bluuebunny/crossref_metadata_2025 huggingface dataset:
Nanoshaving of bovine serum albumin films adsorbed on monocrystalline surfaces and interfaces
Authors: Kolivoška Viliam , Gál Miroslav , Lachmanová Štěpánka , Janda Pavel , Sokolová Romana , Hromadová Magdaléna
Published: August 2011

We apply the ex situ and in situ atomic force microscopy (AFM) nanoshaving technique to investigate the bovine serum albumin (BSA) films on Au(111) and highly oriented pyrolytic graphite (HOPG) surfaces. The both substrates were found to support the BSA films. The section analysis performed before and after the AFM nanoshaving allowed the determination of the film thickness. On Au(111) surface, both ex situ and in situ nanoshaving revealed that the film is formed by strongly denatured BSA molecules, with the average thickness 2.3 ± 0.2 and 2.0 ± 0.2 nm, respectively. On the other hand, the HOPG substrate was found to support less denatured BSA films, with the average film thickness 4.7 ± 0.3 and 5.2 ± 0.3 nm, based on the ex situ and in situ measurements, respectively.
The Princess Marina Hospital accident and emergency triage scale provides highly reliable triage acuity ratings
Authors: Twomey Michele , Mullan Paul C , Torrey Susan B , wallis Lee , Kestler Andrew
Published: August 2011

Objective

To determine the interrater reliability of triage acuity ratings by healthcare workers (HCW) using a previous triage system (PTS) and the Princess Marina Hospital accident and emergency centre triage scale (PATS), a local adaptation of the widely used and studied South African triage scale.

Methods

A cross-sectional study was performed on HCW in an emergency department (ED) in Botswana to determine the interrater reliability of triage acuity ratings when using PTS and PATS to assign triage categories to 25 written vignettes after PATS training. The intraclass correlation coefficient (ICC) was calculated to assess interrater reliability, and graphic displays were used to portray rating distributions for vignettes with a mean rating of different acuity categories for PTS and PATS.

Results

44 HCW completed the scenarios. The ICC for the group of HCW was 0.52 (95% CI 0.37 to 0.67) using PTS and 0.87 (95% CI 0.80 to 0.93) using PATS. The ICC values were higher for PATS than PTS regardless of the number of years of experience of the HCW and the level of the HCW (specialist, medical officer, nurse, nurse aide). Graphic displays showed that there was less variability at all acuity levels when using PATS compared with PTS.

Conclusion

The reliability measures in this study indicate very high interrater agreement and limited variability in acuity ratings when using the PATS as opposed to moderate agreement and increased variability in acuity ratings when using PTS. This suggests that PATS is reliably applied by all levels of HCW and supports the feasibility of the further implementation of PATS in ED in Botswana and in other similar settings.
Continued use of the Standard Days Method®
Authors: Sinai Irit , Lundgren Rebecka I , Gribble James N
Published: August 2011

Objective

To examine the long-term effectiveness and continuation of the Standard Days Method (SDM)®, a fertility awareness-based method of family planning that identifies Days 8–19 (inclusive) of the cycle as the fertile window. On these days users avoid unprotected sexual intercourse to prevent pregnancy. The method works best for women with cycles that are usually in the range of 26–32 days, which is an important reason for method discontinuation in the first year of use. The authors determine if this continues to be an issue in the second and third years of method use.

Methods

Participants in an earlier efficacy study (478 women in three countries) and method introduction studies (1181 women in four countries) were followed for 2 years beyond the original 1-year study period, to determine their continued use of the method, intended and unintended pregnancies, and reasons for discontinuation. Life-tables were used to approximate typical use pregnancy rates.

Results

The method continues to be effective in the second and third years of use, and compares favourably to other user-directed family planning methods. Women with no more than two cycles outside the 26–32-day range within a year are likely to continue having cycles within this range.

Conclusions

Women who complete the first year of SDM use are likely to continue to be able to use the method successfully and effectively. The method presents a viable longer-term option for women who prefer this approach to family planning.
The Standard Days Method®: an addition to the arsenal of family planning method choice in Ethiopia
Authors: Bekele Biruhtesfa , Fantahun Mesganaw
Published: August 2011

Background and methodology

The Standard Days Method® (SDM) is a fertility awareness-based method of family planning that helps users to identify the fertile days of the reproductive cycle (Days 8–19). To prevent pregnancy users avoid unprotected sexual intercourse during these days. A cross-sectional community-based study was conducted from December 2007 to June 2008 in four operational areas of Pathfinder International Ethiopia. A total of 184 SDM users were included in the study. Quantitative and qualitative methods of data collection were used. The aim of the study was to examine the experience of introducing the SDM at community level in Ethiopia.

Results

Of the 184 participants, 80.4% were still using the SDM at the time of the survey, with 35% having used it for between 6 and 12 months, while 42% had used it for more than a year. The majority (83%) knew that a woman is most likely to conceive halfway through her menstrual cycle, and nearly 91% correctly said that the SDM does not confer protection from sexually transmitted infections/AIDS. A substantial majority (75%) had correctly identified what each colour-coded bead represents in the CycleBeads®, and an aggregate of 90.5% of women practised all the elements of correct use.

