bluuebunny/crossref_metadata_2025 huggingface dataset:
Tissue Elasticity Reconstruction Based on Modified 3-Dimensional Finite-Element Model
Authors: Yamakawa Makoto , Shiina Tsuyoshi
Published: July 2005

Tissue elasticity is specific to each tissue. Quantitative tissue elasticity measurement technology enables new tissue diagnoses. In this paper, we propose a new tissue-elasticity reconstruction method that estimates Young's modulus distribution using quantitative tissue-elasticity information, at a high speed and with a high precision. In addition, noninvasive tissue diagnosis will be possible because we use ultrasonic waves for this measurement. Unlike methods that assume the 1-dimensional or 2-dimensional state, and unlike the method based on a perfect 3-D model that we proposed earlier, our new method uses a modified 3-D finite-element model. Using our modified 3-D model, we can estimate Young's modulus solely from the 2-D strain distribution, to an accuracy almost comparable to that of the method using 3-D strain distribution, and at a much higher speed. In this paper, we verify the validity of the method based on a modified 3-D finite-element model, using simulations and phantom experiments.
Bubble Manipulation by Self Organization of Bubbles inside Ultrasonic Wave
Authors: Yamakoshi Yoshiki , Koganezawa Masato
Published: July 2005

Microbubble manipulation using ultrasonic waves is a promising technology in the fields of future medicine and biotechnology. For example, it is considered that bubble trapping using ultrasonic waves may play an important role in drug or gene delivery systems in order to trap the drugs or genes in the diseased tissue. Usually, when bubbles are designed so that they carry payloads, such as drug or gene, they tend to be harder than free bubbles. These hard bubbles receive a small acoustic radiation force, which is not sufficient for bubble manipulation. In this paper, a novel method of microbubble manipulation using ultrasonic waves is proposed. This method uses seed bubbles in order to manipulate target bubbles. When the seed bubbles are introduced into the ultrasonic wave field, they start to oscillate to produce a bubble aggregation of a certain size. Then the target bubbles are introduced, the target bubbles attach around the seed bubbles producing a bubble mass with bilayers (inner layer: seed bubbles, outer layer: target bubbles). The target bubbles are manipulated as a bilayered bubble mass. Basic experiments are carried out using polyvinyl chloride (PVC) shell bubbles. No target bubbles are trapped when only the target bubbles are introduced. However, they are trapped if the seed bubbles are introduced in advance.
Numerical Analysis of Temperature Rise in Tissue Using Ultrasound
Authors: Saito Yoshikazu , Ishizeki Takahiro , Tsuchiya Takenobu , Endoh Nobuyuki
Published: July 2005

In order to avoid burns from ultrasonic radiation, it is important to accurately predict the temperature rise caused by the absorption of ultrasonic radiation in tissue. We describe a preliminary study on the simulation of the temperature rise distribution when the thermal diffusivity is changed. The sound pressure distribution is calculated by the finite difference time domain (FDTD) method, and the thermal conduction distribution in tissue is calculated by the heat conduction equation (HCE) method. Because the boundary condition affects the calculation results, the measured experimental temperature is used for calculations.
Room-Temperature Single-Hole Transistors Made Using Semiconductor Carbon Nanotube with Artificial Defects near Carrier Depletion Region
Authors: Kamimura Takafumi , Maeda Masatoshi , Sakamoto Kazue , Matsumoto Kazuhiko
Published: July 2005

We have succeeded in observing the single hole transistor characteristics in position-controlled grown carbon nanotubes (CNTs) with artificial defects formed by a chemical process. Coulomb blockade characteristics were observed around the hole depletion region even at room temperature. At a low temperature, however, the Coulomb blockade characteristics were observed both in hole and electron transport regions.
Ultrasonic Rotary Motors Using Complex Transverse and Torsional Vibration Rods and Multiple Longitudinal Vibration Transducers
Authors: Suzuki Atsuyuki , Kihara Masaki , Katsumata Yasuhiro , Ishii Keisuke , Tsujino Jiromaru
Published: July 2005

The vibration and load characteristics of ultrasonic motors having (a) a torsional vibration cylinder with three bolt-clamped Langevin piezoelectric ceramic (PZT) longitudinal vibration transducers (BLTs) installed in the tangential direction and (b) a longitudinal vibration disk with three BLT transducers installed around a circular disk were studied. The center rod vibrates longitudinally and affects the load characteristics of the ultrasonic motor. Vibration distributions along a center rod were measured using a laser Doppler vibrometer. Revolution, electric input power, mechanical output power and efficiency were measured under various rotating torques. Maximum torque, revolution and efficiency of the ultrasonic motor with (a) a torsional vibration cylinder (a) were 0.75 Nm, 205 rpm and 1.68%, respectively, and (b) 0.32 Nm, 84 rpm and 1.68%, respectively, with a circular longitudinal vibration disk.
Visualization of Acoustically Induced Cavitation Bubbles and Microjets with the Aid of a High-Speed Camera
Authors: Kubo Takashi , Kuwabara Mamoru , Yang Jian
Published: July 2005

Under ultrasonic irradiation at a frequency of approximately 42 kHz, model experiments in water have been performed to visualize the dynamic behavior of acoustic cavitation bubbles with a high-speed digital camera. The clustered cavitation multibubble moves linearly in random directions. The behavior of the clustered cavitation multibubble is discussed in relation to the behavior of a microjet as well as the phase transition of water between a normal liquid state and a supercritical fluid state. Another experiment has also been carried out to visualize microjets that appeared near a water/tetralin interface and a water/air interface. The behavior of clustered cavitation multibubble is accompanied by the microjets, and the microjets impinge strongly impinging on those interfaces. On the basis of these experimental results, one can conclude that the behavior of microjets and acoustic cavitation bubbles and their related phenomena are quite important for the understanding and control of the intensified macro- and micromixing of liquids.
Basic Research on Time-Reversal Waves in Deep Ocean for Long Acoustic Communication
Authors: Shimura Takuya , Watanabe Yoshitaka , Ochi Hiroshi
Published: July 2005

