Nanorods of ZnO containing various hollow structures were grown by using a thermal evaporation–deposition method with a mixture of ZnS and SnO2 powders as precursors. Transmission electron microscopy revealed rods with rows of voids as well as rods with empty channels along the growth axis. The presence of Sn nanoprecipitates associated with the empty regions indicated, in addition, that these were generated by diffusion processes during growth, probably due to an inhomogeneous distribution of Sn. The mechanism of forming voids and precipitates appeared to be based on diffusion processes similar to the Kirkendall effect, which could lead to void formation at interfaces of bulk materials or in core–shell nanostructures. In some cases the nanorods were ZnO tubes partially filled with Sn that was found to melt and expand by heating the nanotubes under the microscope electron beam. Such metal–semiconductor nanostructures had potential applications as thermal nanosensors or as electrical nanocomponents.

Voids, Nanochannels and Formation of Nanotubes with Mobile Sn Fillings in Sn Doped ZnO Nanorods. Y.Ortega, C.Dieker, W.Jäger, J.Piqueras, P.Fernández: Nanotechnology, 2010, 21[22], 225604