Predictive Model for the Thermal Conductivity of Rough and Smooth Silicon Nanowires

The thermal conductivity of semiconductor nanowires (NWs) is significantly reduced with respect to their bulk counterparts. It decreases when the NW diameter is reduced and, in addition, it is dependent on the NW surface morphology, resulting in very low thermal conductivities for rough NWs. The thermal conductivity is a crucial physical magnitude for the thermal management of the nanodevices based on NWs; therefore, a great research effort has been focused in constructing theories that account for the thermal conductivity of semiconductor NWs. However, among all of these approaches, the possibility of predicting the value of the thermal conductivity of the NWs on the basis of the sole knowledge of the nature and morphology of the NWs is still lacking. We present herein a predictive approach for determining the thermal conductivity of both smooth and rough silicon NWs, based on a modified Callaway-Holland formalism. It correlates well with the existing experimental data, and greatly simplifies the complex evaluation of thermal conductivity at the nanoscale by means of simple mathematical expressions. These expressions allow for the estimation of the Si NW thermal conductivity for any combination of diameter and surface morphology parameters.