Discussion and conclusions

This study demonstrates the importance of the SDM in increasing the availability and accessibility of family planning, and the potential to improve family planning method choice and method mix by expanding use of the SDM.
Deep Traps in InAlN Lattice-Matched to GaN Grown by Metal Organic Chemical Vapor Deposition Studied by Deep-Level Transient Spectroscopy
Authors: Chen Zhitao , Fujita Kazuhisa , Ichikawa Junki , Sakai Yusuke , Egawa Takashi
Published: August 2011

In
x
Al1-x
N lattice-matched to GaN with recording crystal quality have been grown on AlN/sapphire template by metal organic chemical vapor deposition. The width at half maximums (FWHMs) of X-ray diffraction (XRD) ω-rocking curves are as low as 100 arcsec for (0002) reflection and 248 arcsec for (1012) reflection, respectively. Deep level transient spectroscopy (DLTS) technique has been employed to investigate the deep traps in InAlN. Three deep traps were observed with activation energies of E
1 = 0.351 ±0.018, E
2 = 0.404 ±0.027, and E
3 = 0.487 ±0.026 eV, respectively. The capture kinetic behaviors of E
1 and E
3 were investigated, and it is believed that E
1 is associated with point defects while E
3 is related to dislocations.
The Observation of “Conduction Spot” on NiO Resistance Random Access Memory
Authors: Kondo Hirofumi , Arita Masashi , Fujii Takashi , Kaji Hiromichi , Moniwa Masahiro , Yamaguchi Takeshi , Fujiwara Ichiro , Yoshimaru Masaki , Takahashi Yasuo
Published: August 2011

We succeeded in observing the “conduction spot” (CS) in the capacitor structure resistance random access memory (ReRAM), which includes a conductive filament. In this study, we used NiO prepared by thermal oxidation at a high temperature as 800 °C. It requires a forming process using an extra high voltage, which partly removes the top electrode from the resistance switched area. These experiments enabled us to observe the conductive filament directly in CS on NiO ReRAM by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). From SEM images, CSs seem to be produced by some kind of breakdown, but we confirmed the reproducible resistance switching at least 50 cycles after the CS generation. By energy dispersive X-ray spectroscopy (EDX) with TEM observations, drastic oxygen reduction was observed in a local area within CS of NiO films. Moreover, the CS area depended on the injection power for forming. These experimental data suggest that the miniaturization of ReRAM will be achieved by reducing the injection power for forming.
Effects of Heat Treatment on the Resistive Switching Characteristics of Pt/NiO/Pt Stack Structures
Authors: Iwata Tatsuya , Nishi Yusuke , Kimoto Tsunenobu
Published: August 2011

Effects of heat treatment on the resistive switching characteristics of Pt/NiO/Pt cells were investigated. Heat treatment was carried out under various conditions, and different resistive switching characteristics were obtained depending on the oxygen desorption from NiO films. After heat treatment by which the oxygen composition of the NiO films was not changed, the resistance ratio was markedly improved owing to the increase in the initial resistance (R
Ini). It was revealed that the increase in R
Ini is linked to the increase in its activation energy, which may be related to carrier excitation from defect states. On the other hand, many of the cells were initially in the low-resistance state after heat treatment by which the oxygen desorption from NiO films took place. This result indicates the formation of conductive filaments by oxygen desorption.
Fabrication of Multilevel Switching High Density Phase Change Data Recording Using Stacked GeTe/GeSbTe Structure
Authors: Hong Sung-Hoon , Lee Heon , Kim Kang-In , Choi Yunjung , Lee Young-Kook
Published: August 2011

The multilevel switching characteristics of stacked phase change materials with the structures of Ge2Sb2Te5, AgInSbTe/Ge2Sb2Te5, and GeTe/Ge2Sb2Te5were investigated at the nano scale using nanoimprint lithography and conductive atomic force microscopy. Stacked phase change materials devices consisting of nano pillars 200 nm in diameter were fabricated using nanoimprint lithography, and their electrical characteristics were evaluated using conductive atomic force microscopy, with a pulse generator and a voltage source. The stacked GeTe/Ge2Sb2Te5phase change materials exhibited three levels of resistance with a difference of 2 orders in magnitude between them, while the single-layer and stacked phase change materials with similar electrical resistances, such as Ge2Sb2Te5/AgInSbTe exhibited only bi level switching characteristics.
k·p Zincblende Hamiltonian and Optical Matrix with Bulk Inversion Asymmetry
Authors: Chen Chun-Nan , Su Wei-Long , Lee Meng-En , Jen Jen-Yi , Li Yiming
Published: August 2011

A conventional 8 ×8 k·p zincblende Hamiltonian is corrected to include the bulk (or intracell) inversion asymmetry. Meanwhile, a conventional 8 ×8 k·p zincblende optical matrix is also corrected to include this intracell asymmetry.
Direct Synthesis and Enhanced Catalytic Activities of Platinum and Porous-Silicon Composites by Metal-Assisted Chemical Etching
Authors: Nakamura Toshihiro , Tiwari Bishnu P. , Adachi Sadao
Published: August 2011

We demonstrate that Pt/PSi composite powders can be prepared by a simple method involving the metal-assisted electroless chemical etching of Si powders. In X-ray photoelectron spectroscopy and optical measurements, Pt layers are deposited on a Si surface together with the formation of a porous structure. It is found that the oxidation state of Pt layers strongly depends on the conditions for the preparation of Pt/PSi composite powders. Furthermore, Pt/PSi composite powders show an enhanced catalytic activity caused by the Pt metal layer deposited on the nanostructured Pt/PSi surface.
Electron Spin Resonance of Chromium–Platinum Pair in Silicon
Authors: Ishiyama Takeshi , Tsurukawa Takahiro , Mori Yuya , Kamiura Yoichi , Yamashita Yoshifumi
Published: August 2011

We have investigated a chromium–platinum pair in silicon by electron spin resonance measurement. A new ESR spectrum originating from a chromium–platinum pair has been detected in both n- and p-type silicons diffused with chromium and platinum. The anisotropic g-tensor obtained by analyzing the angular dependence of the ESR spectrum shows a monoclinic (C
1h
) symmetry with g-values of g
1=4.67, g
2=2.99, and g
3=1.80. The g
1 axis is along the <110 > direction. The g
2 and g
3 axes are perpendicular to the g
1 axis, and the g
2 axis is rotated from the <100 > direction to the <111 > direction at an angle of 20°. The anisotropic character of monoclinic (C
1h
) symmetry results from the nearest-neighbor configuration consisting of a Pt atom at a substitutional site distorted by the displacement of Pt along the <100 > direction and a Cr atom at the nearest-neighbor interstitial site. The ESR measurement under illumination suggests that a chromium–platinum pair forms a donor like electron trap level.
Low-Temperature Sintering of Negative–Positive-Zero-Type Temperature-Stable Ceramics with ZnO–B2O3 Flux and SrCO3 Additive
Authors: Sun Changku , Wang Xiaohui , Ji An , Li Longtu
Published: August 2011

