bluuebunny/crossref_metadata_2025 huggingface dataset:
Conspicuous Voltage Shift of D-E Hysteresis Loop and Asymmetric Depolarization in Pb-Based Ferroelectric Thin Films
Authors: Soichiro Okamura Soichiro Okamura , Shoiti Miyata Shoiti Miyata , Yoji Mizutani Yoji Mizutani , Takashi Nishida Takashi Nishida , Tadashi Shiosaki Tadashi Shiosaki
Published: October 2002

Polycrystalline Pb(Zr,Ti)O3 (PZT) thin films fabricated by a chemical solution deposition (CSD) process exhibited a conspicuous initial voltage shift in the D-E hysteresis loop toward the negative-bias field. It was concluded that the origin of the voltage shift was an internal bias field due to asymmetric space-charge distribution induced by the natural alignment of spontaneous polarization during the cooling process. The internal bias field also caused asymmetric depolarizaiton at the zero-bias field. In heteroepitaxial (Pb,La)TiO3 thin films, we observed a conspicuous voltage shift toward the positive-bias field and asymmetric depolarization at the zero-bias field. They were eliminated by the application of a positive unipolar pulse train.
Deep-Level Energy States in Nanostructural Porous Silicon
Authors: Matsumoto Takahiro , Mimura Hidenori , Koshida Nobuyoshi , Masumoto Yasuaki
Published: October 2002

The deep-level energy states in nanostructural porous silicon films, prepared by electrochemical anodization, were determined from the analysis of the current-voltage (J-V) characteristics in the space-charge-limited-current (SCLC) regime. The energy states show a minimum density at the Fermi level, which is similar to the U-shaped-trap-distribution observed in crystalline Si–SiO2 interface or in amorphous Si. The agreement between the experimental J-V characteristics and the theoretical curve strongly implies that the current flow is entirely controlled by localized states situated at the quasi-Fermi level.
Measurement of Piezoelectric Displacements of Pb(Zr, Ti)O3 Thin Films Using a Double-Beam Interferometer
Authors: Maiwa Hiroshi , Christman James A. , Kim Seung-Hyun , Kim Dong-Joo , Maria Jon-Paul , Chen Barry , Streiffer Stephen K. , Kingon Angus I.
Published: October 2002

The double-beam interferometric method is applied to measure the field-induced
displacement of Pb(Zr, Ti)O3 thin films. The dc electric field dependence of the
longitudinal piezoelectric coefficient (d
33) response of Pb(Zr, Ti)O3 thin films deposited
by metal organic chemical vapor deposition (MOCVD) was measured. Experimental d
33
values were compared with coefficients calculated using a phenomenological approach
and bulk parameters. Qualitative agreement was obtained between measured and
calculated coefficients.
Imprint Model Based on Thermionic Electron Emission Under Local Fields in Ferroelectric Thin Films
Authors: Nagasawa Dai , Nozawa Hiroshi
Published: October 2002

We investigated the origin of the imprint mechanism of
ferroelectric thin films such as PbZr
x
Ti1-x
O3 (PZT) or SrBi2Ta2O9
(SBT) by considering thermionic field emission under local
fields. The electric fields inside the ferroelectric films are
represented. Since the poled ferroelectric capacitors have strong
local field inside, the thermionic field emission rate is enhanced
by tunneling effect. The emission rate is estimated by taking the
thermionic field emission into account. The dependence of imprint
phenomenon on the emitted electrons from traps is explained in
detail. We calculate the voltage shift that results from the imprint
phenomenon. Comparing the results with the experiments, we
successfully explain the imprint phenomenon based on pinning.
Evolution of Ferroelectric Structure in SrBi2Ta2O9 Thin Films Prepared Using Triple Alkoxides on Pt-Passivated Si
Authors: Kato Kazumi
Published: October 2002

Crystallization of triple-alkoxy-derived SrBi2Ta2O9 (SBT) thin films was
initiated at temperatures below 500°C. For the 500°C-annealed thin films, the
vibration modes of the oxygen sublattice of the SBT perovskite crystal were confirmed
by Fourier-transform infrared spectroscopy (FT-IR) analysis. Calcination at 250°C in
a mixture of water vapor and oxygen flow followed by rapid thermal annealing in the
temperature range of 500–650°C affected the crystallinity and crystallographic
orientation of SBT thin films. For these films, the strong infrared bands mainly
corresponded to the dominant frequencies related to the optical polarization parallel to
the c-axis. Simultaneously, grains grew and the surface topography changed
significantly. The improvement of the crystallinity of the SBT perovskite phase and
the increase in the grain size were responsible for the ferroelectric hysteresis properties
in triple-alkoxy-derived SBT thin films annealed in the temperature
range of 600–650°C
Potential Modulation of Semiconductor Dot Array System due to Photoexcitation
Authors: Fujii Ken-ichi , Yoshizawa Takeshi , Ohyama Tyuzi , Oto Kenichi , Takaoka Sadao , Murase Kazuo , Gamo Kenji
Published: October 2002

Far-infrared magnetooptical absorption measurement of a quantum dot
array is carried out. In contrast to the starting two-dimensional
electron gas, the shift of the resonance peak of a dot array structure
can be clearly observed under pulsed photoexcitation.
From the delay time variation, change of the peak shift is quite
slow. This peak shift does not depend simply on the change in the
carrier concentration by photoexcitation. The photoexcited carrier
changes the charge states around the dot. The peak shift can be
interpreted by the potential modulation due to photoexcitation.
Effects of Ion Etching and Annealing in O2 Atmosphere Following Ion Etching on Properties and Chemistry of Sr0.9Bi2.1Ta2O9+a Thin Films
Authors: Asami Katsuhiko , Koiwa Ichiro , Yamanobe Tomomi
Published: October 2002

