bluuebunny/crossref_metadata_2025 huggingface dataset:
Widely Wavelength Tunable Ultrashort Soliton Pulse and Anti-Stokes Pulse Generation for Wavelengths of 1.32–1.75 µm
Authors: Norihiko Nishizawa Norihiko Nishizawa , Ryuji Okamura Ryuji Okamura , Toshio Goto Toshio Goto
Published: October 2002

Using dispersion shifted polarization maintaining optical fibers and a femtosecond fiber laser, a compact system of widely wavelength tunable ultrashort pulse generation is demonstrated in the wavelength region of 1.32–1.75 µm. The clear sech2 soliton pulse and the anti-Stokes pulse are generated simultaneously. The wavelengths of the two pulses are shifted to the opposite wavelength sides by changing the fiber input power. The maximum conversion efficiencies are as large as 65% for the soliton pulse and 10% for the anti-Stokes pulse. The soliton pulse and the anti-Stokes pulse copropagate along the fiber. The mechanism of the wavelength shift of the anti-Stokes pulse is also discussed.
Plasma Production by m=0 Standing Helicon Waves
Authors: Mudtorlep Nisoa Mudtorlep Nisoa , Youichi Sakawa Youichi Sakawa , Tatsuo Shoji Tatsuo Shoji
Published: October 2002

m=0 standing helicon waves (SHWs) are used to produce high-density Ar plasmas, of the order of 1013 cm-3, in a bounded cylindrical plasma column. Axial mode number N=1, 3, and 5 (N is the number of half-wavelengths in the plasma column) SHWs are strongly excited for plasma length L=10–26 cm with the rf power P
rf≤3.5 kW and external static magnetic field B
0=237 G. Hollow and parabolic density profiles that depend on the axial mode of SHW are observed. The standing wave ratio decreases with L, and travelling helicon waves dominate the plasma production for L>26 cm. The measured results are compared with a two-dimensional wave calculation.
Direct Observation of Strong Quantum-Confined Stark Effect in Vertically-Stacked Quantum Dots at Room Temperature
Authors: Ser Jung-Hoon , Lee Yong-Hee , Kim Jong-Wook , Oh Jae-Eung
Published: October 2002

Strong quantum-confined Stark effect of vertically-stacked quantum dots
(VSQDs) is observed by electroabsorption spectroscopy at room temperature. Contrary
to single-layer QDs, the VSQDs show a large red shift of 9.4 meV with electric-field
change of 60 kV/cm.
Electroluminescent Devices with Ga2O3:Mn Thin-Film Emitting Layer Prepared by Sol-Gel Process
Authors: Minami Tadatsugu , Shirai Tetsuya , Nakatani Toshikuni , Miyata Toshihiro
Published: October 2002

High-luminance electroluminescent devices have been newly developed using a
Ga2O3:Mn thin film prepared by a sol-gel process. The sol-gel
process, which eliminates the need for vacuum processes, enabled the inexpensive
preparation of Ga2O3:Mn thin films on large-area thick ceramic sheet
insulators. Gallium acethylacetonate, a relatively inexpensive and easy to handle
material, was used as the Ga source material. Thin-film electroluminescent (TFEL)
devices with a Ga2O3:Mn thin-film emitting layer prepared by the sol-gel
process at a deposition temperature of 900°C and a postannealing temperature of
1000°C exhibited luminances of 1271 and 401 cd/m2 when driven at 1 kHz
and 60 Hz, respectively.
A New Inside-Type Segmented Coil Antenna for Uniformity Control in a Large-Area Inductively Coupled Plasma
Authors: Pyung-Woo Lee Pyung-Woo Lee , Sung-Sik Kim Sung-Sik Kim , Sang-Hun Seo Sang-Hun Seo , Choong-Seock Chang Choong-Seock Chang , Hong-Young Chang Hong-Young Chang , Takanori Ichiki Takanori Ichiki , Yasuhiro Horiike Yasuhiro Horiike
Published: October 2002

It is found that a properly tuned segmented coil system allows
external control of the radial plasma density profile in an
inside-type, large-area inductively coupled plasma. This coil
system is composed of inner and outer coil segments and an
external variable inductor. The external variable inductor is used
to balance coil currents between the two coil segments for
plasma uniformity control. The measured results indicate that
radial plasma spread can be controlled and optimized with this
external variable inductor.
Effect of Intentionally Formed `V-Defects' on the Emission Efficiency of GaInN Single Quantum Well
Authors: Takahashi Hirokazu , Ito Atsuya , Tanaka Toshiyuki , Watanabe Atsushi , Ota Hiroyuki , Chikuma Kiyofumi
Published: October 2002

We investigated the effect of `V-defects' (hexagonal pits), intentionally formed at threading dislocation (TD) sites, on the emission efficiency of GaInN-based single quantum well (SQW) grown on GaN by metalorganic chemical vapor deposition. We examined the relations between the TD densities and the photoluminescence intensities of the SQW in which V-defects were intentionally formed, comparing them with the relations for a normal SQW under strong excitation conditions. As a result, we demonstrated that the intentionally formed V-defects increase the luminescence intensity and reduce the dependence of photoluminescence (PL) intensity on the TD density of underlying GaN.
A Multi-Layered Optical Disc Scheme for High Density Storage Using Transparent Media
Authors: Ho Ho-Pui , Wu Shu-Yuen , Chan Kowk-Sum , Pun Edwin Y. B. , Shum Ping
Published: October 2002