To demonstrate that tungsten–bronze-based NP0 (negative–positive zero, also called C0G) specification ceramics can be sintered at a low temperature to reduce the cost of capacitor production, systematic investigation has been performed on the structure and dielectric properties of such ceramics doped with SrCO3 in various amounts and ZnO–B2O3 powders of different compositions as sintering aids. A novel dielectric ceramic material with good permittivity, low dielectric loss, and a near-zero temperature coefficient was obtained at a sintering temperature of 900 °C, meeting NP0 specifications. The analysis reveals the pyrochlore phase formation of the low-temperature-fired ceramics with no SrCO3 addition, which verifies the beneficial role of Sr in facilitating the production of pure phases. The results also suggest that the ceramics serve as a promising candidate for fabricating inexpensive multilayer capacitors with pure Ag as the inner electrode.
Air-Stable Inverted Organic Solar Cells with Pentacene Anode Buffer Layer
Authors: Oida Tatsuya , Naito Tatsuhiro , Miyagawa Yuki , Sasaki Muneo , Harafuji Kenji
Published: August 2011

A small-molecular organic solar cell with an inverted structure of indium–tin oxide (ITO)/bathocuproine (BCP)/fullerene (C60)/copper phthalocyanine (CuPc)/pentacene/Ag is reported. Although the Ag electrode usually acts as the cathode because of its low work function, the Ag electrode appropriately works as the anode by inserting a pentacene thin layer between Ag and the active layer. The unencapsulated device shows a power conversion efficiency of 0.28% under 100 mW/cm2 AM1.5G simulated illumination, and a lifetime of 700 h. The lifetime is 700 times longer than that of a conventional device with a structure of ITO/CuPc/C60/BCP/Ag. The long lifetime is attributed to the inverted structure in which the top electrode acts as the anode because this structure could effectively protect C60 from the diffusion of oxygen. By substituting naphthalene-1,4,5,8-tetracarboxylic dianhydride for BCP as a cathode buffer, the power conversion efficiency and the lifetime are improved to 0.40% and more than 1200 h, respectively.
Metal Deposition Selectivity Based on Photochromism of Diarylethene Film in Intermediate Vacuum
Authors: Iwai Yusuke , Tsujioka Tsuyoshi
Published: August 2011

We report on metal deposition selectivity on a photochromic diarylethene (DAE) surface in intermediate vacuum. Selective deposition means that metal vapor is deposited on colored DAE but not on uncolored. Mg was evaporated on the DAE surfaces at various pressures with the introduction of inert gas. Mg was easy to deposit on the uncolored DAE surface in intermediate vacuum (2×10-1 Torr). The easy-deposition effect in intermediate vacuum was explained by the re-adsorption of Mg atoms desorbed from the DAE surface. Mg cathode patterning of an organic light emitting device on the basis of selective deposition in the intermediate vacuum was successfully demonstrated.
Real-Time Ellipsometric Characterization of Initial Growth Stage of Poly(3,4-ethylene dioxythiophene):Poly(styrene sulfonic acid) Films by Electrospray Deposition
Authors: Ino Tomohisa , Asano Takashi , Fukuda Takeshi , Ueno Keiji , Shirai Hajime
Published: August 2011

Kinetic spectroscopic ellipsometry has been used to study the initial growth stage of poly(3,4-ethylene dioxythiophene):poly(styrene sulfonic acid) (PEDOT:PSS) films by the electrospray deposition (ESD) method. The real-time spectra analysis revealed that the surface overlayer decreased in thickness, once the first bulk layer monolayer was formed, indicating a smoothening effect as the nucleation-related microstructure coalesced into the bulk layer. Once the coalescence was completed and the nucleation-induced surface roughness layer was stabilized, the underlying bulk layer increased linearly with time. These results originate from the degrees of the evaporation of solvent material during the transfer of the precursors to the surface and/or of the diffusion of deposition precursors after sticking at the growing surface.
Transient Drain Current Measurement for Polymer Transistor Containing Residual Bromine Atoms
Authors: Suemori Kouji , Taniguchi Misuzu , Uemura Sei , Yoshida Manabu , Hoshino Satoshi , Takada Noriyuki , Kodzasa Takehito , Kamata Toshihide
Published: August 2011

In this study, we investigated the transient drain current characteristics of organic field-effect transistors having poly(9,9-dioctylfluorene-co-bithiophene) (F8T2) as the semiconducting layer. When the F8T2 molecules contained a high concentration of residual bromine atoms, a large decrease in drain current – on the time scale of several milliseconds – was observed upon the application of gate voltage. This decrease in drain current can be fitted accurately using a stretched exponential equation, suggesting that bromine atoms in F8T2 form traps.
Magnetic Field Effects on Photoelectrochemical Reactions of Porphyrin–Viologen Linked Compounds in an Ionic Liquid
Authors: Tahara Hironobu , Yonemura Hiroaki , Harada Satoko , Yamada Sunao
Published: August 2011

