bluuebunny/crossref_metadata_2025 huggingface dataset:
Reflective Microdisplay Using Anti-Ferroelectric Liquid Crystals
Authors: Lu Minhua , Yang K. H. , Sanford J. L.
Published: October 2002

We have characterized the MLC00089 antiferroelectric liquid
crystal (AFLC) mixture in terms of tilt angle, reflectance, and
response time as a function of applied voltage. The derived highest
contrast ratio was about 700 to 1. We also applied the simulated
thin-film-transistor (TFT)-type circuit to direct drive a hardwired
Si-based chip filled with the AFLC mixture by varying the values of
storage capacitor and gate on-time. We found that adding a storage
capacitor is effective to increase the signal if the gate on-time of
the TFT is shorter than the AFLC response time. We also used quasi-DC
driving with a short gate on-time on the hardwired chip as well as a
Si-based reflective 1024×1280 (SXGA) microdisplay. We have
accomplished the effective operation of the microdisplay using 5-frame
quasi-DC driving with extrapolated polarity-frame inversion at 360 Hz
suitable for field-sequential color displays using pulsed-light
sources (light-emitting diodes) as well as optical storage
applications.
Influences of Interfacial Misfit Dislocations on Cathodoluminescence of ZnS/GaAs(001) Studied by Transmission Electron Microscopy
Authors: Mitsui Tadashi , Yamamoto Naoki
Published: October 2002

The change in cathodoluminescence (CL) spectra of thin ZnS films
grown by molecular beam epitaxy (MBE) on GaAs(001) has been examined
by a low-temperature CL measurement system combined with a
transmission electron microscope (TEM). It was found that structural
defects such as dislocations and stacking faults formed in the ZnS
films seriously affect CL intensity within a distance of 200 nm
from the interface, and their effect becomes negligibly small at
distances of more than 600 nm. The relative intensities of the
exciton-associated emissions are small in comparison with the
non-exciton-associated emissions for the thin samples that have
relatively large stacking fault densities. This fact suggests that
the stacking faults accompanying the partial dislocations suppress
the generation of excitons. Moreover, the peak of the
non-exciton-associated emission shifts markedly to long wavelengths,
as the epitaxial layer thickness becomes less than 200 nm. The peak
shift is attributed to the internal stress change in the ZnS film
due to the stress caused by the lattice mismatch and the relaxation
by the introduced defects.
Analysis of Photovoltaic Properties of C60-Si Heterojunction Solar Cells
Authors: Kojima Nobuaki , Yamaguchi Masafumi , Ishikawa Naomi
Published: October 2002

Photovoltaic and photoconductive properties of C60/p-Si heterojunction
solar cells grown by molecular beam epitaxy have been analyzed using a device
simulator based on measured optical absorption coefficients of C60 films. The
spectral response of cell photocurrents in the short wavelength region of less than
700 nm is determined to be due to the optical absorption of the C60 layer. Marked
improvements in photovoltaic properties of the cells have also been observed by
increasing the light intensity. Analytical results suggest that photoconductive effects
on C60 layers under light illumination increase the carrier concentration and
decrease the series resistance of the C60 layer, resulting in an increase of the
open-circuit voltage and short-circuit current of the C60/p-Si heterojunction
cells. The possibility of improving the conversion efficiency of C60-based solar
cells is also discussed.
Morphological Change and Inhibitory Effect on Ag Surface by ArF Excimer Laser Irradiation
Authors: Tabuchi Satomi , Tabata Hitoshi , Kawai Tomoji
Published: October 2002

We have carried out studies of morphologies of silver surfaces
irradiated by ArF eximer laser irradiation in vacuum
(10-3 Pa). Three different morphologies were observed
corresponding to various laser fluences. In the high irradiation
region (above 600 mJ/cm2), wave-like ridges and droplets were
observed. In the intermediate region (about 200 mJ/cm2),
ripples were observed. In the low irradiation region (below
70 mJ/cm2), changes were not observed using an optical
microscope, but were with an atomic force microscope (AFM). We have
clarified that laser irradiation in the fluence range below
70 mJ/cm2 yields a silver surface with excellent
corrosion-resistant properties.
Study of Accumulation Effect of Bombarding N2
+ Ions on Al Surface by Auger Electron Spectroscopy
Authors: Mitsuhashi Riichirou , Mizuhara Yuzuru , Beag Young Whoan , Shimizu Ryuichi
Published: October 2002

The accumulation effect of bombarding N2
+ ions on an Al
surface
was investigated by Auger electron spectroscopy (AES) at N2
+ ion
primary energies of 0.5, 1 and 3 keV. The result revealed direct
evidence of the accumulation effect in that the concentration of
nitrogen at the steady state is higher for the lower primary
energy. This accumulation effect allows an Al surface under
N2
+ ion
bombardment to be of stoichiometric composition by choosing an
appropriate primary energy, leading to the crystal growth of AlN film.
Observation of Retention of Optical Absorption Change in Methylene Blue Sensitized Gelatin and Polyvinyl Alcohol Plates on He–Ne Laser Irradiation
Authors: Pradeep G. , Cyriac Shiji , Ramkumar S. , Kartha C. Sudha
Published: October 2002

The photochemical reactions of methylene blue in gelatin and polyvinyl
alcohol matrices due to He–Ne laser exposure are investigated. Laser
irradiation results in the formation of a new absorption peak which matches
with that of thionine. Retention of this optical absorption change due to
irradiation for several months is observed. The present study confirms that on
irradiation some irreversible changes are also occurring in methylene blue in
addition to the reversible change to leuco methylene blue. Possibility of
permanent recording is suggested.
Distribution of Average Electric Field in tris-(8-hydroxyquinoline)aluminum and 4,4′-bis[N-(1-naphthyl)-N-phenylamino]-biphenyl-based Double-Layer Light-Emitting Diodes
Authors: Yamada Toshiki , Rohlfing Frank , Tsutsui Tetsuo
Published: October 2002

