The simulation of nanoscale sputter depth profiles using molecular dynamics

The feasibility of using molecular dynamics (MD) for simulation of a nanoscale sputter depth profile experiment is examined for the idealised case of depth profiles of individual atomic layers in a Cu(1 0 0) target. Issues relating to the extraction of depth profile information from MD simulations are discussed in detail. The simulations examine the sputter erosion of static and azimuthally-rotated Cu(1 0 0) targets produced by 3 keV Ar projectiles incident at 25° from the surface. The simulated projectile fluence extends to 5 × 10¹⁵ cm⁻², and the mean value of the sputter depth, z, amounts to 8 Cu(1 0 0) monolayers (ML) or 15 Å. The simulations directly supply progressive layer erosion profiles (curves that depict the extent of sputter erosion of each atomic layer vs. total sputter depth). A fitting method is then used to extract smooth depth profiles for each atomic layer from these predicted erosion profiles. The depth profile characteristics (height, width, shift) for the first 10 layers of the target show a pronounced dependence on layer depth.