bluuebunny/crossref_metadata_2025 huggingface dataset:
Thermal Study of Nanometer-Spaced Head-Disk Systems
Authors: Li Hui , Liu Bo , Chong Tow-chong
Published: October 2005

The `cooling effect' of air flow is non-negligible in an ultralow-flying-height (FH) head-disk system. In this study, we develop a heat transfer model to study the heat flux and heat transfer in a head-disk interface. Moreover, a three-dimensional (3-D) finite element (FE) model is developed for steady-state analysis of a slider's thermal protrusion due to a DC write current. Results show that the heat flux is significantly different throughout a slider's air bearing surface (ABS). The high-speed air flow reduces approximately 80% of the temperature rise induced by the write current. This suggests that the actual heat flux distribution and a slider's ABS should be introduced in the thermal-structure FE analysis of a nanometer-spaced head-disk system.
Optical Gain in GaN Quantum Well Lasers with Quaternary AlInGaN Barriers
Authors: Park Seoung-Hwan , Kim Hwa-Min , Ahn Doyeol
Published: October 2005

Optical gain in GaN quantum-well (QW) lasers with quaternary AlInGaN barriers lattice-matched to GaN is investigated on the basis of the multiband effective-mass theory and is compared with that of conventional GaN/AlGaN QW structures. GaN/AlInGaN QW lasers are expected to have enhanced optical gain compared with GaN/AlInGaN QW lasers. However, the optical gain is shown to be reduced markedly with increasing band gap of the AlInGaN barrier. This is because the spontaneous polarization effect is increased significantly for the QW structures with a larger AlInGaN band gap. We find that the threshold current density of the GaN/AlInGaN QW structure can be reduced using a quarternary AlInGaN barrier.
Design and Operation of High-Energy and High-Average-Power Diode-Pumped Single Nd:YAG Amplifier with Stimulated-Brillouion-Scattering Phase Conjugate Mirror
Authors: Kiriyama Hiromitsu , Yamakawa Koichi , Kageyama Nobuto , Miyajima Hirofumi , Kan Hirofumi , Yoshida Hidetsugu , Nakatsuka Masahiro
Published: October 2005

We describe a compact laser-diode-pumped, phase conjugate Nd:YAG master oscillator power amplifier system with a reduced number of components in the single slab amplifier geometry. This system is readily suited for pumping a Ti:sapphire amplifier, making it possible to construct a compact, high-repetition-rate, terawatt-peak-power chirped-pulse amplification system. An average infrared power of 362 W at a repetition rate of 1 kHz in a 29 ns pulse has been produced with an optical-to-optical efficiency of 14%. With a KTiOPO4 frequency-doubling crystal, an average green output power of 132 W at a repetition rate of 1 kHz has also been generated when pumped at an input incident power of 222 W, corresponding to a second-harmonic energy conversion efficiency of 60%. The average power at both infrared and green wavelengths represents a record performance for a single-amplifier system. We discuss in detail the design, performance and operation of the system including output power, optical efficiency, beam quality and stability.
A Bidirectional 2 ×2 Optical Switch Technique Using Absorption or Amplification Function of Erbium-Doped Fiber
Authors: Yeh Chien-Hung , Lee Chien-Chung , Chi Sien
Published: October 2005

A novel bidirectional 2 ×2 optical switch technique, based on conventional erbium-doped fibers (EDFs) that operate at a pumped or unpumped power level, is proposed and demonstrated experimentally. By using the amplification and absorption functions of EDFs and a simple architecture design, the input signals can be switched to a suitable port. The response time of wavelength switching approaches about 2 ms. Moreover, the behavior and system performance of the proposed configuration are also studied.
Three-Terminal Dual-Emitter Phototransistor with Both Voltage- and Power-Tunable Optical Gains
Authors: Chen Hon-Rung , Chen Wei-Tien , Hsu Meng-Kai , Tan Shih-Wei , Lour Wen-Shiung
Published: October 2005

InGaP/GaAs dual-emitter heterojunction phototransistors (DEPTs) with an emitter biased using a voltage is reported for comparison to heterojunction phototransistors (HPTs) with a floating base operated in the p–i–n and transistor modes and to the HPTs with a base biased using a voltage. Although the power- and voltage-tunable optical gains are expected when the base of the HPT is floated and biased using a voltage, respectively, a conventional HPT's configuration does not simultaneously exhibit both. On the contrary, the optical gains of the DEPT can be tuned by both the voltage applied to the emitter and the incident optical power. Experimental results show that (1) the power-tunable optical gains are in the range of 11–29 as determined by the incident optical power upon the HPT with a floating base, (2) the small optical gains tuned by a voltage are 0.83–1.6 with a gain-tuning efficiency of 4.4 V-1 for the HPT with a base electrode, and (3) the DEPT with an emitter biased using a voltage exhibits an enhanced optical gain, with a gain-tuning efficiency of 43.4 V-1, when compared with the HPT with a floating base. Finally, a new concept of current-sharing effects in the base region is introduced to explain power- and/or voltage-tunable characteristics with good agreement found.
Effect of Post Annealing on Performance of Polymer Light-Emitting Devices
Authors: Tu Ming-Lung , Su Yan-Kuin , Lu Wei-Chung , Yang Henglong , Kuo Tzung-Fang , Wen Ten-Chin
Published: October 2005

A high luminescence and a high efficiency could be obtained for polymer light emitting diodes (PLEDs) after post annealing at an appropriate temperature. Calcium was used as the cathode material of light emitting diodes based on 2,3-dibutoxy-1,4-poly(phenylene vinylene) (DB-PPV). Ca diffused into polymer and degraded the performance after PLEDs were post annealed at various temperatures except for 120°C. The luminescence of PLEDs reached 5343 cd/m2 after annealing at 120°C. The corresponding efficiency under the condition was 3.04 cd/A. Both high luminescence and efficiency were greatly enhanced after PLEDs were annealed at 120°C.
Polarization-Selective Liquid-Crystal Device and Its Application to Recordable Integrated Optical Unit
Authors: Shih Hsi-Fu , Tsai Chih-Yuah
Published: October 2005

