Structure and electrical conductivity of ultrathin Ni-Cu films

The structure, phase composition, morphology, and electrical conductivity of Ni-Cu alloy ultrathin films having a thickness of d = 1−10 nm and a Cu concentration of 10–95 at % have been studied. All films are shown to be fcc Ni-Cu alloys; they have an island structure with an island size of 1.5–2 nm in the as-deposited films and of about 20 nm in the films annealed to 700 K. The electrical conductivity of the films depends on their thickness and morphology. For films with d ≈ 1 nm, the electrical conductivity is thermally activated with an activation energy Ea ≈ 0.086−0.095 eV. Films with d > 3 nm exhibit the metallic temperature dependence of electrical conductivity with a positive temperature coefficient of resistivity.