A formation mechanism for ultra-thin nanotwins in highly textured Cu/Ni multilayers

High density nanotwins with average twin thickness varying from 3 to 6 nm are formed in sputtered highly (111) textured Cu/Ni multilayers, when individual layer thickness is 25 nm or less. Twin interfaces are normal to growth direction. Both maximum twin thickness and volume fraction of twins vary with the individual layer thickness. Coherency stress plays an important role in tailoring the formation of nanotwins. Nanotwins compete with misfit dislocations in accommodating elastic strain energy in epitaxial Cu/Ni multilayers.