Orientation relationships of copper crystals on c-plane sapphire

Copper particles have been grown on sapphire (0 0 0 1) substrates by dewetting a copper film either in the solid or the liquid state. After equilibration the particles adopt different orientation relationships (ORs). Solid state dewetting produces a single OR: Cu(1 1 1)[1 (1) over bar 0]parallel to Al(2)O(3)(0 0 0 1)[1 0 (1) over bar 0]. In contrast, dewetting in the liquid state (followed by solid state equilibration) produces four additional ORs, Cu(1 1 1) [1 (1) over bar 0]parallel to Al(2)O(3)(0 0 0 1)(2 (1) over bar (1) over bar 0], Cu(1 1 0)[1 (1) over bar 0]parallel to Al(2)O(3)(0 0 0 1)[2 (1) over bar (1) over bar 0], Cu(3 1 1)[0 1 (1) over bar]parallel to Al(2)O(3)(0 0 0 1)[2 (1) over bar (1) over bar 0] and Cu(2 1 0)[0 0 1]parallel to Al(2)O(3)(0 0 0 1) [2 (1) over bar (1) over bar 0], which have been found to have a similar interfacial energy. All of the ORs observed in this study are consistent with the Fecht and Gleiter lock-in model, from which one would expect that densely packed directions in the interface plane of the metal crystals will tend to align with relatively dense directions in the substrate surface. The 30 degrees change in alignment direction on the c-sapphire side of the interface, from Al(2)O(3) [1 0 (1) over bar 0] for solid state dewetted samples to Al(2)O(3) [2 (1) over bar (1) over bar 0] for samples dewetted in the liquid state, appears to be related to a reconstruction of the copper c-sapphire interface that occurs at a temperature between those at which the two types of samples are processed. (C) 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.