bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of Structural Disorder and Charge Carriers on the Magnetic and Transport Properties of Sr0.7R0.3CoO3-δ (R = Y or Dy0.45Er0.55)
Authors: Takami Tsuyoshi , Cheng Jinguang
Published: January 2011

Research into the magnetic and transport properties of Sr0.7
R
0.3CoO3-δ (R = Y or Dy0.45Er0.55) having tetragonal I4/m
m
m symmetry with oxygen-deficient CoO2(1-δ) (001) planes alternating with CoO2 planes, as in the brownmillerite structure, has shown that the localized 3d6 Co(III) configurations are not easily oxidized and that the n-type conduction is not realized owing to the small polaron Co(II). A ferromagnetic transition temperature decreases with increasing oxygen deficiency as well as with increasing disorder at the R site. The electrical resistivity (ρ) decreases with increasing carrier concentration (n), whereas ρ is independent of the R-site disorder. The thermoelectric power, on the other hand, varies with both n and the disorder. Although the phonon contribution to the thermal conductivity is suppressed, the polaronic conduction makes these compounds unsuitable for thermoelectric-power applications.
Appearance of a Large Magnetization at Elevated Temperatures in Nearly Antiferromagnetic α-Fe2O3
Authors: Yui Yuhki , Ito Shimpei , Mizuguchi Jin , Ishikawa Yoshihisa , Kiyanagi Ryoji , Noda Yukio
Published: January 2011

A significant magnetization of about 10–20 emu/g has been observed under a magnetic field of 5 kOe in nearly antiferromagnetic α-Fe2O3 when heated at 350–500 °C in air. The present outstanding effect that contrasts with the temperature dependence of the Curie's law has been investigated on the basis of various temperature-dependent measurements of magnetization, diffuse reflectance spectra, electrical conductivity, Seebeck potential, X-ray and neutron diffractions, differential scanning calorimetry, thermogravimetry, and X-ray photoelectron spectra. The color of α-Fe2O3 is found to drastically change from vivid red to black at about 380 °C, and this is closely correlated with the appearance of the magnetization. The color change is due to the formation of oxygen defects called a color center (i.e., F-center). Then, the absence of the intervening O2- ions greatly disturbs the superexchange interaction that is responsible for the anti-parallel spin alignment in the Fe–O–Fe (cation–anion–cation) system. As a result, the uncoupled spins can be aligned in parallel due to the direct exchange interaction between various nearest-neighboring Fe3+ ions, resulting in the appearance of the large magnetization at elevated temperatures.
Basic Study on the Radio Frequency Characteristics of the Transmission Lines Employing Periodically Perforated Ground Metal on GaAs Monolithic Microwave Integrated Circuit and Their Equivalent Ciruits
Authors: Yun Young , Ju Jeong-Gab , Kim Hong Seung
Published: January 2011

In this work, basic characteristics of transmission line employing periodically perforated ground metal (PPGM) were investigated using theoretical and experimental analysis. Concretely, bandwidth and impedance were investigated using theoretical analysis, and wavelength and effective permittivity were extracted from experimental results. In addition, insertion loss and isolation characteristics were investigated using equivalent circuit analysis. For simplification of design process, equivalent circuits for the PPGM cell were extracted, and all circuit parameters were expressed by closed-form equation. Above results indicate that the transmission line employing PPGM is a promising candidate for a development of matching and passive elements on monolithic microwave integrated circuit (MMIC) including wireless communication circuit and compound semiconducting devices such as high electron mobility transistor (HEMT), diamond field effect transistor (FET) and light emitting diode (LED).
Impact of (Quasi-)Ballistic Transport on Operation of Complementary Metal–Oxide–Semiconductor Inverters Based on Fully-Depleted Silicon-on-Insulator and Nanowire Devices
Authors: Martinie Sébastien , Munteanu Daniela , Carval Gilles Le , Dura Julien , Jaud Marie-Anne , Barraud Sylvain , Autran Jean-Luc
Published: January 2011

We have developed a numerical simulation methodology to analyze the impact of both device architecture and transport properties on static circuit performance. Firstly, to simulate ballistic transport, we have enhanced the pioneering approach of quasi-ballistic mobility proposed by Rhew and Lundstrom and introduced it into a technology computer aided design (TCAD) simulator. Secondly, we have introduced the remote Coulomb scattering (RCS) limited mobility into the effective mobility and calibrated our model using experimental mobility data. We have used our approach to simulate two ultimate architectures: fully-depleted (FD) silicon-on-insulator (SOI) metal–oxide–semiconductor field-effect transistor (MOSFET) (with either thin or thick buried oxide) and nanowire MOSFET. Finally, we have analyzed the impact of both transport properties and electrostatic control on the noise margin (NM) of complementary metal–oxide–semiconductor (CMOS) inverter.
Characterization of Short-Pulse Generation Using Traveling-Wave Field-Effect Transistors
Authors: Narahara Koichi
Published: January 2011

Pulse propagation on traveling-wave field-effect transistors (TWFETs) is investigated for the generation of short pulses. In a properly designed TWFET, when a decreasing voltage pulse is applied to the gate line and an increasing one is simultaneously applied to the drain line, the pulses experience great shortening. Therefore, a TWFET operates as a short-pulse generator. In this paper, how the width of the finally obtained pulse depends on the device parameters, including the inductive and capacitive coupling coefficients between the gate and drain lines is clarified, and the design criteria of a TWFET as a pulse generator are described, together with several results of numerical calculations for examining its potential.
Superior Reliability of Gate-All-Around Polycrystalline Silicon Thin-Film Transistors with Vacuum Cavities Next to Gate Oxide Edges
Authors: Liu Han-Wen , Chiou Si-Ming , Huang Hui-Ching , Gong Jeng , Wang Fang-Hsing
Published: January 2011

