Near-field heat transfer in a scanning thermal microscope

TL;DR

This paper investigates near-field heat transfer in a scanning thermal microscope, revealing deviations from classical theory at very small distances and proposing a model to better interpret experimental data.

Contribution

It introduces a model accounting for a material-dependent length scale where macroscopic dielectric descriptions break down, improving understanding of near-field heat transfer measurements.

Findings

Deviations from fluctuating electrodynamics at sub-10^-8 m distances

Proposed model aligns better with experimental data

Implications for interpreting scanning thermal microscope signals

Abstract

We present measurements of the near-field heat transfer between the tip of a thermal profiler and planar material surfaces under ultrahigh vacuum conditions. For tip-sample distances below 10-8 m our results differ markedly from the prediction of fluctuating electrodynamics. We argue that these differences are due to the existence of a material-dependent small length scale below which the macroscopic description of the dielectric properties fails, and discuss a corresponding model which yields fair agreement with the available data. These results are of importance for the quantitative interpretation of signals obtained by scanning thermal microscopes capable of detecting local temperature variations on surfaces.