bluuebunny/crossref_metadata_2025 huggingface dataset:
Lens Shift Correction in Tracking Servo System for Digital Versatile Rewritable Disc
Authors: Shihara Tetsuya , Watanabe Katsuya , Kadowaki Shin'ichi , Ishibashi Hiromichi
Published: October 2002

In this paper the development of tracking offset correction for
playback of a digital versatile rewritable disc (so called DVD-RAM),
is described. The slim drive, having a small optical pick-up head
with a small objective lens, is easily influenced by the deviation
of the push-pull tracking error signal due to lens shift. The
DVD-RAM disk format provides information not only on the amount of
lens shift using the push-pull tracking error signal of address
marks to correct tracking deviation, but also an opportunity to
determine the optimum initial lens position using the differential
phase tracking error signal.
Improvement of Performance of a Tracking Servo System for an Optical Disk Drive
Authors: Arai Kiyotaka , Okumura Hideyo , Tokumaru Haruki , Ohishi Kiyoshi
Published: October 2002

A tracking servo system for high-speed and precise tracking control is proposed.
An optical disk camera-recorder to record and retrieve high-definition television
signals is being developed. The camera-recorder must have both a high data
transfer rate and a large capacity. These requirements will be fulfilled by
narrowing the track pitch on the disk and by increasing the disk rotation speed.
Generally, optical disks have a radial run-out of up to approximately 100 µm
peak-to-peak. The tracking servo system must have precise control for the narrow
track pitch and high-speed control for the high disk rotation speed. To meet these
requirements, we propose a tracking servo system consisting of a feedback
controller and of a feedforward controller which employs a pre-compensator
applying the zero phase error tracking method. The simulation results show
reduction of the residual tracking error and also an increase in the disk
rotation speed.
Tilt Servo Using Modal Wavefront Actuator
Authors: Lee Hsiao-Wen , Wei Li-ding , Jou Jwo-Ming
Published: October 2002

In this paper, a new approach of disk tilt servo by using piezoelectric modal wavefront actuator is
proposed. A compatible configuration of commerical optical pickup head (PUH) is presented with a
piezoelectric folding mirror. Based on this device, the innovation has the advantages of high
bandwidth, linear control, simple drive line and high spatial wavefront resolution.
Pupil Plane Filtering for Optical Pickup Heads with Effective Numerical Aperture of 1.1 and 2.0
Authors: Shimura Kei , Milster Tom D. , Jo Joshua S. , Hirota Kusato
Published: October 2002

A pupil plane filtering technique is applied to data signal
detection in an optical data storage system that uses a solid
immersion lens (SIL) and a quadrilayer phase change recording
medium. Two systems that have the effective numerical aperture
(NAEFF) of 1.1 and 2.0 are investigated. A new
filter is designed for the NAEFF=2.0 system on the
basis of this study. We have confirmed by numerical calculations
that the technique improves signal contrast, which is defined by
the ratio of the difference signal to the sum signal between the
homogeneous crystalline area and the homogeneous amorphous area.
We have also confirmed that the technique makes the contrast less
sensitive to the gap width between the SIL and the recording
medium. The vectorial feature of the light is considered in the
calculations. The calculated irradiance distributions and signal
levels for the system with NAEFF =1.1 are confirmed
by experiments.
Superresolution Using a Vertical-Cavity Surface-Emitting Laser (VCSEL) with a High-Order Laguerre-Gaussian Mode
Authors: Flynn Richard A. , Kibar Osman , Hartmann Daniel , Esener Sadik
Published: October 2002

A vertical-cavity surface-emitting laser (VCSEL) is current-annealed to operate
in the high order (0, 4) Laguerre mode, and this source is used in a superresolution setup
to achieve a spot size smaller than the classical diffraction limit. Theory predicts a
reduction down to 51% of the classical limit in each dimension
(i.e. 4× reduction in
area), and a reduction down to 65% (i.e. 2.5× reduction in area) is experimentally
demonstrated with a signal-to-noise ratio of >10 dB between the
main-lobe and the side-lobe intensities.
Near-Field Phase-Change Optical Recording of 1.36 Numerical Aperture
Authors: Ichimura Isao , Kishima Koichiro , Osato Kiyoshi , Yamamoto Kenji , Kuroda Yuji , Saito Kimihiro
Published: October 2002

A bit density of 125 nm was demonstrated through near-field phase-change (PC)
optical recording at the wavelength of 657 nm by using a supersphere solid immersion lens
(SIL). The lens unit consists of a standard objective and a φ2.5 mm SIL. Since this lens
size still prevents the unit from being mounted on an air-bearing slider, we developed a
one-axis positioning actuator and an active capacitance servo for precise gap control to
thoroughly investigate near-field recording. An electrode was fabricated on the bottom of
the SIL, and a capacitor was formed facing a disk material. This setup realized a stable air
gap below 50 nm, and a new method of simulating modulation transfer function (MTF)
optimized the PC disk structure at this gap height. Obtained jitter of 8.8% and a clear eye-pattern prove that our system successfully attained the designed numerical-aperture (NA) of 1.36.
Challenge to Several-Tens-nm/Bit Recording Using Domain Wall Displacement Detection Medium
Authors: Shunji Yoshimura Shunji Yoshimura , Atsushi Fukumoto Atsushi Fukumoto
Published: October 2002

We have examined two unique data error causes for domain wall displacement
detection (DWDD) media, dropout and bit shift, using 8–9 modulation and
(1, 7)-RLL modulation. We have determined that dropout depends only on the
mark length of recorded data, while the deviation of edge shifts, which
causes bit shifts, maintains approximately the same value regardless of mark
length. Using these characteristics of error causes, we have also shown a
prospect of achieving several-tens-nm/bit recordings.
Room Temperature 1.6 µm Electroluminescence from a Si-Based Light Emitting Diode with β-FeSi2 Active Region
Authors: Takashi Suemasu Takashi Suemasu , Yoichiro Negishi Yoichiro Negishi , Ken'ichiro Takakura Ken'ichiro Takakura , Fumio Hasegawa Fumio Hasegawa
Published: October 2002

