Fine characterization of plasma‐polymerized films from a methane/air mixture

The plasma polymerization of methane/air mixtures was performed to produce a hydrophilic film on a substrate, and the obtained films were characterized with ellipsometry, elemental analysis, Fourier transform infrared spectroscopy, X‐ray photoelectron spectroscopy, atomic force microscopy, and contact‐angle measurements. Fourier transform infrared revealed that the structure of the plasma‐polymerized films changed with increasing film thickness; that is, an increase in the film thickness led to an increase in the absorbance ratio of the carbonyl band at 1664 cm^?1 to the methyl band at 1385 cm^?1. Although the contents of nitrogen and oxygen measured by elemental analysis changed with the film thickness, the contact angle and X‐ray photoelectron spectroscopy atomic ratio of the films were independent of it. Nitrogen and oxygen were contained in the bulk more than on the surface of the films. Nitrogen and oxygen were copolymerized with methane, and the properties of the obtained films were similar to those of an amide compound. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3408–3414, 2006     

Visualization of high‐speed phenomena using an acousto‐optic laser deflector

An acousto‐optic laser deflector was used for visualization of high‐speed phenomena, such as shock waves and density perturbations accompanying an impulse discharge, or shock waves generated by laser‐induced breakdown in air. Using a continuous wave laser as the light source, shadowgraphs of shock waves and density perturbations were obtained at shutter speeds down to 1µs. Results showed that shock waves propagated at a speed of 417 m/s in the case of an impulse discharge, and 485 m/s in the case of laser‐induced breakdown. Prebreakdown phenomena such as leaders progressing from the high‐voltage electrode were also visualized. Compared to conventional high‐speed imaging techniques, this method is useful when using a laser light source, since the acousto‐optic crystal can accommodate high‐intensity laser light. © 2005 Wiley Periodicals, Inc. Electr Eng Jpn, 154(3): 9–15, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20279     

Electronic Structures and Device Applications of Transparent Oxide Semiconductors: What Is the Real Merit of Oxide Semiconductors?

The main objective of this review is to provide an idea how to create new functions in oxides and how to find suitable applications only oxides can realize. Oxides have crystal and electronic structures largely different from those of conventional semiconductors such as Si and GaAs. Therefore, we should design suitable applications according to the inherent properties of oxide semiconductors if we intend to develop practical optoelectronic devices using oxides. In this review, we first briefly describe the characteristic features of oxide semiconductors from the viewpoints of crystal and electronic structures. Then three materials and related device applications are shown as examples. N-type amorphous oxide semiconductors (AOSs) can have electron transport properties superior even to silicon if they are in amorphous states. We propose that AOSs are favorable materials for active layers in low-temperature thin film device technology and demonstrate high-performance thin film transistors fabricated at room temperature on flexible plastic sheets. The second example is transparent p-type semiconductors. Employing chalcogen orbitals and layered crystal structures, large hole mobilities, degenerate p-type conduction, and room-temperature stable excitions are rendered in wide bangap materials. Room-temperature operation of excitonic blue light-emitting diodes was thereby demonstrated. The last is 12CaO·7Al₂O₃ in which the use of subnanometer-sized cages and anions clathrated in the cages creates many chemical, optical, and electronic functions.     

Electrical Properties and Structure of p‐Type Amorphous Oxide Semiconductor xZnO·Rh2O3

