Long delay time study of thermal transport and thermal stress in thin Pt film-glass substrate system by time-domain thermoreflectance measurements

Solid state thermoelectric devices are desirable for various sustainable applications. Most of these thin film devices are multilayered structures which requires thorough understanding of thermal transport and thermal stress in order to solve thermal issues. In this paper the experimental technology as well as theoretical model of long delay time pump-probe study with four different illumination configurations have been developed to comprehensively characterize the thermal transport and thermal stress of thin film, substrate and the interface. Furthermore, 94-nm-thick Pt film-glass substrate system has been studied by applying time-domain thermoreflectance measurements under four illumination configurations with high signal quality. The obtained time-dependent temperature signal is superposed by the effects of multilayered thermal transport and thermal stress spontaneously, and the corresponding theoretical predictions match well with the experimental data in the whole delay time range. The determined thermal conductivity of the Pt film shows significant size effect.