Manipulation of Phonon Thermal Transport in SrTiO ₃ -Based Superlattices through Structural Engineering

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Manipulation of thermal transport in oxides is exceedingly important for their thermal based applications. The continuous pursuit of the thermal conductivity limit calls for the rise of more effective thermal manipulation approaches while it remains a long-standing challenge. In this study, a demonstration of the effective manipulation of thermal transport in a series of Ruddlesden–Popper (SrTiO 3 ) n SrO superlattice films is reported. Structural engineering, including tailoring of interfaces and the boundary, is used, and an exceptionally low thermal conductivity of 0.65 W m −1 K −1 is achieved. A model derived from the Boltzmann equation is raised to elucidate thermal transport behaviors, which reveals the dominant roles of interface- and boundary-phonon scatterings in the thermal transport manipulation. In the modeling, a scattering coefficient is proposed to evaluate the effectiveness of interfaces in scattering phonons, in a quantitative measure. The growth quality of interfaces can also be reflected by this scattering coefficient. This approach holds promise to be extended to other oxide systems and will facilitate their thermal based applications, including thermal insulation and thermoelectricity.