bluuebunny/crossref_metadata_2025 huggingface dataset:
Sintering Characteristics and Formation Mechanisms of “Core-Shell” Structure in BaTiO3-Nb2O5-Co3O5 Ternary System
Authors: Chazono Hirokazu , Masayuki Fujimoto Masayuki Fujimoto
Published: October 2002

The formation mechanism of the “grain core-grain shell” structure was investigated for the BaTiO3-Nb2O5-Co3O4 ternary system with two different Nb/Co ratios, in terms of sintering characteristics. The temperature dependence of the dielectric constant, the densification behavior and the grain growth rate were considerably influenced by the Nb/Co ratio, but the core-shell structure was observed in both compositions. Densification occurred after the additives reacted with BaTiO3, as confirmed by X-ray diffraction measurment. The densification behavior was normal with Nb-rich composition but showed two steps in Co-rich composition due to the change of the diffusion mechanism. The liquid phase formed by the secondary-phase Ba6Ti17O40 did not promote densification with these compositions because of its poor wettability with the matrix. The diffusion rate of Nb into the center of BT was smaller than that of Co, and Co was trapped with Nb in the simulation experiment. A model of the formation mechanism of the “core-shell” structure has been developed.
Dielectric Relaxation of (Ba, Sr)TiO3 Thin Films
Authors: Horikawa Tsuyoshi , Makita Tetsuro , Kuroiwa Takeharu , Noboru Mikami Noboru Mikami
Published: October 2002

The dielectric relaxation of (Ba0.5Sr0.5)TiO3 thin films with high electric resistivity is investigated. The films are deposited by an rf-magnetron sputtering method in an atmosphere of argon and oxygen. The dielectric dispersion of the films is measured in the frequency range of 10-2-106 Hz. It is found that the dielectric constant ε slightly decreases with frequency, following the relationship of dε/d(log
10
f)∼-0.01ε, and the dielectric loss is almost constant at less than 1% in the measured frequency range. This type of dielectric relaxation causes absorption current which is inversely proportional to time, as the result of the dielectric aftereffect. In a dynamic random access memory (DRAM) operation, the dielectric relaxation would result in less than 10% loss of storage charge during the refresh cycle, and the film's DC leakage less affects the device operation.
Formation Mechanism of p-Type Surface Conductive Layer on Deposited Diamond Films
Authors: Gi Ri Sung , Mizumasa Tatsuhiro , Akiba Yukio , Hirose Yoichi , Kurosu Tateki , Masamori Iida Masamori Iida
Published: October 2002

A model of the formation of a p-type surface conductive layer on deposited diamond films is proposed. According to the model, the ionization of acid in water produces oxonium ion ( H3O+) which reacts with hydrogen on diamond films and causes the creation of holes in diamond films. The model also explains the disappearance of the p-type surface conductive layer by the action of alkaline substances. The experimental results concerning the change in electrical resistance at the surface of diamond films can be explained using the proposed model.
High-Temperature Superconducting Motor Using Y-Ba-Cu-O Bulk Magnets
Authors: Itoh Yoshitaka , Yanagi Yousuke , Yoshikawa Masaaki , Oka Tetsuo , Harada Shintaro , Sakakibara Tsutomu , Yamada Yuh , Mizutani Uichiro
Published: October 2002

A DC motor equipped with melt-processed Y-Ba-Cu-O (YBCO) superconductors as field magnets was constructed. The YBCO bulks were magnetized at temperatures of 65-77 K in a liquid nitrogen vessel by applying a pulsed magnetic field. The maximum output power was 940 W when the YBCO bulks were cooled to 65 K.
Continuous running tests were carried out for up to 6 h. We found that the trapped magnetic fluxes are hardly affected by the magnetic field of 7500 A/m generated by the armature current and that cooling of the YBCO bulks to low temperatures is very effective for holding the trapped field at a high level and, hence, substantially elevating the performance of a high-temperature superconducting (HTSC) motor.
Theoretical Analysis of Multimode Pumped Second-Harmonic Generation
Authors: Zhou Wang-Long , Mori Yusuke , Sasaki Takatomo , Sadao Nakai Sadao Nakai
Published: October 2002

Type I and Type II second-harmonic generations (SHG) with a randomly phased multimode pump have been theoretically analyzed by considering phase mismatch and fundamental bandwidth effect. The equations obtained in the paper are formulated in a very concise and analytic form, which can be used to evalute both conversion efficiency and spectrum. We found that the previously recognized multimode enhancement effect does not exist in Type II SHG.
The issue of harmonic instability due to multimode pumping has been also discussed.
Transitions between Glow and Arc Modes and Its Influences to the Performance of a Hollow-Cathode Discharge CO2 Laser
Authors: Ivković Milivoje , Nikola Konjević Nikola Konjević
Published: October 2002

Hollow cathode discharge is used for excitation of a CO2 laser. With the aluminum alloy cathode a maximum laser output power of 4.1 W is obtained. This laser output power is related to the formation of aluminum oxide at the cathode surface. These oxide layers induce the transitions between the glow and arc modes of the discharge and formation of microarcs at the cathode surface. This was found beneficial for the laser operation. The results of the time resolved study of the laser parameters are also reported.
Change in UV Transmittance in Silica Photomask Glass under KrF Excimer Laser Irradiation
Authors: Shimbo Masaru , Kenichi Sato Kenichi Sato
Published: October 2002

Change in optical transmittance of silica photomask glass, synthesized by flame hydrolysis of SiCl4, was measured in situ under KrF exima laser irradiation. Photoabsorbance at 215 nm has a peak at 2-3×103 pulse irradiation. The transmittance after cessation of the irradiation recovers having two relaxation times of approximately 10 and 100 s. The maximum absorbance decreases with increasing OH content in the glass. The 0.4th power dependence of the absorbance on the laser power density ( frequency×intensity) is explained by assuming that the saturated absorbance is proportional to the degree of the E
′ center formation reaction, and is reciprocal to that of the OHC related 1.9 eV photoemission reaction.
Electronic Conduction Characteristics of Sel-Gel Ferroelectric Pb(Zr0.4Ti0.6)O3 Thin-Film Capacitors: Part II
Authors: Mihara Takashi , Hitoshi Watanabe Hitoshi Watanabe
Published: October 2002