The electrical characteristics and reliability of n-type gate-all-around (GAA) polycrystalline silicon thin-film transistors (poly-Si TFTs) with vacuum cavities next to the gate oxide edges are investigated. This novel structure is successfully fabricated by spacer formation, partial wet etching of a gate oxide, and in situ vacuum encapsulation. The electrical characteristics of the GAA poly-Si TFTs with vacuum cavities are superior to those of traditional GAA poly-Si TFTs because the vacuum cavity serves as an offset region to decrease the leakage current in the OFF state and as a field-induced drain (FID) to sustain the on-current in the ON state. In addition, regardless of whether static or dynamic electrical stress is imposed on these devices, the GAA poly-Si TFTs with vacuum cavities exhibit superior reliability to traditional ones owing to the simultaneous reduction of vertical and lateral electric fields near the drain junction during bias stressing due to the greater equivalent gate oxide thickness on the gate electrode edges.
In-situ Crystal Structure Analysis of Cobalt Nanocompounds Synthesizing Graphite at High Temperatures
Authors: Yahiro Takanori , Takai Yoshizo
Published: January 2011

The crystal structure change of cobalt nanosized compounds in the graphitization process at high temperatures has been examined by in-situ transmission electron microscopy (TEM). The nanocompounds possess Co3O4 structure at room temperature but the structure changed to CoO at 600 °C, in TEM. At 600–800 °C, the nanoparticles started to aggregate with each other and move around while changing their shapes like a liquid. Accompanying the movement, the nanoparticles absorbed amorphous carbon and synthesized poly-graphite and left the graphite behind. The aggregated particles possessed a β-Co structure at the beginning, but the structure changed to a Co3C structure when the particles stopped moving and synthesizing graphite. Such a structural change occurred not suddenly but gradually while changing the lattice constants continuously, and the particles continued synthesizing graphite at all the transient stages from β-Co to Co3C.
Correlation between Oxygen Composition and Electrical Properties in NiO Thin Films for Resistive Random Access Memory
Authors: Nishi Yusuke , Iwata Tatsuya , Kimoto Tsunenobu
Published: January 2011

Admittance spectroscopy measurement has been performed on NiO
x
thin films with various oxygen compositions (x = 1.0–1.2) in order to characterize localized defect levels. The activation energy and concentration of localized defect levels in NiO
x
films with low oxygen composition (x≤1.07) are 120–170 meV and lower than 2×1019 cm-3, respectively. The result of current–voltage measurement of Pt/NiO
x
/Pt structures indicated that samples with high oxygen composition (x≥1.10) did not show resistance switching operation, whereas samples with low oxygen composition (x≤1.07) did. The best oxygen composition of NiO
x
thin films for realizing repeatable and stable resistance switching operation turned out to be 1.07.
Super Smooth Modification of Al2O3 Ceramic Substrate by High Temperature Glaze of CaO–Al2O3–SiO2 System
Authors: Zhang Jihua , Zhen Shanxue , Yang Lijun , Lou Feizhi , Chen Hongwei , Yang Chuanren
Published: January 2011

The rough surface of ceramic substrate is an obstacle for the scale down of line-width for thin film passive integrated devices (PID). In this paper, a modification method for Al2O3 ceramic substrate with super smooth in surface was proposed. Coating a layer of CaO–Al2O3–SiO2 (CAS) glass was performed to flat the rough surface of alumina substrate by sol–gel method. It was found that addition of 0.06% V2O5 can inhibit the recrystallization of the glaze. The root-mean-square (RMS) roughness of the glazed substrates reached a surprising flatness as small as 0.5 nm, and its melting temperature is higher than 1300 °C. This substrate with super flatness and high temperature endurance may be promising for high performance thin film devices.
Novel Air-gap Formation Technology Using Ru Barrier Metal for Cu Interconnects with High Reliability and Low Capacitance
Authors: Takigawa Yukio , Tarumi Nobuaki , Shiohara Morio , Soda Eiichi , Oda Noriaki , Ogawa Shinichi
Published: January 2011

A novel technology for obtaining low-capacitance Cu interconnects with air gaps has been proposed. Using a Ru barrier metal as a self-mask, a Cu interconnect was effectively protected from losing its cross-sectional shape during the intermetal dielectric etching process. The wiring capacitance with air-gaps was about 30% lower than that of the conventional low-k (k = 2.65)/Cu structure without air-gaps. The time-dependent dielectric breakdown (TDDB) lifetime of the air-gap interconnect with a Ru barrier was 100 times longer than that of the low-k/Cu structure. These results indicate that an air-gap interconnect with a Ru barrier metal can be an effective solution to boost the circuit operating speed and to reduce the power dissipation without the degradation of interconnect reliability for devices of 45 nm nodes and beyond.
Image-Noise Effect on Discrete Power Spectrum of Line-Edge and Line-Width Roughness
Authors: Hiraiwa Atsushi , Nishida Akio
Published: January 2011

