bluuebunny/crossref_metadata_2025 huggingface dataset:
Persistent Photoconductivity (PPC) and Related Deep Metastable Center in MBE Grown p-Type ZnMgSSe
Authors: Tsutomu Yamaguchi Tsutomu Yamaguchi , Koshi Ando Koshi Ando , Keiichi Koizumi Keiichi Koizumi , Hideyuki Inozume Hideyuki Inozume , Hitoshi Ishikura Hitoshi Ishikura , Tomoki Abe Tomoki Abe , Hirofumi Kasada Hirofumi Kasada
Published: October 2002

A persistent-photoconductivity (PPC) effect and the related deep metastable centers have been investigated for a p-type ZnMgSSe quaternary system grown by molecular beam epitaxy. A low temperature photo-excitation revealed a marked PPC effect in nitrogen doped p-type Zn1-x
MgxSySe1-y
(0.05<x<0.18, 0.08<y<0.2) with an exponential temperature dependence of the carrier decay time constant: τ(T) = τ0 exp
(-490±50 meV/k
T). It is also confirmed that the low-temperature photo-excitation has caused a new deep metastable hole trap center with thermal hole activation energy of 650 meV. This metastable deep center is evidenced to be responsible for the observed PPC effect.
Effect of High Current Injection on the Blue Radiative Recombination in InGaN Single Quantum Well Light Emitting Diodes
Authors: Taguchi Tsunemasa , Kudo Hiromitsu , Yamada Yoichi
Published: October 2002

Radiative recombination properties of blue electroluminescence (EL) in the vicinity of 460 nm (about 2.7 eV) in an InGaN-based single quantum well light emitting diode (LED) have been investigated at 77 K under forward-bias pulsed high-current injection condition. The 460 nm blue emission band accompanying the LO-phonon sidebands was clearly observed at forward-biased steady-state currents, while its LO-phonon replicas were smeared out with increasing pulsed current. It is revealed that the forward-biased injection EL spectrum reflects the distribution function of hot electrons injected into the active layer. Emission spectral characteristics can be quantitatively explained by the drifted Maxwellian distribution function of electrons. The temperature of hot electrons was estimated to be about 400 K at current density of about 4500 A/cm2, which is much higher than the lattice temperature.
Reactive Ion Beam Etching and Overgrowth Process in the Fabrication of InGaN Inner Stripe Laser Diodes
Authors: Nunoue Shin-ya , Yamamoto Masahiro , Suzuki Mariko , Nozaki Chiharu , Nishio Joji , Sugiura Lisa , Onomura Masaaki , Itaya Kazuhiko , Ishikawa Masayuki
Published: October 2002

Dry etching and overgrowth process techniques have been developed for the fabrication of InGaN inner stripe laser diodes. The dry etch damage at the etched surface and the overgrown interface was estimated using X-ray photoelectron spectroscopy (XPS) and Rutherford backscattering spectrometry (RBS). As a result, the etch damage at the overgrown interface was shown to be repaired during the overgrowth. Groove stripes formed on the GaN layer by reactive ion beam etching (RIBE) were overgrown by GaN using metalorganic chemical vapor deposition (MOCVD). The morphology of the overgrown surface was observed by scanning electron microscopy (SEM). The grooves of widths less than 10 µm were buried completely at 1100°C and smooth, flat surfaces were obtained. We have fabricated the InGaN inner stripe (IS) lasers and reported on the first pulsed lasing operation of InGaN inner stripe lasers, fabricated by dry etching and overgrowth techniques.
ZnCdSe Quantum Wires Achieved by Strain-Induced Lateral Confinement
Authors: Vanelle Eric , Zhang Baoping , Yasuda Takashi , Wang Wenxin , Segawa Yusaburo , Itoh Tadashi , Brinkmann Dirk , Fishman Guy
Published: October 2002

Nanometer-scale ZnCdSe quantum wires have been achieved using a two step epitaxial growth process. First a (001) ZnCdSe/ZnSe multiple quantum well, strained to a thick ZnCdSe buffer layer, is grown on a GaAs substrate. Second, after the sample has been cleaved, a ZnCdSe/ZnSe single quantum well is grown along the [110] direction: modulation of the in-plane lattice constant in the multiple quantum well area laterally confines the carriers to one dimension. A strong polarisation of the photoluminescence of the quantum wires along the [110] direction is demonstrated.
Delta-Doping and the Possibility of Wire-like Incorporation of Si on GaAs Vicinal Surfaces in Metalorganic Vapor Phase Epitaxial Growth
Authors: Irisawa Tomoki , Motohisa Junichi , Akabori Masashi , Fukui Takashi
Published: October 2002

We have investigated the delta-doping of Si on GaAs vicinal surfaces on which self-organized multiatomic steps are formed during metalorganic vapor phase epitaxy (MOVPE) and the possibility of its wire-like selective incorporation into step edges to form doping quantum wires (DQWRs). We evaluated the electrical characteristics of delta-doped layers by Hall and C-V measurements and investigated their dependence on misorientation angles of GaAs vicinal substrates and doping time. The incorporation of Si is enhanced by steps. This effect is particularly important at the initial stage of delta-doping when the surface coverage of Si is not high. Our results also suggest that the doping density at multiatomic step regions is higher than at terrace regions. Therefore, it is expected that the selective wire-like incorporation of Si takes place at the step edges, and DQWRs can be realized under suitable growth conditions.
Cross-Sectional Potential Imaging of Compound Semiconductor Heterostructure by Kelvin Probe Force Microscopy
Authors: Usunami Takao , Arakawa Masashi , Kishimoto Shigeru , Mizutani Takashi , Kagawa Toshiaki , Iwamura Hidetoshi
Published: October 2002

