Impact of oxygen vacancies on monoclinic hafnium oxide and band alignment with semiconductors

The structures, electronic properties, density of states of baddeleyite phase of hafnium oxide have been investigated by first-principles calculations based on the density functional theory. The calculations carried out by the advanced hybrid functional of Heyd, Scuseria, Ernzerhof. The impacts of two types of oxygen vacancies are investigated. The fourfold coordinated oxygen vacancy (VO-IV) shows a tendency of decreasing the gap value, while the threefold coordinated oxygen vacancy (VO-III) increasing. It is caused from the internal deformation in crystal. Based on the movement of Fermi energy level in the gap, a simple semiconductors-HfO2 band alignment model with the influence of the oxygen vacancies is discussed. The oxygen vacancies concentrating in interface, near interface and bulk area show different characteristic.