bluuebunny/crossref_metadata_2025 huggingface dataset:
Control of Nucleation and Solidification Direction of Polycrystalline Silicon by Excimer Laser Irradiation
Authors: Hara Akito , Sasaki Nobuo
Published: October 2002

The nucleation site and solidification direction of polycrystalline silicon were
controlled by excimer laser crystallization. The sidewall and the top of the
amorphous silicon island, which includes a gradually narrowing region, were
covered with a thick layer of polycrystalline silicon, and single-shot irradiation
was performed from the back surface. The formation of only one nucleus was
observed in a gradually narrowing region of width two times that of the lateral
growth distance. Solidification from the nucleus toward a narrower width region
was then effected in a region 2 µm in width and 3 µm in length. The growth
mechanism is explained on the basis of the temperature gradient formed
by the covering of the polycrystalline silicon and the gradually
narrowing structure.
Nondestructive Visual Search for Fossils in Rock Using X-Ray Interferometry Imaging
Authors: Ando Masami , Chen Junyuan , Hyodo Kazuyuki , Mori Koichi , Sugiyama Hiroshi , Xian Dingchang , Zhang Xiaowei
Published: October 2002

Fossils inside rock have been clearly visualized utilizing an X-ray interferometer. Two types of clear images are obtained, one involves phase contrast in interference beams and the other involving refraction contrast in forward-diffracted beams. 2D monochromatic synchrotron X-ray radiation with a beam size of 10 mm×10 mm and a photon energy of 35 keV was used. Using a stereographic pair of X-ray images, the locations of fossils inside rock can easily be determined with a precision of 0.5 mm. This method can be a powerful nondestructive tool in the fields of paleontology and paleobiology to discover and locate fossils and trace fossils inside rock.
Stabilization of Oxygen Diffusion in Ga-Doped YBa2Cu3O7-δ Thin Films Observed by Spectroscopic Ellipsometry
Authors: Sugai Satoshi , Matsukawa Yasunari , Shimosato Keiji , Oda Shunri
Published: October 2002

We have investigated growth monitoring and the deoxidation process of Ga-doped YBa2Cu3O7-δ (YBCO) thin films using spectroscopic ellipsometry. The imaginary part of the pseudodielectric function, ε

i
, at 4.1 eV is very sensitive to the structure of YBCO. By monitoring the difference between undoped and Ga-doped YBCO during deposition we can evaluate the content of Ga substituted for Cu(I) in YBCO. Furthermore, monitoring of ε

i
at 4.1 eV during deoxidation indicates that the oxygen in the CuO chain of Ga-doped YBCO is more stable than that of undoped YBCO.
Correlation between Barrier Width, Barrier Height, and DC Bias Voltage Dependences on the Magnetoresistance Ratio in Ir–Mn Exchange Biased Single and Double Tunnel Junctions
Authors: Saito Yoshiaki , Amano Minoru , Nakajima Kentaro , Takahashi Shigeki , Sagoi Masayuki , Inomata Koichiro
Published: October 2002

Dual spin-valve-type double tunnel junctions (DTJs) of Ir–Mn/CoFe/AlO
x
/Co90Fe10/AlO
x
/CoFe/Ir–Mn and spin-valve-type single tunnel junctions (STJs) of Ir–Mn/CoFe/AlO
x
/CoFe/Ni–Fe were fabricated using an ultrahigh vacuum sputtering system, conventional photolithography and ion-beam milling. The STJs could be fabricated with various barrier heights by changing the oxidization conditions during deposition and changing the annealing temperature after deposition, while the AlO
x
layer thickness remained unchanged. There was a correlation between barrier width, height estimated using Simmons' expressions, and dc bias voltage dependence on the MR ratio. The V
B dependence on the tunneling magnetoresistance (TMR) ratio was mainly related to the barrier width, and the decrease in the TMR ratio with increasing bias voltage is well explained, taking into account the spin-independent two-step tunneling via defect states in the barrier, as a main mechanism, at room temperature. Under optimized oxidization and annealing conditions, the maximum TMR ratio at a low bias voltage, and the dc bias voltage value at which the TMR ratio decreases in value by half (V
1/2) were 42.4% and 952 mV in DTJs, and 49.0% and 425 mV in STJs, respectively.
Photonic Band Gap in Anodic Porous Alumina with Extremely High Aspect Ratio Formed in Phosphoric Acid Solution
Authors: Masuda Hideki , Ohya Masayuki , Nishio Kazuyuki , Asoh Hidetaka , Nakao Masashi , Nohtomi Masaya , Yokoo Atsushi , Tamamura Toshiaki
Published: October 2002

Two-dimensional (2D) photonic crystals were fabricated using anodic porous alumina with a highly ordered air-hole array of triangular lattice with a high aspect ratio of over 200. The transmission properties of the obtained ordered air-hole array in the alumina matrix exhibited a stop band in the spectrum which corresponds to the band gap in 2D photonic crystals.
1.15 µm Lasing Operation of Highly Strained GaInAs/GaAs on GaAs (311)B Substrate with High Characteristic Temperature (T0=210 K)
Authors: Nishiyama Nobuhiko , Arai Masakazu , Shinada Satoshi , Miyamoto Tomoyuki , Koyama Fumio , Iga Kenichi
Published: October 2002

We have demonstrated a λ=1.15 µm highly strained GaInAs/GaAs quantum well laser grown on GaAs (311)B substrate for the first time. The threshold current density of double quantum well lasers was as low as 410 A/cm2 and the characteristic temperature in the operating temperature range from 10°C to 70°C was 210 K. Wavelength extension to near 1.3 µm and improved polarization stability of vertical-cavity surface-emitting lasers (VCSELs) formable on GaAs substrate can now be expected.
Third-Order Hyper-Rayleigh Scattering in an Azobenzene Dye Solution
Authors: Yamada Toshiki , Mashiko Shinro
Published: October 2002

