bluuebunny/crossref_metadata_2025 huggingface dataset:
Improvement of Current Injection of Porous Silicon
Authors: Chen Yen-Ann , Liang Nai-Yuan , Laih Li-Hong , Tsay Wen-Chin , Mao-Nan Chang Mao-Nan Chang , Jyh-Wong Hong Jyh-Wong Hong
Published: October 2002

n-i-p-n hydrogenated amorphous silicon (a-Si:H) layers were deposited onto porous silicon (PS) formed on p-type crystalline silicon (c-Si) by anodization and used to improve the current injection of a PS-based light-emitting diode (LED). The electroluminescence (EL) spectrum for the obtained PS-based LED with n-i-p-n a-Si:H layers showed the similar tendency as that of a photoluminescence (PL) signal for an as-anodized PS. The current conduction mechanisms of this PS-based LED were also studied.
Highly Oxidation-Resistant TiN Barrier Layers for Ferroelectric Capacitors
Authors: Matsui Yuichi , Torii Kazuyoshi , Kushida Keiko , Hiroshi Miki Hiroshi Miki , Yoshihisa Fujisaki Yoshihisa Fujisaki
Published: October 2002

The characteristics of TiN film, which is well suited for use as the barrier layer of ferroelectric capacitors, were investigated. It was found that high-density TiN is more resistive against oxidation than low-density one. It was also revealed that the <200>-oriented TiN had higher oxidation resistance than the <111>-oriented one. However, whereas a thick Pt bottom electrode was previously used to prevent barrier layer oxidation, we found that the Pt thickness can be reduced to less than half with high-density <200>-oriented TiN. TiN oxidation followed the linear-oxidation law (a reaction-limited process) in the initial stage of oxidation, and the oxidation rate was found to be inversely proportional to the density and proportional to the etching rate. The etching rate of the <200>-oriented TiN was lower than that of the <111>-oriented TiN, indicating that (100) was less reactive than (111). Consequently, the <200>-oriented TiN film exhibited high oxidation resistance.
A New Model Silicon/Silicon Oxide Interface Synthesized from H10Si10O15 and Si(100)- 2×1
Authors: Zhang K. Z. , Meeuwenberg Leah M. , McFeely Mark M. Banaszak Holl
Published: October 2002

A model silicon/silicon oxide interface, synthesized from the spherosiloxane H10Si10O15 and Si(100)-2×1, has been characterized by study of the Si 2p core-levels and valence band region using soft X-ray photoemission. In addition, the intact H10Si10O15 cluster was condensed at -160° C onto Si(111)-H and characterized. The measured photoemission features are in good agreement with the results of previous model studies.
Trajectory Transition Due to Gate Depletion in Corrugation Gated Quantum Wires
Authors: Ochiai Yuichi , Widjaja A. Wahju , Sasaki Nobuyuki , Yamamoto Kazunuki , Ishibashi Kohji , Bird Jonathan P. , Aoyagi Yoshinobu , Sugano Takuo , Ferry David K.
Published: October 2002

We studied quantum interference effects observed in the low-temperature magnetoresistance of corrugation gated wires on a two-dimensional electron gas system. We have also studied the transport change due to deep gate depletion by means of the controlling gate voltage. We analyzed the gate voltage and magnetic field dependences of the negative magnetoresistance and observed small oscillations in the low-field magnetoresistances. The results show that a boundary-related or geometrical effect should strongly affect the phase-breaking mechanism in corrugation gated wires, and that the electron wave propagation differs between a narrow wire and a dot array, depending on the gate voltage.
Fabrication of InGaAs Quantum Wires and Dots by Selective Molecular Beam Epitaxial Growth on Various Mesa-Patterned (001)InP Substrates
Authors: Araki Moriaki , Hanada Yuuki , Hajime Fujikura Hajime Fujikura , Hideki Hasegawa Hideki Hasegawa
Published: October 2002

Systematic growth experiments were undertaken for the successful formation of InGaAs/InAlAs quantum wires and dots on patterned InP substrates by selective molecular beam epitaxy (MBE). Multi layer test structures consisting of InGaAs and InAlAs alternate layers were formed on 7 different types of mesa patterns including stripe- and square-shaped mesas oriented along the [110], [110] and [100] directions. The growth led to the formation of sidewalls consisting of a variety of facets. Although these sidewalls were often rough or not uniform, the growth on the stripe-mesas along the [110] and [100] directions, and the growth on the square-mesas with (201) sidewall facets were found to be promising since they resulted in very smooth sidewall facets, cross-sectional and lateral uniformity, and good growth selectivity. Using these results, InGaAs quantum wires and dots were successfully formed.
A Novel Functional Logic Circuit Using Resonant-Tunneling Devices for Multiple-Valued Logic Applications
Authors: Waho Takao , Kevin J. Chen Kevin J. Chen , Masafumi Yamamoto Masafumi Yamamoto
Published: October 2002

We have demonstrated a novel functional logic circuit using resonant-tunneling devices. By integrating six InGaAs-based resonant-tunneling diodes (RTDs) and one HEMT on an InP substrate, we achieved room-temperature operation of an analog-to-quaternary quantizer, or an inverter in 4-valued logic. The circuit is suitable for multiple-valued logic applications because it exhibits multiple thresholds as well as multilevel output using a simple circuit configuration.
An Equivalent Cicuit for CuO Modified Surface Barrier Layer Capacitors
Authors: Cheng-Fu Yang Cheng-Fu Yang
Published: October 2002