Magnetic field effects (MFEs) on photoelectrochemical reactions of three porphyrin–viologen linked compounds with various methylene groups [ZnP(n)V (n=4,6,8)] were examined in 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF4]) as an ionic liquid using a two-electrode cell. Stable anodic photocurrents are produced by irradiating ZnP(n)V (n=4,6,8) in [BMIM][BF4] with visible light, and the MFEs on photocurrents were clearly observed in ZnP(n)V (n=4,6,8). The MFEs on photocurrents increase with magnetic field for lower magnetic fields (B ≤200 mT) and are constant for higher magnetic fields (B > 200 mT). The magnitude of the MFEs in ZnP(n)V (n=6,8) are larger than that in ZnP(4)V. The MFEs can be explained by radical pair mechanism. The magnitude of the MFEs is larger than those in electrodes modified with ZnP(n)V (n=4,6,8) as Langmuir–Blodgett films. The results are most likely attributable to the properties of [BMIM][BF4] and the mechanism of photoelectrochemical reaction.
Adsorption of Phenylphosphonic Acid on Gold and Platinum Surfaces
Authors: Yagyu Shinjiro , Yoshitake Michiko , Tsud Nataliya , Chikyow Toyohiro
Published: August 2011

The adsorption structure and thermal stability of phenylphosphonic acid (PPOA) on Au and Pt polycrystalline surfaces were investigated as a function of PPOA exposure and surface temperature, by infrared reflection absorption spectroscopy (IR-RAS) and a Kelvin probe (KP). The IR-RAS spectra of PPOA on Au and Pt were found to be similar. PPOA is adsorbed without molecule decomposition at 300 K on both surfaces. The molecularly adsorbed PPOA started to desorb at about 350 K, which is similar to the PPOA evaporation temperature. The surfaces studied were shown to be less active than Al, Ti, and Si surfaces with respect to interaction with phosphonic acid.
Control of the Molecularly Reoriented Direction in Surface Relief Holographic Gratings Using Photoreactive Liquid Crystalline Copolymers
Authors: Kawatsuki Nobuhiro , Tashima Ayaka , Emoto Akira , Ono Hiroshi , Kondo Mizuho , Okada Makoto , Matsui Shinji
Published: August 2011

Molecularly oriented surface relief (SR) structures in photo-crosslinkable liquid crystalline copolymer films were fabricated using a 325 nm He–Cd laser with p–p and s–s polarized intensity holographic beams. The SR height increased as the exposure energy increased. In contrast, the molecular orientation structure depended on the exposure dose. For all doses, molecular migration from the lower exposure region to the higher one was due to the difference in the crosslinking density. The SR height reached up to 280 nm for a film that was initially 1.0 µm thick. The diffraction efficiency depended on the fabricated SR grating, while the difference in the molecular reorientation area and the direction of the SR gratings explained the diffraction properties.
Improvement of Rear Surface Passivation Quality in p-Type Silicon Heterojunction Solar Cells Using Boron-Doped Microcrystalline Silicon Oxide
Authors: Rattanapan Suttirat , Watahiki Tatsuro , Miyajima Shinsuke , Konagai Makoto
Published: August 2011

Boron-doped microcrystalline silicon oxide (µc-SiO
x
:H) films for application as a back surface field (BSF) in p-type silicon heterojunction (SHJ) solar cells have been characterized. We found that the µc-SiO
x
:H(p) film at the optimized condition shows high conductivity and good passivation effect with a low surface recombination velocity of around 102 cm/s. However, too much oxygen atoms in the films increase the defect and the passivation quality degrades. Thus, the control of oxygen content in the films is very important to obtain a high passivation quality. With applying the µc-SiO
x
:H(p) as a BSF layer leads to improved p-type SHJ solar cells performance, which shows the enchantment of EQE spectra in long wavelengths between 800 and 1200 nm. The highest efficiency of the p-type SHJ solar cell we obtain is 18.5% (active area = 0.88 cm2) with a V
oc = 659 mV, J
sc = 34.7 mA/cm2, and FF= 80.9%.
Inverted Organic Photovoltaic Cells with Solution-Processed Zinc Oxide as Electron Collecting Layer
Authors: Zhang Chunfu , You Hailong , Lin Zhenhua , Hao Yue
Published: August 2011

In this work, inverted polymer:fullerene organic photovoltaic (OPV) cells with solution-processed zinc oxide (ZnO) as the electron collecting layer are investigated. ZnO films are prepared simply by the spin-casting of a zinc acetate dehydrate precursor solution, followed by sintering under ambient conditions. The performance of the fabricated inverted OPV cells shows a clear dependence on precursor concentration and sintering conditions. With the ZnO film derived from a sol–gel concentration of 0.1 M and sintered at 350 °C for 10 min, the inverted OPV cell shows optimum performance.
Effect of Porous Counter Electrode with Highly Conductive Layer on Dye-Sensitized Solar Cells
Authors: Rahman Mohammad Maksudur , Kojima Ryota , Fihry Mehdi El Fassy , Tadaki Daisuke , Ma Teng , Kimura Yasuo , Niwano Michio
Published: August 2011

A Pt/porous titanium (Ti)/dense Ti/aluminum (Al)/glass composite counter electrode for a dye-sensitized solar cell (DSC) was fabricated and characterized. The introduction of a highly conductive Al film drastically reduced the sheet resistance of the counter electrode to improve the short circuit current and fill factor of the DSC. Porous and dense Ti layers were deposited by the DC magnetron sputtering process. The dense Ti layer protected the Al film from dissolution in the electrolyte solution to stabilize the composite counter electrode. The porous Ti layer with a larger electrochemical active area at the electrolyte/counter electrode interface mainly improved the short circuit current of the DSC. The results indicate the importance of the introduction of porous materials with highly conductive films into the counter electrode of a DSC and the suitability of composite materials of Al and Ti for the counter electrode.
Demonstration of ZnTe1-xOx Intermediate Band Solar Cell
Authors: Tanaka Tooru , Yu Kin M. , Levander Alejandro X. , Dubon Oscar D. , Reichertz Lothar A. , Lopez Nair , Nishio Mitsuhiro , Walukiewicz Wladek
Published: August 2011