We studied the electronic conduction characteristics of sol-gel ferroelectric Pb(Zr0.4Ti0.6)O3 thin-film capacitors by evaluation of time-dependent leakage current ( I-t ) and current-voltage ( I-V ) characteristics along with other dielectric properties. We derived an experimental formula to explain the leakage current at low field as a function of electric field, time and temperature. The ohmic-like current at low field depended on both the amount of excess Pb and thickness, which might be explained by the leakage current being governed by the amount of ionized point defects with an activation energy of about 0.5 eV.
The ohmic-like current which was decreased after DC stressing reverted back to its original value during the recovery time at high temperature. The 50% recovery time had an activation energy of 0.53 eV.
We proposed a plausible conduction model governed by trapping into ionized point defects.
Raman Scattering Study during the Dehydration Process of Polyacrylamide Gel
Authors: Kazuhiro Hara Kazuhiro Hara , Takeo Masuike Takeo Masuike , Atsushi Nakamura Atsushi Nakamura , Hirotaka Okabe Hirotaka Okabe , Nobuyasu Hiramatsu Nobuyasu Hiramatsu
Published: October 2002

Raman scattering experiment was carried out simultaneously with weight measurement during the dehydration process of polyacrylamide (PAAm) gel. Anomalies in the Raman spectrum were observed when the time dependence of the weight altered: around the first characteristic time, a shoulder emerged on the skirt of the low-lying diffusive central mode, and then around the second one, the shoulder changed into a peak (which resembled the “boson peak" commonly observed in glass) in addition to the disappearance of the central diffusive mode and an O–H stretching mode. The correlation between the spectral change and the time dependence of the weight demonstrated the effect of increase in the polymer chain interaction on the gel's dynamical properties.
Application of Lee's Plate Equations to Analysis of Spurious Vibrations of Rectangular AT-Cut Quartz Plates
Authors: Sekimoto Hitoshi , Tajima Daisuke , Watanabe Yasuaki , Akio Ishizaki Akio Ishizaki
Published: October 2002

Strip A
T-cut quartz resonators have recently been developed and are widely used in frequency applications because of their small size. Many spurious resonances can be supported in a rectangular A
T-cut plate. Therefore, analysis of the influence of both the X and Z
′ dimensions of the plate upon the spurious characteristics is necessary to design the strip resonators. However, it is very difficult to exactly solve three-dimensional equations of elasticity. The practical analysis of spurious characteristics has been carried out on the basis of approximate two-dimensional equations. In this paper, the applicability of Lee's two-dimensional equations to A
T-cut plates is examined. The resonant frequencies are calculated as a function of X-length, and are compared to Koga's experimental data. The result shows that new correction factors should be introduced in the equations in order to adjust the approximate values of wave numbers for the thickness-flexure waves propagating in X and Z
′ directions.
Etch Spirals Formed at Screw-Dislocation Sites on (111) Surface of Cu Crystal by Etching with Marukawa's Solution
Authors: Shigeo Sugawara Shigeo Sugawara
Published: October 2002

Dislocation etch pits were produced by etching of the (111) surface of Cu single crystal for 10-50 s at 280-300 K with Marukawa's solution ( FeCl3·6H2O-HCl-HBr). From electron microscopic observation of their replicas, it was found that spiral terraces often occurred at apices of the etch pits formed at screw-dislocation sites. The spiral terraces tended to occupy somewhat wider regions as etching time and temperature were increased.
Efficient Boron Incorporation in Hydrogenated Amorphous Silicon Films by a Novel Combination of RF Glow Discharge Technique and Heated Filament
Authors: Chattopadhyay S. , Das Debabrata , Sharma S. N. , Barua A K. , Banerjee Ratnabali , Kshirsagar S. T.
Published: October 2002

Boron doped hydrogenated amorphous silicon films were prepared by a novel method involving a combination of plasma chemical vapour deposition (PCVD) and a heated filament. The films were characterized by electrical conductivity measurements. A combination of Raman scattering experiment and infrared (IR) vibrational spectroscopy were performed to study the structural characteristics of the a-Si:H films. Higher conductivities were obtained for the films prepared under the heated filament in comparison to those for the films prepared away from it. It was inferred that growth conditions mainly governed by BH3 radicals led to highly conducting films. For conditions conducive to the production of more atomic hydrogen, SiH3 and BH2 radicals were expected to govern the growth and put the boron atoms into the inactive three-fold coordination.
System for Time-Resolved Observation of Impulsive Soft X-Ray Sources and Its Application to Plasma Focus Experiment
Authors: Takeshi Yanagidaira Takeshi Yanagidaira , Hiroshi Kurita Hiroshi Kurita , Katsumi Hirano Katsumi Hirano
Published: October 2002

A soft X-ray pinhole camera system for time-resolved, one-dimensional (1D) measurement of an impulsive source whose energy is in the range from 1 keV to 20 keV is developed. The system is based on the filtered pinhole camera. The pinhole image is divided into six channels in the direction of the electrode axis through slits and bundled fiber optics. Each channel is detected with a scintillator-photomultiplier combination. The temporal resolution of this system is 5.2 ns. The absolute sensitivity of the channel is ∼4.2×10-20 A/[photons/(mrad2·s)]. This system was successfully used to observe the time evolution of the soft X-ray source generated with a plasma focus device with a gas-puffed target.
Development of High Quality 1.36 eV Amorphous SiGe:H Alloy by RF Glow Discharge under Helium Dilution
Authors: Hazra Sukti , Middya Abdul Rafik , Rath Jatindra Kumar , Basak Subhashis , Swati Ray Swati Ray
Published: October 2002