A scheme for multi-layered high-density optical storage using transparent
dielectric films is presented. Information storage in the transparent storage medium is
accomplished by varying its thickness and the subsequent information retrieval is
achieved by performing differential interference between two probe beams that
traverse two adjacent bit areas in the medium. As a demonstration we constructed a
five-layer storage sample by stacking photo-resist coated glass substrates together
and a dual probe interferometer for the readout of the stored optical bits. Apart from
the successful recovery of the information from individual layers, our experiments also
demonstrated the auto-focussing capability of the scheme by monitoring the Fresnel
reflection off the dielectric interfaces within the stack. Such feature is an important
pre-requisite for practical implementation of this scheme in real applications.
Molecular Dynamics Simulation of Crystallization in an Amorphous Metal during Shear Deformation
Authors: Tarumi Ryuichi , Ogura Akio , Shimojo Masayuki , Takashima Kazuki , Higo Yakichi
Published: October 2002

A molecular dynamics simulation was performed to investigate the structural
changes during a shear deformation process in an amorphous metal. An amorphous model
is constructed from Ni atoms interacting via a Morse-type pairwise additive potential.
At shear stresses below 2.4 GPa, shear strain increased linearly with increasing shear
stress. However, large shear deformation occurred when shear stress reached 2.8 GPa.
During this shear deformation, crystallization was observed in the model. The
crystalline phase had an fcc structure which had an orientation relationship, i.e., the
shear direction and a (111) plane are parallel. This relationship was consistent with
our experimental study on a Ni–P amorphous alloy.
Initial Dissolution Rate of Quartz Rods in Silicon Melts: Influence of Quartz Surface Conditions
Authors: Abe Keisei , Matsumoto Takeshi , Terashima Kazutaka
Published: October 2002

The influence of quartz surface conditions on the quartz dissolution rate in silicon melts has been investigated. As experimental samples with different surface conditions, raw fused amorphous quartz and fused quartz pretreated in silicon melts at 1550°C and 1500°C for 300 min were prepared, respectively. In the case of quartz pretreated in silicon melts at 1550°C, the initial dissolution rate in silicon melts at 1430°C was approximately one-third that of raw fused amorphous quartz or quartz pretreated in silicon melts at 1500°C.
Piezoelectric Properties of a High Curie Temperature Pb(In1/2Nb1/2)O3–PbTiO3 Binary System Single Crystal near a Morphotropic Phase Boundary
Authors: Yasuda Naohiko , Ohwa Hidehiro , Kume Motoyuki , Yamashita Yohachi
Published: October 2002

High-quality piezoelectric (1-x)Pb(In1/2Nb1/2)O3–xPbTiO3 binary system single
crystals near a morphotropic phase boundary were successfully grown by a conventional flux method using PbO–PbF2–B2O3 flux. The largest crystal had dimensions of about
20 mm×10 mm×5 mm. The permittivity shows a shoulder at the ferroelectric
rhombohedral to tetragonal phase transition temperature, T
fr=100°C, and then has a
maximum (35000 at 1 kHz) at the ferroelectric tetragonal to paraelectric cubic phase transition temperature, T
c=260°C. The electromechanical coupling coefficient in
rectangular bar mode, k
33
′=78%, for phased array ultrasonic transducers was obtained
by using the rhombohedral 0.72Pb(In1/2Nb1/2)O3–0.28PbTiO3 single crystal oriented
along the [001] axis in the shape of a rectangular bar of 0.2 mm in
width, 0.5 mm in thickness and 9 mm in length. The
k
33
′=78% is the highest value reported so far among all the piezoelectric materials with a T
c more than 250°C.
Generation of CW Millimeter Wave Signals in a Lithium Niobate Nonlinear Optical Waveguide Using Modulated Optical Input
Authors: Hori Toshihiro , Park Ki-Hwan , Kawanishi Tetsuya , Izutsu Masayuki
Published: October 2002

The generation of CW millimeter wave signals is observed in a LiNbO3 nonlinear optical waveguide. Optical light that has two frequency components is introduced into an optical waveguide, and the millimeter waves which are generated are obtained from the terminal connected to the metallic traveling waveguide. This configuration is made with a LiNbO3 commercial phase modulator. Millimeter waves are generated at frequencies up to 40 GHz. This is the first report of CW millimeter wave generation in a nonlinear ferroelectric waveguide, to our knowledge. A comparison of the measured signal levels with theoretically estimated ones is discussed.
The Role of Growth Rates and Buffer Layer Structures for Quality Improvement of Cubic GaN Grown on GaAs
Authors: Ogawa Masahiro , Funato Mitsuru , Ishido Teruki , Fujita Shizuo , Fujita Shigeo
Published: October 2002

Cubic GaN (c-GaN) layers are grown on GaAs(001) substrates
by metalorganic vapor phase epitaxy.
To attain high-quality c-GaN, we investigate growth conditions
and buffer layer structures.
It is found that by increasing the growth
rate from 0.35 to 1.05 µm/h,
the growth temperature region where the c-GaN composition reaches
its maximum (90%) is shifted from 700–800°C
to 850–900°C.
Regarding the film properties,
excitonic emission and high resistivity are realized
with the faster growth rate.
Subsequently, the c-GaN composition is improved by the use of
a double buffer layer (DBL) structure
instead of the conventional single buffer layer structure
without degrading the achieved
optical and electrical properties.
The DBL structure preserves a relatively high c-GaN composition
even in thick layers.
An Analysis for Measurement of Thermal Diffusivity Components of Anisotropic Platelike Samples by AC Calorimetric Method
Authors: Sheu Long-Jye , Lin Jenn-Der
Published: October 2002

This work examines the effects of anisotropy and transparency on measurements of thermal diffusivity components with an ac calorimetric method associated with laser heating. Analytical results indicate that the region where the two-dimensional effect occurs increases with the decrease of the ratio of cross-plane to in-plane thermal diffusivity. The region also increases with the optical thickness of the sample. The linear relations, as indicated by a decay constant from which the cross-plane thermal diffusivity is deduced, are not obtained for media of both optically moderate and thin thickness, while at sufficiently large optical thickness, anisotropy and two-dimensional effects are found insignificant.
Temperature Dependence of the Phonons of Bulk AlN
Authors: M. Hayes Jonathan , Martin Kuball Martin Kuball , Ying Shi Ying Shi , James H. Edgar James H. Edgar
Published: October 2002

