ADSORPTION AND ACCOMMODATION OF XE ON PT(111)

We have recorded real-space images of Xe atoms adsorbed on a 4-K Pt{111} surface. In the dilute coverage limit, we find nearly all the Xe atoms at step edges. From this observation we deduce a lower limit of hundreds of angstroms that Xe atoms scatter across the surface before becoming thermally accommodated. This result is in sharp contrast to previous studies of metal-atom adsorption on metal surfaces in which it is believed that a large fraction of the impinging atoms remain at their point of impact at low surface temperature. For Xe, once the step sites are nearly saturated, point defects on the Pt{111} surface nucleate the growth of compact, incommensurate, rotationally ordered Xe islands.