We have determined the distribution of the average electric field in double-layer
organic light-emitting diode structures fabricated with
4,4′-bis[N-(1-naphthyl)-N-phenylamino]-biphenyl (α-NPD) as
hole-transport material and tris-(8-hydroxyquinoline)aluminum (Alq) as
electron-transport and emissive material, by means of electroabsorption spectroscopy.
We found that the electric field in the α-NPD layer is considerably smaller than
that in the Alq layer in the forward bias and that most of the dc bias is used for the
formation of the electric field in the Alq layer, especially below the turn-on voltage,
whereas in the reverse bias, the electric field in the Alq layer is identical to that in
the α-NPD layer. This could be attributed to the injection of a relatively large
amount of holes from the indium-tin-oxide electrode into the α-NPD and their
transport, and the hole-blocking property of Alq. An abrupt change of the average
electric field in both the Alq and α-NPD layers was observed in the vicinity of
the turn-on voltage.
Data Processing for Obtaining Atomic Images from SrTiO3 X-Ray Fluorescence Hologram
Authors: Hayashi Kouichi , Sai Makoto , Yamamoto Tokujirou , Kawai Jun , Nishino Makoto , Hayakawa Shinjiro , Gohshi Yohichi
Published: October 2002

It is difficult to obtain a clear atomic image from a measured X-ray fluorescence hologram,
because the holographic undulation in the angular distribution of the X-ray fluorescence intensity is
feeble. We introduce here our numerical data process to reconstruct an atomic image from the
SrTiO3 (001) hologram data reported in a previous paper [J. Kawai et al..: Anal. Sci. 14 (1998) 903].
The holographic oscillation, which could not be seen in the raw data, was revealed by the Savitzky-Golay smoothing method. We also considered the effect of the hologram size on the reconstructed
image of Sr atoms, and found that the spatial resolution of the image became higher with an increase
of the size in the hologram.
Coupled-Mode Analysis of Loss in Bent Single-Mode Optical Fibers
Authors: Mirianashvili Maria , Ono Kazuo , Hotta Masashi
Published: October 2002

In this study, we analyzed the loss formation in bent
single-mode optical fibers using a
semi-analytical method, which is a combination of conformal mapping
and coupled-mode
theory based on the two-layer step-index optical fiber model. The pure
bend loss results were
compared to those reported in the existing literature. The advantage
of using this method is
that it provides insight into the mode field behavior and loss
formation in bent fibers and
accurately presents the power distribution in the cross section of the
fibers.
Thermally-Grown Silicon-Dioxide Waveguides for Use in UV Light
Authors: Ura Shogo , Nakashiba Toru , Suhara Toshiaki , Nishihara Hiroshi , Lambeck Paul V.
Published: October 2002

Silicon dioxide is transparent in wavelength down to vacuum UV,
and high quality film is obtained by thermal oxidation of Si
substrate. Both of higher-refractive-index guiding core and
lower-index optical buffer layers consist of SiO2 films
thermally-grown at different temperatures on Si
substrate. Silicon-on-insulator wafer, of which buried oxide layer
of 3 µm thickness had been treated at >1100°C to be
optical buffer layer, was held in steam flow at 800°C for
oxidizing top Si layer to form SiO2 guiding core layer of
1.2 µm thickness. Guiding characteristics were measured and
showed good agreement with theoretical prediction.
Micromachined Semiconductor Vertical Cavity for Temperature Insensitive Surface Emitting Lasers and Optical Filters
Authors: Koyama Fumio , Amano Takeru , Furukawa Noriyoshi , Nishiyama Nobuhiko , Arai Masakazu , Iga Kenichi
Published: October 2002

We propose a micromachined vertical cavity resonator enabling
temperature insensitive operation for surface emitting lasers or
optical add/drop filters. The strain-induced displacement from
differential thermal expansion is used to compensate the wavelength
shift caused by temperature variation. Also, a wavelength-trimming
technology using the same principle with precise strain control is
suggested. The possibility of a drastic reduction in the temperature
sensitivity of wavelengths, as well as precise wavelength
adjustment, is presented. We fabricated a micromachined vertical
cavity filter with a GaAlAs/GaAs multilayer reflector, which is
mechanically tuned by differential thermal expansion. We observed a
large negative temperature coefficient of the resonant
wavelength. It is demonstrated that its temperature dependence can
be widely controlled by the proposed concept. The possibility of
temperature-insensitive operation is discussed.
Development of Integrated Optical Unit for Large Storage Capacity Floppy Disk
Authors: Kousei Sano Kousei Sano , Shin-ichi Kadowaki Shin-ichi Kadowaki , Hajime Hatada Hajime Hatada , Michiyasu Takano Michiyasu Takano , Tetsuo Saimi Tetsuo Saimi
Published: October 2002

A small integrated optical unit suitable for a large storage capacity floppy disk drive is proposed. The optical unit is 6.8 mm wide, 3.3 mm deep, and 3.0 mm high. The distance between the laser diode and the focused beam on the disk is only 4.0 mm.
The optical unit consists of two components, a lens unit and a laser-detector unit. In this optical unit, with the beam slanting incident on the disk, the reflected beam takes another path. Thus, a diffraction grating, a lens, and a deflector can be integrated into one component. The optical unit allows wide disk tilting of up to 2.4 degrees.
Two-Stage Optical Data Storage in Azo Polymers
Authors: Egami Chikara , Kawata Yoshimasa , Aoshima Yasuo , Alasfar Samer , Sugihara Okihiro , Fujimura Hisashi , Okamoto Naomichi
Published: October 2002

