Palladium diffusion into bulk copper via the (100) surface

Using low-energy electron microscopy, we measure the diffusion of Pd into bulk Cu at the Cu(100) surface. Interdiffusion is tracked by measuring the dissolution of the Cu(100)-c(2 x 2)-Pd surface alloy during annealing (T > 240 degrees C). The activation barrier for Pd diffusion from the surface alloy into the bulk is determined to be (1.8 +/- 0.6) eV. During annealing, we observe the growth of a new layer of Cu near step edges. Under this new Cu layer, dilute Pd remaining near the surface develops a layered structure similar to the Cu3Pd L1(2) bulk alloy phase.