Thermal dissociation of CO molecules and carbon incorporation on the Si(111)-(7 x 7) surface

•Thermal dissociation of CO molecules adsorbed on the Si(111)-7  ×  7 surface.•Incorporation of Carbon atoms into Si(111)-7  ×  7.•Scanning tunneling microscopy experiments and density-functional theory calculations.•A single Carbon atom can be incorporated substitutionally below the Si adatoms.