Simultaneous measurement of thermophysical and mechanical properties of thin films

Thermophysical and mechanical properties of thin films are investigated using ultrashort laser pulses (200 fs), which upon incidence create a temperature rise and generate an ultrasonic wave at the sample surface. By monitoring the thin film's reflectivity response after the deposition of radiation energy, the bulk modulus and thermal diffusivity normal to the surface can be extrapolated from a single data set. The resulting data show cooling profiles that vary greatly from the well-known Fourier diffusion model and agree favorably with the parabolic two-step heat diffusion model. This method can also be used to characterize electron-lattice energy coupling phenomena. Experimental results from bulk samples of copper and platinum as well as thin-film platinum were utilized to determine the values of the thermal diffusivity, bulk modulus, and electron-phonon coupling factor. In addition, the thin film platinum samples were studied with two substrates, silicon and glass, to gain more knowledge of the substrate's effect on transport properties.