Effect of barrier underlayer on diffusion and phase composition of Ni/Cu thin films under annealing

The influence of the 25-nm-thick Cr and V barrier layer on the diffusion and chemical composition formation in Ni/Cu bilayer films under annealing conditions was studied. Cu-Ni solid solution formation onset was found in both cases after annealing at 450°C, which led to constantan Cu 53 Ni 47 alloy formation at 550°C. Cr intense diffusion towards the outer surface followed by its oxidation and accompanied by porous defects formation through the whole film depth was revealed. The existence of slightly higher thermal stresses on V/substrate interface promoted faster Cu-Ni diffusion intermixing as compared to the Cr underlayer application.