Structural and electronic properties of cubic HfO2 surfaces

Using the first-principles method within the generalized gradient approximation, we have performed a systematic study on the structural and electronic properties of cubic HfO2 surfaces. We find that the most energetically favorable surfaces are (1 1 0) and (1 1 1) terminated with single oxygen layer, both of which are stoichiometric. The atomic relaxation in top layers of surface (1 1 1)-O and (1 1 0) exhibits very similar behavior, i.e. cations relax inward while anions outward. This could be well understood by the ionic feature of the Hf–O bond. Both of the two surfaces studied are insulating without any surface state in the energy gap.