Structure and thermal stability of ZnO-TiO₂ core-shell nanowires

ZnO-TiO₂ core-shell nanowires were prepared by a thermal reduction method and an atomic layer deposition (ALD) technique. The effects of deposition thickness, deposition temperature and annealing on crystallization and structure of ZnO-TiO₂ core-shell nanowires were studied. ZnO-TiO₂ core-shell nanowires were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM). The results show that TiO₂ shell is transformed from amorphous to crystallization with the increasing of the deposition thickness and deposition temperature. After 500℃ annealing, the crystallinity of TiO₂ shell is improved, but wavy deformation is observed in the fine core-shell nanowires (the diameter of ZnO nanowires < 80 nm). As for amorphous TiO₂ shell deposited at 150℃ after 500℃ annealing, convex grains are formed on the TiO₂ shell and the loss of ZnO appears at the ZnO-TiO₂ interface.