We have studied the focusing property of time-reversal waves and its application to acoustic communication in shallow water. In this study, this focusing property in the deep ocean and its application to long horizontal acoustic communication are discussed. The results are as follows. Even if a time-reversal array (TRA) does not expand from the sea surface to the seabed, time-reversal signals converge, and the focusing property is not significantly affected by the depths of the focus and TRA. Then, it is revealed that by using time reversal, it is possible to enssure communication channel over a long range, through the simulation. In phase modulation, time reversal can demodulate almost only by itself, while in amplitude and phase modulation, an adaptive filter to compensates further.
Solution Processed Conjugated Polymer Multilayer Structures for Light Emitting Devices
Authors: Piok Thomas , Plank Harald , Mauthner Gernot , Gamerith Stefan , Gadermaier Christoph , Wenzl Franz P. , Patil Satesch , Montenegro Revelino , Bouguettaya Mohamed , Reynolds John R. , Scherf Ullrich , Landfester Katharina , List Emil J. W.
Published: July 2005

We study the feasibility of semiconducting polymer nanospheres deposited from miniemulsions as an approach to form organic multilayer structures and devices from an all solution based process. A detailed study of the wetting and film forming properties of the dispersed semiconducting polymer nanospheres on different polar and non-polar organic surfaces is given. The transmission and fluorescence properties of the polymer multilayer structures are studied. Organic light emitting devices based on such multilayer structures are presented and their properties are discussed.
Low-Temperature Fabrication of Ultrathin ZrO2/Si Structure Using Metal Deposition Followed by Oxygen Annealing
Authors: Nagasato Yoshitaka , Aya Tsutomu , Iwazaki Yoshitaka , Hasumi Masahiko , Ueno Tomo , Kuroiwa Koichi
Published: July 2005

Metal deposition followed by oxygen annealing has been carried out for the fabrication of ZrO2/Si structures. Using this method, 200°C oxygen annealing enables the oxidation of Zr metal and 220°C annealing enables the surface potential control of Si in metal–insulator–semiconductor (MIS) structures, even if the dielectric constant of ZrO2 has been shown to be 11.8. High-quality ZrO2 films with a dielectric constant of ∼20 can be achieved by 300°C annealing with an interfacial layer of 0.9 nm thickness. For these films, no degradation of leakage characteristics was observed after the thermal budget corresponding to that of impurity activation at 850°C for 30 min. Consequently, using this method, a high-quality ZrO2/Si structure that has good chemical stability under a high thermal budget could be fabricated at a low temperature.
High-Mobility Hole-Transporting Polymers for Electroluminescence Applications
Authors: Lee Tik Ho , Tong Ka Lap , So Shu Kong , Leung Louis Man-Lay
Published: July 2005

A series of electroluminescent and conductive phenyl ring-substituted poly(N-phenyl-N-styryl-1-naphthylamine) (P-XNPA, where X=-H (P01), -OCH3 (P02) and -F (P03)) polymers were prepared. The polymers exhibit a high hole mobility, an excellent solubility and a good thermal stability. Their emission color, ionization potential (IP), quantum efficiency, glass transition temperature (T
g), efficiency and stability were all found to be related to the properties of the phenyl substituted side group. As an example, the hole mobility of poly(4-MeONPA) (P02) is 10-5 cm2V-1s-1 at room temperature, compared tothat of poly(N-vinylcarbazole) (PVK) being 10-7 cm2V-1s-1. P02 emits blue light at 450 nm and has a high thermal stability at an onset decomposition temperature above 420°C and T
g of 132°C. A simple organic light-emitting diode (OLED) device fabricated from the same polymer has a maximum luminance of 588 cd/m2 at 175 mA/cm2.
Self Assembled Monolayer for Molecular Electronics
Authors: Koo Ja-Ryong , Pyo Sang-Woo , Kim Jun-Ho , Lee Hyun-Koo , Kim Young Kwan
Published: July 2005

Molecular electronic devices were fabricated with thiol derivatives as redox-active component. This molecules have a thiol radical to allow monolayer formation by the self assembly method, and then this self assembled monolayer (SAM) were inserted between patterned Pt bottom electrode (30 nm) and Ti (5 nm)/Al (30 nm) top electrodes in crossbar array architectures. Before self assembly process, the substrate was treated by a piranha solution or a UV-ozone treatment. From contact angle measurements, before forming SAM, both the substrates treated by the piranha solution and the UV-ozone were hydrophilic condition. After forming SAM, the substrates were maintained with hydrophobic condition in case of the octadecanethiol (C18SH) and hydrophilic condition in case of the 11-mercapto-1-undecanol (HSC11OH). Such results were shown that the SAM was well packed. Also, the current-voltage (I–V) characteristics of the SAM devices along the direction vertical to substrate were measured.
Alignment of Nematic Liquid Crystal Molecules Using Nanometer-Sized Ultrafine Patterns By Electron Beam Exposure Method
Authors: Kagajyo Taichi , Fujibayashi Katsutoshi , Shimamura Toru , Okada Hiroyuki , Onnagawa Hiroyoshi
Published: July 2005

We have investigated the alignment of nematic liquid crystal (NLC) molecules using nanometer-sized ultrafine groove, tilted, and dot patterns fabricated by the electron beam exposure method. In order to improve the wetting condition of NLCs, we sputtered silicon dioxide on a substrate after the fabrication of ultrafine patterns. For a homogeneous alignment cell with an ultrafine groove pattern, an azimuthal anchoring energy of 2.84×10-4 J/m2 was obtained. We also confirmed tilted and homeotropic alignments using tilted and dot patterns, respectively.
Improved Light Outcoupling in Organic Electroluminescent Devices with Random Dots
Authors: Kitamura Akitoshi , Naka Shigeki , Okada Hiroyuki , Onnagawa Hiroyoshi
Published: July 2005

