Domain epitaxy in TiO2/α-Al2O3 thin film heterostructures with Ti2O3 transient layer...

Rutile TiO2 films were grown epitaxially on α-alumina (sapphire(0001)) substrates and characterized by x-ray diffraction and scanning transmission electron microscopy. It was revealed that the rutile film initially grows pseudomorphically on sapphire as Ti2O3 and, after a few monolayers, it grows tetragonally on the Ti2O3/sapphire platform. Formation of the Ti2O3 transient layer was attributed to the symmetry mismatch between tetragonal structure of TiO2 and hexagonal structure of alumina. The separation between the ½[10](101) misfit dislocations was dictated by Ti2O3 and was determined to be 9.7 Å which is consistent with 4/3 and 3/2 alternating domains across the film/substrate interface.