We report the first observation of third-order hyper-Rayleigh scattering superimposed on three-photon-induced fluorescence in a chloroform solution of the azobenzene dye Disperse Red 1. Cubic dependence of the intensity of the scattered third-harmonic light on the intensity of the fundamental light was observed. The intensity of the scattered third-harmonic light was linearly proportional to the number density of the dye. The estimated value of third-order polarizability γ3333 of the dye under resonance conditions was 8.7×10-33 esu.
Fullerene-Derivative Nanocomposite Resist for Nanometer Pattern Fabrication
Authors: Ishii Tetsuyoshi , Tamamura Toshiaki , Shigehara Kiyotaka
Published: October 2002

A nanocomposite resist system that incorporates a fullerene derivative into a conventional positive-type electron-beam resist, ZEP520, is examined. Because of the enhanced solubility of the derivative, the system exhibits a minimal decrease of sensitivity even at an incorporation content of 50 wt% and enables the fabrication of 50 nm patterns with a line dose of 0.39 nC/cm. At higher contents, however, the derivative is not as effective as fullerene C60 or C70 in improving dry-etching resistance because of the aggregation of the derivative molecules, which is probably due to the uniqueness of the derivative used and will be avoided by appropriate molecular design.
Activation Energy, Capture Cross Section, and Emission Frequency of the Trap Level in Unintentionally Doped n-Type GaN Epilayers Grown on Sapphire Substrates in a Nitrogen-Rich Atmosphere
Authors: Jung Woon Hyung , Kang Tae Won , Kim Tae Whan , Chung Kwan Soo
Published: October 2002

Thermally stimulated current (TSC) measurements of unintentionally doped n-type GaN epilayers grown on sapphire substrates in a nitrogen rich atmosphere using plasma-assisted molecular beam epitaxy were carried out to investigate the physical properties of trap levels in GaN films. The TSC spectra showed one dominant trap level at 150 K, and the activation energy, the capture cross section, and the emission frequency of the trap level were 0.265 eV, 2.58×10-21 cm2, and 3.17×105 s-1, respectively. These results can help clarify the potential applications of GaN epilayers in optoelectronic devices in the blue region of the spectrum.
Hard Magnetic Properties of (001) Oriented L10-FePd Nanoparticles Formed at 773 K
Authors: Sato Kazuhisa , Bian Bo , Hirotsu Yoshihiko
Published: October 2002

Two-dimensionally dispersed 10 nm-sized Fe/Pd and Fe/Pt particles (nanoparticles) with orientations have been fabricated with the same condition using an electron-beam evaporation technique. Heat treatments at temperatures above 773 K lead to a formation of L10-type (CuAu I-type) FePd and FePt ordered alloy particles with sizes as small as 10 nm. In the case of FePt nanoparticles, coercivity started to increase at 873 K, while in the case of FePd at 773 K. Moreover, in most of the FePd nanoparticles, their c-axes oriented normal to the film plane and the perpendicular coercivity reached as high as 1.2 kOe after annealing at 773 K for 1 h. This method can be applied to fabricate ultra-high density magneto-optical or vertical recording media under low annealing temperatures for the L10-structure formation especially in the Fe-Pd system.
An Oxide Single Crystal with High Thermoelectric Performance in Air
Authors: Funahashi Ryoji , Matsubara Ichiro , Ikuta Hiroshi , Takeuchi Tsunehiro , Mizutani Uichiro , Sodeoka Satoshi
Published: October 2002

An oxide single-crystalline whisker with high thermoelectric properties at temperatures (T) higher than 600 K in air has been discovered. This whisker is assigned to Ca2Co2O5 phase (abbreviated to Co-225 whiskers) and has a layered structure in which Co–O layers of two different kinds alternate in the direction of the c-axis. Seebeck coefficient of the whiskers is higher than 100 µV·K-1 at 100 K and increases with temperature up to 210 µV·K-1. Temperature dependence of electric resistivity shows a semiconducting-like behavior. These results indicate that the electric carriers are transported via hopping conduction. Using thermal conductivity of a Co-225 polycrystalline sample, figure of merit (Z
T) of the Co-225 whiskers is estimated 1.2–2.7 at T≥873 K. This compound is characterized with regard to low mobility and high density of carriers, which contradicts the conventional materials with high thermoelectric properties.
Oxidation Simulation of (111) and (100) Silicon Substrates Based on the Interfacial Silicon Emission Model
Authors: Uematsu Masashi , Kageshima Hiroyuki , Shiraishi Kenji
Published: October 2002

Silicon oxidation of (111) and (100) substrates is simulated based on the interfacial silicon emission model. Large silicon emission from the interface, which governs the oxidation rate at the interface, plays an important role in determining the substrate-orientation dependence. The simulation is done by changing only the rate of Si-atom emission from the interface; the emission rate for (111) is about 0.4 times that for (100). Using a unified set of parameters, the whole range of oxide thickness is fitted in a wide range of oxidation temperatures (800–1200°C) and oxygen pressures (1–20 atm).
Optical and Electrical Characteristics of CO2-Laser-Treated Mg-Doped GaN Film
Authors: Lai Wei-Chih , Yokoyama Meiso , Chang Shoou-Jinn , Guo Jan-Dar , Sheu Chia-hon , Chen Tsung-yu , Tsai Wen-Chung , Tsang Jian-Shihn , Chan Shih-Hsiung , Sze Simon M.
Published: October 2002

This work investigates the optical and electrical characteristics of CO2-laser annealed Mg-doped GaN films to activate Mg-doped p-type GaN films. Results obtained from the CO2 laser annealing investigation were similar to those of thermal annealing or low energy electron beam irradiation (LEEBI) treatment to activate the Mg-doped p-GaN films. The room-temperature photoluminescence (PL) intensity of the blue emission of the Mg-doped GaN film after 10 W laser annealing was approximately ten times stronger than that of the as-grown film. The resistivity of the Mg-doped GaN film decreased from 105 Ω·cm to 2–3 Ω·cm as the laser annealing power rose above 6 W. The hole concentration of Mg-doped GaN film was approximately 1×1017 cm-3 when the laser annealing power was 7.5 W.
Device Linear Improvement Using SiGe/Si Heterostructure Delta-Doped-Channel Field-Effect Transistors
Authors: Chien Pei Wei , Wu San Lein , Chang Shoou Jinn , Wang Yan Ping , Miura Hidetoshi , Shiraki Yasuhiro
Published: October 2002

