Journal Article

PUBDB-2022-06265

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Unravelling the Origin of Ultra‐Low Conductivity in SrTiO$_3$ Thin Films: Sr Vacancies and Ti on A‐Sites Cause Fermi Level Pinning

Morgenbesser, M.Extern* ; Viernstein, A.Extern* ; Schmid, A. (Corresponding author) ; Herzig, C. ; Kubicek, M.Extern* ; Taibl, S. ; Bimashofer, G. ; Stahn, J. ; Vaz, C. A. F. ; Döbeli, M. ; Biautti, F. ; de Dios Sirvent, J. ; Liedke, M. O. ; Butterling, M. ; Kamiński, M.DESY* ; Tolkiehn, M.DESY* ; Vonk, V.XFEL.EU*DESY* ; Stierle, A.XFEL.EU*DESY* ; Wagner, A.Extern*XFEL.EU* ; Tarancon, A. ; Limbeck, A. ; Fleig, J.Extern*

2022
Wiley-VCH Weinheim

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Please use a persistent id in citations: doi:10.1002/adfm.202202226  doi:10.3204/PUBDB-2022-06265

Abstract: Different SrTiO$_3$ thin films are investigated to unravel the nature of ultra-low conductivities recently found in SrTiO$_3$ 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$_3$ 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$_{Sr}$ and Ti$_{Sr}$) to accommodate nonstoichiometry. Sr vacancies act as mid-gap acceptor states, pinning the Fermi level, provided that additional donor states (most probably Ti$_{Sr}^{\bullet\bullet}$) 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.

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Contributing Institute(s):

1. DOOR-User (DOOR ; HAS-User)
2. PETRA-D (FS-PETRA-D)
3. Nanolab (FS-NL)

Research Program(s):

1. 632 - Materials – Quantum, Complex and Functional Materials (POF4-632) (POF4-632)
2. 6G3 - PETRA III (DESY) (POF4-6G3) (POF4-6G3)

Experiment(s):

1. PETRA Beamline P24 (PETRA III)

Appears in the scientific report 2022

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Database coverage:
; ; ; Clarivate Analytics Master Journal List ; Current Contents - Electronics and Telecommunications Collection ; Current Contents - Engineering, Computing and Technology ; Current Contents - Physical, Chemical and Earth Sciences ; DEAL Wiley ; Ebsco Academic Search ; Essential Science Indicators ; IF >= 15 ; JCR ; SCOPUS ; Science Citation Index Expanded ; Web of Science Core Collection

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