We have demonstrated two-stage optical memory in a photoaddressable azo polymer. The polymer serves as a data storage medium with two recording
mechanisms: photoanisotropic modulation and surface-shape modulation. We can
select the recording mechanism by manipulating beam energies for
recording. The characteristics can be motivated to rewritable and
write-once optical memories: polarization-multiplex bit memories,
surface-modulated bit memories and surface-modulated holographic
memories.
Two-Dimensional Quantization Effect on Indirect Tunneling in an Insulated-Gate Lateral pn-Junction Structure with a Thin Silicon Layer
Authors: Omura Yasuhisa
Published: October 2002

In this paper, the multi-negative conductance property detected at low
temperatures in a silicon-on-insulator insulated-gate pn-junction device with a
10-nm-thick silicon layer is described. Important aspects of lateral low-dimensional
tunneling process are examined by a theoretical formulation. A comparison of the
characteristics of devices with a 10-nm-thick or a 90-nm-thick silicon layer indicates
that the strong two-dimensional confinement effect plays an important role in
multi-negative conductance. The theory predicts that a “resonance effect” between two
subband levels results in the multi-negative conductance in the device with the
10-nm-thick silicon layer.
Formation of CuInSe2 Thin Films by H2Se/Ar Treatment of Thermally Evaporated Metallic Precursors From a Single Crucible
Authors: Alberts V. , Molefe P.
Published: October 2002

In this study, CuInSe2 thin films were prepared by a
relatively
simple and reproducible two-stage growth technique. During the
precursor formation step predetermined quantities of Cu and In were
thermally evaporated from a single crucible in a Se vapour
atmosphere. These low temperature prepared precursor films were
subsequently reacted with a controlled H2Se/Ar atmosphere in
order
to produce fully reacted compound films. From a systematic
investigation of the material properties of the films as function of
H2Se/Ar reaction temperature, we were able to determine optimum
growth parameters. Single-phase material with uniform surface
morphologies and a relatively high degree of in-depth compositional
uniformity was produced by this relatively simple and fast growth
technique. X-ray fluorescence (XRF) Kα1,2 measurements
revealed no
compositional changes after the high temperature selenization
stages. This observation confirmed that the generally reported
material losses from these classes of materials are prevented and
that the final composition of the compound films is controlled
simply by the initial material masses selected during the precursor
formation stage.
Wavelength Tuning of GaAs/AlGaAs Quantum-Well Infrared Photo-detectors by Proton Implantation Induced Intermixing
Authors: Liu X. Q. , Li N. , Lu W. , Li N. , Yuan X. Z. , Shen S. C. , Fu L. , Tan H. H. , Jagadish C.
Published: October 2002

Proton implantation induced intermixing was used to tune the quantum well
infrared photo-detector (QWIP) response wavelength, which may provide a method of
fabricating two-color QWIP devices. Obvious red shift of response wavelength as large
as 0.6 µm was observed relative to the reference sample that was annealed without
implantation, from 7.7 µm to 8.3 µm. Two response wavelengths for the
highest-dose implanted sample were observed in the photo-current spectra. In the
highest dose case (5×1015 H/cm2), the dark current increased by an
order of magnitude and peak responsivity decreased by a factor of 3 for the implanted
and annealed sample. This has been attributed to the raising of the ground state energy
level in the intermixed quantum well and residual damage in the implanted and annealed QWIPs.
Simulation of Temperature Dependence of Microwave Noise in Metal-Oxide-Semiconductor Field-Effect Transistors
Authors: Obrecht Michael S. , Manku Tajinder , Elmasry Mohamed I.
Published: October 2002

We present results of a two-demensional (2D) numerical simulation of high-frequency noise in a short-channel metal-oxide-semiconductor field-effect transistors (MOSFET). Conventionally this noise in MOSFETs is treated as a thermal noise with a rather slow
temperature dependence of the noise spectra. On contrary, the results obtained indicate that this dependence is more of an exponential kind, typical for a shot noise. Shot noise is conventionally related to a forward biased p-n junction where the
current is mostly due to diffusion in the quasi-neutral region. We therefore speculate that most likely in short channel MOSFETs most of the high-frequency noise is produced not in the cut-off region of the channel but near the source side of
the channel where diffusion current component is dominant.
Mn and Mg Interdiffusion and Magnetotransport Properties of La0.7Sr0.3MnO3 Films on MgO (100) Substrate
Authors: Nakamura Keikichi , Liu Xiangdong , Hatano Takeshi , Jiao Zhenkuwan , Shang Ke , Ishii Akira
Published: October 2002

An anomalous annealing temperature dependence of
magnetotransport properties has been observed in sol–gel-derived
polycrystalline thin films of La0.7Sr0.3MnO3 (LSMO)
on MgO substrate. The resistivity peak temperature (T
p)
drops dramatically with increasing annealing temperature, while the
peak resistivity rises sharply. The Rutherford backscattering
analysis of these films strongly points to the existence of Mn and
Mg interdiffusion for samples annealed at temperatures as low as
650°C; this interdiffusion was enhanced with increasing
annealing temperature. In order to confirm the effects of
interdiffusion, we fabricated epitaxial films with Mn site
substitution by Mg and compared their physical properties with those
of polycrystalline films on MgO substrate. It is argued that the
observed anomalous annealing temperature dependence arises from a
combination of Mn site substitution by Mg and the grain boundary
spin-polarized scattering of polycrystalline film on MgO substrate.
Photoluminescence and Electroluminescence of (Gd2O3–Ga2O3):Ce Thin Film
Authors: Xu Xiulai , Hou Yanbing , Xu Zheng , Wang Xiaowei , Xu Xurong
Published: October 2002

