixtures
Authors: Ozawa Atumi , Minamisawa Akiko
Published: October 2002

The pulse-echo overlap technique was used for measuring the
ultrasonic velocity in aqueous mixtures of methanol, ethanol and ethylene
glycol, changing the concentration and temperature. The purpose of the
study is to find a standard liquid whose velocity is independent of
temperature over a certain range. The velocity-invariant concentrations
were determined to be 12.8 wt%, 13.4 wt% and 22.0 wt% respectively, for the
above three mixtures, and the velocity was constant within 0.25% over the
temperature range of 35 to 65°C.
Effects of Bi2O3 Impurities in Ceramic ZnO on Photoacoustic Spectra and Current-Voltage Characteristics
Authors: Toyoda Taro , Shimamoto Satoshi
Published: October 2002

Photoacoustic (PA) spectroscopy is applied to study the optical absorption
of ceramic ZnO doped with 1 mol% Bi2O3 sintered at various temperatures (700–1100°C).
PA signal intensities plotted semilogarithmically reveal two individual regions
below 3.0 eV (A: 3.0–2.7 eV; B: 2.6–2.4 eV). The steepness factor (slope of
exponential optical absorption) obtained at region A decreases as the sintering
temperature increases, indicating an increase of Bi2O3 segregation at particle
surfaces and grain boundaries which might contribute to the interface states. The
steepness factor at region B increases rapidly as the sintering temperature
increases, indicating an occurrence of structural ordering by the Bi2O3 liquid phase
sintering effect. The varistor effect (highly nonohmic behavior in the
current-voltage characteristics) of ceramic ZnO doped with 1 mol% Bi2O3 is
correlated with the characterization obtained by the PA method.
A 3-Terminal AT-Cut Quartz Resonator with Shield Electrodes
Authors: Hirama Koichi , Aoyama Yuji , Naito Matsutaro , Yasuike Ryouichi , Yamazaki Kiyoshi , Hara Kouichi , Tanaka Yoshiaki , Nakamura Kiyoshi
Published: October 2002

In this paper a 3-terminal AT-cut quartz crystal resonator with shield electrodes
is proposed. The resonator has three terminals connected to three electrodes on the
quartz substrate. The 1st and 2nd terminals are connected to two main electrodes to
drive piezoelectrically, and the 3rd terminal is connected to a shield electrode which is
located just outside the main electrodes. The resonator with shield electrodes enables
the separation of the intrinsic capacitance from the stray capacitance which affects the
increase of effective resistance. Experimental data show fairly good agreement with
the intrinsic capacitance predicted by material constants of AT-cut quartz crystal. In
the application of oscillators, a common-emitter Colpitz oscillator circuit is proposed in
this paper instead of the widely used “common-corrector” one, because the stray
capacitance can be included in 2-phase inverting capacitors. Experimental data on
the resonator having a 2-divided electrode connected in a lattice with shield electrodes
is also presented.