Epitaxial growth of manganese oxide films on MgAl2O4 (001) substrates and the possible mechanism

•Three types of manganese oxide films were grown on MgAl2O4 (001) substrates by molecular beam epitaxy.•The structural characteristics and chemical compositions of the films were investigated systematically by using multiple measurement methods.•The critical thicknesses of the films are different under different growth conditions.•An epitaxial stabilization model was used to explain the growth mechanism of the films.

Three types of manganese oxide films were grown on MgAl2O4 (001) substrates by plasma-assisted molecular beam epitaxy (PA-MBE) under different growth rates and substrate temperatures. The structural characteristics and chemical compositions of the films were investigated by using in-situ reflection high-energy electron diffraction (RHEED), ex-situ X-ray diffraction, Raman, and X-ray photoelectron spectra (XPS). At a lower substrate temperature (730 K), the epitaxial film tends to form mixed phases with a coexistence of Mn3O4 and Mn5O8 in order to relieve the mismatch-strain. However, at a higher substrate temperature (750 K), all of the films crystallize into Mn3O4; the critical thickness of the film grown under a lower growth rate (7 Å/min) is much larger than that under a high growth rate (10 Å/min). When the film reaches a certain critical thickness, the surface will become fairly rough, and another oriented phase Mn3O4 would crystallize on such a surface.