High strength, epitaxial nanotwinned Ag films

Epitaxial silver films with (1 1 1) and (1 1 0) orientations were deposited by magnetron sputtering onto silicon (1 1 1) and (1 1 0) substrates, respectively. High density growth twins with an average spacing of a few nanometers are observed in the (1 1 1) oriented films, with twin boundaries oriented normal to the growth direction. Twins are observed in the (1 1 0) oriented films with a much lower twin density, and the twin boundaries are oriented 60° from the growth direction. The epitaxial nanotwinned Ag (1 1 1) and (1 1 0) films have respective indentation hardness values of ∼2 and 1 GPa. The influences of deposition parameters, stacking fault energy, and orientation of {1 1 1} planes on the formation of nanotwins are discussed.