bluuebunny/crossref_metadata_2025 huggingface dataset:
Generation and Evaluation of a 1020 W/cm2 Intensity by Focusing Wavefront Corrected 100 TW, 10 Hz Laser Pulses
Authors: Akahane Yutaka , Ma Jinglong , Fukuda Yuji , Aoyama Makoto , Kiriyama Hiromitsu , Inoue Norihiro , Tsuji Koichi , Nakai Yoshiki , Yamamoto Yoichi , Sheldakova Julia V. , Kudryashov Alexis V. , Yamakawa Koichi
Published: September 2005

An improvement of laser-focused peak intensity has been achieved in a JAERI 100 TW Ti:sapphire chirped-pulse amplifier chain with a feedback-controlled adaptive optics system. Measurements of optical parameters of the laser pulse and an experimental tunneling ionization ratio of a rare gas atom with laser energy scaling have practically confirmed an ultrarelativistic intensity of over 1020 W/cm2 operating at a 10 Hz repetition rate.
Excitation-Power Dependence of Free Exciton Photoluminescence of Semiconductors
Authors: Shibata Hajime , Sakai Masamichi , Yamada Akimasa , Matsubara Koji , Sakurai Keiichiro , Tampo Hitoshi , Ishizuka Shogo , Kim Kyoung-Kook , Niki Sigeru
Published: September 2005

We have derived an analytical formula for the excitation-power dependence of the free exciton photoluminescence (PL) intensity. It has been found that the PL intensity I depends on the power of the excitation laser L as I∝L

k
, where k is the power index. We have deduced the analytical formula that describes the value of k for the free exciton PL emission under the above-band-gap excitation conditions. The results indicate that the value of k is in the region of 1<k<2 depending on both the value of L and material properties such as radiative and competitive nonradiative recombination probabilities.
Effect of Li Substitution on the Piezoelectric Properties of Potassium Sodium Niobate Ceramics
Authors: Matsubara Masato , Yamaguchi Toshiaki , Kikuta Koichi , Hirano Shin-ichi
Published: September 2005

(K,Na,Li)NbO3 (KNN) ceramics with 0.38 mol % K5.4Cu1.3Ta10O29 (KCT) have been prepared by a solid state reaction and their electrical properties were examined. The Curie temperature of (K,Na,Li)NbO3 increased with increasing Li substitution in both the Na and K sites. The 6 mol % Li-substituted sample showed a tetragonal phase at room temperature. Furthermore, a 1–2 mol % Li substitution for Na or K in (K0.5Na0.5)NbO3 improved several of its electrical properties. Most importantly, (K0.49Li0.01Na0.5)NbO3 attained high k
p and Q
m values of 0.43 and 2000, respectively. The value of the field-induced strain was also increased by substituting Li into (K0.5Na0.5)NbO3. The piezoelectric constant d
33 of (K0.5Li0.02Na0.48)NbO3 was approximately 200 pm/V, which was calculated from the slope of the field-induced strain curve at 30–40 kV/cm under a unipolar driving field.
A Method to Determine the Higher Order Polar Anchoring Coefficients for the Non-Twisted Liquid Crystal Cells
Authors: Hsu Jy-Shan , Hsieh Mei-Chi , Yang Chia-Leng , Liang Bau-Jy , Chen Shu-Hsia
Published: September 2005

We propose a method to determine the higher order polar anchoring coefficients for the non-twisted liquid crystal cells. The surface anchoring energy density was determined by measuring the phase retardations as a function of applied voltage. We extended the Rapini–Papoular model and obtained the coefficients of the first and the second terms by analyzing the measured phase retardations with the simulated curves for the homogeneous and homeotropic cells. A discussion of the experimental results is given.
Relationship between Average Cation Radii and Oxygen Parameter for Various Oxides with Spinel-Type Structure
Authors: Yokoyama Takashi , Meguro Takeshi
Published: September 2005

For the relationship among lattice constant (a), average cation radii, and oxygen parameter (u) in oxides with a spinel structure, a theoretical equation is derived as u=(r
A-r
B)/{(1+√3)a}+1.058/(1+√3). Here, r
A is the average cation radius at tetrahedral sites, and r
B is the average cation radius at octahedral sites in a spinel structure. This equation means that u is expressed as a linear function of (r
A-r
B)/a. In this study, the validity of the above equation was comprehensively investigated using various values based on the cation distributions containing the u parameter reported by other researchers. The cation radii reported by Shannon were applied. As a result, the plotted points were found to lie almost on the theoretical line, although the points were concentrated in a local region. Therefore, it was concluded that the reported values of u and the average radii calculated on the basis of the cation distributions are generally reasonable.
Temperature-Dependent Photoluminescence of Highly Strained InGaAsN/GaAs Quantum Wells (λ= 1.28–1.45 µm) with GaAsP Strain-Compensated Layers
Authors: Lai Fang-I , Kuo Hao-Chung , Chang Ya-Hsien , Tsai Min-Ying , Chu Chia-Pu , Kuo Shou-Yi , Wang Shing-Chung , Tansu Nelson , Yeh Jeng-Ya , Mawst Luke J.
Published: September 2005

The effects of nitrogen incorporation into the In0.4Ga0.6As1-x
N
x
/GaAs single quantum wells (SQWs), where x = 0.5 and 2%, grown on GaAs substrates by metalorganic chemical vapor deposition (MOCVD) were investigated using photoluminescence (PL) and high-resolution transmission electron microscopy (HRTEM). The evolution of the excitation-dependent PL and PL-peak position with temperature between 10 and 300 K shows that quantum-dot-like states occurred at that high nitrogen incorporation (x = 2%) and were confirmed by an HRTEM image which showed small dark regions about 2–3 nm in size was found in the interface of In0.4Ga0.6As0.98N0.02 and GaAs. Our investigations indicate that high nitrogen incorporation into the In0.4Ga0.6As1-x
N
x
/GaAs system influenced carrier localization and might cause the formation of the dot-like states.
Scanning Tunneling Microscopy Observation of Graphite Surfaces Irradiated with Size-Selected Ar Cluster Ion Beams
Authors: Houzumi Shingo , Mochiji Kozo , Toyoda Noriaki , Yamada Isao
Published: September 2005

