Controlling surfaces in plasma processing: Role of ions via molecular dynamics simulations of surface chemistry

A study of the interactions of energetic ions with various surfaces using molecular dynamics simulations is reported. Silicon atoms in the amorphous region are readily mixed by argon ions. Limited mixing in the crystalline layer is observed. Fluorine adsorbed on the silicon surface does not mix into the layer with argon ion impact. When an energetic F⁺ impacts a silicon surface, the uptake and apparent sub-surface mixing of F is much greater than Ar⁺-induced mixing. However, a closer examination shows that the F impacts have primarily increased the Si surface area by creating crevices and cracks, and that the F remains mainly on the surface of this layer.