Grain rotation in thin films of gold

We present transmission electron microscope observations of microstructural development in thin, fine-grained, columnar, 〈111〉 textured films of gold. In a sequential annealing experiment, we find that individual grains constantly rotate about the film normal in apparently random, and randomly changing directions. This contributes to the rearrangement of grain boundaries by allowing their individual energies to vary, thus promoting triple-line motion. We perform an analysis of the kinetics of grain rotation: assuming that its rate is limited by grain boundary diffusion, we obtain very good agreement between the observed and predicted rates and the rotation rate is predicted to be very sensitive to the grain size. A simple computer model is developed to investigate the structural consequences of grain rotation, which include reduction in the total grain boundary energy in a specimen, and changes in the populations of the various CSL-related boundaries.