Self-diffusion on Pd(111)

The barrier and prefactor for self-diffusion of Pd on Pd(111) are derived from scanning tunneling investigations of the homoepitaxial growth of Pd/Pd(111). The barrier for diffusion is found to be 350 meV. This is the highest value observed so far for self-diffusion on a fcc(111) metal surface. Such exceptional behaviour has recently been predicted, as Pd(111) — unlike other fcc(111) transition metals — does not support an occupied free-electron like surface state. An exceptionally high prefactor of 6×1016 s−1 is observed, indicating a large entropic contribution to diffusion in accordance with the Meyer–Neldel compensation law.