Studies of atomic and molecular fluorine reactions on silicon surfaces

X-ray photoelectron spectroscopy (XPS) and an ultrahigh vacuum compatible microwave discharge effusive beam source have been used to study the reactions of atomic and molecular fluorine on Si(111) surfaces. Fluorine uptake and changes in binding energy and peak shape for the Si 2p and F 1s XPS peaks have been measured as functions of fluorine exposure. The results indicate that molecular fluorine is dissociatively chemisorbed to form an SiF2-like surface species. This reaction saturates at approximately one monolayer surface coverage. In contrast, atomic fluorine uptake extends well beyond the monolayer regime to include several Si layers. Additionally, as the uptake increases, the reaction product becomes SiF4-like. These findings are compared with previously reported results for XeF2 adsorption.