Planar distribution measurement of cross-plane thermal diffusivity for microscale films using laser spot periodic heating technique

Abstract

Thin-film materials are widely used in the field of thermal management, but the characterization of their thermophysical properties on the microscale is still challenging. In this work, the planar distribution of the cross-plane thermal diffusivity for microscale films is measured utilizing the location-variation and frequency-variation methods based on a laser spot periodic heating technique. A laser beam is focused on the film surface for periodic heating, while a thermocouple collects the temperature rise signal from the back surface. The in-plane thermal diffusivity is determined employing the phase lag spatial distribution of the temperature rise. The cross-plane thermal diffusivity is derived after correcting the frequency dependence of phase lag using the bias phase, thereby eliminating the effect of thermal contact resistance at the thermocouple junction. The accuracy of this method is verified by measuring the thermal diffusivity of standard anisotropic polyester and isotropic stainless-steel films. Finally, the planar distribution of cross-plane thermal diffusivity of microscale stainless-steel and reduced graphene oxide films are successfully measured, bridging the gap left by the infrared lock-in thermography technique.