bluuebunny/crossref_metadata_2025 huggingface dataset:
CLUSTERING EFFECT OF USER-OBJECT BIPARTITE NETWORK ON PERSONALIZED RECOMMENDATION
Authors: GUO QIANG , LIU JIAN-GUO
Published: July 2010

In this paper, the statistical property of the bipartite network, namely clustering coefficient C4 is taken into account and be embedded into the collaborative filtering (CF) algorithm to improve the algorithmic accuracy and diversity. In the improved CF algorithm, the user similarity is defined by the mass diffusion process, and we argue that the object clustering C4 of the bipartite network should be considered to improve the user similarity measurement. The statistical result shows that the clustering coefficient of the MovieLens data approximately has Poisson distribution. By considering the clustering effects of object nodes, the numerical simulation on a benchmark data set shows that the accuracy of the improved algorithm, measured by the average ranking score and precision, could be improved 15.3 and 13.0%, respectively, in the optimal case. In addition, numerical results show that the improved algorithm can provide more diverse recommendation results, for example, when the recommendation list contains 20 objects, the diversity, measured by the hamming distance, is improved by 28.7%. Since all of the real recommendation data are evolving with time, this work may shed some light on the adaptive recommendation algorithm according to the statistical properties of the user-object bipartite network.
SYSTEMC IMPLEMENTATION AND PERFORMANCE EVALUATION OF A DECOUPLED GENERAL-PURPOSE MATRIX PROCESSOR
Authors: SOLIMAN MOSTAFA I. , Al-JUNAID ABDULMAJID F.
Published: July 2010

Technological advances in IC manufacturing provide us with the capability to integrate more and more functionality into a single chip. Today's modern processors have nearly one billion transistors on a single chip. With the increasing complexity of today's system, the designs have to be modeled at a high-level of abstraction before partitioning into hardware and software components for final implementation. This paper explains in detail the implementation and performance evaluation of a matrix processor called Mat-Core with SystemC (system level modeling language). Mat-Core is a research processor aiming at exploiting the increasingly number of transistors per IC to improve the performance of a wide range of applications. It extends a general-purpose scalar processor with a matrix unit. To hide memory latency, the extended matrix unit is decoupled into two components: address generation and data computation, which communicate through data queues. Like vector architectures, the data computation unit is organized in parallel lanes. However, on parallel lanes, Mat-Core can execute matrix-scalar, matrix-vector, and matrix-matrix instructions in addition to vector-scalar and vector-vector instructions. For controlling the execution of vector/matrix instructions on the matrix core, this paper extends the well known scoreboard technique. Furthermore, the performance of Mat-Core is evaluated on vector and matrix kernels. Our results show that the performance of four lanes Mat-Core with matrix registers of size 4 × 4 or 16 elements each, queues size of 10, start up time of 6 clock cycles, and memory latency of 10 clock cycles is about 0.94, 1.3, 2.3, 1.6, 2.3, and 5.5 FLOPs per clock cycle; achieved on scalar-vector multiplication, SAXPY, Givens, rank-1 update, vector-matrix multiplication, and matrix-matrix multiplication, respectively.
SORTING AND ROUTING ON OTIS-MESH OF TREES
Authors: LUCAS KENY T. , JANA PRASANTA K.
Published: July 2010

OTIS (optical transpose interconnection system) is a popular model of optoelectronic parallel computers that has gained enormous attention in the recent years. Several parallel algorithms have been published for many fundamental problems on this architecture. In this paper, first we propose a parallel algorithm for sparse enumeration sort on OTIS-Mesh of Trees (OTIS-MOT). For N (= n2) data elements, our sorting algorithm requires 4 log N electronic moves + 3 OTIS moves. We next present a shortest path routing algorithm that runs also in logarithmic time.
Effects of Energetic Ion Bombardment on Structural and Electrical Properties of Al-Doped ZnO Films Deposited by RF-Superimposed DC Magnetron Sputtering
Authors: Ito Norihiro , Oka Nobuto , Sato Yasusi , Shigesato Yuzo
Published: July 2010

The bombardment of various types of energetic ions during rf-superimposed dc magnetron sputter deposition was investigated in detail and their effects on the structural and electrical properties of Al-doped ZnO (AZO) films were analyzed. Aside from the expected energetic negative oxygen ions (i.e., O- and O2
-), various other negative ions (i.e., AlO-, AlO2
-, AlO3
-, ZnO-, and ZnO2
-) with a high energy were clearly observed. Such negative ions were found to be generated on the target surface and accelerated towards the substrate by the full cathode voltage. Furthermore, we found that the energy of these negative ions decreased with decreasing plasma impedance by superimposing rf power on dc sputtering. The resistivity of the AZO films deposited using the rf-superimposed dc sputtering was much lower than that of the films deposited using conventional dc sputtering. Such a decrease in resistivity should be attributed to reducing the damage of AZO films by suppressing the bombardment energies of various types of energetic negative ions impinging on a growing film surface.
Effect of Heat Treatment on 1.47 eV Band in CdTe Films on GaAs(100) Substrates
Authors: Onodera Chikara , Yoshida Masaaki , Taguchi Tsunemasa
Published: July 2010