Micro-Raman scattering measurements were performed on bulk wurtzite AlN crystals over a temperature range from 10 K to 1275 K. The temperature dependence of the frequency of the AlN phonons follows an empirical relationship previously introduced for diamond. A temperature-induced frequency shift of the E2phonon of -(2.22±0.02)×10-2cm-1/K was determined for high temperatures, which is similar to values reported for bulk GaN. The results provide the basis for the non-invasive monitoring of the temperature of (Al,Ga)N by Raman scattering.
A Novel Method for the Preparation of Green Photoluminescent Undoped Zinc Oxide Film Involving Excimer Laser Irradiation of a Sol-Gel-Derived Precursor
Authors: Nagase Toshimi , Ooie Toshihiko , Makita Yoji , Nakatsuka Masahiro , Shinozaki Kazuo , Mizutani Nobuyasu
Published: October 2002

A green photoluminescent (PL) undoped zinc oxide film was successfully prepared by a novel method involving KrF excimer laser irradiation of a sol-gel-derived precursor. This method requires the appropriate energy fluence (E
f) of 100 mJ/cm2 of the laser, and has the advantage of practical production at a low substrate temperature of 473 K in air. Transmission electron microscopy (TEM) and X-ray diffraction (XRD) observations showed that the green PL film has close-packed columnar crystals in an upper layer, where the green PL centers involving oxygen vacancies are presumed to be present.
Characterization of Polarity of Plasma-Assisted Molecular Beam Epitaxial GaN{0001} Film Using Coaxial Impact Collision Ion Scattering Spectroscopy
Authors: Sonoda Saki , Shimizu Saburo , Suzuki Yasumasa , Balakrishnan Krishnan , Shirakashi Jun-ichi , Okumura Hajime
Published: October 2002

Effects of the initial nitridation of a sapphire(0001) substrate
and the thickness of a low-temperature GaN buffer layer on the
polarity of GaN{0001} films grown by rf plasma-assisted molecular
beam epitaxy (MBE) have been investigated by coaxial impact
collision ion scattering spectroscopy (CAICISS). The volume ratios
of each domain in grown GaN{0001} films, that is, (0001) and
(0001̄), were evaluated by making comparisons between the
experimental results of the incident angle dependences of Ga and N
signal intensities and simulated ones. It was determined that the
initial nitridation of a sapphire(0001) substrate increases the
volume ratio of the (0001̄) domain in the grown film and, on
the contrary, a thick low-temperature GaN buffer layer increases
that of the (0001) domain.
Multilayer Formation of Copper Ions (Cu2+) Deposited onto Self-Assembled Monolayers of Alkanedithiols on Au (111) Surfaces
Authors: Deng Wenli , Fujita Daisuke , Yang Linjing , Nejo Hitoshi , Bai Chunli
Published: October 2002

Self-assembled monolayers (SAMs) of 1,5-pentanedithiol and 1,9-nonanedithiol on Au (111) surfaces were used to adsorb copper ions (Cu2+) from an ethanolic solution of cupric chloride (CuCl2) by chemical interaction of thiol groups and copper ions assembling multilayer structures. Ellipsometry, contact angle measurement and X-ray photoelectron spectroscopy (XPS) confirmed that the alkanedithiol molecules formed SAMs with only one-ended thiol groups attached to the gold surface, leaving the other-ended thiol groups free, which is supported by the molecular mechanics calculation. XPS and X-ray Auger electron spectroscopy (XAES) not only indicate that copper ions deposited onto SAMs from the solution by the chemical reaction of copper ions with ended free thiol groups of SAMs, but more importantly demonstrate that copper is present in the +1 oxidation state in the multilayer system. Atomic force microscopy (AFM) was used to observe SAMs and multilayer structures.
Device Simulation of Grain Boundaries with Oxide-Silicon Interface Roughness in Laser-Crystallized Polycrystalline Silicon Thin-Film Transistors
Authors: Kimura Mutsumi , Eguchi Tsukasa , Inoue Satoshi , Shimoda Tatsuya
Published: October 2002

For laser-crystallized polycrystalline silicon thin-film transistors, the effect of grain boundaries with oxide-silicon interface roughness on the transistor characteristics has been analyzed using device simulation. When grain boundaries and interface roughness are considered simultaneously, degradation of the on-current caused by grain boundaries is reduced by the interface roughness because the electric field concentration increases the carrier density and improves the conductance.
Molecular Surgery of Plasmid Deoxyribonucleic Acid Using Scanning Tunneling Microscopy with a Double-Helix Periodicity
Authors: Nakayama Yoshitaka , Tanaka Hiroyuki , Kawai Tomoji
Published: October 2002

Without the aid of enzymes, we have successfully cut pBluescript II KS(-), a plasmid deoxyribonucleic acid (DNA) molecule adsorbed on Cu(111) surfaces at pitch level resolution using a scanning tunneling microscopy (STM) surface science technique. Manipulation is performed by scanning an STM tip over the DNA molecule with increased tunneling current. The results suggest that manipulation probability is anisotropic to the angle between the direction of the scanning tip and the DNA molecule, showing a characteristic feature of the right-handed helix. The mechanism of the manipulation is discussed.
High fT 50-nm-Gate InAlAs/InGaAs High Electron Mobility Transistors Lattice-Matched to InP Substrates
Authors: Yamashita Yoshimi , Endoh Akira , Higashiwaki Masataka , Hikosaka Kohki , Mimura Takashi , Hiyamizu Satoshi , Matsui Toshiaki
Published: October 2002

