Giant heat transfer and its material dependence at the nanometer scale

We report on quantitative measurements of the absolute heat flux between a gold coated near-field scanning thermal microscope (NSThM) [2] tip and a planar gold sample at nanometer distances of 0.2 nm–7 nm. After a precise calibration procedure we are able to measure the local heat transfer in a quantitative way [1]. We find an extraordinary large heat flux which is more than five orders of magnitude larger than black-body radiation and three orders of magnitude larger than the values predicted by conventional theory of fluctuational electrodynamics [3–10]. Furthermore, we have investigated the influence of thin films of a dielectric material on the near-field mediated heat transfer at the fundamental limit of single monolayer islands on a metallic substrate. Spatially resolved measurements by Near-Field Scanning Thermal Microscopy are presented which are showing a distinct enhancement in heat transfer above NaCl islands compared to the bare Au(111) film [11]. Experiments at this sub-nanometer scale call for a microscopic theory beyond the macroscopic fluctuational electrodynamics used to describe near-field heat transfer today. The method facilitates the possibility to develop designs of nanostructured surfaces with respect to specific requirements in heat transfer down to a single atomic layer. These findings open up the possibility for a local surface modification by means of local heating, e.g., chemical modification and heat assisted magnetic recording, on a scale of a few nanometers.