No abstract available

[en] In this study, we examined the effect of etching on the electrical properties, transmittance, and scattering of visible light in molybdenum doped zinc oxide, ZnO:Mo (MZO) thin films prepared by pulsed direct current magnetron sputtering. We used two different etching solutions - KOH and HCl - to alter the surface texture of the MZO thin film so that it could trap light. The experimental results showed that an MZO film with a minimum resistivity of about 8.9 x 10^-4 Ω cm and visible light transitivity of greater than 80% can be obtained without heating at a Mo content of 1.77 wt.%, sputtering power of 100 W, working pressure of 0.4 Pa, pulsed frequency of 10 kHz, and film thickness of 500 nm. To consider the effect of resistivity and optical diffuse transmittance, we performed etching of an 800 nm thick MZO thin film with 0.5 wt.% HCl for 3-6 s at 300 K. Consequently, we obtained a resistivity of 1.74-2.75 x 10^-3 Ω cm, total transmittance at visible light of 67%-73%, diffuse transmittance at visible light of 25.1%-28.4%, haze value of 0.34-0.42, and thin film surface crater diameters of 220-350 nm.

[en] We present electrical, magnetic and crystal structure for a series of La_1.2(Sr_1.8-xCa_x)Mn₂O₇ (x=0-0.8) manganites. The sample of x=0.4 exhibits the highest magnetoresistance (MR) ratio [ρ(H)-ρ(0)/ρ(H)]x100% of -108% at the temperature of 102 K. The Curie temperature (T_C) decreases from 135 K for x=0-102 K for x=0.4. The hysteresis phenomenon was observed when the temperatures were lower than the magnetic transition temperature. The static strain within the compound for x=0.4 has also been found by high-resolution transmission electron microscopic techniques

[en] We report the unusual photoluminescence (PL) properties of vertically aligned InN nanorod arrays grown on Si(111) with a Si₃N₄ buffer layer. The optimum growth conditions of InN nanorods are obtained by controlling the III/V ratio and the growth temperature. Structural characterization by X-ray diffraction and scanning electron microscopy indicates that individual nanorods are wurtzite InN single crystals with the growth direction along the c-axis. Near-infrared PL from InN nanorods is clearly observed at room temperature. However, in comparison to the PL from InN epitaxial films, the PL from InN nanorods is significantly lower in efficiency and exhibit anomalous temperature dependence. We propose that these unusual PL properties are results of considerable structural disorder (especially for the low-temperature grown InN nanorods) and strong surface electron accumulation effect. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

[en] N,N,N',N'-Tetrabutyladipicamide (TBAA) was used for the extraction of nitric acid and uranyl(II) ion from nitric acid media into toluene. The effects of nitric acid, uranyl(II) ion, and extractant concentration, temperature and back extraction on the distribution coefficient of uranyl(II) ion have been studied. The main adduct of TBAA and HNO₃ is TBAA-HNO₃ in 1.0 mol/l nitric acid solution. The 1:2:2 complex of uranyl(II) ion, nitrate ion and TBAA as extracted species is further confirmed by IR spectra of the extraction of uranyl(II) ion with TBAA. The values of the thermodynamic parameters have also been calculated. (author)

[en] The effect of doping Cr in the Mn site of the La_1.2Sr_1.8Mn₂O₇ system has been studied. Addition of Cr modifies the transport and magnetic properties of the parent phase. With increasing Cr, the insulator-metal transition observed in the parent phase is suppressed and insulating behaviour is induced. In the range of doping studied (25%), the compositions show ferromagnetic behaviour with the Curie temperature decreasing with increasing Cr. The unit cell volume also shows a decrease. However, the magnetoresistance ratio is not significantly affected. We compare these results with an earlier study of doping Cr in the three-dimensional LaMnO₃ structure, where it was seen that the ferromagnetic and magnetoresistance characteristics are sensitive to Cr doping. The results of the present study suggest that the layered manganates are more accommodative to doping compared to the three-dimensional perovskites. (author)

[en] Hexagonal to cubic phase transformation is studied in focused ion beam assisted Ga⁺-implanted GaN nanowires. Optical photoluminescence and cathodoluminescence studies along with high-resolution transmission electron microscopic structural studies are performed to confirm the phase transformation. In one possibility, sufficient accumulation of Ga from the implanted source might have reduced the surface energy and simultaneously stabilized the cubic phase. Another potential reason may be that the fluctuations in the short-range order induced by enhanced dynamic annealing (defect annihilation) with the irradiation process stabilize the cubic phase and cause the phase transformation

[en] Transparent conducting oxide thin films are used as front contact material for dye-sensitized solar cells. This study investigated the effects of chromium (Cr) and vanadium (V) contents on the chemical and heat stability properties of aluminum-doped zinc oxide (AZO) thin films using pulsed direct current magnetic sputtering on Corning 1737F glass substrates. The experimental results show that Cr and V doping is useful for improving the chemical and thermal stability of AZO films. The energy gap for AZO thin films is between 3.65 and 3.69 eV. The resistivity of the AZO:Cr:V thin film was 4.23 x 10^-4 Ω cm at a Cr/V ratio of 0.30/0.23 wt.%, deposition power of 150 W, working distance of 5.5 cm, substrate temperature of 473 K, working pressure of 0.4 Pa, and frequency of 10 kHz. This value is lesser than (and therefore superior to) the resistivity of SnO₂:F (FTO) films (6.5 x 10^-4 Ω cm), but greater than that of SnO₂:In (ITO) thin films (1.2 x 10^-4 Ω cm). The resistivity increased by about 0.27% after electrolyte etching, which is similar to the 0.16% increase observed for the ITO thin film. After a thermal cycle test at 673 K, the resistivity of the AZO:Cr:V film increased to 5.42 x 10^-4 Ω cm, which is better than the resistivity of the ITO and FTO films after the same thermal cycle.

[en] Effects of proton irradiation on the optical and electrical properties of n-InN with charge carrier concentrations of 2-5 x 10¹⁸ cm^-3 have been investigated. Strong changes in photoluminescence spectra and electrical parameters of irradiated n-InN are discussed. Proton irradiation of n-InN results in the appearance of shallow donors in large concentrations. Comparison with the effects observed on heavily degenerate n-InN after proton irradiation leads to the conclusion that these irradiation-produced donors are native defects, most likely vacancies on the nitrogen sublattice. (Abstract Copyright [2007], Wiley Periodicals, Inc.)

[en] LiCoO₂ was coated with ZrO₂ by using an impregnation method followed by a calcination process at 550 ^oC for 8 h. X-ray absorption near-edge spectrum (XANES) and X-ray diffraction (XRD) investigations showed that the structure of LiCoO₂ did not alter by ZrO₂ coating. Cyclic voltammogram indicated that the coating film ZrO₂ exerted influences on transporting of Li⁺ ions. From electrochemical tests, in the voltage range of 3.00-4.25 V, the coated LiCoO₂ shows enhanced electrochemical properties over bare LiCoO₂ at both elevated temperature and room temperature.