TY  - JOUR
AU  - Morgenbesser, Maximilian
AU  - Viernstein, Alexander
AU  - Schmid, Alexander
AU  - Herzig, Christopher
AU  - Kubicek, Markus
AU  - Taibl, Stefanie
AU  - Bimashofer, Gesara
AU  - Stahn, Jochen
AU  - Vaz, Carlos Antonio Fernandes
AU  - Döbeli, Max
AU  - Biautti, Federico
AU  - de Dios Sirvent, Juan
AU  - Liedke, Maciej Oskar
AU  - Butterling, Maik
AU  - Kamiński, Michał
AU  - Tolkiehn, Martin
AU  - Vonk, Vedran
AU  - Stierle, Andreas
AU  - Wagner, Andreas
AU  - Tarancon, Albert
AU  - Limbeck, Andreas
AU  - Fleig, Jürgen
TI  - 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
JO  - Advanced functional materials
VL  - 32
IS  - 38
SN  - 1057-9257
CY  - Weinheim
PB  - Wiley-VCH
M1  - PUBDB-2022-06265
SP  - 2202226
PY  - 2022
AB  - 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.
LB  - PUB:(DE-HGF)16
UR  - <Go to ISI:>//WOS:000821635900001
DO  - DOI:10.1002/adfm.202202226
UR  - https://bib-pubdb1.desy.de/record/484450
ER  -