Wu, XuewangWalter, JeffFeng, TianliZhu, JieZheng, HongMitchell, John F.Biskup Zaja, NevenkoVarela Del Arco, MaríaRuan, XiulinLeighton, ChrisWang, Xiaojia2024-05-302024-05-302017-11-02X. 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, 17042331616-301X10.1002/adfm.201704233https://hdl.handle.net/20.500.14352/104604Ultrafast 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.engjournal article1616-3028https://doi.org/10.1002/adfm.201704233https://www.osti.gov/biblio/1415607open access538.9Nanoscale epitaxial LSCOOxygen vacanciesPerovskiteThermal conductivityTime-domain thermoreflectanceFísica de materiales2211 Física del Estado Sólido