Scanning tunnelling microscopic studies of the etching of (100)-(2 x 1) surfaces showed that the rate of terrace pit formation went through a maximum at Cl surface coverages of 0.77 monolayers. This contradicted the predictions of conventional models. By using newly calculated energies for various possible surface configurations, it was shown that a key factor in desorption was the formation of a single-atom vacancy adjacent to a volatile SiCl2 unit.

Vacancy-assisted halogen reactions on Si(100)-(2 x 1) K.Nakayama, C.M.Aldao, J.H.Weaver: Physical Review Letters, 1999, 82[3], 568-71