Thermal Conductivity Anisotropy in Phonon Transport of Bi2Te3/Bi0.5Sb1.5Te3 Superlattice Film

Abstract

Nanoscale superlattice thin films generally exhibit larger phonon and electron scattering at the interface in the direction of the cross-plane of the samples. Therefore, it is very important to further detailed study of especially phonon transport of the superlattice films. Here, we report temperature dependent thermal conductivity anisotropy in phonon transport of Bi2 Te3 /Bi0.5 Sb1.5 Te3 superlattice thin films at 200–500 K. Thermal conductivity of these thin films for in- and cross-plane thermal conductivities were determined to be approximately 0.74 and 0.4 W m–1 K–1 at 200–500 K, respectively, clearly indicating ∼185% suppression in- and cross-plane thermal conductivities of the superlattice thin films with a large anisotropic behavior. Such large anisotropy in the thermal conductivity can be attributed to enhanced phonon scattering occurring at the interface of the Bi2Te3 and Bi0.5Sb1.5Te3 layer.