Dresden 2026 – scientific programme
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O: Fachverband Oberflächenphysik
O 93: Electronic structure of surfaces: Spectroscopy, surface states III
O 93.8: Talk
Friday, March 13, 2026, 11:15–11:30, HSZ/0201
Defect-driven polarity compensation on weakly polar BaTiO3 (001) and SrTiO3 (001) surfaces. — •Darin Joseph1, Llorenç Albons4, Florian Ellinger2, Michele Reticcioli2,3, Martin Setvin4, and Cesare Franchini1,2 — 1University of Bologna, Italy — 2University of Vienna, Austria — 3CNR-SPIN, L’ Aquila, Italy — 4Charles University, Prague , Czech Republic
BaTiO3 (001) and SrTiO3 (001), commonly classified as Tasker Type I and nonpolar, exhibit surface instability, as evidenced by A-site (Ba/Sr) adatoms and vacancies on cleaved surfaces observed in experiments. Density Functional Theory (DFT) calculations revealed the work function variation between the TiO2 and AO terminations and an electric field in the vacuum of asymmetric slabs, which are typically associated with polar surfaces. Our study reveals that both perovskites exhibit weak polar stacking along the crystallographic axis, leading to surface charges on the pristine terminations and creating an unfavorable electrostatic environment. Our analysis shows that the experimentally observed A-site defects act as compensation mechanisms by counterbalancing these charges to restore charge equilibrium. Charge compensation occurs at 12.5% Sr adatom and 12% vacancy coverage for SrTiO3 and at approximately 12-13% defect concentration for BaTiO3. These theoretical values are consistent with the experimental defect concentrations.
Keywords: Weak Polarity; DFT; Defects; Perovskite surfaces; Polarity compensation