p‐Type conduction in amorphous oxide was firstly found in zinc rhodium oxide (ZnO·Rh₂O₃) (Adv. Mater. 2003 , 15, 1409), and it is still the only p‐type amorphous oxide to date. It was reported that an ordered structure at the nanometer scale was contained and its electronic structure is not clear yet. In this paper, optoelectronic and structural properties are reported in detail for xZnO·Rh₂O₃ thin films (x = 0.5–2.0) in relation to the chemical composition x. All the films exhibit positive Seebeck coefficients, confirming p‐type conduction. Local network structure strongly depends on the chemical composition. Transmission electron microscopic observations reveal that lattice‐like structures made of edge‐sharing RhO₆ network exist in 2–3 nm sized grains for rhodium‐rich films (x = 0.5 and 1.0), while the zinc‐rich film (x = 2) is completely amorphous. This result indicates that excess Zn assists to form an amorphous network in the ZnO–Rh₂O₃ system since Zn ions tend to form corner‐sharing networks. The electronic structure of an all‐amorphous oxide p‐ZnO·Rh₂O₃/n‐InGaZnO₄ junction is discussed with reference to electrical characteristics and results of photoelectron emission measurements, suggesting that the p/n junction has large band offsets at the conduction and valence bands, respectively.     

Carrier Generation in Wide-Gap Conductor, Zinc Antimonate

Mechanisms for carrier generation in zinc antimonate (ZnSb₂O₆) with a wide band gap were examined in relation to its crystallinity. ZnSb₂O₆ prepared by the reaction of Sb₂O₅ sol and 3ZnCO₃·4Zn(OH)₂ was sintered at 893, 1173, and 1393 K, and characterized by X-ray diffraction (XRD), electrical conductivity and diffuse reflectance measurements. A higher conductivity was found for ZnSb₂O₆ sintered at lower temperatures. Rietveld analysis of XRD patterns showed that the cations in conductive ZnSb₂O₆ occupied irregular sites, similar to the random rutile structure. Electron carriers were also considered to be generated by oxygen vacancies in ZnSb₂O₆ samples which have a structure similar to the random rutile structure.     

Wide gap p-type degenerate semiconductor: Mg-doped LaCuOSe

Hole transport and optical properties were investigated on undoped and Mg-doped LaCuOS_1−xSe_x (x=0-1) epitaxial films. Both electrical conductivity and Hall mobility were found to increase monotonously with increasing Se content in the films. The increase in Hall mobility is considered to be associated with the increase in valence band dispersion. Mg ion doping increased hole concentrations in the undoped films by an order of magnitude to ∼2×10²⁰ cm⁻³, while Mg doping reduced mobility to merely half that of undoped films. The results suggest that hole scattering due to Mg impurity ions is suppressed by natural modulation doping originating from the layered structure of LaCuOS_1−xSe_x. Hole concentrations showed no temperature dependence, indicating degenerate conduction. The largest value for conductivity, 140 S cm⁻¹, was obtained with Mg-doped LaCuOSe epitaxial film. Accompanying characteristics included moderately high optical transparency in the visible region and blue photoluminescence.     

Large reversible Li storage of graphene nanosheet families for use in rechargeable lithium ion batteries

The lithium storage properties of graphene nanosheet (GNS) materials as high capacity anode materials for rechargeable lithium secondary batteries (LIB) were investigated. Graphite is a practical anode material used for LIB, because of its capability for reversible lithium ion intercalation in the layered crystals, and the structural similarities of GNS to graphite may provide another type of intercalation anode compound. While the accommodation of lithium in these layered compounds is influenced by the layer spacing between the graphene nanosheets, control of the intergraphene sheet distance through interacting molecules such as carbon nanotubes (CNT) or fullerenes (C60) might be crucial for enhancement of the storage capacity. The specific capacity of GNS was found to be 540 mAh/g, which is much larger than that of graphite, and this was increased up to 730 mAh/g and 784 mAh/g, respectively, by the incorporation of macromolecules of CNT and C60 to the GNS.     

Effects of High-Pressure Processing on the Cooking Loss and Gel Strength of Chicken Breast Actomyosin Containing Sodium Alginate

The effects of high-pressure processing (HPP) (0–400 MPa for 10 min) on the cooking loss (CL), gel strength, and thermal gelling mechanism of chicken breast actomyosin solution containing 0.5 % (w/v) sodium alginate (AS-SA) were investigated. The results showed that HPP could significantly increase (P?相似文献