Theoretical modeling of energy redistribution and stereodynamics in CF scattering from Si(100) under grazing incidence

Abstract

We have simulated CF scattering from Si(100) using the molecular dynamics method. Translational energy loss spectra are presented. The shape of the energy loss distribution as a result of internal energy release is analyzed. At the classical turning point, the internal energy of the molecule is mainly in the form of rotational energy. The strong rotational excitation results in additional molecule-surfaces interactions during the latter half of the collision. These additional collisions permit some molecules that initially gain internal energy exceeding the bond strength to ultimately survive the collision process via rotational de-excitation. The rotational motion exhibited by surviving molecules is determined by the combination of the molecular axis orientation and the local surface structure during the collision process. The rotation planes of the surviving molecules are preferentially aligned with the surface normal (cartwheel-like and propeller-like motions). In this study, propeller-like motion of the surviving molecules is predicted. The majority of surviving molecules exhibit a cartwheel-like motion. However, molecules that gain a propeller-like rotation exhibit a much better alignment of their planes-of-rotation compared with molecules exhibiting cartwheel-like motion.