Influence of synthesis conditions on the nanostructure of immiscible copper–silver alloy thin films

Far from equilibrium, immiscible nanocrystalline Cu–Ag alloy thin films of nominal composition Cu–30(±5) at.% Ag were deposited by co-sputtering. While films deposited at ∼300 K exhibit a two-phase mixture of face-centered cubic (fcc) Ag + fcc Cu, those deposited either at ∼100 K or at low power (∼40 W) exhibit an fcc Cu–25 at.% Ag solid solution, excess fcc Ag and small fractions of a metastable hexagonal (4H) Cu–Ag phase. Increasing the sputtering gas pressure leads to phase separation into fcc Cu, fcc Ag and metastable 4H Cu–Ag.