A cluster ion irradiation system with cluster size selection has been developed to study the effects of the cluster size in surface processing using cluster ions. A permanent magnet with a magnetic field of 1.2 T was installed for size separation of large cluster ions. Traces formed on a graphite surface by the impact with Ar cluster ions under an acceleration energy of 30 keV were investigated by scanning tunneling microscopy. The nature of the traces is strongly affected by the number of constituent atoms of the irradiating cluster ion. When the cluster ion is composed of 100–3000 atoms, crater like traces are observed on the irradiated surfaces. In contrast, such traces are not observed at all with the irradiation of the cluster ions composed of over 5000 atoms. This behavior is discussed on the basis of the kinetic energy per constituent atom of the cluster ion.
Sputter Depth Profiling of Multiple Short-Period BN δ-Doped Si by Work Function Measurement
Authors: Mizuhara Yuzuru , Bungo Takuya , Nagatomi Takaharu , Takai Yoshizo
Published: September 2005

Sputter depth profiling of multiple short-period BN δ-doped Si on the basis of work function (WF) measurement using the secondary electron (SE) method was investigated. The concentration of boron in the sample was confirmed to be less than the detection limit of the current Auger electron spectroscopy system. The results revealed that BN δ-doped layers can be detected as a periodic change in the WF of the order of ∼0.01 eV. These results confirmed that sputter depth profiling on the basis of WF measurement using the SE method is effective for the characterization of dopant atoms in semiconductor devices with high lateral and depth resolutions.
Semiautomatic Protein Crystallization System Featuring Crystallization Solution Preparation Function
Authors: Adachi Hiroaki , Matsumura Hiroyoshi , Inoue Tsuyoshi , Niino Ai , Takano Kazufumi , Murakami Satoshi , Mori Yusuke , Sasaki Takatomo
Published: September 2005

We previously developed a simple, semiautomatic protein crystallization system, the automatic system of crystallization (TASCAL-1), for first crystallization screening. Our new and improved system, TASCAL-2, not only provides its benefits, but is also capable of preparing crystallization solutions for secondary crystallization screening. TASCAL-2 is desktop sized and is controlled by newly developed software in a Windows-based operating system on a personal computer for ease of operation and increased productivity.
π Channel Effects in Transport Properties of Al Nanowires at Finite Biases
Authors: Asari Yusuke , Nara Jun , Kobayashi Nobuhiko , Ohno Takahisa
Published: September 2005

We present the first-principles investigations on π channel effects in electron transport properties of Al monatomic wires. By the eigenchannel decomposition technique, the transport properties are compared between three-atom and five-atom wires, sandwiched between two semi-infinite jellium electrodes. In the presence of finite bias voltages, σ channel current shows a linear bias dependence independent of wire length. In contrast, π channel current shows nonlinearity in the five-atom wire, while it depends on bias voltage almost linearly in the three-atom wire. We have clarified that nonlinear I–V characteristics of the five-atom wire are induced due to the effect of π channels in the ballistic transport regime.
Effects of Photoresist Polymer Molecular Weight and Acid-Diffusion on Line-Edge Roughness
Authors: Patsis G. P. , Gogolides E. , Werden K. Van
Published: September 2005

Important factors contributing to line-edge roughness (LER) of chemically amplified resists are, among others, acid diffusion, and photoresist polymer molecular weight (M
W). Their effects on the final LER are combined and simulations indicated that acid diffusion can be the major LER modifying factor. Acid-diffusion increases LER overall in a chemically amplified resist in comparison with a conventional one under the same deprotection fraction. In addition, extremely high values of acid-diffusion range can result in smaller LER for higher M
W polymers. Under normal acid diffusion conditions, the effect M
W on LER is seen to be of secondary importance. Explanations are given based on the critical ionization model for the resist film dissolution, and experimental verification is done with top-down scanning electron microscope (SEM) images for extreme-ultraviolet lithography (EUVL) photoresist.
Device Simulations in Coupled Floating-Gate Memories
Authors: Tanamoto Tetsufumi , Ohba Ryuji , Yasuda Shin-ichi , Abe Keiko , Fujita Shinobu
Published: September 2005

Two device simulations were carried out to investigate the possibilities of nano sized floating-gate memories. In the first simulation, we calculated the characteristics of coupled floating-gate devices based on a conventional simulator. We found that the memory performance is improved by coupling two floating gates. In the second simulation, we showed the possibility of using a quantum well structure embedded in the conventional floating-gate device and demonstrated that the resonant tunneling phenomenon is available in the Si/SiO2 system when it is coupled with conventional floating gates. We also established that high-k materials are useful in improving device performance. Both are suitable candidates for nano sized very large scale integration (VLSI) devices.
Effect of Nitrogen Incorporation into InAs layer in InAs/InGaAs Self-Assembled Quantum Dots
Authors: Chen Jenn-Fang , Hsiao Ru-Shang , Chen Yu-Chih , Chen Yi-Ping , Hsieh Ming-Ta , Wang Jyh-Shyang , Chi Jim-Y
Published: September 2005