We fabricated organic electroluminescent devices with improved light outcoupling at the air/glass interface using mesa-shaped random dots. An improvement in the external quantum efficiency of 12.5% compared with that of a conventional device was achieved. In the device with random dots, emission without interference, which is a problem for the device with periodical dots, was obtained.
Reduction of Series Resistance in Organic Photovoltaic Cells Using a Metal-Doped Layer
Authors: Nakayama Ken-ichi , Matsui Yoshitaka , Yokoyama Masaaki
Published: July 2005

The series resistance of p-i-n type organic photovoltaic devices was reduced by indium doping in the naphthalene tetracarboxylic dianhydride (NTCDA) layer, which leads us to a marked increase of conductivity based on a peculiar electronic interaction. Partial doping near the electrode interface brought about an increase of aspects of the photovoltaic performance, in particular, the short circuit current and fill factor. On the other hand, doping to the whole NTCDA film quenched the photogenerated excitons and degraded the performance. On the basis of measurements of the action spectra, the increase of photovoltaic performance was attributed to an increase in the collection efficiency of photogenerated carriers due to a reduction of the series resistance.
Organometallic Chemical Vapor Deposition Growth of Heterostructure of Wide Band Gap and Transparent Boron Phosphide on Silicon
Authors: Odawara Michiya , Udagawa Takashi , Shimaoka Goro
Published: July 2005

A boron phosphide (BP) layer was grown on the (111) Si substrate by atmospheric pressure organometallic chemical vapor deposition (MOCVD) using triethylboran ((C2H5)3B) and phosphine (PH3) sources. By transmission electron diffraction analysis, the transparent BP layer was found to grow on (111) Si with the following orientation: (111),<110>-Si//(111),<110>-BP. The MOCVD-grown BP layers exhibited transparency under fluorescent light illumination. Reflected light color was observed to vary depending on the thickness of the BP layer. The refractive index (n) of the heteroepitaxial (111) BP layer was revealed to decrease from 3.16 at a wavelength (λ) of 350 nm to 2.77 at λ of 750 nm. The extinction coefficient (k) corresponding to n at λ of 350 nm was 0.19. Refractive index (n) and k at λ of 350 nm gave 9.95 as the real part of the complex dielectric constant of the MOCVD-grown BP layer. The optical evaluation indicated that BP is applicable as a transparent III-V semiconductor layer for forming heteroepitaxial structures with Si.
Effects of Electron Irradiation on CuInS2 Crystals
Authors: Abe Kenichiro , Miyoshi Yoshihiro , Ashida Atsushi , Wakita Kazuki , Ohshima Takeshi , Morishita Norio , Kamiya Tomihiro , Watase Seiji , Izaki Masanobu
Published: July 2005

The effect of electron irradiation on CuInS2 single-crystals grown using traveling heater method has been examined using photoluminescence (PL). It has been found that the emission intensities for exciton and donor-acceptor pair transitions decrease, and that the appearance of the structures in deep PL band increases. The peaks which appeared after the electron irradiation appear to be due to the recombination emission, involving deep donors and deep acceptors.
Quantification of Gas-Phase H-Atom Number Density by Tungsten Phosphate Glass
Authors: Morimoto Takashi , Umemoto Hironobu , Yoneyama Koji , Masuda Atsushi , Matsumura Hideki , Ishibashi Keiji , Tawarayama Hiromasa , Kawazoe Hiroshi
Published: July 2005

It is shown that H-atom densities in the gas phase can be evaluated by simply measuring the change in optical transmittance of tungsten phosphate glass plates. Tungsten oxide (WO3) doped in phosphate glass plates can be reduced by exposure to H atoms and the degree of reduction can be evaluated from the change in their optical transmittance. The difference in the logarithms of the transmittances before and after the reduction showed a linear dependence on the H-atom density evaluated by a vacuum-ultraviolet laser absorption technique. No change in the transmittance was observed in the absence of H atoms, showing that reduction of WO3 by H2 molecules can be ignored.
NO2 Gas Sensor Made of Porous MoO3 Sputtered Films
Authors: Yamazaki Toshinari , Jin Chengji , Nakayama Atsushi , Ito Koji , Yoshizawa Toshio , Kikuta Toshio , Nakatani Noriyuki , Yamabuchi Tatsuo
Published: July 2005

Molybdenum trioxide films were sputter-deposited on quartz substrates at various substrate temperatures and discharge gas pressures. The films were annealed in air at 450°C. Scanning electron microscopy showed that fine flakes were formed in the films deposited at 300°C, while the surface of the films deposited at room temperature was smooth. After annealing, the fine flakes in the former films grew, while in the latter films, a layered structure was formed. X-ray diffraction patterns showed that every film was composed of orthorhombic MoO3 crystallites. The highest sensitivity and the fastest response to NO2 gas were observed in a film with a layered structure, which was deposited at room temperature and a high pressure of 11 Pa. This film was found to be porous and to have a density of 2.8 g/cm3, which is much lower than the bulk density of 4.7 g/cm3.
Modeling of Reaction Pathways of GaN Growth by Metalorganic Vapor-Phase Epitaxy Using TMGa/NH3/H2 System: A Computational Fluid Dynamics Simulation Study
Authors: Hirako Akira , Kusakabe Kazuhide , Ohkawa Kazuhiro
Published: July 2005

A model of reaction pathways of GaN growth by metalorganic vapor-phase epitaxy was studied by computational fluid dynamics simulations. We included the formation of polymers such as [Ga–N]
n
and [MMGaNH]
n
(n=2–6) in the reaction model in a TMGa/NH3/H2 system for the first time. The simulations using this reaction modeling successfully explained experimental growth rates at various temperatures, and clarified the main reaction pathway of GaN growth. The change in gas-phase chemistry due to temperature in the range of 300–1400 K was investigated. It was found that the type of reactive molecule changes with temperature, followed by the formation of different polymers in a certain temperature range, that is, [MMGaNH]
n
at 600–750 K and [Ga–N]
n
at higher temperatures.
Photoluminescence Enhancement of ZnS:Mn2+ Nanocrystal Phosphors: Comparison of Organic and Inorganic Surface Modifications
Authors: Takahashi Hayato , Isobe Tetsuhiko
Published: July 2005

