bluuebunny/crossref_metadata_2025 huggingface dataset:
Time-resolved Photoluminescence and Carrier Dynamics in Vertically-coupled Self-assembled Quantum Dots
Authors: Gontijo I. , Buller G. S. , Massa J. S. , Walker A. C. , Zaitsev S. V. , Gordeev N. Yu. , Ustinov V. M. , Kop'ev P. S.
Published: October 2002

The relaxation mechanisms of an array of 10 vertically coupled layers
of InGaAs/AlGaAs quantum dots were studied by time-resolved
photoluminescence. Both resonant and non-resonant excitation were
employed and the photoluminescence (PL) intensity in the non-resonant case is a factor of
200 larger than the intensity with resonant excitation. The results
obtained in the non-resonant pumping experiment were analysed with a
rate equation model. It was found that the PL decay time increases
rapidly with the wavelength of detection. Large carrier capture
cross-sections [(2.5±0.9)×10-5 cm3/s] were deduced, resulting in
a capture time of 1 ps for a carrier concentration of 4×1016 cm-3.
A very fast PL risetime was observed with resonant pumping, ruling
out a phonon bottleneck effect in these samples. The decay times at a
given wavelength are always shorter for resonant than for
non-resonant excitation and their difference increases rapidly with
wavelength. This is interpreted in terms of a state filling effect
for the non-resonant case.
Spectroscopy of Hard X-Rays (2–15 keV) Generated by Focusing Femtosecond Laser on Metal Targets
Authors: Fujimoto Yasushi , Hironaka Yoichiro , Nakamura Kazutaka G. , Kondo Ken-ichi , Yoshida Masatake , Ohtani Masayuki , Tsunemi Hiroshi
Published: October 2002

Spectroscopy of hard X-rays generated by focusing a femtosecond laser (42 fs at 780 nm)
onto metal targets consisting elements of various atomic number (Z) is carried out in the
energy range between 2 and 15 keV using a direct-detection charge-coupled-device camera.Sharp K-shell line emissions are observed for X-rays generated from medium-Z targets (Ti, Fe, Ni, Cu and Zn), which can be used for X-ray diffraction without further
monochromization. A broad continuum and a weak trace of L-shell line emissions are
observed for X-rays from high-Z targets (Mo, Nb and W). The energies of the characteristic
X-rays agree well with that of X-rays from neutral atoms or slightly
ionized ions.
A Novel Blue Light Emitting Diode Using Tris(2,3-methyl-8-hydroxyquinoline) Aluminum(III) as Emitter
Authors: Yu Junsheng , Chen Zhijian , Sakuratani Yuuki , Suzuki Hironori , Tokita Masatoshi , Miyata Seizo
Published: October 2002

A novel blue electroluminescent material, tris(2,3-methyl-8-hydroxyquinoline) aluminum complex (Alm23q3) , was synthesized and used to fabricate a double-layer organic electroluminescent (EL) device as an emitting material. A device made of ITO-coated glass/triphenyldiamine derivative (TPD)/Alm23q3/Mg:Ag was fabricated, which emits bright blue light with a maximum luminance of 5390 cd/m2 at 19 V.
Electrooptical Properties of Dual-Frequency Cholesteric Liquid Crystal Reflective Display and Drive Scheme
Authors: Xu Ming , Yang Deng-Ke
Published: October 2002

We developed a bistable cholesteric reflective display using a
dual-frequency cholesteric liquid crystal. The material
exhibits two stable states at zero field: Bragg reflecting
planar texture and nonreflecting (weakly scattering) focal conic
texture. It can be switched directly from the planar texture to
the focal conic texture by a low-frequency voltage and back to
the planar texture by a high-frequency voltage. We have designed
a drive scheme for the display, which uses simultaneous
application of both low- and high-frequency voltages and
cumulative effect of the cholesteric liquid crystals.
Low-Resistivity Highly Transparent Indium-Tin-Oxide Thin Films Prepared at Room Temperature by Synchrotron Radiation Ablation
Authors: Akagi Yoshihiro , Hanamoto Katsumi , Suzuki Hiroyuki , Katoh Takanori , Sasaki Muneo , Imai Shigeru , Tsudagawa Masaru , Nakayama Yasuyuki , Miki Hidejiro
Published: October 2002

High-transparency, low-electrical-resistivity indium-tin-oxide (ITO)thin films were
prepared on quartz substrates using synchrotron radiation ablation at room temperature.
The films had a low resistivity (ρ=1.3×10-4 Ω·cm) and
high-transparency properties in the visible region (T = 83% at 550 nm). X-ray diffraction
patterns indicate that the crystalline ITO film was obtained by room-temperature deposition.
Cleaning of Ge(110) Surfaces Using an Excimer Lamp
Authors: Ichikawa Toshihiro , Kurokawa Kiyotaka , Cho Kohei , Fujii Hisashi
Published: October 2002

The formation of a GeO2 overlayer on a Ge sample surface in the air and subsequent
removal of the overlayer in ultrahigh vacuum is a newly developed method of cleaning Ge
surfaces. Using an excimer lamp as an ultraviolet light source for the oxidation, we attempted
to clean Ge(110), (111) and (100) surfaces and observed that well-reconstructed structures
characteristic of clean surfaces appeared on the surfaces. Reflection high-energy electron
diffraction observations immediately after the removal of the oxide overlayer suggest that the
interface of the oxide overlayer and Ge(110) substrate is rough, but it is relatively smooth in
the cases of Ge(111) and Ge(100) substrates.
Nucleation and Growth of Cu Adsorbates on Hydrogen-Terminated Si(111) Surface in Solution
Authors: Ken-ichi Hara Ken-ichi Hara , Takashi Tanii Takashi Tanii , Iwao Ohdomari Iwao Ohdomari
Published: October 2002

