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Sci Adv. 2019 Feb 22;5(2):eaau8467. doi: 10.1126/sciadv.aau8467. eCollection 2019 Feb.

Probing vacancy behavior across complex oxide heterointerfaces.

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Department of Mechanical and Industrial Engineering, University of Massachusetts-Amherst, Amherst, MA 01003, USA.
Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI 53706, USA.
Department of Chemical Engineering and Materials Science, University of California, Irvine, Irvine, CA 92697, USA.
Institute of Physical Chemistry, RWTH Aachen University, Aachen 52056, Germany.


Oxygen vacancies ( V O ) play a critical role as defects in complex oxides in establishing functionality in systems including memristors, all-oxide electronics, and electrochemical cells that comprise metal-insulator-metal or complex oxide heterostructure configurations. Improving oxide-oxide interfaces necessitates a direct, spatial understanding of vacancy distributions that define electrochemically active regions. We show vacancies deplete over micrometer-level distances in Nb-doped SrTiO3 (Nb:SrTiO3) substrates due to deposition and post-annealing processes. We convert the surface potential across a strontium titanate/yttria-stabilized zirconia (STO/YSZ) heterostructured film to spatial (<100 nm) vacancy profiles within STO using (T = 500°C) in situ scanning probes and semiconductor analysis. Oxygen scavenging occurring during pulsed laser deposition reduces Nb:STO substantially, which partially reoxidizes in an oxygen-rich environment upon cooling. These results (i) introduce the means to spatially resolve quantitative vacancy distributions across oxide films and (ii) indicate the mechanisms by which oxide thin films enhance and then deplete vacancies within the underlying substrate.

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