Density and binding effects in low-energy sputtering

Sputtering of amorphous targets, from 12Mg to 92U, under bombardment with 500, 100 and 50 eV Ar ions at normal incidence is studied by binary-collision simulation. Attention is given to the angle- and energy-integrated sputtering characteristics, namely, the sputtering yield, the mean depth of origin and mean energy of sputtered atoms. The results are approximated by a function ∝Np/Uq, where N is the target atomic density, U the surface binding energy, p and q the fitting parameters. It is shown that the relative importance of density and binding effects differs for different sputtering characteristics and may depend heavily on the bombarding energy. With regards to the sputtering yield, both effects tend to be particularly important at lower energies. Unlike the sputtering yield, the mean energy of sputtered atoms is fairly insensitive to U at the lowest energy studied. Results are compared with the data from the literature