Results of boron delta-doped-channel (DDC) field-effect transistors fabricated on Si0.7Ge0.3/Si strained-layer heterostructures grown by solid-source molecular beam epitaxy (SSMBE) are reported. A device with a 1×100 µm2 gate exhibits an extrinsic transconductance as high as 22 mS/mm. Due to the absence of parallel conduction effects under high-current-level operation in this device, as compared to a modulation-doped structure, a wide and flat range of uniform g
m distribution of 4.5 V together with a high gate-to-drain breakdown voltage (>25 V) and high current density of 120 mA/mm is obtained at room temperature, which is expected to provide an additional degree of freedom for Si-based device applications.
A High-Speed Josephson Latching Driver for a Superconducting Single-Flux-Quantum System to Semiconductor System Interface
Authors: Harada Naoki , Yoshida Akira , Yokoyama Naoki
Published: October 2002

We have used a 2.5 kA/cm2 standard Nb junction technique to fabricate superconducting driver circuits and here present experimental results. The driver consists of 16 resistively shunted stacked junctions and an input junction. It is capable of converting a single flux quantum pulse to 10 mV at 3 GHz, and 7 mV at 10 GHz. The driver is thus a potential high-speed output interface between superconducting single-flux-guantum (SFQ) systems and room-temperature semiconductor systems.
Magnetic Recording on Magneto-Optical Media Using Merge Type Giant Magneto-Resistive Head
Authors: Matsumoto Koji , Ozaki Kazuyuki , Chekanov Albert , Tagawa Ikuya , Shono Keiji
Published: October 2002

TbFeCo media for perpendicular magnetic recording were developed by employing a NiP underlayer that controls the magnetic properties of a TbFeCo magnetic layer. Dynamic write-read characteristics were examined using a conventional merge-type giant magneto-resistive (GMR) head originally designed for longitudinal magnetic recording. A clear magnetic transition of 450 kFCI (kilo Flux Change per Inch), a high media signal-to-noise ratio (SNR), and acceptable overwrite properties were obtained by optimizing the magnetic properties of TbFeCo films. The thermal stability of a written bit in TbFeCo film is sufficient for practical application.
Photon-Number Squeezing in a Light-Emitting Diode Driven by a Constant-Voltage Source: Pump Regulation by the Non-Coulombic Effect
Authors: Hiroyuki Sumitomo Hiroyuki Sumitomo , Masamichi Yamanishi Masamichi Yamanishi , Yutaka Kadoya Yutaka Kadoya
Published: October 2002

Experimental results on squeezing of photon-number fluctuations of a p-n junction light-emitting diode (LED) driven by a constant-voltage source are demonstrated together with physical mechanisms responsible for the squeezing. The observed squeezing at room temperature is discovered to be explained not by the conventional collective Coulomb blockade model but by our new model which includes the effect of the microscopic nonlinear backward-pump process, which can work even in the constant-voltage operation.
New Red Electroluminescent Devices Using Tris(2,2′-bipyridine) Ruthenium (II) Hexafluorophosphate as Emitter
Authors: Li Minrun , Yu Junsheng , Chen Zhijian , Totani Kenro , Watanabe Toshiyuki , Miyata Seizo
Published: October 2002

A new ruthenium complex, tris (2,2′-bipyridine) ruthenium (II) hexafluorophosphate [Ru(bpy)3(PF6)2], was synthesized. Two single-layer electroluminescent devices with an indium-tin oxide (ITO) anode and a Mg cathode were fabricated, one with the newly synthesized material and the other with the known tris (2,2′-bipyridine) ruthenium (II) chloride [Ru(bpy)3Cl2] as emitting materials. The efficiency of the electroluminescent device with the new emitting material [Ru(bpy)3(PF6)2] was found to be much higher than that with [Ru(bpy)3Cl2]. The efficiency of the devices is influenced by the anion size of the emitting materials.
Effects of Chamber Pressure on Composition and Electrical Properties of Zr-Modified (Ba1-x, Srx)TiO3 Thin Films Grown by Sputtering
Authors: Sang-Shik Park Sang-Shik Park , Soon-Gil Yoon Soon-Gil Yoon
Published: October 2002

Zr-modified (Ba1-x
, Sr
x
)TiO3 thin films as capacitors for high density dynamic random access memory were deposited by r.f. magnetron sputtering as a function of chamber pressure. The Zr/Ti ratio of films increased significantly with decreasing chamber pressure and this variation affected the microstructure and surface roughness of the films. The dielectric constant of the films increased due to the decrease of Zr when chamber pressure was increased. The (Ba1-x
, Sr
x
)(Ti1-y
, Zr
y
)O3 thin films showed a dielectric constant of 380∼525 at 100 kHz. The leakage current exhibited a smaller value as chamber pressure decreased and the leakage current density of films with various Zr contents was order of the 10-7–10-9 A/cm2 at 200 kV/cm.
New Liquid-Crystal Materials for Active Matrix Displays with Negative Dielectric Anisotropy and Low Rotational Viscosity
Authors: Klasen Melanie , Bremer Matthias , Tarumi Kazuaki
Published: October 2002

Liquid-crystal single materials with large negative dielectric anisotropies, high clearing temperatures and extremely low rotational viscosities were identified. Using these materials, the rotational viscosities for a broad range of mixture specifications were significantly reduced. Thus, these mixtures are found suitable for the improvement of the switching time of liquid-crystal displays using vertical alignment (VA) modes.
Metalorganic Chemical Vapor Phase Epitaxy of Crack-Free GaN on Si (111) Exceeding 1 µm in Thickness
Authors: Dadgar Armin , Bläsing Jürgen , Diez Annette , Alam Assadullah , Heuken Michael , Krost Alois
Published: October 2002

