Thin specimens were irradiated with Ne, Ar or Kr ions with various energies, at room temperature, and the doses which were required for complete amorphization were determined by using  in situ  transmission electron microscopic and electron diffraction techniques. The onset of amorphization was detected even after the lowest doses; thus indicating amorphization by individual ions. For all of the ions, the dose which was required for complete amorphization increased almost linearly for ion energies ranging from 0.5 to 3.5MeV. The amorphization cross-sections were determined for all the ions and energies that were used. The degree of damage, as expressed by the number of displacements per atom which was required for complete amorphization, decreased with increasing ion energy or mass. A decrease, with increasing energy or mass, was attributed to a decrease in the irradiation-enhanced annealing of amorphous volumes, due to a decrease in the fraction of low-energy atomic displacements. Increasing the fraction of low-energy atomic displacements during Kr irradiation, by simultaneous 1MeV electron irradiation, increased the Kr ion dose that was required for complete amorphization. The radiation annealing was suggested to be due to freely migrating defects that were produced by low-energy atomic displacements.

R.C.Birtcher: Philosophical Magazine B, 1996, 73[4], 677-88