Intrinsic vacancies in cubic-zirconia bulk and surface

Formation of charged (neutral) vacancies of bulk (surface) cubic-ZrO2 is calculated from density functional theory, and compared with available experiments. Relationships among vacancy formation energy, electron and element chemical potentials are established within a wide range of oxygen chemical potentials. The +2 (−2) oxygen (zirconium) vacancy is predicted stable near the valence (conduction) band edge of the bulk, and the neutral oxygen vacancy has the lowest formation energy on (1 0 0) O-terminated surface without exhibiting a defect state within the band gap. Therefore, manipulation of oxygen vacancy concentration becomes possible by optimizing growth surface and oxygen chemical potentials.

Figure optionsDownload as PowerPoint slideResearch highlights▶ It suggested that VO2+ is the most stable vacancy near VBM in pure bulk zirconia under a wide range of oxygen chemical potentials which makes it difficult to realize p-type ZrO2. ▶ The formation of oxygen vacancy is spontaneous under oxygen-poor conditions, but not for the zirconium one even at a favored zirconium-poor condition. ▶ Vacancy formation energy of the oxygen increases along with an increase in Fermi level (for instance through doping). Stability of neutral oxygen vacancy not only depends on the dimension of the structure (higher on surface than in the bulk) but also the polarity nature of surface (higher on polar surface than the nonpolar ones).