Frequency domain analysis of 3ω-scanning thermal microscope probe-Application to tip/surface thermal interface measurements in vacuum environment

The characterization of material thermal properties at nanoscales remains a challenge even if progress was achieved in developing outstanding characterization techniques like scanning thermal microscopy (SThM). In the present work, we propose a detailed procedure based on the combined use of a SThM probe characterization and its Finite Element Method (FEM) modeling to recover in operando 3 omega measurements achieved under high vacuum. This approach is based on a two-step methodology: (i) a fine description of the probe's electrical and frequency behaviors in "out of contact" mode to determine the intrinsic parameters of the SThM tip and (ii) a minimization of the free parameter of our model, i.e., the contact thermal resistance, by comparing 3 omega measurements with the simulations of the probe operating "in contact mode." Such an approach allows us to measure thermal interface resistances between the tip and the surface. We applied our methodology to three different materials with known thermal properties: Si, SiO2 bulk materials, and a gold thin film. In addition, the FEM modeling provides insights into SThM thermal probes sensitivity, as a function of probe/sample interface resistance and the contact area to measure material thermal conductivity paving the way to quantitative SThM measurements.