bluuebunny/crossref_metadata_2025 huggingface dataset:
Electrical Characteristics of Schottky Contacts on GaN and Al0.11Ga0.89N
Authors: Arulkumaran Subramaniam , Egawa Takashi , Zhao Guang-Yuan , Ishikawa Hiroyasu , Jimbo Takashi , Umeno Masayoshi
Published: October 2002

The electrical characteristics of Ag, Ti, Au, Pd and Ni Schottky contacts on GaN
and Al0.11Ga0.89N grown by metalorganic chemical vapour deposition (MOCVD)
on sapphire substrates have been investigated. Al0.11Ga0.89N Schottky
barrier height values are bit higher than the values of GaN contacts except Ti Schottky
contacts. Fermi-level pinning has been observed for both GaN and
Al0.11Ga0.89N Schottky contacts. The pinning degree of GaN and
Al0.11Ga0.89N are much less than GaAs, Si and GaP, but both of them may be
similar to CdS.
Improvement of Annealing Properties of SiC/Si Structure
Authors: Yong Sun Yong Sun , Tatsuro Miyasato Tatsuro Miyasato
Published: October 2002

Properties of the SiC film/Si substrate structure annealed in a hydrogen atmosphere are investigated by scanning electron microscopy observation, X-ray diffraction measurement and Auger electron spectroscopy analysis. Two types of defects, the line and point defects which are formed in vacuum annealing, are also observed in the SiC/Si structure annealed in hydrogen-atmosphere, but the density of the point defects is little. The hydrogen atmosphere annealing results in high crystallinity of the SiC film, and low compositional change at the surface of the SiC film.
Temperature Dependence of Barrier Height and Energy Bandgap in Au/n-GaSb Schottky Diode
Authors: Lin Chuing-Liang , Su Yan-Kuin , Chang Jia-Rong , Chen Shi-Ming , Li Wen-Liang , Jaw Dun-Hua
Published: October 2002

The temperature dependence of barrier height and energy bandgap in Au/n-GaSb
Schottky diode was first determined in a wide temperature range (156–316 K) by
photoresponse measurement. While the energy bandgap of n-GaSb decreases from
0.79 eV to 0.73 eV with an increase in temperature (from 156 K to 316 K), the barrier
height of Au/n-GaSb also decreases from 0.69 eV to 0.57 eV. Though sulfide
treatment was taken to modify the metal-semiconductor interface, Fermi level at the
interface was almost pinned (0.1–0.16 eV) above the valence band edge. Similar to
semiempirical Varshni's law, using our experimental fitting, we obtained the
temperature expressions of the barrier height and the energy bandgap of Au/n-GaSb
Schottky diode.
Effects of Oxygen Vacancy Diffusion on Leakage Characteristics of Pt/(Ba0.5Sr0.5)TiO3/Pt Capacitor
Authors: Maruno Shigemitsu , Murao Takeshi , Kuroiwa Takeharu , Mikami Noboru , Tomikawa Akihiko , Nagata Michihiko , Yasue Tsuneo , Koshikawa Takanori
Published: October 2002

We investigated leakage characteristics of Pt/(Ba0.5Sr0.5)TiO3(BST)/Pt capacitors
by measuring current-voltage characteristics during annealing in vacuum and
atmosphere. Built-in electric fields (E
i) generated at Pt/BST interfaces are
derived from analysis of the leakage currents based on the Schottky conduction
mechanism. It was found that E
i varies in proportion to the square root of
annealing time (√ t). In addition, we found that an external electric field
applied during annealing in vacuum induces asymmetric degradation in the
leakage characteristics at the top and bottom Pt/BST interfaces. Such behavior in
the leakage characteristics is interpreted in terms of the diffusion of oxygen
vacancies at the interfaces. Diffusivity of oxygen vacancies is determined from
E
i-√ t curves.
Thermal Analysis on the Amorphous Carbon Nitride Prepared by Reactive Magnetron Sputtering
Authors: Xiao Xing-Cheng , Jiang Wei-Hui , Song Li-Xin , Hu Xing-Fang , Lu Chang-Wei
Published: October 2002

The differential thermal analysis-thermogravimetry-mass spectroscopy (DTA-TG-MS) study on the thermal stability of CN
x
prepared by magnetron sputtering was carried out
under Ar atmosphere. The results show that the decomposition process could be divided into two stages.
One spans from room temperature (RT) to 800°C. The nitrogen loss as well as the weight loss in the a-CN
x
could be attributed
to the evaporation of C+(m/z=12), CN+(m/z=26), O2
+(m/z=32), CO2
+(m/z=44), NO2
+(m/z=46), and
C2N2
+(m/z=52), as detected by mass spectroscopy. The other is above 800°C, during which the breakage of
C–N bonds and the oxidation of C and N mainly accounts for the weight loss. The weight loss of a-CN
x
is
7% for the first stage and 42.8% for the second, suggesting the a-CN
x
to be more stable at low temperature.
500-nm-Resolution 10 keV X-Ray Imaging Transmission Microscope with Tantalum Phase Zone Plates
Authors: Kagoshima Yasushi , Ibuki Takashi , Takai Kengo , Yokoyama Yoshiyuki , Miyamoto Naoki , Tsusaka Yoshiyuki , Matsui Junji
Published: October 2002

An imaging transmission hard X-ray microscope has been constructed at the
Hyogo-BL (BL24XU) of SPring-8. It makes use of X-ray phase zone plates (PZP's)
made of tantalum as its condenser and objective lenses. The objective PZP has an
outermost zone width of 250 nm, which corresponds to the theoretically expected
spatial resolution of 300 nm. An experiment was performed at the photon energy of 10 keV to
check the performance of the microscope. Since a 250 nm line-and-space pattern
was clearly resolved, we concluded that the microscope attained a spatial resolution
limit better than 500 nm. A few samples were also examined and the feasibility of the
microscope was successfully demonstrated.
Magnetic Promotion and Quenching of Surface Oxidation with Pt Catalyst
Authors: Wakayama Nobuko I.
Published: October 2002

