Dynamical branching during fluorination of the dimerized Si(100) surface: A molecular dynamics study

Collections of classical trajectories have been numerically generated for individual F2 molecules impinging at normal incidence on a Si(100) surface at 0 K dimerized in a p(2×1) pattern. A linear combination of two-atom and three-atom interaction functions represents the potential energy. Trajectories fall into four categories: (a) non-reactive F2 rebound, (b) monofluorination at a surface dangling bond with energetic expulsion into the vacuum of the remaining F atom, (c) difluorination of a pair of dangling bonds, and (d) monofluorination with retention of the second F in a weakly bound Si–F⋅⋅⋅F surface complex. Surface patterns for difluorination, (c), indicate absence of surface diffusion during this mode of chemisorption. Increasing either the translational kinetic energy or the vibrational excitation of the incident F2 appears to enhance its surface reactivity.