We performed the heat treatment of CdTe films on GaAs substrates. The effect of heat treatment on a 1.47 eV band was characterized by photoluminescence (PL) spectra. As excitation density decreases, the emission peak shift of the 1.42 eV band is estimated to be 8.5 meV. As the excitation density decreases, the decrease in the intensity of the 1.47 eV band becomes faster than that of the 1.42 eV band. The 1.47 eV band decreases in intensity with heat treatment, while the 1.42 eV band increases in intensity. These results suggest that the origin of the 1.47 eV band is annealed by heat treatment. By comparing the changes of PL spectra with and without the 1.47 eV band of CdTe films before and after heat treatment, the increase in the intensity of the 1.42 eV band is considered to be related to the annealing of the origin of the 1.47 eV band.
Deep-Level Transient Spectroscopy and Photoluminescence Studies of Formation and Depth Profiles of Copper Centers in Silicon Crystals Diffused with Dilute Copper
Authors: Nakamura Minoru , Murakami Susumu
Published: July 2010

We have observed the formation of the Cu centers in p-type Si crystals diffused with dilute Cu between 400 and 1000 °C by deep-level transient spectroscopy (DLTS) and photoluminescence methods. For the samples diffused below 800 °C, a DLTS Cu center denoted as the CuDLB center was the main component and was almost uniformly distributed in the bulk. For the samples diffused above 800 °C, a precipitate-related Cu species was the main component at the surface, and low-concentration CuDLB centers and another precipitate-related species were the main components in the bulk. We attributed the inhomogeneous depth profiles of the Cu species in the samples diffused above 800 °C to the out-diffusion of Cu atoms and their precipitation near the sample surface. The dissociation product of the CuDLB center denoted as the CuDLA center was occasionally produced by the diffusion of Cu below 600 °C due to the precipitation of interstitial Cu. On the basis of these observations, we discussed the formation kinetics and structures of the CuDLB and CuDLA centers.
Fabrication of Nonsintered Alumina–Resin Hybrid Films by Inkjet-Printing Technology
Authors: Jang Hun Woo , Kim Jihoon , Kim Hyo-tae , Yoon Youngjoon , Lee Sung-nam , Hwang Haejin , Kim Jonghee
Published: July 2010

We used the inkjet printing to fabricate alumina–resin hybrid films without a high temperature sintering process. Single- and co-solvent ink systems showing different evaporation behaviors were formulated in order to understand their impacts on the inkjet-printing of the alumina dots, lines, and films. The packing densities of the inkjet-printed alumina films from both ink systems were around 60% which is higher than the value obtained by other conventional methods. Since the high temperature sintering process was avoided, the polymer–resin was infiltrated through the inkjet-printed alumina films by the same inkjet printing as a binder. The microstructures of these hybrid films were investigated in order to confirm if the microvoids in the films were filled with the resin. The dielectric properties of these hybrid films such as relative permittivity and Q-value were measured in order to assess if these hybrid materials is applicable to three-dimensional (3D) system integration as ceramic package substrates.
Piezoelectric Loss Performance in Pb(Mg1/3Nb2/3)O3–PbTiO3 Single Crystals
Authors: Rajapurkar Aditya , Ural Seyit O. , Zhuang Yuan , Lee Ho-Yong , Amin Ahmed , Uchino Kenji
Published: July 2010

Lead magnesium niobate–lead titanate (PMN–PT) single crystals are a suitable replacement over conventional PZT-based ceramics in transducer applications because of their large electromechanical coupling factors (k > 0.90) and piezoelectric constants (d > 1000 pC/N). For single crystals, it is possible to modify the performance by suitable selection of the orientation, and appropriate composition changes or doping can be utilized to improve the mechanical quality factor Q
m. In this research, we report the piezoelectric loss performance in PMN–PT single crystals as a function of orientation, doping and vibration mode. The loss characteristics are based on mechanical quality factor Q
m as well as the Q values at resonance (Q
A) and anti-resonance (Q
B). The Mn-doping resulted in almost twice the enhancement of the mechanical quality factor Q
m and the maximum vibration velocity in comparison with the undoped samples.
Atomic Layer Deposition and Properties of Silicon Oxide Thin Films Using Alternating Exposures to SiH2Cl2 and O3
Authors: Lee Won-Jun , Han Chang-Hee , Park Jae-Kyun , Lee Youn-Seoung , Rha Sa-Kyun
Published: July 2010

We report the process for the atomic layer deposition (ALD) of silicon dioxide thin films on a silicon wafer by alternating exposures to SiH2Cl2 and O3. The growth kinetics of silicon oxide films was examined by varying reactant exposures at various deposition temperatures ranging from 250 to 450 °C. The deposition was governed by a self-limiting surface reaction, and the growth rate at 350 °C was saturated at 0.25 nm/cycle for SiH2Cl2 exposures of over 5×109 L (10-6 Torr·s). The chlorine content and the wet-etching rate in a diluted HF solution were reduced by increasing the deposition temperature. The films deposited at temperatures ranging from 350 to 450 °C exhibited excellent physical and electrical properties that were equivalent to those of silicon oxide films deposited at 760 °C by low-pressure chemical vapor deposition.
Development of a Generating System to Inspect Some Specific Types of Wrinkle
Authors: Hoang Huu Phuong , Ko Sung Lim
Published: July 2010

Research and development in radio frequency identification (RFID) and flexible displays is being actively conducted worldwide, which are produced using the roll-to-roll (R2R) system, known as “web processing”, on rolls of flexible plastic. To improve R2R performance and productivity, effective control and online supervision of web quality is needed. In this report, we present a system that independently generates and analyzes wrinkles. Wrinkles are defects caused by compressive stresses developed in the web. A machine vision system is able to capture an image that is generated through a well-defined line or shape from a laser beam passing through a transparent web. Based on the captured images, measurement software calculates three-dimensional (3D) information, including the height of the wrinkle on the web, and displays the images to show the shape of the web in real time. By using an area scan camera and machine vision laser, the proposed system may be set up easily and at low cost to inspect certain types of wrinkles.
Self Contact Organic Transistors
Authors: Inoue Jun-ichi , Wada Hiroshi , Mori Takehiko
Published: July 2010