Nb2O5-doped (Ba0.8Sr0.2)(Ti0.9Zr0.1)O3 (BSTZ) is calcined at 1170°C for the complete formation of ABO3 phases. After calcination, CuO is added to BSTZ as a liquid phase promoter and an insulating boundary layer material. After sintering in a reducing atmosphere, the fired ceramics are cooled to an annealing temperature, then the cermics are annealed in air. The loss tangents of the fabricated ceramics increase with amount of CuO addition, but the maximum grain growth and maximum dielectric constant will reveal in 1 wt% CuO-added BSTZ. For BSTZ with different amount of CuO addition, the effective dielectric constant increases with the sintering temperature and decreases critically with annealing temperature and annealing time. When 60 min is used as annealing time, lower the annealing temperature is, more broad dielectric constant-temperature curves are. It is believed that the semiconductive BSTZ, which is residual in the center of the reoxidized BSTZ, will dominate the result.
Design Considerations for Patterned Wafer Bonding
Authors: Cha Giho , Lee Byoung H. , Lee Kyung W. , Bae Gum J. , Kim Wan D. , Lee Jun H. , Kim Il K. , Park Kyu C. , Sang I. Lee Sang I. Lee , Young B. Koh Young B. Koh
Published: October 2002

In patterned wafer bonding process, the debonded area occurring at bonding interface results from the poor wafer flatness of patterned wafer or from the different bonding speed in each position of the wafer. By reducing pressure when bonding occurs and by using interlayer films, we observed that the bondability of the patterned wafers enhances. In such a case, the result was also experimentally proved to be effective for the suppression of particles. In order to obtain the accurate alignment of the bonded wafers we specially designed a vacuum bonding machine, which has a function of self-controlled alignment mechanism (Rotating angle of <0.01°, side margin of <100 µ m). Finally, we obtained void free thin silicon on insulator (SOI) device layer not affecting in the successive lithography process.
Electronic States in Crescent-Shaped GaAs Coupled Quantum Wires
Authors: Arakawa Kazuhiro Komori
Published: October 2002

The electronic states in crescent-shaped GaAs coupled quantum wires on V-grooved substrate have been investigated by theoretical analysis using the finite element method (FEM). The doublet state, namely the symmetric and antisymmetric states, and the transverse electron states in crescent-shaped coupled quantum wires are clarified. The conditions of the coupling and the effect of the thickness disparity between two quantum wires are also clarified. The preliminary experiment on the photoluminescence (PL) characteristics of the crescent-shaped coupled quantum wires, fabricated on V-grooved substrate, are compared to the results obtained by the theoretical analysis. The observed PL peak splittings have been explained by the energy splitting between the symmetric and the antisymmetric states in the theoretical analysis. The experimental results are in good agreement with the results of theoretical analysis for weakly coupled quantum wires.
Thin Films of C 60 doped with Pb
Authors: Doroteo Mendoza Doroteo Mendoza , Francisco Morales Francisco Morales , Roberto Escudero Roberto Escudero
Published: October 2002

In the present work we report the synthesis of thin films of C60 doped with Pb. By means of electrical characterization we found that small quantities of Pb increases the electrical conductivity, giving as a result a semiconducting-like behavior in the range of temperatures from 2 K to 470 K. At higher content of Pb, the system tends to form particles of Pb. In this case, the electrical resistance shows a metallic-like transition below 7 K, but we did not observe zero resistance up to 2 K. We also found that the films readily reacts upon exposure to the laboratory atmosphere.
Phase Behavior and Bistable Switching Effects of the Induced Smectic Phase by Mixing Two Low Molecular Weight Nematic Liquid Crystals
Authors: Jenn Chiu Hwang Jenn Chiu Hwang , Yu Chyi Tsai Yu Chyi Tsai
Published: October 2002

The phase behavior and bistable effect of the induced smectic phase by mixing 4-Cyano-4′-pentyloxy biphenyl (5OCB) and 4-hexyloxy phenyl-4′-pentyl benzoate (HPPB) low-molecular-weight nematic liquid crystals have been studied. The 5OCB nematic crystal with a strong polar terminal group was miscible with the HPPB nematic crystal having a weak polar terminal group. The binary mixture showed an induced smectic phase over a wide range of concentrations and temperatures. Reversible transparent-opaque (light scattering) switching was observed upon the application of electric fields with low and high frequencies, respectively. Both the transparent and opaque states of the mixture could be maintained stably, even after the electric field was turned off (memory effect). A novel-type electrooptical effect based on light scattering was observed for the mixture in the induced smectic state.
Electrode and Interface Polarizations in Nematic Liquid Crystal Cells
Authors: Shuichi Murakami Shuichi Murakami , Hiroyoshi Naito Hiroyoshi Naito
Published: October 2002

Low-frequency dielectric properties were measured for study of the transport properties of impurity ions in nematic liquid crystal (NLC: 4-cyano-4'-pentyl biphenyl) cells with and without polyimide alignment layers. It was found that the dielectric behavior of the NLC cells without polyimide alignment layers is due to the electrode polarization. The diffusion constant and the concentration of the impurity ions are determined from the dielectric behavior. The NLC cells with polyimide alignment layers exhibit interface polarization between the polyimide alignment layers and the NLC slab. The ion concentration is estimated from the frequency at the dielectric loss peak of the interface polarization. The ion concentration is much higher in the NLC cells with polyimide alignment layers than in the cells without polyimide alignment layers, indicating that a considerable amount of impurity ions are dissolved from the polyimide layers. The temporal variations of the dielectric properties of the NLC cells with and without polyimide alignment layers after the cell preparation were also measured.
Suppression of the Hysteresis in a Homeotropic Aligned Ferroelectric Liquid Crystal Film
Authors: Ching-Yih Chen Ching-Yih Chen , Shu-Hsia Chen Shu-Hsia Chen
Published: October 2002

We investigated electro-optical effects in a homeotropic-aligned ferroelectric liquid crystal film. Hysteresis was observed in this cell. The width of the hysteresis could be suppressed by appropriate adjustment of external parameters in the experiment and the unwinding electric field could be reduced by rubbing of the substrate. The rewinding electric field could be increased by making the cell thicker.
Correlation between Soft X-Ray Emission and Dynamics of Fast Capillary Discharges
Authors: Hosokai Tomonao , Nakajima Mitsuo , Aoki Takayuki , Masao Ogawa Masao Ogawa , Kazuhiko Horioka Kazuhiko Horioka
Published: October 2002

