A molecular dynamics study of thin-film formation via molecular cluster beam deposition: Effect of incident species

Molecular dynamics simulations are used to study thin-film nucleation and growth through the deposition of molecular cluster beams on diamond surfaces. A reactive, empirical bond-order hydrocarbon potential is used to calculate the forces on the atoms. Beams of ethylene (C₂H₄) molecular clusters, adamantane (C₁₀H₁₆) molecules, and fullerene (C₂₀) molecules are deposited on hydrogen terminated diamond (111) surfaces at room temperature. These three beams are chosen because of the different chemical bonding in the incident particles - van der Waals interactions in the case of the ethylene molecular clusters, pure sp³ bonds in the case of the adamantane molecules, and covalent sp² bonds with distorted p-orbitals in the case of the fullerene molecules. All three beams are deposited on the surface along either the [1̄1̄2] direction or the [1̄10] direction at incident angles of 0°, 15°, 45° and 60° from the surface normal. Two deposition energies are considered: a total energy of 400 eV/cluster or molecule and a total energy where the momentum normal to the surface is equivalent to an energy of 400 eV/cluster or molecule. The C₂₀ is found to be the most efficient species at producing an amorphous thin film while the molecular cluster beam of ethylene is the least efficient. Despite the differences in the chemical bonding in the three incident species, the structures of the resultant thin films are predicted to be similar at these energies.