Oxygen vacancy migration was studied in monoclinic HfO2 and across its interface with SiO2 through density functional calculations. In HfO2, long-range diffusion shows activation barriers of 2.4 and 0.7eV for the neutral and doubly positively charged vacancy, respectively. In the latter case, the migration preferentially occurred along one-dimensional pathways. A HfO2/SiO2 interface model was constructed to address O vacancy migration across high-κ gate stacks. The vacancy was shown to stabilize in its neutral charge state upon entering the SiO2 layer.

Migration of Oxygen Vacancy in HfO2 and Across the HfO2/SiO2 Interface - a First-Principles Investigation. N.Capron, P.Broqvist, A.Pasquarello: Applied Physics Letters, 2007, 91[19], 192905