Anomalous Defect Dependence of Thermal Conductivity in Epitaxial WO3 Thin Films

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Lattice defects typically reduce lattice thermal conductivity, which has been widely exploited in applications such as thermoelectric energy conversion. Here, an anomalous dependence of the lattice thermal conductivity on point defects is demonstrated in epitaxial WO3 thin films. Depending on the substrate, the lattice of epitaxial WO3 expands or contracts as protons are intercalated by electrolyte gating or oxygen vacancies are introduced by adjusting growth conditions. Surprisingly, the observed lattice volume, instead of the defect concentration, plays the dominant role in determining the thermal conductivity. In particular, the thermal conductivity increases significantly with proton intercalation, which is contrary to the expectation that point defects typically lower the lattice thermal conductivity. The thermal conductivity can be dynamically varied by a factor of approximate to 1.7 via electrolyte gating, and tuned over a larger range, from 7.8 to 1.1 W m(-1) K-1, by adjusting the oxygen pressure during film growth. The electrolyte-gating-induced changes in thermal conductivity and lattice dimensions are reversible through multiple cycles. These findings not only expand the basic understanding of thermal transport in complex oxides, but also provide a path to dynamically control the thermal conductivity.
Publisher
WILEY-V C H VERLAG GMBH
Issue Date
2019-10
Language
English
Article Type
Article
Citation

ADVANCED MATERIALS, v.31, no.43, pp.1903738

ISSN
0935-9648
DOI
10.1002/adma.201903738
URI
http://hdl.handle.net/10203/270047
Appears in Collection
NT-Journal Papers(저널논문)
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