A polarization-selective multiple-beam liquid crystal grating (MBLCG) was designed. It can be applied to an integrated optical unit (IOU) for a recordable optical pickup head in small form factor with the functions of recording data using a single beam and retrieving data using multiple beams, respectively. This device is constructed using the technologies of liquid crystal light modulator for switching diffraction effects of a single transmissive beam and multiple diffracted beams. The proposed IOU composes of a laser diode, a photodetector, a MBLCG and a holographic optical element (HOE). The optical axes of the MBLCG and HOE are mutually perpendicular so that the round-trip light efficiency of the IOU can be maximized. Experimental results show that the MBLCG is capable of generating seven diffracted beams with equal light intensities and polarization-selective corresponding to an incident beam of the ordinary or extraordinary state.
Analysis of Rubbing-Angle-Dependent Reflective Fringe-Field Switching Mode
Authors: Park Jun Baek , Kim Hyang Yul , Jeong Youn Hak , Kim Seo Yun , Lim Young Jin
Published: October 2005

In the transflective fringe-field switching (FFS) mode with a wide-viewing characteristic, it is essential to match the voltage–reflectance curve with the voltage–transmittance curve. However, the operating voltage in the reflective part is smaller than that in the transmissive part. In addition, the strong fringe field at the edge of pixel electrodes [second indium–tin oxide (ITO)s] results in significant non-uniformity in liquid crystal (LC) director distribution. To increase the operating voltage of the reflective part toward that of the transmissive part, a structure with an increased rubbing angle and resin on pixel electrodes is postulated.
Photoluminescence Studies of In-Doped GaN:Mg Films
Authors: Chang Fu-Chin , Chou Wu-Chin , Chen Wen-Hsiung , Lee Ming-Chih , Chen Wei-Kuo , Huang Huai-Ying
Published: October 2005

Photoluminescence (PL) studies of In-doped GaN:Mg films revealed that the Mg-related emission at 3.1 eV is enhanced by more than one order of magnitude on the shoulder of the broad band centered at 2.8 eV for GaN:Mg after an optimal In concentration was added into the films. This enhancement of the 3.1 eV band is believed to be associated with the reduction in the number of self-compensation centers. A slow decay in PL intensity evolution was also observed, which may be ascribed to a local energy barrier that impedes carriers that relax into the valence band. The temperature dependences of the decay time constants were measured and a barrier energy as high as ∼103±7 meV was obtained for In-doped GaN:Mg as compared with 69±8 meV for GaN:Mg.
Thickness Dependence of Current Conduction and Carrier Distribution of GaAsN Grown on GaAs
Authors: Chen Jenn-Fang , Hsiao Ru-Shang , Hsieh Ming-Ta , Huang Wen-Di , Guo P. S. , Lee Wei-I , Lee Shih-Chang , Lee Chi-Ling
Published: October 2005

Thickness dependence of the properties of GaAsN grown on GaAs was investigated by characterizing GaAs/GaAs0.982N0.018/GaAs Schottky diodes by current–voltage (I–V), capacitance–voltage (C–V) profiling and deep-level transient spectroscopy (DLTS). I–V characteristics show a considerable increase in the saturation current when the GaAsN thickness is increased from 60 to 250 Å. As GaAsN thickness is increased further, the I–V characteristic deviates from that of a normal Schottky diode with a large series resistance. These I–V characteristics correlate well with carrier distribution. In thick GaAsN samples, C–V profiling shows carrier depletion in the top GaAs layer and frequency-dispersion accumulation in the GaAsN layer. DLTS spectra show that the carrier depletion in the top GaAs layer is due to an EL2 trap and the frequency-dispersion accumulation is due to the removal of electrons from a trap at 0.35 eV in the GaAsN layer. Increasing the GaAsN thickness markedly increases the magnitude of both traps. The large series resistance in thick GaAsN samples is due to EL2 that markedly depletes the top GaAs layer.
Polarization Reversals in the Presence of 90° Domain Walls
Authors: Ishibashi Yoshihiro , Iwata Makoto , Salje Ekhard
Published: October 2005

Polarization reversals in ferroelectrics in the presence of 90° domain walls are studied using a simplified model. The rotation of a single polarization under the field applied perpendicularly to the original orientation correlates to the anisotropy of local potential energy. The polarization reversals in a ferroelectric system consisting of the a- and the c-domains are studied on the basis of the Landau–Ginzburg free energy. A complex mechanism of polarization reversal was found to depend strongly on the spatial anisotropy of the Landau–Ginzburg energy.
Ab Initio Calculation of Work Functions of ZrO/W(100) and YO/W(100) Surfaces
Authors: Tanaka Hiroo , Nakayama Haruka , Watanabe Kazuyuki
Published: October 2005

The work functions of ZrO/W(100) and YO/W(100) surfaces are investigated by the ab initio calculation based on the density-functional theory. The work function of the W(100) surface is markedly decreased owing to the adlayers of ZrO and YO, which is in good agreement with experimental observations. The energetically stable configuration of ZrO and YO on the W(100) surface is found not to be perpendicular to the surface but to lie on the surface, which cannot be derived from the phenomenological surface-dipole model. We found from the detailed analysis of surface electronic structures that the lying configuration lowers the work function appreciably, particularly for ZrO, owing to an O atom going into the hollow site of the W(100) surface. The present study emphasizes the crucial role of ab initio calculation for clarifying the electronic-state-based origin of the work function.
Novel Transflective Display with Fringe-Field Switching Mode
Authors: Park Jun Baek , Kim Hyang Yul , Jeong Youn Hak , Kim Seo Yun , Lim Young Jin
Published: October 2005

