Stabilization of stoichiometric LaTiO₃ thin films grown by pulsed laser deposition

Like in the famous oxide heterostructure LaAlO₃/SrTiO₃ (LAO/STO) a two dimensional electron system is found at the interface between the strongly correlated Mott insulator LaTi³⁺O₃ and the band insulator STO. In contrast to LAO, the stabilization of LaTi³⁺O₃ requires strong reducing growth conditions since the thermodynamically stable bulk phase is the oxygen-rich La₂Ti⁴⁺₂O₇. Therefore, we have systematically studied the impact of oxidizing and reducing background atmospheres and the influence of the substrate on LaTi³⁺O₃ thin film growth by pulsed laser deposition. In situ x-ray photoelectron spectroscopy of the films prepared on STO exhibit overoxidation probably due to oxygen out-diffusion from the STO substrate, which is reduced for growth on DyScO₃ due to the lower oxygen mobility. In addition, we found that a LAO capping layer of a few unit cells thickness acting like a diffusion barrier for oxygen prevents the LTO film from overoxidation during storage in air.