The effect of impurities upon grain boundary diffusion in thin films on Si substrates was investigated by using internal friction techniques. The impurities were introduced into the films by controlled diffusion from a thin layer, of the corresponding element, which had been evaporated onto the film. A well-defined relaxation peak was observed, except in the case of Ti. It was found that Cu, W and Pt increased the activation energy for grain boundary diffusion, as deduced from the peak position, to values of between 0.85 and 1.0eV; as compared to the original value of 0.55eV. The addition of Au had no detectable effect.

H.G.Bohn, C.M.Su: Materials Science Forum, 1993, 119-121, 273-8