A novel transflective fringe-field switching (FFS) mode has been studied. In a conventional transmissive FFS mode, the effective λ/2 retardation is relatively higher (=0.375) than that in a reflective FFS mode. In a novel design, the in-cell retarder only placed in a reflective part optimizes retardation and matching electrooptic characteristics in the reflective part with that in a transmissive part. In addition, a multislit angle concept is proposed for the optimization of electro optic characteristics.
Microscopic Description of the Dielectric Experiment of Some Liquid Crystals*
Authors: Otowski Wojciech , Demus Dietrich , Biernat Agnieszka
Published: October 2005

Dielectric properties measure the collective response of a charge-free system to an applied electric field, and are a probe of molecular polarizability, dipole moment and the internal field in the anisotropic media. Interactions between dipoles cannot be discounted in the molecular interpretation of the dielectric properties of liquid crystals. So, the theories for these properties are more complicated than for magnetic or optical properties. This paper presents comparison of the predictions of the Nordio–Rigatti–Segre theory with the results of the broadband dielectric studies of the dielectric relaxation processes of a few macroscopically oriented liquid crystals. Using the quantum chemical program MOPAC/7, with the AM1 Hamiltonian a few essential values have to be calculated in advance. Moreover a new procedure for the calculation of the order parameter has been proposed.
Molecular Dynamics Study of Fictive Temperature Dependence of Density of Vitreous Silica
Authors: Kuzuu Nobu , Nagai Ken , Tanaka Mitsuya , Tamai Yoshinori
Published: October 2005

The fictive temperature T
F dependence of the density ρ of vitreous silica has been studied using a molecular dynamics simulation. The density slightly decreases with increasing T
F at T
F<T
*. At a T
F>T
*, the ρ–T
F curve becomes convex, which is qualitatively the same as the experimental evidence. The density at any T
F is greater than that before quenching, at which point the sample had been equilibrated at T=T
F. At T
F>T
*, the difference in the density at T
F and the correspsonding temperature T=T
F is rather large compared to those at T
F<T
*. This is due to the creation of overcoordinated structures.
Preparation of β-FeSi2 Thin Films on Silica Glass Substrates by Vacuum Evaporation Using FeSi2 Powder as Evaporation Material
Authors: Kokubun Yoshihiro , Saito Kaname , Saito Koichi , Ehara Takashi , Nakagomi Shinji
Published: October 2005

β-FeSi2 films have been prepared on silica glass substrates by vacuum evaporation using FeSi2 powder as an evaporation material. Polycrystalline films were obtained by annealing the as-deposited films above 800°C. X-ray diffraction (XRD) showed that the films composed of only the β-FeSi2 phase were formed by the evaporation using the virgin FeSi2 source. On the other hand, the ε-FeSi phase in addition to the β-FeSi2 phase was contained in the films prepared by using the source residue in the former evaporation. XRD measurements also showed that the residue of the FeSi2 source contained much ε-FeSi phase. It was found that the virgin FeSi2 source is indispensable in preparing β-FeSi2 films reproducibly by vacuum evaporation using the FeSi2 source.
Stresses and Temperature Stability of Dense Wavelength Division Multiplexing Filters Prepared by Reactive Ion-Assisted E-Gun Evaporation
Authors: Wei Chao-Tsang , Shieh Han-Ping D.
Published: October 2005

In this paper, we report the in situ measurement of the temperature stability of narrow-band-pass filters on different types of substrate, for dense wavelength division multiplexing (DWDM) filters in optical-fiber transmission systems. The DWDM filters were designed as all-dielectric Fabry–Perot filters and fabricated by reactive ion-assisted deposition. Ta2O5 and SiO2 were used as high- and low-refractive-index layers, respectively, for constructing the DWDM filters. The accuracy and stability of the coating process were evaluated for fabricating the DWDM filters for the temperature stability of the center wavelength. The center wavelength shift was determined to be greatly dependent on the coefficient of thermal expansion of the substrate on which the filter is deposited.
Analysis of Local Breakdown Process in Stressed Gate SiO2 Films by Conductive Atomic Force Microscopy
Authors: Seko Akiyoshi , Watanabe Yukihiko , Kondo Hiroki , Sakai Akira , Zaima Shigeaki , Yasuda Yukio
Published: October 2005

We have studied the processes of local degradation through current leakage leading to breakdown in gate SiO2 films by conductive atomic force microscopy (C-AFM). Electrical stress was applied to the SiO2 films in the form of metal–oxide–semiconductor capacitors. Leakage current spots caused by holes trapped at stress-induced defects appeared in current images of the stressed SiO2 films. During the C-AFM observation at the same area with a high electric field, currents at these leakage spots gradually increased and the breakdown finally occurred at these sites, whereas at background regions other than the leakage spots, leakage currents gradually decreased. In contrast, in the case of nonstressed SiO2 films, the breakdown occurs without showing any predictive signs. Degradation and breakdown mechanisms depending on the stress condition are discussed.
Characterization of TiO2/Polyelectrolyte Thin Film Fabricated by a Layer-by-Layer Self-Assembly Method
Authors: Kim Jin-Ho , Shiratori Seimei
Published: October 2005

Multilayers thin films consisted of TiO2 nanoparticles and oppositely charged polyelectrolytes were fabricated by layer-by-layer self-assembly method and their properties were characterized. At pH 2.0, TiO2 nanoparticles were maximally deposited with poly(sodium 4-styrenesulfonate) (PSS) and the thickness and the surface roughness of film assembled with poly(acrylic acid) (PAA) were largest because of the loopy structure of PAA in acidic solution. On the other hand, the thin film prepared with poly(vinylsulfonic acid–sodium salt) (PVS) showed the high deposition of TiO2, lowest surface roughness, high refractive index (n=2.1) at 632 nm, and high transmittance in visible range. In addition, this film composed of anatase nanoparticles showed good photocatalytic property by decomposing methyl orange molecules with UV irradiation.
High Energy-Resolution Electron Energy-Loss Spectroscopy Study of Electronic Structures of Barium Titanate Nanocrystals
Authors: Suzuki Keigo , Terauchi Masami , Uemichi Yusuke , Kijima Kazunori
Published: October 2005