The authors investigated the effect of scanning-electron-microscope image noise on the accuracy of line-edge-roughness and line-width-roughness (LER/LWR) statistics extracted from power spectral densities (PSDs). To do this, they numerically prepared pseudo-experimental PSDs of LWR using the Monte Carlo (MC) method. The estimation error η decreased with the total number N
ALL of width data points in the same way as that observed in the absence of the image noise. η first increased gradually with the image-noise intensity R but markedly when R went beyond the threshold value R
th determined by the ratio of the sampling interval Δy to the correlation length ξ. The PSDs with these R
th's had the same maximum-to-minimum ratio γ (= 10 in this study). The authors approximated η by B
N
ALL
-3/4(Δy/ξ)-3/8 [1+g(R,Δy/ξ,γ)], where B is 49. They also empirically determined the functional form of g(R,Δy/ξ,γ). Because these functions well fitted massive MC simulation results, they provide guidelines for setting up analysis conditions for securing arbitrarily prescribed accuracy.
Novel Modeling of Correlation between Two-Dimensional Registers in Large-Area Multilayered Roll-to-Roll Printed Electronics
Authors: Kang Hyun-Kyoo , Lee Chang-Woo , Shin Kee-Hyun
Published: January 2011

For the adaption of a roll-to-roll printing method to printed electronics, it is mandatory to increase the register control resolution. Therefore, it is necessary to derive a mathematical model of the register and to develop a controller to reduce register error. A correlation between the machine-direction (MD) and cross-direction (CD) registers was derived by considering both the lateral motion of a moving substrate and the transverse position of a printing roll. By the analysis of the correlation between MD and CD registers, a novel mathematical model of an oblique-machine-direction (OMD) register was derived. The OMD register is more critical in large-area roll-to-roll printing, as the OMD register error is proportional to the width of the substrate. The proposed model can be used to design an effective two-dimensional (2D) register controller that reduces the correlation between MD and CD registers. The proposed mathematical model was validated by numerical simulations and experimental verifications under various operation conditions using a multilayered direct gravure printing machine. The results show that the proposed OMD register model reasonably exposes the MD–CD register correlation.
Electrical Extractions of One Dimensional Doping Profile and Effective Mobility for Metal–Oxide–Semiconductor Field-Effect Transistors
Authors: Park Hyunho , Lee Kong-soo , Baek Dohuyn , Kang Juseong , So Byungse , Kwon Seok Il , Choi Byoungdeok
Published: January 2011

In this study, an attempt is made to provide a framework to assess and improve metal–oxide–semiconductor field-effect transistor (MOSFET) reliability from the early stage of the design to the completion of the product. A small gate area has very small capacitances that are difficult to measure, making capacitance–voltage (C–V) based techniques difficult or impossible. In view of these experimental difficulties, we tried electrical doping profiling measurement for MOSFET with short gate length, ultra thin oxide thickness and asymmetric source/drain structure and checked the agreement with simulation result. We could get the effective mobility by simple drain current versus drain bias voltage measurement. The calculated effective mobility was smaller than expected value and we explained some reasons. An accurate effective mobility for asymmetric source–drain junction transistor was successfully extracted by using the split C–V technique, with the capacitance measured between the gate and source–drain and between the gate and the substrate.
Observation of Optical Fluorescence of GaN Thin Films in an Inductively-Coupled Plasma Containing High Energy Electrons
Authors: Guo Ying , Nakamura Keiji , Zhang Jing , Nakano Yoshitaka , Sugai Hideo
Published: January 2011

In this paper we describe observation of optical fluorescence of GaN thin films in an inductively-coupled plasmas containing energetic electrons with an energy higher than several keV which was similar conditions of plasma treatments often used in plasma based ion implantation. Such high energy electrons are produced by sheath acceleration of secondary electrons induced by ion bombardment at a negatively-biased electrode. A current of a Langmuir probe located in such a plasma is investigated to examine how the high energy electrons behaves in the plasma. It was found that a step-like increment of probe current observed immediately after the negative high voltage application was proportional to discharge power, but slightly depended on the pulse target voltage. A sample of undoped GaN film was observed to emit significant optical fluorescence in the wavelength range of 370–390 nm corresponding to band gap energy of the GaN when the plasma contains the high energy electrons, the fluorescence intensity of the GaN film increased with the incident electron energy higher than a critical energy of ∼5 keV. These results suggested cathode luminescence technique will be used to detect a damage density of GaN substrate surface even in plasma conditions.
Extension of Binary-Collision-Approximation-Based Simulation Applicable to Any Structured Target Material
Authors: Takayama Arimichi , Saito Seiki , Ito Atsushi M. , Kenmotsu Takahiro , Nakamura Hiroaki
Published: January 2011

We have investigated plasma–surface interactions by performing molecular dynamics (MD) simulations. However, such simulations have a high computation cost and are limited to simulations of materials of nanometer order. In order to overcome this limitation, a complementary model based on the binary collision approximation (BCA) can be established. We employed the BCA-based simulation code ACAT and extended it to handle any crystalline or amorphous structure. The extended code, named “AC∀T”, stores the positions of all projectile and target atoms and the velocities of recoil atoms so that it can be combined with the MD code. It also has the potential to reproduce channeling phenomena. Thus, it is expected to be useful for the evaluation of channeling effects.
Synthesis of Tungsten Oxide Nanoslab Bundles by Microwave Plasma-Enhanced Chemical Vapor Deposition
Authors: Hsieh Yun Tsung , Hsueh Sen Hung , Chen Uei Shin , Huang Meng Wen , Shih Han C.
Published: January 2011

A large quantity of tungsten oxide nanoslabs was synthesized within 4 min by microwave plasma-enhanced chemical vapor deposition (MPECVD). The structural, geometrical, and chemical compositions of these nanoslabs were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), and Raman spectroscopy. The results of these characterizations confirmed that the nanoslabs with [010] as the major growth direction have a W18O49structure with thicknesses of 30–50 nm, widths of up to 300–500 nm, and, lengths of up to 800–2000 nm. In XRD spectra, the reflection peaks are representative of monoclinic W18O49. A vapor–solid (VS) mechanism was confirmed for this growth process because no catalyst was used in this growth process.
Low-Temperature Solid Phase Epitaxial Regrowth of Silicon for Stacked Static Random Memory Application
Authors: Lee Kong-Soo , Yeo Chadong , Yoo Dae-Han , Kim Seok-Sik , Moon Joo-Tae , Jung Soon-Moon , Son Yong-Hoon , Park Hyunho , Jeong Hanwook , Kim Kwang-Ryul , Choi Byoungdeog
Published: January 2011

