Photoacoustic thermal characterization of low thermal diffusivity thin films

• Main Authors: K. Herrmann, N.W. Pech-May, M. Retsch
• Format: Article
• Language: English
• Published: Elsevier 2021-06-01
• Series: Photoacoustics
• Subjects: Thermal conductivity; Thermal wave; Thermal transport metrology; Photoacoustic characterization; Effusivity mismatch; Thermal diffusivity
• Online Access: http://www.sciencedirect.com/science/article/pii/S2213597921000082

The photoacoustic measurement technique is a powerful yet underrepresented method to characterize the thermal transport properties of thin films. For the case of isotropic low thermal diffusivity samples, such as glasses or polymers, we demonstrate a general approach to extract the thermal conductivity with a high degree of significance. We discuss in particular the influence of thermal effusivity, thermal diffusivity, and sample layer thickness on the significance and accuracy of this measurement technique. These fundamental thermal properties guide sample and substrate selection to allow for a feasible thermal transport characterization. Furthermore, our data evaluation allows us to directly extract the thermal conductivity from this transient technique, without separate determination of the volumetric heat capacity, when appropriate boundary conditions are fulfilled. Using silica, poly(methyl methacrylate) (PMMA) thin films, and various substrates (quartz, steel, and silicon), we verify the quantitative correctness of our analytical approach.