High energy-resolution electron energy-loss spectra were obtained from barium titanate (BaTiO3) nanocrystals (BTNCs), which were synthesized by chemical vapor deposition using inductively coupled plasma. Onset energies of spectral intensities were 3.2 eV for 34 nm BTNCs and 3.5 eV for 6 nm BTNCs. This indicates an increase in the bandgap energy of BaTiO3 with a decrease in crystal sizes. Those onset energies obtained from 90 nm specimen areas showed an excellent agreement with those estimated by previously reported optical measurements. Volume plasmon peaks were observed at 26.5 eV for 34 nm BTNCs and 25 eV for 6 nm BTNCs. Dielectric functions of the BTNCs were derived from loss-functions by Kramers–Kronig analysis using the refractivity of bulk BaTiO3 (=2.4). The peaks of O 2p→Ti 3d (t2g) transitions in the imaginary part of dielectric function (ε
2) were observed at 3.3 eV for 34 nm BTNCs and 3.8 eV for 6 nm BTNCs. Those of O 2p→Ti 3d (eg) transitions were at 7.8 eV for 34 nm BTNCs and 6.6 eV for 6 nm BTNCs.
Nested Cathode Structure in Field Emission Displays
Authors: Choi Yong Soo
Published: October 2005

The under-gate cathode structure using carbon nanotubes as the emitter has a great advantage in manufacturing because of its simple structure and fabrication. If the field emission display enters into the market of high-resolution flat panel displays, beam focusing could be one of the main problems to overcome. In this study, we investigate the characteristics of a nested cathode structure that is based on the under-gate cathode structure but differs in that the source of electron emission is surrounded on four sides by its own cathode electrode to which the lowest electric potential is applied. We examine beam focusing for the nested cathode through the calculation of beam trajectory by computer simulation and confirm the properties by fabricating a real panel.
Epitaxial Growth of (001)Rh Thin Film on (001)MgO Single-Crystal Substrate by Sputtering
Authors: Kato Kiyohiko , Abe Yoshio , Sasaki Katsutaka
Published: October 2005

We have expected that (001)Rh films with a thickness of 100 nm can be grown epitaxially on (001)MgO, because the lattice mismatch between the two-dimensional superlattice cells consisting of 11×11 unit cells of (001)Rh and 10×10 unit cells of (001)MgO is small. Thus, the effects of substrate temperature (T
s) on the crystal quality, surface morphology and resistivity of sputtered Rh films were studied. As a result, it is revealed that the (001)Rh films are grown epitaxially on (001)MgO at T
s=500°C with the relationship of Rh(001)[110]∥MgO(001)[110]. In addition, the average surface roughness of the epitaxially grown (001)Rh films is 0.28 nm, and a minimum resistivity of 4.9 µΩ cm is obtained.
The Response of the silicon-based Linear Energy Transfer Spectrometer (RRMD-III) to Protons from 1 to 70 MeV
Authors: Terasawa Kazuhiro , Borak Thomas B. , Doke Tadayoshi , Fuse Tetsuhito , Hara Ken-ichiro , Kikuchi Jun , Kitamura Hisashi , Suzuki Satoshi , Uchihori Yukio
Published: October 2005

Experiments have been performed to measure the response of the silicon-based linear energy transfer (LET) spectrometer (RRMD-III) to protons with energies ranging from 1 to 70 MeV. The beam energies incident upon RRMD-III were obtained using plastic polycarbonate degraders with mono-energetic proton beams that were extracted at 70, 40 and 25 MeV from a cyclotron. The energy loss in the degraders never exceeded 70% of the incident energy in order that the energy spread of the emerging protons created by straggling and scattering effects could be suppressed. Estimates of the LET were influenced by the asymmetric energy distribution of the degraded beam. Protons with energies less than 12.2 MeV did not reach the second Si detector in RRMD-III and were not measured. Measured values of LET were within ±7% of the expected value for incident protons that had an energy sufficient to penetrate the second Si detector in RRMD-III (E>15.4 MeV). The LET of stopping particles was computed using a lookup table listing LET vs E, and a simple stopping power formula for a particle with charge Z and energy E
R, where E
R is the energy of the stopping particle measured in the second Si detector.
Design and Characteristic Measurement of Miniature Three-Segment Linear Paul Trap
Authors: Furukawa Tadashi , Nishimura Jin , Tanaka Utako , Urabe Shinji
Published: October 2005

We have fabricated a miniature three-segment linear Paul trap with r
0=0.6 mm and 2Z
0=4 mm. In order to perform quantum-state manipulation of trapped 40 Ca+ ions, we discuss the required harmonic oscillation frequencies which allow us to perform effective sideband cooling and have measured those that depend on the dimensions of the trap. A laser beam that has a component in the radial direction of the linear trap as well as that propagating along the trap axis has been used to detect the fluorescence spectra of the 42
S
1/2–42
P
1/2 transition. We have observed that the profile of the fluorescence spectrum obtained with the side laser beam is markedly different from that obtained with the axial laser beam due to micromotion. By applying additional DC voltages, the micromotion has been compensated, its amplitude has been estimated, and crystallization has been observed for two 40 Ca+ and four 40 Ca+ ions.
Study of Pathway of Hydrogen Migration and Desorption on SiGe(100) Surface Using Ab Initio Calculations
Authors: Cheng Chia-Liang , Tsai Dah-Shyang , Jiang Jyh-Chiang
Published: October 2005

