bluuebunny/crossref_metadata_2025 huggingface dataset:
Simple and Low-Cost Fabrication of Flexible Capacitive Tactile Sensors
Authors: Kasahara Takashi , Mizushima Masanori , Shinohara Hidetoshi , Obata Tsutomu , Futakuchi Tomoaki , Shoji Shuichi , Mizuno Jun
Published: January 2011

We fabricated novel flexible capacitive tactile sensors that can detect both the direction and distribution of an applied force. The sensor consists of a conductive silicone rubber as a movable electrode and fixed electrodes formed on a poly(ethylene terephthalate) (PET) film with silver paste. The dimensions of sensor head are 10.4 ×10.4 ×0.8 mm3. We developed the tactile sensor using screen-printing techniques and atmospheric-pressure plasma pretreatments. We experimentally evaluated the tactile responses to the applied force. The sensor detected the input force-distribution with a force ranging up to 10 N. The flexible thin PET film substrate enables fitting to the tight space and curved surface, and this capacitive tactile sensor is applicable for low-cost controllers of cellular phones and personal computers.
Effect of Rinse Process on Removal of Crown Type Defects during Photoresist Development
Authors: Kim Sang-Yong , Park Jin-Goo
Published: January 2011

Defect reduction is one of the most important factors to improve the process stability and yield in the wafer fabrication process. Reduction of defects after development process is a critical issue in photolithography. A special category of post development defects is the “crown defect” which is formed on large exposed or unexposed areas. In this work, the process was developed to remove crown defects from gate and hole patterns by optimizing the deionized water (DIW) rinse time and applying the sling effect. After testing at various conditions, it was found that 80 and 40 s DIW rinse combined with sling effect could completely remove the crown defects from gate and hole patterns, respectively, which would improve the product quality and yield.
Morphology Effects on Space Charge Characteristics of Low Density Polyethylene
Authors: Zahn Zhou , Wang Wang , Ninghua Ninghua , Sun Sun , Qinghua Qinghua , Liang Liang , Xidong Xidong , Guan Guan , Zhichen Zhichen
Published: January 2011

Low density polyethylene (LDPE) film samples with different morphology were prepared by three kinds of annealing methods which were different in cooling rates in this study. A pulsed electro-acoustic (PEA) space charge measurement system was improved to solve the surface discharge problems for small samples applied with a high voltage. Negative direct current (DC) fields from 50 to above 220 kV/mm were applied to the samples. The influences of morphologies on space charge and space charge packet characteristics were measured by the improved high voltage withstand (HVW) PEA system. Mobility and trap depth of released charges were calculated by space charge decay. It was found that there is a different probability of space charge packet initiation under applied field from -60 to -100 kV/mm. Average velocity and mobility of the space charge packets were calculated by space charge packet dynamics. It was found that the lower cooling rate samples have higher crystallinity, more homo-charge accumulation, lower mobility and deeper trap depth. The mechanism of morphological effects on space charge phenomena have been presumed to give a plausible explanation for their inherent relationships. The morphology in the metal–dielectric interface and in the bulk is convincingly suggested to be responsible for the injection and propagation processes of space charge. A model of positive space charge initiation in LDPE samples was also suggested and analyzed. The mechanism of morphological effects and the charge injection model are well fit with the injection and propagation processes of space charge. The different effects of morphology in the metal–dielectric interface and in the bulk of polymers are stressed.
Improvement of Filtration Performance Using Self-Tuning of Flow Resistance
Authors: Yoon Dong Hyun , Bahk Yeon Kyoung , Kwon Bong Hyun , Kim Seong Sik , Kim Yong-Deok , Arakawa Takahiro , Go Jeung Sang , Shoji Shuichi
Published: January 2011

In this paper, we present the filtration of a liquid sample from polystyrene microparticles analogous to the separation of a biological liquid from mixed particles such as whole blood. The proposed self-tuning of flow resistance can prevent the excessive clogging of microparticles in the microfilter by allowing the automatic change of the flow direction when the microfilter is clogged. Numerically, at about 80% of the clogging of microparticles in the pillar channel, the sample flow is regulated suddenly to the bypass channel. Experimentally, the clogging behavior at the five successive pillar channels and the self-tuning of flow are compared by measuring the clogging area and volume with time. Also, the microfilter array connected in a series can provide an increase in the sample volume proportionally without excessive pressure build-up. This implies the potential to reduce cell fracture in the filtration of biological cells.
Graphene/Graphite-Coated SiC Nanowires Grown by Metal–Organic Chemical Vapor Deposition in One Step
Authors: Kohno Hideo , Yagi Kazuki , Niioka Hirohiko
Published: January 2011

Graphene/graphite-coated SiC nanowires are fabricated from diethylsilane or divinyldimethylsilane by Fe-assisted metal–organic chemical vapor deposition. When diethylsilane is used, a few layers of graphene are formed, while 30–40-nm-thick graphite is formed from divinyldimethylsilane.
Plasma Diagnostics for NH3 Plasmas Using a Quartz Sensor at Various Pressures
Authors: Suzuki Atsushi , Nonaka Hidehiko
Published: January 2011

A novel plasma diagnostic method using a quartz sensor (Q-sensor) was applied to the analysis of NH3 plasmas at various pressures of 19.6–131.0 Pa. The change in the gas composition of the NH3 plasmas was derived from the change in the Q-sensor output through pressure normalization because the pressure-normalized Q-sensor output depends on the molecular weight and viscosity of the measured gas. The change in the gas composition of the NH3 plasmas agrees with the results obtained from the gas analysis using a quadrupole mass spectrometer (QMS): the plasma gas composition includes high-density H2 and low-density N2. The dissociation ratio of NH3 was compared with measurements obtained using the Q-sensor and QMS, which indicates that Q-sensor measurement is useful as a method of plasma diagnostics for obtaining the gas composition of NH3 plasmas at 19.6–131.0 Pa.
Molecular Dynamics Simulation of Chemical Vapor Deposition of Amorphous Carbon: Dependence on H/C Ratio of Source Gas
Authors: Ito Atsushi M. , Takayama Arimichi , Saito Seiki , Ohno Noriyasu , Kajita Shin , Nakamura Hiroaki
Published: January 2011