The effects of ion etching and effects of annealing in an
O2 atmosphere for 60 min at 800°C following ion
etching (reannealing) on the properties of
Sr0.9Bi2.1Ta2O9+a
(SBT) thin films for
ferroelectric memory were studied. The leakage current increased by
six orders of magnitude following Ar-ion etching, and it caused a
bulging out of the hysteresis loop. Electron probe micro analysis
(EPMA) results showed no significant change following the ion
etching, whereas X-ray photoelectron spectrometry (XPS) detected a large
decrease in the Bi concentration and increase in the
metallic Bi to oxidic Bi ratio. Following reannealing, the
electrical properties and surface compositions were restored. Thus,
the electrical properties were significantly affected by the
presence of metallic Bi together with a large composition deviation
in the surface region. It was concluded that ion etching of the SBT
thin films causes a reduction of oxidic Bi to metallic Bi and a
decrease in the total Bi concentration in the surface region
resulting in a high leakage current density, whereas annealing in an
O2 atmosphere is effective for restoring the initial low
leakage current density.
Lowering the Crystallization Temperature of YMnO3 Thin Films by the Sol-Gel Method Using an Yttrium Alkoxide
Authors: Kitahata Hiroya , Tadanaga Kiyoharu , Minami Tsutomu , Fujimura Norifumi , Ito Taichiro
Published: October 2002

We have succeeded in lowering the crystallization temperature of sol-gel derived YMnO3
thin films to 500°C by using yttrium alkoxide as a starting material. The X-ray diffraction
measurements indicated that the films heat treated at temperatures above 500°C had a single phase of
hexagonal YMnO3. The crystallization temperature of the YMnO3 thin film prepared from yttrium
alkoxide was lower by at least 300°C than that of film prepared from yttrium acetate. The film
prepared from the alkoxide and heat treated at 700°C for 3 min had a high crystallinity with c-axis
preferred orientation, and ferroelectricity was observed in the film. The formation temperature of
the ferroelectric YMnO3 thin film prepared from yttrium alkoxide was lower by at least 100°C than
that of film prepared from yttrium acetate.
Dielectric Properties of Solid Solutions (1-x)Pb(Sc1/2Ta1/2)O3–xPbZrO3 (0 < x < 1)
Authors: Yasuda Naohiko , Ohwa Hidehiro , Fujioka Eiji , Suzuki Sadafumi , Iwata Makoto , Ishibashi Yoshihiro
Published: October 2002

Dielectric properties of
(1-x)Pb(Sc1/2Ta1/2)O3(PST)–xPbZrO3 (PZ)
(0<x<1) were investigated. For PZ concentrations x<0.7, a diffuse
phase transition was observed. With increasing x, the maximum
permittivity ε
rm
′ increased, and the
temperature T
m at which ε
rm
′
appeared shifted towards the higher temperature region. For x>0.7,
the permittivity ε
r
′ exhibits a peak at
the phase transition temperature T
c. With increasing x,
the peak value decreased and T
t shifted towards the higher
temperature region. The phase below T
c was confirmed to be
ferroelectric by observation of P-E hysteresis loops. Phase
transformation from the relaxor to the ferroelectric state occurred at
x=0.7. For x>0.8, a steplike anomaly appeared at T
t
below T
c. With increasing x, T
t shifted
towards the higher temperature region. There was a structural change
characterized by the splitting of the structure-sensitive maximum of
the (200) reflection of XRD patterns, similar to orthorhombic PZ,
around x=0.8. Two morphotropic phase boundaries were found: one
between the pseudocubic and rhombohedral phases with
ε
rm
′ of 15000 at 100 kHz was at
x=0.7, and the other between the rhombohedral and orthorhombic
phases was at x=0.8.
Piezoelectric Properties of La-Doped PbTiO3 Films for RF Resonators
Authors: Yamada Akira , Maeda Chisako , Uchikawa Fusaoki , Misu Koichiro , Honma Toshihiko
Published: October 2002

Bulk acoustic wave (BAW) resonators with 5-wt%-La2O3-doped PbTiO3 (PT)
piezoelectric films were fabricated. The La-doped PT films had a dense,
homogeneous morphology, as well as high crystallinity caused by the use of bottom
electrodes with pure Pt-like surface layers. These PT films had remanent polarization
of 110 mC/m2 at 200°C. Resonant frequencies of the fabricated devices were 1.4 GHz and 2.0 GHz. The electromechanical coupling coefficient (k

t

2) was estimated to
be 11% at 1.4 GHz and 9.4% at 2.0 GHz, respectively. The PT films had superior k

t

2 in
the GHz band. The capability of the RF devices with broad bandwidth was
investigated.
Phase Formation and Field-Induced Strain Properties in Y-Modified Lead Zirconate Stannate Titanate Ceramics
Authors: Hyun Yoon Yun-Woo Nam
Published: October 2002

The phase formation and field-induced strain properties of the Pb0.97Y0.02[(Zr0.6Sn0.4)1-y
Ti
y
]O3 ceramics have been investigated as a function of Ti4+ content (0.08 ≤y ≤0.09). With increasing Ti4+ content, the specimens showed a structural transition from the orthorhombic to the rhombohedral phase. The specimen of y=0.08 represented a double hysteresis loop, while the specimen of y=0.09 represented a single hysteresis loop. The strain of digital-type shape was observed in the specimens of y=0.08 and y=0.085. The strain at the shape memory state was about 2.8 ×10-3 in the specimens of y=0.085.
Piezoelectric Properties of Bismuth Layer-Structured Ferroelectric Ceramics with a Preferred Orientation Processed by the Reactive Templated Grain Growth Method
Authors: Takeuchi Tsuguto , Tani Toshihiko , Saito Yasuyoshi
Published: October 2002

