Radical Reactions with Organic Thin Films: Chemical Interaction of Atomic Oxygen with an X-ray Modified Self-Assembled Monolayer

Abstract

The interaction of an X-ray-modified self-assembled monolayer with a mixture of atomic and molecular oxygen (O/O2) has been studied using in situ X-ray photoelectron spectroscopy. Initially the reaction dynamics are dominated by the incorporation of new oxygen containing functionality at the vacuum/film interface. At intermediate O/O2 exposures, when a steady-state concentration of C−O, CO, and O−CO groups has been established, the production of volatile carbon-containing species, including CO2, is responsible for etching the hydrocarbon film. Upon prolonged O/O2 exposures, O atoms penetrate to the film/substrate interface, producing Au2O3 and sulfonate (RSO3) species. Under steady-state conditions, the thickness of the hydrocarbon film was reduced with an efficiency of ≈7.4 × 10-4 Å/impingent O atom while the average penetration depth of O atoms within the hydrocarbon film was determined to be ≈5.5 Å.