ZnS:Mn2+ nanocrystals of 3 nm in diameter were coated with silica to form 20±4 nm core/shell particles, as observed by transmission electron spectroscopy. For ZnS:Mn2+ nanocrystals modified with silica, the intensity of photoluminescence (PL) due to the d-d transition of Mn2+ increases with increasing tetraethyl orthosilicate (TEOS) amount and hence with increasing the thickness of silica shell. This is attributed to the passivation of surface defects and the quantum confinement effect. On the contrary, the PL intensity of the ZnS:Mn2+ nanocrystals modified by both lauryl phosphate (HLP) and silica decreases with increasing TEOS amount. 31P CP/MAS NMR spectroscopy reveals that the chemical interaction between phosphate groups and ZnS:Mn2+ is interrupted by the silica shell. These results suggest that the surface modification of HLP around the ZnS:Mn2+ nanocrystals is more effective than the formation of the silica shell from the viewpoint of PL enhancement.
Influence of Cu-Ion Migration and Fine-Line Effect on Time-Dependent Dielectric Breakdown Lifetime of Cu Interconnects
Authors: Noguchi Junji , Kubo Maki , Tsuneda Ruriko , Takeda Ken-ichi , Miura Noriko , Makabe Kazuya
Published: July 2005

The time-dependent dielectric breakdown (TDDB) of sub-half-micron Cu interconnects was investigated with respect to the waiting time between Cu chemical mechanical polishing (CMP) and barrier dielectric deposition. Breakdown voltage and TDDB lifetime between adjacent Cu wires decrease markedly if the waiting time in air exceeds 5 days. This is due to Cu-ion migration phenomenon on the CMP surface. The degradation can be improved by keeping the samples in a N2 box or adopting post-CMP cleaning. This TDDB degradation has been observed for various Cu barrier dielectrics in this study. In addition, a “fine-line effect” on Cu TDDB lifetime has been discovered. As Cu wire width becomes smaller, the TDDB lifetime also decreases because of the intensification of the electric field at the CMP surface.
Synthesis and Electric Property of CeAlO3 Ceramics
Authors: Wang Xusheng , Yamada Hiroshi , Nishikubo Keiko , Xu Chao-Nan
Published: July 2005

Cerium monoaluminate (CeAlO3) ceramics were synthesized at 1350–1500°C in a reducing atmosphere with H3BO3 as flux and characterized of their structural and electric properties. Pellets of such ceramics, sintered at 1400°C or above, showed a perovskite-like tetragonal structure with a density higher than 92% of its theoretical. These ceramic pellets were found to have a large dielectric constant higher than 600 and a small loss tangent lower than 0.04 in the frequency range of 10 kHz to 10 MHz. This sample also showed an electric conductivity of 4.71×10-9 S/cm and an optical bandgap width of 3.29 eV at room temperature.
Improvement of Ferroelectric Properties in Mo-Substituted Bi3.35La0.75Ti3O12 Films by Optimization of Heating Rate
Authors: Ohki Hiroshi , Wang Xusheng , Ishiwara Hiroshi
Published: July 2005

Bi3.35La0.75(Ti1-X
Mo
X
)3O12 (BLTM) (X=0.005) films were formed on Pt/Ti bottom electrodes by using a sol–gel spin-coating method in which the crystallization temperature, time, and ambience were fixed at 700°C, 30 min, and O2, respectively, but the heating rate was varied in the range from 1°C/s to 300°C/s. It was found through X-ray diffraction and transmission electron microscopy analyses that the heating rate dependences of the orientations and surface morphologies in the BLTM films were completely different from those in Bi3.35La0.75Ti3O12 (BLT) films. Under the optimum heating rate of 10°C/s, the remanent polarization value (2Pr) of 36 µC/cm2 and the leakage current density of 1.2×10-7 A/cm2 at 150 kV/cm were obtained for the BLTM film.
Piezoelectric Measurements of Granite as Composite Material Using Atomic Force Microscope
Authors: Matsuda Tomonori , Yamanaka Chihiro , Ikeya Motoji
Published: July 2005

The piezoelectric vibrational amplitude of a granite sample was measured using an atomic force microscope (AFM) and a lock-in amplifier system. Other samples such as lead zirconate titanate (PZT) and quartz were used as piezoelectric standards, and soda glass was examined as a control to check the background noise level. The converse piezoelectric effect, in which the electric field induces the strain, gave an apparent piezoelectric coefficient of ∼7.0 (± 0.1)×10-13 C/N for granite. The relative dielectric constant of granite was also obtained by measuring the vibrational amplitude and the phase difference at different frequencies. The value was in the order of 1013 less than 1 Hz and decreased as a function of frequency.
Growth of CuInS2 Epitaxial Films on Si(001) by Multisource Evaporation Method
Authors: Kobayashi Satoshi , Kozakai Hirohumi , Vequizo Reynaldo Magdadaro , Tsuboi Nozomu , Oishi Koichiro , Kaneko Futao
Published: July 2005

CuInS2 thin films were epitaxially grown on Si(001) wafers at 500°C using multisource evaporation method. The Cu source temperature was varied keeping the In and S source temperatures constant. The obtained films belonged to the Cu2S–In2S3 system with little extra phase over the range of 0.9≤[Cu]/[In]≤2.9. X-ray diffraction and reflection high energy electron diffraction measurements showed that the films were composed of Cu–Au, sphalerite and chalcopyrite structures, although the last was not always observed. The characteristic structures in the photoluminescence spectrum of a film with [Cu]/[In]=1.4 measured at 23 K was interpreted as the weak broad exciton emission and the donor-acceptor pair emission with a phonon replica comparing to the bulk crystals. The position and the broadening of the exciton emission are reasonable considering the coexistence of various crystal structures.
Construction of Independently Driven Double-Tip Scanning Tunneling Microscope
Authors: Takami Kazuhiro , Akai-Kasaya Megumi , Saito Akira , Aono Masakazu , Kuwahara Yuji
Published: July 2005