We fabricated 50-nm-gate InAlAs/InGaAs high electron mobility transistors (HEMTs) lattice-matched to InP substrates using a conventional process under low temperatures below 300°C, and measured DC and RF performance. The measured cutoff frequency f
T of our 50-nm-gate HEMT is 362 GHz, which is the highest value ever reported for any transistor, and is much higher than the values reported for previous 50-nm-gate lattice-matched HEMTs. The excellent RF performance of our HEMTs might result from the low-temperature fabrication process.
Cathodoluminescence Study of Quantum-Size and Alloying Effects in Single Fractional Monolayer CdSe/ZnSe Structures
Authors: Ichirou Yamakawa Ichirou Yamakawa , Sergei V. Sorokin Sergei V. Sorokin , Alexei A. Toropov Alexei A. Toropov , Sergei V. Ivanov Sergei V. Ivanov , Arao Nakamura Arao Nakamura
Published: October 2002

Luminescence properties of single fractional monolayer CdSe/ZnSe structures with nominal thickness of 1.25 to 3.6 monolayers have been investigated by means of cathodoluminescence (CL) spectroscopy. The CL spectra exhibit sharp peaks superimposed on a broad luminescence band due to individual CdSe-enriched dots spontaneously formed in the CdSe layer. By fitting the CL spectra to the transition energies calculated by a quantum disk model taking into account compositional alloying and dot sizes, we have determined Cd concentrations in CdSe-enriched dots. The results are in good agreement with structural data, and indicate that the blue shift of the dot luminescence with decreasing nominal thickness is due to the alloying effect.
Microstructural and Dielectric Properties of High Permittivity (Pb, Ba) ZrO3 Thin Films by Sol-Gel Processing
Authors: Dey Sandwip K. , Barz Robert , Majhi Prashant , Wang Chang-Gong
Published: October 2002

High permittivity (Pb0.7, Ba0.3)ZrO3 (PBZ) films (60–110 nm) were fabricated by sol-gel processing on (111) Pt-passivated Si substrates, followed by rapid thermal annealing (RTA) at 550–700°C for 5 minutes in oxygen. The randomly oriented grains were of the crystalline perovskite phase, with minor amounts of amorphous or nanocrystalline phase in the intergranular regions. The microstructure of the PBZ films was markedly influenced by substrate annealing and RTA temperature. At 10 kHz, the low-field dielectric permittivity and loss tangent of a 66 nm PBZ film were measured to be 932 and 0.03, respectively, giving a C/A of 12.5 µF/cm2.
Regioregularity vs Regiorandomness: Effect on Photocarrier Transport in Poly(3-hexylthiophene)
Authors: Shyam S. Pandey Shyam S. Pandey , Wataru Takashima Wataru Takashima , Shuichi Nagamatsu Shuichi Nagamatsu , Takeshi Endo Takeshi Endo , Masahiro Rikukawa Masahiro Rikukawa , Keiichi Kaneto Keiichi Kaneto
Published: October 2002

The time-of-flight technique has been used to study transports of photocarriers in regioregular and regiorandom poly(3-hexylthiophene) (P3HT) films by fabricating indium-tin-oxide/P3HT/Al sandwich cell. It has been found that regularity in the coupling of monomers, head-to-tail (HT) has a marked effect on electrical properties and photocarrier transport in P3HT. Both regular and random P3HT films exhibit a dispersive photocurrent response with the positive sign of photocarrier (hole). The room temperature hole mobility of regioregular P3HT is estimated to be 1.21 ×10-3 cm2/V·s and is one order of magnitude larger than that of the random one. The mobility in regioregular P3HT is almost independent of the applied field while that of random P3HT shows a positive field dependence at the field larger than 1.0 ×105 V/cm.
Indirect-to-Direct Transition of (AlAs)n/(AlP)n Strained Short-Period Superlattices
Authors: Ohnuma Toshiharu , Nagano Masahiro , Nemoto Koshichi
Published: October 2002

We carried out first-principles calculation of (AlAs)
n
/(AlP)
n
superlattices (SLs) (n=1–5) using the full-potential linearized augmented plane-wave (FLAPW) method. The SLs are assumed to grow epitaxially on the (001) GaAs and GaP substrates. Indirect-to-direct transition was observed for n≧2 on the (001) GaAs substrate while all SLs grown on the (001) GaP substrate were indirect gap semiconductors. Optical properties were evaluated by the square of vertical transition matrix elements. The matrix elements of (AlAs)
n
/(AlP)
n
SLs grown on (001) GaAs exhibited oscillating behavior. The matrix elements for odd n are two orders larger than those for even.
Longitudinal-Pumping and Transient Collisional Excitation of High Performance Ni-Like Soft-X-Ray Lasers
Authors: Tsuneyuki Ozaki Tsuneyuki Ozaki , Keiichi Yamamoto Keiichi Yamamoto , Ruxin Li Ruxin Li , Hiroto Kuroda Hiroto Kuroda
Published: October 2002

We experimentally investigate the interaction of a preformed plasma with a high intensity 2-ps Nd:Glass laser pulse entering from the longitudinal direction. Observations of the transverse intensity profile of the longitudinal beam are found to be well reproduced by simple hydrodynamic and ray-tracing calculations, if a nonuniform line-focus is taken into account. Observations of visible emission from the plasma reveal the presence of a bright jetlike structure, which extends over an unusually long length of more than ten millimeters. Various characteristics of this jet are experimentally investigated.
Ferroelectric Thin Films Prepared by Backside Pulsed Ion-Beam Evaporation
Authors: Sonegawa Tomihiro , Arakaki Toshiki , Maehama Takehiro , Jiang Weihua , Yatsui Kiyoshi
Published: October 2002

