Stabilization of extended stacking faults by {111}/{112} twin junction interactions

Extended stacking faults, with lengths of up to 10 nm, that join {1 1 1}/{1 1 2} twin-boundary junctions were observed by high-resolution transmission electron microscopy (HRTEM) in gold thin films. Circuit analysis shows that these defects possess a Burgers vector of 1/3 < 1 1 1 >. In order to explain the generation of these extended defects, we consider the behavior of 1/3 < 1 1 1 > dislocations at {1 1 1}- and {1 1 2)-type twin boundaries and near {1 1 1}/{1 1 2} twin-boundary junctions using HRTEM observations and theoretical modeling. By establishing the interaction forces that lead to this defect configuration, our analysis shows that the relief of intrinsic strain at the junction corners, which results from the incompatibility of the translation states at the intersecting boundaries, is sufficient to stabilize the stacking fault extension. Because grain-boundary junctions possess intrinsic strain fields whenever they join boundaries with incompatible translation states, similar mechanisms for stacking fault emission may arise between other closely spaced grain-boundary junctions. (C) 2007 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.