First-principles calculations of the electronic structure and defects of Al2O3

We present first-principles calculations of the electronic structure of the oxygen vacancies in theta-Al2O3 and amorphous Al2O3 (am-Al2O3) using the screened exchange (sX) hybrid functional. The sX hybrid functional can give correct band gap for both phases. The defect energy levels depend strongly on the charge state, with negative defects lying deep in conduction band. Transition levels between different charge states were determined. The 3-fold coordinated O vacancy dominates in theta-Al2O3 due to the higher formation energy of the 4-fold coordinated O vacancy. In am-Al2O3, only the +1/0 charge state of the 3-fold coordinated O vacancy and the +1/0, 0/-1 charge states of the 4-fold coordinated O vacancy have transition levels in the gap and these are near the conduction band edge. The large negative formation energy at O poor condition suggests that the oxygen defects widely exist in both phases. (C) 2013 AIP Publishing LLC.