Dense CaBi4Ti4O15 (CBT) and Na0.475Ca0.05Bi4.475Ti4O15 (NCBT) ceramics with a highly
preferred {001} orientation were prepared by the reactive templated grain growth (RTGG)
method. Plate-like Bi4Ti3O12 (BIT) particles were synthesized by a molten salt technique and
used as the reactive template. The template particles were mixed with other oxide and carbonate
powders and aligned by tape-casting. During the sintering, oriented CBT and NCBT were
formed in situ topotaxially on the oriented BIT particles, and textured CBT and NCBT ceramics
were eventually fabricated by the templated grain growth and densification. The Lotgering
{001} orientation degree of the textured ceramics exceeded 90% for secondary-laminate
sintered specimens. Textured CBT and NCBT ceramics poled in the perpendicular direction to
the preferred <001> axis exhibited electromechanical coupling coefficient (k
33) and
piezoelectric coefficients (d
33 and g
33) three times higher than the values for nontextured
ceramics with the same composition.
Photoluminescence Study of High-Quality InGaAs/GaAs Quantum Dots on (111)B GaAs Substrates
Authors: Tsai Fu-Yi , Lee Chien-Ping
Published: October 2002

We present a simple in situ method to fabricate high-quality InGaAs/GaAs quantum dots on (111)B GaAs substrates. The mechanism of the quantum dot formation is not strain relaxation but the growth characteristic of (111)B GaAs under low substrate temperatures. When the growth is performed at low temperatures, the layer-by-layer growth mode is replaced by island growth and therefore quantum dots are formed. The formation of the quantum dots was verified by atomic force microscope (AFM) images and the shift of photoluminescence (PL). The PL emission from the quantum dots was very strong and the full-width at half-maximum (FWHM) of the emission peak was as small as 7.7 meV, indicating excellent quality and very uniform dot formation. The effect of nominal thickness on the quantum dot formation has been investigated.
Microwave Dielectric Properties of Sm2Ba(Cu1-xZnx)O5(x=0 to 1) Solid Solutions
Authors: Kan Akinori , Ogawa Hirotaka , Watanabe Masahiro , Hatanaka Shigeru , Ohsato Hitoshi
Published: October 2002

Sm2Ba(Cu1-x
Zn
x
)O5 solid solutions with composition x ranging from 0 to 1 were prepared by the
solid-state reaction method. The microwave dielectric properties of the solid solutions obtained in
this study were as follows: the dielectric constants (ε

r
) range from 13 to 20, and the temperature
coefficient of the resonant frequency (τ
f
) and the
quality factor (Q·f) value are -9 to -4 (ppm/°C) and 3000 to 66000 (GHz), respectively. Moreover, it was evaluated that the τ
f
and the Q·f values
obtained in this work are extremely improved by
(Y2-y
Sm
y
)BaCuO5 (y=0 to 1) and Y2Ba(Cu1-x
Zn
x
)O5
solid solutions, respectively. It was also clarified that the variations in the atomic distances in the
Sm2O11 polyhedron and the strain of the polyhedron exerted an influence on the temperature
coefficient of the dielectric constant (τ
ε
) and the Q·f value, respectively.
Electrooptical Properties of Heterostructure (Pb, La)(Zr, Ti)O3 Waveguides on Nb–SrTiO3
Authors: Nashimoto Keiichi , Nakamura Shigetoshi , Morikawa Takashi , Moriyama Hiroaki , Watanabe Masao , Osakabe Eisuke
Published: October 2002

The electrooptic behavior of (Pb, La)(Zr, Ti)O3 (PLZT) heterostructure waveguides, including PLZT/Pb(Zr0.95Ti0.05)O3 [PZT (95/5)] and Pb(Zr0.52Ti0.48)O3 [PZT (52/48)]/Pb(Zr0.85Ti0.15)O3 [PZT (85/15)] on Nb–ST substrates was examined. Electrooptic behavior was characterized by
fabricating beam deflectors using these heterostructures. The heterostructure waveguides
exhibited hysteresis-free electrooptic behavior after the application of initial voltage. The
electrooptic behavior of PLZT/PZT (95/5) and PZT (52/48)/PZT (85/15) heterostructure
waveguides presented a nonlinear dependence and a linear dependence, respectively. The
apparent electrooptic coefficient of the PLZT/PZT (95/5) heterostructure obtained from the linear
part of the V–θ characteristic above +7.5 V was 53 pm/V, and that of the PZT (52/48)/PZT
(85/15) heterostructure was 37 pm/V. The electrooptic coefficient of the PZT (52/48)
waveguide layer using an effective voltage was estimated to be 53 pm/V.
Ti–O Hybridization Effect on Ferroelectric Phase Transition of BaTiO3
Authors: Higuchi Tohru , Tsukamoto Takeyo , Oka Kunihiko , Yokoya Takayoshi , Tezuka Yasuhisa , Shin Shik
Published: October 2002

The Ti-O hybridization effect on the ferroelectric phase transition of BaTiO3 has been
studied by resonant-photoemission spectroscopy. The Ti 3d partial-density-of-state in the
valence band of the paraelectric phase is larger than that of the ferroelectric phase. This fact
indicates that the Ti–O hybridization effect is stronger in the paraelectric phase.
Stability of Antiferroelectric and Ferroelectric Phases in Low Ti Concentration PbZr1-xTixO3
Authors: Kojima Seiji , Ohta Naomi , Dong Xianlin
Published: October 2002

The structural phase transitions of low Ti concentration 1 wt% Nb-doped PbZr1-xTixO3(0.015\leqslantx\leqslant0.030) were studied by Raman scattering spectroscopy and dielectric measurement in the temperature range from -170°C to 300°C. The rhombohedral low-temperature ferroelectricFR(LT) phase, the rhombohedral high-temperature ferroelectricFR(HT) phase and the antiferroelectric orthorhombicAOphases are more distinguishable by Raman spectra in comparison to the spectra of antiferroelectric pure PbZrO3and ferroelectric PZT wherex=0.05, as reported previously. The phase boundary of antiferroelectric orthorhombic and ferroelectric rhombohedral phases exists at the Ti content ofx=0.025, where the bistability of two phases is observed. At this critical composition, both phases appear separate with different temperature treatments. The Curie temperature decreases asxdecreases. Forx> 0.025,FR(LT) toFR(HT) transition temperature decreases asxdecreases, and its thermal hysteresis is about a few degrees. Forx< 0.025,AOtoFR(HT) transition temperature increases asxdecreases, and its thermal hysteresis is several tens degrees. AboveTc, the intense quasi-elastic scattering appears atx=0.03, it becomes weak asxdecreases. This suggests that the origin of the quasi-elastic scattering might be that the nano-size polar clusters are induced by low concentrarion Ti ions.
Persistent Spectral-Hole-Burning in Semiconductor Quantum Dots and its Application to Spectroscopy
Authors: Masumoto Yasuaki
Published: October 2002