A novel electroluminescence oxide phosphor
(Gd2O3–Ga2O3):Ce has been prepared by electron
beam evaporation. The emission peaks of photoluminescence lie at
390 nm and a shoulder at 440 nm. However, the electroluminescence
of the (Gd2O3–Ga2O3):Ce thin film have four
emission peaks at 358 nm, 390 nm, 439 nm and 510 nm,
respectively. The optical absorption of
(Gd2O3–Ga2O3):Ce thin film and the
photoluminescence of composite materials with various ratios of
Ga2O3/(Gd2O3+Ga2O3) have also been
described to investigate the origin of emission of photoluminescence
and electroluminescence.
A Fictive Stress Model Calculation of Stress-Overshoot: A Nonlinear Viscoelastic Behavior in Metallic Glass
Authors: Chen Ho-Sou , Kato Hidemi , Inoue Akihisa
Published: October 2002

A model, based on the hypothesis of stress-induced structural relaxation and a
concept of fictive stress, is proposed for nonlinear viscoelastic behavior in glassy
materials. A model calculation has been carried out on the stress-overshoot
phenomenon observed in metallic glasses. The model calculation reproduces the
experimental results of a Pd40Ni10Cu30P20 glass fairly well, in
particular, the development of stress-overshoot behavior with increasing strain rate
and lowered temperature. In addition, the model reveals a stress-overshoot and
-undershoot oscillatory behavior which has not been reported previously in metallic
glasses, but has been observed in many polymer solutions.
Laser-Induced Shock Compression of Tantalum to 1.7 TPa
Authors: Wakabayashi Kunihiko , Hattori Shyuhei , Tange Tomoyuki , Fujimoto Yasushi , Yoshida Masatake , Kozu Naoshi , Tanaka Kazuo A. , Ozaki Norimasa , Sasatani Yasufumi , Takenaka Hisataka , Nakamura Kazutaka G. , Kondo Ken-ichi
Published: October 2002

An extremely high pressure (1.74±0.22 TPa) was generated in Ta by using
strong shock waves driven by direct irradiation of laser beams from the GEKKO XII glass
laser system. The shock velocity was measured directly and the particle velocity and
pressure were obtained using an impedance-matching technique by considering the
intensity profile of the laser beams.
Structural Refinement of X-Ray Diffraction Profile for Artificial Superlattices
Authors: Yurika Ishibashi Yurika Ishibashi , Naoki Ohashi Naoki Ohashi , Takaaki Tsurumi Takaaki Tsurumi
Published: October 2002

A new structural refinement process for BaTiO3/SrTiO3 (BTO/STO) artificial superlattices was proposed, taking into account the effect of interdiffusion between BTO and STO. The samples were prepared using the molecular beam epitaxy (MBE) method on SrTiO3(001) substrates at 600°C. The step model, the phonon model and the supercell model were employed for simulation of the X-ray diffraction (XRD) profiles of the superlattices. The supercell model can deal with arbitrary variations of chemical composition and lattice spacing. A discrepancy in the intensity of satellite peaks was observed when the interdiffusion between BTO and STO was not incorporated in the simulation. In the phonon model, the concentration profile due to interdiffusion was first calculated using Fick's second law, and the coefficient of Fourier series describing the lattice distortion and modulation of the structure factor was determined. The XRD profiles thus simulated almost agreed with the observed ones, but the intensity of Laue peaks was not consistent with the observation. The degree of interdiffusion at each interface was then changed throughout the superstructures using the supercell model, and it was shown that the accuracy of simulation improved markedly.
Characteristics of Dual Polymetal (W/WNx/Poly-Si) Gate Complementary Metal Oxide Semiconductor for 0.1 µm Dynamic Random Access Memory Technology
Authors: Kim Yong–Hae , Chang Sung–Keun , Kim Seon–Soon , Choi Jun–Gi , Lee Sang–Hee , Hahn Dae–Hee , Kim Hyung–Duck
Published: October 2002

We developed a dual polymetal (W/WNx/poly-Si) gate complementary metal oxide semiconductor (MOS)
down to a 0.15 µm gate length.
The short-channel effects are effectively suppressed and a saturation current of 300 µA/µm
is obtained for nMOS and 110 µA/µm is observed for pMOS at a 0.15 µm gate length.
The lower saturation current of pMOS is attributed both to the p+-doped poly gate depletion and to the
hole mobility degradation due to the increased vertical electric field in the surface-channel pMOS.
Boron penetration is not observed with pure SiO2 gate dielectrics. The gate induced drain leakage
current could be markedly reduced by optimizing the well doping below the gate edge.
A New Lateral Dual-Gate Thyristor with Current Saturation
Authors: Lee You-Sang , Byeon Dae-Seok , Han Min-Koo , Choi Yearn-Ik
Published: October 2002

A new lateral dual-gate thyristor was proposed and fabricated in order to eliminate the
parasitic latch-up problem. The device exhibited the excellent
current-saturation characteristic of a current density of
1200 A/cm2, even at the high anode-gate voltage of 29 V,
through the elimination of the parasitic thyristor in the device
structure. The device, which is suitable for power integrated circuits
(PICs) due to its lateral structure, also exhibited good temperature
characteristics appropriate for high-temperature operations.
A New Fabrication Process for Low-Loss Millimeter-Wave Transmission Lines on Silicon
Authors: Ishii Hiromu , Sahri Nabil , Nagatsuma Tadao , Machida Katsuyuki , Saito Kunio , Yagi Shouji , Yano Masaki , Kudo Kazuhisa , Kyuragi Hakaru
Published: October 2002

The new type of coplanar waveguide for millimeter-wave transmission was
fabricated on silicon by chemical mechanical polishing and selective electroplating
processes based on silicon technology. The thick interconnections obtained using these
processes have less conductor loss than the conventional interconnections, and the deep
grooves on both sides of a signal line in this new waveguide reduce the dielectric loss
caused by the high permittivity of the silicon substrate. The electro-optic sampling
technique confirmed that the new waveguide has excellent millimeter-wave
propagation characteristics, low effective permittivity and low attenuation, at
frequencies up to 300 GHz. The new fabrication processes should be useful in
combining millimeter-wave systems with ultralarge-scale integrated circuits on
silicon.
A Novel Diffusion Resistant P-Base Region Implantation for Accumulation Mode 4H–SiC Epi-Channel Field Effect Transistor
Authors: Kumar Rajesh , Kozima Jun , Yamamoto Tsuyoshi
Published: October 2002

