Epitaxial Growth of TiO2 Rutile Thin Films on Sapphire Substrates by a Reactive Ionized Cluster Beam Method

TiO2 thin films were grown on sapphire substrates at 500°C by means of reactive ionized cluster beam (RICB) deposition. The TiO2 thin films grown on sapphire (0001) and (112̄0) substrates were single-crystalline and had the rutile structure. The epitaxial orientation relationships between the rutile films and the sapphire substrates were found to be (1) rutile (200)//Al2O3(0001) and (2) rutile (101)//Al2O3(112̄0). On (11̄02) sapphire substrates, the films showed both the anatase (101) and rutile (101) structures. The concept of near-coincidence lattice sites was applied to show that the lattice misfit at the interface between these rutile and sapphire planes was small (less than a few percent).