The chemical modification of amorphous polystyrene (PS) by the deposition of atomic S, SC, and SH with 25, 50, and 100 eV of incident kinetic energy is examined using classical molecular dynamics simulations. The forces are determined using the second-generation reactive empirical bondorder (REBO) potential that has been extended to include sulfur. In all cases, the S atoms or S-containing dimers are deposited randomly on the PS surface with a flux of about 0.4 × 10 24 ions/(cm 2 s), which is comparable to experimental values. The simulations predict the way in which the depth profiles vary as a function of the identity and kinetic energy of the incident atom or dimer. We also quantify the ways in which the surface is chemically modified and provide a profile of the chemical products formed on the surface, within the substrate, or in the material sputtered from the surface. The simulations predict that the maximum density of deposited atoms throughout the surface substrate, 3.32 × 10 18 /cm 3 , occurs for S deposition with 50 eV of incident energy. We further predict that the highest molecular weight products are formed as a result of S deposition with 100 eV of energy. Additionally, the chemical reactions that occur during the deposition are found to depend on the beam energy for all the incident atoms or dimers considered. Negligible change in the surface roughness is predicted to occur as a result of these deposition processes.

Classical molecular dynamics simulations are performed to determine the mechanisms by which hyperthermal hydrocarbon polyatomics, which are present in low-energy plasmas, chemically modify polymer surfaces. In particular, C2H, CH3, and C3H5 are deposited on an amorphous poly (methyl methacrylate) (PMMA) substrate with kinetic energies of 4, 10, 25, and 50 eV and compared to the deposition of H at the same energies. The short-range forces on the atoms are determined using the second generation reactive empirical many-body potential, while the long-range forces are determined using a Lennard-Jones potential. The simulations predict that at all these incident energies, the chemical modification of the PMMA is limited to within a nanometer of the surface. Atoms, fragments, and incident polyatomics are further predicted to chemically attach to specific sites on the PMMA monomers at low energies and to attach to a wider range of sites at higher energies. However, no appreciable cross-linking between polymer chains is predicted to occur. Variation in the penetration depth of the deposited polyatomics or H is correlated to differences in their size and bond saturation. The greatest extent of chemical modification of the PMMA surface slab is achieved for C2H deposition with 50 eV of kinetic energy.