On the mechanism of rapid mound decay

The observation of rapid mound decay events on Ag(lll) is reported. As in t he case of Cu(lll), the critical terrace width for the onset of the rapid d ecay corresponds to about six atom rows. For Ag(lll), this distance is inco mpatible with the surface state model proposed earlier for Cu(lll). A new m echanism for the rapid decay events is considered, which involves steps in close proximity. It is shown that the observed mean terrace width in the fi nal, rapid decay of a mound is well described by a combination of the rando m walk and shape fluctuations of the islands with the proposed local decay mechanism. Approximate activation energies for the new process are determin ed for Cu(lll) and Ag(lll). (C) 2000 Elsevier Science B.V. All rights reser ved.