Ferroelectric (PbTiO3 or Pb(Zr, Ti)O3) thin films have been successfully prepared on Si(100) or pyrex glasses by backside deposition of intense pulsed ion beam evaporation. The ion beam parameters were typically as follows: beam energy=1.3 MeV, ion-current density on target=0.7 kA/cm2 and pulse duration=50 ns. The composition of the thin films was in good agreement with that of the original target. The relative dielectric constant at 1 kHz was obtained to be 20, while that obtained by normal front side deposition was 150.
Formation and Properties of Carbon Nitride Thin Films by Pulsed Nd:YAG Laser Deposition
Authors: Yoshiaki Suda Yoshiaki Suda , Kazuya Doi Kazuya Doi , Jun Namba Jun Namba , Fumiaki Imura Fumiaki Imura , Hiroharu Kawasaki Hiroharu Kawasaki
Published: October 2002

Carbon nitride thin films were synthesized on Si(100) substrates by pulsed Nd:YAG laser deposition. Several spectral lines originating from the neutral and ionic species, such as carbon atoms, carbon ions, carbon molecules and carbon nitride molecules were identified in the plasma plume. The surface morphology of the carbon nitride thin films reveals numerous droplets on the films out of which several are spiral shaped. The N/C composition ratio is increased from 0.18 to 0.25 with increasing substrate bias voltage. Fourier transform infrared spectroscope absorption spectra show two characteristic bands: a broad band composed of the graphite G-band and disordered D-band of carbon, and another associated with the CN triple bond. Raman spectra have also been used to characterize the films.
Formation of Diamond Like Carbon by a Pure Carbon Arc Under High Vacuum
Authors: Tamba Moritake , Kawamura Kazuhiko , Okazaki Kiyohiko , Amemiya Hiroshi
Published: October 2002

The arc discharge plasma of solid carbon has been applied to the formation of hard carbon thin films. A double-mesh electrode is placed at the exit of the sharply directed arc plasma column confined in the magnetic bottle. The radio frequency voltage applied to the electrode is effective to diverge the plasma column radially to form a uniform plasma in front of the substrate and also to remove macroparticles. The characteristics of the obtained film are examined using Raman spectra and other techniques.
Surface of Silica Glass Reacting with Silicon Melt: Effect of Raw Materials for Silica Crucibles
Authors: Yamahara Keiji , Huang Xinming , Sakai Susumu , Utsunomiya Akira , Tsurita Yasushi , Hoshikawa Keigo
Published: October 2002

The density of brownish spots formed on the surface of silica glass through the reaction with silicon melt is studied using three types of silica glass, that are made from natural quartz powder, synthetic silica powder, and Al-doped synthetic silica powder. The density of the brownish spots was higher in natural quartz glass (NQG) than in synthetic silica glass (SSG) and in Al-doped synthetic silica glass (ASG). The result is consistent with that of the devitrification of silica glass observed in the interior of the bulk glass after a heat treatment. Aluminum and calcium are detected as aggregates in the devitrification spots of NQG. It is noted that ASG, containing a comparable concentration of well-dispersed aluminum, shows a significantly lower density of brownish spots and internal devitrification spots than NQG. Thus, it is considered that the formation of the brownish spots originates from the devitrification of silica glass caused by aggregates of impurities.
A Modified Capacitance–Voltage Method Used for Leff Extraction and Process Monitoring in Advanced 0.15 µm Complementary Metal-Oxide-Semiconductor Technology and Beyond
Authors: Huang Heng-Sheng , Shiu Jen-Shiuan , Lin Shyh-Jye , Chou Jih-Wen , Lee Ryan , Chen Coming , Hong Gary
Published: October 2002

In this paper, an alternative approach for the extraction of effective channel length, L
eff, using a modified capacitance–voltage (C–V) method [the capacitance–ratio (C–R) method], which considers depletion effect compensation is proposed. In general, we define L
eff=L
mask-ΔL, where ΔL is the sum of the polysilicon gate lithography bias and two times the overlap length of the polysilicon gate and source/drain (S/D) extension (ΔL=L
pb+2L
ovlap). Using the modified C–V method, more consistent and reasonable L
eff data can be extracted as compared to those obtained using the newest current–voltage (I–V) method (shift and ratio method). In using the proposed C–R method, we can electrically measure the exact L
pb and L
ovlap numbers that can both be used as process monitor parameters. The within-wafer uniformities of L
eff (or ΔL), L
pb and L
ovlap have also been checked among devices of various sizes. After the L
eff is extracted, a stable S/D resistance R
sd, with V
g independence, is determined and verified using the I–V method. The parasitic capacitance C
gd is another extracted parameter that is as important as R
sd in SPICE modeling for RF complementary metal-oxide-semiconductor (CMOS) applications.
Capability of 70 nm Pattern Replication in X-Ray Lithography
Authors: Kikuchi Yukiko , Matsui Yasuji
Published: October 2002

The 70-nm-node basic patterns were replicated by X-ray lithography using a very high contrast resist UV6SL and a low contrast X-ray mask. A simultaneous replication of 70 nm isolated line and 70-nm-L/S pattern was fairly demonstrated in the gaps of 10 and 12 µm. The 80 nm dense and semidense contact hole (C/H) patterns were also successfully replicated in the same gaps. Aerial image calculation supported these experimental results. From the comparisons with F2 lithography that requires very high numerical aperture (NA), phase shift masks (PSMs), optical proximity correction (OPC), and resolution enhancement techniques (RETs) to attain the 70 nm node, it has been shown that using proximity X-ray lithography (PXL) it is much easier to realize the 70 nm node.
Microstructure and Electrical Properties of Nonstoichiometric Strontium Titanate Thin Films Grown on Platinum Electrodes
Authors: Morito Kentaro , Suzuki Toshimasa , Fujimoto Masayuki
Published: October 2002