Ab initio calculations have been carried out to investigate the pathways of H-atom migration and H2 desorption on a mixed SiGe(100)-2×1 surface using the cluster model. The H2 recombinative desorption is the rate-determining step in hydrogen migration and desorption on SiGe(100) surfaces, since the energy barrier to H-atom migration is generally lower than that of H2 desorption. The energy barriers for H2 desorption from the interdimer, the Si–Ge pair, (52.8 kcal/mol), and the Ge–Ge pair, (45.1 kcal/mol), are lower than that for the Si–Si pair by 7.5 and 15.2 kcal/mol, respectively. Thus, the SiGe(100)-2×1 surface in chemical vapor deposition provides more dangling bonds than the Si(100)-2×1 surface because of Ge inclusion. In contrast, the chemisorbed H tends to stay on the Si-site, since the barrier for H-migration from the Ge-site to the Si-site is lower that in the opposite direction by 5.6 kcal/mol. Hence, a considerably higher percentage of Ge sites are dangling bonds, compared with Si sites on the SiGe(100) surface. Related transition state structures in the migration and desorption steps are also discussed.
Physical Properties of Cyanine–7,7,8,8,8-Tetracyanoquinodimethane Charge Transfer Complexes
Authors: Liao Wen-Yih , Lee Sanboh , Hu Andrew Teh , Lee Ming-Chia
Published: October 2005

A novel intramolecular charge transfer complex–cyanine–7,7,8,8,8-tetracyanoquinodimethane (TCNQ) dye was formed by grafting. The cyanine–TCNQ complex was characterized by UV–vis spectroscopy, fluorescence emission spectroscopy, and magnetic techniques. The optical properties of the cyanine–TCNQ dye, which forms an intramolecular charge transfer complex, are significantly different from cyanine–I with the same basic structure. A g factor of 2.0029 was determined. The magnetic susceptibility of intramolecular complexes with linkers containing three or five carbon atoms, E03–TCNQ and E05–TCNQ, increase rapidly as temperature decreases below 70 K. E03–TCNQ and E05–TCNQ are paramagnetic and plots of 1/(χM-χTIP) versus T show that the Curie–Weiss temperatures θ are 8×10-5 K and 0.398 K for E03–TCNQ and E05–TCNQ, respectively.
IR Study on Stacking Manner of Peptide Nanorings in Peptide Nanotubes
Authors: Nagai Yukiko , Nakanishi Tsutomu , Okamoto Hajime , Takeda Kyozaburo , Furukawa Yukio , Usui Kenji , Mihara Hisakazu
Published: October 2005

We here report our theoretical as well as experimental studies on the stacking manner of peptide nanorings (PNRs) in peptide nanotubes (PNTs). We focus on the molecular vibrations of N–H and C=O stretching modes and discuss this subject via their infrared (IR) spectroscopy, because PNTs are formed by the inter-ring H bonds between the adjacent PNRs via –N–H…O=C–. Symmetry analysis based on group theory reveals that parallel stacking causes two IR active modes in these molecular vibrations while three modes are active in the antiparallel stacking. This difference in the number of IR active modes is determined only by the stacking manner and not by the number of amino acid residues composing the PNRs. By using two typical PNRs of cyclo[–(L-Gln–D-Ala)3] and cyclo[–(L-Gln–D-Ala)4], we further studied the favorable stacking manners of PNRs via IR observation. Our IR experiments as well as the ab initio energetics show that the former PNRs create a PNT by stacking themselves in parallel while the latter PNRs do so by stacking themselves in an antiparallel manner.
Long-Axis Fabry–Pérot Cavity for Intense Laser-Compton Photon Beam
Authors: Toyokawa Hiroyuki , Yamada Kawakatsu , Ohgaki Hideaki , Hayashi Shusuke , Kii Toshiteru , Yamazaki Testuo , Goko Shinji
Published: October 2005

A long-axis Fabry–Pérot cavity was designed and installed on one of the straight sections of 800 MeV electron storage ring of National Institute of Advanced Industrial Science and Technology (AIST), to increase the yield of laser-Compton photons by about an order of magnitude compared with the currently obtained value. Resonance in the fundamental mode was achieved, and the cavity finesse was measured to be 660. The cavity gain was estimated to be 75.
Calculation of Spatial Impulse Response for Array Transducer
Authors: Sung Chia-Chi , Yang Hsin-I , Jeng Jiann-Hwa
Published: October 2005

Unlike the conventional method of obtaining the spatial impulse response (SIR) for a transducer from the time domain, we propose a new and computationally efficient approach for calculating the acoustic field for a rectangular focusing array transducer in a transmitting, receiving, or transmitting–receiving (pulse–echo) mode from the frequency domain. The SIR spectrum, corresponding to each single frequency, is derived by superposing the sound fields generated by the subdivided rectangular sources. The time-domain pressure variation is obtained by taking the inverse Fourier transform from the combination of each SIR spectrum for the array. The results for a single rectangular transducer in transmitting and receiving modes match well with those from previous studies. The SIR spectrum for a focusing linear array transducer with multiple field scatterers is also developed. The proposed approach markedly reduces the number of sampling points, thereby substantially increasing the computation efficiency.
Fabrication of Low-Voltage Electron Source from Patterned Arrays of Aligned Single-Walled Carbon Nanotube Ropes
Authors: Tong Yu , Liu Chang , Zhao Zhigang , Cheng Hui-Ming
Published: October 2005

With an enhanced field amplification factor (β) owing to their high length/diameter ratios, macroscopically long ropes of aligned single-walled carbon nanotubes (SWCNTs) showed a very low operation voltage in field emission measurements, along with an excellent emission stability under ultrahigh vacuum. SWCNT rope field emitters of similar lengths and diameters were fabricated into patterned arrays in a desired area at a designed distribution density to meet the requirements of a high emission current for an electron source. A tractable means to diminish the influence of the screening effect by introducing insulating partitions into SWCNT rope arrays was developed. The as-prepared low-voltage electron source typically realized current densities of 1–10 mA/cm2 at a voltage of no more than 1000 V.
Back-Gate Effect on Coulomb Blockade in Silicon-on-Insulator Trench Wires
Authors: Nishiguchi Katsuhiko , Crauste Olivier , Namatsu Hideo , Horiguchi Seiji , Ono Yukinori , Fujiwara Akira , Takahashi Yasuo , Inokawa Hiroshi
Published: October 2005

