Measurement of Thermal Diffusivity of thin Films by Thermal Pulse Method

Abstract

Thin polymer films are widely used as dielectric film, and the thermal diffusivity is one of critical parameters. The existing methods have great difficulties for measuring thermal diffusivity of thin films with thickness of several micrometers. The electric field distribution in a two-layer thin film with apparent difference in conductivity was measured by thermal pulse method. There should exist an interface between the two uniform electric field regions in the two-layer film under a low dc applied voltage. By Scale Transformation method, the frequency f corresponding to the position of the interface, which can be found in the (real-imag) distribution of original data. When we know frequency f and the layers thickness, the thermal diffusivity D can be calculated according to the relationship $z=(D/ \pi f)^{0.5}$. Thermal diffusivity D of polyethylene film with thickness 10 μm was measured. The measured thermal diffusivity D is very close to the literature. The proposal based on thermal pulse method can be an alternative way to measure thermal diffusivity of thin film, particularly for films less than 10 μm.