Temperature-dependent thermal conductivity of MBE-grown epitaxial SrSnO₃ films

As an ultrawide bandgap (∼4.1 eV) semiconductor, single crystalline SrSnO₃ (SSO) has promising electrical properties for applications in power electronics and transparent conductors. The device performance can be limited by heat dissipation issues. However, a systematic study detailing its thermal transport properties remains elusive. This work studies the temperature-dependent thermal properties of a single crystalline SSO thin film prepared with hybrid molecular beam epitaxy. By combining time-domain thermoreflectance and Debye-Callaway modeling, physical insight into thermal transport mechanisms is provided. At room temperature, the 350-nm SSO film has a thermal conductivity of 4.4 W m⁻¹ K⁻¹, ∼60% lower than those of other perovskite oxides (SrTiO₃, BaSnO₃) with the same ABO₃ structural formula. This difference is attributed to the low zone-boundary frequency of SSO, resulting from its distorted orthorhombic structure with tilted octahedra. At high temperatures, the thermal conductivity of SSO decreases with temperature following a ∼T^−0.54 dependence, weaker than the typical T⁻¹ trend dominated by the Umklapp scattering. This work not only reveals the fundamental mechanisms of thermal transport in single crystalline SSO but also sheds light on the thermal design and optimization of SSO-based electronic applications.