Impact on Thermal Conductivities of Nanostructured Bismuth Telluride Based Thin Films

Nanostructured bismuth telluride based thin films, including nanoparticle and nanocrystalline have been prepared and measured their thermal conductivities. These thin films exhibit an average grain size of from 10 nm to 150 nm. The cross-plane thermal conductivities are measured by 3-omega method at 300 K. The determined nanostructured bismuth telluride thermal conductivities are 0.18 W/(m·K) and nanoparticle bismuth telluride thin film thermal conductivities are from 0.61 W/(m·K) to 0.80 W/(m·K). As compared with bulk alloys at the same atomic composition, both the nanoparticle and nanocrystalline thin films exhibit a reduction in the thermal conductivity. For more detail analysis, the reduction of the thermal conductivity is examined by a simplified phonon gas model on single crystal of bulk bismuth telluride, antimony telluride and bismuth selenide, The analytical model is consistent with the experimental results, and thus we consider that the thermal conductivity is reduced by the strong phonon scattering.