bluuebunny/crossref_metadata_2025 huggingface dataset:
Preparation of Epitaxial Ge Film on Si by Pulsed Laser Ablation Using Molten Droplets
Authors: Yamada Satoru , Oguri Shinya , Morimoto Akiharu , Shimizu Tatsuo , Minamikawa Toshiharu , Yonezawa Yasuto
Published: October 2002

Ge films were prepared by pulsed laser ablation (PLA) using molten droplets on
(100) Si substrates. The second harmonic of YAG laser (532 nm) was employed for
producing the Ge droplets. The Ge film prepared at room temperature was found to have
a large number of solidified droplets on the substrate indicating that the present PLA
process is mainly governed by droplet ejection from the target. The X-ray pole-figure
measurement for Ge film prepared at an elevated substrate temperature revealed that
the film has Ge crystals aligned in plane as well as out of plane in a cube-on-cube
manner. These results indicate an epitaxial growth of Ge film on Si by PLA using a large
number of molten droplets.
Second-Harmonic Generation from GaP/AlP Multilayers on GaP (111) Substrates Based on Quasi-Phase Matching for the Fundamental Standing Wave
Authors: Motoyuki Sato Motoyuki Sato , Hiroyuki Yaguchi Hiroyuki Yaguchi , Ichiro Shoji Ichiro Shoji , Kentaro Onabe Kentaro Onabe , Ryoichi Ito Ryoichi Ito , Yasuhiro Shiraki Yasuhiro Shiraki , Shigeru Nakagawa Shigeru Nakagawa , Norihide Yamada Norihide Yamada
Published: October 2002

We have demonstrated second-harmonic generation (SHG) from GaP/AlP multilayers on GaP(111)A substrates based on quasi-phase matching (QPM) for the fundamental standing wave. Theoretical calculation predicted that the SHG power increases with increasing number of GaP/AlP multilayers because of their small absorption coefficient in the spectral range of second-harmonic light, which is in contrast to the case of GaAs/AlAs QPM multilayers. In the transmission SHG measurement using a frequency-tunable Ti:Sapphire laser as a fundamental wave source, maximum SHG power was obtained at a fundamental wavelength of 990 nm from the five-pair GaP/AlP QPM multilayers. The wavelength conversion efficiency was measured to be 9.8×10-10%/W, which was smaller than the theoretical value of 6.5×10-8%/W.
Molecular Beam Epitaxial Growth of High-Quality InP/InGaAs/InP Heterostructure with Polycrystalline GaAs and GaP Decomposition Sources
Authors: Dong Song Jin , Min Kim Jong , Tak Lee Yong
Published: October 2002

A high-quality InP/InGaAs/InP double heterostructure was grown by molecular beam epitaxy (MBE) with polycrystalline GaAs and GaP decomposition sources for group V elements. By rapidly changing the cell temperature of GaAs and GaP decomposition sources during the growth switching period from InP to InGaAs and vice versa, a parasitic contamination-free InP/InGaAs/InP double heterostructure was obtained. The photoluminescence linewidths are 4.8 meV at 9 K for InGaAs on InP, and 1.76 meV at 9 K for InP on InGaAs. The X-ray rocking curve linewidth of InGaAs is as low as 20 arcsec without side lobes. These photoluminescence (PL) and X-ray measurement results are comparable to the best MBE data ever reported. Secondary ion mass spectroscopy depth profiles indicate that the contaminations due to the memory effect of group V elements are suppressed below 3 orders of magnitude and the parasitic gallium incorporation from polycrystalline GaAs decomposition sources is below 5 orders of magnitude, which are the best results obtained by MBE so far.
Room-Temperature Magnetoresistance in Fe-Site-Substituted Sr2FeMoO6
Authors: Yutaka Moritomo Yutaka Moritomo , Hiroyuki Kusuya Hiroyuki Kusuya , Takumi Akimoto Takumi Akimoto , Akihiko Machida Akihiko Machida
Published: October 2002

We have observed room temperature magnetoresistance (MR) in Fe-site-substituted Sr2FeMoO6 crystal with a double perovskite structure.
These melt-grown crystals have few grain boundaries and show high conductivity (∼10-3 Ω·cm at 300 K), which is advantageous for a practical application.
We will discuss the possible origin on the basis of the substituent concentration dependence and temperature dependence of the magnitude of the MR.
Deposition of AlN Thin Films with Cubic Crystal Structures on Silicon Substrates at Room Temperature
Authors: Ren Zhong-Min , Lu Yong-Feng , Goh Yeow-Whatt , Chong Tow-Chong , Ng Mei-Ling , Wang Jian-Ping , Cheong Boon-Aik , Liew Yun-Fook
Published: October 2002

Cubic AlN thin films were deposited at room temperature by nitrogen-ion-assisted
pulsed laser ablation of a hexagonal AlN target. The full-width at half maximum
(FWHM) of the X-ray diffraction peak in the θ∼2θ scan can reach a value of 0.27 degrees.
In the Raman spectroscopy measurement, a new peak at 2333 cm-1
originating from cubic AlN polycrystalline was observed. Nitrogen ions not only
effectively promote the formation of stable Al–N bonds but also improve the crystal
properties of the deposited thin films. A nitrogen ion energy of 400 eV is proposed for
the thin-film deposition.
Vanishing of Resistance and Diamagnetism Observed in a Very Thin Al Film at Room Temperature
Authors: Hino Taro
Published: October 2002

A very thin Al film (thickness: 160–430 Å) was evaporated on
a silicon wafer substrate with a SiO2 film and an arachidic
acid Langmuir-Blodgett film. Vanishing of resistance and a
repulsive force indicating diamagnetism were observed in the
very thin Al film in a magnetic field at room temperature.
This repulsive force was measured by an apparatus which can
measure small displacements such as 10-2 µm with a laser beam.
First Fabrication of GaInAs/InP Buried Metal Heterojunction Bipolar Transistor and Reduction of Base-Collector Capacitance
Authors: Toshiki Arai Toshiki Arai , Yoshimichi Harada Yoshimichi Harada , Shigeharu Yamagami Shigeharu Yamagami , Yasuyuki Miyamoto Yasuyuki Miyamoto , Kazuhito Furuya Kazuhito Furuya
Published: October 2002