By molecular dynamics simulation, the chemical vapor deposition of amorphous carbon onto graphite and diamond surfaces was studied. In particular, we investigated the effect of source H/C ratio, which is the ratio of the number of hydrogen atoms to the number of carbon atoms in a source gas, on the deposition process. In the present simulation, the following two source gas conditions were tested: one was that the source gas was injected as isolated carbon and hydrogen atoms, and the other was that the source gas was injected as hydrocarbon molecules. Under the former condition, we found that as the source H/C ratio increases, the deposition rate of carbon atoms decreases exponentially. This exponential decrease in the deposition rate with increasing source H/C ratio agrees with experimental data. However, under the latter molecular source condition, the deposition rate did not decrease exponentially because of a chemical reaction peculiar to the type of hydrocarbon in the source gas.
Growth and Electrical Properties of 3C-SiC/Nanocrystalline Diamond Layered Films
Authors: Koga Akira , Teii Kungen , Goto Masaki , Yamada Kazuhiro , Kato Yoshimine
Published: January 2011

Cubic silicon carbide (3C-SiC)/nitrogen-incorporated nanocrystalline diamond layered films are prepared on p-type Si(100) substrates by carbonization and chemical vapor deposition in moderate-pressure microwave plasmas. X-ray diffraction, cross-sectional transmission electron microscopy, and energy dispersive X-ray spectroscopy reveal that epitaxial 3C-SiC thin layers about 10 nm thick with very high phase-purity are grown at the interface of Si and nanocrystalline diamond. The infrared absorption coefficient for the 3C-SiC layer is estimated to be around 420000 cm-1. The p-Si/3C-SiC/n-nanocrystalline diamond junction in a diode configuration shows rectification in the current–voltage measurement. Structural defects and surface roughening of the SiC layers are highly responsible for increasing the reverse leakage current and thus lowering the diode performance.
Synthesis of Wurtzite-Type ZnMgS by the Pulsed Plasma in Liquid
Authors: Omurzak Emil , Shimokawa Wataru , Taniguchi Kengo , Chen Liliang , Okamoto Makoto , Iwasaki Hideharu , Yamasaki Michiaki , Kawamura Yoshihito , Sulaimankulova Saadat , Mashimo Tsutomu
Published: January 2011

Wurtzite-type ZnMgS (w-ZnMgS) nanoparticles were synthesized using the pulsed plasma in liquid method. By the pulsed plasma generated between two electrodes made of ZnMg alloy in liquid sulfur, we produced w-ZnMgS nanocrystals mixed with Zn2Mg and MgS. Higher purity w-ZnMgS sample was achieved by annealing at 773 K. The synthesized ZnMgS nanoparticles were of spherical shape and contained of many crystal defects (stacking faults). Ultraviolet–visible (UV–vis) absorption spectroscopy analysis of the synthesized w-ZnMgS showed absorption edge broadening and appearance of a small absorption band at around 400 nm even without doping.
Residual Strain Evaluation by Cross-Sectional Micro-Reflectance Spectroscopy of Freestanding GaN Grown by Hydride Vapor Phase Epitaxy
Authors: Geng Huiyuan , Yamaguchi A Atsushi , Sunakawa Haruo , Sumi Norihiko , Yamamoto Kazutomi , Usui Akira
Published: January 2011

Distributions of residual stresses in the cross-section of as-grown c-plane freestanding GaN substrates grown by hydride vapor phase epitaxy (HVPE) were precisely measured by low temperature cross-sectional micro-reflectance spectroscopy. Based on the measured residual stresses in the cross-section area, the depth profile of in-plane isotropic biaxial intrinsic strain in the as-grown GaN wafer was also established according to the elastic theory for thin films. It is found that the intrinsic strain increases nearly linearly with the increasing distance to the Ga-face of the freestanding GaN substrate, and is greatly reduced by the introduction of three-dimensional (3D) GaN islands growth in the starting stage of the HVPE growth. According to the relationship between the intrinsic strain and threading dislocation density, the current research suggests that the bending of freestanding GaN is caused by the reduction of threading dislocation density along the film growth direction.
Drastic Reduction of Dislocation Density in Semipolar (1122) GaN Stripe Crystal on Si Substrate by Dual Selective Metal–Organic Vapor Phase Epitaxy
Authors: Murase Tasuku , Tanikawa Tomoyuki , Honda Yoshio , Yamaguchi Masahito , Amano Hiroshi , Sawaki Nobuhiko
Published: January 2011

A drastic reduction of the dislocation density in a semipolar (1122) GaN stripe on a patterned Si substrate was achieved by the two-step selective growth of a GaN stripe. After depositing a SiO2 mask on the (1122) and (0001) faces of a GaN stripe grown on a (113) Si substrate, GaN was regrown only on the (1122) face. The dislocation density estimated from the dark-spot density in a cathodoluminescence (CL) image greatly decreased from 4.0×108 to 1.0×105/cm2 in the regrowth region. A transmission electron microscopy (TEM) image also verified that there were no dislocations at the regrowth interfaces.
Study of Electrical Response in Pt/GaN Schottky Barrier Diode to CO Gas for High Temperature Gas Sensor
Authors: Okada Hiroshi , Naruse Atsuki , Furukawa Yuzo , Wakahara Akihiro
Published: January 2011

