The photo-etching of chlorinated silicon (1 1 1) surface was found to be induced by laser illumination at two different wavelengths, 245 and 290 nm, in the ultraviolet (UV) range. REMPI-TOF (resonance-enhanced multiphoton ionization-time of flight) measurements revealed that, even when the surface is covered with only silicon monochlorides (SiCl), the molecules desorbing on etching are highly chlorinated silicon (SiCl2-4), which strongly suggests that the atomic process enhanced by the light illumination is not the desorption process as usually conjectured but the hopping of atomic chlorines to neighboring sites. Here they recombinatively react with adsorbed monochlorides forming highly coordinated chlorides that subsequently desorb. (C) 2002 Elsevier Science B.V. All rights reserved.