Scanning thermal microscopy of individual silicon nanowires

Thermal imaging of individual silicon nanowires (Si NWs) is carried out by a scanning thermal microscopy (SThM) technique. The vertically aligned 1.7 (micro)m long Si NWs are fabricated combining nanosphere lithography and metal-induced wet chemical etching. A thermal model for the SThM probe is then presented with two steps: a model out of contact which enables a calibration of the probe, and a model in contact to extract thermal parameters from the sample under study. Using this model and the experimental thermal images, we finally determine a mean value of the tip-to-sample thermal contact resistance and a mean value of the Si NWs thermal conductivity. No significant thermal conductivity reduction in comparison with bulk Si is observed for Si NWs with diameters ranging from 200 to 380 nm. However, the technique presented here is currently the only one available to perform thermal measurements simultaneously on an assembly of individual one-dimensional nanostructures. It enables to save time and to make a statistical processing of the thermal data in order to deduce a reliable mean thermal conductivity, even when the tip-to-sample thermal contact resistance cannot be considered neither negligible in comparison with the Si NW intrinsic thermal resistance nor constant from one Si NW to another