In this project we study quasi-ballistic heat conduction in semiconductor nanowires. By probing phonons transport in nanowires of different length, shapes, and chemical compositions, we try to demonstrate non-diffusive thermal transport that takes place at nanoscale. Moreover, we measure the thermal properties of nanowires at different temperatures and show how the ballistic heat conduction becomes stronger as temperature is decreased to 4 K. In general, this project aims to uncover the length and temperature ranges in which ballistic heat conduction can enhance heat dissipation in microelectronic devices.
The figure above summarizing our results showing ballistic heat conduction. (a) Thermal resistance measured on straight Si nanowires shows that the values deviate from linear dependence typical for diffusive transport, which indicates presence of ballistic thermal transport. (b) Thermal conductivity measured on straight nanowires is higher than that measured on serpentine nanowires, but this difference disappears above 200~K, which shows the range in which ballistic heat conduction occurs. (c) Heat focusing effect based on the ballistic thermal transport. Experimental results agree with Monte Carlo simulations