Thin films of various organic semiconductors, such as pentacene, sexithiophene, copper phthalocyanine, and C60, as well as an organic charge-transfer salt (TTF)(TCNQ) [TTF: tetrathiafulvalene; TCNQ: tetracyanoquinodimethane] are laser-irradiated to form conductive films, which are identified by Raman spectroscopy and atomic force microscopy to be carbon. The resulting practically transparent films are as conductive as laser-sintered carbon films and show temperature-independent conductivity. Source and drain electrodes of organic field-effect transistors are patterned by this method; in these “self-contact” transistors, both the active layers and the electrodes are derived from the same organic film. The laser-sintered carbon films are also utilized for organic single-crystal transistors based on rubrene and TCNQ.
Three-Dimensional Display System Based on Integral Imaging with Viewing Direction Control
Authors: Shin Minyoung , Baasantseren Ganbat , Kwon Ki-Chul , Kim Nam , Park Jae-Hyeung
Published: July 2010

We propose a three-dimensional display system based on integral imaging with viewing direction control. In the proposed method, 4-f illumination optics with a dynamic aperture are used to direct the displayed three-dimensional images to the viewer. It is also possible to control the divergence or convergence of the illumination for an optimized display of real or virtual images. The principle of the proposed method was verified experimentally.
Fabrication of Organic Spin-on-Glass Microring Resonator with a Narrow Gap between a Microring Resonator and a Waveguide Using Nanoimprint Lithography
Authors: Okamoto Hiroyuki , Yamaguchi Kenzo , Nakamatsu Ken-ichiro , Sogabe Hidenori , Matsui Shinji , Haraguchi Masanobu , Okamoto Toshihiro , Fukui Masuo
Published: July 2010

A microring resonator with a narrow gap between a waveguide and a microring resonator has been fabricated by using nanoimprint lithography. An organic spin-on-glass has been used as the material for the microring resonator. The outer diameter of the microring resonator is 20 µm and the coupling gap between the straight waveguide and the microring resonator is 40 nm. The filtering characteristics of the microring resonator have been evaluated using a metal halide lamp. The free spectral range is 3.9 nm and the Q-factor is 310. The structure of the microring resonator with a narrow gap can be used as a fundamental component of optical devices.
Anisotropic Diffusion Filter Based Blob-Mura Defect Detection in Thin Film Transistor Liquid Crystal Display Panel
Authors: Song Young-Chul , Choi Doo-Hyun
Published: July 2010

In this paper, an anisotropic diffusion filter was employed to extract a background image in a thin film transistor liquid crystal display (TFT-LCD) panel image. The background image extracted by an iterative filtering was simply subtracted from a test image to detect blob-Mura defects. To reduce a processing time, we simply modified a conventional anisotropic diffusion filter and evaluated its results. The black and white bob-Mura defects which were included in the same image could be detected separately using only threshold values. Through simulation it was verified that the proposed method has a superior capability of detecting blob-Mura defects.
Nanocrystalline Films Formation of 4,7-Bis(4-triphenylamino)benzo-2,1,3-thiadiazole through Electrophoretic Deposition
Authors: Zhu Yuanyuan , Si Zhengkai , Qian Lingfeng , Xue Minzhao , Sheng Qiaorong , Zhang Qing , Liu Yangang
Published: July 2010

The nanocrystalline films of an amorphous triphenylamine derivative have been firstly formed by a facile electrophoretic deposition (EPD) method from a solution of protonated 4,7-bis(4-triphenylamino)benzo-2,1,3-thiadiazole. The films are composed of nanoparticles which diameters are controllably varied from 20 to 200 nm. Compared with spin-coating films, EPD films possess lower band gap and higher energy level of the highest occupied molecular orbital (HOMO), which means superior intermolecular charge-transfer ability and more excellent hole-transporting property. The facile method for preparing nanocrystalline films could also spread to other amorphous triphenylamine derivatives.
Magnetic and Magneto-Transport Properties of Nickel-Rich Ni–Mn–Ga Heusler Alloys
Authors: Pal Debabrata , Mandal Kalyan
Published: July 2010

Electrical resistivity, ρ of nickel-rich Ni2+x
Mn1-x
Ga has been measured up to a magnetic field of 8 T and within a temperature range from 4.2 to 300 K. At lower temperatures (4.2–70 K), thermal variation of ρ(T) follows a combination of -√T dependent term coming from electron–electron interaction and BT
2 term due to s–d interaction. At higher temperature region (up to ∼280 K), ρ(T) is interpreted in terms of electron–phonon and s–d interaction. A substantial jump in resistivity has been observed while the martensitic transformation takes place. A high negative magnetoresistance (∼8%) has been observed at room temperature due to a change of 8 T magnetic field for the sample Ni2.208Mn0.737Ga, where martensite–austenite structural and ferro–para magnetic transition temperatures almost coincide with each other. Magnetic properties of those samples have also been studied to understand their anomalous change in magnetic entropy and magnetoresistance.
Experimental Determination of Shear Stress induced Electron Mobility Enhancements in Si and Biaxially Strained-Si Metal–Oxide–Semiconductor Field-Effect Transistors
Authors: Weber Olivier , Takenaka Mitsuru , Takagi Shin-ichi
Published: July 2010

