Orthorhombic ITO epitaxially stabilized on a perovskite oxide substrate

Doped indium oxides, such as indium tin oxide (ITO), have been used as transparent conducting materials and have recently attracted increasing interest as thin-film channel materials for high-performance field-effect transistors. In numerous studies on crystalline ITO, stable bixbyite-type (cubic) and metastable corundum-type (rhombohedral) phases have been investigated. Here, we demonstrate an epitaxial stabilization of the ITO polytype having Rh2O3-II-type (space group: Pbna) orthorhombic structure using an orthorhombic perovskite oxide (110) DyScO3 (DSO) substrate. Distorted-orthorhombic ITO (o-ITO) films could be epitaxially grown at substrate temperatures of approximately 350 °C. The epitaxial relationships were determined to be ITO[100]//DSO[100] and ITO[001]//DSO[001], whereas the [010] of ITO was slightly inclined relative to that of DSO because of the strain effect. The transport properties of a distorted o-ITO film were better than those of a bixbyite-type ITO film grown on yttria-stabilized zirconia substrate, indicating that o-ITO has a potential of high-performance oxide semiconductor contributing to future electronics.