Remarkable Reduction of Thermal Conductivity in Silicon Nanotubes

TL;DR

This paper demonstrates that introducing small holes in silicon nanowires to form nanotubes significantly reduces their thermal conductivity, making them promising for thermoelectric applications.

Contribution

It is the first to show that tiny central holes in silicon nanowires can cause substantial thermal conductivity reduction, highlighting a new approach for thermoelectric material design.

Findings

A 1% cross section area hole reduces thermal conductivity by 35%.

Silicon nanotubes have about 33% of the thermal conductivity of nanowires.

Surface localization of vibrational modes explains the conductivity reduction.

Abstract

We propose to reduce the thermal conductivity of silicon nanowires (SiNWs) by introducing small hole at the centre, i.e. construct silicon nanotube (SiNT) structures. Our numerical results demonstrate that a very small hole (only 1% reduction in cross section area) can induce a 35% reduction in room temperature thermal conductivity. Moreover, with the same cross section area, thermal conductivity of SiNT is only about 33% of that of SiNW at room temperature. The spatial distribution of vibrational energy reveals that localization modes are concentrated on the inner and outer surfaces of SiNTs. The enhanced surface-to-volume ratio in SiNTs reduces the percentage of delocalized modes, which is believed to be responsible for the reduction of thermal conductivity. Our study suggests SiNT is a promising thermoelectric material with low thermal conductivity.