A back-gate (BG) effect on a Coulomb blockade in a double-gate silicon-on-insulator (SOI) nanowire is investigated. The nanowire, which is situated at the bottom of a trench and connected to thicker source/drain regions, has a naturally formed barrier at both ends and works as a single-electron transistor at low temperatures. We found that a negative BG voltage increases the charging energy of the Coulomb-blockade island in the nanowire as well as the tunnel resistance of the barriers. This indicates the possibility that the BG voltage shifts the electron wave functions in the source/drain area away from the Coulomb-blockade island and decreases the capacitance of the small junctions located at both ends of the island.
Synthesis of Size- and Structure-Controlled Ge2Sb2Te5 Nanoparticles
Authors: Choi Hoon Sang , Seol Kwang Soo , Takeuchi Kazuo , Fujita Junya , Ohki Yoshimichi
Published: October 2005

Pulsed laser ablation of Ge2Sb2Te5 target materials at approximately 400 Pa of ambient argon gas produces amorphous nanoparticles with a size distribution of from 4 to 30 nm. Thermal treatment of the nanoparticles in their aerosol states crystallizes the particles to both a hexagonal structure and a face-centered cubic structure at 300°C, while only a face-centered cubic structure results at 400°C. The crystallized nanoparticles were then size-classified by a differential mobility analyzer to produce size- and structure-controlled Ge2Sb2Te5 nanoparticles. The particles are revealed to consist of germanium, antimony and tellurium by composition analysis using energy dispersive X-ray spectroscopy.
Fabrication and Characterization of In0.25Ga0.75N/GaN Multiple Quantum Wells Embedded in Nanorods
Authors: Hsueh Tao-Hung , Sheu Jinn-Kong , Huang Hung-Wen , Chang Ya-Hsien , Ou-Yang Miao-Chia , Kuo Hao-Chung , Wang Shing-Chung
Published: October 2005

In0.25Ga0.75N/GaN multiple quantum wells embedded in nanorods with diameters of 60–100 nm were fabricated by inductively coupled plasma reactive ion etching with Cl2/Ar plasma. The strong optical emission of the nanorods, observed by micro-photoluminescence measurement at 80 K, reveals a large blue shift of about 90 meV and an increase in photoluminescence intensity density of more than 17-fold, compared with that of the as-grown wafer under the same excitation power density of 80 W/cm2. These nanostructures have a high potential for application in efficient GaN-based vertical cavity emitters.
Highly Ordered Anodic Porous Alumina by Imprinting Using Ni Molds Prepared from Ordered Array of Polystyrene Particles
Authors: Matsui Yoshitaka , Nishio Kazuyuki , Masuda Hideki
Published: October 2005

Anodic porous alumina with a highly ordered pore arrangement was prepared by imprinting using a metal (Ni) mold prepared from a two-dimensional ordered array of polystyrene particles as a template. The ordered array of shallow concaves of Al prepared by imprinting could initiate pore development and could guide pore growth during anodization. This process enables the high-throughput preparation of highly ordered anodic porous alumina because the metal mold can be used repeatedly.
Computational Study on Stable Structures, Formation Energies, and Conductance of Single Benzene-dithiolate between Two Au Electrodes
Authors: Tanibayashi Satoru , Tada Tomofumi , Watanabe Satoshi , Yoshizawa Kazunari
Published: October 2005

The stable atomic structures, formation energies, and conductance of single benzene-dithiolate between two facing gold electrodes are studied within the framework of density functional theory using a two-layered cluster model for the Au(111) surface of both electrodes. The computed conductance depends on both the adsorption site and the angle between the molecule and electrode surface. In the case where the molecule is perpendicular to the Au(111) surface, the expected value of conductance is strongly dominated by the configuration in which the molecule is adsorbed onto the electrodes at the fcc site because of large differences in formation energies between fcc and other configurations.
New III–V Semiconductor InGaAsBi Alloy Grown by Molecular Beam Epitaxy
Authors: Feng Gan , Yoshimoto Masahiro , Oe Kunishige , Chayahara Akiyoshi , Horino Yuji
Published: October 2005

A new Bi-containing III–V semiconductor InGaAsBi alloy was firstly grown by molecular beam epitaxy (MBE). The high crystalline quality of the InGaAsBi epilayer with smooth interfaces was confirmed by X-ray diffraction measurements. Up to 2.5% Bi was incorporated in the film based on Rutherford back scattering (RBS) results. The RBS channeling spectra give clear evidence that the Bi atoms were substitutionally located in the InGaAs zinc-blende lattice sites.
High-Power Operation of Diode Edge-Pumped, Glue-Bonded, Composite Yb:Y3Al5O12 Microchip Laser with Ceramic, Undoped YAG Pump Light-Guide
Authors: Tsunekane Masaki , Taira Takunori
Published: October 2005

The high-power operation of a diode edge-pumped, composite Yb3+-doped Y3Al5O12 (Yb:YAG) microchip laser has been demonstrated. The novel hybrid composite microchip has a 5-mm-diameter, 300-µm-thickness, single-crystal Yb:YAG core and a transparent ceramic, undoped YAG pump light-guide surrounding the core with the same thickness. The high-reflection coated face of the microchip was bonded to a water-cooled heat-sink by a thermally conductive glue for efficient conduction cooling. The pump light from a fourfold diode stack directly coupled to the light-guide and maximum output powers of 410 W (peak) and 285 W have been successfully obtained at an input pump power of 866 W in quasi-continuous-wave (10 ms, 10 Hz) and continuous-wave operations, respectively, at room temperature.
Self-Induced Instabilities in Nd:Y3Al5O12Ceramic Lasers
Authors: Narita Tatsuro , Miyasaka Yoshihiko , Otsuka Kenju
Published: October 2005