We report a novel approach for improving the performance of InP-based heterojunction bipolar transistors (HBTs). A buried-metal heterojunction bipolar transistor (BM-HBT), in which tungsten stripes of the same area as the emitter metal were buried in an i-InP collector layer, was fabricated for the first time. The aim in fabricating this structure is to realize a reduction in the total base-collector capacitance (C
BCT). In the measurement of microwave S-parameters, C
BCT of 10.3 fF was evaluated. The effective base-collector junction area of the BM-HBT was estimated to be
22% that of conventional-HBT considering the difference in collector thickness.
Thermal Stability and Interfacial Reaction of Barrier Layers with Low-Dielectric-Constant Fluorinated Carbon Interlayer
Authors: Hara Tohru , Sakamoto Keiichi , Togoh Fumiaki , Yang Hongning , Evans David R.
Published: October 2002

The thermal stability of low-dielectric-constant (ε) interlayers for
advanced ULSI's is studied. Thickness decreases by 7 and 4% with annealing from 390
to 450°C in poly-arylether and hydro-organo-siloxane polymer layers.
The thickness variation is as low as 2% in the carbon-rich fluorinated carbon (FC)
(F/C=0.90) layer at temperatures between 250 and 450°C.
The composition of F/C decreases markedly with the increase of temperature above
450°C in high F/C composition, such as 1.20 and 1.28, FC layers. However, this
composition is invariable with annealing at 450°C in layers with low F/C
composition (F/C=0.90) because F does not leave the F-C bond in this layer.
The barrier effect for a FC low ε interlayer is studied in titanium nitride
(TiN) and tantalum nitride (TaN) barrier layers. When polycrystalline TiN and TaN
barrier layers are used, significant interfacial reaction occurs at low temperatures.
That is, Ti and Ta of TiN and TaN layers diffuse deeply into the FC layer at 350°C.
Penetration of F from the FC layer into these barrier layers occurs respectively at
450°C. However, diffusion of Ta and F into FC and TaN can be suppressed if a
microcrystalline TaN (TaN0.90) barrier layer is used; such a N-rich microcrystalline
TaN layer can be deposited by reactive sputtering.
Photonic Gaps in Reduced-Order Colloidal Particulate Assemblies
Authors: Sun Hong-Bo , Xu Ying , Ye Jia-Yu , Matsuo Shigeki , Misawa Hiroaki , Song Junfeng , Du Guotong , Liu Shiyong
Published: October 2002

Colloidal assemblies consisting of monotonic polystyrene microspheres with a controlled degree of ordering were fabricated, and exhibited rich spectral behaviors. Smooth and spike-modulated broad attenuation regions in transmission spectra were observed in highly disordered and partly disordered samples, respectively, in contrast to the narrow peaks observed in well-ordered photonic crystals. These properties are interpreted consistently by analyzing the variation of the volume of closely packed units.
Photoinduced Surface Relief Grating on Composite Film of Conducting Polymer and Polyacrylate Containing Azo-Substituent
Authors: Masanori Ozaki Masanori Ozaki , Taisuke Nagata Taisuke Nagata , Tatsunosuke Matsui Tatsunosuke Matsui , Katsumi Yoshino Katsumi Yoshino , Francois Kajzar Francois Kajzar
Published: October 2002

The formation of a photoinduced surface relief grating on a composite film of conducting polymer with a rigid main chain structure and an acrylate polymer containing azo-substituent with a soft main chain structure has been studied. The diffraction efficiency of the photoinduced surface relief grating decreases with increasing concentration of conducting polymer with respect to the polyacrylate in the concentration range higher than 3 mol%. It has been found, however, that the formation of the surface relief grating is promoted by a slight doping of the conducting polymer (<3 mol%) and progresses even after terminating the laser light irradiation on the composite film. An anomalous angular dependence of photoluminescence from the composite film with a surface relief grating on it has also been observed.
Laser Cooling of Ca+ with an External-Cavity Ultraviolet Diode Laser
Authors: Kazuhiro Hayasaka Kazuhiro Hayasaka , Shinji Urabe Shinji Urabe , Masayoshi Watanabe Masayoshi Watanabe
Published: October 2002

We have built an external-cavity ultraviolet diode laser at 397 nm
for Ca+ spectroscopy.
The laser consists of a commercial ultraviolet diode laser and a holographic grating in the Littrow configuration. Stable single-mode operation with a power of 3 mW, a linewidth no larger than 2 MHz, and a mode-hop-free frequency scanning range of 15 GHz was achieved. This laser was used to cool a small number of Ca+ in a rf trap. The ions were cooled to a low temperature to form a crystallized state. The use of the laser will simplify experimental setups for diverse applications of Ca+, such as frequency standards, quantum computers and one-atom lasers.
Dielectric Study on the Johari-Goldstein Mode of Glass-Forming Sorbitol
Authors: Takuya Fujima Takuya Fujima , Hiroshi Frusawa Hiroshi Frusawa , Kohzo Ito Kohzo Ito , Reinosuke Hayakawa Reinosuke Hayakawa
Published: October 2002

We investigate precisely the temperature dependence of dielectric relaxations for glass-forming sorbitol, focusing on the Johari-Goldstein (J-G) mode. The results reveal that the relaxation times of the J-G mode exhibit a new dependence at high temperatures, different from the behavior reported at low temperatures so far. As a consequence, it is found that the J-G mode merges smoothly with the α-relaxation mode in the crossover region between the normal liquid and the supercooled one; the branching temperature obtained is much higher than that previously extrapolated from the lower temperature dependence of relaxation times.
Structural Phase Transition and Metallic Behavior in Misfit Layered (Bi,Pb)-Sr-Co-O System
Authors: Tsuyoshi Yamamoto Tsuyoshi Yamamoto , Ichiro Tsukada Ichiro Tsukada , Kunimitsu Uchinokura Kunimitsu Uchinokura , Mikio Takagi Mikio Takagi , Takashi Tsubone Takashi Tsubone , Masaki Ichihara Masaki Ichihara , Kimiko Kobayashi Kimiko Kobayashi
Published: October 2002

