A first-principles study of native point defects in hafnia and zirconia was carried out in order to identify the predominant defects under various O chemical potentials and Fermi levels. Oxygen vacancies and O interstitials in both HfO2 and ZrO2 exhibited a negative-U behavior. It was shown that HfO2 was less prone to the formation of O point defects than was ZrO2 for the same O chemical potential. When the Fermi level was constrained to be within the band gap of Si, the predominant defects were negatively charged Hf or Zr vacancies under an intermediate to high O chemical potential. No evidence was found for magnetic defects.

First-Principles Study of Native Point Defects in Hafnia and Zirconia. J.X.Zheng, G.Ceder, T.Maxisch, W.K.Chim, W.K.Choi: Physical Review B, 2007, 75[10], 104112 (7pp)