Twin intersections in silicon on sapphire

Twin intersections and terminations have been examined in epitaxial films of silicon on sapphire by high-resolution electron microscopy. Twins are found to propagate to the Si surface or to terminate within the bulk. Termination occurs either at {112} twin boundaries or by intersection with a second twin. Intersection results in the formation of segments of Σ9 {111}/{115} and {114} boundaries. Removal of twin boundaries during high-temperature annealing is shown to be thermally activated and a grain boundary migration mechanism is discussed.