Core level and valence band XPS investigations of phosphorus oxygen compounds and the formation of thin oxide-free phosphate films on metal surfaces

The research presented in this dissertation is part of an on going study in the Sherwood research group focused on the preparation of novel surface chemistries on metal surfaces. The technique used to investigate the chemical compositions of these surfaces is X-ray Photoelectron Spectroscopy (XPS). The main purpose of this research is two-fold, firstly to investigate the formation of new surface films and secondly to probe the extent to which valence band XPS is able to distinguish subtle differences in surface chemistry.; The formation of new oxide-free phosphate type films on the surface of titanium, copper and aluminum metals is discussed. Previous studies in our group have included the formation of oxide-free orthophosphate films on aluminum, iron and copper. These studies are continued and extended to include the formation of oxide-free phosphite hypophosphite, and acid phosphate films. Two different methods for the formation of these films will be shown. Valence band XPS spectra are interpreted by comparison with spectra generated from band structure and X-alpha cluster calculations. What makes the phosphate films studied in our group unique is the fact that they are oxide-free being bonded directly to the metal surface compared to the mixed phosphate oxide films currently in use.; It will also be shown that it is possible to distinguish between a number of similar sodium phosphate compounds using valence band XPS in combination with band structure and X-alpha cluster calculations. Furthermore it is shown that valence band XPS can be used to differentiate between three different crystal structures of phosphorus pentoxide. The spectral differences are highlighted by the use of difference spectra, with the principal features of the difference spectra being reproduced by difference spectra of spectra calculated from the band structure calculations.