We construct an independently driven double-tip scanning tunneling microscope (STM) for evaluating electrical conduction within the micrometer scale under an ambient condition. Each independently driven STM unit has on atomic resolution and the tip approaches an intended position within 10 mm2 on the surface with three course driving stages and a piezoelectric device which has a maximum scan area of 10 µm. The current flow between the two tips through the material can be detected in the range from 0.1 pA to 100 nA. The measurement of the resistivity of regiorandom poly(3-octylthiophene) thin films was demonstrated using this system.
High-Critical-Current-Density Epitaxial Films of SmBa2Cu3O7-x in High Fields
Authors: Yoshida Yutaka , Matsumoto Kaname , Ichino Yusuke , Itoh Masakazu , Ichinose Ataru , Horii Shigeru , Mukaida Masashi , Takai Yoshiaki
Published: July 2005

The critical current density (J
c) and irreversibility field (B
irr) of epitaxial SmBa2Cu3O7-x
(SmBCO) films are reported. The B
irr and J
c of these films deposited on MgO(100) substrates by pulsed-laser deposition depend critically on the substrate temperature. The use of a thin SmBCO seed layer grown at a high substrate temperature enabled us to obtain fully c-axis-oriented SmBCO films at relatively low temperatures, resulting in a high J
c of 1.7 ×105 A/cm2 of B ∥c at 5 T and 77 K. This value is as high as that of the optimized NbTi superconducting wires achieved at 5 T and 4.2 K.
Low-Damage Sputtering of GaAs and GaP Using Size-Selected Ar Cluster Ion Beams
Authors: Nagano Masahiro , Yamada Susumu , Akita Shirabe , Houzumi Shingo , Toyoda Noriaki , Yamada Isao
Published: July 2005

We have investigated the irradiation damage depths produced by an Ar gas cluster ion beam (GCIB) and an Ar monomer ion beam (MIB) on GaAs and GaP, in a comparison of the cathode luminescence (CL) spectra of ion-irradiated and nonirradiated areas. The depths of irradiation damage in both substrates were estimated from the relationship between the CL intensity and the electron beam acceleration voltage.
Etching a Micro-Trench with a Maximum Aspect Ratio of 60 on Silica Glass by Laser-Induced Backside Wet Etching (LIBWE)
Authors: Kawaguchi Yoshizo , Sato Tadatake , Narazaki Aiko , Kurosaki Ryozo , Niino Hiroyuki
Published: July 2005

We have successfully fabricated a deep micro-trench about 7 µm wide and 420 µm deep on silica glass with a maximum aspect ratio of 60 bylaser induced backside wet etching(LIBWE) via KrF laser ablation of a saturated pyrene/acetone solution. The processing time for the microetching was as short as 5 min at a repetition rate of 80 Hz and a fluence ofF= 1.0 J·cm-2·pulse-1. The etch rate was calculated to be approximately 17 nm·pulse-1. The LIBWE method is shown to be very useful for surface microstructuring of silica glass with high aspect ratio and high throughput.
Effect of GaN Microlens Array on Efficiency of GaN-Based Blue-Light-Emitting Diodes
Authors: Kim Dongwoo , Lee Hyoyoung , Cho Namgil , Sung Younjoon , Yeom Geunyoung
Published: July 2005

In this study, GaN-based vertical light-emitting diodes (VLEDs) were fabricated by a laser lift-off (LLO) process and the effects of microlens formation by plasma etching on the optical properties of the LLO GaN-based VLED devices were investigated. By forming a 5–10 µm microlens array on the LLO GaN-based VLEDs, the measured light emission intensities at 460 nm and in the direction normal to the surface of the device increased by approximately 40% and 100% compared with those of the LLO GaN-based VLED without the microlens array for 10 µm and 5 µm microlens arrays, respectively.
Chirality of Magnetoelectropolymerized Polyaniline Electrodes
Authors: Mogi Iwao , Watanabe Kazuo
Published: July 2005

Polyaniline film electrodes were prepared by a magnetoelectropolymerization (MEP; electropolymerization under magnetic fields) method, and their chiral electrode properties were examined for L- and D-ascorbic acids by cyclic voltammetry. The MEP film electrodes showed different oxidation currents between enantiomers, and those prepared under reverse magnetic fields showed opposite chirality. These results indicate that the MEP method introduces chirality to the polyaniline films and such film electrodes possess the ability of enantioselective recognition for ascorbic acid.
Intrinsic Transit Delay and Effective Electron Velocity of AlGaN/GaN High Electron Mobility Transistors
Authors: Suemitsu Tetsuya , Shiojima Kenji , Makimura Takashi , Shigekawa Naoteru
Published: July 2005

A delay time analysis was carried out for AlGaN/GaN high electron mobility transistors (HEMTs) with gate lengths of 120–210 nm. The influence of the large parasitics in the access region is counted out by de-embedding these parasitics from the measured parameters. From the obtained intrinsic transit delay, the effective electron velocity is estimated to be 1.86 ×107 cm/s. The parasitic delay is rather a major cause of delay in the devices tested. We also found that the channel charging time is not negligible even at the gate length of 120 nm, whereas it can be in the InP HEMTs with the same gate length.
Synthesis and Characterization of Conductive Polypyrrole/Montmorillonite Nanocomposite
Authors: Enomoto Hiroyuki , Matsumoto Shigeo , Lerner Michael M.
Published: July 2005

A conductive polypyrrole/montmorillonite (PPY/MMT) nanocomposite was synthesized by the in situ polymerization of polypyrrole in the gallery of montmorillonite layers. HCl was adopted as a dopant of the conductive PPY polymer. The PPY/MMT film was prepared by a spin-coating method from the colloidal solution of the PPY/MMT nanocomposite. Nanocomposites have been characterized by powder X-ray diffraction (XRD) and electrical dc resistivity measurements. XRD patterns showed that all samples of PPY/MMT layered nanocomposites contain an organic polymer between all individual MMT sheets. Although the electrical resistivity of the PPY polymer was highly dependent on the pH of the solution, the electrical resistivity of the PPY/MMT nanocomposite was almost independent of the pH of the solution.
Fabrication of Microparticle Layer by Annealing Microparticle/Polymer Composite
Authors: Muramatsu Makoto , Ohdaira Toshiyuki , Suzuki Ryoichi
Published: July 2005