Room temperature electroluminescence (EL) was obtained for the first time from a Si-based light emitting diode with semiconducting silicide (β-FeSi2) active region. The peak wavelength was 1.6 µm and it is from β-FeSi2 balls embedded in a Si p-n junction. An a-axis oriented β-FeSi2 layer was grown on n+-(001) Si by reaction deposition epitaxy (RDE), then p- and p+-Si layers were grown by molecular beam epitaxy (MBE). The β-FeSi2 aggregated into balls with about 100 nm diameter in this process. The EL intensity increased superlinearly with increase of the injected current density, and reasonable EL was obtained at current density above 10 A/cm2, though the photoluminescence (PL) was difficult to be detected at room temperature.
High-Temperature Breakdown Characteristics of δ-Doped In0.49Ga0.51P/GaAs/In0.25Ga0.75As/AlGaAs High Electron Mobility Transistor
Authors: Lee Ching-Sung , Hsu Wei-Chou , Chen Yen-Wei , Chen Yung-Cha , Shieh Hir-Ming
Published: October 2002

A δ-doped In0.49Ga0.51P/GaAs/In0.25Ga0.75As/AlGaAs high electron mobility transistor exhibiting high breakdown voltage at high temperature and excellent pinch-off properties has been successfully fabricated by low-pressure metalorganic chemical vapor deposition (LP-MOCVD). The gate-to-drain breakdown voltages are as high as 62 V (300 K) and 42 V (500 K) contributed by δ-doping the high band-gap In0.49Ga0.51P insulator layer. An improved gate voltage swing of about 2.3 V is also achieved. Furthermore, the device demonstrated excellent pinch-off properties when a carrier-retarding AlGaAs buffer layer was inserted. The above results indicate that the present structure is promising for high power and high temperature ambient device applications.
Low Threshold Current Density Operation of GaInAsP/InP Lasers with Strain-Compensated Multiple-Layered Wirelike Active Regions
Authors: Nobuhiro Nunoya Nobuhiro Nunoya , Hideo Yasumoto Hideo Yasumoto , Hideki Midorikawa Hideki Midorikawa , Shigeo Tamura Shigeo Tamura , Shigehisa Arai Shigehisa Arai
Published: October 2002

In order to suppress the occurrence of nonradiative recombination traps during an etching and regrowth process, whose origin was considered to be large latticemismatch, a partially strain-compensated five-quantum-well structure was used for 1.5 µm GaInAsP/InP lasers with wirelike active regions (wire widths of 43 nm and 70 nm) fabricated by electron beam lithography, CH4/H2 reactive-ion etching and organo-metallic vapor-phase-epitaxial regrowth. As a result, we realized wirelike lasers with wire widths of 43 nm with a threshold current lower than those of quantum film lasers prepared on the same wafer at temperatures up to 85°C, for the first time.
High-Power Nd:Y3Al5O12 Ceramic Laser
Authors: Jianren Lu Jianren Lu , Jie Song Jie Song , Mahendra Prabhu Mahendra Prabhu , Jianqiu Xu Jianqiu Xu , Ken-ichi Ueda Ken-ichi Ueda , Hideki Yagi Hideki Yagi , Takakimi Yanagitani Takakimi Yanagitani , Alexis Kudryashov Alexis Kudryashov
Published: October 2002

High power CW (continuous wave) polycrystalline Nd:Y3Al5O12 (Nd:YAG) ceramic rod laser was demonstrated for the first time. The maximum output power of 31 W with a 18.8% slope efficiency was obtained at 1064 nm using 214.5 W/808 nm laser diode pumping.
Characterization of Oxide Films on SiC by Spectroscopic Ellipsometry
Authors: Takeshi Iida Takeshi Iida , Yuichi Tomioka Yuichi Tomioka , Yasuto Hijikata Yasuto Hijikata , Hiroyuki Yaguchi Hiroyuki Yaguchi , Masahito Yoshikawa Masahito Yoshikawa , Yuuki Ishida Yuuki Ishida , Hajime Okumura Hajime Okumura , Sadafumi Yoshida Sadafumi Yoshida
Published: October 2002

We have, for the first time, evaluated the optical constants of thermally oxidized films on SiC by spectroscopic ellipsometry, and discussed the characteristics of SiC/SiO2 interfaces. It was found that the effective refractive indices are smaller than those of the oxide films on Si. They increase with oxidation time, or oxide thickness, reaching to the values of Si oxides. The refractive indices also depend on the oxidation methods, and the pyrogenic oxidation brings about larger refractive indices than dry oxidation. The origin of the small refractive indices of oxide films on SiC was discussed in terms of interface structures and composition in comparison with those of oxide films on Si.
Hybrid Crystals of Calcium Carbonate and Amino Acids
Authors: Kai Ayako , Miki Toshikatsu
Published: October 2002

We have investigated the effects of amino acids on the crystallization of calcium carbonate (CaCO3), and the reactivity between amino acids and CaCO3. Noncharged-polar and acidic amino acids are highly incorporated into CaCO3 and stabilize cauliflower-like grains composed of vaterite which is thermodynamically unstable in the CaCO3 polymorphs. Amino acids in the hybrid CaCO3 form radicals different from those in crystalline amino acids by X-ray irradiation. The results imply that the hybrid carbonate can provide a reaction field for organic synthesis. We also propose models for the bond between amino acids and CaCO3 using semiempirical approximation procedures.
New Technique for the Thermal Resistance Measurement of Power Field Effect Transistors Using Cathodoluminescence
Authors: Hwa-Mok Kim Hwa-Mok Kim , Jin-Sik Yoon Jin-Sik Yoon , Seung-Ho Lee Seung-Ho Lee , Jae-Eung Oh Jae-Eung Oh , Won-Sang Lee Won-Sang Lee , Kye-Ik Chun Kye-Ik Chun , Ki-Woong Chung Ki-Woong Chung , Hae-Won Chung Hae-Won Chung , Tae-Won Kang Tae-Won Kang
Published: October 2002