We present a simple method for the elimination of cracks in GaN layers grown on Si (111). Cracking of GaN on Si usually occurs due to large lattice and thermal mismatch of GaN and Si when layer thicknesses exceeds approximately 1 µm. By introducing thin, low-temperature AlN interlayers, we could significantly reduce the crack density of the GaN layer. The crack density is practically reduced to zero from an original crack density of 240 mm-2 corresponding to crack-free regions of 3×10-3 mm2. Additionally for the GaN layer with low temperature interlayers, the full width at half maximum X-ray (2024) rocking curve is improved from approximately 270 to 65 arcsec.
Growth of Epitaxial ZnO Thin Film by Oxidation of Epitaxial ZnS Film on Si(111) Substrate
Authors: Miyake Aki , Kominami Hiroko , Tatsuoka Hirokazu , Kuwabara Hiroshi , Nakanishi Yoichiro , Hatanaka Yoshinori
Published: October 2002

The growth of an epitaxial ZnO thin film on a Si substrate by oxidation of an epitaxial ZnS film is a novel method and we are reporting it for the first time. The merits of using the Si substrate are to make the driving voltage of light-emitting diodes (LEDs) lower and the cost of the LEDs less expensive than that using a sapphire substrate. In this study, the epitaxial ZnO thin film could be successfully grown on the Si substrate. The epitaxial films showed a strong near-ultraviolet emission with a peak at around 3.32 eV at room temperature under 325 nm excitation.
Properties of Ruthenium Films Prepared by Liquid Source Metalorganic Chemical Vapor Deposition Using Ru(EtCp)2 with Tetrahydrofuran Solvent
Authors: Nabatame Toshihide , Hiratani Masahiko , Kadoshima Masaru , Shimamoto Yasuhiro , Matsui Yuichi , Ohji Yuzuru , Asano Isamu , Fujiwara Tetsuo , Suzuki Takaaki
Published: October 2002

Pure Ru thin films were deposited on SiO2/Si substrates, using Ru(C2H5C5H4)2 with C4H8O (THF) solvent, by liquid source metalorganic chemical vapor deposition. The Ru single phase could be obtained under all growth conditions. For temperatures below 350°C, deposition occurred in the surface reaction region because the kinetics increased exponentially as a function of the deposition temperature with an activation energy of about 1.1 eV. Above 350°C, the deposition was controlled by the mass transport process. Step coverage for the Ru thin films deposited at 300–325°C with an aspect ratio of 3.3 was about 100%. The Ru thin films grown at 325°C showed a dense and smooth microstructure and had resistivities of <100 µΩ·cm.
Real-Time, Micrometer Depth-Resolved Imaging by Low-Coherence Reflectometry and a Two-Dimensional Heterodyne Detection Technique
Authors: Masahiro Akiba Masahiro Akiba , Kin Pui Chan Kin Pui Chan , Naohiro Tanno Naohiro Tanno
Published: October 2002

A novel two-dimensional heterodyne detection technique is demonstrated for real-time, cross-sectional imaging using optical coherence domain reflectometry without lateral scanning. The present technique, which is based on a frequency synchronous detection scheme, enables parallel heterodyne detection with an imager such as a charge coupled device camera. Full-field, micrometer-scale, depth-resolved images acquired at a rate of 10 frame/s are presented.
New Measurement Method of Complex Electrophoretic Mobility of Charged Colloids by Quasi-Elastic Light Scattering
Authors: Daisuke Mizuno Daisuke Mizuno , Yasuyuki Kimura Yasuyuki Kimura , Reinosuke Hayakawa Reinosuke Hayakawa
Published: October 2002

A new measurement method of complex electrophoretic mobility µ* of colloidal particles in suspension was developed using a heterodyne technique of quasi-elastic light scattering under a sinusoidal electric field. The influence of diffusion was removed by squaring the time-domain signal of scattered light and we succeeded in accurate and highly sensitive measurement of µ* in a wide frequency range for the first time. The frequency dependence of µ* of latex particles was measured up to 50 kHz by this method. The relaxation of mobility due to anomalous double-layer polarization was observed above 1 kHz in the obtained spectrum.
Superior Properties of Cesium Triborate CsB3O5 for 194 nm Light Generation with Nd:Y3Al5O12 Laser
Authors: Kagebayashi Yoshio , Deki Kyoichi , Morimoto Yukihiro , Miyazawa Shintaro , Sasaki Takatomo
Published: October 2002

We compared the 194 nm output energy of a type-I phase-matched CsB3O5 (CBO) with that of a type-II phase-matched CsLiB6O10 (CLBO) crystal. Using CBO crystal, we generated deep ultraviolet light at 194 nm by sum-frequency conversion of 2 µm band light and 213 nm light at a conversion efficiency of 2.2%. We found that the conversion efficiency obtained using CBO was 2.7 times higher than that obtained using CLBO at a maximum input of fundamental light. We concluded that CBO is a superior nonlinear optical crystal for generating 194 nm light with Nd:Y3Al5O12 lasers because of its larger spectral and angular acceptance.
Negative-Capacitance Effect in Forward-Biased Metal Oxide Semiconductor Tunnel Diodes (MOSTD)
Authors: Matsumura Mieko , Hirose Yutaka
Published: October 2002

A negative capacitance (NC) effect in metal oxide
semiconductor tunnel diodes (MOSTD) is reported. The phenomenon is
observed with forward-biased minority carrier type MOSTDs with low
measurement frequencies. Enhancements of the effect with the higher
substrate resistivity and with the increase of the minority carrier
injection indicate that the effect arises from conductivity
modulation in the substrate. The equivalent circuit consisting of a
parallel “inductor”-resistor pair in series with the ordinary
equivalent circuit of a MOSTD biased in accumulation is found to be
a good first order representation of the measured impedance spectra.
Correlation of Matched Electric Fields in Four-Level Atoms via Electromagnetically Induced Transparency
Authors: Masahiro Takeoka Masahiro Takeoka , Fumihiko Kannari Fumihiko Kannari
Published: October 2002

