Investigation of the Optical Properties of a BiFeO3/SrTiO3 Heterostructure Grown on an Al2O3(0001) Substrate by RF Cathode Sputtering

The phase composition, structure, and optical properties of the BiFeO3/SrTiO3/Al2O3 (c-cut) heterostructure have been studied using XRD analysis, spectrophotometry, and multi-angle ellipsometry. BFO/STO/A12O3 heterostructures have been obtained by high-frequency cathode sputtering in an oxygen atmosphere using the intermittent deposition technology. It was found that the BiFeO3 and SrTiO3 layers grew with an orientation in the direction of the [111] crystallographic axis parallel to the normal to the Al2O3 substrate. It has been shown that the damaged layer on the surface of the heterostructure does not exceed 2‒3 nm, and no signs of the presence of boundary layers at the Al2O3–SrTiO3 and SrTiO3–BiFeO3 interfaces have been identified. The dispersion dependences of the refractive indices of BFO and STO layers are calculated. The reasons for the revealed regularities are discussed.