ZnIr2O4, a p-type transparent oxide semiconductor in the class of spinel zinc-d6-transition metal oxide

The authors report on the growth of spinel ZnMd62O4 M=Co, Rh, and Ir, a ρ-type wide band gap semiconductor by pulsed laser deposition. The band gap of these compounds is determined by the ligand field splitting in the subbands of the metallic d6 cation. Photoemission spectroscopy revealed that the valence band maximum is composed of occupied t2g 6 states. The observed band gap is increasing for higher quantum numbers, being as large as 3 eV for ZnIr2O4, which is expected from theoretical predictions. Grown in polycrystalline phase, films of these materials display high conductivity, well above 2 S cm−1.