Study of the formation dynamics of self-assembled alkanethiol monolayers by ellipsometry

The motivation of the present work is our research on a cantilever-based chemical sensor. We are addressing the question of the source of the surface stress on a gold-coated cantilever due to alkanethiol adsorption. By simultaneously measuring layer thickness and cantilever stress during alkanethiol monolayer self-assembly, the aim is to gain some insight on where the surface stress comes from. The technique we used to monitor layer thickness is ellipsometry. The ellipsometer is used to measure, in situ, the formation dynamics of self-assembled alkanethiol monolayers under different conditions. The thickness evolution is interpreted in terms of monolayer phases (lying-down and standing-up). During these experiments, the ellipsometer is proven to have Angstrom resolution. Following our objectives, a combined stress-thickness set-up is designed and built. Preliminary results are presented while further investigations are currently being made.