EVOLVE, A TIME-DEPENDENT MONTE-CARLO CODE TO SIMULATE THE EFFECTS OF ION-BEAM-INDUCED ATOMIC MIXING

The sputtering of inhomogeneous multielement targets by medium-energy ions is simulated using the Monte Carlo method. Incident ions as well as the multiple recoil atoms of the cascade produced in the medium are followed until either they escape from the solid or energy falls below a low cut-off value. Two modes of simulation are demonstrated. In the first mode, the program deals with an undisturbed medium and no change takes place in the medium for the simulation of successive ions; a situation which corresponds to low-dose sputtering experiments. In contrast to previous Monte Carlo codes, the other mode of this program considers atomic-mixing of all species including the implanted beam ions in the medium during the simulation of ion bombardment. This simulation of time-dependent processes can provide a better understanding of some sputtering phenomena of complicated nature such as the preferential sputtering of certain species within a multielement medium. Furthermore, this simulation demonstrates the depth resolution limit due to atomic mixing and preferential sputtering which sets bounds on the use of sputter sectioning in the depth profiling of multielement interfaces.