We present the results of nitrogen incorporation into the InAs layer in InAs/InGaAs quantum dots (QDs). We show that this incorporation causes an asymmetric photoluminescence (PL) line shape and abnormally large redshift of the PL peak from the quantum dots as temperature increases. In addition, this incorporation causes a large series resistance and a rapid increase in reverse current at a bias corresponding to the QD region. This effect is due to the formation of a deep trap at 0.34–0.41 eV, which depletes the carriers in the QD region. This depletion gives rise to a geometric resistance-capacitance time-constant effect for the ac conductivity of the free electrons in the top GaAs layer. This trap markedly alters the emission properties of the QD structure. The ac conductivity of the QD structure is governed by the thermal activation of trapped electrons rather than the electron emission from the QD confined states. This incorporation significantly increases the electron emission time from the QD region and, thus, can be used intentionally to modify the emission properties of the QD structure.
Characterization of InP/InGaAs Heterojunction Bipolar Transistors with Carbon-Doped Base Layers Grown by Metal-Organic Chemical Vapor Deposition and Molecular Beam Epitaxy
Authors: Kuroda Naotaka , Fujihara Akira , Ikenaga Yoshifumi , Ishizaki Haruya , Tanaka Shinichi
Published: September 2005

We characterized InP/InGaAs heterojunction bipolar transistors (HBTs) with carbon-doped InGaAs base layers grown by metal-organic chemical vapor deposition (MOCVD) and molecular beam epitaxy (MBE). Since HBTs grown using these techniques require different processing steps, resulting in different types of process-related damage, we analyzed the bulk and periphery components of DC characteristics to clarify the effects of the crystal growth and process techniques on device characteristics separately. The MBE-grown HBTs were found to have an advantage over the MOCVD-grown HBTs, because they do not require harmful high-temperature annealing during processing steps. On the other hand, it was also shown that the MOCVD-grown HBTs have a significantly lower base recombination rate than the MBE-grown HBTs, making MOCVD a suitable method of growing InP HBTs that do not require annealing, such as that with a GaAsSb base.
Fabrication of Co2MnAl Heusler Alloy Epitaxial Film Using Cr Buffer Layer
Authors: Sakuraba Yuya , Nakata Jun , Oogane Mikihiko , Kubota Hitoshi , Ando Yasuo , Sakuma Akimasa , Miyazaki Terunobu
Published: September 2005

Thin films of the full-Heusler compound, Co2MnAl, were grown on Cr-buffered MgO(001) substrates at different growth temperature and post-annealing temperature by magnetron sputtering. Atomic force microscopy (AFM) and X-ray diffraction (XRD) measurements show that Cr-buffer layer can largely improve the surface morphology and structural quality of Co2MnAl film. The (001)-oriented epitaxial growth and B2 structure were confirmed by XRD measurements for all prepared samples. The smallest surface roughness (∼2 Å) and an identical M
s value to the bulk value were obtained in the sample which was deposited at ambient temperature and post-annealed at 300°C.
Plug & Play Quantum Key Distribution Using Modulation Sidebands for Shifting Frequency
Authors: Honjo Toshimori , Inoue Kyo
Published: September 2005

A Plug & Play quantum key distribution (QKD) system operating at a high pulse repetition frequency is presented. To avoid Rayleigh backscattering, modulation sidebands are used as frequency-shifted light. As the pulse repetition frequency increases, the quantum bit-error rate (QBER) in our proposed setup remains constant, while it increases in a conventional setup, which indicates that Plug & Play QKD at a high repetition frequency is possible with our scheme.
Cell Gap-Dependent Transmittance Characteristic in a Fringe Field-Driven Homogeneously Aligned Liquid Crystal Cell with Positive Dielectric Anisotropy
Authors: Kim Seung Jai , Kim Hyang Yul , Lee Seung Hee , Lee Yong Kyun , Park Kyu Chang , Jang Jin
Published: September 2005

Transmittance characteristic in a homogeneously aligned liquid crystal (LC) cell driven by a fringe-electric field is investigated as a function of cell gap using the LC with positive dielectric anisotropy. In this device, the fringe-electric field drives the LCs to rotate so that the dielectric torque is electrode-positional dependent, which results in electrode-position dependency in the LC's rotating angle. As the cell gap decreases to 2 µm, more LCs are affected by surface anchoring, and the LCs above the center of electrodes, in which the LCs are twisted by elastic force between neighboring molecules, are less twisted compared to the 4 µm cell. Consequently, when the cell gap decreases from 4 to 2 µm, the transmittance also decreases even though the cell retardation value remains the same.
Optical Cyclic Wavelength Shifter Using a Dual-Band Polymer Holographic Grating
Authors: Chung Seunghwan , Han Seunghoon , Kim Taesu , Lee Byoungho
Published: September 2005

We propose a cyclic wavelength shifter, that can be applied to optical networks or code-division multiple access (CDMA) systems. The shifter is based on a dual-band polymer holographic grating and operated by applying strain or rotation. Using this device, constant-weight cyclically permutable codes in various CDMA systems might be implemented easily compared with using other optical methods.
Fiber Bragg Grating-Based Multiplexed Sensing System Employing Fiber Laser Scheme with Semiconductor Optical Amplifier
Authors: Yeh Chien-Hung , Lin Ming-Ching , Lee Chien-Chung , Chi Sien
Published: September 2005

We propose and demonstrate experimentally a multipoint fiber Bragg grating (FBG) sensor system, based on fiber Bragg gratings (FBGs), using a semiconductor optical amplifier (SOA) as a gain medium. Multiple wavelength operation is based on the inhomogeneous broadening effect of the SOA of the sensing system. In addition, the behavior of the proposed sensor configuration is also studied.
Emission Mechanism of Double-Insulating Organic Electroluminescence Device Driven at AC Voltage
Authors: Lee Sang-Bong , Fujita Katsuhiko , Tsutsui Tetsuo
Published: September 2005

