Development of a methodology for XPS curve-fitting of the Si 2p core level of siloxane materials

A procedure for obtaining reliable binding energies in XPS for the various chemical states of silicon has been described in the literature for some organosilicon compounds. This manuscript describes further development of this work by the analysis of siloxane compounds that model complex polysiloxane systems. The use of accurate and restrained binding energies will allow greater confidence in the curve-fitting of the Si 2p core level of industrially relevant coatings, which are typically featureless. The binding energy of a siloxy unit is known to increase when an oxygen atom replaces an alkyl group attached to the silicon atom. However, whereas previous work had estimated the binding energy shift between the M [(CH3)(3)SiO1/2], D [(CH3)(2)SiO2/2], T [(CH3)SiO3/2] and Q [SiO4/2] environments of silicon to be equal, or decreasing, this work has demonstrated a non-linear increase in binding energy with increasing oxygen substitution. Copyright (C) 2004 John Wiley Sons, Ltd.