The response characteristics of a Pt/GaN Schottky barrier diode (SBD) to carbon monoxide (CO) gas have been investigated. The characteristics of a GaN-based SBD with a 30-nm-thick Pt catalyst were measured at 300 °C for various CO gas concentrations. The amplitude of the single exponential response of the current under reverse bias changed reasonably with CO gas concentration. We have proposed a parallel diode model to fit the observed response. Using this model, the absorption/desorption of gas molecules and change of the Schottky barrier height are estimated.
Behaviors of Absolute Densities of N, H, and NH3 at Remote Region of High-Density Radical Source Employing N2–H2 Mixture Plasmas
Authors: Chen Shang , Kondo Hiroki , Ishikawa Kenji , Takeda Keigo , Sekine Makoto , Kano Hiroyuki , Den Shoji , Hori Masaru
Published: January 2011

For an innovation of molecular-beam-epitaxial (MBE) growth of gallium nitride (GaN), the measurements of absolute densities of N, H, and NH3 at the remote region of the radical source excited by plasmas have become absolutely imperative. By vacuum ultraviolet absorption spectroscopy (VUVAS) at a relatively low pressure of about 1 Pa, we obtained a N atom density of 9×1012 cm-3 for a pure nitrogen gas used, a H atom density of 7×1012 cm-3 for a gas composition of 80% hydrogen mixed with nitrogen gas were measured. The maximum density 2×1013 cm-3 of NH3 was measured by quadruple mass spectrometry (QMS) at H2/(N2+H2)=60%. Moreover, we found that N atom density was considerably affected by processing history, where the characteristic instability was observed during the pure nitrogen plasma discharge sequentially after the hydrogen-containing plasma discharge. These results indicate imply the importance of establishing radical-based processes to control precisely the absolute densities of N, H, and NH3 at the remote region of the radical source.
Plasma Deposition of Diamond-Like Carbon
Authors: Robertson John
Published: January 2011

We describe some of the recent advances in the deposition and applications of amorphous diamond-like carbons, including an understanding of stress reduction by deposition. The subplantation model is described. Applications to hard, wear-resistant film are summarised.
Magnetoelectronic and Optical Properties of Monolayer and AB-Stacked Bilayer Graphenes
Authors: Ho Yen-Hung , Chiu Yu-Huang , Wang Jei , Lin De-Hone , Lin Ming-Fa
Published: January 2011

The low-frequency magneto-absorption spectra of monolayer and bilayer graphene are evaluated within the gradient approximation. On the basis of Peierls tight-binding model, we can draw the wave function distribution over its sublattices and bring them into the calculation of optical spectra. The optical selection rules and the absorption rate can be accurately determined. The interlayer interactions in bilayers effectively alter the Landau level structures and thus the absorption spectra, such as the field dependence of absorption lines and the appearance of double-peaked absorptions.
White Light Emission from Mesoporous Carbon–Silica Nanocomposites
Authors: Ishii Yosuke , Matsumura Akihiro , Ishikawa Yukari , Kawasaki Shinji
Published: January 2011

Visible photoluminescence properties of mesoporous nanocomposites of carbon and silicon dioxides prepared using the triconstituent co-assembly method is reported. Intense white-light emission from the nanocomposites was observed at room temperature, under 370-nm light irradiation after proper carbon desorption by air-oxidation. We observed that the shapes of the luminescence spectra, especially in the green-yellow region, were highly dependent on the oxidation condition of the samples.
Electric Double Layer Capacitance of Graphene-Like Materials Derived from Single-Walled Carbon Nanotubes
Authors: Inoue Tsuyoshi , Mori Syunsuke , Kawasaki Shinji
Published: January 2011

We tried to unwrap single-walled carbon nanotubes (SWCNTs) by reducing the oxidized SWCNTs. A transmission electron microscope (TEM) observation revealed that the unwrapped SWCNTs were transformed from a pristine nanotube structure to a sheet-like (graphene-like) structure. Electrochemical measurements demonstrated that the electric double layer capacitance (EDLC) of SWCNTs increases significantly due to the unwrapping treatment. For example, the EDLC (199 F/g) of the unwrapped SWCNTs in 1 M H2SO4 electrolyte at a current rate of 50 mA/g is about four times greater than that (51.9 F/g) of pristine SWCNTs.
Hydrogenated Amorphous Carbon Films Prepared by Filtered Vacuum Arc Method with Various C2H2Pressures
Authors: Lee Seunghun , Yoon Sung-Hwan , Kim Jong-Kuk , Kim Do-Geun
Published: January 2011

Hydrogenated amorphous carbon films (a-C:H) were deposited on silicon (100) substrates using a filtered vacuum arc (FVA) method. A graphite cathode and acetylene (C2H2) at various flow rates were used to synthesize the carbon films. The deposition rate of the carbon films without C2H2addition was 5 nm/min, whereas the deposition rate increased from 23 to 82 nm/min with increasing C2H2flow rate from 2.5 to 20 sccm. The supply of C2H2gas induces an increase in CH radical density near the substrate, resulting in a high deposition rate. The plasma diagnostics using optical emission spectroscopy showed that the emission peak intensity of the CH radicals (A3Πg–X3Πu, 431.26 nm) increased with increasing C2H2flow rate. Raman spectroscopy revealed a change in the deposited films from nano-crystalline graphite to a-C:H as the C2H2flow rate was increased.
Optimum Decomposition Conditions for Glass Fiber Reinforced Plastic Recycling by Superheated Steam
Authors: Shi Jian , Bao Limin
Published: January 2011

The objective of the present study is to investigate the effect of pyrolysis time and temperature on the mechanical properties of recycled fiber, based on tensile strength measurements, determining the optimum decomposition conditions for glass fiber-reinforced plastic (GFRP) by superheated steam. In this research, GFRP was efficiently depolymerized and reinforced fiber was separated from resin by superheated steam. Tensile strength of fibrous recyclates was measured and compared to that of virgin fiber. Although tensile strength of recycled fibers were lower than that of virgin fiber, under some conditions tensile strength of recycled fibers were close to that of virgin fiber. They were the optimum decomposition conditions for GFRP in our experiments. With pyrolysis, some char residue from the polymer remains on the fibers and degrees of char on the recycled fibers were closely examined by scanning electron microscopy.
Fabrication of Al/Al3Ti Functionally Graded Materials by Reaction Centrifugal Mixed-Powder Method
Authors: El-Hadad Shimaa , Sato Hisashi , Miura-Fujiwara Eri , Watanabe Yoshimi
Published: January 2011