A capillary discharge was driven by a fast pulse power generator `LIMAY-I' (3 Ω–70 ns) to investigate plasma dynamics. A two-stage pre-ionization circuit was developed to obtain uniformly preionized plasma load as the initial condition. Time-resolved radiations from the plasma column were observed by X-ray detectors and a fast streak camera. Experimental results indicated that the column can implode (rapidly contract) stably in an initial pressure range of 200–1000 Pa of argon. The reproducibility of the signal was quite good and the behavior of plasma column was well explained by one-dimensional magnetro-hydrodynamic (1D-MHD) simulation. These results suggest that the final plasma parameters satisfy the lasing condition for collisionally pumped Ne-like Ar with a sufficient margin of stability.
Behavior of Capillary Plasmas with Different Diameters
Authors: Sueda Tsuyoshi , Sunao Katsuki Sunao Katsuki , Hidenori Akiyama Hidenori Akiyama
Published: October 2002

During the early phase of electrothermal gun operation, the operation characteristics improve at low ambient pressures because the discharge occurs on the surface of the capillary, resulting in a higher rate of wall ablation and a higher capillary plasma density than in the case of operation at higher ambient pressures. In addition, it has been reported that reduction of the capillary diameter at low pressures results in an increase in the kinetic energy of the projectile. At low pressures, an electrothermal gun with a small capillary diameter is therefore superior to one with a large capillary diameter. In order to understand these experimental results clearly, we measured the plasma parameters of electron density and temperature, which are strongly related to the operation characteristics of the electrothermal gun, for different capillary diameters using a spectroscopic technique, and compared the results with results for a zero-dimensional time-dependent model. The electron density of the capillary plasma increases with decreasing capillary diameter.
Damage Reduction of Plasma-Treated Carbon Surfaces by Controlled Plasma
Authors: Yori Izumi Yori Izumi , Takeo Ohte Takeo Ohte , Akira Kojima Akira Kojima
Published: October 2002

A glassy carbon (GC) plate was treated with RF glow discharged argon (Ar) plasma in a vacuum chamber with two parallel-plate electrodes. The sheath voltage was controlled independently of other plasma parameters by means of a shunting circuit which was connected parallel to the electrodes. After 30 s of treatment without the shunting circuit, the contact angle of water on the GC surface decreased from 90° to 0°, and the half band width of the Raman band at 1360 cm-1 on the GC surface increased from 65 cm-1 to 85 cm-1 due to a disordered structure in carbon. When sheath voltage was kept constant at 80 V by means of the shunting circuit, the contact angle and the half band width changed to 0° and 72 cm-1 respectively, with a high ion density of 6×1010 cm-3. GC surfaces were modified sufficiently in a short time and protected from damage using a high-density of ions having moderate collision energy in controlled plasma.
Experimental Method for Evaluating Circulating Current Noise and Intrinsic Voltage Noise of a DC Superconducting Quantum Interference Device
Authors: Masakazu Nakanishi Masakazu Nakanishi
Published: October 2002

We demonstrated an experimental method for individually evaluating the circulating current noise and intrinsic voltage noise of a current-biased dc superconducting quantum interference device (dc-SQUID), which was previously considered impossible.
Evaluation of Electron Shading Charge Buildup Damage Using Metal-Nitride-Oxide-Silicon Capacitors
Authors: Sakamori Shigenori , Maruyama Takahiro , Fujiwara Nobuo , Hiroshi Miyatake Hiroshi Miyatake , Masahiro Yoneda Masahiro Yoneda
Published: October 2002

The damage from plasma-induced charge buildup caused by the “electron shading” effect was investigated in a pulse-modulated plasma using metal-nitride-oxide-silicon (MNOS) capacitors. The reduction of charge buildup depends strongly on the on-time. When the on-time is shorter than 50 µ s and the off-time is constant at 100 µ s, the potential difference between high and low aspect ratio patterns, ΔV, becomes zero. However, the shift in the flatband voltage is large in the case of 33.3 µ s on-time, and it corresponds to the degradation of the gate oxide. The potential of the silicon substrate is thought to become low compared to the polysilicon electrode. This indicates that the potential of the silicon substrate must also be controlled.
Cross-sectional Transmission Electron Microscope Studies on Intrinsic Breakdown Spots of Thin Gate Oxides
Authors: Ikeda Satoshi , Okihara Masao , Hidetsugu Uchida Hidetsugu Uchida , Norio Hirashita Norio Hirashita
Published: October 2002

Cross-sectional transmission electron microscopy was used to study the intrinsic breakdown spots of 10-nm-thick gate oxides thermally grown on (001) Si substrates. At a breakdown spot with a breakdown field of 15 MV/cm, (111) twin planes are confirmed by electron diffraction to exist in the surface region of the Si substrate. High resolution observation also reveals Si lattice fringes in the gate oxide, penetrating from the Si substrate and gate electrode of polycrystalline Si, and significant roughening of the anode interface between oxides and Si substrates. Also, similar growth twins and anode interface roughening are observed for a lower field breakdown spot with a breakdown field of 7 MV/cm. The presence of growth twins indicates that a Si substrate is locally molten during dielectric breakdown. These results are well explained by the local thermal breakdown model of intrinsic oxides. The interface roughening, presumably caused by deoxidization at the SiO2/Si interface in a local hot spot, is indicative of an initial stage of intrinsic dielectric breakdown of thin oxide.
Surface Morphology and Carbon Incorporation for Hexagonal GaN/(111)B GaAs Metalorganic Vapor Phase Epitaxy Using Dimethylhydrazine and Trimethylgallium
Authors: Kobayashi Yasuyuki , Ferdinand Scholz Ferdinand Scholz , Naoki Kobayashi Naoki Kobayashi
Published: October 2002

