Biaxial ZnO-ZnS Nanoribbon Heterostructures

Biaxial ZnO-ZnS heterostructure nanoribbons (NRs) have been synthesized using the vapor-liquid-solid technique by the thermal evaporation of ZnS powder in the presence of a Au nanoparticles catalyst, a limited supply of oxygen and an inert carrier gas under controlled temperature and pressure. High resolution transmission electron microscopy (HRTEM) reveals that the nanoribbon is composed of two biaxially grown nanoribbons of single crystal (wurtzite) of ZnS and ZnO with widths of 10-100 and 20-500 nm, respectively, with an Au nanoparticle tip but no clearly detectable defects. The interfacial region is smooth and narrow (similar to 10 nm for a wire of several 100 nm wide). It is proposed that a composite was first formed via single catalyst confined growth; that is, while ZnS grows vertically via precipitation from the saturated solution in Au, the ZnO component on the surface of the ZnS subsequently served as the substrate for laterally growth forming ZnO nanoribbon. The implication of this technique for the synthesis of other composite nanostructures is noted.