Observations on the influence of solute on grain boundary diffusion and electromigration

Abstract

Radioactive tracer diffusion data is presented which illustrates some of the more interesting questions that need to be further understood. For example, in Al, Cu and Au alloys, solute decreases the activation energy, Ql, for lattice diffusion while increasing Qb for boundary diffusion in the same test samples. Secondly, this is true only for diffusion in the alloy itself; for example, Qb for Cu in pure Al boundaries is 0.4 eV while for Cu in All%Cu alloy boundaries is 0.73 eV. Also, for Qb, Sn in pure Cu is 0.8 eV, Cu in pure Cu is 0.92 eV, but in the Cu2%Sn alloy Sn is 1.2 eV and Cu 1.39 eV quite substantial changes. Of note is the observation that solute atomic size does not appear to be the deciding feature. The systems selected for study represent smaller, larger and similar solute size for Cu in Al, Sn in Cu and Ta in Au, respectively. Preliminary work has been accomplished on measuring the electron energy loss (EELS) of Cu in Al2%Cu grain boundaries, specifically to observe the electronic structure...