Formation of compositional gradient in Al/Al3Ti Functionally graded materials (FGMs) fabricated by the centrifugal method (CM) depends mainly on the centrifugal force and the processing temperature. In this study, a novel centrifugal method, reaction centrifugal mixed-powder method (RCMPM), was proposed to fabricate Al/Al3Ti FGMs under fixed centrifugal force (G=80). The effects of RCMPM processing temperature on the formation of Al3Ti intermetallics, its morphology and its distribution in the fabricated Al/Al3Ti FGMs have been investigated. Fine granular Al3Ti were observed at relatively lower processing temperature while the known coarse platelet-like particles of Al3Ti could be achieved at higher casting temperatures. Moreover, Ti3Al intermetallics compound and unreacted Ti phases are also observed along with Al3Ti particles. In addition, distribution of Al3Ti intermetallics size and their volume fraction showed a significant change when the Al/Al3Ti FGMs processed at different temperatures relative to the liquidus temperature of the master alloy.
Visible Light-Induced Catalytic Oxidation Using Zeolite Encapsulating Two Distinct Metal Complexes
Authors: Inomata Tomohiko , Nagai Yoshimasa , Ohata Nayumi , Funahashi Yasuhiro , Ozawa Tomohiro , Masuda Hideki
Published: January 2011

Y-type zeolite encapsulating two distinct metal complexes has been synthesized. This zeolite contains Ru(bpy)3 (bpy = 2,2'-bipyridine) and Mn(saloph) [saloph = N,N'-bis(salicylidene)-o-phenylenediamine] as photoinducing and oxidative catalytic sites, respectively. The zeolite showed the quenching of the emission, resulting in the effective electron/energy transfer from the RuII center to the MnII center in it. The oxidation reaction of dimethyl sulfide with the zeolite has been accelerated by photoirradiation. This phenomenon indicates that the electron/energy transfer from Ru(bpy)3 units affects the oxidation reaction on Mn(saloph) units.
A Novel Fabrication of p–n Diode Based on ZnO Nanowire/p-NiO Heterojunction
Authors: Chang Sheng-Po , Lu Chien-Yuan , Chang Shoou-Jinn , Chiou Yu-Zung , Hsu Cheng-Liang , Su Peng-Yu , Hsueh Ting-Jen
Published: January 2011

We report the deposition of NiO onto ZnO nanowires prepared on ZnO:Ga/glass templates. With the sputtered NiO, the nanowires became mushroom-like. Experimental results point out that sputtered NiO also formed nanoshells surrounding ZnO nanowires. The p-NiO/n-ZnO heterostructure exhibits rectifying behavior with a sharp turn on at ∼1 V. Furthermore, the current vs voltage characteristic is dominated by space-charge-limited current (SCLC) at high (1.1 V) forward bias.
Nanostructured Refractory Metal Oxide Films Produced by a Pulsed Microplasma Cluster Source as Active Layers in Microfabricated Gas Sensors
Authors: Barborini Emanuele , Ducati Caterina , Leccardi Matteo , Bertolini Giacomo , Repetto Pietro , Milani Paolo
Published: January 2011

Cluster-assembled nanostructured films of refractory metal oxides were produced by supersonic cluster beam deposition (SCBD) using a pulsed microplasma cluster source (PMCS). The growth of nanostructured films takes place at room temperature on substrates exposed to nanoparticles beam. Soft landing and limited diffusion are peculiar characteristics of the deposition process, causing the film to grow according to a highly porous structure. We produced nanostructured Mo, W, and Nb oxide films and we characterized their crystal structure and film morphology at the nanoscale together with their gas sensing performances. The effect of thermal treatments on grain growth and morphology modification was particularly addressed in view of the use of the nanostructured layers in gas sensing applications on microfabricated platforms.
Unique µ-Arene-dimolybdenum Complexes with a Mo–Mo Multiple Bond
Authors: Ogawa Takahiko , Kajita Yuji , Masuda Hideki
Published: January 2011

Novel dimolybdenum complexes bridged with aromatic rings (toluene, anisole), [Mo2(L')2(C7H8)] (1C7H8) and [Mo2(L')2(C7H8O)] (1C7H8O), have been synthesized and characterized by FT-IR and X-ray analysis. Their X-ray structures revealed that the two molybdenum ions were bridged with aromatic rings in unique cis-µ-η2(1,2):η2(4,5) or cis-µ-η2(2,3):η2(5,6) mode to form a Mo–Mo bond; 2.1876(5) and 2.1867(5) Å for 1C7H8 and 2.1886(11) and 2.1904(11) Å for 1C7H8O, respectively. The metal-bound carbon atoms of the bridged aromatic rings were deviated toward the metal atoms from the mean plane and the C–C bonds were shortened and elongated alternately. Judging from the valences of molybdenum ions and the short metal–metal bond distances, it is concluded that the two molybdenum ions are formed a quadruple bond, and also suggested that this bond distance is shortened by µ-arene molecules linked with the electron-releasing substituent group.
Organic Thin-Film Transistors with Tailored Liquid Sources of High-κ HfO2 Using Excimer Laser Irradiation
Authors: Nishizawa Ryota , Naka Shigeki , Okada Hiroyuki , Suzuki Kazuyuki , Kato Kazumi
Published: January 2011