A gradient magnetic field which was not homogeneous was found to have a significant effect
on a surface oxidation performed with platinum catalyst. When a fuel gas flowed in the
direction of decreasing magnetic strength, surface oxidation was found to be promoted. On
the other hand, when a fuel gas flowed in the direction of increasing magnetic strength, the
reaction was quenched. These magnetic effects were explained by the movement of the
reactants and chemical products in and from the reaction zone caused by the magnetic forces
under magnetic-field gradients. The present results suggest a novel method to efficiently
control oxidation reactions on the surface of catalyst.
Room Temperature 339 nm Emission from Al0.13Ga0.87N/Al0.10Ga0.90N Double Heterostructure Light-Emitting Diode on Sapphire Substrate
Authors: Otsuka Nobuyuki , Tsujimura Ayumu , Hasegawa Yoshiaki , Sugahara Gaku , Kume Masahiro , Ban Yuzaburoh
Published: October 2002

Room-temperature deep-ultraviolet emission has been observed
from Al0.13Ga0.87N/Al0.10Ga0.90N double
heterostructure light-emitting diodes (LEDs) on (0001)-oriented
sapphire substrate. By introducing undoped barrier layers, which
sandwich the active layer, the LED was operated at a peak emission
wavelength of 339 nm with a narrow linewidth of 5.6 nm. The
dependence of emission intensity on injection current suggests that
the nonradiative recombination was suppressed and the diffusion
current for the recombination process was dominant at the injection
current of over 20 mA.
Buried Tungsten Metal Structure Fabricated by Epitaxial-Lateral-Overgrown GaN via Low-Pressure Metalorganic Vapor Phase Epitaxy
Authors: Haino Masahiro , Yamaguchi Motoo , Miyake Hideto , Motogaito Atsushi , Hiramatsu Kazumasa , Kawaguchi Yasutoshi , Sawaki Nobuhiko , Iyechika Yasushi , Maeda Takayoshi
Published: October 2002

A buried tungsten (W) structure with GaN is successfully
obtained by epitaxial lateral overgrowth (ELO) technique via
low-pressure metalorganic vapor phase epitaxy (LP-MOVPE). The
selectivity of GaN growth on the window regions is excellent. GaN
with a striped W metal pattern is easily decomposed above the low
temperature of 500°C by the catalytic effect of W. It is
difficult to bury the W mask because severe damage occurs in the GaN
epilayer under the mask. It is found that employing an underlying
AlGaN/GaN heterostructure with a narrow W stripe mask width
(L/S=2/2 µm) leads the epilayer to be free from
damage, resulting in a good W buried structure.
Simplified High-Electric-Field Technique for Measuring the Liquid Crystal Anchoring Strength
Authors: Yokoyama Hiroshi , Sun Ruipeng
Published: October 2002

A simple passive approach, employing a small current-regulating capacitor connected in series with a
liquid crystal cell, is proposed and its utility demonstrated as a new
scheme of implementing the high-electric-field technique (HEFT) for
determining the surface anchoring strength of liquid crystals.
The series capacitor removes the cumbersome need for measuring the
cell capacitance at high fields
from the HEFT, thereby drastically simplifying the operation. The
simplified HEFT allows a direct
linear relation between the optical phase retardation and the
reciprocal of the applied voltage, and as in
the original HEFT, the linear extrapolation of this relationship to
infinite voltage provides the
anchoring strength.
Optimum Atomic Spacing for AlAs Etching in GaAs Epitaxial Lift-Off Technology
Authors: Rao Kota S. R. Koteswara , Katayama Takeshi , Yokoyama Shin , Hirose Masataka
Published: October 2002

With respect to GaAs epitaxial lift-off technology, we report here the optimum atomic spacing (5–10 nm) needed to etch off the AlAs release layer that is sandwiched between two GaAs epitaxial layers. The AlAs etching rate in hydrofluoric acid based solutions was monitored as a function of release layer thickness. We found a sudden quenching in the etching rate, approximately 20 times that of the peak value, at lower dimensions (∼2.5 nm) of the AlAs epitaxial layer. Since this cannot be explained on the basis of a previous theory (inverse square root of release layer thickness), we propose a diffusion-limited mechanism to explain this reaction process. With the diffusion constant being a mean-free-path-dependent parameter, a relation between the mean free path and the width of the channel is considered. This relation is in reasonable agreement with the experimental results and gives a good physical insight to the reaction kinetics.
Photoinduced Damage in Gd1-XYXCa4O(BO3)3 Crystals
Authors: Nakao Hiroshi , Ruan Yongfeng , Furuya Hiroyuki , Yamada Itsunari , Yoshimura Masashi , Mori Yusuke , Sasaki Takatomo
Published: October 2002

Gd1-X
Y
X
Ca4O(BO3)3 (GdYCOB) crystal has
considerable potential as a noncritically phase-matched
third-harmonic generator of Nd:YAG lasers. However, during
high-power third-harmonic generation (THG), THG performance was
limited by photoinduced damages. We observed two
kinds of photoinduced damages. One was a “gray-track” that was
formed during high-peak-power THG. Another was photorefractive
damage that was induced by high-repetitive THG. Electron
paramagnetic resonance (EPR) measurement suggested that the
gray-tracking was related to Y2+ ions that converted from Y3+ by
exposure to UV light.
Liquid Crystal Alignment with a Photo-Crosslinkable and Solvent-Soluble Polyimide Film
Authors: Lee Wen-Chin , Hsu Chain-Shu , Wu Shin-Tson
Published: October 2002

A new photo-crosslinkable and solvent-soluble polyimide containing cinnamate
side chains (PICA) was developed for aligning nematic liquid crystals (LCs). Good LC
alignment was achieved by exposing a long-wave linearly polarized ultraviolet (LPUV)
light to the PICA film. The LC alignment direction is found perpendicular to the
polarization axis of the incident LPUV light. The uniform alignment of LC molecules
induced by PICA films remains intact after being heated at 85°C for 450 hours. A
small pretilt angle on the PICA film was generated by the double exposure method.
Epitaxial Growth of CaxCd1-xF2 Mixed Crystal Films on Si Substrates
Authors: Takuji Gotoh Takuji Gotoh , Hiroshi Kambayashi Hiroshi Kambayashi , Kazuo Tsutsui Kazuo Tsutsui
Published: October 2002

