Contributed Talk - Thursday, 16 September I 10:30 AM (CEST)
Claudiu Hapenciuc: "Improving the SThM accuracy in measuring thin films and bulk materials thermal conductivity"
National Institute for Lasers Plasma and Radiation Physics, Romania
Scanning Thermal Microscopy is a widely recognized technique for thermal conductivity measurements of bulk and nanostructured materials. Wollaston probes are presently used in contact or noncontact mode for thermal conductivity measurement. They can be reliably fabricated in the laboratory and offer an appropriate spatial resolution from few microns to hundreds of nanometers. A study is reported herewith on the errors that can affect the average temperature rise and related probe thermal resistance with direct impact on thermal conductivity evaluation, as a consequence of a contact point asymmetry. The new theoretical models proposed and its results can be used or adapted to any kind and size of hot probe. The study is based on the fin heat conduction equation applied on three regions of the probe: left, middle and right, in respect to the contact point. The thermal conductivity calculation for a thin film on substrate is simulated and the errors that raise from using an asymmetric contact point are inferred for the three values of the asymmetry. They are next compared to simulations obtained using a simplified model of heat transfer inside the probe and from probe to sample. The accuracy of the two models is comparatively analyzed in order to select the optimum one. The error in the simulated average temperature of the probe is investigated as a function of four probe diameters and lengths in order to assess the scaling influence. A general analysis of the errors affecting the thermal conductivity measurement is presented as a function of the experimental data spread out in the probe average temperature measurement. This analysis can serve as an eventual evaluation criterion of experimental precision of the method and improvement possibilities.
Keywords: SThM , hot probe, thermal conductivity, thermal resistance, heat transfer