Electronic structure of Pt/HfO2 interface with oxygen vacancy

Using first-principles calculations, we study the electronic structures of Pt/HfO2 interface in the presence of oxygen vacancy. The energetics and charge transfer are examined when the oxygen vacancy is at various distances from the interface. It is found that the oxygen vacancy is strongly attracted to the interface and the charge transfer decreases monotonically as the vacancy moves away from the interface, albeit the amount of charge transfer is small. The charge transfer results in the decrease of the effective work function of Pt, consistent with the vacancy mechanism to explain the shift in the flat-band voltage.