Mixed crystal films of CaxCd1-x
F2 were epitaxially grown on Si(111) substrates covered with a thin CaF2 buffer layer. Using the molecular-beam epitaxy method, 110-nm-thick mixed crystal films were grown at 200°C on 10-nm-thick CaF2 buffer layers on Si(111). Rutherford backscattering spectroscopy revealed that the composition of the mixed crystal layer, x, was consistent with the flux ratio of a CaF2 molecular beam and a CdF2 molecular beam, and that channeling minimum yields of less than 20% were obtained for the entire range of composition (x=0 to x=1). Very smooth surface morphology with 0.29 nm of rms was obtained for the x=0.31 layer, compared to those of pure CaF2 or CdF2 layers grown at the same growth temperature.
Preservation of Periodically Poled Structures in Zn-Diffused LiNbO 3 Waveguides
Authors: Rubén Nevado Rubén Nevado , Eugenio Cantelar Eugenio Cantelar , Ginés Lifante Ginés Lifante , Fernando Cussó Fernando Cussó
Published: October 2002

In this work, the formation of optical waveguides in periodically poled lithium niobate (PPLN) substrates by Zn-diffusion from vapour phase is studied. It has been found that the diffusion of the Zn ions is homogeneous in the PPLN substrates and the optical waveguides can be fabricated with the same parameters used in single-domain lithium niobate. The periodic ferroelectric domain pattern initially present in the substrate is preserved in the waveguides.
Slip-Free Rapid Thermal Processing in Single Wafer Furnace
Authors: Yoo Woo Sik , Fukada Takashi , Kitayama Hirofumi , Takahashi Nobuaki , Enjoji Keiichi , Sunohara Kiyoshi
Published: October 2002

Defect generation phenomena in Si wafers during atmospheric
pressure rapid thermal processing (RTP) in a single wafer furnace
(SWF) are investigated as a function of temperature, process time,
wafer handling method and speed. The size, shape and spatial
distribution of crystal defects generated during RTP were
characterized using an optical microscope and X-ray
topography. The wafer handling method and speed are found to be very
important in controlling defect generation during RTP under given
process conditions. Highly reproducible slip-free RTP results were
achieved in 200-mm-diameter Si wafers processed at 1100°C for 60 s (up to 5 times) by optimizing the wafer handling method and speed.
Josephson Junction Array for the Measurement of High-Frequency Magnetic Fields
Authors: Enpuku Keiji , Ohta Shusaku , Nakahodo Atsushi , Minotani Tadashi
Published: October 2002

We propose the use of a high-T
c Josephson junction array for the
measurement of high-frequency magnetic fields with high spatial resolution. The
voltage vs magnetic field (V–B) relationship of the bicrystal junction was studied
for this purpose. The junction array fabricated with an area of 120 µm by
50 µm showed the conversion efficiency dV/dB=63 V/T at
T=77 K. This value indicates that the junction array is more sensitive, up to
1.7 GHz, than the conventional induction coil having the same area. Measurement of the
magnetic field with a frequency of 130 MHz was successfully demonstrated using the
junction array. Performance of the junction array will be much improved by decreasing
the operational temperature.
Diamagnetic Anisotropy of Simple Inorganic Oxides Composed of Octahedral Networks Detected by Field-Induced Harmonic Oscillation in the High-Temperature Region
Authors: Uyeda Chiaki , Ohtawa Kouichi , Okita Kazuyuki
Published: October 2002

The detection of small diamagnetic anisotropy for five basic oxides is realized by
measuring the field-induced harmonic oscillation in the temperature range from 300 K
to 800 K. The Δχ-T relationship enables the quantitative evaluation
of diamagnetic anisotropy even if paramagnetic ions are present in the sample, which
is generally the case for actual samples. The maximum anisotropy values between two
magnetic principal axes are (1.1±0.2)×10-8 emu/g for muscovite,
KAl2[Si3AlO10](OH)2, (2.2±0.3)×10-7 emu/g for
talc, Mg3[Si4O10](OH)2, (2.6±0.2)×10-9 emu/g for
brucite, Mg(OH)2, (1.4±0.2)×10-9 emu/g for gibbsite, Al(OH)3,
and (4.2±0.3)×10-9 emu/g for diaspore, AlOOH.
Low-Temperature Thermoelectric Properties of the Composite Crystal [Ca 2CoO 3.34] 0.614[CoO 2]
Authors: Yuzuru Miyazaki Yuzuru Miyazaki , Kazutaka Kudo Kazutaka Kudo , Megumi Akoshima Megumi Akoshima , Yasuhiro Ono Yasuhiro Ono , Yoji Koike Yoji Koike , Tsuyoshi Kajitani Tsuyoshi Kajitani
Published: October 2002

Electric resistivity, thermoelectric power and thermal conductivity
of a polycrystalline sample of the composite crystal
[Ca2CoO3.34]0.614[CoO2], also known as Ca3Co4O9,
have been measured below 300 K. Metallic conductivity accompanied by large
thermoelectric power has been observed down to 50 K. At 300 K, the
sample exhibits a thermoelectric power of S = 133 µV·K-1,
resistivity of ρ= 15 mΩ·cm and thermal conductivity of
κ= 9.8 mW·K-1·cm-1.
The resulting dimensionless figure of merit becomes
Z
T
300 = 3.5×10-2, which is comparable to the value reported
for a polycrystalline sample of NaCo2O4, indicating that the title compound is a potential
candidate for a thermoelectric material.
Structural Properties of TiC/Fe Nanoscale Multilayers Synthesized by the Ion-Beam Sputtering Technique
Authors: Wang Jing , Li Wen-Zhi , Li Heng-De
Published: October 2002

TiC/Fe multilayers with modulation wavelengths ranging from 3.5 nm to
20.6 nm were prepared by the ion-beam sputtering deposition technique at nearly
ambient temperature. It was found that the multilayers with relatively low modulation
wavelengths exhibited epitaxial-like growth. The orientation was (200)TiC//(200)Fe
and [001]TiC//[011]Fe. With increasing modulation wavelength, the TiC/Fe multilayers
underwent a transition from epitaxial-like superlattices to uniaxial textured
polycrystalline multilayers. A possible explanation is discussed.
Sputtering Highly C-Axis-Oriented AlN Films on Y-128° LiNbO3
Authors: Wu Long , Chen Ping-Cheng , Wu Sean , Song Hong-Tie , Chure Ming-Cherng
Published: October 2002