A novel implantation technique using the carbon (C) and boron
(B) sequential implantation is employed to control the B lateral and
vertical diffusion from the p-base region of the planar silicon
carbide (SiC) epi-channel field effect transistor (ECFET). The
current deep level transient spectroscopy measurements were
performed to establish the inter-correlation between the B enhanced
diffusion and the electrically active defects introduced by the C
and B sequential implantation. It was found that the formation of
deep defect level is completely suppressed for the same ratio
(C:B=10:1) as that for the B diffusion in 4H–SiC. A
diffusion mechanism which is correlated to the formation of D center
was proposed to account for the experimentally observed B enhanced
diffusion. The effectiveness of C and B implantation technique in
suppressing the junction field effect transistor (JFET) pinch effect
is clearly visible from the 3–4 fold increase in drain current of
fabricated 4H–SiC ECFET for p-base spacing which was scaled down to
about 3 µm. This novel diffusion resistant implantation technique
open doors for the larger packing densities through unit-cell pitch
reduction for SiC high power device applications.
Monte Carlo Sphere Model for Effective Oxide Thinning Induced Extrinsic Breakdown
Authors: Huang Huan-Tsung , Chen Ming-Jer , Chen Jyh-Huei , Su Chi-Wen , Hou Chin-Shan , Liang Mong-Song
Published: October 2002

The Monte Carlo sphere model is extended to deal with the
extrinsic time-dependent-dielectric-breakdown (TDDB) by
incorporating the well-known “effective oxide thinning”
concept. Percolation simulation, based on this model for the first
time, evidences that the process defects induced extrinsic TDDB is
also statistical in nature as is the intrinsic one, and is
characterized by a probability function defining local oxide
thinning. The experimental bimodal or even multimodal characteristics
can be reproduced accordingly. Furthermore, the simulation results in
the extrinsic regime are found to be sample-size (i.e., the total
number of samples that span the breakdown statistics) dependent,
suggesting that care should be taken when evaluating the extrinsic
TDDB data in a real manufacturing process.
Fast Deposition Process for Graded SiGe Buffer Layers
Authors: Känel Hans von , Rosenblad Carsten , Kummer Matthias , Müller Elisabeth , Graf Thomas , Hackbarth Thomas
Published: October 2002

Low-energy plasma-enhanced chemical vapour deposition (LEPECVD) is shown to allow for the synthesis of relaxed graded Si1-x
Gex, (0≤x≤1) buffer layers at deposition rates above 5 nm/s. On the basis of X-ray reciprocal space mapping, transmission electron microscopy, atomic force microscopy and defect etching, the quality of these buffer layers is shown to be comparable to similar structures grown by other techniques at much lower rates. LEPECVD and molecular beam epitaxy (MBE) have been combined for the synthesis of modulation-doped Si quantum wells, yielding mobilities up to 150000 cm2/Vs at 2 K.
Optical Investigations of Solid-Phase Crystallization of Si1-xGex
Authors: Yamaguchi Shinya , Sugii Nobuyuki , Nakagawa Kiyokazu , Miyao Masanobu
Published: October 2002

Solid-phase crystallization (SPC) of amorphous Si1-xGex(0≦x≦0.3) formed by ion-implantation into epitaxially-grown single crystals was investigated by using ellipsometric spectroscopy. We found that the attenuation constant of optical transition is proportional to the calculated defect density. Annealing-temperature profiles of the defect density during SPC of Si1-xGexwere obtained. It was found that the higher the defect density in the amorphous state, the lower the crystallization temperature of Si1-xGex. And increasing Ge concentration in Si, the crystallization temperature decreases monotonically, which implies a decrease in the activation energy of SPC. It is concluded that the increased lattice constant and reduced strain (caused by Ge introduction into Si) mainly control the SPC of Si1-xGex.
Electrical Properties of Metal-Ferroelectric-Insulator-Semiconductor (MFIS)- and Metal-Ferroelectric-Metal-Insulator-Semiconductor (MFMIS)-FETs Using Ferroelectric SrBi2Ta2O9 Film and SrTa2O6/SiON Buffer Layer
Authors: Tokumitsu Eisuke , Fujii Gen , Ishiwara Hiroshi
Published: October 2002

Nonvolatile memory operations of p-channel
metal-ferroelctric-insulator-semiconductor (MFIS)- and
metal-ferroelectric-metal-insulator-semiconductor (MFMIS)-FETs using ferroelectric
SrBi2Ta2O9 (SBT) film and SrTa2O6(STA)/SiON stacked buffer
layer have been demonstrated. It is determinded that the Al/STA/SiON/Si structure
with a SiO2 equivalent thickness of 3.7 nm has low leakage current of
10-8 A/cm2. The memory window of 1.1 V is obtained for Pt/SBT/STA/SiON
MFIS-FETs, whereas Pt/SBT/Pt/STA/SiON/Si MFMIS-FETs have memory windows as
large as 3.0 V when the area ratio S
M/S
F is 3.8 or 5.9.
Furthermore, it is also demonstrated that by reducing the metal-ferroelectric-metal
(MFM) capacitor area, significant improvement of data retention characteristics can be
achieved. The drain current on-off ratio remains at more than three orders of magnitude
even after an elapse of 10 h.
Dependence of Subthreshold Hump and Reverse Narrow Channel Effect on the Gate Length by Suppression of Transient Enhanced Diffusion at Trench Isolation Edge
Authors: Jung Jong-Wan , Kim Jong-Min , Son Jeong-Hwan , Lee Youngjong
Published: October 2002

