STIMULATED DESORPTION OF CL+ AND THE CHEMISORPTION OF CL-2 ON SI(111)-7X7 AND SI(100)-2X1

The chemisorption of Cl-2 on Si(111)-7 x 7 and Si(100)-2 x 1 and the mechanism for stimulated desorption of Cl+ from Si are studied with soft X-ray photoelectron spectroscopy (SXPS) and photon-stimulated desorption (PSD). It is shown that Cl-2 interacts with Si(111)-7 x 7 at room temperature to form mono-, di- and tri-chlorides, while primarily monochlorides are formed on Si(100)-2 x 1. These differences are explained in terms of the reconstructions of each clean surface. The stimulated desorption of Cl+ ions has a threshold at similar to 20 eV that results from a direct excitation of a Cl 3s electron to an unoccupied Cl antibonding level. No direct desorption of Cl+ ions is observed at the Si 2p edge. Differences between the mechanisms for F+ and Cl+ desorption from Si are discussed.