Dislocation resistivity in Cu: dependence of the deviations from Matthiessen's rule on temperature, dislocation density and impurity content

Measurements of dislocation resistivity and the deviations from Matthiessen's rule (DMRs) are reported for polycrystalline Cu samples with various dislocation densities, impurities and phonons. Since this DMR can reach the same order of magnitude as the dislocation resistivity itself, its quantification is essential in using the electrical resistivity for dislocation density measurement. In the framework of the classical two-group model, a formula for the DMR is derived for the three independent scatterers. The fits by this formula are satisfactory provided that isotropic phonon scattering is chosen for samples with high dislocation densities. While samples with a high purity (residual resistivity ratio (RRR)>or=300) show dislocation scattering anisotropies A_dis approximately=0.1 irrespective of dislocation density, the more impure material (purity 99.99%) (RRR=130) exhibits a significant decrease in A_dis at low dislocation densities, indicating some contribution of enhanced strain fields in the dislocation structure. This leads to an enhanced DMR contribution in this material and makes the determination of the dislocation density N by the electrical resistivity method less reliable. Nevertheless, in the whole purity range considered, the electrical resistivity yields at least the same measuring resolution as TEM of about Delta N approximately=1*10⁹ cm^-2, but a better performance for high dislocation densities up to the order of 10¹⁴ cm^-2.