%0 Journal Article
%A Morgenbesser, Maximilian
%A Viernstein, Alexander
%A Schmid, Alexander
%A Herzig, Christopher
%A Kubicek, Markus
%A Taibl, Stefanie
%A Bimashofer, Gesara
%A Stahn, Jochen
%A Vaz, Carlos Antonio Fernandes
%A Döbeli, Max
%A Biautti, Federico
%A de Dios Sirvent, Juan
%A Liedke, Maciej Oskar
%A Butterling, Maik
%A Kamiński, Michał
%A Tolkiehn, Martin
%A Vonk, Vedran
%A Stierle, Andreas
%A Wagner, Andreas
%A Tarancon, Albert
%A Limbeck, Andreas
%A Fleig, Jürgen
%T Unravelling the Origin of Ultra‐Low Conductivity in SrTiO<sub>3</sub> Thin Films: Sr Vacancies and Ti on A‐Sites Cause Fermi Level Pinning
%J Advanced functional materials
%V 32
%N 38
%@ 1057-9257
%C Weinheim
%I Wiley-VCH
%M PUBDB-2022-06265
%P 2202226
%D 2022
%X Different SrTiO<sub>3</sub> thin films are investigated to unravel the nature of ultra-low conductivities recently found in SrTiO<sub>3</sub> films prepared by pulsed laser deposition. Impedance spectroscopy reveals electronically pseudo-intrinsic conductivities for a broad range of different dopants (Fe, Al, Ni) and partly high dopant concentrations up to several percent. Using inductively-coupled plasma optical emission spectroscopy and reciprocal space mapping, a severe Sr deficiency is found and positron annihilation lifetime spectroscopy revealed Sr vacancies as predominant point defects. From synchrotron-based X-ray standing wave and X-ray absorption spectroscopy measurements, a change in site occupation is deduced for Fe-doped SrTiO<sub>3</sub> films, accompanied by a change in the dopant type. Based on these experiments, a model is deduced, which explains the almost ubiquitous pseudo-intrinsic conductivity of these films. Sr deficiency is suggested as key driver by introducing Sr vacancies and causing site changes (Fe<sub>Sr</sub> and Ti<sub>Sr</sub>) to accommodate nonstoichiometry. Sr vacancies act as mid-gap acceptor states, pinning the Fermi level, provided that additional donor states (most probably Ti<sub>Sr</sub><sup>••</sup>) are present. Defect chemical modeling revealed that such a Fermi level pinning also causes a self-limitation of the Ti site change and leads to a very robust pseudo-intrinsic situation, irrespective of Sr/Ti ratios and doping.
%F PUB:(DE-HGF)16
%9 Journal Article
%U <Go to ISI:>//WOS:000821635900001
%R 10.1002/adfm.202202226
%U https://bib-pubdb1.desy.de/record/484450