A new approach for measuring the thermal resistance of power field-effect transistors (FETs) with extremely high spatial resolution below 40 nm has been demonstrated using cathodoluminescence generated by a low-energy electron beam. The energy shift of the fundamental bandgap caused by the current heating in the channel region is spatially probed, and is converted to the channel temperature using the temperature dependence of the material bandgap. The obtained thermal resistances of the GaAs metal semiconductor field effect transistor (MESFET) and the GaN MESFET are compared with those measured by the conventional electrical technique.
Volume Holographic Storage in Near-Stoichiometric LiNbO3:Ce,Mn
Authors: Gyoo Kim In , Myeongkyu Lee Myeongkyu Lee , Shunji Takekawa Shunji Takekawa , Yasunori Furukawa Yasunori Furukawa , Kenji Kitamura Kenji Kitamura , Ludwig Galambos Ludwig Galambos , Lambertus Hesselink Lambertus Hesselink
Published: October 2002

Near-stoichiometric LiNbO3:Ce,Mn exhibited a reversible photochromic effect at room temperature. Irradiation with ultraviolet (UV) light enhanced a visible absorption band, and the photorefractive sensitivity to 532 nm-green recording light was greatly improved after UV irradiation. Hologram multiplexing was performed with a continuous-wave 532 nm-green laser by the angle-multiplexing method without and with UV pre-exposure. An M/# of ∼5 was obtained in a crystal of 2.55 mm-thickness in the absence of UV pre-exposure. In multiplexing after UV pre-exposure, however, the variable sensitivity and erasure-time constant made it very difficult to achieve a multiple hologram storage with nearly equivalent diffraction efficiency.
Electrical Fatigues in Oxygen Plasma-Treated Sol-Gel-Derived Lead-Zirconate-Titanate Films
Authors: Kyoo Jang Hyuk , Eui Lee Cheol , Jeong Noh Seung
Published: October 2002

Effects of O2-plasma on the electrical fatigue characteristics in ferroelectric [Pb(Zr
x
, Ti1-x
)O3] (PZT) films prepared by a sol-gel method were investigated. Before and after oxygen plasma treatment, the switched remanent polarization decreased to 59% and 76% of the initial value, respectively, when electrical stress was applied by 108 switching cycles. Thus, oxygen plasma treatment is shown to be a simple and effective method of reducing electrical fatigues in PZT thin films.
The Integration of InxGa1-xN Multiple-Quantum-Well Laser Diodes with Copper Substrates by Laser Lift-Off
Authors: Wong William S. , Kneissl Michael , Mei Ping , Treat David W. , Teepe Mark , Johnson Noble M.
Published: October 2002

Indium-gallium nitride (InGaN) multiple-quantum-well ridge-waveguide laser diodes (LDs) grown by metalorganic chemical vapor deposition on sapphire substrates were successfully transferred onto Cu substrates using a laser lift-off (LLO) process. Characterization of the InGaN LDs before and after the sapphire substrate removal revealed no measurable degradation in device performance. The threshold current, under pulsed operation, for a 3 µm ridge-waveguide device and the laser-emission spectrum remained essentially unchanged after the LLO process. In addition, the conductive Cu substrate permitted realization of LDs with vertical-current injection using the Cu as the backside contact.
Optical Quality Dependence on Growth Rate for Metalorganic Chemical Vapor Deposition Grown GaInNAs/GaAs
Authors: Kawaguchi Masao , Miyamoto Tomoyuki , Gouardes Eric , Schlenker Dietmar , Kondo Takashi , Koyama Fumio , Iga Kenichi
Published: October 2002

GaInNAs/GaAs quantum wells with indium compositions of up to 39% were grown by metalorganic chemical vapor deposition under different growth rates. We found that the growth rate (∼1 µm/h) critically affects the optical quality of GaInNAs/GaAs quantum wells and that a low growth rate (∼0.2 µm/h) is preferable for increasing nitrogen compositions.
Fabrication of Self-Aligned Surface Tunnel Transistors with a 80-nm Gate Length
Authors: Chun Yong Jin , Uemura Tetsuya , Baba Toshio
Published: October 2002

A novel method using electron-beam (EB) lithography and regrowth for fabricating self-aligned InGaAs-based surface tunnel transistors (STTs) with sub-micron gate lengths has been developed. The shape of regrowth layer on the gate region is significantly affected not only by the gate lengths but also by the thickness of the regrowth layer. During regrowth, (111) facets are formed at the edges of the gate region while the (100) surface is maintained at the center. The shape changes to triangular consisting of (111) facets as gate length decreases below 150 nm due to the slow growth rate of the (111) facets compared to the (100) surface. The 80-nm STTs were fabricated by controlling the shape of the regrowth layer, and no deposition of the regrowth layer on the sidewall, which causes leakage current, occurred. The successful operation of InGaAs-based 80-nm STTs with clear negative differential resistance (NDR) characteristics and a gate-controlled peak current was obtained at room temperature.
Higher Resistivities Obtained by Iron-Diffusion into Undoped Semi-Insulating GaAs
Authors: Ohsawa Jun , Ozaki Yasutaka , Misaki Takashi
Published: October 2002

A simple diffusion process at low temperatures of
500–550°C can increase the resistivity of GaAs by one order of
magnitude; deep acceptors of iron on the order of 1014 cm-3
were introduced into liquid encapsulated Czochralski(LEC)-grown GaAs
wafers from a spin-on source to obtain higher resistivity in the range
of 108 Ω·cm. Control of the Fermi level onto the middle of
the energy gap was accomplished by compensating deep donors of
electron level No. 2 (EL2) by the acceptors located at
E
t-E
v=0.46 eV. A calculation based on
carrier-compensation concurs with the trend in the resistivity
variation experimentally obtained by iron-diffusion in the temperature
range of 450–600°C.
Experimental Test of a Three-Dimensional Model for Electrophysical Properties of Metal Films
Authors: Chornous Anatoly M. , Opanasyuk Nadia M. , Pogrebnjak Alexander D. , Protsenko Ivan Yu.
Published: October 2002

