Study on Modulation Structure and Resistivity of Nanostructured Cu/Zr Metallic Multilayers

The Cu/Zr nanostructured metallic multilayers with constant modulation periods (λ = 25, 40 nm), covering a wide range of modulation ratio η spanning from 0.1 to 10.5, were deposited on the Si substrate by DC magnetron sputtering. By using the transmission electron microscopy and the four point probe method, the microstructure and size effects on the electrical resistivity (ρ) of Cu/Zr nanostructured multilayers were systematically investigated. It is revealed from the microstructural analysis that the modulation structure of Cu/Zr metallic multilayers is clear and the interfaces are distinguishable. Both the modulation periods λ and the modulation ratio η significantly influence the resistivity ρ of Cu/Zr multilayers. The smaller is the modulation periods λ, the greater is the resistivity ρ. Above a critical modulation ratio (η_C≈1) the resistivity is independent on the modulation ratio, below which the resistivity sharply increases with decreasing the modulation ratio. The combined Fuchs-Sondheimer and Mayadas-Shatzkes (FS-MS) model can be used to fit the experimental data well. It is found that when η>η_C, the resistivity of Cu/Zr multilayers is determined by the cooperative effect of grain boundary scattering and interface scattering; When η<η_C, the resistivity of Cu/Zr multilayers is mainly determined by grain boundary scattering.