The cross-sectional potential images of the GaAs/AlAs multiple quantum wells and InAlAs/InGaAs heterostructures have been successfully obtained by Kelvin probe force microscopy (KFM). It was shown that the smaller amplitude of the alternating voltage (V
ac) applied to detect the electrostatic force during the KFM measurements gave a better potential profile of the heterostructures. The spatial resolution of the present KFM was investigated by measuring the InAlAs/InGaAs layered structures with various thicknesses. The minimum thickness of the InAlAs layer distinguished by the KFM was 40 nm.
Vertical Quantum Confinement Effect on Optical Properties of Strain-Induced Quantum Dots Self-Formed in GaP/InP Short-Period Superlattices
Authors: Kim Seong-Jin , Asahi Hajime , Asami Kumiko , Takemoto Minori , Fudeta Mayuko , Gonda Shun-ichi
Published: October 2002

Optical properties of multilayer quantum dots (MQDs) self-formed in the GaP/InP short period superlattice (SL)/InGaP multilayer structures are investigated by changing the SL period (P) and InGaP barrier thickness (B). By decreasing P, photoluminescence (PL) peak energy is shifted toward higher energy due to the quantum size effect along the growth direction (vertical direction). PL linewidth broadening with temperature is reduced by decreasing P and B. This improvement is attributed to the reduction of potential distribution among quantum dots (QDs) and the enhancement of quantum confinement along the vertical direction, and to the enhancement of quantum confinement due to the vertical coupling effect between QDs. Stokes shift for the MQDs structure is observed to be small. Very small temperature variation of PL peak energy is observed in these MQDs, which originates from the existence of the multiaxial strains among the MQDs. Electroluminescence (EL) spectra show split peaks corresponding to the subbands of QDs on increasing injection current.
Size Quantization in InAs/GaAs Self-Assembled Quantum Dots Grown by Gas-Source Molecular Beam Epitaxy
Authors: Hong-Wen Ren Hong-Wen Ren , Kenichi Nishi Kenichi Nishi , Shigeo Sugou Shigeo Sugou , Yasuaki Masumoto Yasuaki Masumoto
Published: October 2002

The number of confined states in a self-assembled quantum dot (SAD) is determined by its size, shape and composition. By employing a gas-source molecular beam epitaxy, the average size of InAs self-assembled islands on the GaAs (001) surface was controlled by the InAs growth temperature. Meanwhile, indium segregation during the GaAs cap-layer growth was found to greatly modify the shape and actual composition of InAs/GaAs SADs resulting in a blue-shift in the ground state energy. By suppressing indium segregation, InAs/GaAs SADs 39 nm, 29 nm, 22 nm and 15 nm in their average diameters were obtained. The corresponding number of confined states observed was five, three, two and one, respectively. The energy separation between the states is about 50 meV, it does not change appreciably with decreasing the dot size but reduces with intensifying indium segregation.
Computer Simulation and Experimental Characterization of Single Electron Transistors Based on Schottky Wrap Gate Control of 2DEG
Authors: Satoh Yoshihiro , Kasai Seiya , Jinushi Kei-ichiroh , Hasegawa Hideki
Published: October 2002

Characteristics of GaAs-based single electron transistors (SETs) based on Schottky wrap gate (WPG) control of the two dimensional electron gas were studied. The two-gate and the newly proposed three-gate devices with different WPG sizes and channel widths were theoretically analyzed on a computer and experimentally fabricated and characterized. The computer simulation showed that dots and tunneling barriers could be formed in both the two- and the three-gate SETs. In the case of the two-gate SETs, both the dot size and the tunnel barriers were changed simultaneously by the gate voltage. On the other hand, in the case of the newly proposed three-gate SET, the dot size and the potential profile of the tunneling barrier could be separately controlled. Experimentally fabricated the two- and the three-gate SETs with narrow channel widths showed conductance oscillation characteristics which were consistent with the results of potential simulation.
Growth of Metastable Alloy InAsBi by Low-Pressure MOVPE
Authors: Okamoto Hiroshi , Oe Kunishige
Published: October 2002

Low-pressure metalorganic-vapor-phase epitaxy (MOVPE) growth properties of InAsBi, such as the relationship between the InBi composition and growth conditions, the growth conditions by which crystal with mirror-like surface can be obtained, and impurities in the InAsBi layer, are investigated. A mirror-like surface InAsBi layer with very high InBi content (3–4%) compared to the InBi solubility limit of 0.025% is obtained. On the other hand, surface morphologies with droplets, and with whiskers are observed when the growth conditions are not appropriate. In addition, the percentage of Bi substitutionally incorporated into InAs-zinc-blende lattice is evaluated for the first time. As for the impurities in the crystal, both the carbon and silicon in the InAsBi layer are below the detection limits, in spite of the low growth temperature of 365°C. Possible mechanisms dominating the alloy composition and the droplet formation are also discussed.
Anomalous Influence of a Small Amount of Impurities on the Shubnikov de Haas Oscillation Amplitude of Antimony
Authors: Satoh Naoki
Published: October 2002

Transverse magnetoresistance of pure and ionized impurity (5, 10, 30, 55 and 100 ppm tin) doped antimony single crystals was measured up to 15 T at 1.4 K. Compared with pure antimony, phase inversion of the Shubnikov de Haas (SdH) oscillation was observed in the doped samples. Moreover, a marked increase in the oscillation amplitude was found in doped antimony. Typically, the SdH oscillation amplitude of 30 ppm tin-doped antimony was almost twice that of pure antimony. Hall resistivity ρ
y
x
was also measured for the same doped sample in order to obtain the conductivity tensor component σ
x
x
. Phase inversion was explained by taking account of component σ
x
y
in magnetoresistivity ρ
x
x
. The large SdH oscillation amplitude in the tin-doped samples was attributed to the scattering by ionized impurities and to be a direct reflection of the state density at the Fermi level.
Formation and Characterization of Thin Oxide Layers on the Spatially Controlled Atomic-Step-Free Si(001) Surface
Authors: Ando Atsushi , Sakamoto Kunihiro , Miki Kazushi , Matsumoto Kazuhiko , Sakamoto Tsunenori
Published: October 2002