The crystal structure of Bi2-x
PbxSr2Co2Oy has been investigated by X-ray diffraction and electron diffraction analyses. In contrast to what has previously been considered a Bi2Sr2CaCu2O8-type structure, we found that this material has a misfit layer structure: two subcells with different periodicities are alternately stacked.
We have studied the x dependence of the crystal structure and found a discontinuous phase transition at x ≃0.2, where only Bi-Sr-O layers show a drastic change in lattice constants. Pb doping induces metallic behavior, but the effect of the structural phase transition is less clearly observed, which indicates that the electronic properties are mainly
dominated by CoO2 layers.
Stable Icosahedral Quasicrystals in the Cd–Mg–RE (RE = Rare Earth Element) Systems
Authors: Guo Junqing , Abe Eiji , Tsai An-Pang
Published: October 2002

A stable icosahedral phase has been found in a series of Cd65Mg20RE15 (RE=Y, Nd, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu) alloys. These icosahedral alloys have quasilattice parameters from 0.5571 to 0.5799 nm. Electron diffraction study confirmed that the icosahedral quasicrystals have a primitive icosahedral structure.
Fabrication of GaAs Quantum Dots by Modified Droplet Epitaxy
Authors: Watanabe Katsuyuki , Koguchi Nobuyuki , Gotoh Yoshihiko
Published: October 2002

We propose a modified droplet epitaxy method for fabricating
self-organized GaAs/AlGaAs quantum dots (QDs) with a high As flux
irradiation and a low substrate temperature. By our novel method,
GaAs QDs were successfully formed, retaining their pyramidal shape,
original base size and density of droplets, and preventing
layer-by-layer growth. Quantum size effects of the QDs were
distinctly observed by photoluminescence measurements. It was
confirmed that this new modified droplet epitaxy method is promising
for fabricating a high-quality GaAs/AlGaAs QD system.
Room Temperature Single-Electron Narrow-Channel Memory with Silicon Nanodots Embedded in SiO2 Matrix
Authors: Yun Feng , Hinds Bruce J. , Hatatani Shigeo , Oda Shunri
Published: October 2002

The room-temperature operation of a single-electron narrow-channel memory device has been demonstrated by the combined fabrication of a narrow-channel (20 nm wide by 80 nm long) field-effect transistor (FET) defined by electron-beam lithography and nanocrystalline Si (nc-Si) dots formed by annealing a thin film of SiO
x
(x<2). Electrons are injected into nc-Si floating gate dots in discrete units, as observed by the stepwise increase in the threshold shift with writing bias, which is expected for Coulomb repulsion within the nc-Si dot. Time-dependent measurement of the channel current under the floating gate shows stepwise loss of charge, with a lifetime of each stored electron of about 500 s at room temperature. Measurements at low temperature (20 K) show similar discrete steps in memory writing.
Enhancement of Barrier Properties in Chemical Vapor Deposited TiN Employing Multi-Stacked Ti/TiN Structure
Authors: Chang Ting-Chang , Liu Po-Tsun , Yang Ya-Liang , Hu Jung-Chih , Simon M. Sze Simon M. Sze
Published: October 2002

A novel multi-stacked Ti/TiN structure was proposed to enhance the
barrier properties of chemical vapor deposited TiN film. Both the chlorine
content and the resistivity of the multi-stacked Ti/TiN films are
significantly decreased when compared with a single layer of chemical
vapor deposited (CVD) TiN film
with the same thickness. Secondary ion mass spectrometry (SIMS) data
showed that Ti atom distribution is fairly uniform to fill the grain boundary
of TiN film. Therefore, the leakage current resulted from junction spiking was
further reduced by the grain boundary effects when employing multi-stacked
Ti/TiN as diffusion barrier layer instead of a single layer of TiN film.
Anti-Surfactant in III-Nitride Epitaxy –Quantum Dot Formation and Dislocation Termination–
Authors: Tanaka Satoru , Takeuchi Misaichi , Aoyagi Yoshinobu
Published: October 2002

A new approach toward epitaxial growth of group III nitrides using an “anti-surfactant” is presented. Two unique phenomena, quantum dot formation and dislocation termination, were recognized using this approach. The presence of Si atoms as an anti-surfactant on (Al)GaN surfaces modified the nitride epitaxial growth kinetics. These phenomena appeared to be independent; however, the growth mechanisms indicated a common surface event, which included the formation of a monolayer thick Si–N mask (nano-mask) within the fractional coverage on the surface. The Si–N nano-mask influenced the morphology of the deposited GaN surface, i.e. quantum structures, and also contributed to the termination of threading dislocations in GaN films.
Obliquely Tilted Discotic Phase Compensation Films
Authors: Wu Long-Hai , Luo Shr-Jie , Hsu Chain-Shu , Wu Shin-Tson
Published: October 2002

A three-step method was developed to fabricate the obliquely tilted discotic negative birefringence phase compensation films. Model fitting reveals that the tilt angle of the discotic directors is about 46° from surface normal. The total phase retardation value of the film can be controlled by the discotic layer thickness. These asymmetric phase retardation films are useful for widening the viewing angle of a liquid crystal display device.
Direct Generation of 27-mJ, 309-nm Pulses from a Ce3+:LiLuF4 Oscillator Using a Large-Size Ce3+:LiLuF4 Crystal
Authors: Liu Zhenlin , Shimamura Kiyoshi , Nakano Kenji , Mujilatu Na , Fukuda Tsuguo , Kozeki Toshimasa , Ohtake Hideyuki , Sarukura Nobuhiko
Published: October 2002

