Direct field-ion microscopic observations indicated that, at about 500K, an edge atom of a (111) step could ascend the step to the upper terrace, or dissociate to the lower terrace. The activation barrier to the ascending motion was estimated to be 1.51eV, whereas the barrier to dissociation was about 1.6eV. It was also found that in-layer atoms could even jump up to terrace sites, thus forming adatom-vacancy complexes, at unexpectedly low temperatures.

T.Y.Fu, Y.R.Tzeng, T.T.Tsong: Physical Review Letters, 1996, 76[14], 2539-42