Adhesion behaviour of self-assembled alkanethiol monolayers on silver at different stages of growth

Abstract

We studied the development of interfacial energy γ of alkanethiol self-assembled monolayers on Ag/mica substrates by force-displacement spectroscopy using an atomic force microscope. Self-assembled monolayers of decanethiol [CH₃ (CH₂)₉SH] and octadecanethiol [CH₃(CH₂)₁₇SH] were studied. The growth of the monolayer as a function of time was studied by an ellipsometer for three different concentrations of decanethiol and octadecanethiol. The thiols led to well-ordered self-assembled monolayer that showed atomic resolution images by lateral force microscopy mode. The behaviour of γ showed non-monotonic variation in stages of adsorption, which was more prominent for short chain length decanethiol. The γ reached a limiting value of 12 mJ m⁻² for decanethiol and 7 mJ m⁻² for octadecanethiol.