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A Si-capped Ge quantum dot sample was self-assembly grown via Stranski-Krastanov mode in a molecular beam epitaxy system with the Si capping layer deposited at 300 °C. After annealing the sample in an oxygen atmosphere at 1000 °C, a structure, namely two layers of quantum dots, was formed with the newly formed Ge-rich quantum dots embedded in the oxidized matrix with the position accurately located upon the as-grown quantum dots. It has been found that the formation of such nanostructures strongly depends upon the growth temperature and oxygen atmosphere. A growth mechanism was proposed to explain the formation of the nanostructure based on the Ge diffusion from the as-grown quantum dots, Ge segregation from the growing oxide, and subsequent migration/agglomeration. [ABSTRACT FROM AUTHOR]

Abstract: Amorphous SiOx nanowires, with diameters of ∼20nm and lengths of tens of μm, were grown from self-organized GeSi quantum dots or GeSi alloy epilayers on Si substrates. The morphologies and yield of these amorphous nanowires depend strongly upon the synthesis temperature. Comparative experiments indicate that the present SiOx nanowires are induced by metallic Ge as catalysts via the solid liquid solid growth mechanism. Two broad peaks centered at 410nm and 570nm were observed in photoluminescence spectrum, indicating that such SiOx nanowires have the potential applications in white light-emitting diodes, full-colour display, full-colour indicator and light sources. [Copyright &y& Elsevier]