Abstract
The heat of adsorption and sticking probability are measured versus
coverage for Cu and Pb adsorption on the MgO(100) surface pre-decorated
with surface hydroxyl groups, and compared to prior results on OH-free
MgO(100). The presence of OH increases the low-coverage heats of
adsorption of both Pb and Cu, but causes these heats to increase
more slowly with metal coverage as the metal particle size increases.
Measurements by Auger electron spectroscopy show that the Pb island
density increases and island size decreases at a given Pb coverage
with OH present. This explains the slower rise in heat of adsorption
with coverage when OH is present, since smaller islands of metal
bind the next metal atom more weakly. The initial sticking probability
of Pb is lower on. the OH-dosed surface, which we attribute to a
lower adsorption energy for the precursor state (isolated Pb adatoms).
This contrasts with Pb atoms in tiny clusters, which bind more strongly
to MgO(100) when OH is present. (C) 2002 Elsevier Science B.V. All
rights reserved.
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