We have demonstrated the characterizations of the morphologies and local electrical properties of the SiO2/Si(001) structure which was formed by oxidation of the spatially controlled atomic-step-free Si(001) surface. The two-dimensional current images and current-voltage characteristics showed spatial differences in the local electrical properties while the morphologies at the SiO2 surface and the interface between SiO2 and Si(001) were uniform, with root-mean-square values of roughness, smaller than a monoatomic-step-height.
Electrical Transport Properties of GaSb Grown by Molecular Beam Epitaxy
Authors: Zhao G. Y. , Ebisu Hiroshi , Soga Tetsuo , Egawa Takashi , Jimbo Takashi , Umeno Masayoshi
Published: October 2002

The electrical transport property of GaSb are analyzed, both experimentally and theoretically. It is demonstrated that the mobility of GaSb is limited not only by high unintentionally doped impurity concentration, but also by high compensation ratio. Hall-effect measurement are made between 300 and 20 K on several undoped GaSb samples. It is found that the electrical properties of GaSb epilayers strong depend on growth temperature, and the impurity conductivity dominated the conduction mechanism over a large temperature range.
Ion-Beam-Milling of InGaAsP Alloys with N2/O2-Mixtures
Authors: Vollrath Gunther , Schlachetzki Andreas , Fiedler Friedrich
Published: October 2002

In this paper ion-beam-milling of GaAs, InP as well as of InGaAs and InGaAsP of different compositions lattice-matched to InP was investigated using nitrogen and nitrogen/oxygen mixtures. The influence of process parameters such as gas composition, kinetic energy of the ions and the angle of incidence of the ions was investigated in detail. The etch rates of different masking materials like titanium, photoresist and SiO2 are also given. Special attention was paid to the geometry and roughness of the mesa facets in view of their use as laser facets. For the first time the experimental results are compared to calculations based on the sputter theory of Sigmund. The calculated dependence of the etch rates on the kinetic energy of the ions and on the angle of incidence up to 40° is in good agreement with the experimental results.
Differentiation of Effects due to Grain and Grain Boundary Traps in Laser Annealed Poly-Si Thin Film Transistors
Authors: Armstrong G. A. , Uppal S. , Brotherton S. D. , Ayres J. R.
Published: October 2002

A new physical model based on two dimensional simulations for high quality laser re-crystallised poly-Si thin film transistors is presented. It has been shown that to adequately explain the improved subthreshold slope and the lack of saturation of the output characteristics in these transistors, it is essential to distribute the density of defect states between traps in the grains alongside traps localised at grain boundaries. A double exponential density of states has been extracted for thin film transistors (TFTs) annealed at different excimer laser energies, using the field effect conductance method. By splitting the density of states between grain traps and grain boundary traps good fits to the output characteristics have been achieved. Lack of saturation is shown to be due to decrease in potential barrier at grain boundaries with increase in drain bias. At high gate voltages, however, evidence of a self-heating effect similar to that observed in silicon-on-insulator (SOI) transistors is apparent.
Structural Studies on Hydrogenated Amorphous Germanium-Carbon Films Prepared by RF Sputtering
Authors: Minoru Kumeda Minoru Kumeda , Akio Masuda Akio Masuda , Tatsuo Shimizu Tatsuo Shimizu
Published: October 2002

ESR signals for hydrogenated amorphous Ge–C alloy films prepared by magnetron sputtering were deconvoluted into signals originating from a Ge dangling bond and a C dangling bond. It was determined from the results of the deconvolution that the number of Ge dangling bonds per Ge atom is ten to sixty times larger than that of C dangling bonds per C atom. In contrast to the case of Ge–Si alloy films, in which the number of Ge dangling bonds per Ge atom decreases by increasing the Si content because of the increase in the density of Si–H bonds, the number of Ge dangling bonds per Ge atom increases by increasing the C content in Ge–C alloy films, although the density of C–H bonds increases. This finding may be caused by an increase in the structural randomness because the difference in the covalent bond radius between Ge and C is quite large.
Low-Temperature Deposition of CuIn(SxSe1-x)2 Thin Films by Ionized Cluster Beam Technique
Authors: Sano Hiroyuki , Hirasawa Hiroshi , Nakamura Susumu , Kondo Kenichi , Sato Katsuaki
Published: October 2002

CuIn(S
x
Se1-x
)2 thin films were prepared on Mo-coated soda-lime glass substrates by the ionized cluster beam (ICB) technique, in which Cu, In2S3 and Se vapors were ionized and accelerated. The substrate temperature was kept at T
s=400°C. The films were characterized using X-ray diffraction (XRD), a scanning electron microscope (SEM), and an electron-probe microanalyzer (EPMA). It was found that polycrystalline films with improved grain size were obtained when the substrate temperature exceeded 250°C. Using the ICB technique, thin film solar cell devices based on these CuIn(S
x
Se1-x
)2 films were fabricated. The photovoltaic effect was confirmed in substrate-type structure solar cells with the low-temperature deposition of ICB-grown CuIn(S
x
Se1-x
)2 thin films.
Bipolar-Field-Effect-Transistor Hybrid-Mode Operation of Lateral Silicon-on-Insulator Bipolar Mode Field Effect Transistor with Improved Current Gain
Authors: Kim Doo-Young , Kim Seong-Dong , Han Min-Koo , Choi Yearn-Ik
Published: October 2002

