For Pd/Pd(111) an exceptionally high barrier (350 meV) for surface self-diffusion and a negative additional energy ΔE0ex0ex=0ex0ex-530ex0exmeV for step-down diffusion are measured. Both findings agree with the proposed role of free-electron-like surface states. Despite the negative value of ΔE layer-by-layer growth is not observed. This is related to the low preexponential factor for step-down diffusion. Preadsorption of oxygen increases ΔE but flattens the films. Again this is due to the prefactors for diffusion. The present results demonstrate the importance of entropic effects for diffusion and growth.
No takes yet. Share an insight, caveat, or question.
Steltenpohl et al. (2000) studied this question.