Papers by Keyword: Semiconducting Oxide

Abstract: The approach for converting nanoscale mechanical energy into electrical energy using piezoelectric nanowire arrays has been shown by a deflection of the nanowires via a corrugated electrode operated up and down by ultrasounds. I have performed an analytical method for describing the most important quantities concerning transport phenomena; it predicts very high initial diffusion of charge. This behaviour appears via mechanical external device stresses, which assumes therefore the typical characteristics of a nanosensor. With this method it is possible to deduce interesting informations about the device sensitivity, focusing on the important correlation between sensitivity and high initial diffusivity of these materials at nanometric state.

Abstract: A key factor for the efficiency in nanostructured devices is charge transport. Despite considerable attention to this subject, the precise nature of transport processes in these systems has remained unresolved. To understand the microscopic aspects of carrier dynamics, we suggest a method for the calculation of correlation functions. They can be expressed as the Fourier transform of a kernel containing the frequency-dependent conductivity (). We present results for the velocity correlation functions , the mean square deviation of position R2 = <[R(t)-R(o)]2> and the diffusion coefficient D = (R2/t) in materials, like TiO2, ZnO, Si, for which a Drude-Lorentz description or its generalizations applies with a good agreement with experiments. We find that D = 0, indicating absence of diffusion at long times, except in the Drude case (o = 0). For small times t/ < 1, however, diffusion can occur even when o 0, within a limited region of size increasing with the value of o. The quantum mechanical extension of this method allows applications for the nanodiffusion in nanostructured, porous and cellular materials, as for biological, medical and nanopiezotronic devices.

Abstract: The morphology of wurtzite-type zinc oxide (ZnO) grown from an aqueous solution was successfully controlled by addition of phosphate ions and various organic molecules having carboxy groups. Basically, array of hexagonal needles with a diameter of 50–100 nm was grown on a substrate in the absence of the additives. Hexagonal plates were perpendicularly arranged on the substrate by the adsorption of citric, tartaric and maleic acids. The presence of phosphate ions induced an open cellular structures consisting of zinc oxide nanosheets. Densely packed columns and bundles consisting of nanoscale fibrous crystals were produced by the addition of bulky dye molecules, such as phenolphthalein. The influence of the dye molecules depended on pH of the solution. The morphological variation of ZnO films was ascribed to the selective adsorption of the anionic species on the basal and prism planes of the wurtzite structure.