Effects of interface micro structure in crystallization of ZnO thin films prepared by radio frequency sputtering

Abstract

ZnO thin films have been formed by radio frequency sputtering on glass, Al, Au and R-cut sapphire substrates. Micro structures of ZnO/substrate interfaces have been observed by transmission electron microscope and the surface morphology of the substrates has been measured by atomic force microscope. An amorphous layer is observed at the ZnO/glass interface and also a thicker amorphous layer at the ZnO/Al interface. No amorphous layers are observed at ZnO/Au and ZnO/sapphire interfaces, and direct orientation of ZnO thin films begins at the interface of both substrates. These results clearly demonstrate that crystallization of ZnO thin films prepared by radio frequency sputtering is strongly influenced by the surface crystallinity and morphology of substrates. Epitaxially grown ZnO thin films are confirmed, both on R-cut sapphire and on Au, by cross section transmission electron microscope.