An ultraviolet solid-state Ce3+:LiLuF4 (Ce:LLF) laser
which was pumped transversely by a KrF excimer laser with the
repetition rate of 1 Hz produced a 27-mJ, 309-nm pulse using a
large-size Ce:LLF crystal which was grown by the Czochralski (CZ)
method, and the slope efficiency was approximately 17%.
Preparation and Characterization of Fe-Based III-V Diluted Magnetic Semiconductor (Ga, Fe)As
Authors: Haneda Shigeru , Yamaura Masaaki , Takatani Yukihiro , Hara Kazuhiko , Harigae Shin-ichi , Munekata Hiroo
Published: October 2002

The Fe-based III-V diluted magnetic semiconductor (III-V-DMS), (Ga, Fe)As, has been
grown successfully on GaAs(001) substrates by molecular beam epitaxy at a substrate
temperature T
s ranging from 260–350°C. Secondary ion mass spectroscopy analysis has
exhibited that the film composition can be expressed by Ga1-x
Fe
x
As. X-ray diffraction data
have indicated that the lattice constant of Ga1-x
Fe
x
As decreases with increasing Fe composition.
Magnetization data have exhibited that epilayers are predominantly paramagnetic, however,
their detailed behavior differs from that of Mn-based DMS systems. The work has
demonstrated that the physical properties of III-V-DMS can be changed significantly by the
choice of transition metals.
Field-Emission Properties of Aligned Carbon Nanotubes
Authors: Hong Wei-Kai , Shih Han-Chang , Tsai Shang-Hua , Shu Chen-Tien , Tarntair Fu-Gow , Cheng Huang-Chung
Published: October 2002

Dense, well-separated, and aligned carbon nanotubes have been prepared via bias-enhanced microwave plasma chemical vapor deposition. The turn-on fields defined at the emission current density of 10 µA/cm2 are about 3.35 V/µm, 2.54 V/µm, and 3.54 V/µm, for the immersion times in PdCl2 of 1 min, 20 min, and 40 min, respectively. The corresponding emission current densities are about 0.97 mA/cm2, 4.5 mA/cm2, and 0.44 mA/cm2 at the electric field of 5 V/µm. The higher emission current obtained from the aligned carbon nanotubes for the immersion time of 20 min is ascribed to the denser and sharper nanotubes formed in this condition.
An Efficient Decomposition of NO into N2 and O2 in a Fast Discharge Flow of NO/He Mixtures
Authors: Masaharu Tsuji Masaharu Tsuji , Atsushi Tanaka Atsushi Tanaka , Taro Hamagami Taro Hamagami , Kousuke Nakano Kousuke Nakano , Yukio Nishimura Yukio Nishimura
Published: October 2002

About 97% of NO was selectively decomposed into N2 and O2 in a fast discharge flow of a NO/He mixture at a microwave power of 150–200 W, and NO and He flow rates of 25 and 2000 sccm, respectively. The decomposition mechanism in the discharge flow is discussed on the basis of mass spectroscopic and optical emission spectroscopic data.
Intrinsic Fiber-Optic Immunosensors Based on Monochromatic Light Excitation of Surface Plasmon Resonance
Authors: Lin Wen Bin , Chovelon Jean Marc , Lacroix Monique , Jaffrezic-Renault Nicole
Published: October 2002

Currently, the intrinsic fiber-optic immunosensors in common use are usually based on polychromatic light excitation of the surface plasmon resonance, such as the BIACORE Probe developed by Biacore company (Sweden). We propose in this paper a novel fiber-optic immunosensor, simpler and cheaper, which is illuminated by a monochromatic light at 658 nm wavelength emitted from a commercially available laser diode. The application of detecting the rabbit IgG affinity reaction proves its feasibility. This work provides a starting step towards the development of a portable immunoprobe for non-labeling immunoassay.
Temperature and Annealing Effects on Photoluminescence Spectra of (InAs)1/(GaP)2 Superlattices Grown by Solid-Source Molecular Beam Epitaxy
Authors: Cheng Yi-Cheng , Chi Sien , Chou Shu-Tsun , Huang Kai-Feng
Published: October 2002

Anomalous variation of photoluminescence (PL) wavelengths with temperature was observed in (InAs)1/(GaP)2 short-period-superlattice (SPS) quantum wells grown by solid-source molecular beam epitaxy with different phosphorus and arsenic cracker temperatures. We believed that the anomalous PL behavior could be attributed to the multi-axial strain effect existed at the abrupt InAs and GaP interfaces in the SPS structure. After rapid thermal anneal (RTA) treatment, the anomalous PL spectra in the low temperature region disappeared but the high temperature PL characteristics remained, which revealed the thermal stability of the (InAs)1/(GaP)2 quantum well structures and its potential in replacing InGaAsP quaternary.
Synchronized Chaos of Three Elements in Centered Triangular Laser Arrays
Authors: Oishi Yuji , Nemoto Koshichi
Published: October 2002

Symmetrical two-dimensional coupled laser arrays in which lasers are placed on the apices and center of an equilateral polygon are proposed for obtaining a number of synchronized chaotic signals. Numerical simulations for centered triangular arrays are conducted and the synchronized chaos of three lasers on the apices (satellite lasers) is observed. The central-satellite coupling is more important than the satellite-satellite coupling for the synchronized chaos of all satellite lasers.
Preparation of Metal Colloids by a Laser Ablation Technique in Solution: Influence of Laser Wavelength on the Efficiencies of Colloid Formation
Authors: Takeshi Tsuji Takeshi Tsuji , Kenzo Iryo Kenzo Iryo , Hidefumi Ohta Hidefumi Ohta , Yukio Nishimura Yukio Nishimura
Published: October 2002

Colloid formation with laser ablation in solution was examined to investigate the influence of wavelength and focus conditions of irradiation. The wavelength dependence of the ablation efficiency was different between the focused and nonfocused conditions. Reabsorption of incident beam by colloid particles was suggested to be effective under the focused condition.
Paramagnetic Defects Related to Positive Charges in Silicon Oxynitride Films
Authors: Miura Yoshinao , Fujieda Shinji , Hasegawa Eiji
Published: October 2002