Highly c-axis-oriented aluminum nitride (AlN) films were successfully
prepared, without heating the substrate, on Y-128° LiNbO3 substrate by
rf magnetron sputtering. The dependence of the sputtering pressure and the physical
structures of the films (crystalline structure and micromorphology) were investigated.
The results showed that the highly c-axis-oriented AlN films appeared at the lower
sputtering pressures and the films with the best orientation and microstructure were
prepared at 3 m Torr. The deposition rate also increased as the sputtering pressure
decreased.
Material Design for Transparent Ferromagnets with ZnO-Based Magnetic Semiconductors
Authors: Kazunori Sato Kazunori Sato , Hiroshi Katayama-Yoshida Hiroshi Katayama-Yoshida
Published: October 2002

Ferromagnetism of ZnO-based magnetic semiconductors was investigated by
ab initio calculations based on the local density approximation.
In a system of Mn atom doped ZnO, the ferromagnetic ordering of Mn magnetic moments
was induced by hole doping. It was also found that 3d transition metal atoms
of V, Cr, Fe, Co and
Ni showed the ferromagnetic ordering of their magnetic moments in ZnO without any additional
carrier doping treatments.
Appearance of the ferromagnetism in these systems
suggests possibility for a fabrication of a transparent ferromagnet which will have
great impact on industrial applications in magneto optical devices.
Phosphorus Vacancy as a Deep Level in AlInP Layers
Authors: Sung Wei-Jer , Wu Yu-Rue , Lee Shih-Chang , Wen Tzu-Chi , Li Tsang-Jou , Chang Jung-Ting , Lee Wei-I.
Published: October 2002

Deep levels in AlInP layers, grown by metal-organic chemical vapor deposition
(MOCVD) with various V/III mole ratios, have been carefully investigated by deep-level
transient spectroscopy (DLTS). A deep level originating from phosphorus vacancy was
observed with the activation energy of 0.65 eV. Examining this
phosphorus-vacancy-related deep level provided a relatively simple means of
understanding the phosphorus vacancy in AlInP, thus allowing us to determine an
appropriate V/III mole ratio for growing AlInP.
Wafer Fusion Technique Applied to GaN/GaN System
Authors: Tokuda Takashi , Noda Susumu
Published: October 2002

The wafer fusion technique is applied to a GaN/GaN system for the first time.
The processing conditions for successful wafer fusion are clarified. The lowest
annealing temperature for successful fusion of GaN/GaN is 500°C. It is found that
surface smoothness and a large weighting pressure are essential to achieve both a
uniform interface and better reproducibility. The electric property of the fused
interface is also characterized. Current–voltage (I–V) characteristics of the
n-GaN/n-GaN and p-GaN/p-GaN fused interface reveal that a pinning effect of the
Fermi level exists at the fused interface.
Strained Si1-xGex Normal-Graded Channel P-Type Metal Oxide Semiconductor Field Effect Transistor
Authors: Su Chia Yi , Wu San Lein , Chang Shoou Jinn , Chen Liang Po
Published: October 2002

A working p-type metal-oxide semiconductor field-effect transistor (MOSFET)
structure, utilizing a graded-Si1-x
Ge
x
layer as the conducting channel, has
been successfully fabricated by ultra high-vacuum chemical vapor deposition (UHVCVD).
Rapid thermal oxidation (RTO) was used to obtain a high-quality thin-gate oxide films
and decrease the high thermal budget which results in the strain relaxation of the
graded Si1-x
Ge
x
layer. It is found that the proposed device exhibits suitable
transistor characteristics. An extrinsic transconductance of 130 mS/mm at room
temperature for a gate length of 0.6 µm has been obtained, which shows the great
potential of this structure in Si-based device applications.
Frequency Domain Measurement for Relaxation Study on Optical Kerr Effect
Authors: Oki Yutaka , Sakamoto Naoto , Sakai Keiji , Takagi Kenshiro
Published: October 2002

The modulated output of a cw Ar+ laser was used in the relaxation study of the optical Kerr effect. A He–Ne probe laser detected a delayed response of the induced birefringence, which yielded the complex relaxation spectra over a frequency range from 10 kHz to 2 MHz. The system was applied to 6CB, a nematogen, in its isotropic phase at temperatures down to T
c, and the result showed a single relaxation, which was well fitted to a Cole-Cole plot. The relaxation strength and the characteristic time constant followed the temperature dependence of 1/(T-T
*), T
* being the virtual transition point predicted by the Landau-de Gennes theory.
A New Micromachined Bandpass Filter on a Quartz Substrate
Authors: Kyoung-Youl Park Kyoung-Youl Park , Ji-Yong Park Ji-Yong Park , Jong-Chul Lee Jong-Chul Lee , Jae-Yeong Park Jae-Yeong Park , Geun-Ho Kim Geun-Ho Kim , Dong-Wook Kim Dong-Wook Kim , Jong-Uk Bu Jong-Uk Bu , Ki-Woong Chung Ki-Woong Chung
Published: October 2002

A new class of three dimensional(3D) micromachined microwave planar filter at K-band is presented. The filter shows a wide bandpass chracteristic of 36% with the insertion loss of 1.2 dB at 19.11 GHz, and can be applicable in high power monolithic microwave integrated circuits (MMIC).
Electron Emission from Graded AlxGa1-xN/GaN Negative-Electron-Affinity Cold Cathodes
Authors: Deguchi Masahiro , Uenoyama Takeshi
Published: October 2002

A new cold cathode based on Schottky junction using the III-V nitride semiconductor which exhibits negative-electron-affinity (NEA) was proposed. The cold cathode was composed of non-doped graded Al
x
Ga1-x
N/n-type GaN layers grown by metal organic chemical vapor deposition (MOCVD) on sapphire (0001) substrates and thin surface electrode acting as Schottky contact. A part of electrons led to the NEA Al
x
Ga1-x
N surface smoothly by band-engineering, in which Al composition x increased continually toward the surface from the n-GaN side, was emitted through the thin surface electrode. The emission current of a few µA/cm2 was observed under forward bias of about 5 V for the III-V nitride Schottky junction.
Current-Induced Joule Heating Used to Crystallize Silicon Thin Films
Authors: Toshiyuki Sameshima Toshiyuki Sameshima , Kentaro Ozaki Kentaro Ozaki
Published: October 2002

