The interaction of H2O molecules with iron films studied with MIES, UPS and XPS

X-Ray Photoelectron Spectroscopy (XPS), Metastable Induced Electron Spectroscopy (MIES) and Ultraviolet Photoelectron Spectroscopy (UPS) were applied to study the interaction of H2O molecules with iron films. During the interaction with H2O molecules under ultrahigh vacuum conditions, an oxide film is formed on the iron surface. UPS and XPS still show metallic contributions, even for a surface which is exposed to about 10(3) L. The oxide film thickness amounts to about 1.8 nm. No hydroxide formation is observed at all, neither in UPS nor in MIES. Further impinging H2O molecules do not interact with the surface, because the oxide film inhibits the dissociation of impinging molecules. H2O exposure beyond 10(9) L does not lead to a significant increase of the oxide layer, which saturates at a thickness of 1.8 nm. In particular, no surface hydroxide is observed at this exposure. Neither XPS UPS nor MIES reveal any indication for this. (C) 2012 Elsevier B.V. All rights reserved.