Impact of epitaxial strain on crystal field splitting of α-Cr₂O₃(0001) thin films quantified by X-ray photoemission spectroscopy

Abstract

The influence of epitaxial strain on the electronic structure of α-Cr2O3(0001) thin films is probed by combining X-ray photoemission spectroscopy and crystal field multiplet calculations. In-plane lattice strain introduces distortions in the CrO6 octahedron and splits the 3d orbital triplet t2g into a1 + e orbitals. For relaxed thin films, the lines-shape of the Cr 2p core levels are well reproduced when the t2g subset is fully degenerated. In-plane tensile strain stabilizes a1 with respect to e orbitals, whereas compressive strain destabilizes a1 orbitals. Understanding these crystal field variations is essential for tuning the physical properties of α-Cr2O3 thin films.