We report, for the first time, the behavior of Cu nucleation and growth on hydrogen- (H-) terminated Si(111) surface in solution. The samples were prepared by immersing H-terminated Si(111) surfaces in Cu-containing sulfuric acid solution with various immersion times. The Cu-adsorbed silicon surfaces were observed with an atomic force microscope (AFM). Statistical analysis of the AFM images indicates that Cu nucleation occurred immediately after immersing into the solution, and the coverage of the surfaces with Cu adsorbates increased linearly with immersion time although the average height increased negligibly. These results suggest that the growth behavior of Cu adsorbate on H-terminated Si(111) surfaces is fundamentally two-dimensional due to the long-range migration of Cu ions which were reduced at the silicon/solution interface.
Characteristics and Ferroelectric Properties of Pb(Zr, Ti)O3 Capacitors with Pt/La0.5Sr0.5Co1.0O3 Top and La0.5Sr0.5Co1.0O3/SrTiO3/Pt/SrTiO3 Bottom Electrodes
Authors: Furusawa Yoshikazu , Doi Hidekazu
Published: October 2002

Sol-gel-derived Pb(Zr, Ti)O3 films with thin, room
temperature sputter-deposited and postannealed
Pt/La0.5Sr0.5Co1.0O3 top and
La0.5Sr0.5Co1.0O3/SrTiO3/Pt/SrTiO3
bottom electrodes were synthesized on SiO2/Si(100) substrates,
and the microstructures and ferroelectric properties were
examined. Insertion of SrTiO3 layers with optimum thicknesses in
the bottom electrode improved surface roughness of the bottom
electrode and the Pb(Zr, Ti)O3 film, and strengthened the adhesion
of the bottom electrode to the substrate. The stacking of
La0.5Sr0.5Co1.0O3, SrTiO3 and Pt layers in
the bottom electrode yielded Pb(Zr, Ti)O3 (40/60) films with flat
surfaces; the fatigue tests at 3 V, 100 kH indicated that switchable
polarization was greater than 15 µC/cm2, and no fatigue
degradation was observed up to 1010 cycles. However, the PZT
films with higher Ti concentration in the composition exhibited
gradual decay in polariation from fatigue cycles of 106. The
possible reason for the decay in polarization was discussed. The
leakage current was of the order of 10-5 A/cm2 at driving
voltages of 2–3 V; considerable scattering among the leakage current
data was observed.
Inelastic Collision Processes of Methane and Ethane Molecules at a Pt(111) Surface Studied by Molecular Beam Scattering Techniques
Authors: Yagyu Shinjiro , Kino Yasunobu , Ikeuchi Toshiyuki , Hiraoka Tomomi , Kondo Takahiro , Yamamoto Shigehiko
Published: October 2002

Despite distinct differences in molecular structures and
chemical bonds of various alkanes, the inelastic collision processes
of CH4 and C2H6 on a Pt(111) surface have been found to
be very similar. Both processes can be explained qualitatively by a
simple classical binary collision model. Angular intensity
distributions of reflected molecules of both species indicate that
direct inelastic collision is primarily governed by the molecular
mass, the incident kinetic energy of the molecule and the surface
temperature of the Pt(111). Other factors such as the molecular
structure and chemical bond play minor roles in the process. However,
the degree of inelastic collision, that is, the energy transfer rate
per collision, increases with the molecular mass. Helium atom
scattering has revealed that the dissociation process on the surface
is identical for both molecules depending on the incident energy and
the surface temperature, as methyl moiety, ethylidyne moiety and
complete decomposition into carbon and hydrogen atoms,
successively. At elevated surface temperatures, however, thermally
assisted hydrogen tunneling appears to dominate ethane dissociation.
High Efficiency Secondary Electron Detection for the Electron-Beam-Reducing Projection Lithography System
Authors: Nakasuji Mamoru , Shimizu Hiroyasu
Published: October 2002

The secondary electron (SE) trajectories are calculated for two
cases, in which the axial magnetic field from the projection lens at
the target is zero and not zero. In the former case, SEs are easily
detected by the SE detector, which is placed distant from the optical
axis. For the latter case, it is difficult to detect SEs. The
reasons are clear because, for the former case, the magnetic flux
never crosses the target plane, and for the latter case, most of the
magnetic flux crosses the target plane, and SEs with relatively small
initial SE energy (E
i) tend to travel along the magnetic
flux. When an axially symmetric electrostatic field whose potential
at the optical axis is 0.35 V, for the maximum E
i of
30 eV and the emission angle of 30°, and for the
E
i of 3 eV and the maximum emission angle of
89°, all the SEs are detected by the SE detector.
Spatial Energy Distributions of Sputtered Atoms and Reflected Particles during Kr+ and Ar+ Ion Beam Sputtering of Si and Ge
Authors: Lee Nae-Eung
Published: October 2002

For the successful low temperature growth of Si and Ge thin films using ion-beam sputter deposition (IBSD), it is important to avoid residual damage induced by energetic sputtered atoms and/or reflected particles and the incorporation of reflected particles into growing films. We have used a Monte Carlo program to calculate the spatial flux and energy distributions of sputtered atoms and reflected particles as a function of ion beam incidence energy, incidence angle, and energy for different combinations of target materials (Si and Ge) and ion beam (Ar+ and Kr+) species. Average energies of sputtered atoms and reflected particles show a strong emission-angle-dependence and therefore the position of the substrate during IBSD is an important factor in controlling the film quality.
Imaging Characteristics of 0.12 µm Dynamic Random Access Memory Pattern by KrF Excimer Laser Lithography
Authors: Nakao Shuji , Tsujita Kouichirou , Arimoto Ichirou , Wakamiya Wataru
Published: October 2002

Imaging characteristics of a 0.12 µm dynamic random
access memory (DRAM) cell pattern by KrF excimer laser
lithography are investigated by optical image calculations.
Using modified illuminations optimized for specific patterns
and an attenuating phase shift mask (atten-PSM), depth of
focus (DOF) can be achieved up to ∼0.8 µm with high
numerical aperture (NA) of 0.70–0.75. However, the image
quality is significantly degraded by lens aberration of
∼0.06λ in root-mean-square optical pass difference
(RMS-OPD), which is observed in a stepper for 0.25 µm generation
devices. Accordingly, the development of a low aberration
lens is necessary to realize 0.12 µm DRAM cell pattern
formation by KrF excimer laser lithography.
Projection Reduction Exposure with Variable Axis Immersion Lenses (PREVAIL)-A High Throughput E-Beam Projection Approach for Next Generation Lithography
Authors: Pfeiffer Hans C.
Published: October 2002