A three-dimensional model of strain sensitivity proposed by [Tellier, Tosser: Thin Solid Films 59 (1979) 163; Tosser, Tellier and Pichard: J. Mater. Sci. 16 (1981) 944] has been tested for thin Cr, Cu and Co films. The films were obtained by electron-beam evaporation in a vacuum of 10-4–10-5 Pa. Film structure stabilization was carried out by heating and cooling at the rate of 3 K/min in the range of 300 to 520 K. The identity of properties of the films obtained on the glass (during the termal coefficient of resistance (TCR) measuring) and the textolite glass (during the strain-sensitivity coefficient (SSC) measuring) substrates was examined according to Vand method on lattice distortion energy spectra for films of different thickness, where the spectra were calculated from the resistance-temperature data. It has been shown that the experimental results of the strain sensitivity agree with the calculated ones only under the assumption of size dependence of the electron mean-free path.
Effect on GaN/Al0.17Ga0.83N and Al0.05Ga0.95N/Al0.17Ga0.83N Quantum Wells by Isoelectronic In-Doping during Metalorganic Vapor Phase Epitaxy
Authors: Michihiko Kariya Michihiko Kariya , Shugo Nitta Shugo Nitta , Masayoshi Kosaki Masayoshi Kosaki , Yohei Yukawa Yohei Yukawa , Shigeo Yamaguchi Shigeo Yamaguchi , Hiroshi Amano Hiroshi Amano , Isamu Akasaki Isamu Akasaki
Published: October 2002

The effects of isoelectronic In-doping on the structural and optical properties of GaN/Al0.17Ga0.83N and Al0.05Ga0.95N/Al0.17Ga0.83N quantum wells (QWs) on GaN were investigated. QWs were grown by atmospheric pressure metalorganic vapor phase epitaxy with either H2 or N2 carrier gas. Without In-doping, QWs grown in N2 carrier gas had highly superior crystalline and optical properties than those grown in H2 carrier gas. X-ray diffraction and photoluminescence studies revealed that In-doping improves the crystalline and optical properties of QWs, irrespective of the carrier gas species used during growth. These improvements are more remarkable for In-doping into the well layers rather than into the barrier layers.
Zinc-Blende-Type Cubic GaN Single Crystals Prepared in a Potassium Flux
Authors: Yamane Hisanori , Kajiwara Takashi , Sekiguchi Takashi , Shimada Masahiko
Published: October 2002

Single crystals of zinc-blende-type cubic GaN (c-GaN, space
group F43m, lattice parameter a=4.5062(9) Å) were
synthesized at
750°C by the reaction of Ga and N2 in a potassium flux. The
crystal
structure was analyzed by single-crystal X-ray diffraction with an R1-factor of 2.1%
(R1=Σ∥F
o-F
c∥/Σ|F
o|), where
F
o is the observed structure factor and F
c is
the calculated structure factor). A peak of near-band-edge emission was
observed at 3.20 eV in the cathodoluminescence
spectrum measured at 25°C.
Investigation of Substrate Orientation Dependence for the Growth of GaN on GaAs (111)A and (111)B Surfaces by Metalorganic Hydrogen Chloride Vapor-Phase Epitaxy
Authors: Yoshinao Kumagai Yoshinao Kumagai , Akinori Koukitu Akinori Koukitu , Hisashi Seki Hisashi Seki
Published: October 2002

It was found that a 50-nm-thick GaN buffer layer grown by metalorganic hydrogen chloride vapor-phase epitaxy (MOHVPE) at 550°C on a GaAs (111)A surface did not deteriorate even after subsequent heating in an NH3 ambient up to 1000°C, whereas numerous pinholes were formed when the buffer layer was grown on a GaAs (111)B surface. In addition, serious arsenic (As) desorption from the GaAs substrate occurred through the pinholes. A single crystal hexagonal GaN layer with a mirror-like surface can be grown at 1000°C on the 50-nm-thick GaN buffer layer grown at 550°C on the GaAs (111)A surface, as confirmed by scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses. The full-width at half maximum (FWHM) of the ω mode scan for the GaN (0002) plane was 1450 arcsec. Photoluminescence (PL) measurement showed a sharp band-edge emission at 363.1 nm with a FWHM of 96 meV at room temperature.
Characterization of the Surface Recombination Velocity of HgCdTe Using a Gate-Controlled Diode
Authors: Chul Lee Jong-Hwa Choi
Published: October 2002

A four-terminal gate-controlled diode structure has been
used to characterize the surface recombination velocity of HgCdTe.
The electrical performance of the gate-controlled diode fabricated
using x=0.3 HgCdTe was characterized by capacitance-gate voltage
and current-gate voltage measurements. A theoretical model was
developed for the total dark current in the gate-controlled diode
structure and used to fit the experimental data. Data fitting when
the experimental device was operated in depletion mode allowed the
simultaneous extraction of the surface recombination velocity, 170 cm/s, the generation lifetime in the n-p junction depletion
region, 12 ns, and the generation lifetime in the gate induced
junction depletion region, 500 ns.
Improvement of Reverse Leakage Current by Fluorine Implantation in n+/p Shallow Junctions Diffused from a Cobalt Silicide Layer
Authors: Park Ji-Soo , Sohn Dong Kyun , Bae Jong-Uk , Oh Jong Hyuk , Han Chang Hee , Park Jin Won
Published: October 2002

The effect of fluorine implantation on reverse leakage current
has been investigated in n+/p junctions formed by diffusion from a
cobalt silicide layer. Fluorine (F) implantation at a moderate dose
and energy improves the junction leakage, but high dose fluorine
implantation, above 1×1015 cm-2, degrades junction
leakage. Considering that F implantation does not affect the thermal
stability of the CoSi2 layer and arsenic concentration
profiles, it is conjectured that the highly electronegative and
reactive F ions cause deactivation of silicon lattice defects that
act as generation centers, thereby reducing leakage. However, F ions
in excess may act as defects themselves in silicon rather than
reducing the silicon lattice defects, which increases the leakage current.
Electrical Characterization of Extremely Thin (2.7 nm) Oxynitride and Oxide of Silicon Grown by N2O Plasma and Wet Oxidation at Low Temperatures: A Comparison
Authors: Bhat Vishwanath Krishna , Bhat Kunchinadka Narayana , Subrahmanyam Aryasomayajula
Published: October 2002

