In situ and interrupted-growth studies of the self-assembly of octadecyltrichlorosilane monolayers

We have examined the self-assembly process of octadecyltrichlorosilane on silicon using x-ray reflectivity. By comparing the commonly used "interrupted-growth" characterization technique with results obtained in situ, we have determined that quenching the growth and then rinsing and drying the sample introduces free area into the film, presumably by removal of non-cross-linked (physisorbed) molecules. Reintroduction of a quenched and rinsed film to solvent does not restore the thickness of the film to its previous value. We have also performed in situ growth studies over a range of concentrations. For all concentrations, we observe growth of islands of vertical molecules. The growth follows Langmuir kinetics, except at short times for low concentration solutions.