SKM 2023 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 72: Gerhard Ertl Young Investigator Award Competition
O 72.3: Vortrag
Donnerstag, 30. März 2023, 11:30–12:00, CHE 89
Electronic States and Polarons on Polar Surfaces — •Michele Reticcioli1, Florian Ellinger1, Martin Setvin2, and Cesare Franchini1,3 — 1University of Vienna (Austria) — 2Charles University, Prague (Czech Republic) — 3University of Bologna (Italy)
Polar surfaces of oxides exhibit an internal electric field and intrinsic excess charge that might be exploited for a wide range of applications, such as catalysis or electron-hole separation for solar light harvesting. However, there is very limited fundamental understanding of the processes induced by the surface polarity. In our study we attempt to shed some light on the nature of the electric field and the interplay with surface charge. Our density functional theory calculations and scanning-probe microscopy measurements on KTaO3(001) show spontaneous localization of the excess charge in the form of electron and hole polarons. In the absence of external perturbations, the internal electrostatic potential keeps the electron-hole polaron pairs spatially separated. We also show that the electronic properties of the surface can be tuned by adsorbing molecules and metal atoms. Finally, we apply these concepts to more debated cases, such as the SrTiO3(001) surface, where the polarity is too weak to produce a large charge separation. We believe that our findings contribute to deepen the interpretation of polar surfaces of oxides and ionic compounds in general.