We demonstrate charge recombination electroluminescence (EL) that is observed without charge injection from external electrodes in double-insulated organic EL devices. Double-insulating organic thin-film (EL) devices, indium–tin–oxide electrode (ITO)/polymer insulator layer/ambipolar EL layer/ITO or gold nanoparticles layer/ambipolar EL layer/polymer insulator layer/Al electrode, were fabricated. The ambipolar EL layer was made of a poly(N-vinylcarbazole) (PVK)/2.5-bis(4-naphthyl)-1,3,4-oxadiazole (BND)/coumarine-6 film or a poly-(2-methoxy-5-(2-ethylhexyloxy)-1.4-phenylenevinylene) (MEH-PPV) film. For the polymer insulating layer, a poly-4-vinylphenol (PVP) film, which was formed via spin coating from a 2-propanol solution, was used. ITO nanoparticles and thiol-passivated gold nanopartilces were used as ambipolar charge generation materials. When the devices were driven at ac voltage, a uniform surface emission was observed. Experimental results showed that this emission is due to the recombination of holes and electrons that are generated from ITO or gold nanoparticles embedded in organic layers.
Synthesis and Microwave Dielectric Properties of La2O3–xB2O3-Based Melt Mixtures for Low-Temperature Cofired Ceramics
Authors: Takada Takahiro , Kageyama Keisuke
Published: September 2005

La2O3–xB2O3-based melts were fabricated. Two kinds of melts, crystalline at x=2 and amorphous at x=3 with ZnO additions, were obtained. The microwave dielectric properties and microstructure of the ceramics prepared from the melts and calcined La2O3–B2O3 were investigated. Several mixtures of 50 wt % melts and 50 wt % calcined powder were fireable around 900°C, which was a low firing temperature for cofiring with a low-loss conductor. Among them, the dielectric properties for a fired mixture of 50 wt % La2O3–2B2O3–0.5ZnO melt and 50 wt % calcined powder showed an fQ value of about 30000 GHz and ε
r=9–10 at 13 GHz. 5 wt % crystalline additives fired at 925°C, which have the same composition as the host ceramic material, increased fQ to 63000 GHz. The mixtures of 20–80 wt % crystalline melt and 80–20 wt % amorphous melt were also sinterable below 900°C. The best dielectric properties, fQ=72000 GHz and ε
r=8 at 13 GHz, with low firing temperatures were exhibited when the mixing ratio was 20 wt % crystalline melt and 80 wt % amorphous melt. The green sheet, which contained two kinds of melts, could be cofired with Ag at 900°C.
Effects of Ce, Cr and Er Doping and Annealing Conditions on the Microstructural Features and Electrical Properties of PbZrO3 Thin Films Prepared by Sol–Gel Process
Authors: Alkoy Ebru Mensur , Alkoy Sedat , Shiosaki Tadashi
Published: September 2005

Lead zirconate (PbZrO3) thin films doped with Ce, Cr and Er were grown on Pt(111)/Ti/SiO2/Si(100) substrates by sol–gel spin coating process. Polycrystalline films with a phase-pure perovskite structure and a random orientation were obtained regardless of doping materials. Microstructural examinations of the films revealed a two-phase microstructure consisting of large rosette-type perovskite regions with a nanocrystalline phase located in between. Perovskite rosettes were found to be of polycrystalline in nature with grain size ranging between 50–250 nm. Increasing number of annealing cycles and temperature were found to improve the microstructure, crystallinity and electrical properties. Doping elements were also found to increase electrical properties with a saturation polarization (P
sat) reaching 65 ×10-6 C/cm2 in Ce- and Cr-doped coatings compared to 39 ×10-6 C/cm2 for undoped PZ films.
Cell Dynamics Simulation of Kolmogorov–Johnson–Mehl–Avrami Kinetics of Phase Transformation
Authors: Iwamatsu Masao , Nakamura Masato
Published: September 2005

In this study, we use the cell dynamics method to test the validity of the Kormogorov–Johnson–Mehl–Avrami (KJMA) theory of phase transformation. This cell dynamics method is similar to the well-known phase-field model, but it is a more simple and efficient numerical method for studying various scenarios of phase transformation in a unified manner. We find that the cell dynamics method reproduces the time evolution of the volume fraction of the transformed phase predicted by the KJMA theory. Specifically, the cell dynamics simulation reproduces a double-logarithmic linear KJMA plot and confirms the integral Avrami exponents n predicted from the KJMA theory. Our study clearly demonstrates that the cell dynamics approach is not only useful for studying the pattern formation but also for simulating the most basic properties of phase transformation.
Stability of Azobenzene-Containing Polyimide Film to UV Light
Authors: Usami Kiyoaki , Sakamoto Kenji , Uehara Yoichi , Ushioda Sukekatsu
Published: September 2005

We have investigated the stability of an azobenzene-containing polyimide (Azo-PI) film with anisotropic molecular orientation to linearly polarized light (LP-L) of wavelength 340–500 nm. The anisotropic molecular orientation was induced by exposing the corresponding polyamic acid film to LP-L of 72 J/cm2, and then the film was thermally imidized. No significant change was observed in the in-plane molecular order of the Azo-PI film over prolonged light exposure of 468 J/cm2, but a 10% decrease of the number of the Azo-PI backbone structure was observed. From these results we found that: (i) the reorientation of the backbone structure through photo-isomerization cycles of azobenzene is inhibited in the Azo-PI film; (ii) the photo-decomposition of the Azo-PI film proceeds with about 2 times the rate for a poly[4,4'-oxydiphenylene-pyromellitimide] film.
Effect of He Plasma Treatment on the Rectification Properties of Al/CdTe Schottky Contacts
Authors: Toyama Hiroyuki , Yamazato Masaaki , Higa Akira , Maehama Takehiro , Ohno Ryoichi , Toguchi Minoru
Published: September 2005