Electron spin resonance (ESR) spectroscopy is used to explore the origin of positive charges in silicon oxynitride thin films formed in a N2O ambient. A new type of paramagnetic center in as-grown oxynitrides appears as a single peak in the ESR spectrum with a zero crossing g value of 2.0006. This value suggests that the paramagnetic center is a kind of E′ center. We investigate the quantitative behavior of the positive charge center and the paramagnetic center through their density changes induced by vacuum ultraviolet irradiation and hydrogen annealing. Based on the similar behavior of both centers, we propose that the paramagnetic centers can account for a significant part of the positive charges specific to oxynitrides.
Improvement of Property of Pb(ZrxTi1-x)O3 Thin Film Prepared by Source Gas Pulse-Introduced Metalorganic Chemical Vapor Deposition
Authors: Nagashima Kuniharu , Aratani Masanori , Funakubo Hiroshi
Published: October 2002

Pb(Zr, Ti)O3 (PZT) thin films with Zr/(Zr+Ti) of 0.42 were prepared on (111)Pt/Ti/SiO2/Si substrates at 620°C by metalorganic chemical vapor deposition (MOCVD). We attempted the pulse introduction of a mixture of source gases into the reaction chamber and succeeded in simultaneous improvements of the crystallinity, surface roughness and electrical properties of the PZT film by this preparation method. The (111)-orientation increased and the surface roughness decreased. Moreover, the leakage decreased and well-saturated symmetrical polarization-electric field (P-E) hysteresis loop were obtained. Remanent polarization (P
r) and the coercive field (E
c) values of this pulse-MOCVD film were 44 µC/cm2 and 85 kV/cm, respectively.
Synthesis of Nanosize Powders of Aluminum Nitride by Pulsed Wire Discharge
Authors: Sangurai Channarong , Kinemuchi Yoshiaki , Suzuki Tsuneo , Jiang Weihua , Yatsui Kiyoshi
Published: October 2002

Using a thin aluminum wire, we have successfully synthesized aluminum nitride powders in N2/NH3 mixed gas. The powders were characterized by X-ray diffraction and specific surface area measurement. The results of X-ray diffraction indicated that the synthesized powders consist of wurtzite aluminum nitride. In the powders synthesized in N2 gas, a weak peak intensity of aluminum nitride was observed. However, it is significantly increased using a mixed gas of N2/NH3. The average particle sizes were 30–70 nm.
Surface Modification of High-Speed Tool Steel by Repeated Irradiations of Intense Pulsed Ion Beam
Authors: Hiroshi Akamatsu Hiroshi Akamatsu , Yoshisuke Tanihara Yoshisuke Tanihara , Tsutomu Ikeda Tsutomu Ikeda , Kingo Azuma Kingo Azuma , Etsuo Fujiwara Etsuo Fujiwara , Mitsuyasu Yatsuzuka Mitsuyasu Yatsuzuka
Published: October 2002

Surface modification of a high-speed tool steel (SKH51) has been performed by irradiation of the proton intense pulsed ion beam (IPIB) with the ion energy of 180 keV, the ion current density of 460 A/cm2, and pulse duration of 65 ns. By 1-pulse irradiation of the IPIB, the second phase carbides such as VC, Fe6C, and Cr6C are dispersed from the irradiated surface, and the average grain size decreases to 240 nm corresponding to approximately 1/30 of the untreated one. Repeated irradiations of the IPIB result in the reduction in grain size and conversion of an α-Fe structure to a γ-Fe one. The SKH51 treated by 10-pulses irradiation has a single phase of γ-Fe, and the grain size is reduced to approximately 1/170 of that of the untreated one. In addition, the 10-pulses-irradiated surface has an improved wear resistance.
X-Ray Emission Induced by 60 keV High-Flux Copper Negative-Ion Implantation
Authors: Amekura Hiroshi , Voitsenya Vladimir , Lay Thi Thi , Takeda Yoshihiko , Kishimoto Naoki
Published: October 2002

X-ray emission induced by high-flux 60 keV Cu negative ion implantation into silica glasses (a-SiO2) has been studied in the energy range of 0.6–20 keV. At low ion fluxes, the emission spectrum consists of a strong Cu(L) line at 0.95 keV only, without Cu(K) and Si(K) lines. The result is explained by the electron promotion through the quasi-molecule formation. With increasing ion flux, new peaks appear at 1.8, 2.5 and 3.2 keV. These peaks are ascribed to the sum-peak effect under high-flux implantation. Judging from the cross sections and the time dependence, the observed Cu(L) X-ray is concluded to be generated via Cu–O collisions.
Optical Investigation of Fast Pulsed Discharge on Surface of Ceramics for Environmental Applications
Authors: Shinji Ibuka Shinji Ibuka , Yuan-shing Liu Yuan-shing Liu , Masami Okada Masami Okada , Takehiko Nakamura Takehiko Nakamura , Azhar Kamal Azhar Kamal , Toru Murakami Toru Murakami , Hideki Sehata Hideki Sehata , Koichi Yasuoka Koichi Yasuoka , Shozo Ishii Shozo Ishii
Published: October 2002

Pulsed surface discharge on the surface of ceramics was investigated experimentally. The photon counting method was applied to clarify the preceding phase of the discharge. The results indicated the effect of charge injection from electrodes. A pulsed surface discharge reactor for decomposition of nitrogen oxides utilizing honeycomb ceramics was proposed. Discharge processes were observed by framing and streak photographs taken by image converter cameras. The emission spectra from the discharge were investigated using a spectrometer. Uniform surface discharges on honeycomb ceramics were successfully obtained utilizing a fast pulsed power generator with a SI-thyristor.
Leaked Electrons from Virtual Cathode Oscillation
Authors: Seo Yoonho , Choi Eun Ha , Byun Chil Goo , Choi Myung Choul
Published: October 2002

We investigate the properties of leaked electrons from virtual cathode oscillation. It is found from a simulation that most leakage occurs from the radial edge of the beam, so that the leaked beam forms an annular beam. Axial bunching was also observed. The average leaked current was close to the space-charge limiting current, and the energies of the electrons at the end of the drift tube were a fraction of the injected energies, and were nearly independent of the injection currents. A preliminary experimental result seems to support these simulation results.
Visualization of Double-Pulse Discharge in Excimer Laser with Gas Flow
Authors: Jodai Yoshifumi , Imada Go , Masuda Wataru , Yatsui Kiyoshi
Published: October 2002