The use of 1.35 eV amorphous silicon-germanium (a-SiGe:H) alloy as the second/third intrinsic layer along with 1.85 eV front layer in double/triple tandem solar cells is believed to be the best combination for the maximum power output for multijunction cells. In this study high quality low-band-gap (1.36 eV) a-SiGe:H alloy has been developed by RF glow discharge optimizing the deposition parameters and helium dilution of source gases. It has been observed that the structural, electronic properties and defect densities of alloy films developed under the deposition condition which is the transition from low-discharge-power to high-discharge-power regime, become optimum. In the present case this deposition condition is a combination of chamber pressure 0.8 Torr and RF power 60 mW/cm2. The properties of the alloy films developed under helium dilution improve and defect density decreases with the increase of deposition rate up to 120 Å/min. The 1.36 eV alloy film prepared under this condition has very low defect density ( 3.2×1016cm-3eV-1). The analysis of spectral response of Pd/a-SiGe:H Schottky barrier solar cells reveals that the hole transport properties improve due to increase of RF power from 15 to 60 mW/cm2and also due to increase of growth rate from 51 to 120 Å/min.
Waveform Dependence of Surge-handling Capability and Failure Analysis for Semiconductor Lightning Surge Protectors
Authors: Shimoda Yoshio , Hidetaka Satoh Hidetaka Satoh
Published: October 2002

The surge-handling capability of bi-directional thyristors is estimated for four kinds of surge waveforms: 8/20, 1.5/30, 15/100 and 10/1000 µ s. The surge-handling capability increases as the surge waveform becomes shorter. The failure modes of the device are classified into three modes: soft breakdown in the forward direction, a short mode in the forward direction and a bi-directional short mode. The occurrence rate of these modes depends on the applied surge waveforms. A melt hole with many cracks appears in the bi-directional short mode sample. Furthermore, electrode metal diffuses into the silicon substrate near the melt hole and the cracks. The diffused elements and their concentrations are identified by X-ray microanalysis. The likely cause of the melt hole and the diffusion of electrode metal is discussed considering temperature increase caused by surge energy.
Fabrication of Single Crystal of SmBa2Cu3O7-x by the Modified Top-Seeded Solution Growth Method in Low Oxygen Partial Pressure Atmosphere
Authors: Nakamura Masaru , Krauns Christian , Yuh Shiohara Yuh Shiohara
Published: October 2002

Single crystals of SmBa2Cu3O7-
x

(Sm123) have been successfully grown by a modified top-seeded solution growth (TSSG) method in 1% oxygen partial pressure atmosphere ( P(O2)=0.01 atm). Solid Sm2BaCuO5 (Sm211) solute and Ba-Cu-O solvent with Ba to Cu ratio of 3:5 were used in a Sm2O3 crucible. The Sm123 as-grown crystals were confirmed by X-ray structure analysis to have the SmBa2Cu3O7-
x

tetragonal structure, and the substitution of Sm ion to the Ba site was not detected within experimental accuracy. The transport properties of the grown crystals annealed in an oxygen gas flow were measured by the direct-current four-contact method, both in the ab-plane and along the c-axis. The superconductive transition temperature was 93 K and the transition width was 0.3 K.
Coherence Lengths of Matrices in NbTi Multifilamentary Wires
Authors: Tadahiro Akune Tadahiro Akune , Nobuyoshi Sakamoto Nobuyoshi Sakamoto
Published: October 2002

Proximity coupling between superconducting filaments in NbTi multifilamentary wires with Cu or Cu–0.5 wt investigated. Critical current densities of these matrices J
cp were estimated from measured twist-pitch dependence of magnetization. The upper critical field of matrix B
c2p is obtained by applying the scaling law to J
cp data. At T=4.0 K, B
c2p's of Cu matrix are 1.4–4.6 T for interfilamentary spacing d
N=0.20–0.59 µm and are larger than those of Cu–0.5 wt of the matrix ξ N estimated from the temperature dependence of B
c2p are 0.18–0.35 µm at T=4.2 K and show the clean limit characteristics, being proportional to T
-1 for Cu matrix wire. For Cu–0.5 wt T=4.2 K and show the dirty limit characteristics, proportional to T
-1/2.
Optical Characterization of Homogeneous Nematic Liquid Crystal Cells Based on the Liquid Crystal Continuum Model
Authors: Klaus Werner , Suzuki Yasushi , Tsuchiya Masahiro , Takeshi Kamiya Takeshi Kamiya
Published: October 2002

We formulated and applied a new algorithm based on the continuum theory of nematic liquid crystals to the characterization of the electrooptic response of homogeneous nematic liquid crystal cells. Appropriate selection of the device parameters ensures predictions of the electrooptic response which are in agreement with results of optical measurements to a precision of better than 1°. The effect of induced molecular twist and the limitations of decoupling between orthogonal polarizations are discussed.
Photoinduced Desorption of Ethanol Vapor from Ferrocene Solid Surface Monitored by Electrical Current Measurements
Authors: Chakraborty Aloke Kumar , Mallik Biswanath
Published: October 2002

Photoeffects in ferrocene solid samples with physically adsorbed ethanol vapor have been studied in detail at different sample temperatures by monitoring the change in the electrical current in sandwich cells of the material in powder form. The photoeffects in the ethanol-adsorbed ferrocene sample resulted in the decrease of measured currents in the sample cells. Such experiments have indicated photoinduced desorption of ethanol vapors from the ferrocene solid surface. Previously, desorption of adsorbed vapor in the dark from the ferrocene surface was studied by flushing with dry nitrogen gas, but photoinduced desorption of adsorbed vapors from ferrocene is reported here for the first time. The photoeffects in the vapor-adsorbed ferrocene sample cell were also studied using different vapors. It was found that the photoeffects in the vapor-adsorbed ferrocene sample were very selective, and photoinduced desorption was not observed in all the vapors studied. In some vapors, photoeffects in the vaporadsorbed state resulted in enhanced photocurrents of the material. The above results are discussed.
Scanning Tunneling Microscopy in Liquid on Geometrical Study of Cu(001) Surface
Authors: Yamada Yasusei , Arita Masashi , Masaaki Matsui Masaaki Matsui
Published: October 2002

