Premium
Anomalous Defect Dependence of Thermal Conductivity in Epitaxial WO 3 Thin Films
Author(s) -
Ning Shuai,
Huberman Samuel C.,
Ding Zhiwei,
Nahm HoHyun,
Kim YongHyun,
Kim HyunSuk,
Chen Gang,
Ross Caroline A.
Publication year - 2019
Publication title -
advanced materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 10.707
H-Index - 527
eISSN - 1521-4095
pISSN - 0935-9648
DOI - 10.1002/adma.201903738
Subject(s) - materials science , thermal conductivity , electrolyte , epitaxy , thermal conduction , conductivity , condensed matter physics , thermoelectric effect , thin film , lattice (music) , thermodynamics , nanotechnology , composite material , electrode , chemistry , physics , layer (electronics) , acoustics
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 WO 3 thin films. Depending on the substrate, the lattice of epitaxial WO 3 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 ≈ 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.