Solute effects on electromigration

Abstract

The kinetics of the solute effect on solvent electromigration and the vacancy-flow effect on solute electromigration have been analyzed. The Howard and Manning type analysis has been applied to the diffusion data of a number of solutes in Al, Cu, Ag, and Au for determining the required jumping-frequency ratios. The cross-term contributions to the electromigration flux are found to be negative for all the solutes analyzed, so the vacancy-flow effect reduces solute and solvent migration. However, the enhanced diffusivity of the solvent and the large effective charge of the solute overcompensate the negative vacancy-flow corrections. As a result, most of the solutes analyzed are predicted to enhance solvent electromigration except for Fe in Cu and Ag. The result is attributed to the particular behavior of the vacancy jumping around the impurity. Of particular interest also is that the predicted effect of Cu on Al in bulk crystal is inconsistent with the existing thin-film observations. © 1973 The American Physical Society.