Using dimethylhydrazine (DMHy) as a group V source, we grew hexagonal GaN layers on (111)B GaAs substrates by low-pressure metalorganic vapor phase epitaxy. The surface morphology of the hexagonal GaN layers and the carbon incorporation in them strongly depend on the V/III ratio and the reactor pressure. A flat GaN surface can be obtained at the V/III ratio of 60 and the substrate temperature of 850° C. The carbon concentration decreases with increasing reactor pressure and the minimum concentration is 2×1019 cm-3 for hexagonal GaN grown at 300 Torr. Low-temperature photoluminescence measurements reveal that the band edge emission for the GaN grown at 300 Torr is dominant compared with that of a deep level.
Initial Stage of Stress-Induced Migration Phenomenon in Aluminum Interconnection on Semiconductor Device
Authors: Aoyagi Minoru , Asada Kunihiro
Published: October 2002

The initial stage of stress-induced migration in aluminum interconnections on semiconductor devices was studied through measurements of the electric resistivity and the residual-stress, as well as observations of grain growth during high temperature storage. It was shown that characteristics of the initial stage varied markedly depending on the storage temperature and period. The variation of the characteristics was affected not only by (1) increase in grain size or decrease in dislocation density upon recrystallization, but also by (2) degeneration at the grain boundary in the aluminum interconnection, which was considered to be a pile-up of dislocations. In this paper, we propose a model that the initial stage of the stress-induced migration is determined by competition between phenomena (1) and (2), and discuss the possibility that the open failure rate of the interconnection is correlated qualitatively with the change in the electrical resistivity at the initial stage.
Room Temperature InAsxP 1-x-ySby/InAs Photodetectors with High Quantum Efficiency
Authors: Gong XiuYing , Yamaguchi Tomuo , Kan Hirofumi , Makino Takamitsu , Iida Takefumi , Kato Takayoshi , Aoyama Mitsuru , Hayakawa Yasuhiro , Kumagawa Masashi
Published: October 2002

Room temperature surface-illuminated InAs
x
P1-x-y
Sb
y
/InAs photodiodes with an external quantum efficiency as high as 50–86% in a 1.83–3.53 µm wavelength range have been fabricated for the first time. Lattice matched heterostructures with a wide energy gap InAsPSb cap layer were grown on the InAs substrate using the liquid phase epitaxy technique. According to temperature dependence measurements for a 1 mm diameter photodiode, peak responsivities of 1.83–2.5 A/W have been realized in a temperature range of 296 to 200 K. The Johnson noise limited room temperature detectivities D
* are deduced to be 1\endash6 ×109 cm·Hz1/2/W at zero bias. It is demonstrated that the only loss of external quantum efficiency is from the reflection of the entrance face.
The Impacts of Back-End High Temperature Thermal Treatments on the Characteristics and Gate Oxide Reliability of Thin Film Transistor in Ultra Large Scale Integrated Circuit Process
Authors: Lee Kan Yuan , Fang Yean Kuen , Chen Chii Wen , Yaung Dung Niang , Wuu Kuen Hsien , Ho Jyh Jier , Liang Mong Song , Wuu Shou Gwo
Published: October 2002

The impacts of the two major high temperature treatments on the characteristics of thin film transistors (TFT's) in the back-end process of ultra large scale integrated circuit (ULSI) technology have been investigated. TFT's without any high temperature treatment show poor characteristics. High temperature furnace annealing and rapid thermal annealing (RTA) which are performed for boron phosphorous tetra ethyl ortho silicate (BPTEOS) planarization can improve the characteristics of low temperature recrystallized TFT. Then, the technologies used for contact annealing result significant difference on the characteristics of TFT's. High temperature furnace contact annealing can still greatly improve the characteristics of TFT's. However, after furnace annealing for BPTEOS planarization, RTA contact annealing deteriorates the characteristics of TFT. High temperature furnace annealing for BPTEOS planarization improves the charge to breakdown (Q
bd) value of the gate oxide of TFT and so does the furnace contact annealing. However, RTA contact annealing performed after the furnace planarization flow deteriorates that of the gate oxide.
Uniform Fabrication of Highly Reliable, 50–60 mW-Class, 685 nm, Window-Mirror Lasers for Optical Data Storage
Authors: Tada Hitoshi , Shima Akihiro , Utakoji Takeshi , Motoda Takashi , Tsugami Mari , Koki Nagahama Koki Nagahama , Masao Aiga Masao Aiga
Published: October 2002

Uniform fabrication of highly reliable 50–60 mW-class 685 nm laser diodes (LDs) with a window-mirror structure has been realized by using selective solid-phase Zn diffusion and three-inch full wafer processing. A window-mirror structure at the LD mirror is formed by Zn-induced disordering of an ordered GaInP multiple quantum-well (MQW) active layer. High uniformity of characteristics such as the operating current and the far-field pattern has been obtained by realization of highly uniform Zn diffusion. A small astigmatic distance (ΔZ≦3 µ m), a low relative intensity noise (R
I
N≦-135 dB/Hz) and a high speed response (T
r, T
f≦1.2 ns) are obtained in addition to the high-power and high-temperature characteristics (70 mW, 80° C) in spite of the existence of the window structure. The LDs have exhibited reliable 6,000–10,000 h operation under the conditions of 60° C and 50–60 mW for the first time.
Reduction of Beam Divergence Angle by Low-Refractive-Index Layers Introduced to Real-Refractive-Index-Guided GaAlAs High-Power Laser Diodes
Authors: Tadao Hashimoto Tadao Hashimoto , Osamu Imafuji Osamu Imafuji , Toru Takayama Toru Takayama , Masaaki Yuri Masaaki Yuri , Akio Yoshikawa Akio Yoshikawa , Kunio Itoh Kunio Itoh
Published: October 2002