Persistent spectral-hole-burning (PSHB) phenomena have been observed in many kinds of
semiconductor quantum dots (QDs). Luminescence hole burning and charged excitons have been
observed in CuCl QDs in NaCl crystals. The observed PSHB phenomena are explained by the ionization
of QDs. The energy of photoionized QDs is changed from the original energy and their new energies
depend on the spatial arrangement of trapped carriers. Quantum confinement of carriers and the
resulting strong Coulomb interaction between confined carriers and trapped carriers cause the energy
change. PSHB has been widely applied to site-selective spectroscopy of QDs. Size-dependent excited
exciton quantum states in CuCl quantum cubes, size-dependent excited electron-hole quantum states in
CdTe QDs and renormalization of longitudinal optical phonons confined in CuCl QDs have been
revealed by studying sideband holes. This also allowed the measurement of accumulated photon echo,
which clarified the very sharp homogeneous spectral linewidth of QDs under weak excitation conditions.
Two-Dimensionally Position-Controlled Excimer-Laser-Crystallization of Silicon Thin Films on Glassy Substrate
Authors: Motohiro Ozawa Motohiro Ozawa , Chang-Ho Oh Chang-Ho Oh , Masakiyo Matsumura Masakiyo Matsumura
Published: October 2002

Nucleus positions have been two-dimensionally controlled in excimer-laser-crystallized Si thin-films on a glassy substrate. The position along one direction on the surface was controlled by intensity gradient of the excimer-laser light. The position control along the other direction was achieved by pre-patterning of the Si thin film as fine line structures and by heating the space between the lines with a light absorption layer. SiON was suitable as an absorption layer for KrF excimer-laser light. The grains grown were as long as 7 mm, even for ultra-thin (50-nm-thick) Si films.
Transport Coefficients of Indium Antimonide in a Magnetic Field
Authors: Hiroaki Nakamura Hiroaki Nakamura , Kazuaki Ikeda Kazuaki Ikeda , Satarou Yamaguchi Satarou Yamaguchi
Published: October 2002

Transport coefficients of indium antimonide in the presence of a temperature gradient and magnetic field were calculated numerically using the charge neutrality for a parabolic two-band model in classical statistics. Comparing theoretical with experimental results up to 4 T, the theoretical results are almost coincident with the experimental values except for the Nernst coefficient below 0.1 T. We assume that the parabolic two-band model is a criterion for estimating the power factor of the Nernst element.
Comparison of Microstructure and Crystal Structure of Polycrystalline Silicon Exhibiting Varied Textures Fabricated by Microwave and Very High Frequency Plasma Enhanced Chemical Vapor Deposition and Their Transport Properties
Authors: Kamiya Toshio , Nakahata Kouichi , Ro Kazuyoshi , Fortmann Charles M. , Shimizu Isamu
Published: October 2002

Micro- and crystal structures of polycrystalline silicon
(poly-Si) films fabricated by low temperature
(≤360°C) plasma enhanced chemical vapor
deposition (PECVD) were examined. Crystal orientation could be
controlled by varying the source gas ratio SiF4/H2. (220)
oriented films were obtained at low gas flow rate ratios while (400)
preferentially oriented films were obtained at higher
SiF4/H2 ratios either by a remote-type microwave PECVD or a
capacitive coupled parallel electrode very high frequency (VHF)
PECVD. It was found that micro- and crystal structures were a strong
function of orientation; that is, the crystal lattice in the (220)
oriented film was under tensile strain and the crystalline grain had
strong anisotropy of grain size. In contrast, the crystal lattice in
the (400) oriented film was under compressive strain and evident
anisotropy in the grain size could not be found. Furthermore, it was
confirmed that the deposition of SiH
n
and/or
SiH
n
F
m
and etching by fluorinated species and their
competition played an important role in the selective
growth. Fluorine-related species were also effective in growing large
crystalline grains. Hall mobility of electron for (400) oriented films
showed a monotonic increase with carrier density and achieved a large
mobility of ∼10 cm2/Vs.
Role of Seed Crystal Layer in Two-Step-Growth Procedure for Low Temperature Growth of Polycrystalline Silicon Thin Film from SiF4 by a Remote-Type Microwave Plasma Enhanced Chemical Vapor Deposition
Authors: Kamiya Toshio , Ro Kazuyoshi , Fortmann Charles M. , Shimizu Isamu
Published: October 2002

Role of seed crystal layer which played in low temperature
growth of polycrystalline silicon (poly-Si) thin films was
investigated by two-step-growth (TSG) process. The TSG involves two
different deposition processes, which are called as `seed process' and
`growth process'. In order to satisfy the conflicting demands such as
low temperature, high rate and high quality crystal growth, the
deposition conditions in the seed and growth processes were
examined. As a result, it is confirmed that the seeding of high
quality crystal layer is effective to improve crystallinity of growing
poly-Si film, especially for the case grown at lower temperature than
300°C. In order to fully promote crystallinity, some thick
and high crystallinity seed layer is needed. In addition,
epitaxial-like growth on the seed layers can be realized by optimizing
deposition conditions both during the seed and growth processes. When
H2/SiF4 flow ratios larger than those used during the seed
process were used during the growth process, lower growth temperatures
were possible with maintaining a smooth interface between the seed and
the grown poly-Si layers. In essence, the hydrogen mixing
ratio and deposition temperature are complementary parameters, thus it
was possible to reduce deposition temperatures with maintaining large
crystal fraction and oriented structure, if the hydrogen mixing ratio
was increased to an appropriate amount. Furthermore, in situ
ellipsometry analysis indicated that, under optimal conditions, the
interface between the seed and the growing film can indeed be smooth
and epitaxial-like. TSG is a promising technique by which to fabricate
high quality poly-Si thin films on glass substrates at low
temperatures.
Boron Vapour Phase Doping of Silicon for Bipolar Device Applications
Authors: Theunissen M. J. J. , Timmering C. E. , Berkum J. G. van , Mergler Y. J.
Published: October 2002