Extremely thin (2.7 nm) oxynitride and oxide of silicon are grown by N2O plasma and wet oxidation at low temperatures. These extremely thin dielectrics
are characterized by fabricating metal oxide semiconductor (MOS) tunnel
diodes, and studying their capacitance–voltage (C–V), and conductance–voltage (G–V)
characteristics. The density of interface states (D
it) for the as grown plasma
oxynitride is high (2.1×1012 cm-2·eV-1) compared to that of wet oxide
(3.8×1011 cm-2·eV-1), the density of fixed oxide charges (Q
f) are comparable
(∼5×1012 cm-2) in both the cases. It is shown that, post oxidation annealing
(350°C) of the plasma oxynitride improves the quality of the
Si/oxynitride interface.
Inclined Homeotropic Alignment Control of Liquid Crystals on Photo-Cross-Linked Polymer Film by Slantwise Nonpolarized Ultraviolet Light Irradiation
Authors: Kawatsuki Nobuhiro , Takatsuka Hirofumi , Yamamoto Tohei
Published: October 2002

The photoalignment of liquid crystals (LC) on a photo-cross-linkable polymer
film was realized by the use of slantwise nonpolarized ultraviolet (NP-UV) light
irradiation. The LC aligned homeotropically with an inclination, and the inclined
direction was opposite to that of the incident NP-UV light propagation. By changing the
irradiation angle and time, the inclination of the LC could be controlled. The alignment
mechanism of the LC can be explained by the interaction between the LC and the
photo-cross-linked group of the polymer film.
Effects of Nitride Lightly-Doped-Drain Spacers on Inter-Metal-Dielectrics-Induced Metal Oxide Semiconductor Field Effect Transistor Degradation under Hot Carrier Stress
Authors: Lin Jengping , Liu Willie , Lin Chi-Hui
Published: October 2002

Metal oxide semiconductor field effect transistors (MOSFETs)
fabricated using various combinations of lightly-doped-drain (LDD)
spacer materials (e.g. Si3N4 versus SiO2)
and inter-metal-dielectric
(IMD) materials (e.g. silane versus tetraethoxysilane
plasma-enhanced chemical vapor deposition oxide) were used to
investigate the effect of IMD materials and nitride spacers on
MOSFET degradation under hot carrier stress. According to the
results, nitride spacers significantly enhance the hot-carrier
reliability of nMOSFETs; however, the water-blocking property of
nitride spacers fails to eliminate the IMD-induced device
degradation. For pMOSFETs, there is negligible difference in hot
carrier immunity between devices with oxide and nitride spacers.
Tunneling Spectra of Co/I/BiSrCaCuO Tunnel Junctions
Authors: Takayuki Ishibashi Takayuki Ishibashi , Kazushige Sato Kazushige Sato , Genda Gu Genda Gu , Naoki Koshizuka Naoki Koshizuka , Katsuaki Sato Katsuaki Sato
Published: October 2002

Ferromagnet/insulator/superconductor (F/I/S) tunnel junctions consisting of Co and Bi2Sr2CaCu2Ox (BSCCO) have been fabricated in order to study whether the superconducting properties are affected by the spin-polarized current. Co is a ferromagnetic metal with a spin polarization of approximately 35%, and BSCCO is a high-T

c
superconductor with critical temperature (T

c
) of 80–90 K. The junctions with 100 ×100 µm2 have been fabricated using photolithography on the cleaved BSCCO single crystal. As a reference, Au/I/BSCCO tunnel junctions have also been fabricated in the same manner. In both junctions, gap structures were clearly observed in d
I/ d
V spectra. However, the gap energy of 28 mV obtained at 30 K for the Co/I/BSCCO junction was smaller than that obtained for the Au/I/BSCCO junction. The zero-bias conductance peak (ZBCP) was observed clearly for the Au/I/BSCCO junction. It is considered that these differences between the Co/I/BSCCO and the Au/I/BSCCO junctions are due to the spin-polarized current flowing through the junctions.
Improvement of Brightness of Gd2O3:Eu Phosphor Particles Using Boric Acid Flux in the Spray Pyrolysis
Authors: Kang Yun Chan , Roh Hyun Sook , Park Seung Bin
Published: October 2002

Gd2O3:Eu phosphor particles of high brightness were directly prepared by
the spray pyrolysis from solution with boric acid flux. The particles
prepared from solutions with boric acid flux had higher photoluminescence (PL) intensities than
that of particles prepared from solution without flux. The particles
prepared from the solution of 10 wt% boric acid had the highest PL
intensity, which was higher by 43% than that of the particles prepared from
solution without flux. The roles of boric acid flux in improving PL
intensity of Gd2O3:Eu phosphor particles in the spray pyrolysis were to
promote crystal growth and to reduce surface defect of particles. They were
different from ones in solid state reaction.
Application of the pH–Imaging Sensor to Determining the Diffusion Coefficients of Ions in Electrolytic Solutions
Authors: Tatsuo Yoshinobu Tatsuo Yoshinobu , Tetsuro Harada Tetsuro Harada , Hiroshi Iwasaki Hiroshi Iwasaki
Published: October 2002

The pH–imaging sensor is applied to visualization of ionic diffusion in an electrochemical
system. Redistribution of the pH value due to diffusion of ions after electrolysis is measured
to determine the diffusion coefficients of anions and cations. Dependence of the diffusion
coefficient on the molecular weight of ions is investigated. Applicability of the pH–imaging
sensor to quantitative analysis of dynamics in a chemical system is demonstrated.
Activation Energy and Electrical Activity of Mg in Mg-Doped InxGa1-xN (x<0.2)
Authors: Kumakura Kazuhide , Makimoto Toshiki , Kobayashi Naoki
Published: October 2002