We report the optical properties of ZnTe1-x
O
x
(ZnTeO) and evidence for the photovoltaic (PV) activity of a ZnTeO intermediate band solar cell (IBSC). By photomodulated reflectance measurements, electron transitions from the intermediate band to the conduction band were demonstrated. The optical absorption coefficients for the electron transition from the valence band to the intermediate band exceeds 2×104 cm-1, suitable for thin-film PV device applications. The ZnTeO IBSC exhibits an enhanced spectral response below the band edge of ZnTe, and all results are consistent with the proposed conversion mechanism of IBSC.
Fabrication of Wide-Angle and Wideband Visible Antireflection Coating on Flexible Poly(ether sulfone) Substrate Using Ion-Assisted Deposition
Authors: Liou Yeuh-Yeong , Kuo Li-Hsiang , Hsu Chih-Hsien , Liu Wen-Long , Jaing Cheng-Chung
Published: August 2011

A wide-angle and wideband visible (vis) antireflection (AR) coating with the incident angles ranging from 0–50° was designed for a flexible poly(ether sulfone) (PES) substrate, based on a scanning search method, and then this wide-angular vis AR coating was fabricated by the ion-assisted deposition technique. It was found that not only the wide-angular vis AR performance in the designed range was acceptable, but also its vis reflectance for incident angles beyond the designed range was reduced to lower than that of the uncoated substrate, revealing an omnidirectional wideband vis antireflective effect.
Reflective Dual Mode Liquid Crystal Display with Dynamic Mode Utilizing the Transition Behavior between the Two Stable States of Its Memory Mode
Authors: Lee Joong Ha , Song Dong Han , Kim Taehyung , Shin Hun Ki , Jhun Chul Gyu , Kwon Soon-Bum , Kim Dong-Guk , Kim Wook Sung , Yoon Tae-Hoon , Kim Jae Chang
Published: August 2011

In this study, we have proposed a dual-mode liquid crystal display (D-LCD) that can display both the memory and dynamic modes in one cell. The two stable states of the memory mode use splay and -π-twist states. The operation of the dynamic mode is realized by the transition behavior between the two stable states of its memory mode. For a green display, we have also proposed a reflective D-LCD with an optically compensated structure. We found that both the memory and dynamic modes have contrast ratios (CRs) of 30:1 by a good wavelength dispersion of dark state.
AlGaN/GaN Heterostructure Field-Effect Transistors on Fe-Doped GaN Substrates with High Breakdown Voltage
Authors: Oshimura Yoshinori , Sugiyama Takayuki , Takeda Kenichiro , Iwaya Motoaki , Takeuchi Tetsuya , Kamiyama Satoshi , Akasaki Isamu , Amano Hiroshi
Published: August 2011

AlGaN/GaN heterostructure field-effect transistors (HFETs) were fabricated by metalorganic vapor phase epitaxy (MOPVE) on c-plane Fe-doped GaN (GaN:Fe) substrates with different growth conditions of GaN buffer layers. The GaN buffer layers were grown at a V/III ratio of 272 at 300 Torr to realize highly resistive GaN buffer layers with automatic carbon doping. HFETs with carbon-doped GaN buffer layers showed the best characteristics among all the samples in this study. The carbon concentration was 5×1016 cm-3. In the sample with a gate-drain length of 50 µm, the off-state breakdown voltage was 2 kV or higher and the on-resistance was 18.5 mΩ·cm2. We found that the carbon-doped GaN buffer layers are necessary for high breakdown voltages even using semi-insulating GaN:Fe substrates.
A Three-Dimensional Simulation Study of Source/Drain-Tied Double-Gate Fin Field-Effect Transistor Design for 16-nm Half-Pitch Technology Generation and Beyond
Authors: Eng Yi-Chuen , Lin Jyi-Tsong , Chang Tzu-Feng , Chen Chun-Yu , Fan Yi-Hsuan , Chen Cheng-Hsin , Lin Po-Hsieh
Published: August 2011

This paper presents a three-dimensional (3D) simulation study of source/drain (S/D)-tied (SDT) double-gate (DG) fin field-effect transistor (FinFET) design for 16-nm half-pitch technology generation and beyond using technology computer-aided design (TCAD) tools. A simple process to fabricate the proposed SDT FinFET is proposed. An investigation of the fin width (W
fin) on the electrical characteristics is shown, suggesting that a reduced W
fin is good for both the suppression of short-channel effects and the reduction of parasitic capacitance in SDT FinFETs. Also, the self-heating can be well controlled in our proposed SDT FinFET which is a difficult task for SOI family. The proposed FinFET is also compared with the existing experimental data, showing that the SDT FinFET not only demonstrates desired short-channel characteristics due to its inherent structure advantages (partially insulating oxide under the channel region), but also reduces the costs of device fabrication due to its simple process method and planar-like structure.
Ground State Instability in Spin Polarization for Electrons Confined in Two-Dimensional Square Quantum Dots
Authors: Negishi Yhuki , Ishizuki Masamu , Okunishi Takuma , Takeda Kyozaburo
Published: August 2011

