Back to Search
Start Over
Unravelling the Origin of Ultra-Low Conductivity in SrTiO3 Thin Films: Sr Vacancies and Ti on A-Sites Cause Fermi Level Pinning
- Source :
- Advanced Functional Materials 32(2022)38, 2202226, Advanced Functional Materials, 32 (38), Art.-Nr.: 2202226, Advanced Functional Materials, 32 (38)
- Publication Year :
- 2022
- Publisher :
- ETH Zurich, 2022.
-
Abstract
- Different SrTiO3 thin films are investigated to unravel the nature of ultra-low conductivities recently found in SrTiO3 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 SrTiO3 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 TiSr center dot center dot\[{\rm{Ti}}_{{\rm{Sr}}}{ \bullet \bullet }\]) 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.<br />Advanced Functional Materials, 32 (38)<br />ISSN:1616-3028<br />ISSN:1616-301X
Details
- Language :
- English
- ISSN :
- 16163028 and 1616301X
- Database :
- OpenAIRE
- Journal :
- Advanced Functional Materials 32(2022)38, 2202226, Advanced Functional Materials, 32 (38), Art.-Nr.: 2202226, Advanced Functional Materials, 32 (38)
- Accession number :
- edsair.doi.dedup.....1372ff122e8ee1c6c012b4a7de354780
- Full Text :
- https://doi.org/10.3929/ethz-b-000558042