We investigated the matching of two continuous fields in a closed four-level system quantum mechanically. When the atomic coherence is prepared in the dressed state by two strong external coupling fields, fluctuations of phase and amplitude between the two probe fields are selectively absorbed, while these fields are mainly transparent in the media. Such selective absorption establishes the phase and amplitude correlation between the two weak probe fields over a wide range of frequencies. However, the correlation remains limited by the standard quantum limit, because of the addition of the anti-phase atomic noise during the four-wave mixing process.
Defect Control for Large Remanent Polarization in Bismuth Titanate Ferroelectrics –Doping Effect of Higher-Valent Cations–
Authors: Noguchi Yuji , Miwa Ichiro , Goshima Yu , Miyayama Masaru
Published: October 2002

The effects of concentration and distribution of defects controlled by quenching and doping of higher-valent cations on the ferroelectric properties of dense Bi4Ti3O12 ceramics were investigated. The remanent polarization (P
r) of non-doped ceramics quenched from 800°C (above the Curie temperature) was twice as large as those of samples subjected to slow cooling to 25°C and quenched from 600°C (below the Curie temperature). These results imply that domain pinning by defects dominates the polarization properties. The incorporation of vanadium and tungsten into Ti site significantly reduced the influence of domain pinning, resulting in a very large 2P
r of over 40 µC/cm2.
Phenomenological Theory on Si Layer-by-Layer Oxidation with Small Interfacial Islands
Authors: Kenji Shiraishi Kenji Shiraishi , Hiroyuki Kageshima Hiroyuki Kageshima , Masashi Uematsu Masashi Uematsu
Published: October 2002

We theoretically investigate the mechanism of Si layer-by-layer oxidation by taking into account interfacial Si emission. Based on the free energy expression, which includes the oxidation-induced strain within the elastic continuum theory, we simulated the oxidation. Initially, oxidation occurs at the step edge of the interface. However, it stops because of the accumulated strain, and the oxidation at the terrace region begins. As a result, many small islands form at the interface. After their formation, the Si emission occurs to release the interfacial strain. Accordingly, oxidation at the step edges of the small islands becomes possible due to the strain release by Si emission. This process is qualitatively in good agreement with recent observations of Si layer-by-layer oxidation concurrent with the formation of many small oxide islands.
Effect of Substrate Orientation on Photoluminescence of GaNAs
Authors: Moto Akihiro , Takahashi Mitsuo , Takagishi Shigenori
Published: October 2002

The effect of substrate orientation on photoluminescence (PL) properties has been explored for GaNAs grown by metalorganic vapor phase epitaxy using dimethylhydrazine as a nitrogen precursor. The PL spectra show improvements in the emission intensity and linewidth, and a decrease in a deep level emission, with the surface tilted from (100) to (411)A towards (111)A. For the peak position dependence on excitation intensity, a blueshift revealed by the increased excitation intensity is also depressed with higher-index substrates. These improvements could be obtained as a consequence of reductions in deep level defects, residual impurity incorporations, and spatial fluctuations in nitrogen concentration, with an increase in the A-type step density. In addition to the improved optical quality, (411)A shows a relatively large redshift in bandgap. Our results indicate that the use of high-index substrates is effective in GaNAs applications.
Control of Defects in CuInS2Thin Films by Incorporation of Na and O
Authors: Watanabe Takayuki , Yamamoto Tetsuya
Published: October 2002

We investigated the effects of the incorporation of both Na and O on defect structures forp-type Cu-poor CuInS2thin films on the basis of the analysis of experimental data using photoluminescence and the secondary ion mass spectrometry and theoretical results obtained byab-initioelectronic band structure calculations. We propose a model of the defect structure for CuInS2codoped with Na and O. The NaCuand OSform a complex in which they occupy nearest-neighbor sites. The above complex plays an important role in the annihilation of the deep level due to then-type divacancy which includes Cu vacancies (VCu) and vacancies of the sulfur close to theVCusite.
Detection of Supersonic Waves Emitted from Anomalous Arc Discharge in Plasma Processing Equipment
Authors: Yasaka Mitsuo , Takeshita Masayoshi , Miyagawa Ryuji
Published: October 2002

We report, for the first time, a new method of monitoring anomalous arc discharge in plasma processing equipment by detecting supersonic waves emitted at a discharge site. The supersonic wave is detected with an acoustic transducer attached to the outside surface of a plasma chamber. It is demonstrated that the method can detect anomalous discharge both in direct-current (DC) and radio-frequency (RF) plasma equipment. The results suggest that the method can find the location of anomalous discharge sites in the processing chamber.
Dependence of Electrical Characteristics of NbN/TiN/NbN Josephson Junctions on Barrier Thickness and Temperature
Authors: Hirotake Yamamori Hirotake Yamamori , Hitoshi Sasaki Hitoshi Sasaki , Akira Shoji Akira Shoji
Published: October 2002

The dependence of the product of critical current I
c and normal-state resistance R
n for NbN/TiN/NbN Josephson junctions on TiN barrier thickness and temperature has been measured. From a comparison of measured results and theoretically calculated I
c
R
n values, the coherence lengths in TiN films at 4.2 K and 10 K have been estimated to be 6.0 nm and 3.9 nm, respectively. At 4.2 K, the I
c
R
n product in the range of 20 to 400 µV is obtained for junctions with TiN film thickness ranging from 30 nm to 48 nm. At 10 K, the I
c
R
n product up to 50 µV can be obtained when the TiN film thickness is decreased to 25 nm.
Spectral Electroluminescence Mapping of a Blue InGaN Single Quantum Well Light-Emitting Diode
Authors: Fischer Peter , Christen Juergen , Nakamura Shuji
Published: October 2002

The microscopic spectral emission characteristic of Nichia's blue InGaN single
quantum well light-emitting diode is characterized by highly spatially and spectrally
resolved scanning electroluminescence microscopy under operation. The
electroluminescence intensity maps and the emission peak wavelength images directly
image the optical quality of the device and yield quantitative mappings of the good
p-contact quality as well as the small In fluctuations with a spatial resolution of
1 µm. Band filling effects, i.e. the consecutive filling of the local potential
minima is visualized. A highly spectrally resolved measurement proves the existence of
very sharp single emission lines from the localized states.
NiFe-Based Nanostructures Fabricated Using an Atomic Force Microscope
Authors: Takemura Yasushi , Shirakashi Jun-ichi
Published: October 2002

