Observations of individual atoms on metal surfaces have shown that the
diffusion potential at descending steps is not the simple repulsive b
arrier usually assumed in crystal growth. Instead, atoms may be held i
n asymmetric traps at step edges, and there are significant distortion
s of the potential near ascending steps. That the presence of step-edg
e traps instead of repulsive barriers can have a crucial effect on ato
mic kinetics is demonstrated by analyzing three processes important in
crystal growth: the lifetime of atoms before incorporating into a clu
ster, dissociation of atoms from lattice steps, and incorporation on v
icinal surfaces. (C) 1997 Elsevier Science B.V.