Interior barriers and dimer nucleation on islands

On (1 1 1) islands of platinum as well as iridium self-adsorbed on (1 1 1) planes, it is now established that there are interior barriers impeding the movement of adatoms from the inner region to the steps of the island. We have carried out Monte Carlo simulations of adatoms migrating on such islands to establish the effect of interior barriers on the rate at which adsorbed atoms nucleate to form dimers rather than incorporate into the steps of the island. It is found that interior barriers significantly increase the rate at which dimers are created by collisions of two adatoms, and that the presence of additional step-edge barriers further raises the rate of dimer nucleation.