Unravelling the Origin of Ultra-Low Conductivity in SrTiO3 Thin Films: Sr Vacancies and Ti on A-Sites Cause Fermi Level Pinning

被引：10

作者：

Morgenbesser, Maximilian ^{[1
]}

Viernstein, Alexander ^{[1
]}

Schmid, Alexander ^{[1
]}

Herzig, Christopher ^{[1
]}

Kubicek, Markus ^{[1
]}

Taibl, Stefanie ^{[1
]}

Bimashofer, Gesara ^{[2
,3
]}

Stahn, Jochen ^{[2
]}

Vaz, Carlos Antonio Fernandes ^{[2
,4
]}

Dobeli, Max ^{[5
]}

Biautti, Federico ^{[6
]}

de Dios Sirvent, Juan ^{[6
]}

Liedke, Maciej Oskar ^{[7
]}

Butterling, Maik ^{[7
]}

Kaminski, Michal ^{[8
]}

Tolkiehn, Martin ^{[8
]}

Vonk, Vedran ^{[8
]}

Stierle, Andreas ^{[8
,9
]}

Wagner, Andreas ^{[7
]}

Tarancon, Albert ^{[6
,10
]}

Limbeck, Andreas ^{[1
]}

Fleig, Juergen ^{[1
]}

机构：

[1] TU Wien, Inst Chem Technol & Analyt, Getreidemarkt 9, A-1060 Vienna, Austria

[2] Paul Scherrer Inst, Lab Neutron Scattering & Imaging, CH-5232 Villigen, Switzerland

[3] Swiss Fed Inst Technol, Dept Chem & Appl Biosci, Ramistr 101, CH-8092 Zurich, Switzerland

[4] Paul Scherrer Inst, Swiss Light Source, Forschungsstr 111, CH-5232 Villigen, Switzerland

[5] Swiss Fed Inst Technol, Lab Ion Beam Phys, Otto Stern Weg 5,HPK H31, CH-8093 Zurich, Switzerland

[6] Catalonia Inst Energy Res IREC, Jardins Dones Negre 1,2a Pl, Barcelona 08930, Spain

[7] Helmholtz Zentrum Dresden Rossendorf, Inst Radiat Phys, Bautzner Landstr 400, D-01328 Dresden, Germany

[8] Deutsch Elektronen Synchrotron DESY, Notkestr 85, D-22607 Hamburg, Germany

[9] Univ Hamburg, Fachbereich Phys, D-22607 Hamburg, Germany

[10] Catalan Inst Res & Adv Studies ICREA, Barcelona 08930, Spain

来源：

ADVANCED FUNCTIONAL MATERIALS | 2022年 / 32卷 / 38期

基金：

奥地利科学基金会;

关键词：

fermi level pinning; pulsed laser depositions; site occupations; Sr vacancies; SrTiO; (3) thin films; strontium titanate; thin film characterization; ultra-low conductivities; LA-CODOPED SRTIO3; X-RAY-ABSORPTION; DOPED SRTIO3; ELECTRICAL-CONDUCTIVITY; DEFECT CHEMISTRY; IMPEDANCE; OXIDES; TRANSPORT; MODEL; ION;

D O I：

10.1002/adfm.202202226

中图分类号：

O6 [化学];

学科分类号：

0703 ;

摘要：

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.

引用

页数：20