Thermal characterization of micrometric polymeric thin films by photoacoustic spectroscopy

In materials science, the knowledge of the thermal properties of thin films on thick substrates is crucial in determining the role of the film in the physical properties of the entire system. Even though the role of the film can be very important, the determination of its thermal properties is a challenging task due to the fact that its contribution to heat transfer is generally hard to single out from the influence of the substrate. Herein, a simple analytical methodology, based on the photoacoustic technique, useful in the thermal characterization of thin films on thick substrates, is presented. The approach is based on illuminating one side of the substrate with a modulated laser beam and monitoring the thermal contrast when a thin film is formed on the opposite side. This methodology allows to unambiguously determine the volumetric heat capacity of micrometric polymeric thin films. The limits of applicability of the method as well as the possibility of performing a full characterization of the thermal properties of the film are discussed.