Simulations of thin film deposition from atomic and cluster beams

We have simulated silicon thin film growth from energetic beams using molecular dynamics methods. We find that the kinetic energy of the beam has a dramatic effect on the amount of amorphous or cystalline material in the resulting deposit. In some cases energetic beams can produce a crystalline structure at less than half the absolute temperature required for a thermal beam. Our simulations show that local heating at the point of impact facilitates the atomic rearrangements required for crystallization. Cluster beams can also produce crystalline deposits at low temperatures. In this case an amorphous layer forms at the crystal surface, and the thickness of this layer remains constant after an initial transient as crystallization occurs at the amorphous-crystal interface. We discuss the mechanisms by which energetic collisions influence crystal growth, and attempt to develop a criterion for determining whether a beam favors amorphization or crystallization.