We investigated the electrical properties of Mg-doped InGaN with an In mole
fraction of less than 0.2 grown by metalorganic vapor phase epitaxy. We obtained p-type
InGaN with a hole concentration above 1018 cm-3 at room temperature. The
hole concentrations of Mg-doped In0.04Ga0.96N and In0.14Ga0.86N
were 1.2×1018 and 6.7×1018 cm-3, respectively, while that
of Mg-doped GaN was 3.0×1017 cm-3 with the same Mg doping
concentration. The activation energy of Mg in InGaN, calculated from the temperature
dependence of the hole concentration, decreases with the increase in the In mole
fraction. Furthermore, the electrical activity of Mg in InGaN increases with the In mole
fraction. As a result, higher hole concentrations were obtained at room temperature for
Mg-doped In
x
Ga1-x
N (x<0.2) with higher In mole fractions.
Novel Sidewall Capping for Degradation-Free Damascene Trenches of Low-Permittivity Methylsilsesquioxane
Authors: Yeh Ching-Fa , Lee Yueh-Chuan , Su Yuh-Ching , Wu Kwo-Hau , Lin Chein-Hsin
Published: October 2002

A low-permittivity organic dielectric, methylsilsesquioxane (MSQ), used as an
interlevel dielectric is expected to reduce the parasitic capacitance in integrated
circuit. However, MSQ film can be easily degraded during resist ashing after the film is
etched with the damascene trenches being created. In this work, a novel sidewall
capping technology is developed to solve the degradation issue. Prior to resist ashing,
a high-quality, low-permittivity oxide film is selectively deposited onto the sidewalls
of MSQ trenches using selective liquid-phase deposition. Experimental results
demonstrate that the capping oxide can effectively protect the sidewalls of MSQ
trenches from ashing-induced degradation.
Initial Oxidation of Si(100)2×1 by Ozone: Transition of Growth Kinetics from Adsorption to Ultrathin Film Growth
Authors: Nakamura Ken , Kurokawa Akira , Ichimura Shingo
Published: October 2002

We have investigated the initial oxide growth kinetics on Si(100)2×1 by
highly concentrated ozone (>80%) using X-ray photoelectron spectroscopy. Initial
oxidation of <0.6 nm was found to proceed in accordance with Langmuir kinetics.
However, a growth mode changed into linear kinetics at the oxide thickness of 0.6 nm
on the surface at >550°C, while no further growth of oxide films >0.6 nm
was observed on the surface at <500°C under the same pressure condition. This
clear transition of kinetics has contributed to the successful growth of an oxide film
>0.6 nm which is difficult to synthesize using molecular oxygen under the same
processing conditions.
Crucial Influence of the Azimuthal Alignment on the Dynamics of Pure Homeotropic Liquid Crystal Cells
Authors: Li-Yi Chen Li-Yi Chen , Shu-Hsia Chen Shu-Hsia Chen
Published: October 2002

We report an important effect of the azimuthal alignment error on the
dynamics of pure homeotropic liquid crystal cells. The flow of liquid crystal together with the azimuthal alignment error, causes the twist
structure of the directors in the rising period. Our simulation shows that even
a small azimuthal error of 0.02° still influences the transient
optical property of the cell. The simulation and experimental results are
described in this letter. We also describe the origin of the flow-induced
twist effect. This information is useful for the manufacture of the
fast homeotropic liquid crystal devices.
Current-Induced Step Bunching on Vicinal Si(111) Studied by Light Scattering
Authors: Tatsuo Yoshinobu Tatsuo Yoshinobu , Shinji Matsukawa Shinji Matsukawa , Koichi Sudoh Koichi Sudoh , Hiroshi Iwasaki Hiroshi Iwasaki
Published: October 2002

Step bunching on vicinal Si(111) surfaces induced by direct current heating has been studied
using an in situ light scattering measurement system. For annealing at 1240°C, the average
terrace width increased as a power of the annealing time with an exponent of 0.50±0.03 in
the range of 3–14 µm. During the step bunching process, the ratio of the standard deviation
of the terrace width to the average terrace width remained constant at 0.24. Light scattering
in the course of debunching was also observed.
Electrochromic Phosphate-Ion Sensor Based on Nickel-Oxide Thin-Film Electrode
Authors: Shimizu Youichi , Yamashita Tohru , Takase Satoko
Published: October 2002

An electrochromic phosphate-ion sensor was developed with a nickel-oxide
thin-film electrode. The nickel-oxide (NiO) thin-film electrode exhibited a remarkable
change of the transmittance at 530 nm, under a positive potential at +0.55 V vs
saturated calomel electrode (SCE), which was dependent on the HPO4
2-
concentration. The change of transmittance at 530 nm, the sensor signal, was almost
linear to the logarithm of the HPO4
2- concentration between
1.0×10-5 and 1.0×10-2 M. The 90% response time, when the
electrode potential was changed from +0.55 to 0 V vs SCE at
1.0×10-2 M, was about 40 s at room temperature.
High-Mobility Poly-Si Thin Film Transistors Fabricated on Stainless-Steel Foils by Low-Temperature Processes Using Sputter-Depositions
Authors: Serikawa Tadashi , Omata Fujio
Published: October 2002

High mobility n- and p-channel polycrystalline Si thin film transistors (poly-Si
TFTs) are successfully fabricated on flexible stainless-steel foils through low-temperature
processes (≦200°C). In the low-temperature process, all films in the
poly-Si TFT including active Si and gate SiO2 films are deposited by glow-discharge
sputtering and the Si films are crystallized by KrF excimer laser irradiation. Resulting
n- and p-channel poly-Si TFTs show excellent characteristics of mobility of 106 cm2/V·s
and 66 cm2/V·s, respectively. Moreover, they show low off-currents of 1×10-10 A
and on/off current ratios as high as 1×106. Thus, these poly-Si TFTs are very
promising for driver circuits and switching devices in novel flat panel displays of
lightweight and mechanically strong liquid crystal displays and light emitting displays.
Differences of the Magnetic Behavior and Microstructure between the Co Layers in the Ni Buffered Co/Cu/Co Sandwich and Their Effects on Giant Magnetoresistance
Authors: Li Tie , Shen Hong-Lie , Shen Qin-Wo , Tang Sheng-Ming , Zhu Xiang-Rong , Zou Shi-Chang
Published: October 2002

