Quantitative 3w-Scanning Thermal Microscopy: Modelling the AC/DC coupling and the sample heat conduction

A way to increase the Scanning Thermal Microscope (SThM) sensitivity in the harmonic 3w mode is to heat the probe with an AC current sufficiently high to generate a coupling between the AC and the DC signals. We detail in this paper how to properly take into account this coupling with a Wollaston-probe SThM. We also show how to link correctly the thermal conductivity to the thermal conductance measured by the SThM.