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)[11¯0]||Al2O3(0 0 0 1)[101¯0]. In contrast, dewetting in the liquid state (followed by solid state equilibration) produces four additional ORs, Cu(1 1 1) [11¯0]||Al2O3(0 0 0 1)[21¯1¯0], Cu(1 1 0)[11¯0]||Al2O3(0 0 0 1)[21¯1¯0], Cu(3 1 1)[011¯]||Al2O3(0 0 0 1)[21¯1¯0] and Cu(2 1 0)[0 0 1]||Al2O3(0 0 0 1) [21¯1¯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° change in alignment direction on the c-sapphire side of the interface, from Al2O3[101¯0] for solid state dewetted samples to Al2O3[21¯1¯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.