We systematically studied dynamic effects in Nd-doped Y3Al5O12(YAG) ceramic lasers having different Nd concentrations. A variety of dynamic instabilities, including square wave periodic pulsations, were found to take place due to the increased grain boundaries in highly-doped samples.
Giant Bragg Wavelength Tuning of Tunable Hollow Waveguide Bragg Reflector
Authors: Sakurai Yasuki , Matsutani Akihiro , Sakaguchi Takahiro , Koyama Fumio
Published: October 2005

We demonstrate a giant Bragg wavelength tuning with a grating loaded hollow waveguide Bragg reflector. An air-core thickness change of a hollow waveguide enables us to achieve a large propagation constant change over few tens percent, which would be useful for various tunable optical devices. Our observed Bragg-wavelength tuning range is over 160 nm at an air-core thickness change from 10.7 to 1.8 µm, which corresponds to a propagation constant change of over 10%. This is the record large tuning value ever reported in conventional tuning schemes such as thermo-optic or electro-optic effects.
Cell Culture on Nanopillar Sheet: Study of HeLa Cells on Nanopillar Sheet
Authors: Nomura Shinobu , Kojima Hiroko , Ohyabu Yoshimi , Kuwabara Kosuke , Miyauchi Akihiro , Uemura Toshimasa
Published: October 2005

This is the first report of the successful culturing of HeLa cells on nanopillar sheets–a new type of cell culture dish–in a different way from that on flat petri dishes. Nanopillar sheets were fabricated with a high-aspect ratio structure with a diameter of 80–1000 nm and a height of 1–3 µm using nanoprint technology. Nanopillar structure with 500 nm diameter and 1 µm height enabled easy subculture of the cells from the sheets without the conventional trypsinization method. Moreover, the HeLa cells divided and proliferated on the sheets in the same way as on the flat surfaces with different manner of adhesion.
Strong Excitonic Emission from (001)-Oriented Diamond P–N Junction
Authors: Makino Toshiharu , Kato Hiromitsu , Ogura Masahiko , Watanabe Hideyuki , Ri Sung-Gi , Yamasaki Satoshi , Okushi Hideyo
Published: October 2005

We have succeeded in fabricating (001)-oriented diamond p–n junctions with good diode characteristics and realized UV light emission by current-injection at room temperature. As p–n junctions, a phosphorus-doped n-type layer was formed on (001)-oriented boron-doped p-type one by applying an optimized homoepitaxial growth technique based on micro-wave plasma-enhanced chemical vapor deposition. Current–voltage characteristics showed a rectification ratio of 106 at ±30 V at room temperature. The existence of the space-charge layer through the p–n junction was confirmed from capacitance–voltage characteristics. A strong UV light emission at 235 nm was observed at forward current over 20 mA and is attributed to free exciton recombination.
High-Mobility Field-Effect Transistors Based on Single-Crystalline ZnO Channels
Authors: Nishii Junya , Ohtomo Akira , Ohtani Keita , Ohno Hideo , Kawasaki Masashi
Published: October 2005

We have fabricated field-effect transistors with single-crystalline ZnO channels consisting of high-quality epitaxial films grown on lattice-matched (0001) ScAlMgO4substrates by laser molecular-beam epitaxy. Amorphous alumina gate insulators are deposited on the top of the ZnO films using either RF magnetron sputtering or electron-beam evaporation. The field-effect mobility (µFE) of the device prepared by the latter method is as high as 40 cm2·V-1·s-1, one order of magnitude higher than those typically observed for polycrystalline channel devices. However, hysteresis appears in transfer characteristics. This unfavorable effect is found to be eliminated by the thermal annealing of the entire devices in air. The much larger hysteresis and lower µFEare observed for the device with sputtered gate insulators. This is presumably due to dense surface states created by ion or electron bombardment during the sputtering.
Effects of Annealing Process on Dielectric Properties of (Ba,Sr)TiO3 Thin Films Grown by RF Magnetron Sputtering
Authors: Ha Jong-Yoon , Choi Ji-Won , Kang Chong-Yun , Karmanenko S. F. , Yoon Seok-Jin , Choi Doo-Jin , Kim Hyun-Jai
Published: October 2005

Single phase thin films of (Ba0.5Sr0.5)TiO3 have been prepared by single target RF magnetron sputtering. Through post-annealing process in box furnace at 1100°C for 1 h, we have been able to improve the dielectric properties; dielectric permittivity, dielectric loss, and tunability. The change in dielectric properties before and after post-annealing is attributed to the change in film strain and the contraction in film lattice.
Precursor Evaluation for Cu-Supercritical Fluid Deposition Based on Adhesion Properties and Surface Morphology
Authors: Momose Takeshi , Sugiyama Masakazu , Shimogaki Yukihiro
Published: October 2005

Three Cu-precursors [Cu(hfac)2, Cu(DPM)2, and Cu(acac)2] for supercritical fluid deposition (SCFD) were evaluated based on their adhesion strength onto a TiN underlayer for ULSI metallization. Although the fluorinated precursor, Cu(hfac)2, has the highest solubility in supercritical CO2 among these three precursors, the deposited Cu film was hazy and had poor adhesion property due to the fluorine at the interface of Cu and its TiN underlayer. The two non-fluorinated precursors, Cu(DPM)2 and Cu(acac)2, dramatically improved the adhesion property of the deposited Cu film. Although Cu(acac)2 has the lowest solubility among these precursors, it had the lowest nucleation temperature and much smoother surface morphology, which are crucial for ULSI metallization.
Reflectance Diffuse Optical Tomography: Its Application to Human Brain Mapping
Authors: Ueda Yukio , Yamanaka Takeshi , Yamashita Daisuke , Suzuki Toshihiko , Ohmae Etsuko , Oda Motoki , Yamashita Yutaka
Published: October 2005

