Radial thermal transport from heated silicon nanowires: Molecular dynamics simulations and compact engineering models

Because of their advantageous properties, silicon nanowires are considered as basic structures in many concepts of future electron devices. With the high energy density induced during manufacturing but also during operation, heat dissipation is a crucial point for both. While heat transport along the nanowire axis has been investigated already intensively, we note that heat dissipation occurs predominantly in radial direction. In this work, we investigated heat conduction in radial direction by molecular dynamics simulations. The effective thermal conductance for the thermal transport in radial direction increases approximately linearly with the radius of the nanowires and, in contrast to the axial thermal transport in nanowires, is almost independent of nanowire length. A reduction of the thermal conductivity in silicon by a factor of 1.5–3.5 near the silicon-to-oxide interface for the heat flow in radial direction was found. This reduction of the thermal conductivity is a manifestation of the Kapitsa thermal resistance at the silicon-to-oxide interface. Numerical results from molecular dynamics simulations were compared to literature results and comprised to analytical models that enable the time-efficient calculation of heat dissipation which include the specifics of the thermal transport in radial direction in nanowires including the Kapitsa resistance, localized phonon modes at the interface and dependences on the nanowire dimensions.