Scanning tunneling microscopy (STM) in liquid was applied in order to prevent the influence of oxidation in air. Using 1,2,4-trichlorobenzene as a liquid for our STM studies, an image of a Cu (001) surface was taken with high reproducibility and an atom image was also obtained. The surface geometry of Cu (001) differently polished from bulk crystals was investigated.
Radiation Resistance of InP-Related Materials
Authors: Yamaguchi Masafumi , Takamoto Tatsuya , Ikeda Eiji , Kurita Hiroshi , Ohmori Masamichi , Ando Koshi , Vargas-Aburto Carlos
Published: October 2002

Irradiation effects of 1-MeV electrons on InP-related materials such as InP, InGaP and InGaAsP have been examined in comparison with those of GaAs. Superior radiation-resistance of InP-related materials and their devices compared to GaAs has been found in terms of minority-carrier diffusion length and properties of devices such as solar cells and light-emitting devices. Moreover, minority-carrier injection-enhanced annealing of radiation-induced defects in InP-related materials has also been observed.
Quasi-Two-Dimensional Model for Transverse Gas-Flow Laser Amplifier
Authors: Horioka Kazuhiko , Ishikawa Hiroshi , Mitsuo Nakajima Mitsuo Nakajima
Published: October 2002

Simulation procedures of transverse gas-flow laser amplifiers for power extraction are intrinsically two-dimensional. The power development in the laser amplifier, which should be fully coupled to the flow-field variables, depends on a number of hydrodynamic and geometric parameters. In order to simplify the optimization of them, a quasi-two-dimensional model is proposed.
Quasi-Phase-Matched Second-Harmonic Generation in a Periodic-Lens Sequence Waveguide with a Relatively Wide Wavelength-Tuned Width
Authors: Yamamoto Yukihiro , Yamaguchi Satoshi , Yamada Noriko , Ueda Kenji , Matsumoto Takahiro
Published: October 2002

The phase-matching characteristic of a quasi-phase-matched second-harmonic generation in a periodic-lens sequence waveguide on z-face KTiOPO4 (potassium titanyl phosphate) crystal was obtained by measuring, as a function of input optical wavelength, the intensity of frequency-doubled radiation. The fabricated waveguide is a kind of segmented domain-inverted waveguide of which grating pitch is 4 µ m. The phase-matching was observed in the fundamental wavelength region of 850-860 nm. The half-width of the peak around 854 nm is about 0.3 nm. The broadening of phase-matching in wavelength was explained using geometrical optics.
Effects of Amplitude and Phase Mismatching Errors in the Generation of a Kinoform for Pattern Recognition
Authors: Moreno Ignacio , Campos Juan , Gorecki Christophe , María J. Yzuel María J. Yzuel
Published: October 2002

A model to determine the influence of the phase and amplitude mismatching on the diffraction orders is proposed. The coupling between amplitude and phase in liquid crystal televisions (LCTV) is also considered. The effect on the impulse response of the nonlinearities is studied from experimentally determined amplitude and phase modulations. It is shown that even with these nonlinearities one of the orders corresponds to the impulse response of the kinoform. The proper diffractional order may be separated by adding phase codes. Experimental results of impulse responses and correlations are given for different configurations of the spatial light modulator (SLM).
Ferroelectric Behavior in Polyamides of m-Xylylenediamine and Dicarboxylic Acids
Authors: Murata Yukinobu , Tsunashima Kenji , Koizumi Naokazu
Published: October 2002

The ferroelectric properties were studied for polyamides consisting of m-xylylenediamine (MXD) and aliphatic dicarboxylic acids with the number of carbon atoms n=6 to 11, which were designated as nylon MXDn. Quenched samples of these polyamides exhibited the ferroelectric hysteresis loop with the remanent polarization P
r of 25-67 mCm-2 which decreased with increasing n. Strip-biaxial and biaxial drawing of nylon MXD6 caused the preferential orientation of molecular chains parallel to the direction of drawing and to the film surface, respectively, and increased the value of P
r. A reversible pyroelectric coefficient of 4 to 12 µC·m-2·K-1 was observed for nylons MXD6 and MXD7. The polarization was depolarized with increasing temperature and vanished at the glass transition temperature of the respective samples. The ferroelectricity of nylon MXDn is related to the amide groups aligned by the electric field in amorphous regions.
Surface Structure Analysis of Polyacrylate Thin Films
Authors: Katsuragawa Tadao , Chiba Eriko , Okada Kenji , Katsuhiko Tani Katsuhiko Tani , Hidenori Tomono Hidenori Tomono
Published: October 2002

The surface contact angles of poly(fluoroalkyl acrylate)s and poly(fluoroalkyl methacrylate)s vary with the cooling mode used after heat treatments. Grazing angle X-ray reflectivity measurement was applied to characterize the surface roughness of polyacrylate thin films on silicon wafers. Surface and interface roughnesses of polyacrylate thin films with large contact angles were measured as 0.7–1.2 nm, which are smaller than roughnesses (1.2–1.8 nm) with small contact angles. It was found that the ordering of side chains in polyacrylate thin films causes the surface to change the contact angles.
Dosage Control for Scanning Exposure with Pulsed Energy Fluctuation and Exposed Position Jitter
Authors: Suzuki Kazuaki , Ozawa Ken , Tanitsu Osamu , Masato Go Masato Go
Published: October 2002