We present a theoretical study of the ground state electronic structure and the spin polarization for four electrons confined in two-dimensional (2D) square quantum dots (SQDs). We employ standard mean field theory (MFT) approaches using the unrestricted Hartree–Fock (UHF) and density functional theory calculations. The resonant UHF configuration interaction (res-UHF CI) calculation was also performed in order to incorporate the electron correlation more intuitively. The MFT ground state is expected to be spin-polarized when SQDs have a small confinement length L or aspect ratio δ= L

x
/L

y
= 1, in agreement with Hund's rule. In contrast, the spin-unpolarized ground state singlet is expected in all in other SQDs. Thus, the MFT calculations produce the anti-Hund state, where the spin-density wave forms having the zero of the total spin, even though the SQD has the point group symmetry D
4h
. However, the res-UHF CI calculation restores the geometrical symmetry in the resulting ground state when the Coulomb interaction is strengthened. Nevertheless, the res-UHF CI ground state maintains the zero total spin. Thus, ground state instability is expected in the spin-polarization of the SQD system, which eventually violates Hund's rule in accordance with the Coulomb interaction.
Investigations of an Independent Double-Gated Polycrystalline Silicon Nanowire Thin Film Transistor for Nonvolatile Memory Operations
Authors: Chen Wei-Chen , Lin Horng-Chih , Huang Tiao-Yuan
Published: August 2011

In this study, we investigate the merits of an independent double-gated configuration for nonvolatile memory operations. In contrast to the convention where the programming/erasing gate also acts as the read gate, a dedicated read gate with an oxide-only dielectric is proposed in the new mode. Using the same device under identical programming/erasing conditions, greatly improved programming speed (e.g., 61% increase under the stress condition of 18 V for 10 µs) is achieved, while the erasing speed, albeit initially retarded, shows enhancement when the erasing time is larger than a certain value, which can be explained by the back-gate bias effects. Retention characterization indicates that the new mode offers a larger memory window after 10 year extrapolation. In addition, a proper auxiliary gate bias applied during programming/erasing processes is found to improve the programming/erasing speed. Finally, by taking advantage of the separate-gated feature, two independent storage sites can be obtained by employing an oxide–nitride–oxide layer as the dielectric for both gates, thus realizing 2-bit/cell functionality.
Amperometric Biosensor Based on Carbon Nanotube Functionalized by Redox Plasma-Polymerized Film
Authors: Hoshino Tatsuya , Muguruma Hitoshi
Published: August 2011

A novel fabrication approach for the amperometric biosensor based on multilayer films containing carbon nanotubes (CNT), a plasma-polymerized film (PPF), and enzyme glucose oxidase (GOD) is reported. The configuration of the electrochemical electrode is sequentially composed of sputtered gold, lower acetonitrile PPF, CNT, redox PPF, GOD, and upper acetonitrile PPF (denoted as PPF/GOD/Redox-PPF/CNT/PPF/Au). The lower acetonitrile PPF deposited on Au acts as a permselective membrane, and as a scaffold for CNT layer formation. The upper acetonirile PPF directly deposited on GOD acts as a matrix for enzyme immobilization. The redox PPF polymerized by a monomer of dimethlyaminomethlyferrocene (DAF) is directly deposited onto CNTs. The surface of the functionalized CNT has redox sites of ferrocene groups that shuttle electrons from CNTs to the sensing surface of the Au electrode. The synergy between the redox PPF and CNT provides benefits in terms of lowering the operational potential and enhancing the sensitivity (current). The optimized glucose biosensor revealed a sensitivity of 2.0 µA mM-1 cm-2 at +0.4 V vs Ag/AgCl, a linear dynamic range of 4.9–27 mM, and a response time of 5 s.
Effects of Growth Temperatures on Crystal Quality of GaN by Vapor Phase Epitaxy Using GaCl3 and NH3
Authors: Ueda Tetsuzo , Yuri Masaaki , Jr. James S. Harris,
Published: August 2011

Thick epitaxial growth of GaN by vapor phase epitaxy (VPE) is an indispensable technique to form GaN substrates which have been commonly used for blue-violet GaN-based lasers with sufficiently long lifetime. Although the growth has been established in view of the mass-production of the GaN substrate, the crystal quality has never been sufficiently correlated with the growth conditions. In this paper, the effects of the growth temperatures on the crystal quality of VPE-grown GaN films are studied in detail. It is noted that the GaN films are grown by a single-zone VPE using externally placed GaCl3 and NH3 as source precursors. The growth exhibits the growth rate of 14 µm/h at highest and far higher growth rate is possible by increasing the carrier flow rate and/or temperature of the GaCl3. The experimental results reveal that the surface morphology and optical properties are strongly dependent on the growth temperature. At around 975 °C with very narrow temperature window, very smooth surface together with a very sharp photoluminescence (PL) peak originating from bound excitons is observed. Growth at lower temperatures than the optimized window results in rough surface with many pits on it. Higher temperature results in many cracks and peeling-off on the surface with the sign of three-dimensional growth. Peaks originating from residual acceptors are dominant in the PL spectra of the films with rough surfaces grown at higher or lower temperatures from the optimized window. Flattening the surface of GaN at the optimized temperatures by the enhanced lateral growth is essential to grow thick GaN by the VPE with good crystalline quality free from the incorporation of the residual acceptors.
Tuning of Surface Roughness and Lattice Constant in MgO(111)/Al2O3(0001) Grown by Laser Energy Controlled Pulsed Laser Deposition
Authors: Kumada Sho , Matsuzaki Kosuke , Hosono Hideo , Susaki Tomofumi
Published: August 2011

We have studied the effect of variable laser energy on pulsed laser deposition (PLD) grown MgO(111) films on Al2O3(0001) substrates by X-ray diffraction and reflectivity measurements, atomic force microscopy and reflection high energy electron diffraction. In spite of the polar instability of MgO(111) surface, the surface roughness drastically decreases from ∼2 to ∼0.5 nm as the laser energy increases from ∼50 to ∼150 mJ. The in-plane lattice constant is larger than the bulk value at the smaller laser energy while it is smaller than the bulk value at the larger laser energy. This indicates that the balance between the electrostatic energy due to the polar structure, which favors a larger in-plane lattice constant, and the interface epitaxial strain, which favors a smaller in-plane lattice constant in MgO(111)/Al2O3(0001), can be tuned by varying the laser energy in PLD.
Fabrication of Carbon Nanotube/Zinc Oxide Composite Films by Electrodeposition
Authors: Kuwajima Tomoya , Nakanishi Yusuke , Yamamoto Aishi , Nobusawa Kazuyuki , Ikeda Atsushi , Tomita Satoshi , Yanagi Hisao , Ichinose Keigo , Yoshida Tsukasa
Published: August 2011