The double-pulse discharge has been demonstrated in a gas flow with a velocity of 200 m/s which is generated by a Ludwieg tube. A gas mixture of helium and argon is used to simulate the excitation discharge of excimer lasers. The shock waves and the gas density perturbation between two successive discharges have also been visualized applying the shadowgraph technique using a high-speed image-converter camera. The second discharge at an equivalent pulse repetition frequency (f) of 10 kHz becomes an arc through the heated column which is generated by the first discharge. At f=5 kHz, the glow discharge can be produced between the electrodes, however, an arc is also observed through the heated column which is located somewhat downstream of the electrodes. Only a glow discharge is possible up to f=3 kHz. These results clearly demonstrate that the heated column has a decisive effect on the stability of repetitive pulse discharges.
High-Repetition-Rate Electron-Beam-Pumped KrF Laser Technology for Inertial-Fusion-Energy Drivers
Authors: Okuda Isao , Takahashi Eiichi , Matsushima Isao , Matsumoto Yuji , Kato Susumu , Owadano Yoshiro
Published: October 2002

The development of a high-repetition-rate (rep-rate) electron-beam (e-beam)-pumped KrF laser is described. In this study, we aim to achieve pulsed laser outputs of 20 J/80 ns at a rep rate of 1 Hz. The key issues are heat management in the diode foils and introduction of long-lifetime switches into the pulsed-power system. E-beam generation experiments have been started with initial test results of twenty consecutive shots at 1 Hz. Improvement in the energy-transfer efficiency in the rep-rate pulsed-power systems is also discussed.
A Highly-Efficient Tungsten-Polycide Gate Radio-Frequency Power Metal-Oxide-Semiconductor Field-Effect-Transistor Using Bonded Silicon-on-Insulator Technology
Authors: Matsumoto Satoshi , Hiraoka Yasushi , Sakai Tatsuo
Published: October 2002

Highly-efficient RF thin-film silicon-on-insulator (SOI) power metal-oxide-semiconductor field-effect-transistors (MOSFETs) were fabricated by a 0.4-µm complementary metal-oxide-semiconductor field-effect-transistors (CMOSFET)/SOI process. Their breakdown voltages were more than 10 V when the gate and drain offset lengths were 0.4 µm, and the cutoff frequency and maximum oscillation frequency were 20.4 and 20.7 GHz, respectively. When the drain supply voltage was 3.0 V, its power-added efficiency and saturation output power were 66% and 24 dBm at 2 GHz and were 20.3 dBm and 52% at 5.8 GHz. These values were higher than the corresponding values for a thin-film SOI power MOSFET fabricated using state-of-the-art 0.5-µm CMOS/SOI technology. These results indicate that the 0.4-µm-rule thin-film SOI technology is applicable at not only 2-GHz-band but also 5 GHz-band.
Study of Bump Formation in Integrated Chemical Vapor Deposition–Physical Vapor Deposition Aluminum Filling Process
Authors: Lee Joo Wan , Kim Byoung Youp , Han Sang Yeop , Lee Won-Jun , Kim Jun Ki , Park Jin-Won , Roh Jae Sung , Kim Yeong-Cheol
Published: October 2002

Aluminum (Al) bumps are observed over contact holes when the chemical vapor deposition-physical vapor deposition (CVD-PVD) Al filling process is employed in sub micron technology. Boundaries of bumpy Al grains are formed inside the contact holes, while those of smooth Al grains are formed at the neck of the contact holes. Transmission electron microscopy (TEM) is employed to observe the crystallographic orientation of bumpy and smooth Al grains, and the results are <220> and <111> on {100} silicon surface, respectively. It is known that the growth rate of Al in the <220> direction is higher than that in the <111> direction because of its lower plane density. The difference in growth rate between the <220> direction and the <111> direction is believed to lead to bump formation. A modified PVD Al process to form grain boundaries at the neck of the holes is developed to prevent bumpy Al formation and fill the holes completely.
Structural and Magnetic Properties of Spinel Ferrite Epitaxial Films Pulsed-Laser-Deposited at Low Temperature
Authors: Takakazu Kiyomura Takakazu Kiyomura , Manabu Gomi Manabu Gomi
Published: October 2002

Thin films of NiZn- and MnZn-ferrites have been epitaxially grown on sapphire substrates at low temperatures by pulsed laser deposition (PLD). The structural and magnetic properties of the deposited films were investigated in detail. All films crystallized in the spinel phase even when deposited at room temperature and low oxygen pressures of 1 ×10-4 Torr to 1 ×10-6 Torr. X-ray diffraction analysis and atomic force microscopy showed that the spinel ferrite thin films grown at low temperatures below 200°C have high structural and morphological qualities, comparable to those of films grown at higher temperatures. The saturation magnetization of the room-temperature grown films was much lower than that of the bulk for NiZn-ferrite, while, for MnZn-ferrite, was 80% (270 emu/cm3) of that of the bulk. These results make PLD a prime candidate technique for low-temperature epitaxial growth of ferrite thin films.
AlGaAs/InGaAs Pseudomorphic High Electron Mobility Transistor using Pd/Ge Ohmic Contact
Authors: Lee Jong-Lam , Kim Yi-Tae , Oh Jung-Woo , Lee Byung-Teak
Published: October 2002

Microstructural reactions of a Pd/Ge contact to a AlGaAs/InGaAs pseudomorphic high electron mobility transistor (PHEMT) have been investigated, and the results have been used to interpret the changes of electrical properties of the PHEMT. In the as-deposited state, a ternary phase of Pd
x
GaAs containing excess Ge atoms is formed at the interface of Pd/GaAs. When the ohmic metals deposited were annealed at 300°C, a PdGe compound was formed and its contact resistivity was decreased to 1.2×10-7 Ω·cm2. This is due to the preferential outdiffusion of Ga atoms to the PdGe during annealing, leaving Ga vacancies behind. Simultaneously, Ge atoms are indiffused to the GaAs and occupy the Ga vacancies, converting the interfacial GaAs layer into n+-GaAs. The low-temperature PdGe ohmic contact allows changing the sequence in the formation of source/drain and gate electrodes in the PHEMT process. The device performance was remarkably improved as the annealing temperature was increased or the contact resistivity was reduced. The PHEMTs with a gate length of 1.1 µm, annealed at 300°C, exhibit maximum transconductance of 381 mS/mm.
Current–Voltage Characteristics of AlN/GaN Heterostructure Metal Insulator Semiconductor Diode
Authors: Imanaga Syunji , Nakamura Fumihiko , Kawai Hiroji
Published: October 2002

