Interfacial structure of a-plane ZnO grown on r-plane sapphire by pulsed laser deposition

Abstract

In this study, interfacial structure of a-ZnO with misfit accommodation on r-sapphire at low and high growth temperatures (LT and HT) by pulsed laser deposition is presented. Along [1 (1) over bar 00](ZnO) of large lattice mismatch of ZnO with sapphire, TEM examinations show that a-type misfit dislocations are spaced 1.3-2.2 nm on HT-ZnO/sapphire interface, whereas dislocation pairs in spacing of 2.8-3.5 nm are observed for LT-ZnO/sapphire. For smaller lattice mismatch along the ZnO c-axis direction, reciprocal space maps of (11 (2) over bar(2) over bar)(ZnO) and (30 (3) over bar0)(sapphire) reflections show that HT-ZnO is nearly fully strained without much relaxation and has a highly coherent interface with sapphire, in contrast with partial relaxation in LT-ZnO. (C) 2012 Elsevier B.V. All rights reserved.