Randomisation of crystal structure within energetic collision cascades revealed by the sputtering of Au single crystals during ion bombardment

The ratio of random to preferential atomic ejection which occurs from the surface of a gold single crystal during ion bombardment has been found to be very sensitive to the ion mass. For instance, in the case of 50 keV Ne+ ion bombardment preferential ejection dominates, whereas in the case of 50 keV Au+ ion bombardment preferential ejection is only a small fraction of the total. These results are interpreted in terms of a dynamic randomisation of the crystal lattice which occurs during the creation of energetic atomic collision cascades. The disorder occurs so rapidly that a substantial fraction of atoms sputtered from the surface are ejected from an essentially random structure. It is thought that such gross disorder is only a transient phenomenon, and leaves no significant permanent effects, except perhaps for a few clustered defects.