Redox reaction-assisted growth of ZnO nanowires on SnO2 thin films

ZnO nanowires were grown onto SnO2 film coated on Si substrate using a vapor transport method. Zn vapor was found to play important roles in reducing SnO2 and in being oxidized as a ZnO layer. The growth mechanism of ZnO nanowires was revealed to be a two-step process of Zn–SnO2 redox reaction and Sn catalyzed V–L–S (vapor–liquid–solid) growth; initially, Zn vapor atoms arriving at the SnO2 surface reduce the SnO2 to Sn and O atoms and diffuse into the SnO2 layer to form a ZnO layer. The reduced Sn atoms diffuse out of the SnO2 layer and are agglomerated to form Sn liquid droplets. Then, the Sn droplets on the surface of ZnO layer serve as a catalyst for the catalytic V–L–S growth of ZnO nanowires.

► Redox growth of ZnO nanowires on SnO2 films.
► Reduction of SnO2 to Sn and O by Zn vapors.
► Oxidation of Zn to ZnO.
► Sn catalytic V–L–S growth of ZnO nanowires.