Carbon nanotube/zinc oxide (CNT/ZnO) composite films were fabricated by electrodeposition with aqueous solution of ZnCl2and water-soluble CNTs prepared using a high-speed vibration milling technique. The experimental results of secondary ion mass spectroscopy and Raman scattering spectroscopy clearly showed that the CNTs were embedded in the ZnO films. The field electron emission was observed from selectively-etched CNT/ZnO composite films.
Effect of Substrate Surface Finish and Proximity Distance on Compositional Shift of InGaAsP Metal–Organic Vapor Phase Epitaxy in a High-Speed-Rotation Multiple-Substrate Reactor
Authors: Shimizu Eiichi , Momoi Hajime
Published: August 2011

Shift of photoluminescence (PL) wavelengths toward shorter wavelengths (blue shift) in a specific area of InGaAsP quaternary epitaxial layers, grown in a high-speed rotating-disk type metal–organic vapor phase epitaxy (MOVPE) reactor, was found to be a deteriorative factor of PL wavelength uniformity in the epitaxial layers. Experiments were performed to generate a blue shift of PL wavelength, with two mirror-polished substrates placed in adjacent positions in the wafer carrier. Analysis of compositional distribution over 61 points was performed in InGaAsP/InP epitaxial layers with band gap corresponding to the 1310 nm PL wavelength. From this analysis, it was found that the blue shift of PL wavelength was dependent on the compositional shift of group V elements. In addition, the effect of substrate surface finish (mirror-polished or as-etched) was found to be a major cause of the compositional shift of group V elements. We found that, as the proximity distance between adjacent substrates was increased, there existed a critical proximity distance at which the blue shift disappeared.
Three-to-One Dimensional Crossover of Growth Mode in Transition Metal Cyanide Film
Authors: Moritomo Yutaka , Ito Mitsuhiro , Shibata Takayuki
Published: August 2011

A thin film of a transition metal cyanide is a promising positive electrode material for a Li ion secondary battery. Here, we investigated the surface morphologies of Na1.60Co[Fe(CN)6]0.902.9H2O by atomic force microscopy (AFM) and scanning electron microscopy (SEM) against film thickness (t). We observed a crossover behavior of the growth mode from the three-dimensional (3D) type to the one-dimensional (1D) type at the threshold thickness (t
th ≈250 nm). We found that the growth mode is governed by the intradomain grain coverage (γD), not by the conventional surface coverage (γ).
Experimental Investigation of Breakdown Voltage and Electrical Breakdown Time Delay of Commercial Gas Discharge Tubes
Authors: Pejović Milić Momčilo , Pejović Momčilo Milić , Stanković Koviljka
Published: August 2011

This article presents the experimental results of DC dynamic breakdown voltage U
b for small voltage increase rates and electrical breakdown time delay t
d of commercial gas discharge tubes. It was shown that U
b is a stochastic value with Gauss distribution for voltage increase rates ≥2 V/s. In order to determine the static breakdown voltage U
s as a deterministic quantity, the mean values of the dynamic breakdown voltage U
b as a function of voltage increase rate k were extrapolated until the intersection with U
b axis using linear fit. The intersection point (for k = 0) correspond to U
s value. Additional experiments were performed in order to verify the temperature stability of these components over the wide temperature range from 25 to 250 °C. The experimental results of electrical breakdown time delay are also presented in the paper. Electrical breakdown time delay if often refereed as delay response and it is also very important parameter of gas filled devices. It was shown when the voltage higher then 310 V is applied to those components, the mean value of electrical breakdown time delay t
d insignificantly varies to the value of relaxation time τ≈1 s, while the breakdown probability is close to one for the voltages higher then 380 V. These facts show that the commercial gas discharge tubes are very reliable for the protection for voltages higher then 380 V.
Novel System for Potential Nondestructive Material Inspection Using Positron Annihilation Lifetime Spectroscopy
Authors: Yamawaki Masato , Kobayashi Yoshinori , Hattori Kanehisa , Watanabe Yoshihiro
Published: August 2011

A new positron annihilation lifetime spectrometer consisting of a start γ-ray detector, a stop γ-ray detector, a digital oscilloscope, and a positron detector, which is a plastic scintillator coupled to a photomultiplier tube, is described. A 22Na source is placed between the positron detector and a sample to be studied. γ-ray signals related to positrons annihilating in the positron detector are rejected by anti-coincidence processing. Comparison of the positron lifetime spectrum of a steel strip collected with the new system with that collected with a conventional system using two specimens sandwiching the 22Na source shows that accurate positron lifetime measurements are possible with the new system. The new system does not require cutting of the samples and is potentially applicable to truly nondestructive onsite inspection of various materials such as those used in nuclear power plants, aircraft and cars, etc., by positron annihilation lifetime spectroscopy (PALS).
Etch Damage of Ge2Sb2Te5for Different Halogen Gases
Authors: Kang Se-Koo , Jeon Min-Hwan , Park Jong-Yoon , Jhon Myung S. , Yeom Geun-Young
Published: August 2011