Techniques of dosage control for scanning exposure are introduced and the accuracy of exposure dose achieved by these techniques are discussed. Analytical formulation of the dosage accuracy is performed for the first time under consideration of both pulsed energy fluctuation and exposed position jitter. Actual dosage accuracy was measured by adopting the simplest method. Experimental data from the exposure apparatus are shown and the effectiveness of derived formula for dosage error estimation is confirmed. Application for the exposure system is also discussed.
Hierarchy Optimization: A Means to Enhance Efficiency in E-Beam and Optical Lithography
Authors: K. Kalus Anja Rosenbusch , Hiroyuki Endo Hiroyuki Endo , Yasuki Kimura Yasuki Kimura , Akihiro Endo Akihiro Endo
Published: October 2002

In the e-beam lithography arena the proximity effect correction (PEC) of large la youts is still regarded as an insurmountable hurdle. The central processing unit (CPU) time for today's memory layouts (64 Mb) extends into weeks and file sizes into Gigabytes. In this paper a new concept for hierarchical data handling is introduced, the hierarchy reorganization. It paves the way for practical applications of very large layouts. The initial layout is reorganized according to correction-dependent criteria. The term hierarchy factor, which is a measure of the compaction of the given hierarchy tree, is introduced. This paper presents and explains the theoretical rules of the hierarchy optimization. The problems of hierarchical processing are demonstrated and solutions given. The solutions fall into two categories: the first one is common to all hierarchical processing, whereas the second one is application-specific. As an example, the hierarchical processing is applied to the proximity effect correction. Scanning electron microscope (SEM) images of memory chips are shown by comparing corrected with uncorrected wafers. Files sizes and processing times of all relevant processing steps in comparison with flat operation (not exploiting the hierarchy) are given.
New Ultra-High-Frequency Plasma Source for Large-Scale Etching Processes
Authors: Samukawa Seiji , Nakagawa Yukito , Tsukada Tsutomu , Ueyama Hiroyuki , Shinohara Kibatsu
Published: October 2002

A low temperature, uniform, high-density plasma is produced by an ultra-high-frequency (UHF) discharge using a new spokewise antenna. The plasma is uniform within ±5% over a diameter of 30 cm. The plasma density, 1×1011 cm-3, for low electron temperatures of 1.5-2.0 eV, is almost proportional to the UHF power even at a low UHF power. No magnetic field is needed to maintain a high-density plasma. Consequently, the plasma source is fairly simple and lightweight. The plasma source can accomplish a notch-free poly-Si etching profile with a high etching rate at a narrow space pattern of less than 0.3 µ m.
Etching for 0.15-µm-Level Patterns with Low Microloading Effect Using Beam Plasmas Generated by Gas Puff Plasma Sources
Authors: Oomori Tatsuo , Taki Masakazu , Nishikawa Kazuyasu , Hiroki Ootera Hiroki Ootera
Published: October 2002

Microloading effects in high-density plasmas, which typically appear as a difference in the etch rates between the outermost space and the inner space in a line-and-space (L&S) pattern, were investigated using numerical simulations of ion trajectories and ion fluxes incident on the patterned surfaces, taking into account the effects of electrical properties of the materials, plasmas flowing to a wafer and local charging on the patterned surface. The simulation results showed that decrease of the incident ion flux densities were particularly enhanced in the area around the outermost space in the L&S pattern. Moreover, the difference in the incident ion fluxes among the patterns was reduced with increase of the drift velocities of the plasmas. Moreover, experiments on etching of fine patterns on the scale of around 0.15 µ m were also performed using chlorine beam plasmas with high drift velocities generated by gas puff plasma sources. The etch rate of poly-Si stayed nearly constant with decrease of pattern sizes from 1.0 to 0.15 µ m for time-averaged pressure of <P
2>=0.2 m Torr in the specimen chamber.
Effect of Adding CO2 to CH4/H2 Mixture for InGaAs/GaAs Selective Reactive Ion Etching
Authors: Nihei Mizuhisa , Hara Naoki , Suehiro Haruyoshi , Shigeru Kuroda Shigeru Kuroda
Published: October 2002

InGaAs/GaAs selective reactive ion etching (RIE) by adding CO2 to a conventional CH4/H2 mixture was developed for the first time. We demonstrated that adding CO2 (7.8%) not only reduced polymer deposition during etching, but also achieved a significant increase in the In0.52Ga0.48As/GaAs selectivity from 2 to a maximum value of 6.5. We analized the etched surface with X-ray photoelectron spectroscopy (XPS) and found that the surface is polymer-rich after the CH4/H2 RIE, but it changes to G
a
2
O
3-rich after our CH4/H2/CO2 (7.8%) RIE.
From this result, we proposed a mechanism of the InGaAs/GaAs selective RIE.
Site Control of Metal Droplet Formation on CaF2 Surface Using a Focused Electron Beam
Authors: Kawasaki Koji , Uejima Kazuya , Kazuo Tsutsui Kazuo Tsutsui
Published: October 2002

Site-controlled Ga droplet formation using modification of fluoride surface by electron beam exposure was investigated as a new nanofabrication technique. A single line of Ga droplets of approximately 10 nm diameter on CaF2 was obtained using a linearly scanned focused electron beam. The fluctuation of their position from the centerline was found to be about ±20 nm, which was smaller than the estimated beam spot size. The mechanism of this site control effect was discussed using the model of potential on the CaF2 surface for Ga atom adsorption.
The Characteristics of Nitrogen Implanted Tungsten Film as a New Diffusion Barrier for Metal Organic Chemical Vapor Deposited Cu Metallization
Authors: Kwon Chul Soon , Kim Yong Tae , Choi Suk-Ki Min
Published: October 2002