We fabricated heterostructure metal insulator semiconductor (Hetero-MIS) diodes with a Schottky metal-(Ni/Au)/AlN(6 nm)/n+-GaN(Si:3×1018 cm-3)/ohmic metal-(Ti/Al/Pt/Au) structure, and measured the dependence of current–voltage (I–V) characteristics of the diodes on the growth temperature of the AlN layer using low-pressure metalorganic chemical vapor deposition (MOCVD). We found that the current decreases as the growth temperature of the AlN layer decreases from 990°C to 650°C. We conclude that the current flows mainly between the columnar crystals of the AlN layer, because we found from the temperature dependence of the surface morphology of the AlN layer that the radius of the columnar crystals decreases and the height of the columns decreases as the growth temperature decreases, and because the measured I–V characteristics are in agreement with the simulated ones if we assume that the thickness of the AlN layer is about 2 nm, which is much less than the measured thickness of the columnar crystal of 6 nm.
New Trap-Assisted Band-to-Band Tunneling Induced Gate Current Model for P-Channel Metal-Oxide-Semiconductor Field Effect Transistors with Sub-3 nm Oxides
Authors: Lee Hai-Ming , Liu Cheng-Jye , Hsu Chih-Wei , Liang Mong-Song , King Ya-Chin , Hsu Charles Ching-Hsiang
Published: October 2002

A new trap-assisted band-to-band tunneling (TAB) gate current model is proposed to describe the new observed band-to-band tunneling (BBT) induced gate current characteristics of p-channel metal-oxide-semiconductor field effect transistors (PMOSFET's) with ultra-thin gate oxide. Based on this new TAB gate current model, the off-state gate currents of PMOSFET's with various sub-3 nm gate oxides can be well characterized, while the conventional BBT current model is no longer applicable in this regime.
Characterization of Embedded Spiral Inductors in Co-Fired Ceramic Substrates
Authors: Chen Lih-Shan , Hsi Chi-Shiung , Fu Shen-Li , Lin Jiuun-Yih
Published: October 2002

Embedded planarized inductors can be fabricated using the low-temperature co-fired ceramic technique. Larger inductance is obtained when using a spiral pattern, because the mutual inductance between adjacent conductors has a positive sign. In addition, because of their simple geometry and easy fabrication, spiral-type inductors are widely used. For embedded five- and ten-turn spiral coils, the inductances of about 0.3 and 1.2 µH were obtained, respectively. The value of inductance was almost unchanged in the frequency range between 500 kHz and 40 MHz. The quality factor reaches a peak with increasing frequency and then falls. The peak values (about 10 MHz) of the five- and ten-turn spiral coils are about 20 and 32, respectively.
Pinning Effect of Punched-Out Dislocations in Carbon-, Nitrogen- or Boron-Doped Silicon Wafers
Authors: Akatsuka Masanori , Sueoka Koji
Published: October 2002

The pinning effect of punched-out dislocations in carbon-, nitrogen- or boron-doped Czochralski-grown silicon wafers was investigated using an indentation method. The size of a rosette pattern which corresponds to the distance of dislocation movement was measured after heat-treatment without any thermal stress. It was found that the rosette size decreased by carbon, nitrogen and boron doping with a concentration of 2.0×1016–1.4×1017, 5.3×1013–5.3×1014 and 2.0×1018–2.0×1019 atoms/cm3, respectively. The rosette size was approximately proportional to the power -1/3 of carbon, -1/10 of nitrogen and -1/10 of boron concentration, which differed from the reported power of -2/3 of oxygen concentration.
Magnetization Processes in Narrow and Wide Cross-shaped Co/Cu/NiFe Wires
Authors: Kimura Takashi , Wakaya Fujio , Gamo Kenji
Published: October 2002

Wide and narrow cross-shaped wires in the Co/Cu/NiFe trilayer structures were fabricated by using electron-beam lithography, and the magnetization processes were investigated by measuring magnetoresistance (MR) and Hall resistance (HR). The MRs of both the wide and narrow wires showed two values corresponding to the parallel and antiparallel configurations because of the giant MR effects. The observed HR in the wide cross-shaped wire was understood by the magnetization processes in which the magnetizations in the NiFe and Co layers rotate in the same direction. However, the observed HR in the narrow cross-shaped wire indicates that the magnetizations in the NiFe and Co layers rotated in opposite directions. Such magnetization behaviors are explained by considering the dipole interaction between the NiFe and Co layers.
Reduction of Timing Jitter with Active Control in a kHz Regenerative Amplifier of Femtosecond Pulse Ti:Al2O3 Laser
Authors: Miura Taisuke , Takasago Kazuya , Kobayashi Katsuyuki , Zhang Zhigang , Torizuka Kenji , Kannari Fumihiko
Published: October 2002

We measured the timing error of femtosecond pulses amplified by a Ti:sapphire regenerative amplifier operated at a 1 kHz repetition rate using a modified cross-correlation technique. This technique can detect sub-femtosecond timing variation. By actively controlling the amplifier cavity length, we reduced the rms timing jitter of the regenerative amplifier into the sub-femtosecond range.
Triboluminescence of 3,6-Dibromocarbazole
Authors: Wu Wei , Narisawa Takatoshi , Hayashi Shigeo
Published: October 2002