A new approach for reducing a beam divergence angle vertical to the junction plane was proposed. Low-refractive-index layers were introduced adjacent to the active region in a real-refractive-index-guided high-power laser diode. The effects of the low-refractive-index layers on vertical near-field patterns were studied in detail through numerical calculations. The calculations indicated that the beam divergence angle vertical to the junction plane can be reduced with respect to the low-refractive-index layers without significant increase in the threshold current. The fabricated device exhibited a vertical beam divergence angle as small as 15.3° and threshold current as low as 22.7 mA. The actual vertical near-field pattern was found to be wider than calculated, which is attributed to the asymmetrical refractive-index profile in the vertical direction outside the stripe.
Rectification of the Diffusion Equations Proposed for Point Defects in Si Crystals during Melt Growth
Authors: Ryuichi Habu Ryuichi Habu
Published: October 2002

The author previously proposed diffusion equations which describe diffusion behavior of point defects in Si crystal growth ends during melt growth. The author would like to correct the mistakes made during the derivation of the diffusion equations, starting from the phenomenological diffusion equations.
Role of He Gas Mixture on the Growth of Anatase and Rutile TiO 2 Films in RF Magnetron Sputtering
Authors: Kunio Okimura Kunio Okimura , Akira Shibata Akira Shibata
Published: October 2002

The effects of He addition on the growth of crystallized TiO2 films and the change in both the substrate-incident ion current and plasma parameters in rf magnetron sputtering were investigated. The growth of rutile TiO2 was achieved on a non-heated substrate in the case of a mixture of Ar (10 sccm) and He (40 sccm) at a rather high total pressure of 20 mTorr. He (50 sccm) sputtering brought about anatase TiO2 film growth, improving radial inhomogeneity. Mass-resolved analyses of the substrate-incident ion current showed a significant change in species, such as Ar+, O2
+, O+ and Ti+, with increasing He. Studies using the Langmuir probe and gridded energy analyzer showed that high-energy electrons which contribute to excitation and ionization of reactant particles increased over the whole discharge space, while electron density decreased with increasing He. Metastable He atom densities were estimated by the optical absorption method and the effect of the Penning process was discussed quantitatively. We pointed out that the increase in high-energy electrons by He mixture is responsible for the change in the substrate-incident ion current and formation of anatase/rutile TiO2. The Penning effect caused by the metastable He atom was thought to be rather small in the present experimental condition.
Energy Loss Structure in X-Ray Photoemission Spectra of Single Crystalline LiNbO3, LiTaO3, MgO and α-Al2O3
Authors: Kohiki Shigemi , Fukushima Sei , Yoshikawa Hideki , Arai Masao
Published: October 2002

The energy loss structure in X-ray photoemission spectra was studied in detail for complicated band structure systems ( LiNbO3 and LiTaO3) and simple band structure systems (MgO and α- Al2O3). The energy loss structure on the lower kinetic energy side of core lines can be approximated by a sum of four components. The narrower peaks positioned at 7.0, 12.0 and 14.5 eV for LiNbO3, those at 8.0, 13.4 and 15.8 eV for LiTaO3, those at 11.3, 15.3 and 18.3 eV for MgO, and that at 14.5 eV for α- Al2O3 were assigned to interband transitions from the valence to the conduction bands. The peak positioned at 35.3 eV for α- Al2O3 was assigned to interband transition from the O2s level to the conduction band. The broader peaks positioned at 21.8 eV for LiNbO3, 22.6 eV for LiTaO3, 23.2 eV for MgO, and 25.2 eV for α- Al2O3 were ascribed to the single loss of the bulk plasmon excitation. The peak positioned at 49.9 eV for α- Al2O3 was ascribed to the double losses of the plasmon excitation. The observed plasmon energies are larger than the estimated one in the free electron gas model for each substance (10 eV for the complicated and 1 eV for the simple systems).
Oxygen Plasma Treatment of Rubber Surface by the Atmospheric Pressure Cold Plasma Torch
Authors: Lee Bong-ju , Kusano Yukihiro , Kato Nobuko , Naito Kazuo , Horiuchi Takao , Hideomi Koinuma Hideomi Koinuma
Published: October 2002

A new application of the atmospheric cold plasma torch has been investigated. Namely, the surface treatment of an air-exposed vulcanized rubber compound. The effect of plasma treatment was evaluated by the bondability of the treated rubber compound with another rubber compound using a polyurethane adhesive. The adhesion property was improved by treatment of the rubber compound with plasma containing oxygen radicals. Physical and chemical changes of the rubber surface as a result of the plasma treatment were analyzed by field emission scanning electron microscopy (FE-SEM) and fourier transform infrared attenuated total reflection (FTIR-ATR).
Subharmonic Waves Generation by Parametric Decay of Bubble Oscillations
Authors: Fujii Masanori Sato
Published: October 2002

It is well known that subharmonic ultrasonic waves are generated in liquid when acoustic cavitation occurs. In order to confirm this experimentally, generation of subharmonic ultrasonic waves in water was undertaken and various subharmonic waves of the orders such as 1/2, 1/3, 2/3, 1/4, and nonrational number ratio were detected, in addition to first and higher-order harmonic waves. The generation mechanism of the subharmonic waves was discussed based on a model of the nonlinear interaction between ultrasonic waves and bubbles. The pumping wave that generates the subharmonic waves is considered to be radial bubble oscillation in unison with the input frequency, due to the energy received from the ultrasonic waves. This oscillation, in turn, emits ultrasonic waves with subharmonic frequencies through parametric decay when certain matching conditions in the dispersion relation are fulfilled. This process can be treated as analogous to that of an acoustic phonon.
Temperature Dependence of Dielectric, Elastic and Piezoelectric Properties of Pb(ZrxTi 1-x)O 3 Ceramics Near the Morphotropic Phase Boundary
Authors: Shen Zhang Shen Zhang , Xianlin Dong Xianlin Dong , Seiji Kojima Seiji Kojima
Published: October 2002

