Surface charge dynamics on ferroelectric PbZr0.48Ti0.52O3 films responding to the switching bias of electric force microscope

We investigated the role of surface charges in writing and reading ferroelectric bits on an epitaxial PbZr0.48Ti0.52O3 thin film by electric force microscopy (EFM). The sign of EFM surface potential was reversed within several hundred microseconds for 10 V. For a negative bias voltage of -10 V, EFM surface potential was reversed in several milliseconds. The different time scales of the EFM surface potential reversals originate from the screening of the ferroelectric polarization charges by the surface charges which pass over two different Schottky barriers depending on the applied bias polarity.X118sciescopu

Nitride mediated epitaxy of CoSi2 through self-interlayer-formation of plasma-enhanced atomic layer deposition Co

The silicide formation by annealing plasma-enhanced atomic layer deposition (PE-ALD) Co and physical vapor deposition (PVD) Co was comparatively studied. Very pure Co films were deposited by PE-ALD with CoCp2 and NH3 plasma. However, various analyses have shown that amorphous SiNx interlayer was formed between PE-ALD Co and Si due to the NH3 plasma exposure in contrast with PVD Co. Due to the nitride interlayer, CoSi2 was epitaxially grown from PE-ALD Co by rapid thermal annealing through nitride mediated epitaxy. This process scheme is expected to provide a simple route for contact formation in future nanoscale devices. (c) 2007 American Institute of Physics.open112221sciescopu

Synthesis of horizontally aligned ZnO nanowires localized at terrace edges and application for high sensitivity gas sensor

We developed step edge decoration method for the fabrication of semiconductor ZnO nanodots and nanowires using pulsed laser deposition. We synthesized high quality ZnO nanowires with the small diameter of about 20 nm and the uniform interval of about 80 nm between each nanowire, which has a simple structure for the formation of contact electrodes. The ZnO nanowire-based sensor was prepared only with the simple process of a gold electrode formation. The ZnO nanowire-based sensor exhibited the high surface-to-volume ratio of 58.6 mu m(-1) and the significantly high sensitivity of about 10 even for the low ethanol concentration of 0.2 ppm.open115860sciescopu

Plasma-Enhanced ALD of TiO2 Thin Films on SUS 304 Stainless Steel for Photocatalytic Application

Plasma-enhanced atomic layer deposition (PE-ALD) of TiO2 thin films using Ti(NMe2)(4) [tetrakis(dimethylamido) Ti] and O-2 plasma were prepared on stainless steel to show the self-cleaning effect. The TiO2 thin films deposited on stainless steel have high growth rate, large surface roughness, and low impurities. The film deposited below 200 degrees C was amorphous, while the films deposited at 300 and 400 degrees C showed anatase and rutile phases, respectively. The contact angle measurements on crystalline PE-ALD TiO2 thin films exhibited superhydrophilicity after UV irradiation. The TiO2 thin film with anatase phase deposited at 300 degrees C showed the highest photocatalytic efficiency, which is higher than on Activ glass or thermal ALD TiO2 films. We suggest that anatase structure and large surface area of TiO2 thin film on stainless steel are the main factors for the high photocatalytic efficiency. (C) 2009 The Electrochemical Society. [DOI: 10.1149/1.3095515] All rights reserved.X117sciescopu

Effects of Fluorine Plasma Treatment on the Electronic Structure of Plasma-Enhanced Atomic Layer Deposition HfO2

We investigated the effects of fluorine treatments on the electrical properties and electronic structures of plasma-enhanced atomic layer deposition HfO2 gate oxides, depending on the treatment process. Pre- and postoxide-deposition fluorine treatments were carried out using CF4 plasma. Improved dielectric properties were achieved by predeposition treatment, while degradation of electrical properties was observed for postdeposition treatment. Based on the electronic structure analysis using X-ray photoemission spectroscopy and near-edge X-ray absorption fine structures, we found that the enhanced dielectric properties of the pretreated HfO2 are induced by the defect passivation and conduction-band offset increase. (C) 2009 The Electrochemical Society. [DOI: 10.1149/1.3089976] All rights reserved.open111010sciescopu