NiFe thin films of 20 nm thickness deposited by rf magnetron sputtering on SiO2/Si substrates were selectively oxidized using an atomic force microscope (AFM). The dot structures of NiFe-oxide were fabricated by applying a pulse voltage to the AFM cantilever. The height of the dots was controlled in the range from 3.5 to 14 nm by changing the voltage or duration of the applied pulse bias. The diameter of the dots was varied from 60 to 140 nm, which was not strongly dependent on the duration of the pulsed bias.
Stripe-Patterned Garnet Films on Substrates with Ion-Beam-Bombarded Micropatterns
Authors: Yasuyuki Okamura Yasuyuki Okamura , Sadahiko Yamamoto Sadahiko Yamamoto
Published: October 2002

We report the selected-area epitaxy (SAE) of rare-earth iron garnet crystalline and amorphous straight ridge patterns with 8 µm width deposited on Gd3Ga5O12 substrates. The samples were fabricated by a sputter epitaxial method on substrates that were partially etched by ion-beam bombardment. We found that the stripe pattern direction significantly affects the crystallographic formation of the side wall of the grown ridge.
Bismuth-Substituted Lanthanum Manganite for Bolometric Applications
Authors: Hayashi Ken-ichi , Ohta Eiji , Wada Hideo , Higuma Hiroko
Published: October 2002

In this study, we are exploring the use of perovskite manganese oxide for bolometric applications. To obtain a large temperature coefficient of resistance (TCR: defined as 1/R
d
R/d
T) at near-room temperature, we formed (Bi, La)1-x
Sr
x
MnO3 (BLSMO) bulk samples. The substituted Bi in samples function to reduce the crystallization temperature and to eliminate the ferromagnetic phase. In this report, we discuss the issues related to the influence of the substituted Bi on features such as the surface morphologies, crystallinities and electrical transport properties. For the samples, the temperature dependence of resistivity indicates thermally activated behavior like that of a semiconductor, and a higher activation energy implies a larger TCR value. The maximum TCR value of the samples was 3.6%/K at room temperature.
A New Linear Piezoelectric Motor with Self-Lock Feature
Authors: Ann Ngoi Kok , Lin Wu , Ng Lim Enk
Published: October 2002

The friction-type motor is the overwhelming type in the field of piezoelectric motors. The limitations of the friction-type motors are their inability to achieve high output push force or torque. Based on the theory of self-lock, a novel mechanism for the linear piezoelectric motor is proposed in this paper. The new motor transfers the output force and displacement generated by a piezoelectric actuator directly, whereas the friction-type motor transfers via the induced friction between the stator and the rotor. The new motor can be applied in cases where both high positioning precision and heavy load are essential. A long-distance positioning accuracy of 10 nm has been achieved.
Low-Temperature Process to Improve the Leakage Current of (Ba, Sr)TiO3 Films on Pt/TiN/Ti/Si Substrates
Authors: Hwang Chuan-Chou , Lai Ming-Jiunn , Jaing Cheng-Chung , Chen Jyh-Shin , Huang Stewart , Juang Miin-Horng , Cheng Huang-Chung
Published: October 2002

In this study, we employed an oxygen plasma post-treatment to improve the leakage characteristics of Pt/(Ba, Sr)TiO3(BST)/Pt capacitors prepared by the RF cosputtering technique. Applying oxygen plasma treatment to BST thin films can effectively passivate the oxygen vacancies of the BST films, thus decreasing the electric conduction paths of leakage current. The leakage current is reduced by as many as two orders of magnitude by this low-temperature (250°C) and short duration (∼5 min) process. However, the usage of oxygen plasma treatment is not unrestricted. Plasma treatment over a long time (more than 10 min) degrades the leakage characteristics, due to plasma damage. Therefore, a proper oxygen plasma treatment for as-deposited BST films is desired to improve leakage characteristics of BST thin films.
Precipitation of Nanoscale Icosahedral Quasicrystalline Phase in Amorphous Hf70Cu20Pd10 Alloy
Authors: Li Chunfei , Inoue Akihisa
Published: October 2002

An amorphous Hf70Cu20Pd10 ternary alloy was prepared and its crystallization process was studied. The crystallization proceeds through two exothermic reactions. Annealing of the specimen at a temperature lower than the onset point of the low-temperature exothermic reaction resulted in the precipitation of an icosahedral quasicrystalline phase. Further annealing at the same temperature caused the phase transformation to Hf2Cu crystalline phase, indicating the metastable character of the icosahedral quasicrystalline phase. In comparison with the crystallization process of other Hf-based amorphous alloys, the effect of Pd addition on the precipitation of the icosahedral quasicrystalline phase was discussed from the point of view of atomic radius.
Characteristics of Copper Diffusion into Low Dielectric Constant Plasma Polymerized Cyclohexane Thin Films
Authors: Cheonman Shim Cheonman Shim , Jayoung Choi Jayoung Choi , Donggeun Jung Donggeun Jung , Nae-Eung Lee Nae-Eung Lee , Cheol-Woong Yang Cheol-Woong Yang
Published: October 2002

Copper (Cu) diffusion into low dielectric constant plasma polymerized cyclohexane (PPCHex) thin films deposited by plasma enhanced chemical vapor deposition upon annealing was investigated. Cu diffusion was analyzed by current–voltage (I–V) measurement, Rutherford backscattering spectroscopy (RBS), and transmission electron microscopy (TEM). From I–V measurement and TEM analysis, it was revealed that PPCHex thin films were resistant to Cu diffusion up to 400°C, while there was a notable amount of Cu diffused into the PPCHex thin films after 450°C annealing. RBS was not sensitive enough to detect a small amount of Cu diffused into the PPCHex films. Improved Cu diffusion resistance of our PPCHex thin films compared to thin films of chemically synthesized polymers is thought to be due to high cross-linking among film-forming species of plasma polymers.
Photoemission Study on Protonic Conductor CaZrO3: Evidence of the Exchange Mechanism of Proton and Hole
Authors: Higuchi Tohru , Tsukamoto Takeyo , Tezuka Yasuhisa , Kobayashi Kiyoshi , Yamaguchi Shu , Shin Shik
Published: October 2002

