Trapping and desorption of energetic Cu atoms on Cu(111) and (001) surfaces at grazing incidence

Molecular-dynamics (MD) simulations of Cu atoms impacting both Cu(111) and (001) surfaces at grazing incidence have been performed to study trapping ( or surface skipping), desorption, and energy dissipation. An energetic Cu a tom (10 less than or equal to E less than or equal to 100 eV) can become tr apped by the mean attractive potential above the surface, oscillating norma l to the surface. While in this trapped state, it can traverse hundreds of A as it dissipates energy to the surface. Until the atom either desorbs or comes to rest, it experiences an energy loss, that is piecewise linear in t ime, typically comprised of two or more linear regions. In each region, the energy loss rate, nE/dt, is approximately constant. The process can be cha racterized by two parameters: the desorption probability at each oscillatio n and an average energy loss rate (per oscillation) that is independent of energy. These parameter values are the same for both the (111) and (001) su rfaces. A phenomenological model based on these parameters is presented, an d the predictions of sticking probability, average energy transfer to the s urface, and total distance traveled, agree with full MD simulations. The de pendence of the desorption probability on the surface temperature was also studied. [S0163-1829(99)01339-9].