We investigated the effect of He plasma treatment on the surface composition of CdTe and the electrical properties of Al/CdTe Schottky contacts. The composition of the initial CdTe surface is Te-rich due to Br-methanol etching. When Al Schottky contacts are formed on the CdTe surfaces with the Te-rich layer, the barrier height is low and the rectification property is not good. In this paper, we propose the He plasma treatment method to remove the Te-rich layer. From X-ray photoelectron spectroscopy measurement, it was found that the plasma treatment can remove the Te-rich layer. The rectification property of the Al Schottky contacts on the plasma-treated surfaces is improved, and their barrier heights are estimated to be about 0.65 eV. In γ-ray spectrometry, a high-energy resolution of 1.6 keV full width at half maximum at 59.5 keV was obtained from the plasma-treated Al/CdTe/Pt detector. The results indicate that the plasma treatment of CdTe surfaces significantly improves the energy resolution of Schottky-type Al/CdTe/Pt radiation detectors.
Analysis of Influence of Address Electrode Width on Address Discharge Characteristics Using Threshold Voltage Closed Curve
Authors: Kim Yongduk , Park Sekwang
Published: September 2005

In order to drive high-density plasma displays, one TV field should effectively be composed of reset, address, and sustain periods and the display quality should be improved. Therefore, we must study high-speed driving technology. In this paper, we will show the relationship between the width of the address electrode and high-speed drive using the threshold voltage (V
t) closed curve and will propose the panel structure for high-speed driving. In these experiments, we will show that the wider the address electrode is, the narrower the width of the scan pulse becomes. Therefore, we could achieve the dynamic data voltage margin of 16.4 V at a scan pulse width of 0.8 µs and a ramp voltage of 220 V at an address electrode width of 180 µm for a high-speed-drive 4-in. test PDP.
Influence of Diffusion on Properties of 173 nm Light Emission from Discharge Cells in Plasma Display Panel
Authors: Uhm Han S. , Choi Eun H. , Jung Kyu B.
Published: September 2005

A simple analytical expression Y of the 173 nm emission intensity is described in terms of the diffusion loss d
f, the three-body collision η, the gas pressure p and the xenon mole fraction χ. The emission intensity Y of 173 nm photons decreases with increasing parameter d
f. Moreover, Y increases rapidly with the gas pressure p and the xenon mole fraction χ. Results from the theoretical model agree markedly well with experimental data.
Temperature-Dependent Photoluminescence of Self-Assembled (In,Ga)As Quantum Dots on GaAs (100): Carrier Redistribution through Low-Energy Continuous States
Authors: Mano Takaaki , Nötzel Richard , Gong Qian , Lippen Twan v. , Hamhuis Gerrit J. , Eijkemans Tom J. , Wolter Joachim H.
Published: September 2005

Temperature-dependent photoluminescence (PL) studies of an ensemble of self-assembled (In,Ga)As quantum dots (QDs) on GaAs (100) provide insight into the nature of the continuous states between the wetting layer (WL) and QDs. In addition to the well-known anomalous temperature dependence of the PL peak position and width around 90 K due to carrier (electron–hole pair) redistribution through the WL, we observe a similar behavior at much lower temperatures around 30 K. This behavior is attributed to carrier redistribution through the low-energy continuous states between the WL and QDs, directly proving their quasi-two-dimensional character. The smaller changes in the PL spectra than the WL-induced ones, however, indicate that the carrier redistribution and, thus, the spatial extent of the continuous states are restricted to a limited area around the QDs. This is also supported by the constant integrated PL intensity in this temperature range due to the absence of nonradiative recombination within these areas.
Azurin for Biomolecular Electronics: a Reliability Study
Authors: Bramanti Alessandro , Pompa Pier Paolo , Maruccio Giuseppe , Calabi Franco , Arima Valentina , Cingolani Roberto , Corni Stefano , Felice Rosa Di , Rienzo Francesca De , Rinaldi Ross
Published: September 2005

The metalloprotein azurin, used in biomolecular electronics, is investigated with respect to its resilience to high electric fields and ambient conditions, which are crucial reliability issues. Concerning the effect of electric fields, two models of different complexity agree indicating an unexpectedly high robustness. Experiments in device-like conditions confirm that no structural modifications occur, according to fluorescence spectra, even after a 40-min exposure to tens of MV/m. Ageing is then investigated experimentally, at ambient conditions and without field, over several days. Only a small conformational rearrangement is observed in the first tens of hours, followed by an equilibrium state.
Propagation Characteristics of Terahertz Electrical Signals on Micro-Strip Lines Made of Optically Transparent Conductors
Authors: Takase Kousuke , Ohkubo Tetsuya , Sawada Futoshi , Nagayama Daiki , Kitagawa Jiro , Kadoya Yutaka
Published: September 2005

We investigated the propagation properties of terahertz (THz) electrical pulses in micro-strip lines (MSLs) in which the signal line or the ground plane is made of indium–tin–oxide (ITO), which is a widely used transparent conductor. Finite-difference time-domain calculations showed that, in cases where ITO is used as the ground plane, an amplitude attenuation of as low as α∼0.35 mm-1 (3 dB/mm) can be realized at 1 THz. It was also found that the use of the dc value for conductivity for ITO results in a slightly larger value for the attenuation. In experiments, although the conductivity of the ITO film was not sufficiently high, clear picosecond electrical pulses were observed after 2 mm of propagation with nearly the same waveform and an amplitude only 30% smaller than those in metal-based MSLs. These results suggest that ITO can be used as a ground plane conductor in millimeter-scale MSLs in the THz range.
The Ellipsometric Measurements of a Curved Surface
Authors: Lee Kan Yan , Chao Yu Faye
Published: September 2005