The exchange mechanism of proton and hole in protonic conductor
CaZrO3 has been investigated by photoemission spectroscopy. The
Fermi level is higher by about 1.0 eV through proton doping,
indicating that protons exchange with holes. The defect chemical
calculation proves that the change of the number of the protons,
holes, and the oxygen vacancies by the proton doping accords with
the photoemission process.
Superior Decomposition of N2O into N2 and O2 in a Fast Discharge Flow of N2O/He or N2O/Ar Mixtures
Authors: Masaharu Tsuji Masaharu Tsuji , Takeshi Tanoue Takeshi Tanoue , Atsushi Tanaka Atsushi Tanaka , Kousuke Nakano Kousuke Nakano , Taro Hamagami Taro Hamagami , Yukio Nishimura Yukio Nishimura
Published: October 2002

The decomposition of N2O into N2, O2, and NO was studied in a fast discharge flow of N2O/He or N2O/Ar mixtures. The decomposition efficiency of N2O into N2 and O2 in N2O/Ar mixtures was higher than that in N2O/He mixtures, and 99% of N2O could be decomposed into N2 and O2 at a low N2O flow rate of 25 sccm. The decomposition mechanism in the discharge flow is discussed on the basis of mass spectroscopic and optical emission spectroscopic data.
Effect of Microscopic Nonconservative Process on Noncontact Atomic Force Microscopy
Authors: Naruo Sasaki Naruo Sasaki , Masaru Tsukada Masaru Tsukada
Published: October 2002

Effects of the tip-induced nonconservative processes of the tip or surface atom on the cantilever dynamics of noncontact atomic force microscopy (nc-AFM) are theoretically analyzed based on the time-averaging perturbation theory. The typical order of the magnitude of theQvalue due to such nonconservative processes is estimated to be on the order of 104, which is comparable to the intrinsic dissipation of the cantilever free oscillation. The additional frequency shift due to the hysteresis loop of the force curve is estimated to be on the order of 10 Hz. This part of the frequency shift sets in like a step function when the tip turning point approaches the surface within a certain threshold height. This feature explains the experimental observation of the discontinuous frequency shift at chemical reactive sites.
Ray Tracing in an Inhomogeneous Liquid Crystal Cell
Authors: Bau-Jy Liang Bau-Jy Liang , Jin-Jei Wu Jin-Jei Wu , Chao-Sung Lin Chao-Sung Lin , Chien-Hung Wang Chien-Hung Wang
Published: October 2002

We provide a method for tracing normally or obliquely incident light propagating
in inhomogeneous media. The incidence angle of light and the optical axes of
birefringence media can be arbitrary. As an example, we employ a method to analyze
light behavior in two-dimensional inhomogeneous liquid crystal cells. The theoretical
results are compared with the experiment results.
Preparation of Highly Porous Silica Aerogel Thin Film by Supercritical Drying
Authors: Kawakami Nobuyuki , Fukumoto Yoshito , Kinoshita Takashi , Suzuki Kohei , Inoue Ken-ichi
Published: October 2002

Thin film preparation of porous silica aerogel is investigated
as super-low dielectric constant material for ultra-large scale
integrated circuits. By using Tetramethylorthosilicate based
solution mixed with Dimethyl sulphoxide, which effectively
suppresses solvent evaporation, thin film is successfully formed on
a wafer without cracking. After an optimization of the aging process
in water vapor, the film is dried in supercritical fluids of carbon
dioxide, which is free from capillary force, and a high porosity
aerogel with dielectric constant as low as 1.1 is obtained. Porosity
and the dielectric constant of aerogels can be controlled over a
wide range by changing the time of aging.
Alignment Mechanism of Nematic Liquid Crystal on Rubbed Polymer Surface Studied by Subsequent Processes of Rubbing and Photoalignment
Authors: Chung Doo-Han , Takanishi Yoichi , Ishikawa Ken , Takezoe Hideo , Park Byoungchoo , Jung Youngyi , Hwang Ha-Keun , Lee Sooman , Han Ki-Jong , Jang Sei-Hum
Published: October 2002

A novel method for understanding the alignment mechanism was motivated by the
texture observation of a nematic liquid crystal (LC) contacted with a photoaligned layer
after rubbing. Reorientation of director occurs by subsequent photoalignment to
different direction from that forced by rubbing. Moreover, it was found by polarized
absorption spectra that the preferential average main chain axis over whole the
alignment layer does not change, indicating that the orientation change by
photoalignment occurs only at very top surfaces. This experiment without changing
surface morphology indicates that the alignment priority for the nematic LC is mainly
governed by the anisotropic short-range intermolecular interaction between alignment
films and LC molecules and the effect of microgrooves plays a minor role.
Efficient Hole Generation above 1019 cm-3 in Mg-Doped InGaN/GaN Superlattices at Room Temperature
Authors: Kumakura Kazuhide , Makimoto Toshiki , Kobayashi Naoki
Published: October 2002

We achieved spatially averaged hole concentrations above 1019 cm-3
at room temperature in Mg-doped In
x
Ga1-x
N/GaN (4 nm/4 nm) superlattices
grown by metalorganic vapor phase epitaxy. The hole concentrations for the
In
x
Ga1-x
N /GaN superlattices increased with the In mole fraction, and the
maximum hole concentration reached 2.8×1019 cm-3 for the
In0.22Ga0.78N/GaN superlattice. The hole concentrations for the
superlattices are larger than those for the InGaN bulk layers with the same average In
mole fraction. The weak temperature dependence of the resistivities for InGaN/GaN
superlattices with higher In mole fractions indicates highly efficient hole generation
in the superlattice.
Reflective Liquid Crystal Display Using a Non-Twist Half-Wave Cell
Authors: Lee Gi-Dong , Kim Gi-Hong , Moon Sung-Hoon , Noh Jeong-Dong , Kim Sung-Chul , Park Won Sang , Yoon Tae-Hoon , Kim Jae Chang , Hong Seung Ho , Lee Seung Hee
Published: October 2002

