Anomalous lattice shrinking of LaTiO3 thin film on SrTiO3 (111) induced by three-dimensional electron transfer

Abstract

High-quality LaTiO3 films in the pseudocubic phase have been grown on SrTiO3 (111) using oxide molecular beam epitaxy. The in situ electron diffractions and ex situ scanning transmission electron microscopy reveal that the films with the thickness up to 60 monolayers bear the in-plane compressive strain, while the ex situ x-ray diffractions indicate the contracted out-of-plane interspacing. Such an anomalous lattice shrinking may be related to the formation of oxidized LaTiO3 + δ and, more importantly, the three-dimensional electron transfer from the film to the substrate. This is supported by spatial electron energy loss spectroscopy that shows the homogeneous distribution of Ti with increased valence in the film.