A hybrid-mode operation of silicon-on-insulator (SOI) bipolar mode field effect transistor (BMFET) is proposed to improve the current gain. The device characteristics are analyzed and verified numerically for hybrid mode, BMFET mode, and double-diffused metal-oxide-semiconductor field effect transistor (DMOS) mode by MEDICI simulation. In hybrid-mode operation, DMOS, lateral bipolar transistor, and BMFET currents flow simultaneously. The proposed SOI BMFET exhibits 30 times larger current gain in hybrid mode operation by connecting DMOS gate to the p+ gate of BMFET structure as compared with the conventional structure without sacrifice of breakdown voltage and leakage current characteristics. The improved current gain characteristics are achieved by the DMOS-gate-induced hybrid effect that lowers the barrier of p-body and reduces the charge in the p-body.
NMR Study of R2Co7B3 (R=Y, Ce, Nd, Sm and Gd) Compounds
Authors: Maruyama Fumio , Nagai Hiroyuki , Amako Yasushi , Yoshie Hiroshi , Adachi Kengo
Published: October 2002

In order to study the magnetic properties of the Co-sublattice of R2Co7B3, the 59Co NMR and magnetic measurements have been carried out at 4.2 K. The R2Co7B3 (R=Y, Ce, Nd, Sm and Gd) compounds with a hexagonal Ce2Co7B3-type structure are obtained. The Co moments at the 6i
1 site are estimated from NMR and are found to be nearly consistent with those obtained from the magnetic measurements for R=Y, Sm and Gd. On comparing the calculated moments per unit cell, µ, with the saturation magnetization, M
s, for R=Y and Gd, the values of µ are found to be very consistent with those of M
s and the value of µ for R=Ce is much larger than that of M
s.
Effect of SiO 2 Sintering Aids on High Critical Temperature Positive Temperature Coefficient of Resistivity Properties of (Pb 0.6Sr 0.3Ba 0.1)TiO 3 Materials Prepared by Microwave Sintering Technique
Authors: Hu Chen-Ti , Chen Horng-Wen , Chang Horng-Yi , Lin I-Nan
Published: October 2002

Positive temperature coefficient of resistivity (PTCR) materials with the composition (Pb0.6Sr0.3Ba0.1)TiO3, possessing a high critical temperature as T
c=420° C, have been prepared by microwave sintering technique. Incorporation of SiO2 as sintering aids has lowered the sintering temperature (soaking time) required from 1250° C (10 min) to 1140° C (10 min), where the core-shell microstructure was fully developed. The electrical properties were stabilized for the samples containing more than 5 mol% SiO2 and sintered at a temperature higher than 1120° C (10 min). The resistivity ratio, PTCR jump and minimum resistivity achieved are (ρmax
/ρmin
)≈102.85–103.2 Ω· cm, PTCR=0.026–0.030 and ρmin
≈102 Ω· cm, respectively. The corresponding energy level of the donors ( Y+3-ions) and the effective electron traps (cationic vacancies) are estimated to be ε
d=0.077 eV and ε
a=0.67 eV+ε
F, respectively, where ε
F is the Fermi level of the materials. The electronic parameters, such as donor level (ε
d), PTCR jump and trap level (ε
a), are better parameters for indicating the perfectness of the densification process than the crystal structural and the microstructural examinations.
Novel Measurement Method for Flexoelectric Coefficients of Nematic Liquid Crystals
Authors: Taiju Takahashi Taiju Takahashi , Shigeru Hashidate Shigeru Hashidate , Hirokazu Nishijou Hirokazu Nishijou , Makio Usui Makio Usui , Munehiro Kimura Munehiro Kimura , Tadashi Akahane Tadashi Akahane
Published: October 2002

A new measurement method for the flexoelectric coefficients e
11 and e
33 (corresponding to the splay and bend strain, respectively) of nematic liquid crystals (LCs) is proposed. The values of e
11+e
33 and e
11-e
33 can be determined by fitting experimental electrooptical characteristics of hybrid aligned nematic (HAN) cells with numerical simulations. For the measurement of e
11+e
33 and e
11-e
33, a dc electric field is applied along the cell normal and along the cell surface, respectively. The measurements were carried out for two nematics, N-(4-methoxybenzylidene)-4′-n-butylaniline (MBBA) and ZLI-4792. As a result, e
11+e
33=(-5.4 ±1.0) ×10-11 C/m and e
11-e
33=(1.4 ±0.1) ×10-11 C/m for MBBA, | e
11+e
33 | ≤1.0 ×10-11 C/m and e
11-e
33=(-1.5 ±0.1) ×10-11 C/m for ZLI-4792 were obtained.
Near Band-Edge Photoluminescence in Strained and Relaxed Si1- xGe x/Si Quantum Wells
Authors: Yang Yu , Jiang Shiji , Tian Zihua , Wu Xinghui , Sheng Chi , Wang Xun
Published: October 2002

Near band-edge photoluminescence was observed from strained and relaxed Si1-x
Ge
x
/Si quantum wells grown by molecular beam epitaxy and annealed at 850–1100°C. Changes in the photoluminescence line energies were monitored, and the extent of both interdiffusion and relaxation in wells during annealing was calculated. Strain relaxation was observed only in quantum well structures annealed above 950°C. The experimental data confirmed the existence of an abrupt transition between stable and strain-relaxed Si1-x
Ge
x
/Si quantum well structures, and it was also observed that photoluminescence was sensitive enough to detect the onset of strain relaxation in quantum well structures following rapid thermal annealing.
Study on Photoacoustic Signals from Powdered Samples
Authors: Oka Takefumi , Tanaka Kunihiko , Tokunaga Taichi , Nakamura Takashi , Iiri Tomohiro , Yamazaki Makoto
Published: October 2002