A three-intensity imaging ellipsometric technique is proposed to investigate the surface topography as well as the refractive index profile (RIP) of a lens. The azimuth deviation of polarizer caused by the tilting of a SiO2 thin film on Si substrate was investigated after a careful calibration on the azimuth position of polarizer of the water-surface. The azimuth deviation of polarizer is proved to be the local surface normal; thus we can determine not only the radius of curvature of a Plano-Convex lens from the measurement, but also its incident-angle-corrected RIP.
Fiber-Optic Distributed Strain Sensing System by Brillouin Optical Correlation Domain Analysis with a Simple and Accurate Time-Division Pump-Probe Generation Scheme
Authors: Hotate Kazuo , Yamauchi Toyohiko
Published: September 2005

A simplified and accurate system of Brillouin optical correlation domain analysis for fiber-optic distributed strain sensing is proposed and demonstrated. In the system, pump and probe lightwaves, with about 11 GHz frequency difference for stimulating fiber Brillouin scattering, are generated accurately in a time-division way by using direct-frequency-modulation nature of a laser diode. We have developed a scheme for rigorously compensating frequency modulation response of the laser diode to realize accurately a rectangular frequency modulation with such large amplitude for the time-division pump-prove generation. Distribution of Brillouin gain spectrum along an optical fiber has successfully been measured, with 16 cm spatial resolution, using the waveform pre-compensated accurately for the laser frequency modulation.
Improving Boron-Induced Retardation of Metal-Induced Lateral Crystallization Length by Hydrogen Treatment
Authors: Chen Shih-Fang , Fang Yuen-Kuen , Lin Ping-Chang , Lee Tsung-Han , Lin Chun-Yu , Lin Chun-Sheng , Chou Tse-Heng
Published: September 2005

In this letter, we use hydrogen treatment to improve boron-dopant-induced growth length retardation in metal-induced lateral crystallization (MILC) of amorphous silicon film (a-Si). Compared with the case without hydrogen treatment, a scanning electron microscope (SEM) micrograph shows that the grown poly-silicon length in boron-doped a-Si film can be increased from 7 to 40 µm after 6 h of MILC annealing. The doped boron atoms generate a large number of dangling bonds, which then capture the metal atoms to interrupt the MILC processing thus retarding the growth length. Therefore, the obvious enhancement in MILC length is attributed to the passivation of dangling bonds with hydrogen atoms.
Generation of Long and High-Density Plasma Column Using Metal-Antenna Surface Wave-Excited Plasma Source
Authors: Kousaka Hiroyuki , Xu Junqi , Umehara Noritsugu
Published: September 2005

We investigated the effect of gas pressure on the length of a microwave-excited high-density plasma column sustained along a graphite rod (25 cm in length and 1.0 cm in diameter), which was negatively biased against a grounded chamber. It was confirmed that the length of the overdense (>1011 cm-3) plasma column increased with increasing gas pressure and negative voltage. At a gas pressure of 33 Pa, we obtained the longest plasma column covering the entire surface of the rod with a negative voltage of -150 V and an input microwave power of 100 W.
Growth of Fe-Doped Thick GaN Layers for Preparation of Semi-Insulating GaN Substrates
Authors: Kumagai Yoshinao , Takemoto Kikurou , Murakami Hisashi , Koukitu Akinori
Published: September 2005

Vapor-phase epitaxy of Fe-doped thick GaN layers was performed using GaCl, NH3 and FeCl2 as source gases on (0001) sapphire and (111)A GaAs substrates with the aim of preparing semi-insulating (SI) GaN substrates. On sapphire, the resistivity of the GaN layer increased with increasing FeCl2 input partial pressure. A 12-µm-thick SI GaN layer showing a resistivity of 3.0×109 Ω cm at room temperature was successfully grown by compensating for background donors. In contrast, the resistivity of the GaN layers grown on the GaAs substrate remained low (on the order of 10-2 Ω cm) even though the same growth conditions were used as on the sapphire substrate. Secondary ion mass spectroscopy (SIMS) measurements suggested that the presence of As vapor-species caused by the degradation of the substrate hindered Fe from becoming incorporated into GaN.
Polycrystalline to Single-Crystalline InN Grown on Si(111) Substrates by Plasma-Assisted Molecular-Beam Epitaxy
Authors: Hsiao Ching-Lien , Tu Li-Wei , Chen Min , Jiang Zhi-Wei , Fan Ni-Wan , Tu Yen-Jie , Wang Kwang-Ru
Published: September 2005

The structural evolution of InN from microsized grains to nanocolumns, and to a two-dimensional epifilm grown on Si(111) substrates was realized by plasma-assisted molecular-beam epitaxy. Grainy InN was grown at a higher substrate temperature, and a higher NBEP/InBEP ratio, and on a low-temperature InN buffer layer. A high-quality InN epifilm was grown at a lower substrate temperature, and a lower NBEP/InBEP ratio, and on a high-temperature AlN buffer layer with a room-temperature Hall mobility and a carrier concentration of 860 cm2/(V·s) and 8.9×1018 cm-3, respectively. Photoluminescence spectroscopy showed a unique peak in the infrared region indicating that the energy gap of the InN is in the range of 0.64–0.66 eV.
Electro-Optic Properties of Pb(Zr1-xTix)O3 (X=0, 0.3, 0.6) Films Prepared by Aerosol Deposition
Authors: Nakada Masafumi , Ohashi Keishi , Akedo Jun
Published: September 2005

