Enhanced sputtering from the F/Si(100) surface with extraction of the surface bond direction

It was found that slow highly charged ions had a high ability to ionize F atoms on a F/Si(100)-2×1 surface and desorb F+ ions along the local bond direction. Actually, the F+ ion yields were proportional to the incident charge cubed, and the F+ ions were emitted along the Si-F bond directions showing a fourfold symmetry pattern. The trigger process of the F+ formation is discussed based on a charge transfer process of F 2p electrons by extending the classical over barrier model. Further, we found that the kinetic energy of highly charged ion induced F+ ions is lower than that of electron stimulated F+ ions caused by the removal of a F 2s electron.