Projection reduction exposure with variable axis immersion lenses (PREVAIL) represents the
high throughput e-beam projection approach to next generation lithography (NGL), which
IBM is pursuing in cooperation with Nikon Corporation as an alliance partner. This paper
discusses the challenges and accomplishments of the PREVAIL project. The supreme challenge
facing all e-beam lithography approaches has been and still is throughput. Since the throughput of
e-beam projection systems is severely limited by the available optical field size, the key to success
is the ability to overcome this limitation. The PREVAIL technique overcomes field-limiting
off-axis aberrations through the use of variable axis lenses, which electronically shift the optical
axis simultaneously with the deflected beam, so that the beam effectively remains on axis. The
resist images obtained with the proof-of-concept (POC) system demonstrate that PREVAIL
effectively eliminates off-axis aberrations affecting both the resolution and placement accuracy of
pixels. As part of the POC system a high emittance gun has been developed to provide uniform
illumination of the patterned subfield, and to fill the large numerical aperture projection optics
designed to significantly reduce beam blur caused by Coulomb
interaction.
Effect of Chelating Agents on High Resolution Electron Beam Nanolithography of Spin-Coatable Al2O3 Gel Films
Authors: Saifullah Mohammad S. M. , Namatsu Hideo , Yamaguchi Toru , Yamazaki Kenji , Kurihara Kenji
Published: October 2002

The effect of chelating agents on the electron beam exposure characteristics as well
as environmental stability of the spin-coatable Al2O3 gel films is discussed. It was
found that the Al2O3 gel films prepared by reacting aluminium tri-sec-butoxide,
Al(OBus)3, with acetylacetone (AcAc), AcAc/Al2O3, gave better environmental stability
and patterning characteristic than the gel films prepared by reacting the Al(OBus)3 with
ethylacetoacetate (EAcAc), EAcAc/Al2O3. The latter suffered from a faster moisture
attack in the laboratory atmosphere. Both EAcAc/Al2O3 and AcAc/Al2O3 films are ∼106
times more electron beam sensitive than sputtered AlO
x
films, thus bringing the
formers' sensitivity very close to some of the organic electron beam resists. It was seen
that the baking temperature up to 70°C has almost no effect on either the sensitivity or
the contrast in both the films; but it has a significant effect on the developing
characteristics. Electron beam nanolithography gave 20 nm linewidth with a rectangular
cross-section in both EAcAc/Al2O3 and AcAc/Al2O3 films. It was observed that the
etching characteristics of Al2O3 films in the electron cyclotron resonance (ECR) plasma
are dependent upon the final baking temperature of the developed pattern. Preliminary
plasma etching studies show that 15 nm lines on polysilicon can be etched.
Coulomb Blockade Phenomena in Si Metal-Oxide-Semiconductor Field-Effect Transistors with Nano-Scale Channels Fabricated Using Focused-Ion Beam Implantation
Authors: Kondo Hiroki , Izumikawa Kenta , Sakurai Masakazu , Baba Shin-ichi , Iwano Hirotaka , Zaima Shigeaki , Yasuda Yukio
Published: October 2002

We have fabricated Si metal-oxide-semiconductor field-effect
transistors of small dimensions using focused-ion-beam (FIB)
implantation and SiO2 implantation masks with the width of
63–118 nm and have investigated the Coulomb blockade phenomena in
these devices. The source and drain regions are formed by FIB
implantation with a beam diameter of about 100 nm and the effective
channel length is estimated to be 27–82 nm. Periodic oscillations of
conductance, which are considered to be Coulomn blockade osillations,
are observed at temperatures below 13 K. The measured oscillation
period of V
G is 1.2–3.1 V and the gate capacitance is
estimated to be 0.053–0.14 aF for different channel
lengths. Furthermore, it is found the the oscillation period of
V
G increases as the channel length increases, which
indicates that the dot radius decreases with increasing channel
length. Large negative magnetoresistance is distinctly observed at the
top of oscillation peaks and, on the other hand, only weak
magnetoresistance is obtained at the bottoms.
63-nm-Pitch Pit Pattern Fabricated on Polycarbonate Surface by Direct Nanoprinting
Authors: Yokoo Atsushi , Nakao Masashi , Yoshikawa Hiroshi , Masuda Hideki , Tamamura Toshiaki
Published: October 2002

Nanoscale pit patterns were formed on a polycarbonate substrate surface, which is
commonly used for compact disks, by direct nanoprinting. Pit patterns with 100, 70,
and 63 nm pitches were imprinted on the disk surface using a SiC mold with a nanostructure projection pattern. These pitches correspond to the the storage densities
of 75, 150, and 185 Gbit/in2. We evaluated the mold-holding temperature and press-pressure dependence of the pit depth. We also evaluated the press-time dependence.
With a relatively low press-pressure of 1.3 kg/mm2 at room temperature, a 100-nm-pitch
pit pattern with a pit depth of over 40 nm was fabricated using a mold with a projection
height of 60 nm.
Introducing Protons into Potassium Tantalate Niobate Single Crystals
Authors: Tadayuki Imai Tadayuki Imai , Shogo Yagi Shogo Yagi
Published: October 2002

Potassium tantalate niobate single crystals are capable of capturing
protons in their lattice. We examined this capability via analysis of
their O-H absorption spectra in the near infrared region. Protons are
captured in the crystals together with oxygen in the form of water
molecules. Therefore, when we wish to introduce protons into the crystals,
they must contain oxygen vacancies of some kind. The vacancy
concentrations for as-grown crystals depend on the melt compositions
used for growth. The addition of copper and/or lithium to the melt
decreases the vacancy concentration. We were able to increase the
concentration either by deoxidizing the melt used for crystal growth,
or by post-growth heat treatment.
Response Characteristics of High-Performance Photorefractive Liquid Crystals
Authors: Ono Hiroshi , Kawatsuki Nobuhiro
Published: October 2002