We report the successful application of reflectance diffuse optical tomography (DOT) using near-infrared light with the new reconstruction algorithm that we developed to the observation of regional hemodynamic changes in the brain under specific mental tasks. Our results reveal the heterogeneous distribution of oxyhemoglobin and deoxyhemoglobin in the brain, showing complementary images of oxyhemoglobin and deoxyhemoglobin changes in certain regions. We conclude that our reflectance DOT has practical potential for human brain mapping, as well as in the diagnostic imaging of brain diseases.
Giant Vesicle Fusion on Microelectrodes Fabricated by Femtosecond Laser Ablation Followed by Synchrotron Radiation Etching
Authors: Rahman Md. Mashiur , Nonogaki Youichi , Tero Ryugo , Kim Yong-Hoon , Uno Hidetaka , Zhang Zheng-Long , Yano Takayuki , Aoyama Masaki , Sasaki Ryuichiro , Nagai Hiroyuki , Yoshida Makoto , Urisu Tsuneo
Published: October 2005

We have developed a new technique for fabricating a hole (well) with a diameter of about 1 µm for a microelectrode on the surface of SiO2 (600 nm)/CoSi2 (10 nm)/Si substrate. This process enabled the fabrication of electrode holes while maintaining the original nanolevel flatness (R
a∼0.8 nm) of the SiO2 surface. A lipid bilayer was formed by giant vesicle fusion on these microelectrodes. Fluorescence microscope, in situ atomic force microscope and electrical characteristics measurements showed that a single lipid bilayer of sufficiently high resistance (gigaohm seal) was successfully fabricated.
Highly Manufacturable and Reliable 80-nm Gate Twin Silicon–Oxide–Nitride–Oxide–Silicon Memory Transistor
Authors: Park Byung-Gook , Choi Byung Yong , Choi Woo Young , Lee Yong Kyu , Lee Jong Duk , Shin Hyungcheol , Sung Suk-Kang , Kim Tae-Yong , Cho Eun Suk , Cho Byung Kyu , Bai Keun Hee , Kim Dong-Dae , Kim Dong-Won , Lee Choong-Ho , Park Donggun
Published: October 2005

Thanks to the combination of damascene gate and outer poly-Si sidewall spacer process, we have successfully fabricated twin silicon–oxide–nitride–oxide–silicon (SONOS) memory (TSM) transistors with 20-nm twin nitride storage nodes under an 80-nm gate. In terms of device manufacturability, the damascene gate process makes it possible to realize physically separated structure and the outer poly-Si sidewall spacer scheme contributes to realization of 20-nm long nitride storage node. Compared with conventional SONOS transistor, the fabricated TSM transistor maintains its threshold voltage margin between the forward and reverse reads down to 80-nm long gate. The TSM transistor also shows stable and reliable characteristics: up to 105 program/erase cycles endurance and fairly good bake retention at 150°C.
Record-High Trapped Magnetic Field by Pulse Field Magnetization Using GdBaCuO Bulk Superconductor
Authors: Fujishiro Hiroyuki , Kaneyama Masahiko , Tateiwa Tatsuya , Oka Tetsuo
Published: October 2005

A trapped magnetic field B
T
P as high as 4.47 T, which is the highest reported using pulse field magnetization to date, has been realized on the surface of a GdBaCuO bulk superconductor by a modified multi pulse technique combined with stepwise cooling. Following an introduction of a small amount magnetic flux into the bulk center by applying lower pulse fields B
ex=4.5–4.6 T twice at a higher starting temperature T
s=45–48 K, higher fields of B
ex=6.6–6.7 T are applied three times at a lower T
s=28–29 K. The reduction in the temperature rise due to the already existing trapped flux, in addition to the optimization of the higher B
ex value at the lower T
s, is a key point in enhancing B
T
P.
Mechanical Characteristics of Diamond-Like-Carbon Nanosprings Fabricated by Focused-Ion-Beam Chemical Vapor Deposition
Authors: Nakamatsu Ken-ichiro , Nagase Masao , Namatsu Hideo , Matsui Shinji
Published: October 2005

Our investigation of diamond-like-carbon (DLC) nanosprings with a 130-nm spring section diameter, which were fabricated by focused-ion-beam chemical vapor deposition (FIB-CVD), showed for the first time that nanosprings can be stretched. We observed large displacements of the FIB-CVD nanosprings with in-situ optical microscopy; in other words, the nanosprings showed behavior similar to that of macroscale springs. In addition, we investigated the dependence of the spring constant of the DLC nanosprings on the spring diameter. The spring constants, measured using commercially available cantilevers, ranged from 0.47 to 0.07 N/m. The diameter dependence of the measured spring constant was accurately expressed by the conventional formula for a coil spring. The estimated shear modulus of the DLC nano-springs was about 70 GPa. This value is very close to the value of conventional coil springs made of steel.
Evaluation of Spin-Transfer Switching in CoFeB/MgO/CoFeB Magnetic Tunnel Junctions
Authors: Kubota Hitoshi , Fukushima Akio , Ootani Yuichi , Yuasa Shinji , Ando Koji , Maehara Hiroki , Tsunekawa Koji , Djayaprawira David D. , Watanabe Naoki , Suzuki Yoshishige
Published: October 2005

Current-induced magnetization switching was demonstrated on Co–Fe–B/MgO/Co–Fe–B magnetic tunnel junctions (MTJs), which exhibited giant tunnel magnetoresistance ratios of about 100%. Switching current density at a pulse duration of 100 ms was about 6×106 A/cm2 at room temperature. The switching current density was reduced to one-third of the smallest value for the MgO-based MTJs reported to date. Dependence of the switching current on pulse duration and on the external magnetic field was discussed based on a theoretical model incorporating thermally activated spin-transfer switching. The spin-transfer switching in the MgO-based MTJs realizes low writing power consumption and a high read-out signal in high-density magnetoresistive random access memory.