RT Journal Article
T1 Glass‐like through‐plane thermal conductivity induced by oxygen vacancies in nanoscale epitaxial La_0.5Sr_0.5Co_O3-δ
A1 Wu, Xuewang
A1 Walter, Jeff
A1 Feng, Tianli
A1 Zhu, Jie
A1 Zheng, Hong
A1 Mitchell, John F.
A1 Biskup Zaja, Nevenko
A1 Varela Del Arco, María
A1 Ruan, Xiulin
A1 Leighton, Chris
A1 Wang, Xiaojia
AB Ultrafast time-domain thermoreflectance (TDTR) is utilized to extract the through-plane thermal conductivity (Lambda(LSCO)) of epitaxial La_0.5Sr_0.5Co_O3-delta (LSCO) of varying thickness (<20 nm) on LaAlO_3 and SrTiO_3 substrates. These LSCO films possess ordered oxygen vacancies as the primary means of lattice mismatch accommodation with the substrate, which induces compressive/tensile strain and thus controls the orientation of the oxygen vacancy ordering (OVO). TDTR results demonstrate that the room-temperature Lambda(LSCO) of LSCO on both substrates (1.7 W m(-1) K(-1) are nearly a factor of four lower than that of bulk single-crystal LSCO (6.2 W m(-1) K(-1). Remarkably, this approaches the lower limit of amorphous oxides (e.g., 1.3 W m(-1) K-1 for glass), with no dependence on the OVO orientation. Through theoretical simulations, origins of the glass-like thermal conductivity of LSCO are revealed as a combined effect resulting from oxygen vacancies (the dominant factor), Sr substitution, size effects, and the weak electron/phonon coupling within the LSCO film. The absence of OVO dependence in the measured Lambda(LSCO) is rationalized by two main effects: (1) the nearly isotropic phononic thermal conductivity resulting from the imperfect OVO planes when delta is small; (2) the missing electronic contribution to Lambda(LSCO) along the through-plane direction for these ultrathin LSCO films on insulating substrates.
PB Wiley
SN 1616-301X
YR 2017
FD 2017-11-02
LK https://hdl.handle.net/20.500.14352/104604
UL https://hdl.handle.net/20.500.14352/104604
LA eng
NO X. Wu, J. Walter, T. Feng, J. Zhu, H. Zheng, J. F. Mitchell, N. Biškup, M. Varela, X. Ruan, C. Leighton, X. Wang, Adv Funct Materials 2017, 27, 1704233
NO National Science Foundation (US)
NO U.S.Department of Energy
NO National Natural Science Foundation of China
NO Ministerio de Economía y Competitividad (España)
NO European Commission
DS Docta Complutense
RD 9 abr 2025