Etch damage of Ge2Sb2Te5(GST) has been investigated after etching in halogen inductively coupled plasmas (ICPs) such as CF4, Cl2, and HBr. X-ray photoelectron spectra of Ge, Sb, and Te on the etched surfaces showed different depths of etch damage depending on the halogen-based plasmas. The blank GST etched by CF4showed a lower total-halogen-percentage remaining on the etched surface than that etched by Cl2even though the depth of halogenations was the deepest for the GST etched by CF4owing to the highest reactivity. However, when a GST feature masked by SiO2/Ti/TiN was etched, owing to the reaction of O from the SiO2mask and C from CF4, a thinner/or no C–F polymer appeared to be formed on the etched sidewall; therefore, the highest halogenation was observed on the GST etched by CF4. Among the halogen-gases investigated, HBr showed the lowest damage due to the lowest reactivity.
Deflections of Magnetic Actuators with Different Widths of Microcantilevers
Authors: Hsieh Yi-Ping , Wei Zung-Hang , Yip Ming-Chuen
Published: August 2011

Two magnetic actuators with different widths of microcantilevers are fabricated using electron beam lithography and electron beam evaporation and placed in various magnetic fields to observe the discrepancy between their flexures. One magnetic actuator of a 76×0.75×0.3 µm3 silicon oxide microcantilever and a 75×9×0.3 µm3 silicon oxide plate deposited on a 60×1×0.09 µm3 ferromagnetic thin film; the other of a 76×0.85×0.3 µm3 silicon oxide microcantilever and a 75×9×0.3 µm3 silicon oxide plate deposited on a 60×1×0.09 µm3 ferromagnetic thin film. The magnetic actuator is bent by magnetic torque produced by the ferromagnetic thin film under an external magnetic field owing to the fabrication of a highly sensitive microcantilever and the design of a high magnetic shape anisotropy. In this study, we prove the effect of the width of the microcantilever by the deflection of the magnetic actuator. The deflection of the magnetic actuator can be forecasted, when the magnetic actuator is used for gripping a cell.
Analysis of Size Dependence of Quality Factor of Quartz-Crystal Tuning Fork
Authors: Itoh Hideaki , Seki Tatsuya
Published: August 2011

We derived an approximate formula for the quality factor (Q value or Q) of a quartz-crystal tuning fork by applying the approximate calculation method developed by Landau et al. and Lifshitz et al. to the thermoelastic coupling equations previously obtained from the viewpoint of the thermoelasticity for a cantilever beam. We found that our calculated Q obtained using the approximate formula is half of the measured Q for an etching-processed quartz-crystal tuning fork. Furthermore, we derived the equation of the size dependence of Q by further approximating the approximate formula for Q at a constant frequency and various frequencies. The predicted size dependence of Q from these obtained equations is confirmed by measuring the Q of seven commercially available quartz-crystal tuning forks. The equations, which show the size dependence of Q, and the approximate formula for Q obtained here are effective for explaining the decreases in Q of the miniaturized quartz-crystal tuning fork.
Lead-Free Low-Melting and Semiconductive Vanadate Glass Applicable to Low-Temperature Sealing
Authors: Naito Takashi , Aoyagi Takuya , Sawai Yuichi , Tachizono Shinichi , Yoshimura Kei , Hashiba Yuji , Yoshimoto Mamoru
Published: August 2011

We optimized the fundamental composition and additives in a semiconducting V2O5–P2O5–TeO2 glass system to develop lead-free low-melting glass suitable for low-temperature sealing below 400 °C. Glass with a composition of 55.7V2O5–19.8P2O5–23.5TeO2 (mol %) has a low glass transformation temperature (T
g < 300 °C) as well as hard crystallization, and it is desired as a low-temperature sealing material. The effects of adding BaO, Sb2O3, MnO2, or Fe2O3 to the fundamental composition of 55.7V2O5–19.8P2O5–23.5TeO2 (mol %) on the thermal properties and water-vapor resistance were then characterized. Adding 11.7 mol % Fe2O3 improved the water-vapor resistance drastically and decreased the thermal expansion coefficient without increasing T
g. Sealing at 360 °C with our lead-free Fe2O3-added vanadate glass enabled practical airtight packaging on an electronic device.
Preparation of Thin Crystals of FeTe1-xSx Using the Scotch-Tape Method
Authors: Mizuguchi Yoshikazu , Watanabe Tohru , Okazaki Hiroyuki , Yamaguchi Takahide , Takano Yoshihiko , Miura Osuke
Published: August 2011

We have investigated an applicability of the scotch-tape method to fabricating thin crystals of Fe chalcogenide FeTe1-x
S
x
. Thin crystals with a typical thickness of 40 nm were expectedly left on a Si substrate. Thin films prepared using this process will develop both detailed studies on intrinsic nature of Fe-based superconductivity and application to superconducting devices.
Fabrication and Properties of Indium Tin Oxide/ZnO Schottky Photodiode with Hydrogen Peroxide Treatment
Authors: Lee Hsin-Yen , Su Chun-Tsung , Wu Bin-Kun , Xu Wei-Lun , Lin Yu-Jui , Chern Ming-Yau
Published: August 2011

A transparent, efficient ZnO ultraviolet Schottky detector with indium tin oxide (ITO) as a metallic contact layer is fabricated on ITO-coated glass substrates by cw CO2 laser evaporation. The device behavior changes from near ohmic to Schottky in the current–voltage characteristics after hydrogen peroxide treatment on the ZnO surface with a fitted barrier height of 1.16 eV, an ideality factor of 2.31, and a leakage current of 3.1×10-7 A at -3 V bias. Photoluminescence (PL) data show the effect of hydrogen peroxide, and indicate that the surface defects are removed, and better diode characteristics are shown.
Feather-Like Structures in Positive Streamers Interpreted as Electron Avalanches
Authors: Wormeester Gideon , Nijdam Sander , Ebert Ute
Published: August 2011

In experiments positive streamers can have a feather-like structure, with small hairs connected to the main streamer channel. These feathers were observed in pure nitrogen (with impurities of 1 ppm oxygen or less) but not in air. We hypothesize that these hairs are individual electron avalanches moving towards the streamer channel. Based on results of numerical simulations, we provide a theoretical explanation why these hairs are visible in nitrogen, but not in air.