Nonstoichiometric strontium titanate films with the Sr/Ti ratio ranging from 0.9 to 1.4 were grown on Pt electrodes fabricated on Si substrates (Pt/Ta/SiO2/Si) by the RF-sputtering method with low and high deposition temperatures (250°C and 600°C, respectively). The insulating and dielectric properties of nonstoichiometric SrTiO3 films have been studied as a function of Sr/Ti ratio. The highest dielectric constant was obtained by a SrTiO3 film with a slight excess of SrO independent of the deposition temperature; the film showed better insulating property in comparison with the stoichiometric specimen, while the insulating property of TiO2-excess SrTiO3 films, consisting of SrTiO3 crystalline phase and Ti excess amorphous phase, notably depended on the deposition temperature. The high-temperature deposition resulted in better insulative resistance.
Numerical Evaluation of the Relative Value of Dielectric Anisotropy and Order Parameter in Fluorinated Nematic Liquid Crystals
Authors: Xu Jun , Okada Hiroyuki , Sugimori Sigeru , Onnagawa Hiroyoshi
Published: October 2002

A numerical evaluation of physical constants in the fluorinated liquid crystals has been investigated. The molecular parameters, such as dipole moment and polarizability, were calculated using a semiempirical molecular orbital method. In order to evaluate the temperature dependence of the value “dielectric anisotropy divided by order parameter (Δε/S)”, the Maier-Meier theory was used. The temperature dependence of Δε/S in these phenylbicyclohexane compounds has been explained.
Improvement of Efficiency of Ultraviolet Radiation in a Plasma Display Panel with a Complex Buffer Gas
Authors: Hashiguchi Seishiro , Tachibana Kunihide
Published: October 2002

Discharge in an opposed discharge-type ac plasma display panel cell was analyzed with a one-dimensional fluid model. The present study used helium, neon, argon and some combination of them as a buffer gas which was added to xenon gas. Calculation was performed for a sequence of pulses of sustaining voltage after applying a writing voltage. The composition of Ne/Ar buffer gas with Ne:Ar=1:3 gave the highest efficiency of Ultraviolet radiation. It was 1.6 times as large as the efficiency of simple neon buffer gas for 10%Xe. The efficiency increased with increasing fraction of xenon but the region of stable discharge decreased in size with increasing fraction of xenon.
End-point Detection of Reactive Ion Etching by Plasma Impedance Monitoring
Authors: Kanoh Masaaki , Yamage Masashi , Takada Hiroyuki
Published: October 2002

For the practical application of end-point detection of etching using plasma-impedance monitoring, the factors determining the impedance were clarified using an electric circuit model of a reaction chamber. In the model, plasma is approximated by a conductor, and the floating capacitance and wafer of a powered electrode, as well as the powered-electrode sheath (the sheath formed between the plasma and powered electrode), are approximated by capacitors. Calculated values obtained using the model agree well with measured values obtained by an impedance monitor installed between the powered electrode and the matching network. Based on this result, it was inferred that the impedance depends on the powered-electrode sheath-voltage and electron density, as well as on the floating capacitance and area of the powered electrode, the dielectric constant and thickness of the wafer, and the electron temperature. Next, the end-point detection method of etching by impedance monitoring was applied to reactive ion etching of SiO2 films, and the following finding was confirmed: the change in the impedance significantly depends on the RF power and the exposed area ratio (the ratio of etched area to wafer area) on the wafer. In addition, the feasibility of detecting the point of change of the exposed area ratio on the wafer, where the area size varies during etching, by detecting microchanges in the impedance, was demonstrated. As a result, the possibility of highly accurate end-point detection of etching by impedance monitoring was confirmed.
Trapping of Micrometer Size Bubbles by Ultrasonic Waves
Authors: Yamakoshi Yoshiki , Koshiba Masaru , Ozawa Yoshiyuki , Masuda Nobuyuki
Published: October 2002

An ultrasonic trapping method of small objects is applied to micrometer size bubbles. The experiments are carried out using an ultrasonic contrast agent of mean diameter 1.3 µm. An ultrasonic focused wave of opposite phase with frequency 5 MHz is applied to produce sequential traps for the microbubble flow. It is found that the microbubbles aggregate forming large masses of bubbles which are trapped inside the ultrasonic wave field. The effects of viscosity of the surrounding liquid are also examined.
Near-Field Optical Simulation of Super-Resolution Near-Field Structure Disks
Authors: Nakano Takashi , Yamakawa Yuzo , Tominaga Junji , Atoda Nobufumi
Published: October 2002

We describe the optical properties of readout signals from light-scatting-center super-resolution near-field structure disks by a numerical simulation using a three-dimensional finite-difference time-domain method (FDTD). Since the generation process of the near-field readout signals has a relationship between the direction of the mark train and the polarization direction of incident light, the optical properties of readout near-field signals strongly depended on the incident light polarization. It was found that the land & groove structure, and the scattering center size also influenced the readout signals.
Imaging of Digital Versatile Rewritable Disc using the Reflection-Mode Scattering-Type Scanning Near-Field Optical Microscope
Authors: Yamaguchi Mitsushiro , Sasaki Yasuo , Sasaki Hiroko , Konada Takeshi , Ebina Atsushi , Umezawa Tomokazu , Horiguchi Tohru
Published: October 2002

