Comparison Studies of Interfacial Electronic and Energetic Properties of LaAlO₃/TiO₂ and TiO₂/LaAlO₃ 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 2 and LaAlO 3 . Two types of heterostructures, i.e., TiO 2 film grown on LaAlO 3 substrate (TiO 2 /LaAlO 3 ) and LaAlO 3 film grown on TiO 2 substrate (LaAlO 3 /TiO 2 ), were modeled. The TiO 2 /LaAlO 3 model is intrinsically metallic and thus does not exhibit an insulator-to-metal transition as TiO 2 film thickness increases; in contrast, the LaAlO 3 /TiO 2 model shows an insulator-to-metal transition as the LaAlO 3 film thickness increases up to 4 unit cells. The former model has a larger interfacial charge carrier density ( n ∼ 10 14 cm –2 ) and smaller electron effective mass (0.47 m e ) than the later one ( n ∼ 10 13 cm –2, and 0.70 m e ). The interfacial energetics calculations indicate that the TiO 2 /LaAlO 3 model is energetically more favorable than the LaAlO 3 /TiO 2 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 2 /LaAlO 3 and LaAlO 3 /TiO 2 heterostructures.