The chemisorption of SiCl4, Si2Cl6, and chlorine on Si(111)7x7 has been characterixed using soft X-ray photoemission with synchrotron radiation, thermal desorption spectroscopy, and Auger electron spectroscopy. SiCl4 dissociatively chemisorbs on room temperature Si(111)7x7 with an extremely low sticking coefficient, with only SiCl remaining on the surface. In contrast, Si2Cl6 chemisorbs with ~500 times greater probability and then partly dissociates into SiClx (x = 1, 2, 3) fragments. A monolayer of Cl deposited directly also contains SiCl, SiCl2, and SiCl3 surface species, but they are created via reaction with substrate Si atoms and have lower Si 2p core level binding energies. Upon heating the surface, all the adsorbed Cl is removed via desorption of silicon chlorides, primarily SiCl2, indicating that SiCl4, SiCl6, and chlorine will etch SI(111)7x7 if an additional reactant is not available to remove the surface Cl. Interestingly, the different reactives of SiCl4 and Si2Cl6 upon adsoprtion can be explained by the dynamics of different adsorption mechanisms.
Citation: Surface Science
Pub Type: Journals