The dielectric properties and piezoelectric resonance frequency were studied in 0.5 wt% Nb2O5 doped Pb(ZrxTi1-x
)O3 ceramics (x=0.52 and 0.53) near the morphotropic phase boundary. The inverse dielectric constants were plotted as a function of temperature, and the broad anomaly-related MPB and thermal hysteresis were successfully observed in temperature ranges from 220 K to 320 K for PZT52/48 and from 300 K to 400 K for PZT53/47. The frequency constants of PZT52/48 and PZT53/47 also showed broad anomalies in the same temperature ranges. These broadenings reflect the coexistence of the tetragonal and rhombohedral phases near the MPB. The temperature dependence of electromechanical coupling factor, the shear modulus and Poisson's ratio were determined from the observed data.
Experimental Surface Acoustic Wave Properties of AlN Thin Films on Sapphire Substrates
Authors: Kaya Kiyoshi , Takahashi Hiroshi , Shibata Yoshihiko , Hirai Yasuhito Kanno
Published: October 2002

Equivalent circuit model parameters of Rayleigh propagation along the [001] axis of AlN (110) thin films synthesized using chemical vapor deposition on a sapphire R-plane were measured. The electro-mechanical coupling constant was 0.63% at k
h≧2, and the static capacitance was 46.3 pF/m in the case that the line/space ratio was unity. The acoustic impedance and the normalized susceptance were obtained as a function of wavelength of surface acoustic wave for various line/space ratios.
Measurement of Two-Dimensional Temperature Distribution in Water Using Acoustooptic Interaction
Authors: Koichi Mizutani Koichi Mizutani , Masabumi Mizunuma Masabumi Mizunuma , Masahiro Yoshioka Masahiro Yoshioka , Keinosuke Nagai Keinosuke Nagai
Published: October 2002

A method of realizing two-dimensional temperature distribution in water by means of optical Fourier transform is described. Using this method, the water temperature distribution is obtained from a small spatial domain where an ultrasonic beam perpendicularly intersects a laser beam. The temperatures are measured at 64 points in a 28×28 mm2 region. The error of measurement is within 1°C. The present method can be applied to measurements of concentration or density, because in this method, the water temperature is obtained from the acoustic wave velocity.
Analysis of Local Lattice Strains Around Plate-Like Oxygen Precipitates in Czochralski-Silicon Wafers by Convergent-Beam Electron Diffraction
Authors: Okuyama Tetsuya , Nakayama Masaru , Sadamitsu Shinsuke , Nakashima Jyun , Tomokiyo Yoshitsugu
Published: October 2002

Convergent-beam electron diffraction (CBED) is used to study lattice strain around plate-like oxygen precipitates in Czochralski (CZ)-grown silicon. Local lattice strain determined from higher-order Laue zone (HOLZ) patterns shows that compressive and tensile stress fields exist near the precipitates. The spatial variation of local lattice strain and lattice rotation is visualized in a defocused large angle CBED disc, or a convergent-beam imaging (CBIM) disc.
Hall Effect Measurement and Band Bending Calculation of Hydrogenated Diamond Film Grown by Chemical Vapor Deposition
Authors: Shirakawa Yusuke , Anda Yoshiharu , Tetsuro Maki Tetsuro Maki , Takeshi Kobayashi Takeshi Kobayashi
Published: October 2002

The surface conductive layer in a hydrogenated chemical vapor deposited diamond film was studied experimentally and analytically. The Hall effect measurement showed that the hole areal density at the surface introduced unintentionally was as high as 1013/ cm2, which was about an order of magnitude higher than that used in the conventional field-effect transistors. We have analyzed the surface band bending from the quantum-mechanical point of view to determine the equivalent Fermi level pinning position settled after hydrogenation. It was found that, at the surface, the Fermi level locates inside the valence band at a depth of 0.36 eV from the valence band edge.
A Simple Graphical Method for Determining Densities and Energy Levels of Donors and Acceptors in Semiconductor from Temperature Dependence of Majority Carrier Concentration
Authors: Hideharu Matsuura Hideharu Matsuura
Published: October 2002

The purpose of this study is to propose a simple graphical method for accurately determining the densities and energy levels of donors and acceptors with different energy levels in a semiconductor from the temperature dependence of majority carrier concentration n(T). For this purpose, a function S(T,E
ref) is defined as S(T,E
ref) ≡n(T) exp
(E
ref/k
T) /k
T, where k is the Boltzmann constant and E
ref is a parameter which varies a peak temperature of S(T,E
ref). Since S(T,E
ref) has peaks corresponding to the energy levels of impurities which produce majority carriers, the density and energy level can be evaluated using each peak in the S(T,E
ref) curve. This method can be used to investigate how many kinds of impurities, which produce majority carriers, exist in a semiconductor. Moreover, the density of all impurities, which produce minority carriers, can be determined, since we can simulate the dependence of S(T,E
ref) on this density.
Melt Mixing of the 0.3In/0.7GaSb/0.3Sb Solid Combination by Diffusion under Microgravity
Authors: Okitsu Kazuhiko , Hayakawa Yasuhiro , Yamaguchi Tomuo , Hirata Akira , Fujiwara Syogo , Okano Yasunori , Imaishi Nobuyuki , Yoda Shin-ichi , Oida Toshihiko , Masashi Kumagawa Masashi Kumagawa
Published: October 2002