The time response of high-performance photorefractivity in a thick-grating regime was characterized in high- (H-LC) and low-molar-mass liquid
crystal (L-LC) mixtures (HL-LCMs) doped with fullerene. A high two-beam
coupling gain coefficient of over 250 cm-1 was achieved at a low applied dc field
of 0.16 V/µm. The photorefractive grating formation time was varied between
0.12 and 0.5 s, which strongly depended on the two-beam power ratio, the two beam intensities and the applied dc field.
Strained Layer Multiquantum Barriers with Improved Carrier Injection and Confinement
Authors: Irikawa Michinori , Ishikawa Takuya , Sasaki Yoshitaka , Kasukawa Akihiko , Iga Kenichi
Published: October 2002

The effects of using strained layer superlattice in multiquantum barriers (MQBs) were
analyzed with focus on InP-based materials and their application to strained layer
multiquantum well lasers (SL-MQW LDs). Tensile strained barriers are shown to largely
increase the effective barrier height of MQBs. A new barrier material, AlInP, which
is 1–1.5% tensile strained on InP, is shown to have inherent advantages of large conduction
band
edge discontinuity ΔE
c and low aluminum content compared to conventional AlInAs on
InP. Those advantages are confirmed for strain-compensated MQB with tensile
barrier/compressive
well in terms of increasing the effective barrier height. Some disadvantages of the
strain-compensated MQB are also pointed out; the increase in density of holes injected into
the MQB region under lasing conditions and the high p-doping concentration required. To
solve those problems, an improved method of carrier injection through minibands with gradually
enhanced energy levels toward the MQW region is presented, which is shown to enable elimination
of the carrier transport effect and to result in marked improvement in laser performances.
Optical and Electrical Properties of β-FeSi2/Si, β-FeSi2/InP Heterojunction Prepared by RF-Sputtering Deposition
Authors: Okajima Keiichi , Wen Ching-ju , Ihara Manabu , Sakata Isao , Yamada Koichi
Published: October 2002

The composition dependence of the optical absorption and the photoelectric
measurements of β-FeSi
X
thin films prepared by RF-sputtering were studied, where X was in the
range of 1.9–2.3. The absorption coefficient increased steeply at photon energies near 0.9 eV.
The photovoltaic properties and the I–V characteristics of β-FeSi
X
/n-Si heterojunctions were
measured. The open-circuit photovoltage (V
OC) was about 40 mV, and independent of X and the
substrate temperature. The photoelectric yields of a β-FeSi
X
/n-Si heterojunctions were measured
and the photoemission thresholds φ1 and φ2 were determined to be 0.64 and 0.96 eV for X=2.1.
It was suggested that a deep trap level existed on the interface and a large discontinuity of the
conduction band (ΔE
c) was formed. The value of
ΔE
c decreased from 0.35 eV to 0.30 eV as the
value of X increased. In addition, the photovoltaic properties of β-FeSi2/InP heterojunctions
were investigated to obtain ΔE
c lower and V
OC higher than that of β-FeSi
X
/n-Si. For β-FeSi
X
/p-InP, a maximum V
OC of 450 mV was obtained under concentrated illumination.
Electron Affinity and Effect of Annealing on Heavily Boron-Doped Diamond Films
Authors: Wong Ka Wai , Lee Shuit Tong , Lin Zhangda , Lam Yat Wah , Kwok Raymund Wai Man
Published: October 2002

A series of heavily boron-doped polycrystalline diamond films was studied. It was found that the electron affinity of the diamond surfaces increased with increasing doping concentration and the Fermi level was pinned at ∼0.35 eV above the valence band maximum (VBM). After annealing at ∼500°C, the electron affinity of all samples decreased and the Fermi level increased to  0.87 eV. These changes were concurrent with a decrease in the concentration of both boron and oxygen, and an increase in that of B
x
O
y
relative to elemental boron on the diamond surfaces. A model was proposed to explain the dependence of electron affinity on boron concentration, and to explain other changes observed upon annealing.
Laser Ablation of Poly(methylmethacrylate) Doped with Aromatic Compounds: Laser Intensity Dependence of Absorption Coefficient
Authors: Jun Wang Jun Wang , Hiroyuki Niino Hiroyuki Niino , Akira Yabe Akira Yabe
Published: October 2002

We developed a novel method of obtaining an absorption coefficient which depends on the laser intensity, since a single-photon absorption coefficient of a polymer could not be applied to laser ablation. The relationship between the nonlinear absorption coefficient and the laser intensity was derived from experimental data of transmission and incident laser intensities. Using the nonlinear absorption coefficient of poly(methylmethacrylate) doped with benzil and pyrene, we succeeded in fitting the relationship of etch depth and laser intensity, obtained experimentally, and discussed the energy absorbed by the polymer at the threshold fluence.
Consideration on the Quantitativeness of Reflection High Energy Electron Diffraction Intensity as a Tool to Monitor the Coverage of the Si(111) Surface by 7×7 Domains
Authors: Kazuyoshi Shimada Kazuyoshi Shimada , Satoshi Katsube Satoshi Katsube , Tetsuya Ishimaru Tetsuya Ishimaru , Hiroki Kawada Hiroki Kawada , Iwao Ohdomari Iwao Ohdomari
Published: October 2002

The quantitativeness of reflection high energy electron diffraction (RHEED) intensity as a high-speed tool to monitor nucleation and growth of 7 ×7 dimer-adatom-stacking-fault (DAS) domains on Si(111) surface rapidly quenched from a high-temperature disordered 1 ×1 phase has been investigated by comparing the time dependence of both RHEED intensity and scanning tunneling microscope (STM) images. The superlattice reflection intensity of RHEED normalized with that of uniform coverage increased gradually as a function of time after the quenching. The increase rate was higher at higher substrate temperature. A series of STM images revealed the transient aspect of the Si(111)7 ×7 reconstruction that a number of nuclei were randomly formed at the initial stage of growth, and the domain density decreased due to coalescence as the growth proceeded. The coverage by 7 ×7 DAS domains obtained from STM images was always higher than the normalized intensity of superlattice reflection, which showed that the intensity was reduced due to interference between randomly located DAS domains.
Effect of Multiply Charged Ions on the Vickers Hardness of TiC Films
Authors: Akira Suzuki Akira Suzuki
Published: October 2002

