Ordered deficient perovskite La_2/3TiO₃ films grown via molecular beam epitaxy

As the parent compound of a promising solid electrolyte material Li_3xLa_2/3−xTiO₃, the perovskite La_2/3TiO₃ has potential for advancing research on Li-intercalated ionic conductors. Epitaxial La_2/3TiO₃ films have been grown by molecular beam epitaxy using a growth process consisting of deposition and annealing cycles, with in situ monitoring by electron diffraction. X-ray absorption spectroscopy confirms the tetravalent state of Ti in La_2/3TiO₃, and the as-grown films are insulating. X-ray diffraction reveals the presence of half-order peaks, indicating a doubling of the pseudocubic perovskite unit cell due to the ordering of La vacancies in alternating A-site layers. These results demonstrate that single-phase, vacancy-ordered epitaxial films of La_2/3TiO₃ can be stabilized with excellent crystalline and electronic properties over wafer-sized areas, making possible Li-ion intercalation studies in films with well-defined domain boundary properties. Such boundaries are known to profoundly influence Li-ion conduction within the material. Understanding the effects of domain boundaries on Li-ion conduction could lead to improvements in solid-state battery technology and pave the way for the development of more efficient and safer energy storage devices.