Positron annihilation spectroscopy was used to address the proportionality of vacancy production versus ion fluence in Si. For implants of Au (11.5MeV, 2 x 109 to 3 x 1011/cm2) and Ge (8.6MeV, 5 x 109 to 4 x 1011/cm2), it was found that the vacancy accumulation was approximately linear (i. e., doubling the fluence doubled the vacancy concentration). This was in contrast to a variety of prior reports, both theoretical and experimental, and it was shown that this discrepancy was primarily a function of the range of fluences examined. It was shown also that sub-linear vacancy accumulation at higher ion fluences was driven principally by direct overlap of damage cascades, not by defect diffusion.

Proportionality of Vacancy Concentration to Ion Implantation Fluence. P.J.Simpson, S.Szpala: Journal of Applied Physics, 2002, 92[10], 5852-5