We measured annealing temperature and the Zr-to-Ti concentration ratio dependence of the electro-optic (EO) effect for highly transparent Pb(Zr1-x
Ti
x
)O3 [PZT] films more than 1 µm thick, directly deposited on glass substrates by aerosol deposition (AD). X-ray diffraction patterns show that as-deposited AD films have a large strain and lattice distortions, and these affects can be attenuated by increasing annealing temperature. The dielectric constant of AD-PZT films increased with annealing temperature, which is consistent with the X-ray diffraction measurement. The EO effect was enhanced with increasing Zr concentration, and a linear EO coefficient (r
c) of 102 pm/V was obtained for the PbZr0.6T0.4O3 film annealed at 600°C, whose composition is near its morphotropic phase boundary. The r
c of PbZr0.6T0.4O3 films increased with annealing temperature, and the film annealed at 850°C showed an r
c of 168 pm/V. The EO measurements show that AD is a highly promising film-deposition method for optical devices such as EO modulators and optical switches.
Longevity of Plastic-Based Organic Light-Emitting Devices by Means of Protective Oils as Passivation Layer
Authors: Kim Gi Heon , Joung Meyoung Ju , Oh Jiyoung , Yoon Sung-Min , Suh Kyung Soo
Published: September 2005

For the encapsulation of plastic-based organic light-emitting devices (OLEDs), an inert oil as a liquid passivation layer is applied on the periphery of the device. The electroluminescence (EL) and rate of degradation of such devices are examined to compare the electrical and emissive properties of the devices before and after forming the inert liquid passivation layer. The presence of the liquid layer firmly prevents the occurrence and growth of dark spots and enhances the lifetime of the devices in air. Driven at 27.45 mA/cm2 (L
o∼1780 cd/m2), a driving lifetime of 195.0 h is achieved, which is affected by the type of inert oil used.
Huge Spin-Polarization of L21-Ordered Co2MnSi Epitaxial Heusler Alloy Film
Authors: Sakuraba Yuya , Nakata Jun , Oogane Mikihiko , Kubota Hitoshi , Ando Yasuo , Sakuma Akimasa , Miyazaki Terunobu
Published: September 2005

Magnetic tunnel junctions (MTJs) with a stacking structure of epitaxial Co2MnSi/Al–O barrier/poly-crystalline Co75Fe25 were fabricated using an ultrahigh vacuum sputtering system. The epitaxial Co2MnSi bottom electrode exhibited highly ordered L21 structure and very smooth surface morphology. Observed magnetoresistance (MR) ratios of 70% at room temperature (RT) and 159% at 2 K are the highest values to date for MTJs using a Heusler alloy electrode. A high spin-polarization of 0.89 at 2 K for Co2MnSi obtained from Julliere's model coincided with the half-metallic band structure that was predicted by theoretical calculations.
Low-Leakage Polymeric Thin-Film Transistors Fabricated by Laser Assisted Lift-Off Technique
Authors: Kim Sung-Jin , Ahn Taek , Suh Min Chul , Yu Chang-Jae , Kim Dong-Woo , Lee Sin-Doo
Published: September 2005

Organic thin-film transistors (OTFTs) based on a semiconducting polymer have been fabricated using a patterning method of the selective wettability. Laser assisted lift-off (LALO) technique, ablating selectively the hydrophobic layer by an excimer laser, was used for producing a semiconducting polymer channel in the OTFT with high resolution. The selective wettability of a semiconducting polymer, poly(9-9-dioctylfluorene-co-bithiophene) (F8T2), dissolved in a polar solvent was found to define precisely the pattering resolution of the active channel. It is demonstrated that in the F8T2 TFTs fabricated using the LALO technique, the leakage of the gate current is drastically reduced.
Metal Deposition Deep into Microstructure by Electroless Plating
Authors: Takeyasu Nobuyuki , Tanaka Takuo , Kawata Satoshi
Published: September 2005

It is generally difficult to deposit metal on an occluded part of a structure or inside a long tubular structure. In this paper, we report an electroless plating method that is useful for metal deposition onto internal obscured regions of a complex structure, and we show that the technique can deposit metal over a wide area. We demonstrate gold deposition inside a capillary tube and a complex concave structure of micrometer scale consisting of polystyrene microbeads sandwiched between glass plates.
Low-Temperature Oxidation of Silicon using UV-Light-Excited Ozone
Authors: Tosaka Aki , Nishiguchi Tetsuya , Nonaka Hidehiko , Ichimura Shingo
Published: September 2005

An ultra low-temperature (< 300°C) silicon oxidation process in which KrF excimer laser light (λ=248 nm) is irradiated in highly concentrated ozone has been developed. The growth rate of SiO2 film was 5.2 nm/10 min at 300°C and 3.6 nm/10 min at 70°C. The leakage current densities of grown at 70°C SiO2 in an electric field of over 8 MV/cm match well the calculated curve based on the Fowler–Nordheim tunneling. The oxidation mechanisms for two growth modes are discussed.
Critical Current Density Enhancement around a Matching Field in ErBa2Cu3O7-δ Films with BaZrO3 Nano-Rods
Authors: Mukaida Masashi , Horide Tomoya , Kita Ryusuke , Horii Shigeru , Ichinose Ataru , Yoshida Yutaka , Miura Osuke , Matsumoto Kaname , Yamada Kazuhiro , Mori Nobuyuki
Published: September 2005

Field angular dependences of critical current density are measured for as-grown high crystalline quality ErBa2Cu3O7-δ films with BaZrO3 nano-rods. Large critical current density enhancement is observed. The magnetic field where the enhancement is observed coincides with the matching field calculated from the density of BaZrO3 nano-rods. The largest enhancement is observed in B ∥c-axis of ErBa2Cu3O7-δ films. This anisotropic critical current density enhancement is thought to be caused by the direction of BaZrO3 nano-rods which grow along the c-axis of the films. BaZrO3 nano-rods in the films will promise the application of coated conductors in a magnetic field.
Evaluation of Attenuation Constants of Superconducting NbN Coplanar Waveguides
Authors: Yamamori Hirotake , Shoji Akira
Published: September 2005