Recording marks written on the digital versatile rewritable disc (so called DVD-RAM) by a blue violet laser diode were observed using a reflection-mode scattering-type scanning near-field optical microscope (RS-SNOM) for the first time. The RS-SNOM is based on the atomic force microscope (AFM) and thus both the AFM and SNOM observations are simultaneously performed. In the AFM image, the land/groove structure was clearly observed and no other contrast appeared, while in the SNOM image, the 180-nm-long recording marks were clearly observed at the position of the groove. The contrast originated from the difference in the refractive index, faithfully traced in the SNOM image with a resolution of 50 nm. This result indicates that the RS-SNOM can be used as an observation tool for the next-generation high-density optical media.
The 4.7 GB Recordable Digital Versatile Disc (DVD-R) for Multiple Speed Recording
Authors: Suzuki Yuki , Ookijima Yuuko , Takeshima Hideharu , Maeda Shuuichi
Published: October 2002

We studied the characteristics of the 4.7 GB recordable digital versatile disc (DVD-R) with high-speed recording up to 4X (14 m/s) speed. We demonstrated that metal-azo dyes with either a small amount of heat generation or the low absorption show good recording characteristics, and also indicated the write pulses suitable for multiple speed recording.
Phase-Change Media for High-Numerical-Aperture and Blue-Wavelength Recording
Authors: Borg Herman J. , van Schijndel Mark , Rijpers Jan C. N. , Lankhorst Martijn H. R. , Zhou Guofu , Dekker Martijn J. , Ubbens Igolt P. D. , Kuijper Maarten
Published: October 2002

We have studied the feasibility of doped eutectic SbTe alloys for practical application in digital video recording (DVR) rewritable phase-change media for high-numerical-aperture (NA=0.85) and blue-wavelength (λ=405 nm) recording. Remaining issues such as thermal cross-erase in land/groove recording and the thermal stability of recorded amorphous marks have been investigated and resolved. This work has resulted in the realisation of 22.5 GB phase-change media complying with the DVR blue format. The future of doped eutectic SbTe alloys in the phase-change recording-speed race is also promising, as the crystallisation speed and archival life stability can be optimised more or less independently by tuning the Sb/Te atomic ratio and adding Ge, respectively. We have demonstrated that a user data transfer rate of 70 Mbit/s (DVR double speed) is within reach using our current phase-change composition, and are expecting to realise data rates of over 100 Mbit/s in the near future.
A Feasibility Study of Writing Compensation for Tangential Tilt
Authors: Lee Kyung-Geun , Joo Seong-Sin , Otsuka Tatsuo , Kim Yoon-Gi , Park In-Sik , Shin Dong-Ho
Published: October 2002

For achieving a higher density than that of current digital versatile discs(DVD), a high numerical aperture(NA) and blue wavelength light source is tested to increase the areal density. In contrast to this positive effect, the coma aberration is doubled with a NA of 0.65 and wavelength of 400 nm compared to that of the current rewritable DVD at the same disc tilt. Additionally, the effective power density for recording is much smaller than that in the case of a DVD with a tilt. In this paper an efficient compensation method for disc tilt will be presented.
Radial Tilt Detection Using One Beam and Its Compensation in a High-Density Read Only Memory
Authors: In Ma Tae-Yong Doh , Ho Choi Byoung , Sik Park In , Sam Chung Chong , Jung Kim Yong-Hoon Lee , Ho Shin Dong
Published: October 2002

To increase the capacity of the optical disc, the shortening in the wavelength of the laser diode and the increase of the numerical aperture of the lens have been attempted for several years. Unfortunately, the efforts have generated adverse effects of comatic aberration caused by disc tilt. To solve this problem, a few detection and compensation methods of disc tilt have been proposed for random access memory (RAM) discs. However, no clear approach has been taken yet in the case of read only memory (ROM) disc. In this paper, we propose a method to detect the radial tilt in a high-density ROM disc using differential phase detection (DPD) signals generated by an 8 divided photodetector. The developed radial tilt servo with a 3-axis lens actuator compensates the detected radial tilt. Its effects on the tracking servo which arise when the actuator rotates are introduced. Finally, the feasibility of the proposed method is verified through experiments on a high-density ROM.
Optical Pickup Feeding Velocity Profile Design of Optical Disk Storage
Authors: Ho Park Juhn , Joon Lee Heui-Sik Seo , Byunghoon Min Byunghoon Min , Heuigi Son Heuigi Son
Published: October 2002

Residual vibrations and jerks of a pickup body caused by the flexibility of an optical pickup feeding system in optical disk storage may degrade the quality of reading and writing, and increase the track access time. In this study, a feeding velocity profile that suppresses the residual vibrations and jerks is calculated and applied to a stepping-motor-driven feeding system. The calculated feeding velocity profile shows good results compared to the conventional feeding velocity profile of trapezoidal shape.
Force Characteristics of Slim Pickup Actuator to Improve Actuating Performances
Authors: Hong Sam-Nyol , Choi In-Ho , Kim Young-Joong , Suh Min-Suk , Kim Jin-Yong
Published: October 2002

Recently, there has been a trend to lower the tilt margin in multifunctional rewritable optical disk drives and many attempts have been made to construct a servo system to compensate the tilt in such devices as compact disk-rewritable (CD-RW) or digital versatile disk-random access memory (DVD-RAM) drives in view of rewritable disks. However, in the slim-type drives for Notebook PCs, it is very difficult to realize mechanisms for tilt servo without accompanying impairment of the gain property, due to spatial constraints. In this paper, we suggest a method of controlling the driving force to diminish the variance of mechanical tilt over the entire movable range of wire-spring-suspension-type actuators, and propose a process for precise analysis of driving force. In addition, based on the results of force analysis, we present the conditions that minimize the phase disturbance in subsidiary resonances which have adverse effects on the servo performance of slim-type pickup actuators.
Optical Recording Using High Numerical-Aperture Microlens by Plasma Etching
Authors: Kouchiyama Akira , Ichimura Isao , Kishima Koichiro , Nakao Takashi , Yamamoto Kenji , Hashimoto Gakuji , Iida Atsushi , Osato Kiyoshi
Published: October 2002