In previous experiments, TiN films or (Ti,Al)N films deposited by the high-voltage discharge method are found to exhibit good abrasion resistance properties or superior hardness. This effect is considered to be caused by multiply charged ions which are generated by the high-voltage discharge; however, it may also be caused by the high ionization rate induced by the high-voltage discharge. The rate of ions arriving at the substrate area is measured by the change in the discharge voltage and the magnetic field. The rate at which ions come to the substrate is increased by forming a magnetic field, but not by an increase in the high-voltage discharge. Under both conditions, i.e., with and without a magnetic field, TiC films are deposited by the conventional method and by the high-voltage discharge method. Comparison of the Vickers hardness of these films is carried out. In both cases, films deposited by the high-voltage discharge method are harder than those obtained by the conventional method.
Electron Field Emission Characteristics of Planar Field Emission Array with Diamondlike Carbon Electron Emitters
Authors: Lin Chin-Maw , Chang Shoou-Jinn , Yokoyama Meiso , Chuang Feng-Yu , Tsai Chun-Hui , Wang Wen-Chun , Lin I-Nan
Published: October 2002

The electron emission characteristics of planar field emission arrays (FEAs), containing undoped and boron-doped diamondlike carbon (DLC) films as emitters, were investigated. The planar DLC FEAs require only 13.3 V/µm to turn on the electron field emission, whereas the boron-doped planar DLC FEAs requires an even lower electric field (9.8 V/µm) to trigger the electron emission. The boron-doped DLC films also possess an electron emission property highly superior to that of the undoped DLC films and exhibit a stable electron emission current of 938 µA under a 20 V/µm bias voltage, which corresponds to a high emission current density of (J
e)B-DLC=128 mA/cm2. These superior properties suggest that the boron-doped DLC FEAs are potentially useful as electron emitters in flat panel displays.
Electrode Structure and Heat Treatment Effects on Stabilization of Capacitive Humidity Sensor with Plasma-Polymerized Thin Film
Authors: Takeda Shin-ichi
Published: October 2002

Organic as-grown films obtained by rf plasma excitation have, in general, unstable properties that appear with time, which induce deviations from accurate values of the relative humidity (RH). In this paper, the improvement of the humidity properties of the as-grown films by heat treatment, and the extension of lifetime through the arrangement of electrodes of the sensors are described. Plasma-polymerized polycresol (PC) films, used as a material to sense water vapor, are subjected to two different heat treatments, i.e., the continuous heat cycle and the alternative trapezoidal form of the temperature cycle in vacuum. These heat treatments led to the evaporation of small unreacted molecules, and at the same time, dissociation, repolymerization and cross-linking with radicals of the polymer chain. Thus, these treatments cause a decrease in the concentration of hydrophilic groups (OH) and in free volume, which limits the amount of adsorbable water molecules in the film. Consequently, improved and stable RH sensors were obtained.
Electronic Properties and Electroluminescence of Monosubstituted Polyacetylenes and Their Mixtures with Disubstituted Polyacetylene
Authors: Rahmat Hidayat Rahmat Hidayat , Masaharu Hirohata Masaharu Hirohata , Akihiko Fujii Akihiko Fujii , Masahiro Teraguchi Masahiro Teraguchi , Toshio Masuda Toshio Masuda , Katsumi Yoshino Katsumi Yoshino
Published: October 2002

Monosubstituted polyacetylenes (PA), that is, poly(phenylacetylene) (PPA) derivatives with various substituents attached at the ortho-position of the phenyl ring, have been studied. The valence band top and the bandgap energy of these polymers were estimated in the range from -5.5 eV to -5.9 eV (vs vacuum level) and from 1.9 eV to 2.3 eV, respectively, depending on the substituents. Although PL of these PPA derivatives is very weak, we have observed electroluminescence (EL), which is considered to be related to the nature of the self-trapped excitonic states of these polymers. The EL characteristics were found to depend on the substituents of polymers. In the mixture of poly(o-trimethylsilylphenylacetylene) (PPA-oSiMe3) with the strong luminescent disubstituted PA, poly(1-phenyl-2-p-n-butylphenylacetylene) (PDPA-nBu), the enhancement of PL of PPA-oSiMe3 was not observed. However, EL of PPA-oSiMe3 was enhanced in the mixture with PDPA-nBu, which is explained in terms of excitation energy transfer.
Active Liquid Crystal Devices Incorporating Liquid Crystal Polymer Thin Film Waveplates
Authors: E. Stockley Yoriko Morita , M. Johnson Kristina , Eckhard Hanelt Eckhard Hanelt , Frank Sandmeyer Frank Sandmeyer
Published: October 2002

A method of fabricating active liquid crystal (LC) devices incorporating
liquid crystal polymer (LCP) films with passivation layers in combination
with conventional LC monomers is presented. Unlike monomeric LC
waveplates, LCP waveplate stacks can be produced on a single substrate.
Furthermore, the passivation layer is shown to act as an effective
alignment and protective layer for LC monomers and LCPs, thus enabling the
assembly of variable LC components with integrated thin film LCP waveplates
in an LC cell configuration. Such active devices with thin film waveplate
stacks are useful in applications such as tunable wavelength filters for
wavelength division multiplexing (WDM) communication systems. The device
fabrication method is used to produce a single-unit, double-pass,
polarization-insensitive variable LC phase modulator (LCPM).
Atomic-Layer Etching of a Br-Saturated Si(111)-7×7 Surface by Using Scanning Tunneling Microscope
Authors: Mochiji Kozo , Ichikawa Masakazu
Published: October 2002

