Nanodomain and interface structure in epitaxial BaTiO3 thin films on MgO deposited by magnetron sputtering

Abstract

High epitaxial quality BaTiO3 films were deposited on the MgO (001) substrate using RF magnetron sputtering at 800 °C by manipulating processing parameters. The BaTiO3 films have a ~200 nm thickness with a very low surface roughness but a rough interface structure with respect to the substrate. The epitaxial BaTiO3 films have a tetragonal crystal structure (a = 4.02 A and c = 4.11 A) with a tetragonality (c/a) of 1.02. The c-axis of the film is parallel to the growth direction as characterized by X-ray diffraction, electron diffraction, and high-resolution transmission electron microscopy. The orientation relationship between the film and the MgO is (001)BTO//(001)MgO and 〈100〉BTO//〈100〉MgO. Epitaxial nanodomains were formed in the film with a size ranging from 3 to 20 nm. The formation of the nanodomains is associated with the rough film/substrate interface due to the modification of the substrate surface characteristics (steps, terraces, and kinks) during the process. The two-dimensional interface structure between the film and the substrate was studied and its influence on the film microstructure is discussed.