The characteristics of organic thin-film transistors (OTFTs) with tailored liquid sources of HfO2 as a high-κ insulator were investigated using excimer laser irradiation. We have demonstrated that the OTFT characteristics were improved more by short wavelength light source irradiation than UV irradiation to cleave chemical bonds of organic residues in the alkoxy-derived HfO2 films. The field-effect mobilities and on–off ratios obtained for one shot of excimer laser irradiation were 0.18 cm2 V-1 s-1 and 750, respectively.
Bias-Induced Threshold Voltage Shifts in Organic Thin-Film Transistors by Soluble Fullerene Layers on Gate Dielectric
Authors: Mohamad Khairul Anuar , Uesugi Katsuhiro , Fukuda Hisashi
Published: January 2011

An investigation of threshold voltage shifts in organic thin-film transistors (TFTs) based on pentacene with an additional soluble fullerene derivatives of [6,6]-phenyl C61-butyric acid methyl ester (PCBM) on gate dielectric. With an additional soluble fullerene layer, the threshold voltage (V
th) is optimized from -3.9 to -1.1 V without affect the mode operation of the devices, while retaining the carrier mobility (0.02–0.03 cm2 V-1 s-1) and on/off current ratio (∼104). Furthermore, the existence of PCBM agglomerates as electron acceptor-like traps resulted in a shift of V
th in the positive and reversible directions depending on the magnitude of gate bias (V
bias) as well as duration of time bias (T
bias). The device operation changed into normally-on (depletion–accumulation) mode upon positive V
bias as the duration of T
bias was increased, which attributes to the formation of a conductive layer at the pentacene–fullerene interface. Moreover, the recovery of V
th was further enhanced by a high negative V
bias for a short duration. In addition, the mobility was minimally affected by both V
bias conditions.
Low-Voltage Organic Field-Effect Transistors Fabricated on Self-Assembled-Monolayer-Free SrTiO3 Insulator
Authors: Yan Hu , Hanagata Hiroki , Jo Toshihiko , Okuzaki Hidenori
Published: January 2011

Strontium titanate (SrTiO3) thin film with a dielectric constant of εr = 12.1 prepared on a heavily doped n-type silicon wafer by sputtering. Both pentacene and C60 field-effect transistors fabricated using the self-assembled monolayer (SAM)-free SrTiO3 as an insulator showed well-saturated output characteristics at a driving voltage as low as -3 or 3 V. Hole mobility of the pentacene-FET was 0.28 cm2 V-1 s-1, while electron mobility of the C60-FET was 0.09 cm2 V-1 s-1.
Solution-Processed Small Molecular Organic Light-Emitting Devices with a Mixed Single Layer
Authors: Wang Zhaokui , Naka Shigeki , Okada Hiroyuki
Published: January 2011

We investigated the characteristics of solution-processed mixed-single-layer organic light-emitting devices (OLEDs) by mixing an electron injection material, a hole transport material, and a dopant material based on 5,6,11,12-tetraphenylnaphthacene (rubrene). The mixed-single-layer OLEDs showed better performance by optimizing the solution concentration and mixing ratio of organic materials. The performance was further improved by mixing chloroform (95 wt %) and toluene (5 wt %) as a solvent. The maximum luminance and power efficiency obtained were 12,400 cd/m2 and 1.1 lm/W, respectively. The mixed-single-layer OLEDs by solution process can be expected as an alternative route to the fabrication of small-molecular OLEDs with reduced cost of devices and avoiding the complexities of the co-evaporation of multiple organic materials in the vacuum deposition process.
Highly Efficient Green Phosphorescent Organic Light-Emitting Diodes with High Electron Mobility
Authors: Choi Eun Young , Seo Ji Hyun , Kim Heo Min , Lee Kum Hee , Kang Hyun Ju , Yoon Seung Soo , Kim Young Kwan
Published: January 2011

We demonstrated highly efficient green organic light-emitting diodes (OLEDs) by inserting a mixed hole blocking layer (HBL) between the emitting layer (EML) and electron transporting layer (ETL). We compared 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP), N-arylbenzimidazoles trimer (TPBi), and 4,7-diphenyl-1,10-phenanthroline (Bphen) as the hole blocking layer. Thereafter, we mixed BCP with TPBi and Bphen. We obtained improved efficiency from the mixed HBL devices and the TPBi mixed with BCP device showed the best efficiency.
Fabrication of Organic Light-Emitting Diodes Using Photosynthetic Pigments Extracted from Spinach
Authors: Ohtani Naoki , Kitagawa Natsuko , Matsuda Takashi
Published: January 2011

We fabricated organic light-emitting diodes (OLEDs) containing chlorophylls in the active region, which were extracted from spinach using a chemical method. Photoluminescence (PL) cannot be observed in the thin film of the extracted chlorophylls owing to concentration quenching. To overcome the concentration quenching, a host material, poly[(m-phenylenevinylene)-alt-(2,5-dihexyloxy-p-phenylenevinylene)] (PPV) was added in the active region. This leads to the observaton of electroluminescence (EL) signals originating from chlorophyll a. We also evaluated the lifetime of the PL and EL. Consequently, the OLEDs containing carotenoids in the active region exhibit the light-emission much longer time than that without carotenoidos. This is assigned to the antioxidant activities of carotenoids. OLEDs containing a large amount of carotenoids are resistant to the oxidation damage.
Self-Aligned Organic Light-Emitting Diodes with Color Changing by Ink-Jet Printing Dots
Authors: Satoh Ryu-ichi , Naka Shigeki , Shibata Miki , Okada Hiroyuki , Inoue Toyokazu , Miyabayashi Takeshi
Published: January 2011

The self-aligned color-changeing organic light-emitting diodes with the ink-jet printing (IJP) dots have been investigated, and we have studied a device structure of a micro-area color-changeing method involving the IJP emission of dots and their periphery, where a side-coupling emission mode and double-area emission mode were used. The distance of the side-coupling emission from emission dot was estimated to be 10 µm. The brightnesses of the dots and their periphery at 100 mA/cm2 were 1,300 and 380 cd/m2, respectively.
Double-Faced Organic Light-Emitting Device Using Laminate Method
Authors: Minani Takahiro , Satoh Ryu-ichi , Okada Hiroyuki , Naka Shigeki
Published: January 2011

