Interface and defect structures in ZnO films on m-plane sapphire substrates

Abstract

Interface and defect structures in Zno films grown on (1 0 (1) over bar 0) m-plane sapphire substrates by plasma-assisted molecular beam epitaxy were investigated by transmission electron microscopy (TEM). Distribution of misfit dislocations (MDs) at the ZnO/Al(2)O(3) interfaces was orientation dependent and quite anisotropic. In addition, type-I(1) stacking faults (SFs) bounded by the Frank dislocations with the Burgers vector of 1/6[2 0 (2) over bar 3] were observed to be predominant. Many SFs initiated from the interface to the film surface were observed in addition to the MDs at the interface. The analysis of the high-resolution TEM revealed no correlation between the SFs and the MDs. The ZnO films were not found to be pure m-plane ZnO and (1 0 (1) over bar 3) domains were frequently observed in the film with otherwise mostly (1 0 (1) over bar 0) m-plane in nature. These (1 0 (1) over bar 3) domains were not nucleated at the interface but initiated inside the ZnO film above the interface and reached the top surface. (C) 2009 Elsevier B.V. All rights reserved.