Current-induced marker motion in gold wires

Abstract The motion of light transverse scratches, used as markers, has been observed on the surface of gold wires carrying current densities of about 104 A/cm2 for periods of several days. Clear evidence for a mass transport caused by momentum exchange with the electron current is shown by the magnitude and direction of the marker motion—several microns a day in some cases and always toward the cathode. This motion is exhibited by scratches on the central portion whose temperature varied from 850°C to 1000°C. Water cooling maintained the ends of the wires near room temperature. In agreement with a simplified theory the marker motion appears to be proportional to the current density and the self-diffusion constant. Possible applications of this technique include (1) the indirect determination of the activation energy for diffusion and (2) the investigation of the strength of interaction between the electrons and those lattice defects which constitute the activated complexes for atom jumping. In this case a value of 2μ ohm-cm/per cent was indicated for the “specific resistivity” of the diffusing atom in gold.