Microstructure and electrical transport property of Fe/Cu nanoscale multilayered materials

The microstructures and electrical conductivity (σ) at room temperature of Fe/Cu multilayered material, which was prepared by the electron-beam physical-vapor-deposition technique, were investigated to understand the dependence of σ on the bilayer thickness (Λ=d _Fe+d _Cu) and the sublayer thickness ratio (χ=d _Fe/Λ), where d is the sublayer thickness. Satellite peaks in the x-ray diffraction spectra were observed, indicating a layered structure in the multilayered material. The specimen was polycrystalline, and the in-plane grain size is independent of the sublayer thickness. σ at a fixed χ increases with increasing Λ, and keeps nearly constant when Λ is larger than 30 nm. σ at a fixed Λ decreases linearly with increasing χ. The size dependence of σ is explained using a model that takes into account scattering by the sublayer interfaces and the grain boundaries. The scattering at interfaces and grain boundaries is thought to be the dominant mechanism for the size dependence of σ on Λ when d _Fe is smaller and larger, respectively, than the estimated electron mean free path in the Cu sublayer.