The Oscillatory Adsorption of Organosilane Films on Aluminium Oxide: Film Morphology using Auger Electron Spectromicroscopy

The morphology of Propyltrimethoxysilane films during the oscillatory growth mechanism is shown using Auger Electron Spectromicroscopy. While the link between oligomerisation of silane molecules on the substrate and the oscillatory growth mechanism has been proposed previously, here for the first time we show the presence of silane film islands through Auger Electron Spectromicroscopy elemental mapping of the substrate. Monitoring the morphology of the film at key peaks and throughout along the oscillatory curve reveals the formation of a stable thin, homogenous film along with the presence of islands approximately 20 mu m in diameter, whose numbers vary collectively during the adsorption/desorption mechanism. The measurable oscillations in silane substrate coverage has been directly linked to the repeated adsorption and desorption of silane islands on the aluminium substrate. The consequence of this mechanism is such that Propyltrimethoxysilane films behave most like a monolayer during the early stages of film growth, prior to siloxane oligomerisation.