Photoacoustic (PA) signals (amplitude and phase) from powdered samples are examined as a function of the effective absorption coefficient (k) of powder. Variation of the k value of a sample is accomplished by dilution of the sample in a diluent (BaSO4) with various degrees of dilution or by variation of the excitation wavelength for undiluted samples. It is determined that every powder studied shows a minimum in its PA phase vs k curve. A current theory of powder PA spectroscopy explains the presence of the phase minimum using a composite mechanism where the periodic expansion of buffer gas by heat transferred from the sample and the mechanical vibration of the sample are assumed as sources of the PA signal. The authors propose a method of estimating the relative value of k in a bulk sample from the phase minimum observed using the dilution method for the powdered sample.
Role of the EL2 Center on the Formation of Metastable Hydrogen-related Defects (M3/M4) in n-GaAs
Authors: Tatsuyuki Shinagawa Tatsuyuki Shinagawa , Tsugunori Okumura Tsugunori Okumura
Published: October 2002

Hydrogen-related metastable defects (M3/M4) in n-GaAs were studied in relation to the EL2 center. We found that the M3/M4 defects were observed only in the crystals containing the EL2 center in the as-grown state after exposure to a hydrogen plasma. The EL3 level, which was tentatively assigned as off-center oxygen, could not be responsible for the formation of the M3/M4 defects. It was speculated that both diffused hydrogen and the pre-existing arsenic antisite or its related defects were responsible for the formation of the M3/M4 defects. A quantitative analysis with the samples exposed to atomic hydrogen showed that the M4 defect consisted of two different configurations. A metastable component of the M4 defect coupling with the M3 defect was not formed or latent in the as-irradiated state at room temperature. After bias annealing at higher temperatures, such as 420 K, the M3/M4 couple was formed.
Phase Determination of Second-Order Surface Susceptibility Tensor of Liquid Crystal Monolayer Using Ultra-Thin Film Local Oscillator
Authors: Sei Masaki , Nagayama Kohei , Kajikawa Kotaro , Ishii Hisao , Seki Kazuhiko , Kondo Katsumi , Matsumoto Yoshiyasu , Ouchi Yukio
Published: October 2002

We demonstrated full determination of second-order nonlinear susceptibility of a 4′-n-octyl-4-cyanobiphenyl (8CB) liquid crystal (LC) monolayer adsorbed on a second-harmonic (SH) active polyimide (PI) substrate. In order to separate the SH signal of the LC film from that of the PI film, we adopted an interferometry technique of second-harmonic generation (SHG) using an ultra-thin film local oscillator. We have found a variety of phases in the components of susceptibility: those of χ
z
i
i
and χ
i
z
i
are almost the same but the phase of χ
z
z
z
differs by 80° from the other two. The phases of the components of the surface susceptibility tensor are not always identical. This fact indicates that the surface SH response is more complicated than what we expected.
A Study of Acoustic Emission in Piezoelectric Multilayer Ceramic Actuator
Authors: Aburatani Hideaki , Yoshikawa Shoko , de Vries Kenji Uchino
Published: October 2002

Acoustic emission (AE) in multilayer ceramic actuators (MCA) has been studied. It was observed that AE signals could be concealed by sample's mechanical vibrations under usual MCA driving conditions. These vibrations were caused by an electrical coupling between the sample's piezoelectricity and the power supply's feedback. The AE was observed around the coercive field under bipolar driving. On the contrary, with unipolar driving, the AE was not present until the applied voltage reached a certain critical voltage. It was clarified that the AE generation in MCAs was strongly dependent on the maximum pre-applied stress (Kaiser effect), which corresponds to the applied voltage. The onset voltage of AE can be used to estimate the existing damages in the MCA. During the poling process, larger numbers of AE was observed in damaged MCA than that of un-damaged ones.
Zero-Order-Free, Multilayer-Coated Laminar Grating in the 31 nm Region
Authors: Toyoda Mitsunori , Miyata Noboru , Yanagihara Mihiro , Watanabe Makoto
Published: October 2002

A laminar holographic grating was coated with a Mo/Si multilayer and the grating efficiency was measured between 27 and 35 nm for an incidence angle of 10°. The zero order was almost suppressed by the negative interference due to the groove profile. The maximum efficiency of first order was 4.8% at 31 nm. It was also found that the spectral wavelength provided by the grating at 10° incidence ranges from 28 nm to 32 nm.
Flocculation and Membrane Binding of Outer Membrane Protein F, Porin, at Acidic pH
Authors: Suzuki Keiko , Nakae Taiji , Mitaku Shigeki
Published: October 2002

Outer membrane protein F (OmpF), porin, of Escherichia coli is an intrinsic membrane protein made of a β-sheet barrel, the amino acid sequence being as hydrophilic as many soluble proteins in spite of its location in the hydrophobic region of membrane. The binding of porin molecules with a lipid membrane and the flocculation of the protein were studied at various pH, using the combination of centrifugation and intrinsic fluorescence measurements. The binding of porin with the lipid membrane occurred in the pH range below 7, whereas the flocculation of porin in the absence of the membrane was observed only at pH below 5. Porin molecules in the pH range between 5 and 7 were stable as a colloid but spontaneously bound with the lipid membrane soon after the addition of lipid vesicles. The possible mechanism of the structural formation of porin in the outer membrane was discussed based on the pH dependence of the membrane binding ability of this protein.
Optical Storage: Science and Technology
Authors: Mitsuhashi Yoshinobu
Published: October 2002

In this paper, various aspects of optical storage have been reviewed. First,
the author introduces storage needs which will continue to grow exponentially.
The advancement of Internet and computer software will accelerate the increase
of manageable data and the large storage requirements. This paper introduces
discussion topics such as applications, recording density limits and the progress
of science and technology. The possibility of optical dynamic random access
memory (ORAM) is mentioned in relation to memory hierarchy. To overcome the
density growth limit many kinds of attempts have been made including
introduction of super resolution, flying head recording, near field recording and
dynamic spatial phase control recording. In the future, optical storage with a high
recording density of 100 Gbit per square-inch and new amplification or enhancing
mechanisms for writing and reading of tiny marks will be important. The author
has raised the above issues which will be discussed.
Nitrogen Doping Effect on Phase Change Optical Disks
Authors: Kojima Rie , Okabayashi Shoichi , Kashihara Toshiaki , Horai Keiichiro , Matsunaga Toshiyuki , Ohno Eiji , Yamada Noboru , Ohta Takeo
Published: October 2002

