Comparison of growth of hydrocarbon thin films by molecular-beam and cluster-beam deposition: Atomistic simulations

Molecular dynamics simulations have been performed to study the difference in the growth of polyethylene thin films via neutral ethylene molecular-beam and cluster-beam depositions. The collisions occurred at incident energies of 25 and 50 eV/molecule on a hydrogen-terminated diamond (111) surface. A many-body empirical bond order potential for hydrocarbons was used to model the interatomic interactions in the system that allowed for bonds to be broken and formed over the course of the simulations. In contrast to the expectations that the cluster beam would provide significantly enhanced thin-film nucleation, the results indicate few differences in thin-film adhesion that occurs as a result of the deposition. The role of substrate temperature on thin-film nucleation is also investigated and found to be negligible over a 1200° range. Finally, structural relaxation of thin-film fragments is investigated through energy minimization with AM1. The structures of the fragments are found to change slightly from the relaxed structures predicted in the molecular dynamics simulations.