We proposed a laminate method, which demonstrates a double-faced organic light emitting device. This device can display different images at both sides. To carry out a simple fabrication process, a lamination process was carried out at the interface between a refection cathode on a poly(ethylene naphthalate) (PEN) film and on organic emission layer on a glass substrate. This device yields the ultimate low-cost product and does not require a high vacuum pressure.
Charge Transporting Properties and Output Characteristics in Polythiophene:Fullerene Derivative Solar Cells
Authors: Tsai Yueh-Tsung , Goto Kensuke , Yoshikawa Osamu , Mori Shogo , Sagawa Takashi , Yoshikawa Susumu
Published: January 2011

The carrier mobility (µ) and lifetime (τ) of polymer solar cells based on the active layer with various compositions of regioregular poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) have been investigated through photoinduced charge carrier extraction by linearly increasing voltage measurement. Increase in the PCBM content resulted in the increase in the mobility up to one order of magnitude and the highest performance was attained at the composition of P3HT:PCBM (3:2), which corresponds to the bending point of mobility and lifetime. Furthermore, the mobility-lifetime product µτ was almost constant with various weight ratios of P3HT and PCBM. This result implies that the composition does not affect the charge correction efficiency before recombination. A semiconducting thin-film optics simulator was applied for prediction of the photovoltaic performance. Theoretical and experimental cell performance results were in good agreement with each other.
Enhancement of the Open-Circuit Voltage and Hole Conduction of Tetraphenyl Porphyrin/C60 Multilayered Photovoltaic Device by the Insertion of Oxide Hole Collection Layers
Authors: Itoh Eiji , Higuchi Yuji , Furuhata Daisuke , Shirotori Toshiki
Published: January 2011

We investigated the photovoltaic properties of organic multilayered photovoltaic devices consisting of Indium–tin-oxide (ITO)/oxide/tetraphenyl porphyrin (H2TPP, ZnTPP)/fullerene (C60)/bathocuproine (BCP)/Al structures. The open-circuit voltage V
OC increases with the thickness of porphyrin layers between 10 and 30 nm. The upper limit of V
OC is attributed to the built-in potential and the energy difference between the highest occupied molecular orbital (HOMO) of H2TPP and the lowest unoccupied molecular orbital (LUMO) of the C60 layer ΔE. The use of oxide hole collection layers, such as NiO and MoO3, is effective for increasing the built-in potential across the organic layers resulting in the improved V
OC. The “kink” in the J–V curve observed at approximately V
OC for the device with a thick H2TPP layer and the device with and without a MoO
x
layer is analyzed on the basis of the Poole–Frenkel and Schottky models assuming the amorphous porphyrin layers as dielectrics. The resistance of the organic layers is dominated by the field-dependent bulk resistance of H2TPP films for V<V
OC, whereas the kink above V
OC was attributed to the relatively high Schottky barrier for holes at the ITO/H2TPP and ITO/MoO3 interfaces.
Vapor Sensing Using Waveguide-Based Multiple Surface Plasmon Resonance Sensors
Authors: Shinbo Kazunari , Mizusawa Kenta , Takahashi Hayato , Ohdaira Yasuo , Baba Akira , Kato Keizo , Kaneko Futao , Miyadera Nobuo
Published: January 2011

Multiple surface plasmon resonance (SPR) sensors were prepared on a waveguide, and vapor sensing was carried out. A BK-7 slide glass was used as a waveguide core, and three pairs of Ag films (50 nm)/polymer films with various thicknesses were prepared separately on the waveguide. White light was input from the substrate edge, and the spectrum of the output light was observed. Discrete SPR dips can be observed in the output light spectra by selecting the dielectric constant and the thickness of the polymer film, which govern the SPR condition. The sensors with poly(vinyl alcohol) as sensing material were prepared and the water vapor sorption properties were investigated. Furthermore, polyisoprene, poly(vinyl carbazole), poly(methyl methacrylate), and perfluorinated polymer were used as sensing materials, and the detection of various vapors was carried out.
Study of Liquid Crystal Alignment Formed Using Slit Coater
Authors: Sato Hideaki , Miyashita Katsuyoshi , Kimura Munehiro , Akahane Tadashi
Published: January 2011

Liquid-crystal (LC)-coated substrates with a planar LC alignment can be fabricated by UV irradiation during LC coating using a slit coater. The alignment transition from a planar alignment to a vertical alignment was caused by UV irradiation after LC coating when a certain UV-curable additive was doped with the nematic LC. These results are applicable to the development of a novel fabrication technology for printable LC devices.
Mesitylene-Solvated Monolayers by Thermal Hydrosilylation
Authors: Lee Michael V. , Lee Jonathan R. I. , Willey Trevor M.
Published: January 2011

In this paper we show near-edge X-ray absorption fine structure (NEXAFS) analysis of monolayers that are formed by thermal hydrosilylation from 1-alkene diluted in mesitylene. The monolayers are not purely aliphatic as originally proposed. Instead the bound molecules have an alkenyl structure that is promoted by the presence of mesitylene. The double bonds are more prevalent than in our previous report for monolayers formed without mesitylene. Simulated NEXAFS spectra suggest that the double bonds are present in the form of 2-alkenyl moieties. The presence of double bonds impairs the use of these monolayers as dielectrics and enables their use for conductive interfaces.
Structural and Magnetic Properties of Fe and Au Ion-Implanted Al2O3 Single Crystals
Authors: Kinoshita Ryosuke , Sakamoto Isao , Hayashi Nobuyuki , Nomura Kiyoshi , Honda Shigeo , Ishida Tomoya , Iio Satoshi , Tashiro Hiroyuki , Toriyama Tamotsu
Published: January 2011

