By using the vibrating reed technique, an internal friction peak was detected near to 200C at a measurement frequency of 245Hz in thin Au films on Si substrates. A comparison was made with a previous study, of bulk Au polycrystals, which had been made by using a low-frequency torsional pendulum. It was found that, although both peaks were attributed to grain boundary relaxation, the peak in thin Au films (with an activation energy of 0.87eV and pre-exponential factor of 2.5 x 10-13s) was more directly related to grain boundary diffusion. This difference was attributed to the effect of the much smaller grain sizes of the thin films as compared with those of the bulk polycrystals.

A.W.Zhu, H.G.Bohn, W.Schilling: Philosophical Magazine A, 1995, 72[3], 805-12