Single silicon nanowires as inherent heaters and thermometers for thermal conductivity measurements

It is traditionally challenging to measure the thermal conductivity of nanoscale devices. In this Letter, we demonstrate a simple method for the thermal conductivity measurements of silicon nanowires by using the silicon nanowire under test as the thermometer and heater. The silicon nanowire (SiNW) arrays are patterned out of a silicon-on-insulator (SOI) wafer by standard microfabrication processes. The thermal conductivity of SiNWs with a width from 150nm to 400nm (while the thickness is fixed at 220nm) are measured in the temperature range of 20-200K. At low temperature range, the nanowire thermal conductivity exhibits a strong size dependency since the effective phonon mean-free path is dominated by the nanowire radial size. At high temperature range, the phonon mean-free path is significantly smaller than the nanowire radial size. The nanowire thermal conductivity is strongly temperature correlated and nearly independent of the nanowire size. Density function theory calculations are also performed on the SiNWs and the calculated thermal conductivity of SiNWs are largely consistent with the experimental data, showing that our method is valid for the thermal conductivity measurements of nanoscale devices.