Atomic and electronic structures of domain boundaries in LaTiO3 thin films

Abstract

Domain boundaries in perovskite oxides often exhibit abundant physical properties and phenomena. Here, epitaxial LaTiO3 thin films on (100) SrTiO3 substrates are prepared by pulsed-laser deposition. X-ray diffraction and transmission electron microscopy investigations reveal that the epitaxial LaTiO3 thin films have good crystallinity but a high density of domain boundaries. Atomic-scale scanning transmission electron microscopy observations reveal that two types of domain boundaries are formed in the LaTiO3 thin films. The type I domain boundaries are formed on the {100} crystal planes, while the type II domain boundaries on the {110} crystal planes. Electron energy-loss spectroscopy analyses suggest that the valence states of Ti ions at the type I domain boundaries are +3, while those at the type II domain boundaries are +4. First-principles calculations reveal that the bandgap decreases at both domain boundaries compared to the bulk. The carrier concentration at the type I domain boundaries is significantly higher than that of the bulk, while the carrier concentration at the type II domain boundaries is lower. These findings suggest that domain boundaries play an important role in tailoring the electrical properties of the LaTiO3 thin films, thereby promoting the potential applications and property modulation of related materials and devices.