Chemical transformations of self-assembled monolayers by low energy reactive ion beam bombardment

Abstract

Reactions of low energy (500 eV) beams of CCl₄⁺, O₂⁺ and PCl₃⁺ on hydrocarbon and fluorocarbon self-assembled monolayer surfaces are shown to produce chemically modified monolayers. The surfaces before and after the reaction have been characterised by X-ray photoelectron spectroscopy. It is suggested that the surface modification involves the substitution of the ion/ surface reaction sites with the appropriate reagent. It appears that the ion beam penetration is minimal and the extent of modification is limited to the top layers of the surface. It is found that the hydrocarbon surface is more reactive than the fluorocarbon surface towards oxygen ions. Upon prolonged bombardment, the alkyl chains desorb and the exposed substrate reacts with the ion beam. It is proposed that extremely thin molecular surfaces of distinct functionality can be made by low energy reactive ion beam bombardment on SAM surfaces.