Shefford P. Baker¹, Nathaniel G. Rogers¹, Kenneth D. Shaughnessy¹; ¹Cornell University

High densities of twin boundaries parallel to close-packed directions in thin FCC and HCP films made using atom-by-atom deposition processes are of interest because of the potential to create materials with high strength and high ductility. However, to achieve these properties, such structures must be stable. Twin boundaries represent additional stored energy and can in principle assist in driving grain growth. We have developed methods to systematically vary the density of these defects during film deposition and show that the kinetics of grain growth are consistent with the expected nanotwin densities. Only under certain conditions are the microstructures stable. We discuss the magnitudes of the driving forces as well as strategies for stabilizing these structures.