Electrical-current-induced joule heating was applied to the crystallization of 60-nm-thick amorphous silicon films formed on glass substrates. Three-µs-pulsed voltages were applied to silicon films connected with a capacitance in parallel. Coincident irradiation with a 28-ns-pulsed excimer laser melted films partially and reduced their resistance. Complete melting for 12 µs and a low cooling rate of 1.1×108 K/s were achieved by joule heating from electrical energy that accumulated at a capacitance of 0.22 µF. The analysis of electrical conductivity suggested a density of defect states of 1.5×1012 cm-2 at grain boundaries. The formation of 3.5-µm-long crystalline grains was observed using a transmission electron microscope. The preferential crystalline orientation was (110).
Strains in InAs Quantum Dots Embedded in GaAs: A Finite Element Study
Authors: Muralidharan Govindarajan
Published: October 2002

Strains in InAs quantum dots embedded in GaAs have been examined using a 2-D axi-symmetric finite element method within a thermo-mechanical framework. The initial shape of the dot was assumed to be conical in 3-D. Results show that the shape and the width/height ratio are critical in determining the strains within the quantum dots. Results of the calculation are compared with the results of other calculations and experimental measurements of strains using the scanning tunneling microscope (STM).
Two Components in Femtosecond Optical Response of Y0.7Pr0.3Ba2Cu3O7-δ Thin Films in Superconducting State
Authors: Shigeki Nashima Shigeki Nashima , Masayoshi Tonouchi Masayoshi Tonouchi , Masanori Hangyo Masanori Hangyo , Kai-Uwe Barholz Kai-Uwe Barholz , Frank Schmidl Frank Schmidl , Paul Seidel Paul Seidel
Published: October 2002

We studied the optical response of Y0.7Pr0.3Ba2Cu3O7-δ (YPBCO) thin films by means of a femtosecond time-resolved pump-probe method, and found that its response quite differs significantly from that of YBa2Cu3O7-δ (YBCO) thin films. It is revealed that there are two components in the transient reflectivity change ΔR(t)/R of the YPBCO thin film in the superconducting state. The temperature dependence of ΔR(t)/R suggests that the one component originates from the photoexcitation of superconducting layers and the other originates from that of normal layers. The origin of these two components is discussed in relation to the electronic structure of YPBCO.
An Artificial Retina LSI with 5000 Frames per Second On-Sensor Projection Function
Authors: Funatsu Eiichi , Kuramochi Soichiro , Nagafuchi Yoji , Kage Hiroshi , Sakashita Narumi , Murao Fumihide , Kyuma Kazuo
Published: October 2002

Our artificial retina (AR) LSI executes high-accuracy on-sensor image projection. The fabricated 32×32 pixel AR LSI compresses 1024 bytes image data to 64 bytes data, which reduces the image-processing load of the subsequent processing part. A motion detection system was developed through combination with an 8-bit microcontroller. This motion detection system outputted motion data at the rate of 50 reports/s for high-speed motion, corresponding to a 200 µs time difference. This high-speed image detection was attained also by the high sensitivity of 20 V/lx·s and the wide dynamic range of 66 dB.
A New Method of Determining Short-Range Order Parameter in Relaxor Pb(Ni1/3Nb2/3)O3 by Magnetic Susceptibility Measurement
Authors: Shirakami Tatsuya , Mitsukawa Michihiro , Imai Takahito , Urabe Kazuyori
Published: October 2002

We synthesized Pb(Ni1/3Nb2/3)O3 (PNN) and performed selected-area electron diffraction (SAD) in order to investigate the structure of the B-site array. In addition to the reflection from the basic cell, the SAD pattern of sintered PNN corresponds to the reciprocal plane normal to the [011] zone axis and showed diffuse scatterings at (½½½) positions. We also measured the magnetic susceptibility of PNN and discussed the short-range ordering around Ni2+ ions by analyzing the susceptibility based on a simple model.
Increase of Azimuthal Anchoring Energy and Thermal Stability at Homogeneously Orientated Liquid Crystal/Polymer Interface
Authors: Sato Rumiko Yamaguchi
Published: October 2002

A surface memory effect appears on isotropic polymer surfaces when the polymer surface is exposed to a homogeneously orientated nematic liquid crystal (LC), and an azimuthal anchoring energy of the surface increases with exposure time. The increase of the anchoring energy is also observed in the homogeneous LC cell with rubbed polymer substrates, but not in the twisted nematic (TN) cell. Alignment surfaces in the homogeneous LC cell become stable against heating above the glass transition temperature of the polymer, in contrast to the thermal instability in the TN cell. These results reveal that the LC bulk orientation actively influences the polymer molecular orientation at the LC/polymer interface.
Growth of Thick Hexagonal GaN Layer on GaAs (111)A Surfaces for Freestanding GaN by Metalorganic Hydrogen Chloride Vapor Phase Epitaxy
Authors: Yoshinao Kumagai Yoshinao Kumagai , Hisashi Murakami Hisashi Murakami , Akinori Koukitu Akinori Koukitu , Kikurou Takemoto Kikurou Takemoto , Hisashi Seki Hisashi Seki
Published: October 2002

Thick hexagonal GaN was grown on GaAs (111)A surfaces by metalorganic hydrogen chloride vapor phase epitaxy (MOHVPE) in the temperature range from 920°C to 1000°C. Both the surface morphology and the photoluminescence (PL) property of the grown layer were greatly improved with increase of the growth temperature up to 1000°C. However, the full-width at half maximum (FWHM) in the ω mode X-ray diffraction (XRD) of the GaN (0002) plane increased with increasing growth temperature above 960°C, due to the bending of the grown layer. The bending could be suppressed by growing a thicker layer, even at 1000°C. A mirror-like GaN layer with the FWHM value of 4.7 min was obtained by growing a 100-µm-thick layer at 1000°C, which indicates that the growth of a thick GaN layer on the GaAs (111)A surface is a promising method for the preparation of freestanding GaN substrates.
DC and RF Performance of 50 nm Gate Pseudomorphic In0.7Ga0.3As/In0.52Al0.48As High Electron Mobility Transistors Grown on (411)A-Oriented InP Substrates by Molecular-Beam Epitaxy
Authors: Masataka Higashiwaki Masataka Higashiwaki , Takahiro Kitada Takahiro Kitada , Toyohiro Aoki Toyohiro Aoki , Satoshi Shimomura Satoshi Shimomura , Yoshimi Yamashita Yoshimi Yamashita , Akira Endoh Akira Endoh , Kohki Hikosaka Kohki Hikosaka , Takashi Mimura Takashi Mimura , Toshiaki Matsui Toshiaki Matsui , Satoshi Hiyamizu Satoshi Hiyamizu
Published: October 2002