The nitrogen doping effect on the Ge–Sb–Te recording layer was quantitatively examined. We
succeeded in the quantitative analysis of the nitrogen concentration in the Ge–Sb–Te–(N)
recording layer by secondary ion mass spectrometry (SIMS) observation. The nitrogen
concentration could be finely controlled at a high deposition rate of 4.7 nm/s. The addition of
a small amount of nitrogen remarkably improved the overwrite cycle numbers. We found that
the most suitable nitrogen concentration was from 2 to 3 at%. We proposed a model to explain
the nitrogen atom function in the recording layer. The nitrogen atoms produced nitrides, which
are condensed near the grain boundaries of Ge–Sb–Te microcrystals. This resulted in the
formation of very thin wrappings, which wrap the crystal grain in a manner similar to that of
the peel of a peach and suppressed the micro-material flow. We achieved 8×105 overwrite
cycles at λ=790 nm, N
A=0.50 and using the pit position modulation (PPM) recording
method where the minimum bit length is 0.87 µm.
Photoisomerization Quantum Yields of Naphthacenequinones Embedded into Polymeric Matrices
Authors: Binyukov Vladimir I. , Koroteev Nikolay I. , Krikunov Sergei A. , Magnitskii Sergei A. , Malakhov Dmitriy V. , Shubin Vladimir V. , Sokolyuk Nataliya T.
Published: October 2002

The differential photoisomerization quantum yield (QY) behavior of four derivatives of naphthacenequinone in toluene solution and in polymethyl methacrylate (PMMA), polyvinyl butirale (PVB) and polybutyl methacrylate (PBM-5) polymer films during direct and reverse reactions has been investigated. It was discovered that in all cases the initial QY in polymer matrices is higher than the QY in toluene solution.
Dual-Layer Optical Disk with Te–O–Pd Phase-Change Film
Authors: Nishiuchi Kenichi , Kitaura Hideki , Yamada Noboru , Akahira Nobuo
Published: October 2002

A recordable dual-layer optical disk that uses a Te–O–Pd phase-change film was studied
for high-density recording. In order to reduce thermal influence to adjacent tracks, we
selected the optimum composition of Te42O46Pd12 that gives low thermal conductivity. To
get equivalent signal amplitude and absorbance of layers, the thicknesses of the laser
incident side recording layer (Layer 1) and the other layer (Layer 2) are designed to be
20 nm and 55 nm, respectively. We confirmed that there was less than 10% bottom jitter
for both layers under the following recording densities: recording bit length of 0.41 µm
and track pitch of 0.74 µm. The laser powers required for recording on Layer 1 and
Layer 2 were typically 10 mW and 12 mW, respectively. The jitter was less than 13% for
both layers with large power tolerance of 30%p-p.
An Optical Head with Special Annular Lens for Laser Disc-Compatible Digital Versatile Disc Pickup
Authors: Yoo Jang-hoon , Lee Chul-woo , Cho Kun-ho , Choi Hyun-sub , Lee Jae-won
Published: October 2002

A compact and inexpensive design for a laser disc(LD)-compatible
digital versatile disc(DVD) pickup that uses a special annular
lens is presented and the measurement technique of the lens is described.
One objective lens having a special annular area functions
as an aberration-corrected lens for reading LD, compact disc recordable(CDR)
and DVD regardless of differences in substrate thickness.
The special area has an aspherical surface optimized for a thick substrate.
This lens can also be used for compact disc rewritable(CDRW).
4.7 GB Phase-Change Optical Disk for an Authoring System of Digital Versatile Disc
Authors: Nagata Ken'ichi , Saimi Tetsuo , Furukawa Shigeaki , Nishiuchi Ken'ichi , Yamada Noboru , Akahira Nobuo
Published: October 2002

A phase-change optical disk that has an optical phase-shift signal reproducing structure and the same physical specifications as the 4.7 GB read-only digital
versatile disc (DVD) was developed. A minimum jitter of 9% and a wide tilt tolerance for the jitter were obtained under DVD reproducing conditions of λ=650 nm and N
A=0.60. This new medium can be used
as an inspection tool for DVD authoring. It was also confirmed that this optical disk had a potential for use as a rewritable 4.7 GB DVD medium that has compatibility with the read-only DVD.
Thermal Radiative Emission of LiF and LiNbO 3 in the Near-Infrared Spectra
Authors: Chen Jyh-Chen , Chieh Hu Chieh Hu , Yeou-Chang Lee Yeou-Chang Lee
Published: October 2002

The thermal radiation for the wavelengths of 3–5, 5, 10.6 and 8–12 µ m emitted from heating rods is measured in this study by a two-dimensional thermal imaging radiometer. The LiNbO3 and LiF rods with both single crystal and polycrystalline structures are measured. The volumetric emission is enhanced by the scattering effect induced by the polycrystalline rod's porous structure. When the phase is changed from solid to liquid, the sharp decrease of the emission in the 3–5 µ m spectrum has been observed for the polycrystalline rods due to the disappearance of the scattering effect of the porous structure. Indeed, the emission in the 3–5 µ m spectrum does not significantly decrease for a LiF single-crystal rod. However, it still exists for a LiNbO3 single-crystal rod except that the difference in the emission levels decreases. As the phase change from solid to liquid occurs, the emission of LiF and LiNbO3 in the 10.6 µ m spectrum continuously increases regardless of whether the structure is a single crystal or polycrystalline.
Multi-Beam Optical System for Optical Tape Recording
Authors: Tokumaru Haruki , Okumura Hideyo , Arai Kiyotaka , Kawamura Norikazu , Yoshimura Shin-ichi
Published: October 2002

