Orientation relationships of copper crystals on sapphire (1 0 1¯ 0) m-plane and (1 0 1¯ 2) r-plane substrates

Copper films deposited on m- and r-plane sapphire substrates have been dewetted in either the solid or the liquid state, and equilibrated at 1253 K. The orientation relationships (ORs) between the dewetted copper crystals and the sapphire substrates have been investigated by electron backscatter diffraction. In addition, the shape of the copper/sapphire interface has been studied by scanning electron microscopy. Although the as-deposited films develop {1 1 1} surfaces parallel to both substrates, after solid state dewetting the copper crystals on the m-plane substrate are found to change their interface plane from Cu{1 1 1}||Al₂O₃(m-plane) to Cu{1 1 1}|| Al₂O₃ (a-plane), and after liquid state dewetting the preferred OR of copper on both m- and r-plane substrates may be expressed as: Cu{1 1 1}〈1 1 0〉 || Al₂O₃ {1 1 2¯ 0} 〈0 0 0 1〉. This OR is identical to that previously observed for copper on the sapphire a-plane.