In this paper, we report on the material and device characteristics of pseudomorphic In0.7Ga0.3As/In0.52Al0.48As high electron mobility transistors (HEMTs) grown on a (411)A-oriented InP substrate by molecular-beam epitaxy. The electron Hall mobility in the (411)A HEMT was 2.5 times higher at 15 K and 1.3 times higher even at room temperature than that in a HEMT grown on a conventional (100) InP substrate. The (411)A HEMTs with 50 nm gates provided excellent DC and RF device characteristics.The maximum transconductance was as high as 1.1 S/mm, and the cutoff frequency reached 355 GHz.
Fabrication of Ramp-Edge Junction with NdBa2Cu3Oy-Based Interface-Modified Barrier
Authors: Takehiko Makita Takehiko Makita , Kazuyoshi Toma Kazuyoshi Toma , Kazuhiro Ishikawa Kazuhiro Ishikawa , Hideaki Zama Hideaki Zama , Hiroyoshi Tano Hiroyoshi Tano , Keiichi Tanabe Keiichi Tanabe
Published: October 2002

We report on the first successful fabrication of ramp-edge junctions with an NdBa2Cu3Oy (NBCO)-based interface-modified barrier in which a YBa2Cu3Oy (YBCO) film is employed as a counterelectrode. The interface-modified barrier on the NBCO ramp surface is formed by electron cyclotron resonance (ECR) ion etching and subsequent annealing treatments to the ramp surface. By annealing at a slightly higher temperature than that for a YBCO-based interface-modified barrier just before counterelectrode growth, resistively shunted junction type current–voltage (I–V) characteristics with the I

c

R

n
product at 4.2 K of approximately 1.6 mV are obtained. These results suggest that NBCO as well as YBCO can be used in high-quality ramp-edge
junctions.
Broadband Antireflection Gratings for Glass Substrates Fabricated by Fast Atom Beam Etching
Authors: Kanamori Yoshiaki , Kikuta Hisao , Hane Kazuhiro
Published: October 2002

We fabricated a two-dimensional subwavelength-structured (SWS) surface on a glass substrate. The SWS surface was patterned by electron-beam lithography and etched by an SF6 fast atom beam. The SWS surface consisted of tapered gratings with a 150 nm period and a 150 nm deep groove. The reflectivity at wavelengths from 400 nm to 2000 nm was measured and compared with the results calculated on the basis of rigorous coupled-wave analysis. At wavelengths from 400 nm to 800 nm, the reflectivity of the glass surface decreased to 1% from the original value of 5% of the glass substrate. The reflectivity was also examined as a function of the incident angle by using He–Ne laser light.
All-Optical Inverted Operational Amplifier Derived from the Negative Nonlinear Absorption Effect
Authors: Maeda Yoshinobu
Published: October 2002

An all-optical inverted operational amplifier derived from the negative nonlinear absorption effect in an erbium-yttrium aluminum garnet crystal was realized using an erbium-doped fiber amplifier and a feedback ring resonator. The inverted output modulation degree depended on the fiber amplifier gain and increased abruptly at a gain of more than 25 dB. The maximum value of the output modulation degree was 91% when the input modulation degree was 52%. The inverted output power was amplified by approximately 28 times the input power of 25 µW. A NOR-type logic gate operation was demonstrated using two optical signals of 1.53 µm.
Wide Viewing Angle Active Matrix Liquid Crystal Displays Based on a Single Discotic Compensation Film
Authors: Leenhouts Frans
Published: October 2002

One of the methods of widening the viewing angle of twisted nematic liquid crystal displays (TN LCDs) is to apply a discotic compensation film between the front polariser and the front substrate and between the rear polariser and rear substrate. A wide-viewing-angle solution is proposed, which is based on a single discotic film. The use of a single film instead of two leads to a considerable reduction in cost.
CHF3 Plasma Treatment of Si Field Emitter Arrays For No Damage Vacuum Packaging
Authors: Masayoshi Nagao Masayoshi Nagao , Hisao Tanabe Hisao Tanabe , Takashi Matsukawa Takashi Matsukawa , Seigo Kanemaru Seigo Kanemaru , Junji Itoh Junji Itoh
Published: October 2002

Si field emitter arrays (FEAs) are promising cold cathodes for field emission displays (FEDs). The emission current from the Si FEAs, however, is known to decrease significantly after the vacuum-packaging process based on the frit sealing technique. In this work, we have investigated the mechanism of the current decrease and found that CHF3 plasma treatment of the tip surface was sufficiently effective to prevent the problem. In the experiment, the Si FEAs were exposed to the CHF3 plasma for 15 s and then treated by the same process as that for the frit sealing at various temperatures. No changes in the emission current were observed before and after the frit sealing process at temperatures up to 430°C. Details of the CHF3 plasma treatment are described.
Effects of Redox Treatment on Diamondlike Carbon Coated Mo Substrates
Authors: Yokoyama Chin-Maw Lin , I-Nan Lin I-Nan Lin
Published: October 2002

We have studied the effects of oxidation-reduction (redox)
treatment applied to Mo substrates on the characteristics of the
subsequently deposited diamondlike carbon (DLC) films. Atomic force
microscopic (AFM) analyses revealed that the surface of Mo
substrates became rougher after the redox treatment. The
subsequently deposited DLC films inherited the surface morphology of
the Mo substrates. The electron emission characteristics of DLC
films coated on redox Mo substrates are superior to those of DLC
films coated on normal Mo films which is ascribed to the increase in
the field enhancement factor of the DLC films.
White Light Emission from a Polymer-Macromolecule Blend System Due to Energy and Charge Transfer
Authors: List Emil J. W. , Leising Günther , Schulte Niels , Schlüer Dieter A. , Scherf Ullrich , Graupner Willi
Published: October 2002