Electron mobility enhancements under uniaxial, biaxial and shear stress have been experimentally discriminated by applying mechanical stress to Si and biaxially strained Si/SiGe(001) n-channel metal–oxide–semiconductor field-effect transistors (MOSFETs). Additive stress effects on mobility enhancements among uniaxial, biaxial and shear stress for different biaxial strain levels are deduced and the physical mechanisms of these various stress-induced mobility enhancements are highlighted. It is found experimentally that the shear stress impact on mobility in Si is fully additive to the biaxial tensile stress electron mobility enhancement. The shear stress, with its band warping mechanism, is thus effective to boost the electron mobility and to overcome the saturation of the biaxial stress mobility enhancement with its valley population mechanism. The warping of the 2-fold valleys and the effective mass change induced by the shear stress component included in <110> uniaxial stress is experimentally quantified in this study. The 0.19m
0 transverse effective mass m
t of 2-fold valleys valleys is found to be reduced by 10% for 400 MPa shear stress.
Electrically and Continuously Tunable Optical Delay Line Based on a Semiconductor Laser
Authors: Wu Fang-Ming , Peng Peng-Chun , Lin Jason , Lin Gong-Ru , Chi Sien
Published: July 2010

This investigation experimentally demonstrates the feasibility of the electrically and continuously tunable optical delay line using a semiconductor laser. The time delays for a 10 Gbps data signal are electrically delayed by adjusting the bias current of laser, and the maximum delay is approximately 41 ps. We also measure the bit error rate against the receiver power by various bias currents and wavelength detuning (Δλ). Measurements are made to verify the feasibility to use in optical communication systems.
Turn-Around Phenomenon in the Degradation Trend of n-Type Low-Temperature Polycrystalline Silicon Thin-Film Transistors under DC Bias Stress
Authors: Liu Han-Wen , Chiou Si-Ming , Wang Fang-Hsing
Published: July 2010

In this research, the instability of n-type low-temperature polycrystalline silicon (poly-Si) thin-film transistors (LTPS TFTs) is investigated under DC bias stress and a unique phenomenon is observed. At a large gate stressing voltage and simultaneous low to moderate drain biasing voltages operating in a linear region, a turn-around phenomenon is observed in the on-current (I
on) degradation trend of the TFT characteristics, resulting from the increase in maximum transconductance (G
m,max). However, under a larger drain stressing voltage, the turn-around phenomenon of the I
on degradation trend is observed to disappear owing to the extensive increases in threshold voltage (V
th) and trap state density (N
trap) in a channel, which cause the TFTs to deteriorate monotonically.
Impact of Source Junctions on the Performance and Cycling-Induced Degradation of Split-Gate Flash Memory
Authors: Zhao Wei , He Yue-Song , Huang Chunchieh , Mei Len
Published: July 2010

The impacts of different source junctions on the program/erase speed and cycling degradation are studied in details for split-gate memory using source-junction-side FN erase and source-side injection program. The device with pure phosphorous source junction has faster program but slower erase speed than that with phosphorous plus arsenic source junction, mainly because of stronger coupling between floating gate and pure phosphorous junction. During program/erase cycling, the memory cell with phosphorous junction shows much higher program-V
T rise but less erase-V
T increase than that with phosphorous-plus-arsenic junction. For the phosphorous junction, it is found the cycling-induced damage is mainly caused by program operation near the injection point. For the phosphorous-plus-arsenic junction, however, program and erase generate almost equal amount of damage near the injection point and the source junction, respectively. Anneal after phosphorous-plus-arsenic implant improves cycling performance due to less abrupt junction.
Characteristics of a Multiple Alloy Nanodot Memory with an Enhanced Charge Storage Capability
Authors: Song Yun Heub , Bea Ji Chel , Tanaka Tetsu , Koyanagi Mitsumasa
Published: July 2010

A nano-floating gate memory structure with a controllable large threshold voltage window using the Fowler–Nordheim (FN) tunneling program and erasing is proposed. This structure has multiple dot layers composed of a uniform single alloy dot layer in the surrounding silicon dioxide layer and a uniform interoxide layer between these dot layers. Here, we confirmed that multiple alloy FePt nanodot layers provide more charge storage than a single layer, which gives a larger memory window. Thus, multiple nanodot layers can store more charges corresponding to the number of layers with the optimization of several parameters, such as blocking oxide layer thickness. In addition, high operation voltages, low operation speeds due to a thick blocking oxide layer, and the poor retention related to the device structure were revealed, and the improvement of this issue was also discussed. Despite several issues, it is expected that a multiple FePt nanodot memory using FN tunneling will be a candidate structure for a future flash memory because of its larger memory window.
An Analytical Model of Surface Electric Field Distributions in Ultrahigh-Voltage Buried P-Top Lateral Diffused Metal–Oxide–Semiconductor Devices
Authors: Sheu Gene , Yang Shao-Ming , Chang Yi-Fong , Tsaur Shyh Chang
Published: July 2010

