Molecular dynamics and Monte-Carlo simulation of sputtering and mixing by ion irradiation

Molecular dynamics (MD) and Monte-Carlo (MC) simulations of low-energy (<500 eV) Ar ion irradiation on Si substrates were performed in order to investigate the mixing and sputtering effects. Both MD and MC simulation show similar results in sputtering yield, depth profile of projectile and mixing of substrate. For these incident energies, the depth of the mixed region is determined by the implant range of incident ions. For example, when the incident energy is 500 eV, the Ar ions reach a depth of 40 Å so that the Si atoms that reside shallower than 40 Å are fully mixed at an ion dose of about 5.0×10¹⁶ atoms/cm². The resolution of secondary ion mass spectrometry (SIMS) was also studied. It was found that the resolution of SIMS depends on the depth of mixing, which depends in turn on the implant range of the probe ions. This is because the mixing of substrate atoms occurs more frequently than sputtering, so that the information about the depth profile in the mixing region is disturbed.