Thermal conductivity of the n = 1–5 and 10 members of the (SrTiO3)nSrO Ruddlesden–Popper superlattices

Abstract

Unlike many superlattice structures, Ruddlesden–Popper phases have atomically abrupt interfaces useful for interrogating how periodic atomic layers affect thermal properties. Here, we measure the thermal conductivity in thin films of the n = 1–5 and 10 members of the (SrTiO3)nSrO Ruddlesden–Popper superlattices grown by molecular-beam epitaxy and compare the results to a single crystal of the n = 1 Ruddlesden–Popper SrLaAlO4. The thermal conductivity cross-plane to the superlattice layering (k33) is measured using time-domain thermoreflectance as a function of temperature and the results are compared to first-principles calculations. The thermal conductivity of this homologous series decreases with increasing interface density. Characterization by x-ray diffraction and scanning transmission electron microscopy confirms that these samples have a Ruddlesden–Popper superlattice structure.

Structural and Thermoelectric Properties of Gd2−2xSr1+2xMn2O7 Double-Layered Manganites

“…The layered structure of the RP compounds would enhance the phonon scattering at the interfaces between the A 2 O 2 layer and perovskite layer and consequently reduce κ , which is of great importance for TE materials. Investigation on thermal conductivity in the thin films of the m = 1–5 and 10 members of the (SrTiO 3 ) m SrO RP superlattices showed that the m = 2 member had the lowest κ in this RP homologous series [ 9 ]. Significant reduction of κ values was observed in the layered (Sr 1− x RE x ) m +1 Ti m O 3 m +1 ( m = 1, 2) [ 10 ] and La 2−2 x Ca 1+2 x Mn 2 O 7 (0.75 ≤ x ≤ 1.0) [ 11 ] due to the intrinsic superlattice structure as compared to their perovskite phases.…”

Strain generated by the stacking faults in epitaxial SrO(SrTiO3) N Ruddlesden–Popper structures

“…Among others, RP phases based on STO or other perovskite oxides (SrRuO 3 , LaCuO 3 , NdNiO 3 etc.) exhibit very low dielectric losses (Dawley et al, 2020b;McCarthy et al, 1969;Lee et al, 2013b), strong magnetoresistance (Moritomo et al, 1996), improper ferroelectricity (Birol et al, 2011;Pitcher et al, 2015;Oh et al, 2015;Benedek et al, 2015) or low thermal conductivity, with attractive prospects for the design of highefficiency thermoelectric modules (Balachandran et al, 2017;Dawley et al, 2021;Wise et al, 2001;Kamba et al, 2003).…”

Tuning Coherent-Phonon Heat Transport in LaCoO3/SrTiO3 Superlattices

“…Instead, these authors reported a constant interfacial resistance ≈2 × 10 –9 K m 2 /W. A monotonic decrease was also observed in the thermal conductivity of (SrTiO 3 ) n SrO Ruddlesden–Popper superlattices, as the interface density increases …”

“…A monotonic decrease was also observed in the thermal conductivity of (SrTiO 3 ) n SrO Ruddlesden–Popper superlattices, as the interface density increases. 23 …”

“…A monotonic decrease was also observed in the thermal conductivity of (SrTiO 3 ) n SrO Ruddlesden−Popper superlattices, as the interface density increases. 23 Transition-metal 3d oxides are quite ionic, and sharp interfaces may introduce polar discontinuities in some cases, whose energy penalty can be resolved through ionic intermixing. 24 This, together with their shorter l and λ than semiconductors, should make them more sensitive to interfacial defects.…”