Computed molecular depth profile for $C_{60}$ bombardment of a molecular solid

Molecular dynamics (MD) simulations have been performed for 10 keV $C_{60}$ bombardment of an octane molecular solid at normal incidence. The results are analyzed using the steady-state statistical sputtering model (SS-SSM) to understand the nature of molecular motions and to predict a depth profile of a $\delta$-layer. The octane system has sputtering yield of $\sim$ 150 $nm^{3}$ of which 85% is in intact molecules and 15% is fragmented species. The main displacement mechanism is along the crater edge. Displacements between layers beneath the impact point are difficult because the nonspherically shaped octane molecule needs a relatively large volume to move into and the molecule needs to be aligned properly for the displacement. Since interlayer mixing is difficult, the predicted depth profile is dominated by the rms roughness and the large information depth because of the large sputtering yield.