An optical tape recording system utilizing a rotating optical head is under
development as a mass storage device suitable for recording television programs.
High-quality moving pictures for broadcast require a correspondingly high bit rate of
over 100 megabits per second (Mbps) for recording. Toward the realization of such a
high bit rate, recording in parallel utilizing many laser beams is most effective. We
propose an optical system integrating a head that is suitable for parallel recording on
an optical tape with numerous laser beams. The optical system assumes the role of
keeping the lateral magnification constant during focusing. We studied the
effectiveness of such an optical system by the experimental construction of a four-beam optical head.
Digital Versatile Rewritable Disc (DVD-RAM) Complementary Allocated Pit Address (CAPA) Signal and Tracking Error Signal Detection Method; Improving Objective Lens Radial Shift Immunity
Authors: Yoshizawa Takashi , Satoh Hiroharu , Ohsawa Hideki
Published: October 2002

The complementary allocated pit address (CAPA) signal in
a digital versatile rewritable disc (DVD-RAM) is susceptible to an
objective lens radial shift; the reduction of its signal amplitude
occurs and the S/N ratio decreases. To alleviate this situation, we
propose a new readout signal processing scheme, the center
separate detection method (CSD) of discarding a large amount of
the 0-th diffracted light beam from the disc. We confirmed the
expected results by numerical simulation.
The New Re-writable Disc system for Digital Versatile Disc
Authors: Muramatsu Eiji , Yamaguchi Atsushi , Horikawa Kunihiko , Kato Masahiro , Taniguchi Shoji , Jinno Satoshi , Yamaguchi Masataka , Kudo Hideo , Inoue Akiyoshi
Published: October 2002

The authors have developed a new re-writable disc system named digital versatile disc (DVD)-RW. The basic concept of this system consists of the following characteristics.
1)  This system has added a re-writable feature to the DVD-R (write once system).
2)  It is compatible with DVD-ROM, DVD-Video and DVD-Audio systems.
By capitalizing on the characteristics of this system as much as possible, it will be possible to produce a useful standard, meeting the users' demand for video recording application of the DVD.
Two-Photon Single-Beam “Bit-by-Bit" Writing and Fluorescent “Page-by-Page" Reading 2.5D Femtosecond Optical Data Storage System
Authors: Koroteev Nikolay I. , Krikunov Sergei A. , Magnitskii Sergei A. , Malakhov Dmitriy V. , Shubin Vladimir V.
Published: October 2002

A novel scheme of rewritable multilayered (2.5D) optical data storage based on single-beam femtosecond two-photon consequent writing and fluorescent parallel readout has been developed. The table-top prototype is created to demonstrate writing-reading-erasing the information in dual-layer polymer photochromic matrices with equivalent information density of 50 Mbit/cm2 per layer.
Effect of Sb on Transport Properties of Thin Films of a-Ga20Se80- xSb x
Authors: Khan Zishan H. , Zulfequar M. , Malik M. Manzar , Husain M.
Published: October 2002

Temperature dependence (148–318 K) of dark conductivity and transient photoconductivity of thin films of a-Ga20Se80-x
Sb
x
(where x = 0, 5, 10, 15 and 20) is reported. It has been found that at temperatures (287–318 K), the conduction is taking place in the band tails of localized states, while at temperatures (148–287 K), the conduction is due to variable range hopping which shows fair agreement with Mott's condition of variable range hopping. The transient photoconductivity observations made at different temperatures indicate non-exponential decay and recombination may be considered to take place through valence and conduction band.
Effect of Electron Shading on Gate Oxide Degradation
Authors: Sakamori Shigenori , Maruyama Takahiro , Fujiwara Nobuo , Miyatake Hiroshi
Published: October 2002

The oxide degradation due to edge and electron shading effects is
investigated in a pulse-modulated plasma using metal-oxide-silicon
(MOS) and metal-nitride-oxide-silicon (MNOS) capacitors. Reduction of
edge defect, shading defect and electron shading charge build-up is
strongly dependent on the on-time in pulse plasma. In particular, when
the on-time is shorter than 50 µs, the coefficient of the shading defect
becomes almost zero. The investigation of MNOS capacitors, which have
the patterns with or without the substrate contact antenna, indicates
that the electric stress direction applied to gate oxide changes as
the device structure changes.
Highly Selective SiO2 Etching Using Inductively Coupled Plasma Source with a Multispiral Coil
Authors: Yamanaka Michinari , Hayashi Shigenori , Kubota Masafumi , Nakagawa Hideo
Published: October 2002

To exploit the highly selective SiO2 etching in an inductively coupled plasma (ICP) with
a multispiral coil (MSC), the effects of chamber wall heating and pulse modulation have
been examined, employing a laser-induced fluorescence (LIF) technique to detect CF
x

(x=1, 2) radicals. It was found that chamber wall heating up to 100°C in a CHF3/C4F8
plasma leads to a drastic increase in the SiO2 selectivity to Si, accompanied by an increase
in the radical densities. A further increase in the selectivity of SiO2 up to ∼45 was
realized by pulse modulation whereby the CF2 radical density increases with shortening of
the modulation period to 20 µs. The resultant high selectivity could be brought about by
controlling the production and extinction processes of the radicals in the MSC-ICP.
Mechanism of Radical Control in Capacitive RF Plasma for ULSI Processing
Authors: Tatsumi Tetsuya , Hayashi Hisataka , Morishita Satoshi , Noda Shuichi , Okigawa Mitsuru , Itabashi Naoshi , Hikosaka Yukinobu , Inoue Masami
Published: October 2002

