Calculations were made of energy levels associated with the O vacancy in monoclinic HfO2 using a hybrid density functional which accurately reproduced the experimental band-gap. The most stable charge states were obtained for a varying Fermi level in the HfO2 band gap. In order to compare these with measured defect levels, total energy differences which were specific to the considered experiment were determined. The results showed that the O vacancy could consistently account for the defect levels observed in (Poole-Frenkel-type) trap-assisted conduction, direct electron injection and optical absorption experiments.

Oxygen Vacancy in Monoclinic HfO2 - a Consistent Interpretation of Trap Assisted Conduction, Direct Electron Injection, and Optical Absorption Experiments. P.Broqvist, A.Pasquarello: Applied Physics Letters, 2006, 89[26], 262904 (3pp)