A simple and extensively applicable technique of fabricating microparticle layers was developed. Pure microparticle layers can be formed by annealing microparticle/polymer composite sheets on targets. During the annealing process, the polymer is pyrolytically decomposed and evaporated from the composite sheets. As a result, a layer consisting entirely of microparticles is formed on the target. Using this technique, silicon carbide whiskers and diamond microparticle layers were successfully fabricated on Si wafers.
Deep Sub-Micron Strained Si0.85Ge0.15 Channel p-channel Metal-Oxide-Semiconductor Field-Effect Transistors (pMOSFETs) with Ultra-Thin N2O-Annealed SiN Gate Dielectric
Authors: Chen Ching-Wei , Chien Chao-Hsin , Chen Yi-Cheng , Hsu Shih-Lu , Chang Chun-Yen
Published: July 2005

We have investigated the electrical characteristics of strained Si0.85Ge0.15 channel p-channel metal-oxide-semiconductor field-effect transistors (pMOSFETs) with ultra-thin N2O-annealed SiN gate dielectric. We have found that the thickness of SiGe channel has a great impact on the device characteristics. With controlling the SiGe layer thickness thinner than 15 nm, the device depict a subthreshold swing of 68 mV/A, the interface state density of 1×1011 eV-1·cm-2, acceptable junction leakage, and more than 50% hole mobility improvement with respect to the Si channel device. Therefore, high quality interface between the gate dielectric and the strained SiGe channel can be achieved by using the N2O-annealed SiN gate dielectric.
Structural and Electrical Properties of Polycrystalline Bi4-xNdxTi3O12 Ferroelectric Thin Films with in-Plane c-Axis Orientations
Authors: Matsuda Hirofumi , Kurachi Masahiro , Uchida Hiroshi , Watanabe Takayuki , Iijima Takashi , Koda Seiichiro , Funakubo Hiroshi
Published: July 2005

Bi4-x
Nd
x
Ti3O12 (BNT, x=0.25, 0.5, 0.75) thin films with in-plane c-axis orientations were grown on IrO2/Si from solution route and their electrical properties were studied. The remanent polarization exhibited a broad peak against x with the maximum value of 2P
r=47 µC/cm2 at x=0.5. The orthorhombic lattice parameters and Curie temperature T
C were measured for BNT powders prepared from the same coating solutions. Both orthorhombic anisotropy a/b and T
C monotonically decreased with increasing x. Irrespective of x, leakage current density J<1.5×10-7 A/cm2 under 100 kV/cm was observed by optimizing film growth temperature T
G=700°C, even though the Bi2O2 blocking layers aligned perpendicular to the film.
Micropatterning Oligonucleotides on Single-Crystal Diamond Surface by Photolithography
Authors: Zhang Guo-Jun , Umezawa Hitoshi , Hata Hideo , Zako Tamotsu , Funatsu Takashi , Ohdomari Iwao , Kawarada Hiroshi
Published: July 2005

DNA micropatterns have been for the first time fabricated on a single-crystal diamond surface in conjunction with the photolithography technique. A new chemical modification process for producing amine groups inside patterned regions and a passivation layer terminated with fluorine outside patterned regions is demonstrated. The resulting amine groups within patterned areas and fluorine termination outside patterned areas on the single-crystal diamond surface were characterized by spatially resolved X-ray photoelectron spectroscopy. Amine-terminated oligonucleotides were then linked to the amine-patterned regions using a crosslinker. It was revealed that hybridization on DNA-patterned diamond is specific and selective, with a low background outside the patterns and strong binding to complementary probe DNA immobilized inside the patterns but no binding to noncomplementary probe DNA similarly immobilized inside the patterns. These results suggest that DNA micropatterning on a single-crystal diamond may serve as an ideal platform for future biochips and biosensors.
Lubricant State Evaluation of Ultraviolet-Irradiated Magnetic Disk Using Lateral Friction Force Modulation Microscopy with Electric Current Distribution
Authors: Miyake Shojiro , Ninomiya Shigeyuki , Wang Mei
Published: July 2005

We describe an experimental study of lubricant state evaluation, conducted using an electrically conductive diamond tip equipped in a lateral friction force modulation microscope, on perfluoropolyether-coated magnetic diamondlike carbon disks with and without ultraviolet irradiation. It is shown that the current distribution on a surface is a crucial parameter governing surface damage and the lubricant state, and that a variation in current can be used to determine the surface morphology and wear properties. The lubricant distribution of lubricant dip coated onto the disks is evaluated at a low load and the wear properties are investigated at a high load.
Ni Thin Film Deposition from Tetrakistrifluorophosphine-Nickel
Authors: Ohshita Yoshio , Ishikawa Masato , Kada Takeshi , Machida Hideaki , Ogura Atsushi
Published: July 2005

The inorganic molecule Ni(PF3)4 is a candidate as a Ni chemical vapor deposition (CVD) precursor, which is an alternative to organometal sources. We develop a new method of synthesizing Ni(PF3)4 from Cp2Ni and PF3 with a high yield. Ni(PF3)4 is liquid at room temperature and has a vapor pressure (215 Torr at 30°C) sufficiently high for CVD. CVD using MeCp2Ni or CpAllyNi as a Ni precursor does not produce a Ni film on a Si surface, but CVD using the Ni(PF3)4/He gas system deposits a continuous Ni film on a Si surface at low temperatures below 200°C.
Protein Adsorption on Patterned Hydroxyapatite Thin Films Fabricated by Pulsed Laser Deposition
Authors: Kusunoki Masanobu , Kawasima Masami , Nishikawa Hiroaki , Morimoto Koichi , Hayami Takashi , Hontsu Shigeki , Kawai Tomoji
Published: July 2005