In order to investigate the effects of diffusion and convection on the melt mixing of semiconductors, experiments under microgravity in space and 1-g on earth were conducted. Sandwich combinations of In/GaSb/Sb solids closed in a BN cylinder were heated up to 733° C in space and 744° C on earth, and they were then cooled rapidly. In both samples, many needle crystals were distributed in the whole area. It was observed that the melt mixing in space was controlled by diffusion which was represented with an error function, and the diffusion coefficient of indium was given by a value of 2.4×10-4 cm2/ s. In the earth sample, however, the indium concentration distribution followed an exponential curve. This indicated that both factors, diffusion and thermal convection, have contributed to the mixing of semiconductor melts.
Real-time Ellipsometry Studies of Gold Thin-Film Growth
Authors: Soonil Lee Soonil Lee , Junegie Hong Junegie Hong , Soo-ghee Oh Soo-ghee Oh
Published: October 2002

In-situ ellipsometry was used to monitor the growth of Au thin films deposited on SiO2/Si substrates by magnetron sputtering. To analyze the growth curves, which are Δ vs ψ curves measured in real time, we introduced various growth models and calculated the effective dielectric constants of the growing films using effective medium approximations. Analysis results show that Au thin films do not grow layer-by-layer, rather they grow as islands following the initial nucleation. As the islands grow bigger, they come in contact with each other and coalesce. The Au thin films continue to grow to become continuous films exhibiting surface roughness. The optical characteristics of the Au thin films in the nucleation and coalescence stages are found to be markedly different from those of the bulk Au.
Optical Properties of Photochromic Dyes in the Amorphous State
Authors: Kaneuchi Yoshihiro , Tsuyoshi Kawai Tsuyoshi Kawai , Maki Hamaguchi Maki Hamaguchi , Katsumi Yoshino Katsumi Yoshino , Masahiro Irie Masahiro Irie
Published: October 2002

Optical properties of photochromic dyes, 1,2-bis(2-methylbenzo[b]thiophen-3-yl)perfluorocyclopentene (BFCP) and cis-1,2-dicyano-1,2-bis(2,4,5-trimethyl-3-thienyl)ethene have been studied in the solid state. These photochromic dyes have been found to form a stable amorphous solid state when they are sandwiched between two glass plates. The time for the transition from the amorphous state to the crystalline state increases with decreasing distance between the two glass plates. The amorphous solid films clearly show photochromism upon light irradiation and also a marked change in photoluminescence intensity. The crystallization of the open-ring BFCP isomer is much faster than that of the closed-ring isomer. It has also been revealed that the photoluminescence spectrum of BFCP changes upon photoisomerization.
Amorphous and Microcrystalline Silicon Deposited by Low-Power Electron-Cyclotron Resonance Plasma-Enhanced Chemical-Vapor Deposition
Authors: Schotten João Pedro Conde , Arekat Safwan , Brogueira Pedro , Sousa Rui , Chu Virginia
Published: October 2002

The structural and optoelectronic properties of intrinsic amorphous silicon (a-Si:H) and microcrystalline silicon ( µc-Si:H) deposited using electron cyclotron resonance plasma-enhanced chemical vapor deposition (ECR-PECVD) with a microwave power of 150 W were studied as a function of the ECR source-to-substrate distance, d
ss, process pressure, hydrogen dilution and substrate temperature. Hydrogen was used as the excitation gas and silane was injected into the main chamber. Deposition rates show a maximum as a function of the deposition pressure. For d
ss=6 cm this maximum occurs between 5 and 10 mTorr. ECR-deposited a-Si:H films show a high Tauc bandgap (∼1.9 eV), low dark conductivity (∼10-11 Ω-1 cm-1), relatively high Urbach energy (≥55 meV) and high defect density (≥5×1015 cm-3) compared with a-Si:H grown by RF glow discharge. Hydrogen evolution and infrared spectroscopy reveal the presence of voids and/or columnar structure. The transition from amorphous to microcrystalline silicon occurs under conditions of high hydrogen dilution, low deposition pressure, and low d
ss. The higher the hydrogen dilution, the lower the substrate temperature needed to achieve µc-Si:H. Raman spectra of the µc-Si:H suggest small grain size ( ∼4 nm) and crystalline fraction (∼60%). A growth model is proposed that includes silane excitation both by the ECR electrons and by the excited hydrogen species.
Gas Source Molecular Beam Epitaxy Growth of GaN-Rich Side of GaNP Alloys and Their Observation by Scanning Tunneling Microscopy
Authors: Reiko Kuroiwa Reiko Kuroiwa , Hajime Asahi Hajime Asahi , Kakuya Iwata Kakuya Iwata , Seong-Jin Kim Seong-Jin Kim , Joo-Hyong Noh Joo-Hyong Noh , Kumiko Asami Kumiko Asami , Shun-ichi Gonda Shun-ichi Gonda
Published: October 2002

The GaN-rich side of a GaNP alloy exhibits a potentially large variation in band-gap energy with P content due to its large bowing. To study the phase separation observed in GaNP grown on a (0001) sapphire substrate with a P content larger than 0.015, GaNP layers are grown on (111)A substrates by electron cyclotron resonance molecular beam epitaxy (ECR-MBE). During the growth of GaNP layers, reflection high energy electron diffraction (RHEED) exhibits additional spotty patterns indicating phase separation as well as (1×1) streaks. Scanning tunneling microscopy (STM) images on the phase-separated samples show the bright clusters with about 3 nm in size, which correspond to the phase-separated GaP-rich region. I-V curves on the bright clusters are quite different from those on other areas indicating a lower band-gap energy.
Barrier-Height Imaging of Oxygen-Adsorbed Si(111) 7×7 Surfaces
Authors: Shu Kurokawa Shu Kurokawa , Mitsuhiro Yuasa Mitsuhiro Yuasa , Akira Sakai Akira Sakai , Yukio Hasegawa Yukio Hasegawa
Published: October 2002