We propose the use of a high numerical-aperture (NA) microlens formed by plasma etching for an optical recording application. It was found through optical recording experiments that a microlens formed by plasma etching is applicable to a tiny objective lens.
Fabrication of Very Small Aperture Laser (VSAL) from a Commercial Edge Emitting Laser
Authors: Chen Fang , Zhai Jinhui , Stancil D. D. , Schlesinger T. E.
Published: October 2002

In this paper we report a method for producing very small aperture lasers (VSALs) from low-cost, commercial index guided edge emitting diode lasers. The detailed fabrication procedure is provided and the VSALs are characterized. Both high power and high aperture power to background noise power ratio are obtained even with a small aperture. This fabrication method can be applied to most commercial diode lasers without knowledge of the detailed geometry and is highly reproducible.
A Study on the Read/Write Experimental Results for a High-Definition Digital Video Disc Recorder using Blue-Laser Diode
Authors: Aoki Ikuo
Published: October 2002

At present, tape media are mainly used for video recording globally. However, in the near future, disc media will come into general use, as they possess many strong points compared with tape media. Thus, we are now researching the development of a high-definition digital video disc recorder with high capacity, high data transfer rate, and low cost. Our target specifications are 15 GB to 18 GB, and over 35 Mbps, using a 120 mm phase change disc and a blue-laser diode. To confirm that it is possible, numerous sample discs were manufactured and experiments were carried out. We succeeded in obtaining good experimental results. In this study, we demonstrate the possibility of realizing a high-definition digital video disc recorder using a 120 mm phase change disc and a blue-laser diode without using a disc cartridge or any extraordinary method that increases the cost.
Ordering and Electronic Properties of Self-Assembled Si/Ge Quantum Dots
Authors: Brunner Karl , Abstreiter Gerhard
Published: October 2002

We have combined Ge island nucleation during molecular beam epitaxy in the Stranski-Krastanow growth mode with step bunching in Si/SiGe multilayers on vicinal Si substrates in order to realize self-ordered arrays of nanostructures. Surface steps and the local strain fields surrounding strain-relaxed SiGe nanostructures influence the island nucleation and result in spatially ordered stable arrays of Ge dots. The controlled formation of vertically correlated stacks of wires, dots or dots on wires by such self-ordering processes offer novel functionality for future applications like infrared detectors and memories. The fundamental electronic and optical properties of self-assembled Ge dots embedded in Si are analyzed by photoluminescence, admittance and intra valence band photocurrent spectroscopy.
Strain Relaxation of Self-Assembled InAs/GaAs(001) Quantum Dots Observed by Reflection High-Energy Electron Diffraction
Authors: Takashi Hanada Takashi Hanada , Hirofumi Totsuka Hirofumi Totsuka , Takafumi Yao Takafumi Yao
Published: October 2002

Strain relaxation of self-assembled InAs quantum dots on GaAs (001) surface was investigated by in situ reflection high-energy electron diffraction (RHEED) during molecular-beam epitaxy (MBE). Relaxed atomic structures of a dot, wetting layer and substrate system were calculated for several shapes and sizes of dots using the Stillinger-Weber strain potential. The surface-parallel lattice parameter averaged in each atomic layer of the dot increases from the bottom layer to the top layer. A scale invariance of the strain distribution was found for the typical InAs-dot sizes when the shape of the dot is fixed. By taking into account the attenuation of an electron beam it was shown that the variation of the mean lattice parameter of the dots measured by RHEED depends mainly on the dot coverage (area density of atoms in all dots) and the height/diameter ratio of the dots.
Fabrication of GaAs Quantum Dots on a Bilayer-GaSe Terminated Si(111) Substrate
Authors: Keiji Ueno Keiji Ueno , Koichiro Saiki Koichiro Saiki , Atsushi Koma Atsushi Koma
Published: October 2002

We have developed a novel method to fabricate self-assembled quantum dots (QDs) of compound semiconductors on a Si(111) substrate using the so-called `droplet epitaxy' technique. In order to fabricate QDs on a Si substrate by droplet epitaxy, we examined the termination of a Si (111) surface with a bilayer-GaSe. This surface is formed by depositing 1 monolayer Ga on a Si(111)-7×7 surface and annealing in a Se flux at 520°C. Then Ga atoms are deposited to form Ga droplets on this surface, and the sample is annealed in an As flux to transform Ga droplets into GaAs QDs. It is revealed that GaAs QDs with a diameter as small as 10 nm and a height of 5 nm can be formed on the bilayer-GaSe/Si(111) substrate at a maximum density of 8.4×1010 cm-2. Using this method a new technique will be available to fabricate QDs of many kinds of compound semiconductors on the Si(111) substrate.
Theoretical Analysis of Charge Confinement in Metal Microclusters
Authors: Tadatsugu Hoshino Tadatsugu Hoshino , Mineko Hirokami Mineko Hirokami , Masayuki Hata Masayuki Hata , Minoru Tsuda Minoru Tsuda
Published: October 2002

Quantum chemical calculations have been performed to investigate changes in total energy and charge population of metal microclusters under various conditions for electric charging. This information would be helpful in the design of single-electron devices in which charge confinement in a quantum dot is essential to achieve device action. Total energies suggest that storage of electric charge is allowed within ±2e at normal device voltage for an Al169 cluster whose diameter is 3.8 nm in the planar structure. Less charge confinement (±e) is permitted for smaller cluster size. Charge populations show a difference between atoms located at the inner and outer parts of the cluster. The total amount of electrons in the inner part is almost constant in spite of the variation of electric charging conditions. In contrast, the outer part is significantly involved in storing or releasing electrons.