Protein adsorption on hydroxyapatite (HAP) thin film was investigated before and after patterning. Hydroxyapatite thin film 100 nm thick was deposited by pulsed laser deposition. The film was patterned by photolithography and wet etching with HCl solution. Proteins (phospholyrase b, bovine serum albumin, and others) labeled with fluorescein isothiocyanate (FITC) were used as the reagent. After the HAP film was soaked in the reagent and washed with pure water, a conspicuous contrast in FITC was observed between the HAP pattern and the glass substrate (or photoresist). This behavior showed that the biocompatibility of the HAP thin film was not influenced by the patterning process. Our technique for HAP thin film is adaptable for applications involving biosensors as electronic devices and scaffolds for tissue culture.
Modeling of Second-Harmonic Generation from Intracavity Surface-Emitting Lasers with Nonlinear Crystal
Authors: Kim Kyusang , Koyama Fumio , Terao Tsutomu , Kadoya Minoru , Izawa Takao
Published: July 2005

We present the optimum design of intracavity surface-emitting lasers with a nonlinear crystal for highly efficient second-harmonic generation. To realize a single-mode operation with high output power necessary for efficient frequency conversion, we introduce an external concave mirror structure in our laser design. The modeling result shows that the optimum inside mirror reflectivity of an intracavity structure is 70% on a 100-µm thick n-type GaAs substrate. We expect blue emission of more than 10 mW with a reduced substrate absorption and an optimized inside mirror reflectivity.
Giant and Stable Conductivity Switching Behaviors in ZrO2 Films Deposited by Pulsed Laser Depositions
Authors: Kim Soohong , Byun Iksu , Hwang Inrok , Kim Jinsoo , Choi Jinsik , Park Bae Ho , Seo Sunae , Lee Myoung-Jae , Seo David H. , Suh Dong-Seok , Joung Yong-Soo , Yoo In-Kyeong
Published: July 2005

ZrO2 films have been deposited on Pt/Ti/SiO2/Si substrates by pulsed laser deposition methods. Giant and stable conductivity switching behaviors with maximum on/off ratio of 106 and switching endurance of 105 times are observed in a typical Pt/ZrO2/Pt structure. The Pt/ZrO2/Pt structure exhibits two ohmic behaviors in the low-voltage region (V < 1.4 V) depending on the value of previously applied voltage and Schottky-type conduction in the high-voltage region (1.4 V< V <8.9 V). It seems that the conductivity switching behaviors result from the changes in both the Schottky barrier and the bulk conductivity controlled by applied voltages.
Center-Wavelength-Shifted Passively Mode-Locked Diode-Pumped Ytterbium(Yb):Yttrium Aluminum Garnet(YAG) Laser
Authors: Uemura Sadao , Torizuka Kenji
Published: July 2005

We generate 136-fs pulses from a passively mode-locked diode-pumped ytterbium(Yb):yttrium aluminum garnet(YAG) laser. This is to our knowledge the shortest pulse from a Yb:YAG laser. We shift the laser center wavelength from the commonly used 1030 nm to around 1050 nm to utilize the Yb:YAG spectrum broader.
Epitaxial Lateral Overgrowth of High Al Composition AlGaN Alloys on Deep Grooved SiC Substrates
Authors: Heikman Sten , Keller Stacia , Newman Scott , Wu Yuan , Moe Craig , Moran Brendan , Schmidt Mathew , Mishra Umesh K. , Speck James S. , DenBaars Steven P.
Published: July 2005

Fully coalesced Al0.93Ga0.07N films were demonstrated by metalorganic chemical vapor deposition on deep grooved SiC substrates. Lateral Al0.93Ga0.07N growth was achieved at low V/III ratios during growth. The deep grooves enabled coalescence despite of parasitic growth in the trenches. Dislocation reduction in the overgrown regions of the films was observed by transition electron microscopy and atomic force microscopy.
Enhanced Pixel-Driving Circuits for Active-Matrix Organic-Light-Emitting Diode Displays with Large Sizes
Authors: Yu Sang Ho , Choi Sung Wook , Shin Hong Jae , Kwack Kae Dal , Kim Tae Whan
Published: July 2005

Enhanced pixel-driving circuits for active-matrix organic-light-emitting diode (AM-OLED) displays with large sizes and highly uniform brightnesses were designed for system on panel. The driving method used the pre-charge functions of the data for a highly uniform brightness during a short time to program the current. The currents of the designed pixel-driving circuits were not significantly affected by variations in the threshold voltages, or by the mobilities of the driving thin-film transistors. These results indicate that the proposed pixel-driving circuits hold promise for potential applications in AM-OLED displays with large sizes and highly uniform brightnesses.
Determination Factor of Lattice Structure in Hexadecafluorovanadylphthalocyanine Epitaxially Grown on Alkali-Halide Substrates
Authors: Uno So-ichiro , Hoshi Hajime , Takezoe Hideo , Ishikawa Ken
Published: July 2005

The epitaxial growth of fluorine-substituted vanadylphtalocyanine (F
x
VOPc; x = 15.4) on KBr, KI, and RbI was studied. The lattice structure of F15.4VOPc changes from (√10 ×√10)R ±27° to (√8 ×√8)R0° as the lattice constants of the substrates increase. This sequence is different from that of other shuttlecock-shaped phthalocyanines(Pcs) such as VOPc, TiOPc and AlPcCl, in which the structure changes from (√10 ×√10)R ±27° to (3 ×3)R45°. The difference suggests that the orientation of molecules on the substrates plays an important role in the determination of the lattice structure of F15.4VOPc on alkali-halide substrates.
Synthesis of AlN Grains and Liquid-Phase-Epitaxy (LPE) Growth of AlN Films Using Sn-Ca Mixed Flux
Authors: Isobe Hiroaki , Kawamura Fumio , Kawahara Minoru , Yoshimura Masashi , Mori Yusuke , Sasaki Takatomo
Published: July 2005