Nitrogen-implanted W thin film (W-N+) has been proposed as a new diffusion barrier for Cu metallization. The crystalline phase of W-N+ thin film is transformed from polycrystalline to amorphous by the implantation of 1–3 ×1017 N+/cm2. However, if the dosage of N+ is less than 6 ×1016 N+/cm2 it is difficult to form the amorphous phase in the W film. The comparison of this amorphized W-N+ diffusion barrier with the conventional W film shows that the amorphized W-N+ diffusion barrier is very effective for preventing the Cu diffusion even at the annealing temperature of 800°C for 30 min, whereas the conventional W film cannot withstand annealing at 600°C for 30 min. Our result at 800°C for 30 min is a new and excellent record for preventing Cu diffusion.
Effects of Vacuum-Ultraviolet-Light-Induced Surface Reaction on Selective and Anisotropic Etching of Silicon Dioxide Using Anhydrous Hydrogen Fluoride Gas
Authors: Saito Yoji , Imai Hideo , Sugita Yoshihiro , Ito Takashi
Published: October 2002

Vacuum-ultraviolet (VUV) light induced etching of thermally grown silicon dioxide films was investigated near room temperature. We used synchrotron radiation as a VUV light source and anhydrous-hydrogen-fluoride as an etching gas. The silicon dioxide is etched only in the VUV light irradiated area, and etched selectively with respect to (100) oriented singlecrystalline silicon, which is not etched even under the irradiation. Moreover, we have found anisotropic etching with the patterned polycrystalline silicon etching mask. The ratio of the etch rate of SiO2 in the vertical direction compared to the horizontal direction of the substrate surface is about 30. From these results, the etching process is due to the photo-induced surface reaction. The excitation of the adsorbed AHF molecules or SiO2 surface would be a dominant process.
Nanoscale Evaluation of Structure and Surface Potential of Gated Field Emitters by Scanning Maxwell-Stress Microscope
Authors: Itoh Junji , Nazuka Yutaro , Inoue Takahito , Yokoyama Hiroshi , Kanemaru Seigo , Keizo Shimizu Keizo Shimizu
Published: October 2002

Both the structural and surface potential images of gated field emitters (GFEs) were measured using a scanning Maxwell-stress microscope (SMM) in air. Si cone-shaped and Mo disk-edge GFEs were measured. The experimental results clearly revealed differences in the surface potential for various materials and irregularities in the GFE structures which were too small to be found by conventional scanning electron microscope observations. It was also found that the surface potential of Si was rather flat even in the emitter tip apex.
Scratch Lithography of 10 nm Silicon Structures
Authors: Tada Tetsuya , Kanayama Toshihiko
Published: October 2002

A new lithography method, scratch lithography, is proposed for fabrication of silicon nanostructures. When a poly(methylmethacrylate) (PMMA) layer coated on a Si substrate is scratched by a needle, some of the PMMA molecules adhere to the substrate and cannot be removed by rinsing in acetone. The individual PMMA molecules thus fixed to the surface can be used as etch masks for electron cyclotron resonance microwave plasma etching (ECR etching) with SF6 at a low temperature (-130° C), which leads to formation of Si pillars of 10 nm diameter with a high aspect ratio (∼10). A 10-nm-wide line was also formed unintentionally, probably owing to the microroughness of the tip, suggesting that it may be possible to fabricate well-controlled nanostructures if the scratching tip is reduced to nanometer dimensions.
Transport Characterization of Schottky In-Plane Gate Al 0.3Ga 0.7As/GaAs Quantum Wire Transistors Realized by \twltibIn-Situ Electrochemical Process
Authors: Hiroshi Okada Hiroshi Okada , Tamotsu Hashizume Tamotsu Hashizume , Hideki Hasegawa Hideki Hasegawa
Published: October 2002

The low-temperature transport properties of the novel Al0.3Ga0.7As/GaAs Schottky in-plane gate (IPG) quantum wire transistor realized by the in-situ electrochemical process were studied. The device showed good field-effect transistor (FET) characteristics with excellent gate control and complete pinch-off. Quantized conductance in the units of 2e
2/h was clearly seen at 4 K. The first plateau persisted up to 40 K. Shubnikov-de Haas oscillation measurements showed an extremely weak dependence of the carrier density on the gate bias, indicating that the Schottky IPG controls the wire width without changing the sheet carrier density. Application of a magnetic field widened the conductance plateaus. Under harmonic approximation for the electrostatic confinement potentials, a subband spacing of \hbarω0=4–5 meV was obtained.
Characterization of Defect States Responsible for Leakage Current in Tantalum Pentoxide Films for Very-High-Density Dynamic Random Access Memory (DRAM) Applications
Authors: Lau Wai Shing , Tan Thiam Siew , Sandler Nathan P. , Page Barry S.
Published: October 2002

Defect states in tantalum pentoxide films grown by low-pressure metal-organic chemical vapor deposition on silicon wafers have been studied with Al/Ta2O5/p+-Si and Al/Ta2O5/n+-Si capacitor structures by the zero-bias thermally stimulated current technique. It was demonstrated that a shallow band of defect states is responsible for leakage current. The shallow band of defect states can be suppressed by low-temperature post metallization annealing, resulting in a reduction of leakage current for both positive gate bias and negative gate bias. However, the reduction in leakage current for positive gate bias is much stronger than that for negative gate bias.
Electrical Properties of Undoped and SnTe-Doped GaxIn1-xSb Molecular-Beam-Epitaxially Grown on GaAs
Authors: Chen Jenn-Fang , Jaw Shuenn-Haw , Cho Alfred Y.
Published: October 2002

Electrical properties of undoped and SnTe-doped GaxIn1-xSb on GaAs grown by molecular beam epitaxy are studied. In the studied composition x from 0.65 to 1, source SnTe is found to be an n-type dopant. The SnTe incorporation efficiency in GaxIn1-xSb is found to have no significant difference from SnTe in GaSb. The fitted ionized impurity concentrations for GaSb increases proportionally with the sample's donor concentrations, suggesting that the charged impurities are introduced through SnTe doping. On the other hand, for GaxIn1-xSb, the fitted ionized impurity concentrations do not vary with the total donor concentration. This suggests that material inhomogeneities or imperfections in GaxIn1-xSb may be the cause of mobility values which are lower than expected. In addition, the V/III beam equivalent pressure (BEP) ratio is found to critically influence the quality of the SnTe-doped ternary layers.
Intelligent Power IC with Partial SOI Structure
Authors: Yamaguchi Hitoshi , Himi Hiroaki , Fujino Seiji , Tadashi Hattori Tadashi Hattori
Published: October 2002

