Fluctuations in atomic collision cascades with power law scattering

Abstract

In a preceding paper [1], fluctuations in a collision cascade were investigated. The variance of the yield as well as the energy and depth correlations in sputtering and defects were calculated with constant cross sections and a hard-sphere scattering model. In a more real approximation, atomic collision cascades obey power law scattering, which has a rather different collision kinematics. In particular, the energy transfer, and thus the energy distribution within the cascade evolution, is very different from that of a hard-sphere model. Therefore the yield and mean distribution, as well as the variance and the two-point cascade correlations were calculated in the present paper in a power law scattering model. It was found that despite the differences in the cascade dynamics, most previous findings are still valid. Notably, the relative variance of defects is low in infinite media, whereas in half-spaces it is a monotonically increasing function of the energy of the bombarding ion. The two-point energy and depth correlations are also quite similar to their hard-sphere counterparts. Calculated values of the yield, mean distribution, variance and two-point correlations are shown in the paper for several cases. All calculations were made by using a binary collision Monte-Carlo algorithm.