Solid phase epitaxy (SPE) techniques have been studied to realize stacked static random memory (SRAM) devices. Among the candidates including epitaxial lateral overgrowth (ELO) and laser epitaxial growth (LEG) techniques, SPE is the most stable and cost-effective scheme since it is fulfilled by the deposition of amorphous silicon layers and the subsequent low temperature annealing using conventional furnace equipment which has been used for several decades in semiconductor fabrication. We introduced silicon seeds for the epitaxial realignment of amorphous silicon within the contact window by the selective epitaxial growth (SEG) of single-crystalline silicon. The role of process variables associated with channel silicon deposition on SPE was investigated. The efficiency of SPE was quantified by electron back-scatter diffraction (EBSD) measurement, which visualizes the fraction of the <100> orientation in a channel silicon layer. SiH4 ambient during the ramp-up stage in the deposition of amorphous silicon layers showed superior epitaxial realignment to N2 ambient, which was mainly due to the suppression of interfacial layer formation. Electrical characteristics such as on-current distribution and static noise margin indicated SPE to be feasible for high-density stacked SRAM application.
Structural, Electrical, and Optical Properties of SnO2:Sb Films Prepared on Flexible Substrate at Room Temperature
Authors: Lee Sung Uk , Boo Jin-Hyo , Hong Byungyou
Published: January 2011

In this study, antimony (6 wt %)-doped tin oxide (ATO) films were prepared on a poly(ether sulphone) (PES) flexible substrate by radio frequency (RF) magnetron sputtering at room temperature, with varying deposition parameters such as RF power and working pressure. The RF power was varied from 50 to 150 W in steps of 25 W. The working pressure was varied from 0.67 to 1.2 Pa in steps of 0.27 Pa at room temperature. The thickness of the deposited ATO films was about 200 nm. The (110), (101), (200), and (211) diffraction peaks were observed for the ATO films deposited with two different conditions. All the samples were found to be crystalline with a cassiterite tetragonal (rutile type) structure that has a preferred orientation in the (101) direction, which is structurally stable and exists mainly in nature. The ATO film deposited at a RF power of 125 W with a working pressure of 0.67 Pa showed the lowest resistivity of 6.9 ×10-3 Ω cm, and the optical transmittance was 80.1% in the visible wavelength range from 400 to 800 nm.
Improvement of Plasma-Assisted Molecular Beam Epitaxial Growth of Group III Nitrides on Si Controlling Radio Frequency Discharge Modes and Irradiation of Nitrogen Flux
Authors: Ohachi Tadashi , Yamabe Nobuhiko , Wada Motoi , Ariyada Osamu
Published: January 2011

A radio frequency inductively coupled plasma (rf-ICP) nitrogen discharge was investigated to improve group III nitride growth on Si substrates. Two modes of the rf-ICP discharge, low brightness (LB) and high brightness (HB) discharges, were successfully controlled through mode transition. Direct irradiation and indirect irradiation of nitrogen atoms were applied for the growth of group III nitrides. As an application of indirect irradiation of nitrogen atoms, the growth of β-Si3N4 using interface reaction epitaxy (IRE) was studied. As applications of direct irradiation of nitrogen atoms, activity modulation migration-enhanced epitaxy (AM-MEE) and plasma-assisted molecular beam epitaxy (PA-MBE), which are atomic layer epitaxy (ALE) methods, are demonstrated. These growth systems operate to realize a single-growth process from a Si substrate to an AlN or GaN epitaxial layer, i.e., through preparation of a double buffer (DBL) layer of AlN/β-Si3N4/Si after the growth of IRE β-Si3N4 and IRE AlN. The electron emission due to the self-ionization of nitrogen atoms on a negatively biased electrode is demonstrated to measure in situ direct and indirect nitrogen atom fluxes during the growth.
In situ Investigation of Growth Mechanism during Molecular Beam Epitaxy of In-Polar InN
Authors: Wang Ke , Yamaguchi Tomohiro , Araki Tsutomu , Yoon Euijoon , Nanishi Yasushi
Published: January 2011

A real-time investigation of In-polar InN growth by radio-frequency plasma-assisted molecular beam epitaxy has been conducted using laser reflection and reflected high-energy electron diffraction (RHEED). Laser reflection intensity is very sensitive to surface changes in the growth front. Clear reflection intensity changes have been observed for In-stabilized surface, In adlayer, and In droplet formation. Simultaneously, the envelope of reflection intensity variation shows interference oscillation due to the increasing InN thickness. Laser reflection intensity increases during In deposition and decreases during the following N irradiation, in contrast to RHEED intensity. In situ monitoring using both techniques has demonstrated complementary information on the growth front. On the basis of the observation from both techniques, the growth mechanisms and roles of the In adlayer and droplets in the InN growth are discussed.
Parametric Study for Selective Growth of Single-Walled Carbon Nanotubes in Plasma Enhanced Chemical Vapor Deposition
Authors: Nozaki Tomohiro , Karatsu Takuya , Yoshida Shinpei , Okazaki Ken
Published: January 2011