In this paper, we present an analytical model for determining surface electric field distributions in buried P-top lateral-diffused metal–oxide–semiconductor (LDMOS) devices with dual conduction and an enhanced dual conduction layer. The model is based on Poisson's two-dimensional solution and gives closed-form solutions for the surface potential and electric field distributions as functions of structural parameters and drain bias. All analytical results are verified by simulation results obtained from MEDICI and previous experimental data, confirming the validity of the model. In addition, a novel 800 V diffused metal–oxide–semiconductor (DMOS) with enhanced dual conduction paths above a buried P-top device is also presented. The enhanced dual conduction paths reduce on-state resistance by 22% as compared with state-of-the-art dual conduction paths and thin silicon-on-insulator (SOI) technologies. An R
on of less than 125 mΩ cm2 is achieved with 809 and 782 V off- and on-states breakdown voltages, respectively, at V
g = 5 V.
Secret Key Distribution Protocol for Practical Optical Channels Using a Preshared Key and Phase Fluctuations
Authors: Tomaru Tatsuya
Published: July 2010

A practical secret-key-distribution protocol using general phase fluctuations is described. A preshared key is assumed and is used only inside a transmitter and a receiver. The probabilistic property of signal-light fluctuations works with the preshared key to produce a difference in bit-error rate between a receiver and an eavesdropper. Using the difference, new secret keys are generated information theoretically although a preshared key is used. The probabilistic property of signal-light fluctuations is essential in this protocol, and classical fluctuations as well as quantum fluctuations are applicable. Because signal states are classical, the system becomes tolerant of loss and amplification.
Properties of Si Nanowires Synthesized by Galvanic Cell Reaction
Authors: Kobayashi Yasushi , Adachi Sadao
Published: July 2010

A galvanic cell reaction is used to synthesize Si nanowires (SiNWs) in AgNO3/HF solution at 30 °C for 60 min. The AgNO3 concentration ise varied from M=0.0001 to 0.6 mol/L in aqueous HF solution (5 mol/L). Vertically well-aligned SiNW arrays are found to be formed in the limited AgNO3 concentration range of M∼0.02–0.08 mol/L. The maximum nanowire length is ∼35 µm (M∼0.05 mol/L). The photoluminescence (PL) spectra of the SiNWs exhibit a broad peak centered at ∼1.8 eV. Below M∼0.02 or above ∼0.08 mol/L, the solutions produce only roughened surfaces. No PL emission is observed from such surfaces. Passive HF etching of the SiNWs leads to the removal of the surface oxide overlayer and changes the wettability from highly hydrophilic (∼5°) to superhydrophobic (∼135°). Optical absorption and Fourier-transform infrared spectroscopy show that the SiNWs have an extremely large optical absorbability not only in the interband-transition region but also in the far-infrared spectral region.
Silicon-Containing Spin-on Underlayer Material for Step and Flash Nanoimprint Lithography
Authors: Takei Satoshi , Ogawa Tsuyoshi , Deschner Ryan , Jen Kane , Nihira Takayasu , Hanabata Makoto , Willson C. Grant
Published: July 2010

Nanoimprint lithography is a newly developed patterning method that employs a hard template for the patterning of structures at micro- and nanometer scales. This technique has many advantages such as cost reduction, high resolution, low line edge roughness (LER), and easy operation. However, resist peeling, defects, low degree of planarization, and low throughput issues present challenges that must be resolved in order to mass produce advanced nanometer-scale devices. In this study, the new approach of using a silicon-containing spin-on hard mask underlayer material with high adhesion by reacting methacrylate groups of the underlayer to the acrylate groups of resist material during ultraviolet irradiation was demonstrated to obtain the excellent patterning dimensional accuracy and increase the process latitudes. The performance of this process is evaluated by using step and flash imprint lithography. The obtained high adhesion between the underlayer and resist material was found to lead a silicon-containing underlayer material to excellent patterning dimensional accuracy and 80 nm straight profiles. We expect that the silicon-containing a spin-on hard mask material under organic resist will be one of the most promising materials in the next generation of nanoimprint lithography.
Structure and Mechanical Properties of Diamond-Like Carbon Films Prepared from C2H2 and H2 Mixtures by Pulse Plasma Chemical Vapor Deposition
Authors: Fujimoto Shinji , Akasaka Hiroki , Suzuki Tsuneo , Ohtake Naoto , Takai Osamu
Published: July 2010

Diamond-like carbon (DLC) films were prepared by dc pulse plasma chemical vapor deposition (CVD). The hydrogen flow ratio [H2/(C2H2+H2)] was varied from 0 to 0.75, and the pulse frequency was varied from 1 to 20 kHz. Then, the relationship between film structure and hardness was investigated. At H2/(C2H2+H2)=0, films prepared at 10 kHz have the greatest hardness because a further increase in pulse frequency leads to an increase in the number of regular sixfold ring structures in the film and excessive ion peening on the growth face. The hardness at H2/(C2H2+H2)=0.5 is greater than that at H2/(C2H2+H2)=0 because the effect of ion peening and the number of regular sixfold ring structures at H2/(C2H2+H2)=0.5 are suitable for fabricating hard films. In contrast, at H2/(C2H2+H2)=0.75, the hardness is lower than that at H2/(C2H2+H2)=0 because of the reduced effect of ion peening; thus, the effect of an increase in the number of polymer bonds becomes significant.
Effect of Cation Substitution on Bipolar Resistance Switching Behavior in Epitaxially Grown NiO Films
Authors: Kim Hoonmin , Lee Seungran , Bak Junghoon , Jo Myungrae , Park Yun D. , Char Kookrin
Published: July 2010

