Annealing induced solid-state structure dependent performance of ultraviolet photodetectors made from binary oxide-based nanocomposites

In this study, one-dimensional core–shell nanorods of ZnO–TiO2 (ZnO–TiO2 nanorods) were successfully prepared through the atomic layer deposition of amorphous TiO2 ultra-thin films onto ZnO nanorod templates. The subsequent postannealing procedures at 400–800 °C induced core–shell nanorods to transform into high quality crystalline wurtzite ZnO-anatase TiO2 and wurtzite ZnO-cubic Zn2TiO4 (ZnO–ZTO) nanorods. Structural analyses revealed that the surfaces of the ZnO–ZTO nanorods are more irregular and rougher than those of ZnO–TiO2 nanorods. Moreover, ZnO–ZTO nanorods have a higher oxygen vacancy size near the nanostructure surfaces because of a relatively high-temperature solid-state reaction. The surface electron depletion size is associated with the degree of nanorod crystal-imperfection defects, and this might affect the oxide nanorod ultraviolet photoresponse efficiency.