Impact of roughness on heat conduction involving nanocontacts

The impact of surface roughness on conductive heat transfer across nanoscale contacts is investigated by means of scanning thermal microscopy. Silicon surfaces with the out-of-plane rms roughness of ∼0, 0.5, 4, 7, and 11 nm are scanned both under air and vacuum conditions. Three types of resistive SThM probes spanning curvature radii over orders of magnitude are used. A correlation between thermal conductance and adhesion force is highlighted. In comparison with a flat surface, the contact thermal conductance can decrease as much as 90% for a microprobe and by about 50% for probes with a curvature radius lower than 50 nm. The effects of multi-contact and ballistic heat conduction are discussed. Limits of contact techniques for thermal conductivity characterization are also discussed.