Berlin 2024 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 67: Poster: Oxide, Insulator and Semiconductor Surfaces

O 67.6: Poster

Mittwoch, 20. März 2024, 18:00–20:00, Poster C

Polaron formation on BaTiO3 surfaces induced by oxygen vacancies — •Andreas Ziegler and Bernd Meyer — Interdisciplinary Center for Molecular Materials and Computer Chemistry Center, FAU Erlangen-Nürnberg, Germany

BaTiO3 is widely used as substrate and recently found interest in catalysis for oxidative coupling reactions. For these applications it is important to understand its surface properties in an oxygen-deficient state. While the localization of electrons due to oxygen vacancies has been studied intensely for bulk BaTiO3, excess electrons on the surfaces of BaTiO3 have not been elucidated yet.

We applied spin-polarized density functional theory (DFT) with an on-site Hubbard+U correction to determine the behavior of defect electrons created by oxygen vacancies on the Ba- and Ti-terminated BaTiO3(001) surface. By applying atomic distortions before geometry optimization we achieved different localization/delocalization pattern of the two defect electrons. We find that localization of both electrons is energetically always more favorable than solutions with delocalized electrons. On the Ba-terminated surface, in the lowest-energy configuration, one electron is localized within the oxygen vacancy on the surface and the other on a Ti ion in the subsurface layer. This is in contrast to the bulk, where both defect electrons preferentially localize on neighboring Ti sites. On the Ti-terminated surface, strong surface relaxations occur, hindering an electron to localize in the vacancy and allowing localization only on two specific Ti sites.

Keywords: barium titanate surfaces; surface polarons; DFT+U calculations

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