Materials Science Forum Vols. 663-665

Abstract: (200) grain-oriented 0.91Pb(Zn1/3Nb2/3)O3–0.09PbTiO3 (PMN–0.09PT) piezoelectric ceramics with a degree of orientation of 0.5052 have been produced from melt by a directional solidification method. The dielectric, ferroelectric, and piezoelectric properties were investigated, e.g., ε~4200, tanδ~0.8%, d33~2100pC/N, kt~58%, and k33~90%, some of these values are comparable to those of ~PZN–PT single crystals. The strain–electric-field curve with a maximum strain of 0.49% at a field of 7kV/cm and well-saturated hysteresis loops with a Pr~32 mC/cm2 were recorded. The results demonstrate that the directional solidification method is a promising technique to fabricate high performance grain-oriented PZN–PT ceramics.

Abstract: The crosstalk is induced between the elements in digital circuits due the increasing switching speeds and the decreasing in technology scaling. The crosstalk is caused by parasitic couplings between adjacent wires that include capacitance and inductance effects. The crosstalk can result in functional failures or timing problems. A test approach for the delay faults caused by crosstalk interferences in digital circuits is presented in this paper, the approach is based on decision diagrams and the selection of delay sensitive path. The static timing analysis is carried out to obtain the delay information about the paths, all aggressor lines are activated in the best possible way. The test vectors are generated by building a decision diagram and searching for the specific paths in the decision diagram. Experimental results show that the test approach proposed in this paper can generate the test vectors for the testable delay faults caused by crosstalk.

Abstract: The limited sensitivity of thinfilm based sensors has motivated the search for sensing structures and materials with greater sensing performance. Although thinfilm based SAW devices have been used as force, pressure, chemical and gas sensors so far. It is limited by the exposed sensing surface of the thinfilm. A feasibility study has been done by implementing the ZnO nanorods (NRs) to enhance the device sensitivity by greatly increase the exposed sensing surface. The implementation of these ZnO NRs as sensing elements is expected to enhance the sensing power due to the large surface to volume ratio. The sensing mechanism in this design is by detecting the minute change of seismic mass for ZnO NRs using surface acoustic wave before and after the attachment of reacting chemical liquid and gas substance.

Abstract: Activated carbon was fabricated by using phenolic resin as carbon source, tween-80 as organic template, KOH as activator. The samples were analyzed by N2 adsorption, scanning electron microscopy (SEM). Cyclic voltammetry and galvanostatic charge-discharge were used to characterize the electrochemical performance of the samples. The results showed that specific surface area of the prepared sample was 1935.99 m2/g, pore size was mainly in the range of 1.0～4.0 nm and showed typical capacitance characteristics in cyclic voltammetry. At a current density of 15mA/cm2, a specific capacitance of 246.18F/g was achieved and the resistance was 1.11Ω. Supercapacitors based on the sample had low ESR and excellent power property.

Abstract: Ti-Ga co-doped ZnO thin films (TGZO) have been successfully prepared on glass substrates by DC magnetron sputtering at room temperature. The X-ray diffraction (XRD) patterns show that all the deposited films are polycrystalline with a hexagonal structure and have a preferred orientation along the c-axis perpendicular to the substrate. The distance between target and substrate was varied from 41 to 75 mm. The crystallinity increases obviously and the electrical resistivity decreases when the distance between target and substrate decreases from 75 to 46 mm. However, as the distance decreases further, the electrical resistivity increases. It is obtained that the lowest resistivity is 2.0610-4cm when the distance between target and substrate is 46 mm. In the visible region, the TGZO films show a high average transmittance of above 90 %.

Abstract: The magnet-optical films of TbFeCo and Ag/TbFeCo were prepared on the Si substrates by magnetron sputtering. The spectra of Kerr ellipticity and Kerr rotation were measured at room temperature and the remarkable enhancement of Kerr effect was observed at short wavelength. The enhancement of Kerr effect is not caused by the interference between layers, but the resonance-like peak due to the presence of the plasma absorbing edge of Ag. The thickness of Ag layer has important influence on the enhancement of Kerr effect and the enhancement of Kerr effect will be disappeared as Ag layer is over than 50 nm.

Abstract: YFeO3 single crystal, as a novel magneto-optical material, has attracted much attention due to its remarkable properties of primary significance for technological applications. In this work, YFeO3 crystal was successfully grown by optical floating zone method. Some voids are observed in the polished surface. The voids are effectively decreased by denser feed rod. In the etching samples, hexagonal etch patterns, sub-grain boundary and concentric growth striations were observed by optical microscope and SEM. The formation mechanism of these defects was discussed, and effective measures to restrain these defects were also proposed.

Abstract: Excellent dielectric property and amazing X-ray Diffraction spectra were found for the novel polyimide films by composing SiO2 hollow spheres with different wt%. The dielectric constants of that from different dianhydrides were ranged of 1.9-3.1 at 1MHz. It was sure that the dielectric constants of the films could be tunable in wider range with different wt% SiO2 hollow sphere as well as different dianhydrides. And in the X-ray Diffraction spectra, some films not only presented wide diffractive peaks of amorphous structures, but also showed sharp crystal peaks at 58.7o and 28.4o. And the Intensity of the sharp crystal peak was dramatically related with the value of dielectric constants. It might be caused by the ordered structure in part of polymer chain. And the structures and properties of the composite thin films were also measured with scanning electron microscope and dynamic themomechanical analysis et al.

Abstract: Based on nonequilibrium Green’s function and first-principles calculation, we investigate the electronic transport of borazine molecule with different metal-molecule interface conformations, namely bridge and top site. The motivation is the variable situations that may arise in break junction experiments. Numerical results show that the current will be increased with the different adsorption sites; especially the enhancement of current is more obvious when molecule is located at the bridge site. Furthermore, a negative differential resistance under applied bias can be observed when the molecule is located at the top site. The mechanism of negative differential resistance is mainly induced by the resonance peak around the Fermi energy in top adsorption site.

Abstract: The electronic structure and optical properties of Fe1-xCoxSi2 have been studied using the first principle plane-wave pseudo-potential based on the density function theory. Substitutional doping is considered with Co concentrations of x=0.0625, 0.125, 0.1875 and 0.25, respectively. The calculated results show that the volume of β-FeSi2 increase and the band gap decrease with increasing of Co.