Carbon nanotube (CNT) growth mechanism in plasma enhanced chemical vapor deposition (PECVD) is presented. Previously developed atmospheric pressure glow discharge reactor was modified and used for this purpose. First, pressure-dependent transition (20–100 kPa) of CNT morphology was investigated with fixed input power (60 W) and different catalyst loading (Fe/Al2O
x
: 20 nm). High-purity, vertically-aligned single-walled CNTs (SWCNTs) were synthesized when capacitively coupled non-thermal plasma was generated at atmospheric pressure. On the other hand, fraction of double-walled and multi-walled CNTs increased as total pressure decreased. Although CNT growth rate was decelerated at reduced input power (5–20 W), SWCNTs were also synthesized in the root growth regime at 20 kPa. Plasma-generated reactive species are the important driving force of CNT growth; however, generation and transportation of those species must be properly suppressed for selective growth of single-, double-, and multi-walled CNTs.
Application of Carbon Nanotubes to Nylon Composite
Authors: Suzuki Tomoko , Inoue Sakae , Nojima Kazuhiro , Tsuchimoto Akiharu , Chen Beibei , Kumar Mukul , Ando Yoshinori
Published: January 2011

Carbon nanotubes (CNTs) have many interesting mechanical properties. Therefore, it is expected that an excellent characteristic can be demonstrated by small addition of CNTs in various composite materials. In this study, nylon-6 (N6) was used as the base material and CNTs were mixed to it as a reinforcing agent. Three kinds of CNT were used as filler. Single-wall nanotubes (SWNTs) produced by arc plasma jet (APJ) method, SWNTs produced by ferrum-hydrogen arc (FHA) method, and multiwalled nanotubes (MWNTs) produced by chemical vapor deposition (CVD). Mechanical properties of the composites were measured by tension test, bending test and impact test. In general, when tensile or bending strength goes high, the value of impact energy falls. However, in the case of APJ-SWNT mixing in N6, the impact energy also increases together with the tensile and bending strengths. This study, thus, suggests that APJ-SWNT possesses a characteristic due to which the composite material is strengthened without losing its toughness.
Improvement in Field Electron Emission Performance of Natural-Precursor-Grown Carbon Nanofibers by Thermal Annealing in Argon Atmosphere
Authors: Ghosh Pradip , Zamri Mohd , Ghosh Debasish , Soga Tetsuo , Jimbo Takashi , Hashimoto Shinobu , Ohashi Shuho , Tanemura Masaki
Published: January 2011

Carbon nanofibers (CNFs) were grown on a graphite substrate by the spray pyrolysis of a botanical hydrocarbon, turpentine oil, using ferrocene as the catalyst and sulfur as the promoter. The as-grown CNFs were annealed at 450 °C for 30 min in an air, and then at 1800 °C in an argon atmosphere for 2 h. The annealed CNFs have better degree of crystallinity and reduced number of defects compared with the as-grown CNFs confirmed by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy, and thermogravimetric analysis. The as-grown and annealed CNFs were found to be effective electron emitters with turn-on fields of 3.2 and 2.1 V/µm, respectively. The improvement in field emission (FE) performance can be explained in terms of the higher degree of graphitization of the CNFs after thermal annealing. This improved FE performance of the natural precursor grown CNFs was comparable to the FE performance level attainable for the conventional carbon nanomaterials grown using petroleum products. Thus, it was considered that the use of petroleum products could be avoidable for CNF growth and that CNFs grown using ecofriendly materials are very promising for the application in future field emission displays (FEDs).
Mass Density as Basis Parameter on Mechanical Properties under Diamond-Like Carbon Prepared in Wide Range of Conditions Using Variety of Methods
Authors: Kaneko Satoru , Horiuchi Takahiro , Yoshida Kentaro , Tanaka Satomi , Kato Chihiro , Kano Makoto , Kumagai Masao , Tanoue Hideto , Kamiya Masao , Takikawa Hirofumi
Published: January 2011

Diamond-like carbon (DLC) films were prepared on steel substrates by eleven suppliers using different types of equipment utilized in each company's own coating formation process. The deposition methods include sputtering, electron cyclotron resonance chemical vapor deposition (ECR-CVD), plasma enhanced chemical vapor deposition (PECVD), arc ion plating (Arc), filtered arc deposition (FAD), and plasma-based ion implantation (PBII). Some correlation of mechanical properties seems to be valid in a narrow range of parameters produced by a particular deposition method. In order to investigate general correlations in a wide range of parameters, various DLC films were prepared by different suppliers on the same substrate, and were evaluated in exactly the same manner. Independent of deposition methods, there existed correlations of the hardness, elastic modulus and Raman shift with a wide range of mass density.
Preparation of Arc Black and Carbon Nano Balloon by Arc Discharge and Their Application to a Fuel Cell
Authors: Ikeda Takashi , Kaida Shota , Satou Tosiyuki , Suda Yoshiyuki , Takikawa Hirofumi , Tanoue Hideto , Oke Shinichiro , Ue Hitoshi , Okawa Takashi , Aoyagi Nobuhiro , Shimizu Kazuki
Published: January 2011

Arc black (AcB) was prepared in N2 gas using the twin-torch arc discharge apparatus, and a hollow capsule with graphite layers named a carbon nano balloon (CNB) was obtained by heat treatment of the AcB in Ar gas at 2400 °C. Transmission electron microscopy, Raman spectroscopy, thermogravimetric analysis, and compressive resistivity measurement confirmed that the CNB was well graphitized. In the direct methanol fuel cell (DMFC) application of these carbon nanomaterials, catalyst metal nanoparticles were supported on the AcB, and a membrane-electrode assembly (MEA) was formed from the catalyst-supported AcB and the CNB by hotpressing them on an electrolyte film. The MEA containing the CNB resulted in a higher DMFC performance than that without the CNB, indicating that the CNB with lower compressive resistivity than the AcB works as a material for the improvement of electric conductivity in an MEA.
Magneto-Optical Properties of Armchair Nanographene Ribbons under Spatially Modulated Electric Field
Authors: Chen Szu-Chao , Chiu Chih-Wei , Lin Ming-Fa
Published: January 2011