Au ion implantation in Fe ion-implanted Al2O3 (Fe/Al2O3) has been performed in order to tailor the structural, magnetic and optical properties of Fe granules in Al2O3 matrix. After Au ion implantation, Rutherford backscattering (RBS) measurements indicate the decrease and the redistribution of retained Fe atoms with the inclusion of Au atoms, and the patterns of X-ray diffraction (XRD) show the formation of Au granules in the Fe/Al2O3. Besides, the magnetization curves of the Fe/Al2O3 after Au ion implantation show still the superparamagnetic characteristics and the decrease of saturation magnetization, and the optical absorption measurements indicate the formation of Au granules in the Fe/Al2O3 in accordance with the XRD result. In addition, we investigated a behavior of Fe granules in Al2O3 matrix by conversion electron Mössbauer spectroscopy (CEMS), which indicates the decrease of superparamagnetic state as a function of Au ion dose. As a result, it is suggested that Au ion implantation has potentialities to tailor the physical properties of Fe granules in Al2O3 matrix.
Fourier-Transform Infrared Absorption Spectroscopy of Chromium Nitride Thin Film
Authors: Shirahata Jun , Ohori Tetsutaro , Asami Hiroki , Suzuki Tsuneo , Nakayama Tadachika , Suematsu Hisayuki , Niihara Koichi
Published: January 2011

Chromium nitride thin films were deposited by RF reactive unbalanced magnetron sputtering on (100) Si single-crystal or glassy carbon substrates. The characteristics of the thin films were measured by Rutherford backscattering spectroscopy, X-ray diffractometry, and scanning electron microscopy. From the results of the above measurements, it was found that our samples were stoichiometric chromium nitride thin films. The chemical bonding state was estimated using the results of the Fourier-transform infrared spectroscopy. A peak attributed to the Cr–N bond was observed at around 380 cm-1, and it could be obtained with any beam splitter and atmosphere. Furthermore, the influence of residual stress was also investigated. Residual stresses of CrN thin films, which were calculated from their strains, were quite low.
Effect of Mechanical Alloying Parameters on the Formation of Ni–Cu Solid Solution Coating on the Ni Balls
Authors: Farahbakhsh Iman , Zakeri Alireza , Manikandan Palavesamuthu , Tanaka Shigeru , Hokamoto Kazuyuki
Published: January 2011

Mechanical alloying is a viable technique to produce coatings of limited thickness on a solid substrate. Elemental copper powder was mechanically alloyed with nickel balls in a planetary ball mill under various milling times and rotation speeds. The mutual diffusion of the elements during milling which led to the formation of a Ni–Cu solid solution and the creation of Ni–Cu coating on the surface of Ni balls was studied. The maximum hardness of the coating increased to threefold (HV0.01594) that of the substrate. Micro-structural characterization of the coating surface using optical microscope, scanning electron microscope (SEM), and electron probe micro-analyzer (EPMA) indicates that, by using appropriate processing conditions, a thick, fully-dense coating can be metallurgically bonded to the nickel balls. X-ray diffraction (XRD) results revealed the formation of nanocrystalline solid solutions.
Surface Electronic Properties of Discontinuous Pd Films during Hydrogen Exposure
Authors: Zhao Ming , Nagata Shinji , Shikama Tatsuo , Inouye Aichi , Yamamoto Shunya , Yoshikawa Masahito
Published: January 2011

This paper explored the change in the surface resistance of the discontinuous palladium (Pd) films during hydrogen exposure. In our experiments, we observed a remarkable rise in the electrical resistance of the discontinuous film which consists of nano-sized particles, when it was exposed to thin hydrogen. By studying the resistance change ratio before and after hydrogen exposure, we have found that it demonstrates an inverse exponential relationship with the ratio of on-film particle radius to the inter island separation. This suggests that the change in the film resistance under hydrogen exposure is primarily associated with the variation of surface work function which is caused by the hydrogen absorption on the Pd surface.
Preparation of Scandia-Stabilized Zirconia Electrolyte Thin Films for Intermediate Temperature-Solid Oxide Fuel Cells by Electron Beam Vapor Deposition
Authors: Hong Young Sun , Yoon Hyon Hee
Published: January 2011

Thin films of scandia-stabilized zirconia (ScSZ) for a solid oxide fuel cell (SOFC) electrolyte were prepared using electron beam vapor deposition. The effects of annealing temperature, substrate temperature, and e-beam gun power on the structure and surface morphology of the thin films were examined. It was found that the ScSZ thin film samples annealed at approximately 1000 °C consisted of a single cubic phase. The crystal orientation of the ScSZ films increased with substrate temperature and with e-beam gun power. A good adhesion to the substrate and a columnar structure were observed from the fractured cross-sectional view of the ScSZ films on a NiO-YSZ anode substrate. The ionic conductivity of the ScSZ film with 2.5 µm thickness was observed to be 9.46×10-3 S cm-1 at 700 °C with the conduction activation energy of 0.82 eV. The results in this study showed that the crystallite size of the ScSZ thin films and thus the electrochemical properties can be improved by optimizing e-beam deposition conditions and annealing temperature.
Change in Magnetic Characteristics of NiFe2O4 Nanoparticles upon Organic Matter Adsorption and Desorption
Authors: Kurosawa Ryo , Suzuki Tsuneo , Nakayama Tadachika , Suematsu Hisayuki , Niihara Koichi
Published: January 2011

The change in magnetic characteristics of NiFe2O4 nanoparticles upon the absorption of oleic acid and their desorption by heat treatment was examined in this research. With a heat treatment at 600 °C, the median diameter increased from 5.4 to 16.2 nm. However, the saturation magnetization varied by only 0.3%. On the other hand, with the coating of oleic acid, the saturation magnetization of NiFe2O4 nanoparticles decreased from 31.7 to 30.0 emu/g. After desorption by heat treatment at 600 °C, the saturation magnetization was increased. From these results, it was clear that coating NiFe2O4 nanoparticles with oleic acid decreased the saturation magnetization. This phenomenon may enable us to control the magnetization characteristics of nanoparticles.
Anomalous Hall Effect and Magnetoresistance in Mn-Doped ZnSnAs2 Epitaxial Film on InP Substrates
Authors: Oomae Hiroto , Asubar Joel T. , Jinbo Yoshio , Uchitomi Naotaka
Published: January 2011