Boron vapour-phase doping (VPD) has been investigated as a possible processing tool for defect-free applications in shallow, vertical and deep junctions in devices. From literature and experiments it has become clear that silicon boride (SiB3) layers can form during VPD. Thermodynamical calculations and analytical techniques were used to establish boride-free doping conditions. SiB3 formation and decomposition have been investigated as a function of temperature, time and the presence of O-containing compounds in the gas system. The hydrogen anneal after boron VPD not only decomposes boride layers on the Si surface, but it is also a means to control dose and depth of a boron junction. Boride-enhanced boron diffusion with buried SiB3 layers has been demonstrated. Effects of patterned Si windows in masking layers and polycrystalline Si layers on the VPD process are described. Application of the boron VPD technique to make a p-type base in bipolar npn transistors shows excellent device and high-frequency characteristics.
Crystallographic Structures and Parasitic Resistances of Self-Aligned Silicide TiSi2/Self-Aligned Nitrided Barrier Layer/Selective Chemical Vapor Deposited Aluminum in Fully Self-Aligned Metallization Metal Oxide Semiconductor Field-Effect Transistor
Authors: Lee Chang-Hun , Nishimura Takamasa , Matsuhashi Hideki , Yokoyama Michio , Masu Kazuya , Tsubouchi Kazuo
Published: October 2002

In deep submicron metal oxide semiconductor field-effect transistor (MOSFET) structures,
parasitic resistances of source/drain and gate (S/D&G) regions limit device performance. For
the reduction of parasitic resistances, we have previously proposed a fully self-aligned
metallization (FSAM) MOSFET using selective aluminum chemical vapor deposition (Al CVD)
technology. The features of FSAM-MOSFET are (1) self-aligned silicide (SALICIDE) for low
TiSi2/n+-Si contact resistances in S/D regions, (2) self-aligned barrier layer on TiSi2 surface, and
(3) selective Al deposition on S/D&G regions for low sheet
resistances. In this study,
crystallographic structures and parasitic resistances of SALICIDE TiSi2/self-aligned nitrided
barrier layer/selective CVD Al structures have been investigated. It has been experimentally
confirmed that (1) C49-TiSi2/n+-Si has lower contact resistance than C54-TiSi2/n+-Si, (2) the 10 nm amorphous Ti–Si–N barrier layer has stable thermal endurance and does not increase the
contact resistances, and (3) the selective CVD Al layer reduces the sheet resistances of the S/D.
Therefore, the combination of SALICIDE TiSi2, self-aligned barrier layer and selective CVD Al
is promising for the low-temperature FSAM-MOSFET process.
Electromagnetic Calculations of the Near Field of a Tip under Polarized Laser Irradiation
Authors: Lu Yong-Feng , Mai Zhi-Hong , Chim Wai-Kin
Published: October 2002

A general model of the near field emission for a tip under
polarized laser irradiation is established for the case of imaging and
processing by a laser-assisted scanning probe microscope (SPM). The
near field emission of an actual SPM tip was calculated using the
method of moment. The tip-sample geometry was modelled as a cone
approaching a surface at the tip apex. Laser-induced current modes in
the tip and sample were established in the form of trigonometric
functions. This model can be used for rigorous calculations and has
been applied to investigate the dependence of the near field on laser
wavelength, tip aspect ratios, tip-sample distance and the dielectric
properties of both tip and sample.
A Detailed Investigation of the Polarization-Dependent Surface-Relief-Grating Formation Process on Azo Polymer Films
Authors: Viswanathan Nirmal K. , Balasubramanian Srinivasan , Li Lian , Tripathy Sukant K. , Kumar Jayant
Published: October 2002

We have carried out two-beam interference experiments to form
surface-relief gratings (SRGs) on azo polymer films under different
polarization combinations. The mechanism of SRG formation on
azobenzene chromophore functionalized polymer films has been shown to
depend on both the spatial variation of the intensity as well as the
polarization state of the incident field pattern. The treatment
presented in this paper clearly defines the intensity and polarization
distribution across the two-beam interference region for different
polarization configurations of the interfering beams. The efficient
photoisomerization process due to the spatial variation of the optical
field renders the material anisotropic and the surface mobile. The
simultaneous presence of a component of electric field gradient in the
grating vector direction results in large-modulation-depth SRGs. We
have carried out this investigation in one class of prototypical
amorphous epoxy-based azo polymer thin films. Our results confirm that
efficient SRG formation on azo functionalized polymer film requires
photoinduced anisotropy and a component of optical field gradient in
the direction of the grating vector.
Ferroelectric Signal Frequency Dividers
Authors: Tae Song David J. Jefferies
Published: October 2002

The nonlinear capacitance of a ferroelectric is used to down-convert modulated signals by carrier frequency division. The modulations are largely preserved.
Photoinduced Charge Separation and Photocurrent in Multilayered Conducting Polymer Heterostructure by Self-Assembly Method
Authors: Yamaue Takahiro , Kawai Tsuyoshi , Onoda Mitsuyoshi , Yoshino Katsumi
Published: October 2002

