The oxidation of submonolayer deposits of Pb on Cu(111); differences between the oxide at the Pb island edges and the stoichiometric surface oxide

Abstract

The oxidation of monolayer and submonolayer amounts of Pb deposited on Cu(111) was studied by XPS and work function changes. The binding energy (BE) of the 4 f 7 2 emission of the oxidized Pb decreases as the oxidation progresses. For a given percentage of oxidation the binding energy (BE) of the oxide also depends on the Pb coverage. For example, for a Pb coverage of 0.1 monolayers oxidized up to 40%, the BE is 0.20 ± 0.03 eV larger than for 1.0 monolayers with the same degree of oxidation. The experimental data are consistent with the existence of two different surface oxides. One of them involves Pb atoms with low atomic coordination such as edge atoms in the Pb islands.