Evidence for spike-effects in low-energy heavy-ion bombardment of Si and Ge

A systematic investigation of implantation damage by various heavy tons (Z1  7) in the energy range 10-60 keV has been undertaken in Si and Ge at 50 and 300 K. In several cases, diatomic ions having the same energy per atom as the corresponding monatomic ions were also used. The results are interpreted in terms of the mean deposited energy density within each collision cascade. In all cases, the generally accepted collision cascade theory grossly underestimates the amount of observed damage and, at the higher deposited energy densities (i.e., Θ ≳ 0.1 eV/atom), non-linear effects provide strong evidence for the existence of spike phenomena.