An optical configuration for a single-polarizer reflective liquid crystal
display using a non-twist cell is proposed. Optimized optical configurations
could be achieved by using a cell with a quarter-wave retardation or a
half-wave retardation. Especially, a half-wave cell provides very high
brightness in the bright state. The configuration can be applied to most of
liquid crystal display modes with a non-twist cell. By fabricating an
antiferroelectric liquid crystal (LC) cell and a vertically aligned cell, we demonstrated high
brightness as well as high contrast of reflective half-wave cells.
Solution Growth of Single-Phase β-FeSi 2 Bulk Crystals
Authors: Haruhiko Udono Haruhiko Udono , Isao Kikuma Isao Kikuma
Published: October 2002

We have succeeded in growing single-phase β-FeSi2 crystals by a temperature gradient solution growth method. FeSi2 solute and Ga solvent were placed in a quartz ampule, which was evacuated under a high vacuum (<2×10-6 Torr) and sealed with a quartz rod. The ampule was heated for 24–144 h in a gradient temperature profile. The grown crystals had multiple facet planes and the color was metallic silver white. X-ray diffraction showed that the grown crystals were single-phase β-FeSi2. The conduction of the β-FeSi2 grown crystals was p-type and the resistivity was between 0.05 and 0.2 Ω·cm.
Ferromagnetism in Semiconductor Dot Array
Authors: Hiroyuki Tamura Hiroyuki Tamura , Kenji Shiraishi Kenji Shiraishi , Hideaki Takayanagi Hideaki Takayanagi
Published: October 2002

Ferromagnetism in semiconductor-dot arrays is theoretically predicted. The two types of bipartite semiconductor-dot arrays which we propose exhibit flat band characteristics. According to the Lieb theorem, ferromagnetism is predicted, although our designed dot arrays do not contain any magnetic elements. We also investigate the typical dot-radius and inter-dot distance for the realization of the semiconductor-dot ferromagnetism, and several applications are discussed.
New Method of Particle Confinement Time Measurement in RF Traps
Authors: Mitsutoshi Aramaki Mitsutoshi Aramaki , Youichi Sakawa Youichi Sakawa , Tatsuo Shoji Tatsuo Shoji
Published: October 2002

We have developed a new method to measure confinement time,
τ, of trapped ions in a toroidal RF trap. An electron beam which
creates Ar ions in the RF trap is modulated sinusoidally with angular frequency
ω0. The total number, N, of the confined ions is modulated
with phase delay φ of the electron beam current
I
B. τ is derived from φ using the
relation, τ=(1/ω0)tan
φ. This new method of
τ measurement has the advantage of less disturbance of ion
confinement because the synchronous detection of φ at
ω0 can minimize the modulation amplitude of
I
B.
CW Laser Oscillation in Z-Cut Nd-Diffused Ti:MgO:LiNbO3 Waveguides
Authors: Fujimura Masatoshi , Shin Yang Kim , Nishihara Hiroshi
Published: October 2002

Rare-earth doped LiNbO3 waveguide lasers have been studied for
implementation of waveguide devices with new functions. CW laser oscillation in a
Nd-doped Z-cut Ti:LiNbO3 waveguide was first demonstrated in this paper. Key
issues for the implementation of the waveguide lasers included preparation of
high-quality Nd-doped crystals and suppression of photorefractive damage. Nd thermal
diffusion technique was used to prepare the Nd-doped crystals. MgO-doped LiNbO3
crystals were used to suppress the damage. A prototype waveguide laser of 14-mm long
was fabricated, and CW oscillation was achieved at a wavelength of 1085 nm by
optical pumping at 809 nm. The threshold power was 27 mW at room temperature and
7 mW at 120°C.
Thermal Stability of Artificial SrTiO3/SrO Superlattice Epitaxially Grown on SrTiO3 Single Crystal
Authors: Iwazaki Yoshiki , Suzuki Toshimasa , Sekiguchi Shoichi , Fujimoto Masayuki
Published: October 2002

A post-annealed artificial (SrTiO3)5/SrO superlattice grown on a (100)
SrTiO3 single crystal substrate was characterized by X-ray diffraction (XRD) and
transmission electron microscopy (TEM), to investigate the thermal stability of
inserted rock-salt layers of SrO, the so-called Ruddlesden-Popper (RP) layers, in the
epitaxial thin film. The intensities of XRD satellite peaks stemming from the
superstructure decreased with increasing annealing temperature and almost
disappeared at 1000°C. The high-resolution cross-sectional TEM image of the
superlattice after annealing at 1000°C showed that RP layers perpendicular to the
film surface appeared, which was predominant over in-plane RP layers. The predominant
formation of the vertical RP layers may be attributed to the strain release of RP layers
at the film surface.
Equivalent Network Representation for Thickness Vibration Modes in Piezoelectric Plates with an Exponentially Graded Parameter
Authors: Ken Yamada Ken Yamada , Jun-ichi Sakamura Jun-ichi Sakamura , Kiyoshi Nakamura Kiyoshi Nakamura
Published: October 2002

Equivalent network representation is derived for thickness vibration modes in piezoelectric plates having an exponentially graded parameter.
The network is composed of a transmission line of length corresponding to
the plate thickness and an electrical port with two capacitors which is linked to the line at both its ends via two ideal transformers.
The ratios of the two transformers are different from each other and frequency dependent.
The two capacitors are also frequency dependent and have the same value but opposite sign. The frequency characteristic of the input electric admittance of the resonator, which shows the unique feature of the functionally graded piezoelectric plate, is demonstrated by equivalent network analysis.