For the first time to our knowledge, we have shown that
subthreshold hump and reverse narrow channel effect characteristics
depend on the gate length, and that the hump strength has a peak
point at the gate length where the threshold voltage is highest. In
order to explain these effects, we proposed a new model in which the
boron transient enhanced diffusion at the trench isolation edge is
more suppressed than that at the middle channel. The simulation
results using the proposed model agreed well with the experimental
results.
Study of an Elevated Drain Fabrication Method for Ultra-Shallow Junction
Authors: Nakano Masayuki , Kotaki Hiroshi , Sugimoto Kazuo , Okumine Tetsuya , Yoshioka Fumiyoshi , Kakimoto Seizo , Ohta Kenji , Hashizume Nobuo
Published: October 2002

An elevated diffusion layer fabricated from polycrystalline
silicon (poly-Si) by solid phase diffusion was investigated in
detail by secondary-ion mass spectroscopy (SIMS) analysis. We
clarified that it was necessary to control the native oxide in the
poly-Si/Si substrate interface and use small-grained poly-Si to
fabricate uniform and controllable shallow junctions. The
low-capacitance sidewall-elevated drain (LCSED) metal oxide
semiconductor field-effect transistor (MOSFET) fabricated by the
oxygen-free load-lock low-pressure chemical vapor deposition (LPCVD)
poly-Si (L/L poly-Si) was extremely effective for marked scaling
down of transistor size and realizing an ultra low reversed junction
leakage current.
New Process for Si Nanopyramid Array (NPA) Fabrication by Ion-Beam Irradiation and Wet Etching
Authors: Koh Meishoku , Sawara Souichi , Goto Tomomi , Ando Yoshinori , Shinada Takahiro , Ohdomari Iwao
Published: October 2002

It has been found that the rate of Si etching by hydrazine
(N2H4H2O) is drastically retarded by ion-beam
exposure. By utilizing this new phenomenon, a simple process of
fabricating nanopyramid arrays (NPAs) on a Si surface is
proposed. Two-dimensional arrays of dots and lines are written
directly on a Si substrate with 60 keV Si, P and BF2 ion beams
at doses of 1013–1015 cm-2. Subsequently, the Si
substrate is dipped in hydrazine solution, where unexposed regions
are selectively etched by hydrazine. Using this simple process,
130 nm convex NPAs with 200 nm pitch and 40 nm concave NPAs with
150 nm pitch can be fabricated easily. It is shown that the
electrical property of the apex of the pyramid can be controlled by
dopant ion irradiation. The cause of the retarded etch rate of
ion-beam-exposed Si by hydrazine is comprehensively discussed.
A New Bit-Line-Controlled Self-Convergent Multilevel AND-Type Flash Memory
Authors: Chou Amy Hsiu-Fen , Yang Evans Ching-Song , Wong Wei-Zhe , King Ya-Chin , Hsu Charles Ching-Hsiang
Published: October 2002

In this paper, we propose a new programming technique for
multilevel AND-type flash memory. It achieves multiple programmed
states through a bit-line-controlled self-convergent
operation. Experimental results demonstrate superior capability of
tightening threshold voltage distribution and significant
improvement in endurance characteristics. Excellent immunity to
program disturbance is also demonstrated.
On the Program and the Read of Multilevel Storage Using Source Side Injection Flash Memory
Authors: Liu Chun-Mai , Brennan James , Guo Jr. , Kordesch Albert V. , Su Kung-Yen
Published: October 2002

A comprehensive study of read methods and program for multilevel storage on a source-side-injection (SSI) Flash memory is
reported. A methodology of evaluating and optimizing read method and multilevel program is demonstrated. This has been
successfully applied to the development of a multilevel analog memory for voice recording applications and is suitable for the
development of multilevel-based high-density digital Flash memory.
Simulated Threshold Voltage Adjustment and Drain Current Enhancement in Novel Striped-Gate Nondoped-Channel Fully Depleted SOI-MOSFETs
Authors: Koh Risho
Published: October 2002

To enhance the performance of metal-oxide-silicon field-effect-transistors (MOSFETs), a new device having a Silicon-on-insulator (SOI) structure, called a striped-gate SOI-MOSFET, is proposed and its electrical characteristics are estimated by device simulation. The threshold voltage of this device is controlled by changing the length of a metal layer interposed in the gate electrode. A set of systematic device simulations reveals a type of two-dimensional effect in the gate electric field provides a continuous threshold voltage control for a non-doped channel SOI-MOSFET, and that the suppression of the channel doping provides a large drain current. A circuit simulation on a 2-input complementary-MOS (CMOS) NAND gate chain comprising the devices shows that the operation speed is enhanced by 46% compared with that of bulk MOSFETs, due to the device's large drain current and small parasitic capacitance.
Surface States of Mica and Contact Charging
Authors: Hashimoto Yuichi , Sakakibara Takeshi
Published: October 2002

Through investigation of photoelectron emission from the surface of mica with ultraviolet irradiation, it has been clarified that the surface states of mica play an important role not only in
the electron emission but also in the electronic conduction of the surface. To study this in more
detail, photothresholds of the electron emission from the surface have been measured for
Muscovite mica treated with fast atom bombardment (FAB) under various conditions caused by
contact charging generated by contact with a biased conductive brush. In addition, another static
approach was performed with corona charging for deposition of charges on the surface of mica. The photothreshold for FAB-treated specimens increased markedly from 5.0 eV to 5.8 eV with
respect to an increase of negative contact charging. Such change of the photothreshold has not
been observed for FAB-treated specimens after corona charging. Such a phenomenon is
concluded to be caused by the transport of electrons between the conductive brush and the
surface states of mica in the range of 5.0 to 5.8 eV. In this paper, we will demonstrate that the
surface states of mica are closely related to contact charging as well as to the electronic
conduction state of the surface.
Charging States of Si Quantum Dots as Detected by AFM/Kelvin Probe Technique
Authors: Shimizu Naoji , Ikeda Mitsuhisa , Yoshida Eiji , Murakami Hideki , Miyazaki Seiichi , Hirose Masataka
Published: October 2002

