Annealing behaviors of SnO2–ZnO coaxial nanowires

SnO2-core/ZnO-shell nanorods were prepared by using a two-step process comprising the thermal evaporation of Sn powders and the sputter-deposition of ZnO. It appeared that the shells were crystallized by annealing. Photoluminescence measurements showed that the orange emission of the SnO2 nanorods was enhanced in intensity by sheathing them with ZnO and further enhanced by annealing them. A reducing atmosphere was more efficient in enhancing the orange emission by annealing than an oxidative atmosphere. The emission enhancement was mainly attributed to the increase in the Sn interstitial concentration in the SnO2 cores during the annealing process in a reducing atmosphere.