A Comparison between the Oxidation of Bulk Lead and that of Lead Deposits on Au(111) : an Auger Study

Abstract

A comparison of the oxidation of bulk lead with the oxidation of thin lead layers on an inert gold substrate provides important information on both processes, particularly on the transition from surface to bulk oxidation. The exposure to oxygen of bulk polycrystalline lead at room temperature rapidly produces an oxide layer which grows laterally as a film 2.0 ± 0.2 monolayers thick, followed by much slower oxygen uptake. The same oxide, PbO, forms for lead films of submonolayer to several monolayers thickness, deposited on a Au(111) surface. For lead deposits of less than one monolayer, the oxide grows with a thickness of one monolayer. Computer decomposition of the lead signal into metal and oxide components has been carried out using the Auger lineshapes for unoxidized metal and thick oxide as basis functions. This method provides chemical information similar to that obtained from X-ray photoelectron spectroscopy.