The magnetic behaviors and the microstructures of the two Co layers in the Ni
buffered Co 55 Å/Cu 35 Å/Co 55 Å sandwich were investigated by a vibrating sample
magnetometer and high resolution transmission electron microscope. It was found that
the structural quality of the two cobalt layers depends on their different `buffer' layers.
The lower cobalt layer induced by the nickel layer formed high quality face-centered
cubic (fcc) structure, while the upper cobalt layer grown upon the copper matrix
produced only random-oriented fcc-Co structure. The different crystalline states
between the two Co layers resulted in their different magnetic behaviors through the
magnetostatic effect, which made it possible to achieve a maximum anti-aligned state
and finally enhanced the giant magnetoresistance (GMR) effect in the Co/Cu/Co sandwich.
Low Voltage and Wide-Viewing-Angle Twisted Nematic Liquid Crystal Displays by Optical Compensation
Authors: Lu Minhua , Yang K. H.
Published: October 2002

Low voltage and wide-viewing-angle single-domain and two-domain twisted nematic liquid crystal displays (TN-LCDs)
can be achieved
by using a single-layer twist discotic film with negative birefringence as a compensation film.
The compensated TNs have also higher contrast ratio and less color-shifts over the
uncompensated ones. The compensated two-domain TN has the added advantage of no extra
light leakage at the locations of the disclination lines between two domains in the dark state of
the display so that no black matrix is needed at these locations. Further increases in viewing
angles are also possible by combining the compensation scheme with wide-viewing-angle
polarizers. The compensation scheme can also be applied to reflective TNs for either
direct-view or projection displays.
Stability of Antiferroelectricity Studied Using a Homologous Series of Antiferroelectric Liquid Crystals
Authors: Nakata Michi , Takanishi Yoichi , Ishikawa Ken , Takezoe Hideo , Aoki Yoshio , Nohira Hiroyuki
Published: October 2002

In order to investigate the stability of antiferroelectricity in the smectic
CA
* (SCA
*) phase, the threshold electric field
(E
th) for the field-induced antiferroelectric-ferroelectric phase transition
was evaluated in a homologous series of compounds with a trifluoromethyl group as a
permanent transverse dipole. It was found that E
th decreases with
increasing the chiral chain length. According to X-ray diffraction, the smectic layer
thickness increases linearly with the chiral chain length, suggesting no molecular
conformation change in the homologues and monotonous increase of the distance between two
dipoles in adjacent smectic layers. These two results indicate that the stability of
antiferroelectricity in SCA
* is strongly correlated with the distance
between the dipoles in adjacent layers.
First Principles Study of Atomic-Scale Al2O3 Films as Insulators for Magnetic Tunnel Junctions
Authors: Noriko Watari Noriko Watari , Mineo Saito Mineo Saito , Hisanao Tsuge Hisanao Tsuge , Osamu Sugino Osamu Sugino , Shuhei Ohnishi Shuhei Ohnishi
Published: October 2002

We performed
density-functional calculations with Al/Al2O3/Al structures
as models to study Al2O3 tunnel barriers for
magnetic tunnel junctions.
We found
that aluminum oxide films thicker than 4.6 Å
have pseudogaps without substantial gap states,
which suggests that these films have good insulating
properties.
This finding is consistent with an experimental result where a large
magnetoresistance ratio was attained with a film thickness of
about 8 Å.
Optical Constants of Cubic GaN, AlN, and AlGaN Alloys
Authors: Takanobu Suzuki Takanobu Suzuki , Hiroyuki Yaguchi Hiroyuki Yaguchi , Hajime Okumura Hajime Okumura , Yuuki Ishida Yuuki Ishida , Sadafumi Yoshida Sadafumi Yoshida
Published: October 2002

We have used spectroscopic ellipsometry to investigate, for the first
time, the optical constants of cubic GaN, AlN, and AlGaN alloy epitaxial
layers grown by molecular beam epitaxy. The refractive indices of cubic
AlGaN were found to decrease with increasing Al content, as expected from
the empirical observation that the refractive index decreases with
increasing direct bandgap energy. In the transparent wavelength region, the
refractive indices of cubic AlGaN with lower Al contents are somewhat
larger than those of hexagonal modifications, while with higher Al
contents, the refractive indices of cubic AlGaN and hexagonal AlGaN are almost equal.
We also found that the direct bandgap energies of cubic
AlGaN show a parabolic dependence on the Al content.
Epitaxial Growth and Ultraviolet Photoluminescence of CaF 2/ZnO/CaF 2 Heterostructures on Si(111)
Authors: Masahiro Watanabe Masahiro Watanabe , Yasuhisa Maeda Yasuhisa Maeda , Shun-ichi Okano Shun-ichi Okano
Published: October 2002

The epitaxial growth of zinc oxide (ZnO) nanocrystals embedded in a single-crystalline CaF2 layer on a Si(111) substrate has been demonstrated. Highly c-axis-oriented ZnO 4–10 nm thick was grown on a CaF2(111) layer using radio-frequency (RF) sputtering followed by annealing in ultrahigh vacuum, resulting in the formation of epitaxial self-organized ZnO nanocrystals on CaF2/Si(111). It was found that CaF2 can be grown epitaxially over ZnO/CaF2 by molecular beam epitaxy (MBE), thus the CaF2/ZnO/CaF2 heterostructure has been formed on a Si(111) substrate. Abrupt heterointerfaces between CaF2 and ZnO were confirmed on a transmission electron microscope (TEM) cross section, and ultraviolet (UV) photoluminescence (PL) corresponding to the band-gap energy of ZnO was dominant in PL spectra observed at room temperature.
X-Ray Photoelectron Spectroscopy Characterization of Diamond Thin Film Surfaces for Electronic Device Application
Authors: Maki Tetsuro , Ito Akihiro , Kawamura Hideki , Kobayashi Takeshi , Aoki Masahiko , Kajiyama Kenji
Published: October 2002

Diamond thin film surfaces after the deposition of fluoride and
nitride have been characterized by X-ray photoelectron spectroscopy
to investigate the chemical bonding. A considerable shift to the
higher energy side in the peaks of the C 1s level was observed in
the sample with CaF2 deposited at 500°C. The data suggest
that the fluorination proceeds on the diamond surface via the
deposition of CaF2 and that the degree of fluorination depends
on the kind of adatoms present on the diamond surface before the
deposition of CaF2.
Breakdown and Recovery of Thin Gate Oxides
Authors: Twan Bearda Twan Bearda , Paul W. Mertens Paul W. Mertens , Marc M. Heyns Marc M. Heyns , Hans Wallinga Hans Wallinga , Pierre Woerlee Pierre Woerlee
Published: October 2002