Epitaxial NiO films (epi-NiO) were successfully doped with Al by performing sequential deposition of NiO and AlO
x
by pulsed laser deposition. Surface morphology and crystallinity were confirmed by atomic force microscope images and X-ray diffraction, indicating that the samples were grown epitaxially. Resistance switching (RS) phenomena of Al-doped NiO films were investigated using epitaxial SrRuO3 (SRO) and CaRuO3 (CRO) as the bottom (BE) and top electrode (TE), respectively. When the epi-NiO/SRO interface was modified by inserting either a 1-nm-thick epitaxial AlO
x
layer or a 5-nm-thick epitaxial 10% Al-doped NiO (Al0.1Ni0.9O
x
) layer, the RS of epi-NiO remained unchanged. However, when the CRO/epi-NiO interface was modified by inserting a 1-nm-thick epitaxial AlO
x
layer or a 5-nm-thick Al0.1Ni0.9O
x
layer, switching behavior was significantly changed; in the case of the 1-nm-thick epitaxial AlO
x
layer, the switching behavior completely disappeared, while in the case of 5-nm-thick Al0.1Ni0.9O
x
layer, number of cells which exhibited RS was drastically decreased. The switching phenomena may be suppressed due to the presence of Al cations whose free energy for oxidation is much lower than that of Ni. Our experimental results suggest that oxygen ions migration at the TE/epi-NiO interface may play a critical role in bipolar RS of epi-NiO. The relation between RS and free energy for oxidation is discussed.
Oxygen Adsorption and Magnetic Properties of Ultrathin Co/Ir(111) Films
Authors: Ho Huei-Ying , Tsay Jyh-Shen , Chen Yu-Shan
Published: July 2010

During oxygen exposure to ultrathin Co/Ir(111) films, both the oxidative process and physical adsorption occur. The diffusion length of oxygen is around two monolayers of Co. Within this thickness, Co films are almost oxidative and ferromagnetism disappears. For thicker films with nanometer thickness, after completing the oxidative process at the beginning of oxygen exposure, the physical adsorption becomes a major process. By controlling the amount of further exposure to oxygen, the coercive force in the polar configuration can be adjusted while keeping the Kerr rotation at a nearly constant value.
Fluorine Penetration into Amorphous SiO2 Glass at SF6 Atmosphere Using Q-Switched Nd:YAG and Excimer Laser Irradiations
Authors: Dehghanpour Hamid Reza , Parvin Parviz
Published: July 2010

At low pressures up to 0.1 mbar, the evidence of simultaneous SF6 gas decomposition and the morphology alteration on amorphous SiO2 glass have been investigated using various laser irradiations at typical wavelengths, i.e., ultraviolet (UV; 193 nm), visible (532 nm), and near infrared (NIR; 1064 nm). The instrumental micro-analysis of the surface were carried out by a number of instruments such as laser breakdown spectroscopy (LIBS), scanning electron microscopy (SEM), Rutherford back scattered spectroscopy (RBS), wavelength dispersive X-ray (WDX) mapping, energy dispersive X-ray (EDX) microanalysis and photo-spectrometry accordingly. It was shown that the excimer laser at shorter wavelengths induces microstructuring on glass mainly due to the surface UV photoablation and the subsequent collisional SF6 decomposition. Conversely, at the longer wavelengths such as the fundamental and second harmonic generation of a Q-switched Nd:YAG laser, the treatment of the target is done based on the micro-plasma induced ablation and the following electron-impact SF6 decomposition.
Characteristics of Electron Emission from a (Pb,La)(Zr,Ti)O3Ferroelectric Cathode
Authors: Seo Minsu , Hong Kimin
Published: July 2010

The properties of electron emission from a poled lead lanthanum zirconate titanate (PLZT) ferroelectric cathode have been investigated on the dependence of operating parameters such as the driving voltage, the vacuum pressure, the diode gap distance, and the diode acceleration voltage. The threshold electric field for electron emission from the cathode is about 6 kV/cm and the emitted current increase with increase in the driving voltage. A maximum current of 37 A/cm2has been detected when the driving voltage is -1.4 kV and the gap distance is 20 mm. The electron emission is considered to be initiated by field emission and then possibly be enhanced by the surface plasma. To confirm the detailed emission process, however, further experimental study should be necessitated.
Generation of Dielectric Barrier Discharge Plasma in Supercritical Argon for Material Synthesis
Authors: Suga Yosuke , Nakajima Tsuyoshi , Watanabe Toshiyuki
Published: July 2010

Plasma discharge was generated by high-frequency (HF) power in supercritical argon (critical pressure: 4.86 MPa, critical temperature: 150.7 K). Dielectric barrier discharge (DBD) enabled us to continue to generate a stable plasma even in high-pressure argon in more than 1 h by using parallel plate electrodes. Furthermore, a discharge plasma at a high pressure was generated in a wide area (150 mm2) between these electrodes for material synthesis. From optical emission spectra of argon at atmospheric pressure to critical pressure, it was observed that the plasma at a high pressure generated the same active species as the plasma at a low pressure. A weak broadening of plasma emission spectra was observed when pressure increased. Moreover, a carbon thin film was synthesized from n-pentane by using the novel reaction field of DBD. The carbon thin film was analyzed by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and Raman spectroscopy.
Surface Loss Probability of Nitrogen Atom on Stainless-Steel in N2Plasma Afterglow
Authors: Takashima Seigo , Takeda Keigo , Kato Satoshi , Hiramatsu Mineo , Hori Masaru
Published: July 2010