The emission color of organic-light-emitting diodes (OLEDs) can be tuned by doping the active layer with fluorescent polymers, dyes or macromolecules. We built white light emitting OLEDs with an external electroluminescence (EL) quantum efficiency of up to 1.8% by doping a blue-light-emitting laddertype poly(paraphenylene) with an orange emitting fully π-conjugated macro-molecule. For the EL spectra we found a much stronger contribution from the guest emission than in photoluminescence, which is attributed to charge carrier trapping at the guest and subsequent EL in addition to excitation energy migration of singlet excitons from the host to the guest.
Holographic Encoding of Permanent Gratings Embedded in Diamond by Two Beam Interference of a Single Femtosecond Near-Infrared Laser Pulse
Authors: Kawamura Ken-ichi , Sarukura Nobuhiko , Hirano Masahiro , Hosono Hideo
Published: October 2002

It is reported on the first demonstration that non-erasable gratings may be holographically encoded in diamonds by colliding a pair of pulses split from a single high peak power femtosecond laser pulse using a Ti: sapphire laser. Confocal microscopic observation revealed that gratings are formed beneath the top surface at ∼0.5 to ∼1.5 µm. Conversion of diamond into diamond-like or amorphous carbon occurs in the encoded portion, resulting in the refractive index modulation. The present method is applicable for encoding volume holograms for all crystalline and amorphous transparent dielectrics including sapphire, LiNbO3, SiC, ZnSe and various types of glass.
Flat and Large Poly-Si Grains by a Continuous Process of Plasma-Enhanced Chemical Vapor Deposition of a-Si and Its Direct Laser Crystallization
Authors: Mimura Akio , Shinagawa Youmei , Kawachi Genshirou , Onisawa Kenichi , Minemura Tetsurou , Hara Masayuki , Ishida Takeshige , Takeda Tomohiko
Published: October 2002

A multichamber processor was developed for a 150 mm×150 mm-sized substrate which combines chemical vapor deposition (CVD) reactors and a laser annealer. Deposition of a-Si was carried out at 430°C using a new high-temperature heater and the hydrogen content was reduced to 6 at%. The continuous process of a-Si deposition and one-step direct laser crystallization provides a simple poly-Si preparation process which yields flat poly-Si grains (<R
rms: 4 nm). It was also found that dehydrogenation treatment increased film roughness.
Autocorrelation Measurement of Femtosecond Optical Pulses Based on Two-Photon Photoemission in a Photomultiplier Tube
Authors: Toshiaki Hattori Toshiaki Hattori , Yoshitsugu Kawashima Yoshitsugu Kawashima , Masahiro Daikoku Masahiro Daikoku , Hideyuki Inouye Hideyuki Inouye , Hiroki Nakatsuka Hiroki Nakatsuka
Published: October 2002

The very sensitive intensity autocorrelation measurement of 15 fs, 800 nm pulses from a Ti:sapphire laser has been achieved using two-photon-induced photocurrent in a photomultiplier tube.
Correlation between Photoluminescence Intensity and Micro Structure in Amorphous Silicon Films Prepared by Reactive RF Sputtering
Authors: Ikurou Umezu Ikurou Umezu , Takatoshi Murota Takatoshi Murota , Masayuki Kawata Masayuki Kawata , Yoshiaki Takashima Yoshiaki Takashima , Ken-ichi Yoshida Ken-ichi Yoshida , Mitsuru Inada Mitsuru Inada , Akira Sugimura Akira Sugimura
Published: October 2002

We report on the efficient photoluminescence (PL) of a-Si:H film prepared by reactive RF sputtering. The PL intensity and optical properties of the sputtered film depend on the input RF power. Stronger PL intensity at room temperature was observed for films deposited at low input RF power. The PL intensity of this film is stronger than that prepared by the plasma-enhanced chemical vapor deposition. The PL intensity did not correlate with the defect density but correlated with the number of SiH2 units in the film. A considerable number of SiH2 units in the film reduced transitions of electrons and/or holes to nonradiative centers.
A 1.3-µm GaInNAs/GaAs Single-Quantum-Well Laser Diode with a High Characteristic Temperature over 200 K
Authors: Kitatani Takeshi , Nakahara Kouji , Kondow Masahiko , Uomi Kazuhisa , Tanaka Toshiaki
Published: October 2002

We have obtained a high characteristic temperature (T
0) of 215 K
from a 1.3 µm GaInNAs/GaAs single-quantum-well laser under pulsed
operation at 20°C to 80°C. To our knowledge, this T
0 is the highest
yet reported for 1.3 µm band edge emitters suitable for
optical-fiber communication systems. The use of GaInNAs as an active
layer is, therefore, very promising for the fabrication of
long-wavelength laser diodes with excellent high-temperature performance.
Preparation of PbTiO3 Thin Films Using a Coating Photolysis Process with ArF Excimer Laser
Authors: Tsuchiya Tetsuo , Watanabe Akio , Imai Yoji , Niino Hiroyuki , Yamaguchi Iwao , Manabe Takaaki , Kumagai Toshiya , Mizuta Susumu
Published: October 2002

TiO2, PbO and PbTiO3 thin films were prepared using the Titanium-2-ethylhexanolate and lead-2-ethylhexanoate coating photolysis process with ArF excimer laser irradiation. The photolysis of Ti-2-ethylhexanolate, Pb-2-ethylhexanoate and mixed Ti-2-ethylhexanolate and Pb-2-ethylhexanoate was investigated by Fourier transform infrared (FT-IR) absorption spectroscopy and X-ray diffraction (XRD). In the case of the one-step ArF irradiation method at 50 mJ/cm2 with a repetition rate of 10 Hz for 5 min, rutile TiO2 and PbTiO3 perovskite phase along with a pyrochlore phase were obtained, while PbO was not obtained. On the other hand, in the case of the two-step ArF irradiation method consisting of preliminary weak irradiation at 10 mJ/cm2 with a repetition rate of 50 Hz for 0.5 min and a stronger irradiation at 50 mJ/cm2 with a repetition rate of 10 Hz for 5 min, anatase TiO2, β-PbO and a single phase of perovskite PbTiO3 were successfully obtained. The crystallization mechanism of PbTiO3 films from the metallorganic precursor is also discussed.
Control of In-Plane Orientation of Merocyanine Dye in Mixed Langmuir-Blodgett Films Using Salt Formation with Matrix
Authors: Tachibana Hiroaki , Matsumoto Mutsuyoshi
Published: October 2002

