The oxidation of clean polycrystalline lead surfaces has been investigated by the static mode of secondary ion mass spectrometry and X-ray photoelectron spectroscopy. The XPS Pb(4f 7 2) and O(1s) peaks indicate the immediate formation of the rhombic (yellow) form of PbO upon oxygen exposure, with no evidnece for an intermediate adsorbed oxygen moiety. Positive and negative ion static SIMS spectra were recorded in conjunction with the photoemission experiments, and the quantitative coverage information of XPS is used as an aid in the interpretation of the SIMS data. The O+, O2+, Pb+, PbO+, O-, O2-, PbO-, and PbO2- secondary ions were observed during the course of the oxidation, although the positive ion yields were too low to offer detailed information. Recent theoretical predictions of the cluster formation mechanism require considerable local atomic order of the surface to be maintained in the cluster. We therefore explain the immediate appearance of O2- and PbO2- clusters by invoking a nucleation mechanism for growth of the oxide.
All Science Journal Classification (ASJC) codes
- Condensed Matter Physics
- Surfaces and Interfaces
- Surfaces, Coatings and Films
- Materials Chemistry