Atomic-layer etching of Br-saturated Si(111) surfaces has been achieved by
using scanning tunneling microscope at room temperature. At a Br2 dose of 100 L,
most of the Si adatoms are saturated with Br atoms, while the 7×7 structure is
completely retained. At further Br2 doses up to 400 L, most of the Si adatoms are
removed during the tip scanning at a sample bias of +3 V, and the underlying rest-atom layer is imaged. The adatoms remaining on the scanned surface are
dominantly SiBr and SiBr2 species, suggesting that highly brominated adatoms like
SiBr3 or SiBr4 are more likely etched away during the tip scanning. These highly
brominated silicon adatoms are not volatile at room temperature, but easily desorb
through the field evaporation under the usual scan mode.
Effects of Reactor Pressure on Epitaxial Lateral Overgrowth of GaN via Low-Pressure Metalorganic Vapor Phase Epitaxy
Authors: Miyake Hideto , Motogaito Atsushi , Hiramatsu Kazumasa
Published: October 2002

The effects of reactor pressure on epitaxial lateral overgrowth (ELO) via low-pressure
metalorganic vapor phase epitaxy (MOVPE) have been studied in relation to growth temperature.
For the ELO GaN on SiO2 stripes along the <1100> direction of the underlying GaN,
on decreasing the reactor pressures from 500 to 40 Torr or increasing the growth temperatures
from 950 to 1050°C, the (0001) surfaces become broad and the side walls changed from inclined
{1122} surfaces to vertical {1120} surfaces. For the ELO GaN on the stripes along
the <1120> direction, the shapes with {1101} facets are independent of the
reactor pressure and growth temperature. The ELO of GaN is dominated by the diffusion-limited process.
Chirp-Free Tuning of Fiber Bragg Grating Using a Cantilever Beam
Authors: Yu Youlong , Tam Hwayaw , Geng Shuwei , Demokan Muhtesem Suleyman , Liu Zhiguo , Chung Wenghong
Published: October 2002

A new approach for tuning the wavelength of a fiber Bragg grating without chirping is
demonstrated. Tuning is achieved by bending a triangular cantilever beam with the grating was
epoxied on its surface. The isosceles triangle was firmly fixed at its base and bending was realised by
exerting a force to its vertex. Chirp-free tuning of a fiber Bragg grating over a wavelength range of
4.52 nm is demonstrated. Using a correction index of 0.7, the experimental results are in good
agreement with the theoretical values.
Effect of Ultrathin Top Silicon Layers on the X-Ray Photoelectron Emission from the Buried Oxide in Silicon-on-Insulator Wafers
Authors: Katayama Toshiharu , Yamamoto Hidekazu , Ikeno Masahiko , Mashiko Yoji , Kawazu Satoru , Umeno Masataka
Published: October 2002

The intensities of photoelectrons emitted from ultrathin top Si(100)
layers and buried oxide layers in silicon-on-insulator (SOI) samples were
analyzed and the modulation in the polar-angle intensity distributions of
photoelectrons emitted from buried oxide layers was observed for the first
time. A possible reason for the intensity modulation is multiple scattering
of photoelectrons traveling in the SOI layer. The intensity change of
photoelectrons emitted from buried oxide layers as well as from SOI
layers disperses the apparent thicknesses of the SOI layer determined by
angle-resolved X-ray photoelectron spectroscopy (AR-XPS) for various
polar angles.
Electron Energy Control in Inductively Coupled Plasma Employing Multimode Antenna
Authors: Shindo Haruo , Urayama Takuya , Fujii Takashi , Horiike Yasuhiro , Fujii Syuitsu
Published: October 2002

A method of electron energy control was studied in an inductively coupled plasma
employing a multimode antenna, for high etching performance in ultra large-scale-integrated circuit (ULSI)
fabrication processes. Electron energy was reduced by changing the azimuthal mode of the
antenna from m=0 to m=1 with no notable change in electron density. The electron energy
reduction at the m=1 mode was found by Langmuir probe measurement. This behavior was also
confirmed by optical emission spectroscopy. Since the energy reduction was more remarkable
at lower pressures, it was considered to be due to the reverse of the induction field with
a smaller length in the higher mode antenna.
Polypyrrole Films with Anisotropy for Artificial Muscles and Examination of Bending Behavior
Authors: Mitsuyoshi Onoda Mitsuyoshi Onoda , Tetsuya Okamoto Tetsuya Okamoto , Kazuya Tada Kazuya Tada , Hiroshi Nakayama Hiroshi Nakayama
Published: October 2002

The novel features of electrochemical actuators fabricated from a cylindrical polypyrrole (PPy) pipe prepared by the electrochemical polymerization technique have been described. This cylindrical PPy pipe was cut into a rectangular film and its electrochemical and electrical properties were measured. When the inner surface of the PPy film (surface in contact with electrolyte when PPy was polymerized) was insulated and redox was carried out, the PPy film bent toward the outer surface (surface in contact with a slender Teflon pipe when PPy was polymerized) upon reduction and returned to its original shape upon oxidation. However, the bending was not completely accomplished by redox when the outer wall side of the PPy film was insulated. Although such an anomalous bending in the PPy-film actuator cannot be explained satisfactorily at this stage, we speculate that the bending phenomena are due to the difficulty of dopant transfer between inner and outer surfaces.
Direct Observation of Magnon Excitation in a Ferromagnetic Tunnel Junction Using Inelastic-Electron-Tunneling Spectroscopy
Authors: Junichirou Murai Junichirou Murai , Yasuo Ando Yasuo Ando , Makoto Kamijo Makoto Kamijo , Hitoshi Kubota Hitoshi Kubota , Terunobu Miyazaki Terunobu Miyazaki
Published: October 2002