The spatially modulated electric field is used to tune the magneto-optical properties of an armchair nanographene ribbon. The band structure and optical absorption spectrum under the perpendicular magnetic field and the spatially modulated electric field are calculated through the tight-binding model and the gradient approximation. The quasi-Landau levels are greatly affected by the periodic potential such as the modulation of the energy dispersion, the creation of the extra band-edge states, and the alteration of the Landau wave functions. The modulation ability of the electric field grows with the increase of the electric field strength or the decrease of the periodic length. The change of the electronic properties is directly reflected in the optical absorption spectra. The number, the shape, the intensity, and the position of the absorption peaks are altered. The selection rule of the optical excitations between the quasi-Landau levels is destroyed under the influence of the modulated electric field. The predicted results can be directly verified by optical measurements.
Effects of Environmental Humidity and Temperature on Sterilization Efficiency of Dielectric Barrier Discharge Plasmas in Atmospheric Pressure Air
Authors: Kikuchi Yusuke , Miyamae Masanori , Nagata Masayoshi , Fukumoto Naoyuki
Published: January 2011

The inactivation ofBacillus atrophaeusspores by a dielectric barrier discharge (DBD) plasma in atmospheric humid air was investigated in order to develop a low-temperature, low-cost, and high-speed plasma sterilization technique. The biological indicators covered with a Tyvek sheet were set just outside the DBD plasma region, where air temperature and humidity as a discharge gas were precisely controlled by an environmental test chamber. The results show that the inactivation ofB. atrophaeusspores was found to be dependent strongly on humidity, and was completed within 15 min at a relative humidity of 90% and a temperature of 30 °C. The treatment time for sterilization is shorter than those of conventional sterilization methods using ethylene oxide gas and dry heat treatment. The inactivation rates depend on not only relative humidity but also temperature, so that water content in air could determine the generation of reactive species such as hydroxyl radicals that are effective for the inactivation ofB. atrophaeusspores.
Nitrile Hydration by Co(III) Complex with Oxygenated S Atoms Inserted into Mesoporous Silica
Authors: Ozawa Tomohiro , Shibayama Tomonori , Yano Takuma , Funahashi Yasuhiro , Masuda Hideki
Published: January 2011

Three octahedral Co(III) complexes with N2S2 coordination donors at the equatorial plane and two molecules of tert-butylisocyanide at axial sites were prepared to investigate the hydration of acetonitrile, propionitrile, benzonitrile, and acrylonitrile. The complexes are different in the oxidation state of the coordinated sulfurs; two thiolates (–S; 1), two sulfenates (–SO; 2), and two sulfinates (–SO2; 3). The hydration of the nitriles to their corresponding amides was observed only in the reaction system including 2, indicating that the sulfenate group is essential for the generation of the hydration activity in the series. In order to avoid the deactivation of catalyst 2 by decomposition, it was inserted into the mesopores in the folded sheet mesoporous material (FSM). Indeed, the thermal stability of 2 increased and the reaction turnover number somewhat improved, but the catalyst eluted out from the pores because the electrostatic interaction between silanol groups and polar groups of 2 weakened in an aqueous solution.
Finite Element Analysis of Severe Plastic Deformation of Difficult-to-Work Material by Equal-Channel Angular Pressing at Ambient Temperature
Authors: Jamian Saifulnizan , Sato Hisashi , Miura-Fujiwara Eri , Watanabe Yoshimi
Published: January 2011

An alternative technique of the equal-channel angular pressing (ECAP) process for difficult-to-work materials at ambient temperature is proposed by embedding a difficult-to-work material into an easy-to-work material. The easy-to-work material as a host material assists the deformation of the difficult-to-work material. The ECAP process is simulated by the finite element method (FEM). For this study, Ti as the difficult-to-work material is embedded into an Al-based functionally graded material (FGM) matrix. FEM is conducted with Ti embedded into a different host material type as well as a different die channel geometry. The strain distribution of the specimen after a single ECAP pass is analyzed. From the obtained results, it is found that the strain distribution in Ti is strongly influenced by the host material and the shape of the die channel.
Surface Plasma Treatment of Polyimide Film for Cu Metallization
Authors: Cho Sang-Jin , Choi Jin-Woo , Bae In-Seob , Nguyen Trieu , Boo Jin-Hyo
Published: January 2011

Surface modification of polyimide films by oxygen/argon atmospheric pressure plasma (APP) was studied for copper metallization under several conditions, including plasma treatment time, gas ratio, and power of radio frequency (RF; 13.56 MHz) plasma. The effects of APP treatments on the surface properties of polyimide (PI) films were investigated in terms of Fourier-transform infrared (FT-IR) spectroscopy, atomic force microscopy (AFM), and contact angle measurements. The results showed that the root-mean-squared (RMS) roughness of untreated PI films was 1.48 nm, increasing to 2.08, 2.17, and 2.57 nm after plasma treatment at 200, 400, and 600 W, respectively. At the same time, the contact angle of untreated PI film was 73.0° and reduced to 25.9, 20.3, and 17.3° after plasma treatment at 200, 400, and 600 W, respectively. The lowest contact angle and the maximum RMS roughness were 13° and 8.50 nm, respectively. Those values were achieved by oxygen/argon APP at an RF plasma power of 600 W and with 50 repetitions. Also, X-ray diffraction (XRD) was used to examine the Cu surface structure in the Cu/PI system to indicate the quality of Cu foil. The highest I(111)/I(200) ratio was 1.89 at an RF power of 600 W by oxygen/argon APP treatment.
Properties of Indium Tin Oxide Thin Films Deposited on Glass and Clay Substrates by Ion-Beam Sputter Deposition Method
Authors: Venkatachalam Shanmugam , Nanjo Hiroshi , Hassan Fathy M. B. , Kawasaki Kazunori , Wakui Yoshito , Hayashi Hiromichi , Ebina Takeo
Published: January 2011