Breakdown events are studied in varying test set-ups with a high
time
resolution. Often a partial recovery from breakdown is observed within a
few ms.
Parameters such as device area, stress conditions and parasitic elements
prohibit the
recovery if they result in a high system impedance. The results suggest
the existence
of a highly conductive path that can be annihilated during breakdown.
Preparation and Characterization of SrBi2(Ta1-xNbx)2O9 Thin Films by Metalorganic Chemical Vapor Deposition from Two Organometallic Source Bottles
Authors: Mitsuya Masatoshi , Ishikawa Katsuyuki , Nukaga Norimasa , Funakubo Hiroshi
Published: October 2002

SrBi2(Ta1-x
Nb
x
)2O9 (SBTN) thin films were first
prepared on Pt/Ti/SiO2/Si substrates by metalorganic chemical vapor deposition
(MOCVD) with high compositional reproducibility. Bi(CH3)3, a mixture of
Sr[Ta(O·C2H5)6]2 and
Sr[Nb(O·C2H5)6]2, and O2 gas were used as sources. The
Nb/(Ta+Nb) ratio in the film was almost the same as that of the source
materials. The film, deposited at 500°C following heat treatment at 800°C
for 30 min in O2 atmosphere, consisted of an almost single phase of SBTN. The
remanent polarization and the coercive field of the 330 nm-thick film were
8.5 µC/cm2 and 91 kV/cm, respectively. This film showed negligible fatigue
after 5×1010 polarization switching cycles.
Formation of Parallel X-Ray Microbeam and Its Application
Authors: Tsusaka Yoshiyuki , Yokoyama Kazushi , Takeda Shingo , Urakawa Masafumi , Kagoshima Yasushi , Matsui Junji , Kimura Shigeru , Kimura Hidekazu , Kobayashi Kenji , Izumi Koichi
Published: October 2002

We have developed a parallel X-ray microbeam of 7×5 µm2in size with a small angular divergence, which aims high-resolution strain measurements in a very local area. The microbeam has been formed by compressing and collimating the X-rays from a third-generation undulator source using successive asymmetric reflections. Using this beam, we have evaluated the strain induced by field oxidation in silicon wafers by rocking curve measurements. We have observed that the lattice constant in the Si region near the oxide film edge is contracted and that in the SiO2/Si region is extended. The difference between these lattice constants is as small as about Δd/d∼±5×10-6.
Quantum Point Contacts in a Density-Tunable Two-Dimensional Electron Gas
Authors: Sebastien Nuttinck Sebastien Nuttinck , Katsushi Hashimoto Katsushi Hashimoto , Sen Miyashita Sen Miyashita , Tadashi Saku Tadashi Saku , Yoshihisa Yamamoto Yoshihisa Yamamoto , Yoshiro Hirayama Yoshiro Hirayama
Published: October 2002

Quantum point contacts fabricated using a backgated two-dimensional electron-gas system show clear quantized features and a 0.7 anomaly in conductance. Using these density-tunable point contacts, we have studied the behavior of the 0.7 anomaly. The 0.7 step shifts down to around 0.5 as the electron density is decreased under a zero magnetic field. This suggests that electron-electron interactions play an important role in forming the conductance anomalies of quantum point contacts.
Single Wafer Furnace and Its Thermal Processing Applications
Authors: Yoo Woo Sik , Fukada Takashi , Kuribayashi Hiromitsu , Kitayama Hirofumi , Takahashi Nobuaki , Enjoji Keiichi , Sunohara Kiyoshi
Published: October 2002

A resistively heated, vacuum and atmospheric pressure compatible, single wafer furnace (SWF) system is proposed to improve operational flexibility of conventional furnaces and productivity of single wafer rapid thermal processing (RTP) systems. The design concept and hardware configuration of the SWF system are described. The temperature measurement/control techniques and thermal characteristics of the SWF system are described. Typical process results in TiSi formation, implant anneal and thin oxide formation using the SWF system are reported. Due to the vertically stacked, dual chamber configuration and steady state temperature control, very flexible operation with a high throughput at a minimal power consumption (<3.5 kW per process chamber at 1150°C) was realized. Many thermal processes used in furnaces and RTP systems can easily be converted to SWF processes without decreasing cost performance and/or deteriorating process results by using the SWF system.
Unified Simulation of Silicon Oxidation Based on the Interfacial Silicon Emission Model
Authors: Uematsu Masashi , Kageshima Hiroyuki , Shiraishi Kenji
Published: October 2002

We have simulated silicon oxidation taking into account the emission of a large number of silicon atoms from the interface, which governs the silicon-oxidation rate. The silicon emission model enables the simulation to be done using the oxidant self-diffusivity in the oxide with a single activation energy. The simulation has deduced a silicon emission rate that exhibits a break point in its activation energy at around 1000°C, which is attributed to the viscoelastic properties of the oxide. Using a unified set of parameters, the whole range of oxide thickness is fitted in a wide range of oxidation temperatures (800–1200°C) without any empirical modifications.
Synthesis, Crystal Structure and Magnetic Properties of Iron Particles Encaged in Carbon Nanocapsules
Authors: Masuda Morio , Maeda Kohji , Kobayashi Tadashi , Shiomi Shigeru , Fujiwara Yuhji , Saito Yahachi
Published: October 2002

Soot containing carbon-coated iron particles was produced by the arc-evaporation of a Fe-packed graphite rod in a modified fullerene generator. X-ray diffraction and electron microscopy revealed that it consisted of carbon nanocapsules encaging α-Fe, γ-Fe and Fe3C particles. Helium gas pressure during arc-evaporation was varied from 1 to 5 atm as well as from 50 to 500 Torr. The fraction of the γ-Fe component increased with helium gas pressure. The fraction of α-Fe, γ-Fe and Fe3C components in the soot prepared in helium gas of 5 atm was estimated to be 45, 25, and 30 wt%, respectively.