Ballistic thermal transport in silicon nanowires

Jeremie Maire,Roman Anufriev,Masahiro Nomura

doi:10.1038/srep41794

Abstract

We have experimentally investigated the impact of dimensions and temperature on the thermal conductivity of silicon nanowires fabricated using a top-down approach. Both the width and temperature dependences of thermal conductivity agree with those in the existing literature. The length dependence of thermal conductivity exhibits a transition from semi-ballistic thermal phonon transport at 4 K to fully diffusive transport at room temperature. We additionally calculated the phonon dispersion in these structures in the framework of the theory of elasticity and showed that the thermal conductance increases with width. This agrees with our experimental observations and supports the pertinence of using the modified phonon dispersion at low temperatures.

Highlights

We have experimentally investigated the impact of dimensions and temperature on the thermal conductivity of silicon nanowires fabricated using a top-down approach
The length dependence of thermal conductivity exhibits a transition from semi-ballistic thermal phonon transport at 4 K to fully diffusive transport at room temperature
We have investigated different heat transport regimes in silicon NWs at different temperatures

Summary

Introduction

We have experimentally investigated the impact of dimensions and temperature on the thermal conductivity of silicon nanowires fabricated using a top-down approach. Specular phonon scattering leads to non-diffusive heat propagation called “ballistic”, meaning the absence of scattering mechanisms other than specular phonon reflections on the surfaces Such ballistic heat transport has been demonstrated at room temperature in bulk[20,21] and in suspended silicon thin films[22]. We address the modifications to the phonon dispersion in these NWs and show that they can explain the stronger reduction in thermal conductivity of NWs at 4 K, as compared to that of the membrane These results demonstrate the possibility of using phonon wave properties to control heat transport at the nanoscale.

Results

Discussion

Conclusion