The origin of high-mismatch orientation relationships for ultra-thin oxide overgrowths

A crystallographic orientation relationship (COR) of unusually high lattice mismatch (> 15%) between an Al {1 0 0} substrate and its ultra-thin (<1 nm) oxide overgrowth is reported. This striking observation is in contrast with the general assumption that a COR with the lowest mismatch is preferred. However, as shown by thermodynamic model calculations, despite the relatively large energy contributions from residual strain and misfit dislocations, the high-mismatch overgrowth can be stabilized by a relatively low surface energy and a relatively high density of metal-oxygen bonds across the interface. (C) 2007 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.