Atomic control of layer-by-layer epitaxial growth on Molecular-dynamics simulations

Molecular-dynamics simulations were performed to clarify the structures of SrO and BaO layers on a (Formula presented) substrate at the atomic level, and to predict an appropriate buffer layer for (Formula presented) heterojunction. The atomic structure of these layers grown on a (Formula presented) substrate terminated on the (Formula presented) atomic plane was investigated. From the analysis of the angle distribution of Sr-O-Sr and the radial distribution between Sr and O, the first single SrO layer on the (Formula presented) substrate was found to keep a perfect NaCl-type structure. However, the structure of the second SrO layer deviated from a NaCl-type structure. This result suggests that only a single SrO layer is able to grow epitaxially and uniformly on the (Formula presented) substrate terminated on the (Formula presented) atomic plane. Since a BaO layer is one component of the (Formula presented) layered structure, a detailed understanding of the (Formula presented) heterojunction has been desired. Here, the stress induced by the lattice mismatch of the (Formula presented) and (Formula presented) heterojunction was evaluated. The (Formula presented) gained 1.2 GPa stress, while surprisingly the (Formula presented) did not have any stress. Moreover, the BaO layer was found to grow epitaxially and uniformly on the (Formula presented) Note that (Formula presented) is expected to grow epitaxially on a BaO layer since the BaO layer is a part of the (Formula presented) layered structure. Hence, we suggest that BaO/SrO is a suitable buffer layer for the (Formula presented) heterojunction.