Comparison Studies of Interfacial Electronic and Energetic Properties of LaAlO/TiO and TiO/LaAlO Heterostructures from First-Principles Calculations.

By using first-principles electronic structure calculations, we studied electronic and energetic properties of perovskite oxide heterostructures with different epitaxial growth order between anatase TiO and LaAlO. Two types of heterostructures, i.e., TiO film grown on LaAlO substrate (TiO/LaAlO) and LaAlO film grown on TiO substrate (LaAlO/TiO), were modeled. The TiO/LaAlO model is intrinsically metallic and thus does not exhibit an insulator-to-metal transition as TiO film thickness increases; in contrast, the LaAlO/TiO model shows an insulator-to-metal transition as the LaAlO film thickness increases up to 4 unit cells. The former model has a larger interfacial charge carrier density (n ∼ 10 cm) and smaller electron effective mass (0.47m) than the later one (n ∼ 10 cm, and 0.70m). The interfacial energetics calculations indicate that the TiO/LaAlO model is energetically more favorable than the LaAlO/TiO model, and the former has a stronger interface cohesion than the later model. This research provides fundamental insights into the different interfacial electronic and energetic properties of TiO/LaAlO and LaAlO/TiO heterostructures.