Inelastic-electron-tunneling spectroscopy (IETS) is applied to investigate the spin-dependent tunneling process for a Ta/Ni80Fe20/FeMn/Ni80Fe20/Al-oxide/Co/Ni80Fe20 ferromagnetic tunnel junction. IET spectra for both parallel and antiparallel magnetization configurations of ferromagnetic electrodes exhibit a strong peak at 20 mV. Using the subtraction between these spectra, we obtain the inelastic excitation spectrum induced only by the magnetic origin. This spectrum exhibits a strong peak at 18 mV and decreases monotonically with increasing bias voltage. The bias-voltage dependence of tunnel magnetoresistance (TMR) is the same. These results are discussed by considering the distribution of the surface magnon excitation energy.
Pretilt Angle Dependence of Azimuthal Anchoring Energy in Nematic Liquid Crystals
Authors: Mada Hitoshi , Saito Susumu
Published: October 2002

Azimuthal anchoring energy was measured by a novel method for sample cells of several liquid crystals on various aligning layers. In this method, the deviation of director was measured and determined accurately, even in the case where the dispersion of the rotatory power is significant. The obtained azimuthal anchoring energy is widely distributed from 10-10 J/m2 to 10-5 J/m2 for samples with a pretilt angle ranging from 1.6 to 87.2 degrees. The azimuthal anchoring energy tends to depend on pretilt angles with even cosine powers. The experimental results can be theoretically explained by expanding the surface energy in power series of the tensor order parameter at the surface, the easy axis, and the surface normal unit vector.
Yellow Emission from Zinc Oxide giving an Electron Spin Resonance Signal at g=1.96
Authors: Ohashi Naoki , Nakata Tomokazu , Sekiguchi Takashi , Hosono Hideo , Mizuguchi Masafumi , Tsurumi Takaaki , Tanaka Junzo , Haneda Hajime
Published: October 2002

ZnO polycrystals doped with Li, Cu or Al were prepared by solid-state reactions and their
cathodoluminescence (CL) and electron spin resonance (ESR) spectra were measured. A strong
yellow emission centered at 2.0 eV was observed for the Al-doped specimen and its intensity was
higher than that of the green emission observed for the Al-free samples. The intensity of the green
emission was independent of the annealing atmosphere. On the other hand, the intensity of the
yellow emission was enhanced by annealing in Ar gas but was suppressed by annealing in O2 gas.
The increase of the intensity of the ESR signal at g≈1.96 was parallel to the increase in the yellow
emission intensity. The effect of Al-doping upon CL spectra was discussed on the basis of the
assignment that the yellow emission is due to a donor-acceptor pair transition.
Capacitively-Detected Magnetic Resonance in Hydrogenated Amorphous Silicon Solar Cells
Authors: Brandt Martin S. , Neuberger Ralph T. , Bayerl Martin W. , Stutzmann Martin
Published: October 2002

Spin-dependent transport processes in hydrogenated amorphous silicon (a-Si:H) solar cells at
high frequencies are studied with capacitively-detected magnetic resonance (CDMR). A
resonant increase of the capacitance at room temperature is found with a g-factor of 2.0055,
characteristic for the spin-dependent trapping of electrons at neutral dangling bonds. It is
shown that with the help of spin-dependent capacitance measurements quantitative information
on the defect density in the device can be obtained, a particular advantage over conventional
electrically detected magnetic resonance (EDMR) where resonant changes of the dc
conductivity are measured.
New Laser Garnet Crystal with Disordered Structure
Authors: Alexander Kaminskii Alexander Kaminskii , Ken-ichi Ueda Ken-ichi Ueda , Galina Bogomolova Galina Bogomolova , Jose Garcia-Sole Jose Garcia-Sole , Daniel Jaque Daniel Jaque , Juan Capmany Juan Capmany , Doyle Temple Doyle Temple
Published: October 2002

We report the room-temperature, low-threshold, continuous wave (CW) laser action at the wavelengths of two near-IR 4
F
3/2→4
I
11/2 and 4
F
3/2→4
I
13/2 emission channels of Nd3+ ions in new disordered garnet YGaO3. All observed generation lines are identified. In addition, confined spectroscopic characterization, including the determination of peak cross-sections of induced transitions, of this new laser material were carried out.
Infrared Absorption at Longitudinal Optical Frequency in Amorphous Oxides and Their Mixtures
Authors: Ohwaki Takeshi , Onishi Takashi
Published: October 2002

Infrared absorption at longitudinal optical (LO) frequency was measured in amorphous aluminum oxide, amorphous magnesium oxide and their mixtures. It was found that the LO mode of a mixture of these oxides has a single peak, and its position lies between those of the constituents if two oxides are mixed on the order of angstroms. The LO mode of amorphous MgAl2O4 is also reported.
Refractive Index Change of Dithienylethene in Bulk Amorphous Solid Phase
Authors: Kawai Tsuyoshi , Fukuda Norio , Gröschl Dieter , Kobatake Seiya , Irie Masahiro
Published: October 2002

A diarylethene derivative, 1,2-bis(5-(4-tert-butylphenyl)-2,4-dimethylthiophen-3-yl)- 3,3,4,4,5,5-hexafluorocyclopentene, forms stable amorphous solid with T
g of 68°C. Reversible photochromism in the amorphous solid film is observed upon alternate irradiation with UV (e.g. 313 nm) light and visible (580 nm) light. The refractive index of the solid film changed by as much as 3.8×10-2 along with the photoisomerization.
Generation of Coherent cw-Terahertz Radiation Using a Tunable Dual-Wavelength External Cavity Laser Diode
Authors: Ping Gu Ping Gu , Fan Chang Fan Chang , Masahiko Tani Masahiko Tani , Kiyomi Sakai Kiyomi Sakai , Ci-Ling Pan Ci-Ling Pan
Published: October 2002

A tunable dual-wavelength external cavity laser diode (2-λ-ECL) was used to generate tunable coherent cw-terahertz (THz) radiation by photomixing in a biased photoconductive antenna fabricated on a low-temperature-grown (LTG)-GaAs film. The 2-λ-ECL oscillated at the two output modes simultaneously with a frequency separation from 250 GHz to 2.1 THz in the same cavity. We demonstrated that the frequency of the emitted THz radiation corresponded to the difference frequency between the two modes of the diode laser. The tunable 2-λ-ECL, due to its compact design and ease of optical alignment, is a promising laser source for the generation of tunable cw-THz radiation by photomixing.
Nanoscale Switching and Domain Structure of Ferroelectric BaBi4Ti4O15 Thin Films
Authors: Harnagea Catalin , Pignolet Alain , Alexe Marin , Satyalakshmi Kayyar M. , Hesse Dietrich , Gösele Ulrich
Published: October 2002