In the integration of power devices and control circuits, temperature rise caused by the heat dissipation of power devices and electric interference between power devices and control circuits are important problems. In this report, the following was demonstrated by using the partial silicon-on-insulator (SOI) structure with shielding layers. The partial SOI structure has the Si directly bonded areas where power devices are formed and SOI areas where control circuits are formed. Firstly, the temperature rise was reduced to about a half that in the complete SOI structure, and the latch-up occurrence in the control circuit was prevented by the insertion of shielding layers. Secondly, at the condition of 150° C and 16 V, the normal operation of an intelligent power IC consisting of multichannel power devices and a 1-bit microcomputer was accomplished.
Counter Doped N-Channel MOSFETs: Mobility Improvement and Reverse Short Channel Effect Enhancement
Authors: Ploeg Eric P. Ver , Noda Hiromasa , Umeda Kazunori , Nagai Ryo , Shin'ichiro Kimura Shin'ichiro Kimura
Published: October 2002

Counter doping implantation into the channel region is an effective and attractive technique for lowering the threshold voltage in n-channel metal oxide semiconductor field effect transistors (MOSFETs). There are several important advantages to using counter doping, including improved mobility. However, counter doping is shown here to also enhance the reverse short channel effect (RSCE), which is likely to become a more serious phenomenon in future generations of MOSFETs. This doping profile dependent behavior gives us some physical insight into the underlying mechanism responsible for the RSCE.
Effect of Water Vapor Processing on Microstructure and Superconducting Property of High-TcSuperconductors YBa2Cu3Oxand Bi1.85Pb0.35Sr1.90Ca2.05Cu3.05Oy
Authors: Zheng Xuguang , Yamaguchi Norihiro , Kuriyaki Hisao , Kazuyoshi Hirakawa Kazuyoshi Hirakawa
Published: October 2002

The effect of water vapor on the microstructure and superconducting properties of high-temperature (high-Tc) superconductors is investigated using polycrystalline YBa2Cu3Oxand Bi1.85Pb0.35Sr1.90Ca2.05Cu3.05Oy. The superconductors are sintered in atmospheres of H2O-O2and H2O-O2-Ar, respectively, instead of O2. Crystal growth, especially that around grain boundaries, is greatly enhanced by water-vapor processing. As a result, the transport critical current densityJcis considerably enhanced.
Low-Energy Electron Diffraction Analysis on Initial Stages of Ge Growth on Si(111)(1×1)-As and As-Desorbed Si(111)(1×1) Surfaces
Authors: Yasuda Haruyuki , Abe Daisuke , Hasegawa Shigehiko , Maehashi Kenzo , Hisao Nakashima Hisao Nakashima
Published: October 2002

We have investigated initial stages of Ge growth on Si(1×1)-As and As-desorbed (1×1) surfaces using spot profile analysis of low-energy electron diffraction and Auger electron spectroscopy. It is found that at 500° C, 2-dimensional (2D) islands are formed on both the Si(1×1)-As and the As-desorbed (1×1) surface. In contrast, Ge growth on the Si(1×1)-As surfaces at 300° C initially proceeds in the step flow mode, while for growth on the As-desorbed (1×1) surfaces at 300° C, much smaller 2D islands are formed. We demonstrated that the effect of As surfactant on surface diffusion is deeply related to the growth temperatures, and that As atoms enhance migration of Ge atoms at lower growth temperatures.
Relationship between Water Diffusivity of Dielectric Films and Accelerated Hot Carrier Degradation Caused by Water
Authors: Fukuda Kenji , Nakano Tadashi , Fujishima Masaaki , Mura Naomi , Tokunaga Kyoji , Tsuzumitani Akihiko , Ichinose Shuji
Published: October 2002

The relationship between the water diffusivity of dielectric films evaluated by use of D2O and the accelerated hot carrier degradation caused by water is presented. The diffusion coefficient of D2O in SiO2 film deposited by tetraethyl-orthosilicate-based plasma-enhanced chemical vapor deposition (P-TEOS) was about one-tenth that of SiH4-based (P-SiO) film. The P-TEOS film showed little capability of blocking water diffusion, while P-SiO film only 200 nm in thickness was sufficient to block the water diffusion as well as to suppress accelerated hot carrier degradation. Analyses of Fourier Transform Infrared Spectroscopy (FT-IR) and Secondary Ion Mass Spectrometry (SIMS) revealed that chemical species of Si-H and Si-NH included in P-SiO film efficiently trapped the diffusing water.
Improvement in Patterning Characteristics of GaAs Oxide Mask Used in In Situ Electron-Beam Lithography
Authors: López Máximo , Tanaka Nobuyuki , Matsuyama Isamu , Tomonori Ishikawa Tomonori Ishikawa
Published: October 2002

In situ electron-beam (EB) lithography is a technique used to process GaAs/AlGaAs semiconductor structures in an ultrahigh vacuum environment. In this technique a thin GaAs oxide layer is selectively formed on a clean GaAs surface by EB-stimulated oxidation under a controlled oxygen atmosphere, and it is then used as a mask material to pattern the underlying layers by Cl2 gas etching. We have found that by using slightly misoriented GaAs substrates both the EB dose and the oxygen pressure necessary to form a resistive oxide mask can be markedly reduced.
Comparison of Propagation Losses of Single-Mode GaAs/AlGaAs Waveguides in a Three- and a Five-Layer Structure
Authors: Young Tae Byun Young Tae Byun , Kyung Hyun Park Kyung Hyun Park , Sun Ho Kim Sun Ho Kim , Sang Sam Choi Sang Sam Choi , Tong Kun Lim Tong Kun Lim
Published: October 2002