Indium tin oxide (ITO) thin films were prepared on glass and clay substrates by ion beam sputter deposition method. The surface morphologies of ITO films showed that the ITO film on glass substrate is smooth; in contrast, the ITO film on clay substrate is rough. The X-ray diffraction patterns showed two different orientations, i.e., (400) and (222) on different substrates, i.e., glass and clay, respectively. The optical spectra showed that the optical transmittance of ITO/glass is greater than that of ITO/clay substrate; it is due to the difference in substrate surface roughness between ITO/glass and ITO/clay. The sheet resistances of ITO/glass and ITO/clay were calculated as 32 and 41 Ω/□, respectively. The increase in film thickness enhances the growth of the films along (222) direction. It is attributed that the stress relaxation is one of the reasons for the change of preferred orientation from (444) to (222) plane. In this paper we discuss the possible factors which determine the crystal growth and orientation of ITO thin films.
Synthesis and Reactivity of µ-η2:η2-Disulfido Dicopper(II) Complex with N,N ',N''-Trimethyl-1,3,5-cis,cis-triaminocyclohexane
Authors: Matsumoto Jun , Kajita Yuji , Masuda Hideki
Published: January 2011

A new µ-η2:η2-disulfido dicopper(II) complex (1) was prepared from the reaction of copper(I) complex with N,N ',N''-trimethyl-1,3,5-cis,cis-triaminocyclohexane (R3TACH; R=Me) and elemental sulfur at room temperature in CH2Cl2. The UV–visible spectrum of 1 gave four peaks at 353 (ε= 18300), 397 (ε= 10000), 462 (ε= 6000), and 666 (ε= 760 M-1·cm-1) nm in CH2Cl2, whose spectral pattern is similar to those of copper(II) complexes with other R3TACH derivatives [R=Et (ethyl), iBu (isobutyl), and Bn (benzyl)] reported previously. The compound 1 was quite stable in the solid state, while in CH2Cl2, it was decomposed at 25 °C; the decomposition rate and half-lifetime were estimated to be 1.15×10-2 min-1 and 60 min, respectively. The stability was similar to that of the copper complex of Et3TACH, although it was lower than those of the disulfido dicopper(II) complexes with other TACH ligands. The compound 1 showed an oxidation reactivity toward triphenylphosphine to give triphenylphosphine sulfide with 68% yield. The relationship between the structures and oxidation reactivities of the µ-η2:η2-disulfido dicopper(II) complexes were discussed in relation to the distortion around the Cu2S2 core and the steric hindrance between the substituent groups.
Molecular Design of High-Performance Fullerene Materials: A Theoretical Study on Hole-Transport Property of Fullerene Hydride C70H2
Authors: Tokunaga Ken , Ohmori Shigekazu , Kawabata Hiroshi
Published: January 2011

As a convenient method for modifying the hole-transport property of fullerene materials, hydrogenation of fullerene C70 is considered theoretically. Firstly, for the analysis of the carrier-transfer mechanism between C70H2 molecules, the geometrical difference between C70H2 and C70H2
+, the natural population analysis (NPA) charge, and the electron spin resonance (ESR) parameters (spin density) of C70H2
+ are calculated by density functional theory [B3LYP/6-311G(d,p)]. Secondly, the reorganization energies (λ) and electronic coupling elements (H
AB) of eight isomers of C70H2 with a small heat of formation are calculated and compared with that of C70. It is shown that four isomers of C70H2 have a smaller λ than C70 (120 meV) and that the magnitude of λ of C70H2 isomers is closely related to the geometrical difference between C70H2 and C70H2
+. Four isomers of C70H2 have larger H
AB than C70 (24 meV). Isomers with delocalized highest occupied molecular orbital (HOMO) tend to have small λ and large H
AB. At 300 K, the best isomer has hole-transfer rate constant (k
ht) which is over six times as large as that of C70.
Evaluation of Alignment of Nematic Liquid Crystal Thin Film by Spectroscopic Ellipsometry
Authors: Ito Keisuke , Goda Kazuya , Kimura Munehiro , Akahane Tadashi
Published: January 2011

Generally, macroscopic molecular orientation state in liquid crystal layer can be described by Ossen and Frank's continuum theory. However, the validity of applying the continuum theory to nematic liquid crystal thin film (NLCF) has not been confirmed yet. In this study, we experimentally examined NLCF by employing spectroscopic ellipsometer. As a result, theoretical and experimental result represent a good agreement when NLCF thickness is from 60 to 250 nm. Furthermore, the influence of surface roughness on alignment film surface and glass substrate was also examined.
Crystal Growth of Anthracene by Dip Coating and Application for Organic Electroluminescence Devices
Authors: Noda Atushi , Iwata Nobuyuki , Yamamoto Hiroshi
Published: January 2011

