Energy Spectra of Atoms Sputtered by Low-Energy Ions: Computer Simulation

The energy spectra and average energies of sputtered atoms were calculated for a number of amorphous targets (Si, Ti, Ni, V and Nb) bombarded with 1 keV Ar ions. The calculations were carried out using the computer simulation programs OKSANA and SRIM-2013. It is shown that for targets whose atoms are heavier than incident ions, SRIM can greatly overestimate the contribution of fast sputtered atoms. This is especially noticeable in calculations with the surface binding energy found by adjusting the calculated sputtering yields to the experimental ones. The simulation results are compared with analytical estimates of the average energy of ejected atoms based on the linear theory of sputtering. It is shown that in all the cases considered, these estimates are also greatly overestimated, since they do not take into account the degradation of collision cascades at low bombarding energies. A good agreement of the OKSANA, TRIM.SP and ACAT simulations is noted.