Direct observation of diffusional creep via TEM in polycrystalline thin films of gold

Some transmission electron microscope observations are presented of the effects of stress in gold thin films, at moderately elevated temperatures. Stretching of the film by diffusional creep is demonstrated, and good agreement is obtained between theoretical predictions of the strain rate at the estimated stress level, provided that surface energy and surface diffusion. contributions are accounted for. Zero-creep stresses are found to be very large for these thin films, and the excess stress, over the zero-creep level, required to account for the observed strain rate, is relatively small. The growth of creep voids (cracks) in the films is attended by the formation of bridging whiskers under certain conditions and the whiskers also appear to grow by a diffusive mechanism. (C) 1998 Acta Metallurgica Inc. Published by Elsevier Science Ltd. All rights reserved.