Proportionality of vacancy concentration to ion implantation fluence

摘要

We have used positron annihilation spectroscopy to address the proportionality of vacancy production versus ion fluence in silicon. For implants of Au (energy 11.5 MeV, fluences 2x10(9)-3x10(11)/cm(2)) and of Ge (energy 8.6 MeV, fluences 5x10(9)-4x10(11)/cm(2)), we find that the vacancy accumulation is approximately linear (i. e., doubling the fluence doubles the vacancy concentration). This is in contrast to a variety of prior reports, both theoretical and experimental, and we show that this discrepancy is primarily a function of the range of fluences examined. We show also that sublinear vacancy accumulation at higher ion fluences is driven principally by direct overlap of damage cascades, not by defect diffusion. (C) 2002 American Institute of Physics. References: 21