Glass-Like Through-Plane Thermal Conductivity Induced by Oxygen Vacancies in Nanoscale Epitaxial La0.5Sr0.5CoO3-δ

Xuewang Wu, Jeff Walter, Tianli Feng, Jie Zhu, Hong Zheng, John F. Mitchell, Neven Biskup, Maria Varela, Xiulin Ruan, Chris Leighton, Xiaojia Wang

Research output: Contribution to journalArticle

7 Citations (Scopus)

Abstract

Ultrafast time-domain thermoreflectance (TDTR) is utilized to extract the through-plane thermal conductivity (ΛLSCO) of epitaxial La0.5Sr0.5CoO3− δ (LSCO) of varying thickness (<20 nm) on LaAlO3 and SrTiO3 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 ΛLSCO 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 ΛLSCO is rationalized by two main effects: (1) the nearly isotropic phononic thermal conductivity resulting from the imperfect OVO planes when δ is small; (2) the missing electronic contribution to ΛLSCO along the through-plane direction for these ultrathin LSCO films on insulating substrates.

Original languageEnglish (US)
Article number1704233
JournalAdvanced Functional Materials
Volume27
Issue number47
DOIs
StatePublished - Dec 15 2017

Fingerprint

Oxygen vacancies
Thermal conductivity
thermal conductivity
Glass
glass
oxygen
Substrates
Lattice mismatch
Ultrathin films
Tensile strain
accommodation
Oxides
Substitution reactions
Single crystals
substitutes
oxides
Electrons
single crystals
room temperature
electronics

Keywords

  • nanoscale epitaxial LSCO
  • oxygen vacancies
  • perovskite
  • thermal conductivity
  • time-domain thermoreflectance

How much support was provided by MRSEC?

  • Primary

Reporting period for MRSEC

  • Period 4

Cite this

Glass-Like Through-Plane Thermal Conductivity Induced by Oxygen Vacancies in Nanoscale Epitaxial La0.5Sr0.5CoO3-δ. / Wu, Xuewang; Walter, Jeff; Feng, Tianli; Zhu, Jie; Zheng, Hong; Mitchell, John F.; Biskup, Neven; Varela, Maria; Ruan, Xiulin; Leighton, Chris; Wang, Xiaojia.

In: Advanced Functional Materials, Vol. 27, No. 47, 1704233, 15.12.2017.

Research output: Contribution to journalArticle

Wu, Xuewang ; Walter, Jeff ; Feng, Tianli ; Zhu, Jie ; Zheng, Hong ; Mitchell, John F. ; Biskup, Neven ; Varela, Maria ; Ruan, Xiulin ; Leighton, Chris ; Wang, Xiaojia. / Glass-Like Through-Plane Thermal Conductivity Induced by Oxygen Vacancies in Nanoscale Epitaxial La0.5Sr0.5CoO3-δ. In: Advanced Functional Materials. 2017 ; Vol. 27, No. 47.
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abstract = "Ultrafast time-domain thermoreflectance (TDTR) is utilized to extract the through-plane thermal conductivity (ΛLSCO) of epitaxial La0.5Sr0.5CoO3− δ (LSCO) of varying thickness (<20 nm) on LaAlO3 and SrTiO3 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 ΛLSCO 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 ΛLSCO is rationalized by two main effects: (1) the nearly isotropic phononic thermal conductivity resulting from the imperfect OVO planes when δ is small; (2) the missing electronic contribution to ΛLSCO along the through-plane direction for these ultrathin LSCO films on insulating substrates.",
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T1 - Glass-Like Through-Plane Thermal Conductivity Induced by Oxygen Vacancies in Nanoscale Epitaxial La0.5Sr0.5CoO3-δ

AU - Wu, Xuewang

AU - Walter, Jeff

AU - Feng, Tianli

AU - Zhu, Jie

AU - Zheng, Hong

AU - Mitchell, John F.

AU - Biskup, Neven

AU - Varela, Maria

AU - Ruan, Xiulin

AU - Leighton, Chris

AU - Wang, Xiaojia

PY - 2017/12/15

Y1 - 2017/12/15

N2 - Ultrafast time-domain thermoreflectance (TDTR) is utilized to extract the through-plane thermal conductivity (ΛLSCO) of epitaxial La0.5Sr0.5CoO3− δ (LSCO) of varying thickness (<20 nm) on LaAlO3 and SrTiO3 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 ΛLSCO 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 ΛLSCO is rationalized by two main effects: (1) the nearly isotropic phononic thermal conductivity resulting from the imperfect OVO planes when δ is small; (2) the missing electronic contribution to ΛLSCO along the through-plane direction for these ultrathin LSCO films on insulating substrates.

AB - Ultrafast time-domain thermoreflectance (TDTR) is utilized to extract the through-plane thermal conductivity (ΛLSCO) of epitaxial La0.5Sr0.5CoO3− δ (LSCO) of varying thickness (<20 nm) on LaAlO3 and SrTiO3 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 ΛLSCO 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 ΛLSCO is rationalized by two main effects: (1) the nearly isotropic phononic thermal conductivity resulting from the imperfect OVO planes when δ is small; (2) the missing electronic contribution to ΛLSCO along the through-plane direction for these ultrathin LSCO films on insulating substrates.

KW - nanoscale epitaxial LSCO

KW - oxygen vacancies

KW - perovskite

KW - thermal conductivity

KW - time-domain thermoreflectance

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