Series study on the thermal transport properties of nanofilm by applying transient thermoreflectance method

With the continued size reduction and operation frequency increase in micro/nanoelectromechanical systems, heat accumulation has become more critical. It is crucial to carry out an in-depth investigation on the thermal transport properties of thin metal films, i.e., electron-phonon relaxation, thermal diffusivity and interfacial thermal resistance. In this paper, series study of the thermal transport properties of thin metal films have been performed by applying transient thermoreflectance method, including femtosecond and picosecond laser thermoreflectance systems. The electron-phonon coupling factor of thin gold films with different thickness have been measured by applying femtosecond laser thermoreflectance system. The results show that the electronphonon relaxation is nearly the same as that of bulk gold and independent of film thickness. The cross-plane thermal diffusivity of 95.3 and 200-nm-thick molybdenum film has been studied by applying the picosecond laser thermoreflectance system. The measurement results show that the cross-plane thermal diffusivity of molybdenum thin film decrease significantly compared to the corresponding bulk value and tends to increase as films become thicker.