Band gap and electronic structure of cubic, rhombohedral, and orthorhombic In_2O_3 polymorphs: Experiment and theory

摘要

Recent studies on In_2O_3 have revealed a rich phase diagram and have led to the discovery of new In_2O_3 polymorphs, including the synthesis and ambient recovery of Pbcn In_2O_3. The electronic properties of this new phase are studied together with other better-known polymorphs (Ia3 and R3c) using soft x-ray absorption and emission spectroscopy, directly probing the partial density of states and transition matrix elements. Together with complementary full-potential all-electron density functional theory calculations, this allows important material parameters, such as the electronic band gap and partial density of states, to be elucidated. Excellent agreement between experiment and theory is obtained, with band gaps of 3.2 ± 0.3, 3.1 ± 0.3, and 2.9 ± 0.3 eV determined for the Ia3, R3c, and Pbcn In_2O_3 polymorphs, respectively. The effective mass of carriers in Pbcn In_2O_3 is predicted to be 12% less than in the widely used Ia3 polymorph while having a similar effective optical band gap.