Domain formation in anatase TiO2 thin films on LaAlO3 substrates

Using advanced Cs-corrected scanning transmission electron microscopy, we have observed the atomic structures of coherent TiO2/LaAlO3 heterointerfaces in anatase TiO2 thin films deposited on single-crystal LaAlO3. Two epitaxial relationships are identified: (001)[100] TiO2//(001)[100] LaAlO3 and (001)[010] TiO2//(001)[100] LaAlO3. These epitaxial relationships and the terrace steps on the substrate surface result in the formation of multidomains in the anatase TiO2 thin films. Three types of domain boundaries are identified, namely, 90° rotation domain boundaries, translation domain boundaries, and mixtures of the two. These domain boundaries are expected to have a profound effect on the properties of the thin film.