Ferroelectric polarization switching with a remarkably high activation energy in orthorhombic GaFeO3 thin films

Orthorhombic GaFeO3 (o-GFO) with the polar Pna2(1) space group is a prominent ferrite owing to its piezoelectricity and ferrimagnetism, coupled with magnetoelectric effects. Herein, we demonstrate large ferroelectric remanent polarization in undoped o-GFO thin films by adopting either a hexagonal strontium titanate (STO) or a cubic yttrium-stabilized zirconia (YSZ) substrate. The polarization-electric-field hysteresis curves of the polar c-axis-grown o-GFO film on a SrRuO3/STO substrate show the net switching polarization of similar to 35 mu C cm(-2) with an unusually high coercive field (E-c) of +/- 1400 kV cm(-1) at room temperature. The positive-up and negative-down measurement also demonstrates the switching polarization of similar to 26 mu C cm(-2). The activation energy for the polarization switching, as obtained by density-functional theory calculations, is remarkably high, 1.05 eV per formula unit. We have theoretically shown that this high value accounts for the extraordinary high E-c and the stability of the polar Pna2(1) phase over a wide range of temperatures up to 1368 K.111714Ysciescopu

A new modelling approach of evaluating preventive and reactive strategies for mitigating supply chain risks

Supply chains are becoming more complex and vulnerable due to globalization and interdependency between different risks. Existing studies have focused on identifying different preventive and reactive strategies for mitigating supply chain risks and advocating the need for adopting specific strategy under a particular situation. However, current research has not addressed the issue of evaluating an optimal mix of preventive and reactive strategies taking into account their relative costs and benefits within the supply network setting of interconnected firms and organizations. We propose a new modelling approach of evaluating different combinations of such strategies using Bayesian belief networks. This technique helps in determining an optimal solution on the basis of maximum improvement in the network expected loss. We have demonstrated our approach through a simulation study and discussed practical and managerial implications

Comparison and Mapping Facilitate Relation Discovery and Predication

Relational concepts play a central role in human perception and cognition, but little is known about how they are acquired. For example, how do we come to understand that physical force is a higher-order multiplicative relation between mass and acceleration, or that two circles are the same-shape in the same way that two squares are? A recent model of relational learning, DORA (Discovery of Relations by Analogy; Doumas, Hummel & Sandhofer, 2008), predicts that comparison and analogical mapping play a central role in the discovery and predication of novel higher-order relations. We report two experiments testing and confirming this prediction

The effect of localized surface plasmon resonance on the emission color change in organic light emitting diodes

Three primary colors, cyan, yellow, and green, are obtained from Ag nano-dot embedded organic light emitting diodes (OLEDs) by localized surface plasmon resonance (LSPR). By changing the thickness of the Ag film, the size and spacing of Ag nano-dots are controlled. The generated light from the emissive layer in the OLEDs interacts with the free electrons near the surface of the Ag nano-dots, which leads to LSPR absorption and scattering. The UV-visible absorption spectra of glass/ITO/Ag nano-dot samples show intense peaks from 430 nm to 520 nm with an increase of Ag nano-dot size. And also, the Rayleigh scattering spectra results show the plasmon resonance wavelength in the range of 470-550 nm. The effect of the LSPR of Ag nano-dots on the change of emission color in OLEDs is demonstrated using 2 dimensional finite-difference time-domain simulations. The intensity of the electro-magnetic field in the sample with 5 nm-thick Ag is low at the incident wavelength of 500 nm, but it increases with the incident wavelength. This provides evidence that the emission color change in OLEDs originates from LSPR at the Ag nano-dots. As a result, the emission peak wavelength of OLEDs shifted toward longer wavelengths, from cyan to yellow-green, with the increase of Ag nano-dot size.open11107Nsciescopu