We investigated the loss kinetics of nitrogen (N) atoms in a N2plasma afterglow using a vacuum ultraviolet absorption spectroscopy technique with an atmospheric-pressure microdischarge hollow cathode lamp. The decay curves of N atom density were fitted with single exponential functions at pressures from 1.33 to 13.3 Pa. The dependence of the decay time constant on the pressure showed that the N atoms were predominantly lost through diffusion to the wall surface. The surface loss probability of N atoms on stainless-steel based on the decay time constant as a function of pressure was estimated to be 0.03.
Adhesion and Diffusion Barrier Properties of Ta Films Fabricated by Auxiliary Plasma Assisted Bias Sputtering
Authors: Kim Yong-Chul , Lee Do-Seon , Lee Won-Jong
Published: July 2010

The formation of an adhesion/barrier layer and a seed layer by sputtering techniques followed by electroplating has been one of the most widely used methods for filling through-Si vias (TSVs) for three-dimensional packaging. In this research, the adhesion and diffusion barrier properties of Ta films deposited by auxiliary plasma assisted bias sputtering were investigated. As substrate power increased, the deposition rate and sheet resistance of the film decreased while the surface roughness and degree of crystallinity increased owing to the bombardment of energetic ions on the growing film. The strength of adhesion between the Cu/Ta film and the SiO2/Si substrate was quantitatively measured by a topple test and a 180° peel test. The highest adhesion strength was obtained when the thickness of the Ta film was within 20–40 nm, which was about two times higher than that in the case without a Ta adhesion layer. The application of a substrate power of over 0.51 W/cm2 caused 20–40% enhancement of the strength of adhesion between the Cu/Ta film and the SiO2/Si substrate. The enhancement of adhesion strength was attributed to intermixing in the interface region, the increase in surface roughness, and the removal of contaminants by the bombardment of energetic ions. The improved barrier property of the Ta film against Cu diffusion could be obtained by applying an appropriate substrate power during the deposition of Ta films.
Measurement of Macrophage Adhesion at Various pH Values by Optical Tweezers with Backward-Scattered Detection
Authors: Su Yi-Jr , Hsu Long
Published: July 2010

Optical tweezers have emerged as a powerful tool with broad applications in biology and physics. In force-measuring applications, the trapped bead position is usually accurately determined by forward-scattered detection. The current study discusses both backward-scattered detection and forward-scattered detection related to the linear detection range for a 3 µm bead and the distance between the two laser system focuses, confirming the optimum positions of the two focuses. The result indicates that the linear detection range of backward-scattered detection is longer than the forward-scattered one. Finally, this work investigates real-time adhesion force measurements between human macrophages and 3 µm trapped beads coated with lipopolysaccharides at various pH values by optical tweezers with backward-scattered detection.
Electrical Detection of Magnetic Vortex Chirality
Authors: Tanabe Kenji , Chiba Daichi , Ono Teruo
Published: July 2010

The electrical detection of chirality in a magnetic vortex, which is the curling direction of a magnetization structure, is reported. Two electrodes, which were placed on a NiFe microdisc at asymmetric positions with respect to the center of the disc, were used to measure the resistance between them. The magnetoresistance curves with opposite asymmetries due to the anisotropic magnetoresistance effect were observed depending on the chirality of the vortex state, indicating that the asymmetrically placed electrodes are useful for the electrical detection of chirality.
Morphologies of Pentacene Crystals Obtained by Physical Vapor Growth Technique
Authors: Jo Sadaharu , Takenaga Mitsuru
Published: July 2010

Three kinds of morphologies were observed in the pentacene crystals obtained by physical vapor growth, such as the whisker-type morphology, the plateletlike morphology with large parallelogram planes, and the plateletlike morphology with large dendritic planes. Plateletlike crystals have a common basal (001) plane, despite possessing different morphologies, that is, either the parallelogram or dendritic planes. The results of white-beam X-ray diffraction analysis revealed that the crystal qualities depended on the growth condition rather than on the crystal morphology.
Gigahertz Acoustic Spectroscopy by Micro-Brillouin Scattering
Authors: Kojima Seiji
Published: July 2010

An interesting problem on condensed matter in pure and applied sciences is the understanding of vibration and relaxation dynamics in the gigahertz range, especially cooperative motions in nonequilibrium states. In this work, we review the progress in micro-Brillouin scattering spectroscopy (MBSS) for condensed matter. MBSS has been achieved by combining a tandem multipass Fabry–Perot interferometer and an optical microscope to probe the gigahertz dynamics in a microscopic area/sample. It provides the fundamental information on a variety of vibration and relaxation processes and elementary excitations related to the lattice instability of structural phase transitions of normal and relaxor ferroelectrics, nonequilibrium cooperative dynamics of liquid–glass transitions and the hydration dynamics of protein glass transitions. The most relevant studies on the various aspects of gigahertz dynamics are provided.
High Temperature Brillouin Scattering of Potassium Borate Glasses
Authors: Kawashima Mitsuru , Matsuda Yu , Aramomi Syunsuke , Kojima Seiji
Published: July 2010

High temperature elastic properties of potassium borate glasses, xK2O·(100-x)B2O3 (x=4, 10, 14, 20, 28, and 34 mol %), have been investigated between 20 and 1100 °C by Brillouin scattering. Longitudinal sound velocity of the glasses changes only slightly up to the glass transition temperature (T
g), and, with further heating above T
g, it decreases markedly. This sudden decrease in sound velocity is caused by structural rearrangements that make glass networks soft above T
g. With an increase in K2O composition, the slope of sound velocity just above T
g increases. The composition dependence of the fragility of potassium borate glass is suggested on the basis of the slope. The activation energy of the relaxation process of 28K2O·72B2O3 measured by Brillouin scattering is estimated to be 6.84 kcal/mol, which is comparable to the energy of formation of a boroxol ring structure in a liquid phase.
Analysis of Nanomechanical Antenna Structure Resonator Using Transfer Matrix Method and Examination of Its Frequency Gap
Authors: Itoh Hideaki , Tatebe Hiroshi
Published: July 2010

