PNNL

Abstract

We have investigated the early stages of Alpha-Fe2O3 (0001) film growth on Alpha-Al2O3 (0001) using oxygen-plasma-enhanced molecular beam epitaxy along with reflection high-energy electron diffraction, noncontact atomic force microscopy, and x-ray photoelectron spectroscopy and diffraction. A compressionally-strained, fully-stoichiometric Alpha-Fe2O3 film three monolayers thick forms prior to the onset of three-dimensional island formation and lattice relaxation. The surface of this film appears to buckle along , giving rise to a new set of inwardly-contracted diffraction spots which, if not resolved from the substrate spots, could be interpreted as a 12% in-plane lattice parameter expansion. Such an interpretation has led prior investigator to conclude that the interfacial layer consists of a disordered cation layer with an in-plane lattice parameter ~6% larger than that of Alpha-Fe2O3 [4]. Our interpretation of the diffraction data suggests that the interfacial layer is badly distorted, but commensurate with the substrate.