P. S. Weiss* and D. M. Eigler*
Physical Review Letters 69, 2240 (1992).
We have recorded real-space images of Xe atoms adsorbed on a 4K 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 Ångstroms 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. Thus, we have imaged the initiation of the growth of a surface overlayer, and have identified the sites at which this growth begins.