Multilayered heterostructures composed of negatively and positively charged conducting polymers have been fabricated by the self-assembly method, and their optical properties and photoconduction have been studied. Remarkable quenching of photoluminescence and enhanced photoconduction are found in the multilayered heterostructure. These phenomena are explained in terms of the efficient photoinduced charge separation at the heterointerfaces between the negatively and positively charged conducting polymers which are thought to act as photodonor and photoacceptor, respectively.
Self-Assembly Process of Alkanethiol Monolayers
Authors: Hideyuki Ogawa Hideyuki Ogawa , Takumi Takamura Takumi Takamura , Yuhei Shimoyama Yuhei Shimoyama
Published: October 2002

To reveal formation of self-assembled monolayers (SAM), we analyzed the molecular orientation of SAMs of alkanethiol and the molecular organization in the Langmuir-Blodgett (LB) and vacuum deposited (VD) films by Fourier-transform infrared reflection absorption spectroscopy (FT-IR-RAS) and X-ray diffraction (XRD). XRD of the LB films suggests that alkanethiol orients normal to a gold substrate. Alkanethiol in the VD films tilts with a larger angle on the gold than on the glass substrates. The FT-IR-RAS spectra revealed that the molecular organization in the SAM on the gold (111) surface is dependent on the immersion time. Alkanethiol in the SAM aligns normal to the substrate, when the molecule undergoes close packing. A stable SAM embedded in a well-ordered monolayer is controlled by the intermolecular interaction of alkanethiol as well as the interaction between sulfur and gold.
Change in the Layered Structure of Merocyanine Dye Langmuir-Blodgett Films due to N-Octadecane Addition
Authors: Hirano Yoshiaki , Kamata Kunihiko N. , Inadzuki Yudzou S. , Kawata Jun-ichi , Miura Yasuhiro F. , Sugi Michio , Ishii Toshio
Published: October 2002

The layered structure in Langmuir-Blodgett (LB) films of the merocyanine dye (MS)-arachidic acid (C20) binary system and the MS–C20-n-octadecane (AL18) ternary system with low and high C20 contents ([MS]: [C20]:[AL18]=1: 2: x and 1: 5: x, 0≦x≦5.0) has been studied by means of surface pressure (π)–area (A) isotherm and X-ray diffraction measurements. The π–A isotherm measurement indicates that AL18 tends to fill the empty space of MS; however, a certain amount of AL18 is found outside of the space of MS even for smaller mixing ratios of AL18. A phase transition is observed in the π–A isotherms of the ternary monolayers with low and high C20 contents for x≧3.0. Two different regimes can be recognized in the X-ray diffraction patterns of the LB films with low and high C20 contents: 2θ< 9° and 9° < 2θ. The bilayer unit-cell species governing the X-ray diffraction patterns for 2θ<9° changes with increasing molar mixing ratio of C20. X-ray diffraction and π–A isotherm measurements indicate that the increase in AL18 in the empty space of MS causes the expansion of the spacing estimated for 2θ< 9° in the LB films.
Electrical Conduction Mechanism of Al Contacts and Undoped Polycrystalline Diamond Films
Authors: Huang Bohr-Ran , Wu Chia-Haur
Published: October 2002

Polycrystalline diamond films were deposited using a
methane/hydrogen gas mixture in a microwave plasma-assisted chemical
vapor deposition system. In this research, a conduction mechanism was
successfully established for the Al/undoped diamond structure in the
temperature range of 30–300°C. It was found that the
rectifying properties of the Al/undoped diamond structure at room
temperature exhibited more ohmic behavior at high temperatures. It was
suggested that the oxidation layer in the metal/diamond interface was
degraded, and more currents flowed through the bulk diamond
crystallites and the diamond grain boundaries after the
high-temperature measuring process. It was suggested that a Schottky
contact was also formed in the diamond grain boundaries. The modified
equivalent circuit for the Al/undoped diamond structure is an ideal
Schottky diode in series with the bulk resistance for the bulk diamond
crystallites, which is also parallel to an opposite pole of the ideal
Schottky diode in series with the grain boundary resistance for the
diamond grain boundaries. Both the space-charge-limited transport
mechanism and the field-activated transport mechanism were considered
for the Al/undoped diamond structure. It was found that the field-activated
transport mechanism, in which the series resistance can be
represented by the Frenkel-Poole equation, had a better fit to the
experimental data.
Microstructural Observation of Boron Nitride Films Synthesized by Ion Implantation
Authors: Hu Cheng , Kotake Shigeo , Suzuki Yasuyuki , Senoo Masafumi
Published: October 2002

We report on the synthesis of boron nitride (BN) films by ion implantation and demonstrate
the results of microstructural observation of the films. Boron films
were initially prepared on single-crystal Si(100) substrates by rf
sputtering. Then, 30 keV N2
+ was implanted at doses ranging from
1×1017 ions/cm2 to 6×
1017 ions/cm2 to synthesize BN. No substrate heating was used in the sputtering and implantation
processes. Chemical composition analysis of the films was carried out
by Auger electron spectroscopy. Transmission electron microscopy was
employed for microstructural observation. Mixed-phase BN, including
t-BN, c-BN, w-BN and B25N, was identified in the implanted films. The
BN formation mechanism was discussed and compared with theoretical
models. The results of this work are consistent with the
stress-induced BN formation model in several aspects.
Dynamic Range of Optical Reflectometry with Spectral Interferometry
Authors: Mitsui Takahisa
Published: October 2002

I present an optical reflectometry (OR) technique with spectral interferometry (SIOR) that realizes high dynamic range compared with a conventional OR system using the delayed heterodyne technique (DHOR), and report on the application of this system to noninvasive in vivo measurements of the structure of the skin and the nail of an index finger. The theoretically derived dynamic range of SIOR is m/4-times superior to that of DHOR, where m is the number of independent image pixels. A dynamic range of 105 db was experimentally realized, which is comparable to the theoretically expected dynamic range of 112 db.
Recombination Activity in Directly Bonded High Resistivity Silicon Wafers Measured by the Photoconductance Decay Method
Authors: Sarrabayrouse Gérard , Lecerf Pascal , Bielle-Daspet Danielle
Published: October 2002

