Using scanning tunneling microscopy, it was demonstrated that the nucleation density of Fe islands on the surface of nanoscale Pb films oscillated with the film thickness; providing a direct manifestation of the quantum size effect upon surface diffusion. The Fe adatom diffusion barriers were deduced to be 0.204 and 0.187eV on a 21- and 26-monolayer Pb film, respectively, by matching the kinetic Monte Carlo simulations to the experimental island densities. The effect was further illustrated by the growth of Fe islands on wedged Pb films, where the Fe island density was consistently higher on the odd-layer films than on the even-layer films in the thickness range of 11 to 15 monolayers.

Quantum Size Effect on Adatom Surface Diffusion. L.Y.Ma, L.Tang, Z.L.Guan, K.He, K.An, X.C.Ma, J.F.Jia, Q.K.Xue, Y.Han, S.Huang, F.Liu: Physical Review Letters, 2006, 97[26], 266102 (4pp)