AlN grains were synthesized using a Sn-Ca alloy flux. Conditions under which AlN grains could be synthesized were investigated by varying the flux composition (Ca:Sn) and the ratio of Al to flux. The Sn-Ca mixed flux enabled us to synthesize AlN grains under the relatively mild conditions of 900°C and 5 atm. We also attempted homoepitaxial liquid-phase epitaxy (LPE) growth on an AlN(0001) thin film grown on a sapphire(0001) substrate by metalorganic chemical vapor deposition (MOCVD) and obtained 1.8-µm-thick-AlN film in the liquid phase.
Diffusion Mechanism in Ag/TCNQ Thin Films with Cu as Tracers
Authors: Liu Ping , Jiang Yiming , Xie Hengbo , Guo Feng , Li Jin
Published: July 2005

Metalorganic thin film Ag-7,7,8,8-tetracyanoquinodimethane (TCNQ) is prepared by successive vacuum evaporation of Ag and TCNQ. The diffusion behavior in Ag-TCNQ is studied using Cu as a tracer, in combination with profile analyses by secondary ion mass spectroscopy (SIMS). The results show that the diffusion mechanism in Ag-TCNQ thin film is Ag ion diffusion accompanied by ion exchange.
Fabrication of Single Crystalline Diamond Triode Electron Emitter
Authors: Vinod Purayath Robert , Yamada Takatoshi , Hwang Doo-Sup , Fujimori Naoji
Published: July 2005

A novel and simple technique is proposed for the fabrication of gated single crystalline diamond Spindt-type emitter array with a small and precise gate aperture. An interesting silicon oxide deposition pattern `sphere on cone' enabled controlled gate opening by wet chemical etching. Using this technique a highly uniform Spindt-type emitter array with a specified gate aperture of 1.4 µm has been fabricated. Study on controlled field emission indicates the normal operation of the fabricated emitter.
Organic Light-Emitting Diodes Based on a Binuclear Platinum(II) Complex
Authors: Saito Kaori , Hamada Yuji , Takahashi Hisakazu , Koshiyama Tamami , Kato Masako
Published: July 2005

Electroluminescent properties of an emissive binuclear platinum(II) complex have been studied. We fabricated organic light-emitting diodes based on Pt2(ppy)2(pyt)2 (ppy = 2-phenylpyridine, pyt = pyridine-2-thiolate) phosphor, which exhibits an emission from a 3MMLCT state based on a Pt-Pt interaction. An electrophosphorescent device with a multilayer configuration of ITO/CuPc/NPB/Pt2(ppy)2(pyt)2/BAlq/Alq3/LiF/Al demonstrated red emission with Commission Internationale de L'Eclairage (CIE) coordinates of x=0.65, y=0.35, a maximum luminous efficiency of 1.8 cd/A (1.0 mA/cm2), and an external quantum efficiency of 3.4%.
Temperature Dependence of Surface Acoustic Wave Characteristics of GaN Layers on Sapphire Substrates
Authors: Nishimura Kazumi , Shigekawa Naoteru , Yokoyama Haruki , Hohkawa Kohji
Published: July 2005

We measured surface acoustic wave (SAW) characteristics along the [01-10] and [2-1-10] directions of 1.5- and 2-µm-thick GaN layers on (0001) sapphire substrates at ambient temperatures between -50 and 200°C. The extracted thermal coefficient of delay (TCD) for the SAW propagating along the [01-10] direction, which is smaller than that for the SAW propagating along the [2-1-10] direction, decreases when GaN layer thickness, h, multiplied by SAW wave number, k, increases. The TCD for h
k = 3.9, which might be close to that in bulk GaN, is as small as 28.3 ppm/deg. These results indicate that GaN is promising for SAW device operation over a wide range of ambient temperatures.
High-Performance Air-Stable Ambipolar Organic Thin-Film Transistor Based on F16CuPc and CuPc
Authors: Ye Rongbin , Baba Mamoru , Mori Kunio
Published: July 2005

We report on the fabrication of organic thin-film transistors based on fluorinated copper phthalocyanine (F16CuPc) and copper phthalocyanine (CuPc) layers. The thin-film transistors showed high-performance air-stable ambipolar characteristics with a field-effect hole mobility of 3.26 ×10-3 cm2/V·s and a field-effect electron mobility of 3.34 ×10-3 cm2/V·s, which are comparable to the unipolar field-effect mobilities of single-layer thin-film transistors. These outstanding ambipolar characteristics, along with the highly stable chemical nature of F16CuPc and CuPc, make this transistor an attractive candidate for organic complementary metal oxide semiconductor (CMOS) circuits.
Effect of Coriolis Force on Fingering Instability and Liquid Usage Reduction
Authors: Cho Hao-Chiang , Chou Fu-Chu , Wang Ming-Wen , Tsai Chu-Shu
Published: July 2005

The Coriolis force affects significantly the onset of fingering instability, the angle and shape of finger, and the maximum attainable radius. Once the effect of Coriolis force becomes appreciable, the fingers protrude out of the liquid front in a deflected angle with the radial line. The critical radius is only a function of the rotational Reynolds number when the Coriolis force is dominant. The finger's base area develops into a triangular-like shape. The deflected angle at the finger's base area is quite different from that of fingertip. The changing of finger's deflected angle results in the merging together of fingers, which in turn leads to the increase of maximum attainable radius.
Low-Dark-Current Large-Area Narrow-Band Photodetector Using InGaN/GaN Layers on Sapphire
Authors: Ohsawa Jun , Kozawa Takahiro , Hayashi Hiroyuki , Fujishima Osamu , Itoh Hiroshi
Published: July 2005

A metal–semiconductor–metal structure was fabricated on a 20-nm-thick InGaN layer, and showed a responsivity of over 0.1 A/W to the wavelength of 400 nm at a bias of 1 V. The photocurrent was almost linear to the power of the incident light in three decades. The Schottky interdigital electrodes kept the dark current to less than 100 pA at 10 V despite its large detecting area of 1 mm2. The device showed fast responses on the order of 10 ns to optical impulses from a 407 nm laser diode. Biasing at 1 V or lower is effective in suppressing the sensitivity in the wavelength range shorter than 350 nm when illuminated from the substrate side through a 2-µm-thick GaN layer, resulting in a narrow-band detector for the 400 nm band.