Interface atomic structure of LaCuOSe:Mg epitaxial thin film and MgO substrate

In order to understand the growth mechanism of magnesium doped LaCuOSe thin film on MgO, the atomic structure of the interface between the epitaxial thin film and the substrate was investigated. Electron diffraction confirmed the orientation relationship between the film and the substrate as (0 0 1)[1 0 0]LaCuOSe:Mg//(0 0 1)[1 0 0]MgO. High resolution Z-contrast imaging based on the high angle annular dark field scanning transmission electron microscope (HAADF-STEM) technique clearly revealed the alternate stacking of La–O layers and Cu–Se layers, and identified a peculiar stacking sequence of La layers at the interface. With the aid of first principles calculations of the interfacial adhesive energy, it was found that the different La layers at the interface play a key role in stabilizing the interface.