Tuning the thermal conductivity of silicon nanowires by surface passivation

Céline Ruscher, Robinson Cortes-Huerto, Robert Hannebauer, Debashish Mukherji, Alireza Nojeh, A. Srikantha Phani

Published 2023-04-23Version 1

We study thermal conductivity $\kappa$ of surface passivated silicon nanowires (SiNWs) using large scale molecular dynamics simulations. Consistent with the experimental observations, we find that bare SiNWs become unstable, especially for small cross-section width $w$. We correlate this behavior with a large excess energy $\Delta$ of the surface atoms with respect to bulk silicon and propose a practically relevant method that uses $\Delta$ as a guiding tool to obtain stable SiNWs. The surface stabilization is achieved by the surface passivation of the silicon atoms with hydrogen or oxygen. As an added advantage, $\kappa$ of a SiNW can be further tuned by changing the concentration $c$ of the passivated atoms. By analyzing the phonon band structures via spectral energy density (SED), we discuss separate contributions from the surface and the core to $\kappa$ and show how passivation can help tune the stiffness of SiNWs.