We analyzed the frequency gap of an antenna structure resonator, a coupled resonator of the central clamped-clamped beam with forty vibrating clamped-free beams on both sides of the clamped-clamped beam, from the standpoint of the propagating flexural wave. By describing the antenna structure resonator as repeated T-shaped units in a row, an input-output relation of the propagating flexural waves between any neighboring two of the repeated T-shaped units was derived using the transfer matrix method. We elucidated the reason why the frequency gap occurred in the resonant frequency characteristics of the antenna structure resonator by calculating the attenuation of the flexural waves and the dispersion relation between the frequency and wave number of the waves using the Bloch wave function under the periodic boundary condition of these units, which was a fairly good approximation capable of being applied to the antenna structure resonator.
Melting and Discharge Phenomena of Breaking Ag Contacts Using a Precisely Controlled Piezoelectric Actuator
Authors: Kudo Takayuki , Wakatsuki Noboru
Published: July 2010

Using a laminated ceramic piezoelectric actuator for a very slow (4.5 µm/s) precisely controlled make/break operation, the contact voltage V
c, the contact current I
c, and the amounts of residue of the melt and discharged surface and discharge for breaking hinge relays with Ag-contacting electrodes were measured. To control mechanical conditions, we used a movable electrode with a finely shaped convex surface (radius of curvature: 0.5 mm) and a flat fixed electrode. Every make/break operation causes surface irregularity. Therefore, the operation was performed only once. In order to measure the area of the contacted surface after metal melting and arc ignition, V
c and I
c was adjusted to be 25 V and 1.2 A, respectively. Even when V
c and I
c were larger than the minimum arc voltage and minimum arc current, respectively, electric discharge was spontaneously suppressed below 130 µs. The residues of discharge were multiple scars with radii in the range of 100 µm, which had a black and/or white rectangular convex or concave shape.
Recognition of Optical Layered Binary Phase Shift Keying Labels Using Coherent Acoustooptic Processor for Hierarchical Photonic Routing
Authors: Goto Nobuo , Miyazaki Yasumitsu
Published: July 2010

Wavelength-selective optical processing using collinear acoustooptic (AO) switches will be useful in photonic routing systems. We have studied the applications of this processing to optical label recognition in label routers. We propose the recognition of hierarchical routing labels encoded in the binary-phase-shift-keying (BPSK) format using an AO processor consisting of optical delay waveguides and parallel double-stage AO switches. Using wavelength-multiplexed hierarchical labels, simple processing using the AO processor can be realized. The recognition characteristics are analyzed and numerically confirmed by computer simulation.
Effect of Circular Assumption on Active Element Size Measurement for Hydrophone Sensitivity Calibration Using Narrow Beam
Authors: Yoshioka Masahiro , Matsuda Yoichi , Kikuchi Tsuneo
Published: July 2010

The effect of the hydrophone active element size measured assuming circular geometry on the sensitivity calibration using a narrow beam is investigated. It is confirmed that there is a hydrophone that has a noncircular effective active element despite its circular geometry, by measuring the effective radii of a hydrophone for the direction turned with a step of 5° on the active element. As a result of calibrating the hydrophone sensitivities using a focused beam and measured element radii, the sensitivity dispersion due to the circular assumption is identified as an important uncertainty source of the measurement.
Use of Trapped-Energy Mode of Backward-Wave-Type Thickness Vibration for Liquid-Level Sensing
Authors: Seto Shuichi , Horiuchi Shuhei , Yamada Ken
Published: July 2010

The authors have presented a new technique that employs a piezoelectric thickness vibrator operating in a trapped-energy mode for detecting a small-scale variation in liquid level. In this study, the feasibility of applying backward-wave-type energy trapping to liquid level sensing is investigated. It has been found that backward-wave-type energy trapping shows a sensing property slightly different from those obtained using conventional trapped-energy modes. Gradual variations in resonance characteristics with liquid level have been observed for backward-wave-type energy trapping when the liquid surface is in the surrounding electroded region.
Estimation of Sound Velocity Distribution Using Sectional Near-Field Acoustical Holography and Global Search
Authors: Ohbuchi Takeshi , Ebihara Tadashi , Mizutani Koichi , Wakatsuki Naoto , Masuyama Hiroyuki
Published: July 2010

We propose a method of estimating sound velocity distribution by the combined use of near-field acoustical holography (NAH) and optimization. In this fundamental research, the sound velocity varies only in the z-axis, and the sound velocity is a continuous distribution. In addition, the sound velocity varies in the range of a sound velocity that can be varied in water. For the estimation of sound velocity distribution, we proposed a modified method of NAH to calculate in an inhomogeneous medium called Sectional NAH (SNAH). In SNAH, a calculation space is discretized into a number of sections so that NAH can be used approximately in each section. The calculation result by SNAH in an inhomogeneous medium agreed well with the calculation result by finite element method (FEM). Here, the sound velocity distribution is estimated. Firstly, sound fields are measured. Next, the sound field at one of the measured planes is calculated from the other measured sound fields by SNAH with initial sound velocity. Then, the difference between the calculated and measured sound fields is minimized by optimizing the sound velocity distribution by the multi start downhill simplex method. Sound velocity distributions given as linear and Gaussian distributions were estimated in simulations by SNAH and FEM. The validities of our proposed methods were confirmed by simulations.