An amphiphilic merocyanine dye (MC) having a carboxyl group was mixed with arachidic acid (C20) or octadecylamine (C18NH2). In the MC/C20 mixed Langmuir-Blodgett (LB) film (mixing ratio of 1:1), MC formed J-aggregates and irregularly-shaped domains were observed. The carboxyl groups of MC and C20 remained intact. On the other hand, in the MC/C18NH2 mixed LB films (mixing ratio of 1:1), MC was in the monomeric or dimeric states, and the surface of the film was very smooth. MC was deprotonated and C18NH2 was protonated, which strongly suggests the salt formation of the two components.
Structural Investigation of Metalorganic Chemical-Vapor-Deposition-Grown InGaAs Layers on Misoriented GaAs Substrates
Authors: Takano Yasushi , Masuda Masako , Shirakawa Yasufumi , Kuwahara Kazuhiro , Fuke Shunro
Published: October 2002

InGaAs layers were grown by metalorganic chemical vapor deposition (MOCVD) using linearly graded buffer layers on exactly oriented and misoriented GaAs(001) substrates toward [100]. The material quality was determined by optical microscopy, X-ray diffraction, atomic force microscopy and transmission electron microscopy investigation. A smooth surface was difficult to obtain on exactly oriented substrates. Layers on misoriented substrates showed smoother surface morphology and reduced linewidth of X-ray rocking curves than those on exactly oriented substrates. The radius of curvature of the sample for the tilted substrate was larger than that for the untilted substrate. These findings suggest that the introduction of dislocations is enhanced and the misfit dislocation distribution in the graded buffer layers becomes uniform with the use of the misoriented substrates.
Phenomenological Theory of Semiconductor Epitaxial Growth with Misfit-Dislocations
Authors: Ko Okajima Ko Okajima , Kyozaburo Takeda Kyozaburo Takeda , Norihisa Oyama Norihisa Oyama , Eiji Ohta Eiji Ohta , Kenji Shiraishi Kenji Shiraishi , Takahisa Ohno Takahisa Ohno
Published: October 2002

We have developed a phenomenological theory of growth behavior in semiconductor heteroepitaxy that includes the effects of the formation of Stranski-Krastanov (SK) islands and misfit-dislocations (MDs). Our theory can reproduce the various types of growth behavior observed in heteroepitaxial growth. Moreover, we also formulate a procedure for determining the phenomenological parameters that includes atomistic calculations. The critical thickness of InAs/GaAs(110) obtained by this procedure is in good agreement with the experimentally obtained value.
Interaction between Two Ferrocene Groups Linked by Methoxyterthienyl “Molecular Wire”
Authors: Sato Masa-aki , Fukui Kazuhiko , Kashiwagi Shin-ichiro , Hiroi Masao
Published: October 2002

Methoxyterthiophene substituted with two terminal ferrocenyl groups was prepared. The oxidation process and the oxidized state of the compound were investigated by cyclic voltammetry, coulometry, and electronic absorption spectroscopy. The measurements show that an oxidized species is first produced on a ferrocene moiety and definitely interacts not only with the methoxythiophene moiety but also with the other ferrocene moiety. This indicates that the oxidized species spread over almost the entire molecule.
Simulation of High-Pressure Oxidation of Silicon Based on the Interfacial Silicon Emission Model
Authors: Uematsu Masashi , Kageshima Hiroyuki , Shiraishi Kenji
Published: October 2002

Silicon oxidation using high-pressure oxygen, where the rate shows less-than-linear dependence, is simulated based on the interfacial silicon emission model. The oxidation reaction of the emitted Si atoms in the oxide, which controls the oxidation rate at the interface, plays an important role in determining the oxidation pressure dependence. We introduce reaction terms for the oxidation in the oxide so as to fit the oxide thickness at oxygen pressures of 1–20 atm. The simulation is made using constant parameter values for oxidation reaction by changing only the oxidant solubility in the oxide in proportion to oxygen pressure.
Local Stress Analysis of Epitaxial Laterally-Overgrown GaN
Authors: Quincy Liu Quincy Liu , Axel Hoffmann Axel Hoffmann , Axel Kaschner Axel Kaschner , Christian Thomsen Christian Thomsen , Jürgen Christen Jürgen Christen , Peter Veit Peter Veit , Rainer Clos Rainer Clos
Published: October 2002

Three-dimensional stress distributions for two different samples of epitaxial laterally-overgrown GaN deposited on SiO2 masks were simulated by continuum elasticity theory using the finite-element method. The samples have patterned masks in the (1100) and (1120) orientations, respectively. The results of the simulation compared quantitatively quite well with the stress distributions derived from micro-Raman measurements. This success depended on taking into account the existence of a string of voids in the samples that could be seen in the transmission electron microscope image. From the buffer layer towards the sample surface, the biaxial stress relaxes within a relatively short distance to a value that corresponds to a biaxially compressed film. This value persists until a short distance from the sample surface.
Effect of Hydrogen Plasma Treatment on Formation of Amorphous Silicon Film Using Organosoluble Silicon Cluster as a Precursor
Authors: Watanabe Akira , Unno Masashi , Hojo Fusao , Miwa Takao
Published: October 2002

A novel process for the formation of amorphous silicon thin film by a coating technique using an organosoluble silicon cluster as a precursor was developed. The process of conversion of organic silicon film to inorganic silicon film was investigated by Raman and Fourier transform infrared (FT-IR) spectroscopies. Upon heat treatment of the precursor film, the disappearance of the organic substituent and the appearance of the transverse optical phonon band of amorphous silicon were observed in Raman spectra. The combination of heat and hydrogen plasma treatments of the thin film reduced the conversion temperature dramatically.