Characterisation of bonded high-resistivity silicon wafers by
the microwave photoconductance decay (µPCD) technique has been
performed. Bonding is shown to drastically alter the bulk
recombination activity of the wafers. The technique allows to separate
between bulk and interface recombination and appears as a powerful
tool to evaluate the quality of the bonded interface.
Effects of Crystal Originated Particles on Breakdown Characteristics of Ultra Thin Gate Oxide
Authors: Cho Won-ju , Lee Kyo-sung , Cha Young-kuk , Park Chang-woo , Shim Hyun-suk , Kim Young-cheol , Kuwano Hiroshi
Published: October 2002

The effects of crystal originated particles (COPs) on the ultra
thin gate oxide for recent ultra large-scale integration (ULSI)
devices have been studied. Various types of Czochralski (CZ) silicon
wafers were prepared by control the pulling speed of silicon ingot to
clarify the relationships between COPs and breakdown characteristics
of the ultra thin gate oxide. The distribution of COPs, measured by
optical shallow defect analyzer and particle counter, was compared
with the results of time zero dielectric breakdown (TZDB), time
dependent dielectric breakdown (TDDB) and stress induced leakage
current (SILC) for gate oxides with the thickness of 4.5–10 nm. As a
result, it was found that the effect of COPs is not a major factor for
the degradation of ultra thin gate oxide in recent ULSI devices.
Diffusion Control of Dopant from Heavily Se Doped n Type GaAs Layers Grown by Molecular Layer Epitaxy
Authors: Nishizawa Jun-ichi , Kurabayashi Toru
Published: October 2002

Properties of GaAs grown by molecular layer epitaxy are strongly influenced by surface
stoichiometry during growth. In molecular layer epitaxy, Se is introduced for the heavily
doped n
++ layers for device applications. In such layers, Se exists as an interstitial atom and
behaves as a diffusion source. In the growth process, the diffusion of doped Se into GaAs is
affected by the supply pressure of AsH3; a higher amount of AsH3 supplied during the
growth of the undoped layer in an n
++-i structure reduces the diffusion of Se. A lower
amount of AsH3 supplied during the growth of the n
++ layer reduces the diffusion of Se
from the n
++ layer to the i layer. The stoichiometry in i and n
++ layers affects the diffusion
of interstitial Se in different manners.
Theoretical Studies on Hole Transport and the Effective Hall Factor in Cubic Phase of p-Type GaN
Authors: Yasuhiko Hayashi Yasuhiko Hayashi , Keisuke Watanabe Keisuke Watanabe , Takashi Jimbo Takashi Jimbo , Masayoshi Umeno Masayoshi Umeno
Published: October 2002

The theoretical hole transport characteristics (Hall and drift
mobilities, and effective Hall factor) are reported for the cubic
phase of p-type GaN. These characteristics are calculated
using the “relaxation time approximation” as a function of
temperature. The calculations show that the dominant lattice
scattering mechanism for holes is the acoustic deformation
potential. In the calculation of the scattering rate for ionized
impurity mechanism, the activation energy of 120 or 250 meV is used at
different compensation ratios of given acceptor
concentrations. Comparing the scattering time in these activation
energies, it is found that the activation energy difference is
negligible at high compensation ratios. We determined the anisotropy
factors separately, due to the anisotropy of the energy surface for
heavy- and light-hole bands, and these parameters are taken into
account in the Hall factor calculations. The Hall factors are very
important when we attempt to compare the calculated drift mobility
with measured Hall ones. The theoretical Hall mobilities at total hole
concentrations of 3.5 ×1015 and 3.5 ×1016 cm-3
are about 312 and 225 cm2V-1s-1, respectively,
with the activation energy of 120 meV and the compensation ratio of
0.5 at 300 K. It is found that Hall mobilities are strongly affected
by the compensation ratios. The obtained effective Hall factor in the
cubic phase of GaN is in the range of 1.4 (T=120 K) to 1.8
(T=400 K).
Investigation of Low Loss and High Reliability Encapsulation Technology in Large-Area, High-Power Semiconductor Devices
Authors: Morita Toshiaki , Kato Mitsuo , Onuki Jin , Onose Hidekatsu , Matsuura Nobuyoshi , Sakurada Shuroku
Published: October 2002

In order to realize uniform and low contact resistance in the low mounting force region for large-area, high-power semiconductor devices, the effects of hardness and surface cleanliness of metal sheets inserted between an Al cathode and Mo internal electrode on the contact resistance were investigated as a function of mounting force. Contact resistance was lowered with increasing cleanliness and decreasing hardness of the inserted sheet for all values of the mounting force. A new process was developed in which an Ag-plated Mo sheet is heat-treated at 573 K for 15 min in air. It was confirmed that devices with the new Ag-plated Mo sheet have efficient long form reliability. The contact resistance and its dependence on the mounting force of the devices using this sheet are of the same level as those of an Ag-sputtered Mo sheet and an Ag sheet.
Probe Anode as a Characterization Tool for Field Emission Arrays
Authors: Nicolaescu D. , Filip V. , Itoh Junji , Kleps I.
Published: October 2002

A method of characterization for arrays of vertical field
emitters, which makes use of an anode of micron-sized dimensions, is
presented. Modeling results reveal that the emission current for probe
anodes varies in a similar way as for large dimension
anodes. Practical rules are derived for the correct interpretation of
the experimental data.
Strain Effect on the Band Structure of InAs/GaAs Quantum Dots
Authors: Zhu Haijun , Feng Songlin , Jiang Desheng , Deng Yuanming , Wang Hailong
Published: October 2002