Attenuation constants of superconducting NbN coplanar waveguides (CPWs) have been evaluated by measuring their transmission coefficients and reflection coefficients with a network analyzer. It has been found that the attenuation constant of NbN CPWs rapidly increases when their thicknesses are reduced below the penetration depth (300 nm). It has also been found that the experimentally measured attenuation constants of NbN CPWs coincide well with the numerically calculated ones.
Second Harmonic Generation of Thermally Poled ZnCl2–B2O3–TeO2 Glasses and Its Mechanism
Authors: Nasu Hiroyuki , Nagaike Yuki , Takeda Hirofumi , Hashimoto Tadanori , Kamiya Kanichi
Published: September 2005

Second harmonic generation (SHG) was observed from halide, in particular, chlorine-containing glasses. The magnitude of SHG increased with increasing ZnCl2 concentration and poling time. Although the mechanism of SHG is still controversial, the deficiency of cations near the anode surface was detected. However, in this glass system, the polishing of the anode side showed no effect on SHG. However, the polishing of the cathode side significantly decreased the magnitude of SHG. Therefore, the SHG mechanism in this glass system is made evident for the first time in which the movement of anions resulting in an anion-deficient layer near the cathode side is able to cause SHG.
Magnetic Behavior of Fe Doped In2O3
Authors: Kohiki Shigemi , Murakawa Yusuke , Hori Kyoko , Shimooka Hirokazu , Tajiri Takayuki , Deguchi Hiroyuki , Oku Masaoki , Arai Masao , Mitome Masanori , Bando Yoshio
Published: September 2005

We report spin-glass transition at room temperature (RT) and cluster-glass behavior below RT for Fe doped In2O3 powders with the atomic ratio of In : Fe = 1.85 : 0.15 grown in an oxygen atmosphere. In ac susceptibility, a large peak and a small cusp were observed at RT and ≈30 K, respectively. The peak at RT shifted to higher temperatures with an increase of applied field frequency, while the cusp showed no frequency dependence. Third harmonic nonlinear susceptibility exhibited a divergent peak at RT. Field-cooled dc susceptibility increased almost linearly below RT, whereas zero-field-cooled dc susceptibility deviated below the field-cooled one with lowering temperature.
High-Quality ZnO Thin Films Grown by Fast Pulsed Laser Deposition without a Buffer Layer
Authors: Lin Ming-Zheng , Su Chun-Tsung , Yan Hong-Chang , Chern Ming-Yau
Published: September 2005

For the first time, a fast pulsed laser deposition (FPLD) process is presented for the epitaxial growth of ZnO thin films on c-plane sapphire substrates. This process is driven by a 355 nm solid-state laser pulsing at 10 kHz. The ZnO thin films grown by FPLD show a width of ∼10 arcsec in the X-ray ω-scan and distinct Pendellösung fringes in the θ–2θ scan of the ZnO(0002) reflection. Photoluminescence spectra reveal sharp donor-bound excitons of ∼5 meV width and free excitons up to n = 2. Compared to conventional (much slower) PLD, 1–20 Hz, the measurements indicate that higher quality ZnO films can be grown by FPLD. In particular, despite the large lattice mismatch, such ZnO films were grown by FPLD directly on sapphire substrates without a buffer layer.
Attempt at Two-Dimensional Mapping of X-ray Fluorescence from Breast Cancer Tissue
Authors: Ando Masami , Yamasaki Katsuhito , Ohbayashi Chiho , Esumi Hiroyasu , Hyodo Kazuyuki , Sugiyama Hiroshi , Li Gang , Maksimenko Anton , Kawai Toshiaki
Published: September 2005

A world first two-dimensional mapping of X-ray fluorescence from an invasive papillary carcinoma containing three kinds of metal elements that by white radiation has been obtained. Carcinoma shows intense Ca K X-rays, while normal tissue including stroma, shows no such Ca X-ray signals within experimental precision, but even shows reasonable Fe and Zn K X-ray intensity. This has extremely good correspondence to an X-ray dark-field (X-DF) image taken using a Laue angular analyzer. This fact may suggest an idea that carcinoma may attract Ca atoms better than Fe and Zn atoms, which are involved more in normal tissue.
Impact of sarcoglycan complex on mechanical signal transduction in murine skeletal muscle
Authors: Barton Elisabeth R.
Published: September 2005

Loss of the dystrophin glycoprotein complex (DGC) or a subset of its components can lead to muscular dystrophy. However, the patterns of symptoms differ depending on which proteins are affected. Absence of dystrophin leads to loss of the entire DGC and is associated with susceptibility to contractile injury. In contrast, muscles lacking γ-sarcoglycan (γ-SG) display little mechanical fragility and still develop severe pathology. Animals lacking dystrophin or γ-SG were used to identify DGC components critical for sensing dynamic mechanical load. Extensor digitorum longus muscles from 7-wk-old normal (C57), dystrophin- null ( mdx), and γ-SG-null ( gsg−/−) mice were subjected to a series of eccentric contractions, after which ERK1/2 phosphorylation levels were determined. At rest, both dystrophic strains had significantly higher ERK1 phosphorylation, and gsg−/− muscle also had heightened ERK2 phosphorylation compared with wild-type controls. Eccentric contractions produced a significant and transient increase in ERK1/2 phosphorylation in normal muscle, whereas the mdx strain displayed no significant proportional change of ERK1/2 phosphorylation after eccentric contraction. Muscles from gsg−/− mice had no significant increase in ERK1 phosphorylation; however, ERK2 phosphorylation was more robust than in C57 controls. The reduction in mechanically induced ERK1 phosphorylation in gsg−/− muscle was not dependent on age or severity of phenotype, because muscle from both young and old (age 20 wk) animals exhibited a reduced response. Immunoprecipitation experiments revealed that γ-SG was phosphorylated in normal muscle after eccentric contractions, indicating that members of the DGC are modified in response to mechanical perturbation. This study provides evidence that the SGs are involved in the transduction of mechanical information in skeletal muscle, potentially unique from the entire DGC.