Plane-wave density functional theory calculations were made of formation energies, relaxed structures, and electrical levels of O vacancies and interstitial O atoms in monoclinic zirconia. The atomic structures of positively and negatively charged vacancies and interstitial O atoms were also investigated. The ionization energies and electron affinities of interstitial O atoms and O vacancies in different charge states were calculated with respect to the bottom of the zirconia conduction band. Using the experimental band offset values at the interface of ZrO2 films grown on Si, the positions of defect levels with respect to the bottom of Si conduction band were found. The results demonstrated that interstitial O atoms and positively charged O vacancies could trap electrons from the bottom of the zirconia conduction band and from Si. Neutral O vacancy serves as a shallow hole trap for electrons injected from the Si valence band. The calculations predict negative U for the O– center and stability of V+ centers with respect to disproportionation into V2+ and V0 in monoclinic zirconia.

Structure and Electrical Levels of Point Defects in Monoclinic Zirconia. A.S.Foster, V.B.Sulimov, F.L.Gejo, A.L.Shluger, R.M.Nieminen: Physical Review B, 2001, 64[22], 224108 (10pp)