Barrier-height imaging with scanning tunnelimg microscopy (STM) is applied to the study of oxygen adsorption on a Si(111) 7×7 surface. On clean surfaces, atomic resolution is obtained in the barrier-height mode, as expected for corrugated surfaces. Upon exposure to oxygen, the barrier height φ is found to increase at the oxygen-reacted sites. The dark sites show a greater increase in φ than the bright sites, indicating more charge transfer at the dark sites.
Atomic-Like Properties of Semiconductor Quantum Dots
Authors: Tarucha Seigo , Austing David Guy , Honda Takashi , van der Hage Rob , Kouwenhoven Leonardus Petrus
Published: October 2002

We use a gated submicron double-barrier resonant tunneling structure to study transport properties of a semiconductor quantum dot containing a tunable number of electrons starting from zero. At zero magnetic field the addition energy has large maxima for special numbers of electrons in the dot, reflecting a shell structure of electronic states in a circular dot with a harmonic lateral potential. As a function of magnetic field, current peaks evolve in pairs. This arises from the antiparallel filling of spin-degenerate states. Close to zero magnetic field, however, this pairing is rearranged to favour the filling of states with parallel spins in line with Hund's rule. These observations demonstrate that the electronic spectrum for our quantum dots is analogous to that of real atoms. When the dot has asymmetry in the lateral shape, the addition energy spectrum is readily modified reflecting the disruption of the shell structure.
Construction of Semiconductor Nanoparticle Layers on Gold by Self-Assembly Technique
Authors: Nakanishi Takuya , Bunsho Ohtani Bunsho Ohtani , Kohei Uosaki Kohei Uosaki
Published: October 2002

Cadmium sulfide (CdS) nanoparticles were prepared using the Aerosol-OT (AOT)/heptane inverse-micelle method. The particle size was controlled by changing the [H2O]/[AOT] ratio in the preparation process to be ca. 3 nm, which was estimated from their absorption maximum ( ca. 385 nm) and absorption edge ( ca. 450 nm) in heptane solutions. Self-assembled monolayers (SAMs) of α,ω-dithiols were prepared on (111)-oriented gold substrates. They were highly stable in aqueous solutions and showed a blocking effect toward electron exchange between the gold substrate and the electroactive species in the solution. Mono- and multi-layers of CdS nanoparticles were prepared by immersing the SAM-covered gold substrates in a heptane solution containing CdS particles. Infrared reflection-absorption spectra revealed that CdS particles on SAMs were surrounded by AOT and that a sequential immersion procedure led to the alternately layered structure of CdS particles and dithiol molecules.
Growth and Characterization of Coherent Quantum Dots Grown by Single- and Multi-Cycle Metal-Organic Chemical Vapour Deposition
Authors: Kochnev Igor V. , Ledentsov Nikolai N. , Maximov Mikhail V. , Tsatsul'nikov Andrew F. , Sakharov Alexey V. , Volovik Boris V. , Kop'ev Petr S. , Alferov Zhores I. , Bimberg Dieter , Kosogov Alexander O. , Ruvimov Sergey S. , Werner Peter , Gösele Ulrich
Published: October 2002

Very strongly electronically coupled zero-dimensional structures were grown using metal-organic chemical vapour deposition (MOCVD). The method is based on formation of first a sheet with InGaAs pyramids on the GaAs (100) surface, and subsequent alternate short-period GaAs–InGaAs deposition with GaAs layer thickness much smaller than the pyramid height. This results in formation of column-like InGaAs structures. Each structure has a characteristic lateral size of ∼23 nm at the top and is composed of many closely packed InGaAs parts separated by only 2–3 monolayer-thick GaAs barrier layers. Each upper InGaAs part in a column is progressively larger than the lower parts. The full width at half-maximum of luminescence of 28 meV at 8 K indicates good average uniformity of the electronically coupled dot ensemble. Effective tunability of the emission wavelength at and around 1.3 µ m can be realized using this approach.
InAs/GaAs Quantum Dots Grown by Metalorganic Chemical Vapor Deposition
Authors: Frank Heinrichsdorff Frank Heinrichsdorff , Alois Krost Alois Krost , Nils Kirstaedter Nils Kirstaedter , Ming-Hua Mao Ming-Hua Mao , Marius Grundmann Marius Grundmann , Dieter Bimberg Dieter Bimberg , Alexander Olegovich Kosogov Alexander Olegovich Kosogov , Peter Werner Peter Werner
Published: October 2002

InAs quantum dots (QDs) have been grown by metalorganic chemical vapor deposition on exactly (001) oriented GaAs using the Stranski-Krastanow growth mode. The samples exhibit a high average dot density of 4 ×1010 cm-2 with no defects over macroscopic areas. The QDs show bright room temperature luminescence at around 1.1 eV. Vertical dot stacks consisting of up to 5 QD sheets with various GaAs separation layer thicknesses have been produced. Transmission eletron microscope images show pronounced QD ordering in the growth direction. For thin separation layers the dot luminescence is red shifted by ∼ 70 meV for the stacked dots as compared to single dot sheets. A low threshold (100 A/cm2 at 77 K) separate confinement heterojunction laser with a five-fold dot stack as an active medium operating at up to room temperature is demonstrated.
Charging Effect of InAs Dots in Split-Gate High Electron Mobility Transistor Structure
Authors: Yoh Kanji , Konda Jun , Sanshiro Shiina Sanshiro Shiina , Norihiko Nishiguchi Norihiko Nishiguchi
Published: October 2002

We report on a series of distinct current oscillations due to charging of InAs dots in a GaAs double heterojunction field-effect transistor (DHFET) with self-assembled InAs dots formed on the bottom of the channel. These peaks can be interpreted by the tunneling of electrons from the channel to the InAs dots resulting in the threshold voltage shift. Observed number of currrent peaks suggests that each dot can accomodate up to six electrons. Based on the InAs dot size estimated by Transmission Electron Microscope (TEM) observation, relatively large effective mass of 0.06 m0–0.08 m0 were estimated in order to account for accomodation of six electrons per dot.