We present for the first time the temperature dependence of resistivity, anomalous Hall effect, and extraordinary magnetoresistance (MR) in 6.5% Mn-doped ZnSnAs2 epitaxial film prepared by molecular beam epitaxy (MBE) on InP(001) substrates. The magnetic field dependence of magnetization (M–H curve) show clear hysteresis loops at 300 K for magnetic fields applied both perpendicular and parallel to the sample surface. The Curie temperature was evaluated to be 350 K. Near-zero-field hysteresis loops in the anomalous Hall resistance were also observed at various temperatures corresponding to the hysteretic out-of-plane magnetization of the sample. Negative and positive values of MR were observed in the low-field region. The behavior of the MR can be properly described by the Khosla–Fischer semi-empirical model for spin scattering of carriers in an impurity band. These characteristics strongly indicate a carrier-spin interaction in Mn-doped ZnSnAs2.
Preparation of Nickel Thin Sheets with Nanosized Ferrites by Combustion Synthesis and Electroforming
Authors: Choi Yong , Baik Nam Ik
Published: January 2011

Composite nickel sheets with nanosized nickel–zinc ferrite particles were prepared as electromagnetic shielding materials by electroforming in a modified nickel–sulfate bath with nickel–zinc ferrite particles. The nanosized nickel–zinc ferrites were prepared by combustion synthesis and mechanical milling. The combustion temperature and propagation rate were about 1150 °C and 8.9 mm/s, respectively. Neutron diffractometry revealed that the final nickel–zinc ferrites formed by combustion synthesis followed by mechanical milling were Ni0.42Zn0.58Fe2O4 with the crystal structure and lattice parameter of F
d3m and 0.84124 nm, respectively. Microstructure observation and chemical analysis by transmission electron microscopy and energy-dispersive spectroscopy respectively showed that nanosized nickel–zinc ferrite particles with a diameter of about 20 nm exist in the thin composite nickel sheet. Maximum magnetization (M
s), residual magnetization (M
r), and coercive force (i
H
c) were 7.75 Wb/m2/kg, 0.88 m3/kg, and 1297 A/m, respectively. The complex permeability decreases with an increase in frequency, and its real value (µr') has an maximum at about 0.65 GHz.
Influence of Hydrothermal Conditions on Size of Template Particles for Textured Ceramics
Authors: Bai Shan , Wen Yuqing , Zhang Fan , Karaki Tomoaki , Adachi Masatoshi
Published: January 2011

We report the influences of the sodium dodecyl-benzenesulfonate (SDBS), hydrothermal reaction temperature and time on the size of potassium sodium niobate (K,Na)NbO3 (KNN) template particles to determine the regularities of these changes. In the reaction with a small autoclave, when the quantity of SDBS reached 1.5 wt %, the width of the obtained platelike KNN-hydrate particles reached a maximum of 1.5 µm and the thickness was 0.15 µm, meaning that the aspect ratio was 10/1. To accommodate practical applications, a large autoclave was used in the following hydrothermal reaction. We found that the size of the platelike particles increased with improved reaction temperature and time. Particles 1.5 to 5 µm wide and 0.15 to 0.4 µm thick were prepared. After calcining these particles at 450 °C, platelike KNN template particles were obtained. Finally, tape-casting results showed that the platelike KNN templates have the (100) orientation.
Preparation and Characterization of Cr–Zn–N–O Thin Films Deposited by Pulsed Laser Deposition
Authors: Suzuki Tsuneo , Sekiguchi Fumiya , Shirahata Jun , Asami Hiroki , Nakayama Tadachika , Suematsu Hisayuki , Niihara Koichi
Published: January 2011

Cr–N–O, Cr–Zn–N–O, and Zn–O thin films were prepared by pulsed laser deposition. The compositional analysis of the Cr–Zn–N–O thin films by Rutherford backscattering spectroscopy revealed that they are ternary compounds of the Cr–Zn–N–O system. Their Vickers hardness was about 4200 kgf/mm2. X-ray diffraction indicated that the Cr–N–O and Cr–Zn–N–O thin films have the NaCl-type structure (B1), the same as CrN. Transition electron microscopy observation indicated that a grain of the (Cr,Zn)(N,O) phase existed, on the basis of which it could be considered as a solid solution of B1-CrN and a high-pressure phase of ZnO with the B1 structure.
Step Hall Measurement of InSb Films Grown on Si(111) Substrate Using InSb Bilayer
Authors: Nakayama Koji , Nakatani Kimihiko , Khamseh Sara , Mori Masayuki , Maezawa Koichi
Published: January 2011

We investigated the in-depth profile of electrical properties of InSb films grown on Si(111) substrates using various InSb bilayers. The InSb bilayers were prepared using three types of initial In-induced surface reconstructions on Si(111) substrates such as √3×√3-In, 2×2-In, and √7×√3-In. The InSb films were grown using a two-step growth procedure. In the growth procedure, the 1st layer was deposited using at a low growth rate of about 1 Å/min. The in-depth profile of the electrical properties of the InSb films was obtained by reciprocally repeated chemical etching and Hall measurement. The electron mobility of the films was gradually decreased with decreasing thickness. The electron mobility at room temperature of the InSb film grown via √7×√3-In surface reconstruction was estimated to be about 61,000 cm2/(V·s) in the region near the surface and about 20,000 cm2/(V·s) in the region approximately 0.2 µm from the InSb/Si interface. These indicate that the high electron mobility of the samples grown on the InSb bilayer using at a low growth rate during the first layer deposition originated from the reduction of the regions with low electron mobility near the InSb/Si interface.