Comparative Ab initio Calculations for ABO3 Perovskite (001), (011) and (111) as well as YAlO3 (001) Surfaces and F Centers

Authors R.I. Eglitis, A.I. Popov

Institute of Solid State Physics, University of Latvia, 8, Kengaraga Str., Riga LV1063, Latvia

Issue Volume 11, Year 2019, Number 1
Dates Received 22 November 2018; revised manuscript received 02 February 2019; published online 25 February 2019
Citation R.I. Eglitis, A.I. Popov, J. Nano- Electron. Phys. 11 No 1, 01001 (2019)
PACS Number(s) 68.35.Ct, 68.47.Gh
Keywords ABO3 perovskites, YAlO3, B3PW, F-center, (001) surfaces.ABOYAlOBPWF.

By means of the hybrid exchange-correlation functionals, we performed predictive ab initio calculations for industrially most important ABO3 perovskites, like, BaTiO3, SrTiO3, CaTiO3, SrZrO3 and PbZrO3 (001), (011) and (111) surfaces as well as bulk and (001) surface F-centers. From another side we performed comparative ab initio calculations for charged and polar YAlO3 (001) surfaces. For BaTiO3, CaTiO3, SrZrO3 and PbZrO3 perovskite neutral (001) surfaces, in most cases, all upper surface layer atoms relax inwards, whereas all second surface layer atoms relax upwards, and again, all third surface layer atoms relax inwards. The atom relaxation pattern for YAlO3 polar and charged (001) surfaces is completely different from the ABO3 perovskite neutral (001) surfaces. The ABO3 perovskite (001) surface energies are practically equal for both AO and BO2-terminations, and they are considerably smaller than (011) and especially (111) polar and charged surface energies. The atomic displacement magnitudes of nearest neighbor atoms around the (001) surface F-center in ABO3 perovskites are considerably larger than the related displacement magnitudes of nearest neighbor atoms around the bulk F-center. In the ABO3 perovskites the electron charge is considerably better localized inside the bulk F-center than in the (001) surface F-center, where the oxygen vacancy charge is more delocalized over the nearest neighbor atoms than in the bulk F-center case. The (001) surface F-center formation energy in the ABO3 perovskites is smaller than the bulk F-center formation energy, which triggers the F-center segregation from the ABO3 perovskite bulk towards its (001) surfaces. In most cases the (001) surface F-center induced defect level in the band gap of ABO3 perovskites is located closer to the (001) surface conduction band bottom than the bulk F-center induced defect level to the bulk conduction band bottom.

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