Thickness-Dependent Thermal Conductivity of Annealed n-Bi2Te3 and p-Bi0.5Sb1.5Te3 Thin Films and Theoretical Analysis

Abstract

We report on the thickness-dependent thermal conductivities of n-type bismuth telluride ( Bi2Te3) and p-type bismuth antimony telluride ( Bi0.5Sb1.5Te3) thin films using modified Callaway and Sondheimer models. In this study, Bi2Te3 thin films with thicknesses of 100, 300, and 420 nm and Bi0.5Sb1.5Te3 thin films with thicknesses of 100, 300, and 780 nm were prepared using radio-frequency magnetron sputtering. The average thermal conductivities of the Bi2Te3 and Bi0.5Sb1.5Te3 thin films were determined to range from 0.38 to 0.96 and from 0.26 to 0.59W/m.K at 300 K, respectively, using the four-point-probe 3-omega method. The experimental results, including the thickness-dependent thermal conductivities of the Bi2Te3 and Bi0.5Sb1.5Te3 thin films, were further analyzed using both modified Callaway and Sondheimer models, which showed good agreement with the experimental results. This result implies that the thermal conductivity of the films is significantly reduced compared with the bulk values because of the enhanced phonon scattering in thin films. We have confidence that this theoretical analysis could significantly contribute to further understanding of thermal transport in thin films.