Tuning the electronic properties of epitaxial strained CaFeO 3-δ thin films

Abstract

Strain engineering of transition metal oxides due to their desirable properties has long been a focal point in both physics and material sciences. Here, we investigate the strain dependence of electronic and optical properties of the high valence iron-based perovskite CaFeO 3-δ. Using substrates with various lattice constants, we achieve a wide range of tunable epitaxial strain states in CaFeO 3-δ thin films ranging from compressive -0.37% to tensile 3.58%. Electrical transport and optical absorption measurements demonstrate a distinct strain-dependent behavior, in which larger tensile strain leads to higher electrical resistivity and a larger optical bandgap. We attribute these modulations to tensile strain suppressed p-d hybridization in CaFeO 3-δ, as evidenced by soft X-ray absorption spectra measurements.