Electronic Transport in Nanocrystalline Metals: A Study of Electrodeposited Nickel Foils

Abstract

The electrical resistivity (ρ), its temperature coefficient (a) and the thermoelectric power (S) has been studied at room temperature for nanocrystalline electrodeposited Ni foils prepared under different deposition conditions. With decreasing crystallite size, ρ increased, α decreased and S became less negative in agreement with the few previously reported results on other nanocrystalline metals. The temperature dependence of ρ was measured from 4.2 K to 300 K for some samples with small (≈50 nm) crystallite size. A large residual resistivity was observed and the temperature variation of ρ was also different from that of well-annealed, defect-free Ni with large crystallite size. It was concluded that the large residual resistivity cannot be completely ascribed to crystallite boundaries only but the presence of a high density of other types of lattice imperfections due to the nanocrystalline structure must also be assumed in the electrodeposited Ni foils whereas the different temperature behavior can be explained by considering that the electronic mean free path of the matrix is higher than the average crystallite size at low temperatures and the situation is reversed at room temperature.