Dynamics of proton transfer reactions on silicon surfaces: OH-dissociation of methanol and water on Si(001)

Abstract

The reaction dynamics of methanol and water on Si(001) were investigated by means of molecular beam techniques. The initial sticking probability s0 was determined as a function of the kinetic energy of the incoming molecules, Ekin, and surface temperature, Ts. For both, methanol and water, a nonactivated reactional channel was observed; the dynamics were found to be determined by the reaction into the datively bonded intermediate state. A low conversion barrier was deduced for the conversion from this intermediate into the final state. It is attributed to the reaction mechanism, which proceeds via proton transfer from the OH-group of the datively bonded molecules to a Si surface atom. Despite this low conversion barrier, adsorption into the intermediate and further reaction via proton transfer were found to be largely decoupled.