MOLECULAR-DYNAMICS SIMULATION OF ADATOM FORMATION UNDER KEV-ION BOMBARDMENT OF PT(111)

Molecular-dynamics simulations are presented of defect formation in rare-gas ion bombardment of a Pt(111) surface with energies between 100 and 3000 eV, with a particular emphasis on adatom formation. Formation and equilibration of adatoms take considerably more time than sputtering, namely, between 1 and 10 ps for the systems studied. Adatoms have a considerable probability of originating from deeper than the first layer, e.g., 40% for 3-keV Xe bombardment. For energies above several hundred eV, a factor of 2-4 more adatoms than sputtered particles are found; at smaller energies this ratio is even higher. This behavior can be explained by assuming a lower barrier for adatom formation than for sputtering. The trends of adatom formation with bombarding energy and bombarding particle species coincide with recent experiments by Michely and Teichert [Phys. Rev. B 50, 11 156 (1994)].