Self-diffusion on Pd(111)

The barrier and prefactor for self-diffusion of Pd on Pd(111) are derived f rom 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 othe r fcc(111) transition metals - does not support an occupied free-electron l ike surface state. An exceptionally high prefactor of 6 x 10(16) s(-1) is o bserved, indicating a large entropic contribution to diffusion in accordanc e with the Meyer-Neldel compensation law. (C) 2000 Elsevier Science B.V. Al l rights reserved.