Internal friction associated with grain boundary diffusion in thin gold films

Using the vibrating reed technique an internal friction peak has been observed near 200°C (measurement frequency 245 Hz) in thin gold films on silicon substrates. Comparing with a previous study on bulk gold polycrystals using a low-frequency torsional pendulum (D. R. Mash and L. D. Hall, 1953, Trans AIME, 197, 937), it was found that though both peaks are attributed to grain boundary relaxation the peak in gold thin films with its activation energy of (0·87 × 0·03) eV and pre-exponential factor of 2·5 × 10 −(13 ± 0·3) s is more directly related to grain boundary diffusion. This difference is attributed to the much smaller grain sizes in the thin films compared to those in the bulk polycrystals.