Ferroelectric domain structures of epitaxial BaBi4Ti4O15 (BBiT) thin films with
different orientations have been imaged for the first time at the nanometer scale. Using
the piezoresponse mode of scanning force microscopy it was demonstrated that the spontaneous
polarization of BBiT has no component along the c-axis of the unit cell. Local piezoelectric
hysteresis loops from non c-oriented grains with lateral sizes of 300 to 500 nm were recorded.
The saturation values of the piezoelectric constant perpendicular to the c-axis are comparable
to those measured macroscopically. A distinct ferroelectric behavior was still found in grains
as small as 300 nm in lateral size.
Interface and Defect Structures of (001)-Oriented SrBi2Ta2O9 Thin Film Epitaxially Grown on (001) SrTiO3 Single Crystal
Authors: Suzuki Toshimasa , Nishi Yuji , Fujimoto Masayuki , Ishikawa Katsuyuki , Funakubo Hiroshi
Published: October 2002

Interface and defect structures of epitaxial c-axis oriented
SrBi2Ta2O9 thin films on well lattice-matched (001) SrTiO3 substrates
were crystallographically characterized by transmission electron
microscopy. The film was coherently grown on the SrTiO3 substrate
without interfacial layers and misfit dislocations, preserving the
crystallographic relation of (001)[110] SrBi2Ta2O9//(001)[100] SrTiO3.
The plausible atomic stacking sequence at the interface was found to be
(SrTiO3 bulk)–SrO–TiO2–SrO–TaO2–Bi2O2–TaO2–SrO–(film bulk),
where an electrically neutral SrO layer could be preferentially
formed on the TiO2-terminated SrTiO3 substrate. High-resolution
lattice images of the film showed that distinctive wedge-shaped
contrasts could be attributed to the formation of c/6 translational
boundaries originating from single unit cell steps on the SrTiO3
substrate.
Characteristics of Underwater Near-Field Acoustic Radiation Force Acting on a Planar Object
Authors: Toru Hatanaka Toru Hatanaka , Yoshikazu Koike Yoshikazu Koike , Kentaro Nakamura Kentaro Nakamura , Sadayuki Ueha Sadayuki Ueha , Yoshiki Hashimoto Yoshiki Hashimoto
Published: October 2002

A phenomenon called near-field acoustic levitation (NFAL) has been reported where planar objects of several kilograms in weight are levitated in the air a few hundred micrometers away from a radiation surface. The authors experimentally studied the feasibility of underwater NFAL and demonstrated that planar objects can also be levitated in liquid. Furthermore, unexpected characteristics such as that attraction, in addition to the repulsive acoustic radiation force, acts on the planar object under certain conditions, were found.
High-Luminance Blue-Emitting BaAl2S4:Eu Thin-Film Electroluminescent Devices
Authors: Miura Noboru , Kawanishi Mitsuhiro , Matsumoto Hironaga , Nakano Ryotaro
Published: October 2002

The high-luminance blue emitting electroluminescent (EL) devices which have been satisfied with the requirement for full color displays were obtained. BaAl2S4:Eu thin-film EL devices as the new blue emitting EL phosphor was prepared by the two targets pulse-electron-beam evaporation. The maximum luminance level was 65 cd/m2 under the 50 Hz-pulse voltage. The EL spectrum had a blue emission band with a peak around 475 nm due to the 5d-4f transition for Eu2+ ion. The Commission Internationale de l'Eclairage (CIE) color coordinates of BaAl2S4:Eu EL device were x=0.12 and y=0.10.
Red Emission from Eu-Doped GaN Studied by Photoluminescence and Photo-Calorimetric Spectroscopy
Authors: Maruyama Takahiro , Sasaki Hitomi , Morishima Shinichi , Akimoto Katsuhiro
Published: October 2002

Bright and sharp photoluminescence was obtained from Eu-doped GaN films grown
by gas-source molecular beam epitaxy using ammonia. It was found that the decrease in
luminescence intensity is small between 80 K and 300 K, compared with the red emission
from InGaN. The red emission from Eu-doped GaN also showed only a small peak shift
within 1.6 meV in the same temperature range. From these results, the advantage of using
Eu-doped GaN as a stable optoelectronic material against temperature variation is shown.
A 1.3-µm GaInNAs Laser Diode with a Lifetime of over 1000 Hours
Authors: Kondow Masahiko , Kitatani Takeshi , Nakahara Kouji , Tanaka Toshiaki
Published: October 2002

A 1.3-µm-range GaInNAs/GaAs single-quantum-well laser was tested for 1000 hours
at 24°C under an auto-current-control condition. No degradation was observed.
The threshold current fell slightly (14%). The lasing wavelength was stable. The lack of
rapid degradation under an auto-power-control condition at a high temperature (50°C)
suggests that a reliable GaInNAs laser diode with a practical lifetime may soon be
realized.
Gray-Scale Operation of Surface-Stabilized Ferroelectric Liquid Crystal Displays Using Polymer-Stabilized Method
Authors: Matsui Hidehiko , Miyata Tomoyuki , Hasebe Hiroshi , Takatsu Haruyoshi , Kobayashi Shunsuke , Iimura Yasufumi
Published: October 2002

We have reported a new method of realizing gray-scale operation of
surface-stabilized ferroelectric liquid crystal displays (SSFLCDs) by controlling
the threshold voltage of the samples. The control of the threshold voltage is
achieved by forming liquid crystalline polymer networks in a FLC medium using a
UV-curable liquid crystalline monomer, and the threshold voltage is found to
decrease with increasing concentration of the doped monomer. This
phenomenon is utilized to realize the gray-scale operation, and we succeed in
obtaining a quasi-tristable SSFLCD by combining it with a two-domain structure.