3,6-Dibromocarbazole was identified to be triboluminescent for the first time. From the triboluminescence and photoluminescence spectra, it was found that the room-temperature triboluminescence spectrum of 3,6-dibromocarbazole, unlike most other triboluminescent materials, was different from its photoluminescence spectrum at the same temperature and was composed of a weak tribofluorescence and a strong tribophosphorescence. This result can be ascribed partly to the “heavy atom effect” caused by the two bromine substituents and partly to the change in luminescence quantum yields experienced during the breakage of the crystals. Its symmetry of crystalline structure was determined to belong to the acentric space group using the method of second-harmonic generation.
Temporal Autocorrelation Function of Light Scattered from Aggregated Particles in a Dense Colloidal Suspension
Authors: Katsuhiro Ishii Katsuhiro Ishii , Toshiaki Iwai Toshiaki Iwai
Published: October 2002

We have investigated a temporal amplitude autocorrelation function of multiply backscattered light from aggregated particles in a dense colloidal suspension. It is shown that the measured amplitude autocorrelation function for aggregated particles deviates from the theory of diffusing wave spectroscopy obtained for the multiple light scattering from homogeneously dispersed particles. We introduce a sum of temporal amplitude autocorrelation functions of the single and multiple scatterings as a model of the temporal autocorrelation function. The temporal autocorrelation functions of the single and multiple scatterings can be estimated by means of fitting the experimental data to the model function. Reliable particle sizing of clusters in the dense medium can be performed by employing the multiple scattering autocorrelation function in the short elapsed time and the single scattering autocorrelation function in the long elapsed time from the time when particles begin aggregating. Consequently, we propose a new monitoring method of the particle aggregation and a particle sizing method of clusters in the dense colloidal suspension.
Characterization of Degenerate Four-Wave Mixing in Photorefractive Polymer-Dissolved Liquid Crystal Composites
Authors: Ono Hiroshi , Kitamura Keiko , Kawatsuki Nobuhiro , Norisada Hideki
Published: October 2002

Optical phase conjugation in a high-performance photorefractive polymer-dissolved liquid crystal composite has been observed with a cw frequency-doubled Nd-YAG laser (532 nm) or He–Ne laser (633 nm). The degenerate four-wave mixing experiment enabled measurements of phase conjugate reflectance as a function of input beam intensities, applied electric field, and grating spacing. The refractive index modulation was estimated from the phase conjugate reflectance on the basis of the coupled wave theory including the absorption loss of the photorefractive media. Small input powers were sufficient for inducing a large refractive index modulation around 4.0 ×10-3.
Characterization of the Local Layer Structure of a Narrow Wall in a Surface Stabilized Ferroelectric Liquid Crystal Using Synchrotron X-Ray Micro-Diffraction
Authors: Iida Atsuo , Noma Takashi , Miyata Hirokatsu
Published: October 2002

Synchrotron X-ray microbeam small angle diffraction experiments were carried out for the characterization of the local layer structure of the narrow wall of a zig-zag defect in a surface stabilized ferroelectric liquid crystal cell. A series of the rocking curve (ω) and the azimuthal (χ) intensity distribution profiles were measured as a function of the vertical position across the narrow wall. The local layer was deflected at the wall in the χ direction. For the inclined narrow wall making an angle of a few degrees to 10° with respect to the rubbing direction, the deflected layer bent in both ω and χ directions. At the narrow wall running parallel to the rubbing direction, the layer bent only in the ω direction. The local layer structure was discussed in relation to the surface anchoring effect and a uniformly bent layer structure was proposed to explain experimental results.
The Effect of Homogeneous Short Branching on Chain Folding Behavior
Authors: Masako Iwata Masako Iwata
Published: October 2002

The effect of branch content on chain folding behavior was studied by molecular dynamics simulation. The study was carried out using a single linear chain composed of 300 CH2 units with short branches. The number of branches varied from 0 to 29. The short branches were located homogeneously along the backbone chain. The model polymer was assumed to be ethylene/α-hexene copolymer produced with metallocene polymerization. There was a critical number of branches required to form the ideal folded structure. Most branches in the folded structures were excluded from the crystal region and were located at the folding surfaces. The chain with homogeneous branching could form a stable folded structure with shorter folding length than that with no branches. When the chain without branches folded, the sliding movement promoted thickening. When the chain with branches folded, thickening ceased on the way because branches inhibited the sliding movement of the chain.
Low-Temperature Epitaxial Growth of Cubic Silicon Carbide on Si(100) for Submicron-Pattern Fabrication
Authors: An Sung-Jae , Yi Gyu-Chul
Published: October 2002

SiC films were selectively grown on patterned SiO2/Si(100) substrates using supersonic molecular jet epitaxy. For film growth, we employed methylsilane seeded in a carrier gas (He or H2) as a reactant gas. Due to the high translational kinetic energy of methylsilane molecules in the supersonic jet, the growth temperature was as low as 670°C. The reduction of the growth temperature is explained in terms of a decrease in the activation energy and enhancement of the reaction efficiency from methylsilane to the SiC film during film growth. More importantly, a high growth rate of SiC at low temperature yielded submicron patterns of SiC without degradation of the SiO2 mask.
Fabrication and Structure of Langmuir–Blodgett Films of Nitrostilbene
Authors: Hiroyuki Kaji Hiroyuki Kaji , Yuhei Shimoyama Yuhei Shimoyama
Published: October 2002

Using the dilution technique of the developing solution as well as the flow-orientation method, we successfully fabricated a well-ordered Langmuir monolayer and Langmuir–Blodgett (LB) films of 4-dimethylamino-4′-nitrostilbene (DANS). The dilution technique of developing solutions allows formation of a two-dimensional film of DANS below a certain concentration. The flow-orientation method enhances the molecular orientation in the monolayer by means of a moving barrier. X-ray diffraction (XRD) suggested that the DANS monolayers form the tilt stacking in the LB films. Ultraviolet visible (UV-VIS) spectra of the LB films showed a peak shift to the shorter wavelength as compared with those of the DANS solution. The blue shift of the UV-VIS spectra reflected the enhanced molecular packing of the nitrostilbene chromophore. Both the XRD and UV-VIS data are indicative that DANS tilts to the substrate normal.