Influence of overlayer thickness on the density of Lomer dislocations in nanoscale Ni-Cu bilayer thin films

We report on the evolution of the spacing and the character of misfit dislocations with increasing Ni overlayer thickness at an (001) Ni-Cu interface. At low Ni overlayer thicknesses (3 and 5 nm), most of the interface dislocations are 60degrees 1/2<110> glide dislocations, while Lomer edge dislocations constitute only about 5% of the total interface dislocation content. At a 13 nm Ni overlayer thickness, the fraction of Lomer dislocations increases to approximately 40% of the total content. This dramatic increase in the fraction of Lomer dislocations is likely related to a rebound mechanism which initiates at some critical thickness between 5 and 13 nm.