The radicals of capacitive plasmas actually used in mass production were analyzed
using various measurement systems. The composition of radicals in bulk plasma depends on the
gas chemistry, the dissociation process, and interaction with the wall. It is revealed that parent
gas (C4F8) is dissociated by multiple collision with electrons according to τ·n
e<σv>,
where τ is the residence time, n
e is the electron density, σ is the dissociation collision cross
section and v is the electron velocity. A high-performance etching process, which can realize
0.09 µmφ contact holes with aspect ratio of 11, was achieved using a short residence time to
suppress the excess dissociation and the control of deposition species through the addition of O2
to C4F8/Ar plasma as well as the reduction of the density of F radicals through the reaction with
the Si wall.
Silicide-Silicon Schottky Barrier Heights Calculated Using an Interface-Defect Model
Authors: Kikuchi Akira
Published: October 2002

The Schottky barrier heights of transition-metal silicides on Si
are calculated using a model with multiple interface-defect levels.
The barrier heights decrease with increasing interface-defect
density. An increase in interface-defect density induces the strong
Fermi-level pinning which results in the pinning of the Schottky
barrier height. With a few exceptions, the measured barrier heights
are obtained for the defect densities of 1×1013–5×1013 cm-2 which are
found to be sufficient to pin the Fermi-level at the interfaces.
Quantum Cellular Automaton Device Using the Image Charge Effect
Authors: Wu Nan-Jian , Shibata Naoto , Amemiya Yoshihito
Published: October 2002

A quantum cellular automaton (QCA) device that uses the image charge effect is
proposed. This image-charge QCA device is constructed from many unit cells on a
metal substrate covered with an insulator layer. Each unit cell consists of four
quantum dots and two excess electrons. Two positive image charges in the metal
substrate maintain the charge neutrality of each cell. The distance between two
neighboring cells is designed to allow intercellular electron tunneling. The image-charge
QCA cell can overcome two basic problems: establishing charge neutrality
in each cell and loading electrons easily and precisely. We designed signal-transmission
and elemental logic gate circuits using these image-charge QCA cells, and
simulated operation of the circuits by computer simulation. It is demonstrated
that the image-charge QCA circuits can perform signal transmission and elemental
logic operations and that electrons (two per cell) can be easily loaded into the
image-charge QCA circuits.
Impact of Organic Contaminants from the Environment on Electrical Characteristics of Thin Gate Oxides
Authors: Ogata Tamotsu , Ban Cozy , Ueyama Akemi , Muranaka Seiji , Hayashi Tomohiko , Kobayashi Kiyoteru , Kobayashi Junji , Kurokawa Hiroshi , Ohno Yoshikazu , Hirayama Makoto
Published: October 2002

We have investigated the impact of organic contaminants
from the environment on the electrical characteristics of gate
oxides by evaluation of electrical characteristics of metal
oxide semiconductor (MOS) capacitors and gas
chromatography-mass spectrometry following thermodesorption
(TD-GC/MS) analysis of organic species adsorbed on silicon
surfaces. It was found that organic contaminants from the
environment adsorbed on silicon surfaces deteriorate gate
oxide reliability; the increase in both breakdown and infant
failure of gate oxides is enhanced by organic contaminants
from the environment and depends on gate oxide thickness and
the kind of silicon substrate. These results are useful for
clarifying the deterioration mechanism of gate oxides caused
by organic contaminants on silicon surfaces.
Surface Properties of a YBa2Cu3O7-δ Thin Film After Photo-Lithographic Treatment
Authors: Huh Yunsung , Kim Jin-Tae , Hwang Yunseok , Park Yongsup , So Youngjin , Kim In-Seon , Lee Soon-Gul , Park Gwangseo , Park Yong Ki , Park Jong-Chul
Published: October 2002

The effect of photolithographic treatments on the surface of a YBa2Cu3O7-δ thin film has been investigated by measuring the electrical contact resistance and performing X-ray photoemission spectroscopy (XPS) experiment. Water plays an important role in increasing the electrical contact resistance of the YBa2Cu3O7-δ thin film, as compared
with the developer and photoresist (PR); water removes oxygen from the surface and increases the contact resistance. The chemical interaction with the PR or developer is not a key element in increasing the contact resistance. XPS spectra show that the oxygen concentration of the surface of a YBa2Cu3O7-δ thin film is reduced after the photolithographic process.
Enhancement of Absorption Magnitude of Short-Wavelength Intersubband Transition in InGaAs/AlAs Quantum Wells
Authors: Asano Takashi , Noda Susumu , Sasaki Akio
Published: October 2002

Reduction of absorption magnitude with shortening of the intersubband
transition wavelength is observed in InGaAs/AlAs quantum wells on GaAs substrates.
Theoretical calculation of the carrier distribution shows that the reduction is caused by
carrier leakage to the X minimum of the AlAs barrier from the Γ minimum of the
InGaAs well. In order to regain the absorption magnitude, we undertake to suppress
the carrier leakage by reducing the density of states in the AlAs X minimum and by
increasing the energy spacing between Γ and X minima. The optimizations lead to the
enhancement of the absorption magnitude of more than fourfold, and a peak absorption
coefficient of 14000 cm-1 is obtained with an optimized structure. The results obtained
here are considered very useful for device applications of the short-wavelength
intersubband transitions.
Phase-Change Optical Disks for a High Data Transfer Rate
Authors: Okada Mitsuya , Ogawa Masatsugu , Kubogata Masayuki , Ohkubo Syu-ichi , Itoh Masaki
Published: October 2002

We studied a phase-change optical disk structure suitable for high linear
velocity, red laser source, and mark edge recording conditions in order to realize
high data transfer rate recording. On the conventional disk with a metal reflective
layer suitable for pit position recording, it was found that the increase in
overwrite jitter at low linear velocity conditions is small because “preceding
crystallization” functions effectively. It was proved that absorption control
between amorphous marks and crystalline erased area is indispensable for high
linear velocity conditions. Based on these studies, we designed an absorption-controlled
disk with a Si reflective layer and confirmed low overwrite jitter at a
wide range of linear velocity conditions up to 17.4 m/s.