Two-Step Approach to the Formation of Organic Monolayers on the Silicon Oxide Surface

A new synthetic strategy has been developed for the formation of densely packed monolayers on oxide surfaces. This technique involves a simple two-step procedure in which the oxide surface is initially chlorinated and then exposed to alcohol molecules for monolayer formation via Si−O linkages. We demonstrate this approach with the formation of octadecanol (C18) monolayers on the oxide-terminated Si(111) surface. Characterization of the resulting C18H37O− monolayer by a combination of techniques reveals a densely packed film with partial disorder. At the highest surface coverage, the thickness of the film is determined to be 24 Å. Kinetics of monolayer growth is characterized by a fast initial step at low coverage; the rate constant decreases by 3 orders of magnitude when surface coverage approaches saturation.