Thin films of transition metal oxides open up a gateway to nanoscale electronic devices beyond silicon characterized by novel electronic functionalities. While such films are commonly prepared in an oxygen atmosphere, they are typically considered to be ideally terminated with the stoichiometric composition. Using the prototypical correlated metal SrVO3 as an example, it is demonstrated that this idealized description overlooks an essential ingredient: oxygen adsorbing at the surface apical sites. The oxygen adatoms, which persist even in an ultrahigh vacuum environment, are shown to severely affect the intrinsic electronic structure of a transition metal oxide film. Their presence leads to the formation of an electronically dead surface layer but also alters the band filling and the electron correlations in the thin films. These findings highlight that it is important to take into account surface apical oxygen or -- mutatis mutandis -- the specific oxygen configuration imposed by a capping layer to predict the behavior of ultrathin films of transition metal oxides near the single unit-cell limit.
@article{arxiv.2202.10778,
title = {Toward Functionalized Ultrathin Oxide Films: the Impact of Surface Apical Oxygen},
author = {Judith Gabel and Matthias Pickem and Philipp Scheiderer and Lenart Dudy and Berengar Leikert and Marius Fuchs and Martin Stübinger and Matthias Schmitt and Julia Küspert and Giorgio Sangiovanni and Jan M. Tomczak and Karsten Held and Tien-Lin Lee and Ralph Claessen and Michael Sing},
journal= {arXiv preprint arXiv:2202.10778},
year = {2022}
}