Evidence for heated spikes in bombarded gold from the energy spectrum of atoms ejected by 43 kev a+and xe+ions

A low-energy peak at 0.15 ev is observed in the energy spectrum of atoms ejected from Au under heavy ion bombardment. The peak accounts for 12% of all atoms sputtered in the case of 43 kev Xe+ ions, and 4% with 42.5 kev A+ ions. It is shown that the phenomenon is not directly associated with focused collision sequences and an explanation is given in terms of evaporation from heated spike regions. A deduction that the focusing range is much greater than the recoil atom's range leads to a model of constant radius spikes. The ensuing calculation correctly predicts the shape of the spectrum, its magnitude and its dependence on the bombarding ion. An effective radius of 110 Å and a maximum temperature of 1750°k is deduced for spikes caused by recoils with 42 kev. Some implications are considered in the fields of radiation damage and sputtering.