Regensburg 2022 – wissenschaftliches Programm

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KFM: Fachverband Kristalline Festkörper und deren Mikrostruktur

KFM 17: Focus Session: Surfaces and Interfaces of (Incipient) Ferroelectrics (joint session O/KFM)

KFM 17.4: Vortrag

Mittwoch, 7. September 2022, 16:15–16:30, H3

Polaronic Properties of the weakly-polar SrTiO3(001) Surface — •Florian Ellinger1, Michele Reticcioli1, Igor Sokolović2, Ulrike Diebold2, Martin Setvín3, and Cesare Franchini1,41University of Vienna — 2Technische Universität Wien — 3Charles University Prague — 4Università di Bologna

The SrTiO3(001) surface shows ferroelectric-like distortions on the bulk-like termination, an out-of-plane dipole moment, and so-called "weak polarity". Recent experiments propose that these effects are compensated by Sr-adatoms and -vacancies, stabilizing the unreconstructed surface. [1]

We investigate the 1 × 1 SrTiO3(001) surface with TiO2- and SrO-terminations by means of density functional theory (DFT) simulations. Our calculations confirm the experimental interpretation and show that these polarity-compensating surface defects introduce additional charge. Adsorbing Sr-adatoms and doping with Nb leads to excess electrons in the crystal, facilitating the formation of electron-polarons. On the other hand, by creating Sr-vacancies on the surface we introduce excess holes to the system, which can localize as hole-polarons. For both kinds of polarons we analyze their general properties, e.g., the preferred localization site or stability. Further, we compare results of different structural phases of this crystal to achieve a comprehensive understanding of mentioned physical phenomena.

[1] Sokolović et al., Incipient ferroelectricity: A route towards bulk-terminated SrTiO3, Phys. Rev. Materials 3, 034407 (2019)

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