Band gap, electronic structure, and surface electron accumulation of cubic and rhombohedral In2O3

The bulk and surface electronic structure of In₂O₃ has proved controversial, prompting the current combined experimental and theoretical investigation. The band gap of single-crystalline In₂O₃ is determined as 2.93±0.15 and 3.02±0.15eV for the cubic bixbyite and rhombohedral polymorphs, respectively. The valence-band density of states is investigated from x-ray photoemission spectroscopy measurements and density-functional theory calculations. These show excellent agreement, supporting the absence of any significant indirect nature of the In₂O₃ band gap. Clear experimental evidence for an s-d coupling between In4d and O2s derived states is also observed. Electron accumulation, recently reported at the (001) surface of bixbyite material, is also shown to be present at the bixbyite (111) surface and the (0001) surface of rhombohedral In₂O₃ .