EXPERIMENTS ON ATOMIC-SCALE MECHANISMS OF DIFFUSION

Many substitutional impurities in crystalline solids diffuse by a hybrid mechanism involving a fast-migrating intermediate species. Nonequilibrium measurements of the migration frequency g and migration length-lambda for such an impurity can provide definitive data on atomic-scale diffusion mechanisms. We report the first experimental study to exploit this approach. The system investigated is B in crystalline Si. B is shown to diffuse predominantly via a migrating interstitial species B(i), generated by a kick-out reaction. The observed mechanism and energetics agree with recent total-energy calculations.