Atomically resolved scanning tunneling microscopy study of the adsorption and dissociation of methylchloride on Si(001)

The room-temperature adsorption and dissociation of methylchloride (CH3Cl) on Si(001) using scanning tunneling microscopy has been studied. Fragments are identified by the symmetry of their binding on the underlying Si(001) lattice. Methylchloride adsorbs dissociatively at room temperature, yielding a methyl group and a chlorine atom bound to the surface. Chlorine atoms bind in a variety of geometries, the most common being two chlorine atoms bonded to a single silicon dimer (silicon monochloride dimers). When the surface is heated to 150 °C, all Cl rearranges to this monochloride-type bonding configuration, and images reveal the beginnings of monochloride island formation. The Cl:CH3 ratio on the surface is found to be approximately 2:1, implying that not all methyl groups are bound to the surface in the reaction.