  We perform ab initio calculations, based on density functional theory, of
substitutional and vacancy defects in the monoclinic hafnium oxide (m-HfO2) and
alpha-quartz (SiO2). The neutral oxygen vacancies and substitutional Si and Hf
defects in HfO2 and SiO2, respectively, are investigated. Our calculations show
that, for a large range of Hf chemical potential, Si substitutional defects are
most likely to form in HfO2, leading to the formation of a silicate layer at
the HfO2/Si interface. We also find that it is energetically more favorable to
form oxygen vacancies in SiO2 than in HfO2, which implies that oxygen deficient
HfO2 grown on top of SiO2 will consume oxygen from the SiO2.