Single-mode GaAs/AlGaAs ridge waveguides with a three- and a five-layer heterostructure have been designed using an effective index method and fabricated using a metalorganic chemical vapor deposition (MOCVD) technique and the chemical wet etching method. The propagation loss was measured by the Fabry-Perot resonance method and sequential cleaving experiment at 1.31 µm wavelength. The propagation loss is as low as 0.62 dB/cm for waveguides with a double heterostructure. For five-layer waveguides with a W-shaped index profile, it is 0.23 dB/cm, comparable to the lowest loss value of semiconductor waveguides yet reported. Therefore the W-type waveguides provide a useful basis for low-loss guided-wave devices for integrated optoelectronics.
Time Variation of Plasma Properties in a Pulse-Time-Modulated Electron Cyclotron Resonance Discharge of Chlorine Gas
Authors: Mieno Tetsu , Samukawa Seiji
Published: October 2002

Time dependence of plasma parameters in a pulse-time-modulated electron cyclotron resonance plasma of Cl2and Ar gases is measured. It is found that Cl2plasma produces a large quantity of negative ions during afterglow and that decay times of electron density, electron temperature and sheath potential of Cl2plasma are much smaller than those of Ar plasma. The results suggest that the pulse modulation of Cl2plasma changes the flow of charged particles through the sheath region to the substrate surface and enables us to improve highly selective and charge-free poly-Si patterning.
Atomically Resolved InP(110) Surface Observed with Noncontact Ultrahigh Vacuum Atomic Force Microscope
Authors: Ueyama Hitoshi , Ohta Masahiro , Sugawara Yasuhiro , Seizo Morita Seizo Morita
Published: October 2002

Atomic resolution imaging of the cleaved InP(110) surface was demonstrated using an ultrahigh vacuum atomic force microscope (UHV-AFM) in a noncontact mode, for the first time. The force gradient acting on the tip was detected by the frequency modulation (FM) detection method. A rectangular lattice could be clearly resolved. Atomic defects were also clearly and reproducibly observed. These results suggest that the noncontact UHV-AFM has potential for imaging III-V compound semiconductor surfaces with true atomic-scale lateral resolution.
A New Method to Monitor the Process of Laser Ablation: Measurements on the Current Induced by Ablated Particles
Authors: Quan Zhuang Quan Zhuang , Katsumi Tanaka Katsumi Tanaka , Ryohei Nakata Ryohei Nakata
Published: October 2002

An induced current signal due to the ejection of charged particles in the laser ablation process was observed. The signal displayed an ablation threshold which was in accord with the ablation threshold measured by mass spectrometry, and showed a nonlinear relationship of its intensity till much higher laser fluences. The mechanism of the occurrence of the signal and its potential applications are discussed.
Magnetically Excited Plasma Oxidation of Si
Authors: Hideaki Nagasawa Hideaki Nagasawa , Hiroyasu Kitajima Hiroyasu Kitajima , Daisuke Kitayama Daisuke Kitayama , Yoshinaga Okamoto Yoshinaga Okamoto , Hideaki Ikoma Hideaki Ikoma
Published: October 2002

High-quality Si dioxide was successfully grown at room temperature using a magnetically excited plasma oxidation technique. Helicon waves were probably excited under the growth conditions used. Excellent capacitance-voltage characteristics were obtained after annealing of these oxide films in oxygen ambient for 15 min at 300°–500°C. The growth rate was somewhat low. However, the film thickness increased substantially with annealing. X-ray photoelectron spectroscopic studies indicated that high-quality Si oxides without suboxides were grown even at room temperature.
Properties of Basal-Plane-Faced Tilt Boundary Josephson Junction in YBCO Films
Authors: Ishimaru Yoshihiro , Hayashi Kunihiko , Youichi Enomoto Youichi Enomoto
Published: October 2002

We have investigated a Josephson junction formed at a boundary of an a-axis oriented plate surrounded by c-axis oriented grains. The YBCO c-axis oriented film with few a-axis oriented grains have been fabricated on a MgO(100) substrate by pulsed laser deposition. TEM observation shows clear lattice image along the grain boundary. Typical RSJ type I-V curves are observed with I
c
R
n of 1.37 mV and J
c of 4.4×104 A/cm2 at 4.2 K.
In addition, Shapiro steps under microwave irradiation and Fraunhofer-like diffraction pattern of I
c under magnetic field are observed, indicating that the boundary works as Josephson junction. Temperature dependence of the diffraction pattern under a magnetic field is different from one of conventional junctions which is described by penetration depth characteristics. This property is explained qualitatively on the basis of asymmetric electrodes structure.
Second-Order Hyperpolarizabilities of Aromatic Carboxylates without Visible Absorption
Authors: Duan Xuan-Ming , Kimura Tatsumi , Okada Shuji , Oikawa Hidetoshi , Matsuda Hiro , Kato Masao , Hachiro Nakanishi Hachiro Nakanishi
Published: October 2002

The second-order hyperpolarizabilities (β) of aromatic carboxylates were evaluated by the hyper Rayleigh scattering method at 1.064 µ m and semiempirical molecular orbital calculation. The β values of methyl methoxybenzoate and its dimer in methanol solution were measured to be 22 and 49×10-30 esu, respectively, which are about 0.6 and 1.3 times that of p-nitroaniline. The calculation of β and dipole moment (µ ) of the methyl methoxybenzoate oligomers revealed an almost linear increase of these values with increasing number of repeating units up to trimers. Since the oligomers have a short cutoff wavelength of about 300 nm as well as large β and µ, these compounds are concluded to be promising chromophores for second-order nonlinear optics.