Nanoscale Characterization of Atomic Positions in Orthorhombic Perovskite Thin Films

The crystal structure determines many of the physical properties of oxide perovskites (ABO₃) and only a tiny modification of the lattice structure causes major changes in the functional properties through the interplay among spin, orbital and charge orders. The determination of distortions and their associated symmetries is a valuable asset for understanding the structure properties relationship and guiding the design of epitaxial oxide heterostructures and correlated electronic states. Here, the in-depth structural characterization of a 50 nm-LaVO₃ thin film grown onto (110)-oriented DyScO₃ by molecular beam epitaxy is reported. The heterostructure is investigated by means of X-ray diffraction, high-resolution and scanning transmission electron microscopies, scanning precession electron diffraction tomography and first-principles calculations. LaVO₃ crystallizes in the orthorhombic Pbnm space group and is constrained by the substrate, which imposes a growth along the [110] orthorhombic direction, over the 140 deposited unit cells. The mapping of the reciprocal space allows determining the orientation of the film and refining the lattice parameters. Using scanning transmission electron microscopy, the structure of LaVO₃ is analyzed, focusing on the determination of the antipolar displacement of the rare earth. Additionally, 3D electron diffraction enables to resolve the atomic positions of all species within the film.