The purpose of this study is to apply anthracene needle-like crystals (NLCs) to an organic electroluminescence (EL) device. The NLCs growth depended on dipping speed. The slower the dipping speed, the wider NLCs grew. It was confirmed that the NLCs were anthracene by the Raman spectrum and X-ray diffraction (XRD) pattern. The lattice spacing determined from XRD corresponded to the step height obtained from surface images taken using atomic force microscopy. The anthracene NLCs bridged between Au and Al electrodes with a drawing speed of 2 µm/s.
Enhancement of Electron Injection in Organic Light-Emitting Diodes with Photosensitive Charge Generation Layer
Authors: Okawa Yuta , Naka Shigeki , Okada Hiroyuki
Published: January 2011

We describe the enhancement of electron injection by external light irradiation in organic light-emitting diodes (OLEDs) with a charge generation layer (CGL). Under He–Ne laser irradiation, photon-induced charge generation under electric field occurred in the CGL. Electrons and holes were generated in the CGL and the electrons were directly injected into adjacent electron transport layers. As a result, the enhancement of current density under light irradiation was observed. A thousand fold enhancement of current density was obtained for light irradiation under forward biased condition. Current density was determined by the intensity of light irradiation and was saturated under the higher voltage regions. Up-converted light emission was also observed under the light irradiation.
Effect of Dielectric Barrier Discharge Air Plasma Treatment on TiO2 Thin Film Surfaces
Authors: Kawakami Retsuo , Niibe Masahito , Fukudome Toshiaki , Takeichi Atsushi , Inaoka Takeshi , Tominaga Kikuo
Published: January 2011

Surface treatment effect on TiO2 thin films with the anatase phase by dielectric barrier discharge (DBD) air plasmas has been investigated for a variety of gas pressures and treatment times. At a low gas pressure (100 hPa) at which a glow-like discharge plasma occurs, hydrophilicities of TiO2 thin films treated at 5 and 30 min are enhanced compared with that of the as-grown thin film. For the 5 min treatment, this trend is more pronounced probably due to oxygen absorbed on the surface from the air plasma. For the 30 min treatment, the enhanced hydrophilicity is probably due to oxygen vacancy created on the surface by a high fluence of the plasma. When the gas pressure increases to 400 hPa at which a streamer discharge plasma occurs, the hydrophilicity is more weakened than that of the as-grown thin film: the plasma-induced damage occurs regardless of the treatment time. This result would probably result from the higher discharge current and UV light intensity caused by the higher breakdown voltage based on Paschen's law.
Synthesis and Characterization of Thin Films of a Half-Metallic Oxide, Sr2FeMoO6, by Combinatorial Techniques
Authors: Kadota Shogo , Matsumoto Yuji , Sasagawa Takao
Published: January 2011

The ordered double perovskite oxide, Sr2FeMoO6, has a half-metallic property and is considered as one of the best materials for creating spin-polarized current for next-generation spintronics devices. In order to optimize the fabrication conditions for (001)-oriented single-crystalline Sr2FeMoO6 thin films, a combinatorial pulsed laser deposition (PLD) technique, together with combinatorial (high-throughput) characterization, were carried out. It is found that atmospheric pressure during the deposition affects the formation of secondary phases, thus careful control of this parameter is necessary. On the other hand, substrate temperature affects the electric transport property and surface flatness; better results are obtained at a higher substrate temperature.
Synthesis and Characterization of Cu- and Co-Doped Bi4V2O11 for Intermediate-Temperature Solid Oxide Fuel Cell Electrolytes by Carbonate Coprecipitation
Authors: Lee Jin Goo , Yoon Hyon Hee
Published: January 2011

Bi2Me
x
V1-x
O5.5-3x/2 (Me = Cu; 0≤x≤0.2) powders were prepared by the ammonium carbonate coprecipitation method. The starting salts were bismuth nitrate, copper nitrate, cobalt nitrate, and vanadium sulphate. The thermal decomposition of Bi2Me
x
V1-x
O5.5-3x/2 precursors was completed at about 500 °C. The crystallite structure, surface morphology, and ionic conductivity of the prepared powders and pellets were examined using X-ray diffractometry, field emission scanning electron microscopy, and an impedance analyzer, respectively. The average particle sizes of the Bi2Cu0.1V0.9O5.35 and Bi2Co0.1V0.9O5.35 powders were 10–50 nm. The tetragonal structure (γ-phase) appeared at sintering temperatures higher than 700 °C and the peak intensity increased at higher sintering temperatures. The ionic conductivities of the Bi2Cu0.1V0.9O5.35 and Bi2Co0.1V0.9O5.35 pellets sintered at 800 °C showed the highest values of 6.8×10-2 S cm-1 at 700 °C and 9.1×10-2 S cm-1 at 700 °C, respectively. The optimum concentration of the Cu and Co dopants in Bi2Me
x
V1-x
O5.5-3x/2 was determined to be 0.1. The results of this study demonstrated that the ammonium carbonate coprecipitation process could be used as an economical method for the preparation of Bi2Me
x
V1-x
O5.5-3x/2 electrolytes for intermediate-temperature solid oxide fuel cells.
Electronic Structures and Magnetism of Al/Fe(001) Thin-Film Systems: First-Principles Calculations
Authors: Choi Heechae , Yoon Geunsup , Chung Yong-Chae
Published: January 2011

Using the first-principles calculations, the changes in the magnetic moment and the electronic structure of Al/Fe(001) thin film systems were investigated with varying Al thickness and the interface intermixing amount. When Al overlayer was 1 ML thick, the interface intermixing was not favorable, which is consistent with experimental observations. However, when the Al layers were 2 ML and 3 ML, the interface intermixing was exothermic and the Fe atoms intermixed in the Al layer lattices had reduced magnetic moments. As the intermixing amount was increased, the magnetic moments were decreased. The origins of enhancement and reduction in the Fe magnetic moments could be found from the projected 3d-electron density of states analysis.