| Résumé | Cyclopropyl methyl ketone molecules react at single dangling bonds on an H-terminated Si(100) surface to form a metastable radical species attached via the oxygen atom. While the adsorbate has the capacity to abstract an H atom from an adjacent surface site, in analogy with the previously studied reaction of styrene, it appears not to do so. Rather, the cyclopropyl ring opens, thereby shifting the radical to a position distant from the point of attachment. H-abstraction then occurs from one of a variety of surface sites within range of the radical. The surface dangling bond created by abstraction allows the process to repeat, leading to the creation of a contiguous string of molecules attached to the surface. The assembly process follows a meandering path unlike in the case of styrene where H-abstraction is restricted to adjacent surface sites, resulting in straight multimolecular assemblies. This result hints at an opportunity to gain control over growth direction through judicious addition of constraints within the ring-opened radical adsorbates. Also, because the unimolecular rates of such ring opening reactions have been well characterized ("radical clocks") we anticipate that in the future, the kinetics of the self-directed growth process may be determined. |
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