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DS: Fachverband Dünne Schichten

DS 25: Focus Session: Resistive Switching by Redox and Phase Change Phenomena II (Valence and phase change in oxides)

DS 25.4: Talk

Wednesday, April 2, 2014, 12:15–12:30, CHE 89

Vacancy-vacancy interaction in SrTiO₃ bulk and surfaces — •Ali Al-Zubi, Gustav Bihlmayer, and Stefan Blügel — Peter Grünberg Institut (PGI) & Institute for Advanced Simulation (IAS), Forschungszentrum Jülich and JARA, 52425 Jülich, Germany

We employ the density functional theory (DFT) to model point defects, in particular oxygen vacancies, in the perovskite SrTiO₃. We use a bulk super-cell model to calculate the formation energy of single and double O-vacancies for different arrangements in the unit cell. Our results indicate a clear trend of the defects to form one-dimensional extended structures in the ground state.

We extend the study to surfaces and calculate the interaction energy of homogeneously distributed O-vacancies on SrO- and TiO₂-terminated (001) surfaces. To compare to the bulk, we investigate clustering effects, in particular on the TiO₂-terminated surface. For an analysis of the results, we study the role of structural relaxations and estimate the importance of electronic effects by comparison to DFT+U calculations that simulate correlation effects via a Hubbard-U parameter. Furthermore, interaction energies on the SrO-terminated surface are compared to results for O-vacancies in the SrO plane in the Ruddlesden-Popper phases, exhibiting the importance of screening effects in the bulk matrix.

We acknowledge the DFG, SFB 917 project A4, for financial support.