Hemispherical Si quantum dots have been self-assembled on
thermally grown 3.2-nm-thick SiO2/p-Si(100) by low-pressure
chemical vapor deposition of silane. The charging states of the Si
quantum dots have been detected as surface potential changes by
using an atomic force microscopy/Kelvin force probe method. From the
relationship between the measured surface potential changes and the
charging energy of a single dot, the number of electrons retained in
a dot has been estimated to be one. Furthermore, it is found that
electron extraction from neutral dots can be achieved to create a
hole at each dot.
Excess Noise Characteristics of Hydrogenated Amorphous Silicon Avalanche Photodiode Films Using Functionally Graded Structure
Authors: Sawada Kazuaki , Akiyama Masahiro , Takao Hidekuni , Ishida Makoto
Published: October 2002

An a-Si:H/a-SiC:H staircase photodiode with linearly graded gap
multiplication regions is a useful device for photoconversion
films. Photocurrent multiplication due to impact ionization was
observed in the hydrogenated amorphous silicon (a-Si:H)/hydrogenated
amorphous silicon carbide (a-SiC:H) staircase photodiode. In the
staircase photodiode with one band offset, the photocurrent was
multiplied twice and was saturated. In the staircase photodiode with
three band offsets, a saturated multiplication gain of about 6 was
obtained. The noise characteristics of the a-Si:H/a-SiC:H staircase
photodiode films with one and three linear graded-gap regions were
studied. The measured shot noise characteristics of the photodiode
film, which was operated in a photocurrent multiplication region,
corresponded to the ideal value, which was calculated as free excess
noise. It was determined that the shot noise of a-Si:H/a-SiC:H
staircase avalanche photodiode film was much less than that for the
conventional crystal silicon avalanche photodiode in the
photocurrent multiplication region. These results indicate that
staircase photodiode films are promising devices for highly
sensitive imaging sensors.
Effects of Strain on Highly Mismatched AlGaN/GaN Multiple Quantum Wells
Authors: Iizuka Norio , Suzuki Nobuo
Published: October 2002

Photoluminescence (PL) spectra, surface morphologies and
cross-sectional images of
transmission microscopy (TEM) were examined after changing the
thickness of barriers or wells in AlGaN/GaN multiple quantum
wells. When the wells are thin and the barriers are thick, multi quantum wells (MQWs) are
partially relaxed. This brings about changes in the electric field and
the band-gap of the wells. Thus, the PL spectrum becomes
broad. Although few cracks were observed, cross-sectional TEM images
indicated that the crystalline quality was poor. Even when the wells
are thin, however, the strain energy can be lowered by reducing the
barrier thickness. Thus, an improved PL spectrum can be obtained.
Investigation of Initial Growth Process of GaN Film on Sapphire Using Computational Chemistry
Authors: Onozu Takayuki , Inaba Yusaku , Takami Seiichi , Kubo Momoji , Miyamoto Akira , Iyechika Yasushi , Maeda Takayoshi
Published: October 2002

We have performed molecular dynamics (MD) simulations and periodic density
functional calculations to investigate the interatomic interactions of the GaN/sapphire
(0001) interface and the energetically stable site of GaN molecule on the sapphire
(0001) surface. The MD simulations indicate that the mobility of the Ga atoms is larger
than that of the N atoms on the sapphire (0001) surface, as the Al–N interaction is
stronger than the O–Ga interaction. The density functional calculations also suggest
that the formation of the Al–N bond is most energetically stable on the sapphire
(0001) surface. Since the sapphire (0001) substrate is terminated with Al atoms in the
reductive atmosphere, we assumed that the formation of Al–N bonds is dominant at
the GaN/sapphire (0001) interface.
Optical Recombination Processes in High-Quality GaN Films and InGaN Quantum Wells Grown on Facet-Initiated Epitaxial Lateral Overgrown GaN Substrates
Authors: Yamaguchi A. Atsushi , Mochizuki Yasunori , Mizuta Masashi
Published: October 2002

We have used time-resolved and temperature-dependent
photoluminescence (PL) measurements to study the recombination
mechanism in high-quality GaN films and InGaN quantum wells (QWs)
grown on facet-initiated epitaxial lateral overgrown (FIELO) GaN
substrates. We found that the nonradiative defect density in
FIELO-GaN films is much lower than that in GaN films grown on
sapphire substrates and that the emission efficiency of InGaN-QWs is
determined not only by the defect density but also by the indium
alloy fluctuation. We have proposed a model to evaluate these two
factors separately and have used it to show that both the defect
density and the alloy fluctuation in the QW films grown on FIELO
substrates are much less than those in QW films grown on sapphire
substrates.
Spatially Resolved Imaging of the Spectral Emission Characteristic of an InGaN/GaN-Multi Quantum Well- Light-Emitting Diode by Scanning Electroluminescence Microscopy
Authors: Fischer Peter , Christen Jürgen , Zacharias Margit , Schwegler Veit , Kirchner Christoph , Kamp Markus
Published: October 2002

The microscopic spectral emission characteristic of an InGaN/GaN
multi quantum well light-emitting diode is directly imaged by highly
spectrally- and spatially-resolved scanning electroluminescence
microscopy under operation as a function of injection current
density from both, contact and substrate side. The mono- and
panchromatic luminescence intensity maps and especially the
peak-wavelength scanning images provide access to the optical
quality of the final device and yield direct images of the In
fluctuations with 1 µm spatial resolution. Indium
concentrations varying from around 0.09 to 0.11 are found in the
active InGaN-region of the near ultraviolet diode emitting at
404 nm with a FWHM of 20 nm. At high current density a 4 nm
redshift of emission wavelength due to ohmic heating is
observed. Whereas the mesa electroluminescence intensity mapping of
the front side becomes uniform for higher current densities, the
backside electroluminescence still shows electroluminescence
intensity fluctuations.
Lattice-Relaxation Process of (InAs)m(GaAs)n Strained Short-Period Superlattices Grown on GaAs
Authors: Katsuya Samonji Katsuya Samonji , Hiroo Yonezu Hiroo Yonezu , Naoki Ohshima Naoki Ohshima
Published: October 2002

