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https://doi.org/10.1063/1.5044563
Title: | Compensated thermal conductivity of metallically conductive Ta-doped TiO2 | Authors: | Suh, Joonki Sarkar, Tarapada Choe, Hwan Sung Park, Joonsuk Venkatesan, T. Wu, Junqiao |
Issue Date: | 14-Jun-2018 | Publisher: | American Institute of Physics Inc. | Citation: | Suh, Joonki, Sarkar, Tarapada, Choe, Hwan Sung, Park, Joonsuk, Venkatesan, T., Wu, Junqiao (2018-06-14). Compensated thermal conductivity of metallically conductive Ta-doped TiO2. APPLIED PHYSICS LETTERS 113 (2). ScholarBank@NUS Repository. https://doi.org/10.1063/1.5044563 | Abstract: | Electrical and thermal conductivities of epitaxial, high-quality Ta-doped TiO2 (Ta:TiO2) thin films were experimentally investigated in the temperature range of 35-375 K. Structurally identified as the anatase phase, degenerate Ta doping leads to high electrical conductivity in TiO2, reaching >105 (?-m)?1 at 5 at. % of Ta, making it a potential candidate for indium-free transparent conducting oxides. In stark contrast, Ta doping suppresses the thermal conductivity of TiO2 via strong phonon-impurity scattering imposed by the Ta dopant which has a high mass contrast with Ti that it substitutes. For instance, the near-peak value shows a >50% reduction, from 9.0 down to 4.4 W/m-K, at just 2 at. % doping at 100 K. Interestingly, further Ta doping beyond 2 at. % no longer reduces the measured total thermal conductivity, which is attributed to a high electronic contribution to thermal conduction that compensates the alloy-scattering loss, as well as possibly the renormalization of phonon dispersion relation in the heavy doping regime originating from doping-induced lattice stiffening. As a result, at high Ta doping, TiO2 exhibits high electrical conductivity without much degradation of thermal conductivity. For example, near room temperature, 5 at. % Ta doped TiO2 shows over 3 orders of magnitude enhancement in electrical conductivity from undoped TiO2, but with only less than 10% reduction in thermal conductivity. The metallic Ta:TiO2 maintaining reasonable good thermal conductivity might find application in energy devices where good conduction to both charge and heat is needed. © 2018 Author(s). | Source Title: | APPLIED PHYSICS LETTERS | URI: | https://scholarbank.nus.edu.sg/handle/10635/168501 | ISSN: | 00036951 10773118 |
DOI: | 10.1063/1.5044563 |
Appears in Collections: | Staff Publications Elements |
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