The strain effect on the band structure of InAs/GaAs quantum dots has been investigated. 1 µm thick InGaAs cap layer was added onto the InAs quantum dot layer to modify the strain in the quantum dots. The exciton energies of InAs quantum dots before and after the relaxation of the cap layer were determined by photoluminescence. When the epilayer was lifted off from the substrate by etching away the sacrifice layer (AlAs) by HF solution, the energy of exciton in the quantum dots decreases due to band gap narrowing resulted from the strain relaxation. This method can be used to obtain much longer emission wavelength from InAs quantum dots.
Fabrication of Surface Relief Grating with Second-Order Nonlinearity Using Urethane-Urea Copolymer Films
Authors: Che Yanlong , Sugihara Okihiro , Egami Chikara , Fujimura Hisashi , Kawata Yoshimasa , Okamoto Naomichi , Tsuchimori Masaaki , Watanabe Osamu
Published: October 2002

Surface relief gratings on azobenzene-substituted urethane-urea
copolymer films with large second-order nonlinearity are fabricated by
a laser-interferometric method. The surface relief structures are
obtained upon exposure to an interference pattern of a polarized
Ar+ laser beam, which mainly results from photoablation. The
gratings are thermally stable at temperatures higher than glass
transition temperature (T
g) of the copolymer. The surface
relief gratings with second-order nonlinearity are fabricated after a
corona poling process. We report what we believe to be the first
experimental observation of the separated second-harmonic generation
from the fundamental wave by the surface relief grating with
second-order nonlinearity.
Analysis of the Laser Action of a Solid-State Dye Laser with a Thin Film Ring Resonator
Authors: Fukuda Makoto , Takeshita Kiyokazu , Mito Keiichi
Published: October 2002

This paper presents the fabrication of a compact blue
solid-state dye laser and the properties of the laser action based on
both experiment and numerical calculation. We solidified Stilbene-3
dye as the active medium for the laser by the sol-gel method and
coated the medium around a 3-mm diameter glass rod. We used the glass
rod simultaneously as a thin film ring resonator and a light
amplifier. We pumped the dye molecules with pulsed Nd:YAG laser
third-harmonic generation (355-nm wavelength) and obtained blue laser
emission; the center wavelength of the laser output was 433 nm. We
also designed a model of the thin film ring laser and simulated a
performance of the laser. Because of the agreement between the
calculated and experimental results, the validity of the model was
assured.
Tunable, UV Solid-State Lidar for Measurement of Nitric Oxide Distribution
Authors: Toriumi Ryoichi , Tai Hideo , Kuze Hiroaki , Takeuchi Nobuo
Published: October 2002

A solid-state differential absorption lidar (DIAL) system was developed for nitric oxide monitoring. The ultraviolet (UV) light was generated through second-harmonic generation, subsequent to the sum-frequency mixing of the pulses from a Ti:sapphire laser, pumped by a frequency-doubled Nd:YAG laser, and from the fundamental of another
Nd:YAG laser. The output pulse energy achieved in this way was 4 mJ at 226.8 nm with 2 pm linewidth. This DIAL system made it possible to measure the spatial distribution of nitric oxide emitted from a diesel engine installed at a distance of 130 m from the lidar for demonstration of stack plume, with the detection accuracy of 0.065 ppm with a range resolution of 10 m. We also measured the background nitric oxide of the order of 10 ppb in the urban atmosphere.
New Optical Logic Gates using Liquid Crystal Optical Diodes
Authors: Taiju Takahashi Taiju Takahashi , Hirokazu Furue Hirokazu Furue , Tomohiro Miyama Tomohiro Miyama , Tomo-o Yamashita Tomo-o Yamashita , Shunsuke Kobayashi Shunsuke Kobayashi
Published: October 2002

New optical logic gates have been fabricated by stacking two ferroelectric liquid crystal optical diodes (LC-ODs) fabricated by polymer stabilization. The device exhibits a strong asymmetric electrooptic performance; for this reason, the device is referred to as a liquid crystal optical diode. The liquid crystal logic gates fabricated by stacking two LC-ODs are shown to enable the performance of logic calculations, such as AND, NAND, OR, XOR, and XNOR.
A New Red-Emitting Phosphor, SrTiO3:Pr3+, for Low-Voltage Electron Excitation
Authors: Itoh Shigeo , Toki Hitoshi , Tamura Kiyoshi , Kataoka Fumiaki
Published: October 2002

A new red phosphor, SrTiO3:Pr3+, was developed for vacuum fluorescent displays (VFDs) and field emission displays (FEDs). It was discovered that the addition of Al is essential to achieve a high luminous efficiency of low-voltage cathodoluminescence and photoluminescence. The mechanism underlying the improvement of the luminous efficiency by the addition of Al is discussed. With the addition of 17 mol% Al, luminance of 800 cd/m2 was obtained at the anode voltage of 50 V. Powder X-ray diffraction and Auger analysis showed that the Al ions react with the Sr ions to form SrAl12O19.
Studies of Localized Levels in HgCdTe Grown on Si and CdZnTe Substrates Using Metal-Organic Chemical Vapor Deposition
Authors: Yoshino Junya , Morimoto Jun , Wada Hideo
Published: October 2002

Localized levels in the iodine-doped n-type HgCdTe fabricated on Si and CdZnTe substrates by metal-organic chemical vapor deposition are studied by Fourier transform infrared spectroscopy (FT-IR) and Hall measurement. These surface morphologies are observed by laser scanning microscopy (LSM). From the temperature dependencies of mobility and carrier concentration obtained by Hall measurement, and of transmittance obtained by FT-IR, microstructural defects, doped I and a Hg atom on the Te site are thought to be the origins of localized levels for HgCdTe grown on Si substrate. Many pits are observed by LSM, suggesting the existence of defects. On the other hand, a Hg atom on a Te site is the most conceivable origin of localized levels for HgCdTe grown on CdZnTe substrate. Since the heavily doped I leads to the degeneration of HgCdTe, other origins of localized levels are masked and cannot be confirmed. In the MCT grown on CdZnTe, microstructural defects and Hg vacancies are ruled out as the major candidates for the origin of the localized levels because of the high quality of HgCdTe.