We investigated the lattice-relaxation process in the growth of an (InAs)1(GaAs)4 strained short-period superlattice (SSPS) on GaAs(100) substrates by X-ray diffraction (XRD) measurements and transmission electron microscopy (TEM). It was found that the lattice relaxation in the (InAs)1(GaAs)4 SSPS proceeded as rapidly as that in the In0.2Ga0.8As alloy layer. The percentage strain relaxation R
XRD, as estimated by XRD measurements, agreed with the calculation results based on the elasticity theory. However, the percentage strain relaxation R
TEM, as calculated by measurements of misfit dislocations at the heterointerfaces, was much lower than that estimated by the XRD measurements. It is believed that the difference between the values of R
XRD and R
TEM are attributable to the nonuniform distribution of strain energy along the growth direction.
Spectral Characteristics of Vertically Stacked Etched Multiple-Quantum-Wire Lasers Fabricated by Flow Rate Modulation Epitaxy
Authors: Kim Tae Geun , Wang Xue-Lun , Ogura Mutsuo
Published: October 2002

We report the spectral characteristics of AlGaAs–GaAs multiple-quantum-wire
(QWR) lasers fabricated by flow rate modulation epitaxy on V-grooved substrates.
Room-temperature lasing from the fundamental state (1e-1hh) is generally
observed in devices longer than 350 µm; however, secondary peaks at the
adjacent higher subbands are immediately detected following current injection. The
evolution of the stimulated emission spectra is investigated here. Typical threshold
current and the wavelength tuning rate of current are observed to be 6.2 mA and
0.012 nm/mA, respectively, for 800-µm-long uncoated cavities.
Correlation of Nanostructural Heterogeneity and Light Induced Degradation in a-Si:H Solar Cells
Authors: Das Ujjwal Kumar , Rath Jatindra Kumar , Williamson Don L. , Chaudhuri Partha
Published: October 2002

The small angle X-ray scattering (SAXS) method was adopted to estimate the
nanostructural heterogeneity in hydrogenated amorphous silicon (a-Si:H) materials
deposited by rf plasma enhanced chemical vapor deposition (PECVD) process from
silane-argon mixtures at different volume ratios. The performance of the solar cells
fabricated by using the same materials as the intrinsic layer has been correlated with
the integrated SAXS intensity of the intrinsic layer. The change in the density of states
due to light soaking has been measured in solar cell structure by a dual beam
photoconductivity method. We have observed a systematic increase in the photoinduced
degradation of the photoconductivity, defect density and the solar cell parameters with
the increase in the structural heterogeneities in the film. Modification of the growth
kinetics due to bombardment of the metastable argon (Ar*) has been found to
control the amount of nanostructural heterogeneity in the material.
Hetero Atomic-Layer Epitaxy of Ge on Si(100)
Authors: Motohiro Matsuyama Motohiro Matsuyama , Satoshi Sugahara Satoshi Sugahara , Keiji Ikeda Keiji Ikeda , Yasutaka Uchida Yasutaka Uchida , Masakiyo Matsumura Masakiyo Matsumura
Published: October 2002

Hetero atomic-layer epitaxy of Ge on the Si(100) surface has been successfully demonstrated. The Si underlayer was found to have strong influences on the adsorption kinetics of a Ge precursor, but a discrete increase in the grown-film thickness was achieved with a one-monolayer step up to the critical thickness of the Ge layer. The periodicity of vacancy lines in the grown Ge layer is shortened in pitch with increasing the number of Ge growth cycles, reconfirming that the Ge layer was grown in a layer-by-layer manner. C atoms were not introduced in the grown film when the growth temperature was about 420°C.
A Monte Carlo Study of Current–Voltage Characteristics of the Scaled-Down Single-Electron Transistor with a Silicon Rectangular Parallelepiped Quantum Dot
Authors: Kenji Natori Kenji Natori , Tsuyoshi Uehara Tsuyoshi Uehara , Nobuyuki Sano Nobuyuki Sano
Published: October 2002

The current-voltage characteristics of a silicon quantum-dot single-electron transistor are investigated by Monte Carlo simulation. A simple rectangular parallelepiped quantum dot is assumed and the current is computed by counting the sequential tunneling of electrons through the energy level of the dot. In contrast to known features of the classical single electron transistor, the obtained result shows a variety of current peak behaviors which are closely related to the energy level structure of the dot. In particular, a characteristic bell-shaped envelope of current peaks is observed in Coulomb oscillation when electrons are transmitted through multiply degenerate energy levels. The current–voltage characteristics of the quantum-dot single-electron transistor depend sensitively on the electronic structure of the dot, reflecting the geometry and the material of the device.
Lateral Silicon Field-Emission Devices using Electron Beam Lithography
Authors: Han Sangyeon , Yang Sun-a , Hwang Taekeun , Lee Jongho , Lee Jong Duk , Shin Hyungcheol
Published: October 2002

We fabricated field-emission vacuum microelectronic devices such
as diode and triode devices, using high-resolution electron-beam
lithography in combination with the reactive ion etching (RIE)
technique. The turn-on voltage of the diode is 13 V, which is the
lowest value reported for single-crystalline lateral silicon
field-emission devices. An emission current of 1.4 µA was
obtained at an anode bias of 40 V. Field emission was confirmed by
the linearity of the Fowler-Nordheim plots. The anode current of the
triode was effectively modulated as a function of gate voltage. The
device stability results show that the proposed devices are stable
and reproducible.