Electrical and optical properties of excess oxygen intercalated CuScO2(0001) epitaxial films prepared by oxygen radical annealing

A CuScO2(0001) epitaxial film with an oxygen intercalation layer was formed by annealing using oxygen radicals, and the electrical and optical properties of the epitaxial film were investigated. The thickness of the layer was 60 nm from the film surface, and its electrical conductivity was analyzed by using the two-layer model. The dependence on temperature of the electrical conductivity and Seebeck coefficient revealed that the dominant conduction mechanism of the layer was a small polaron conduction above 150 K and that it changed to two-dimensional variable-range hopping conduction below 150 K. The optical average transmittance of the epitaxial film was larger than 65% in the visible/near-infrared regions, while the energy gap for direct allowed transition was estimated as 3.7 eV.