Influence of higher semiinvariants on the fitting parameters of implanted ions distribution

The influence of higher semiinvariants of impurity distribution on fitting parameters of the Pearson curves is investigated. An exact distribution and a package for its parameter calculations, suggested by the authors, are used. Calculations are made for implantation of the ions Li, C, Ar and Ge into diamond, graphite and fullerite C60 over the energy range 0.1 keV to 1 GeV. It is found that (1) at the low energies, when nuclear scattering dominates, the higher semiinvariants underestimate the fitting skewness and excesses on 20-50% concerning their true values, if their modules are more than 0.1, (2) at the high energies, when electronic stopping dominates, the fitting skewness is always underestimated, and the fitting excesses are always overestimated in the same limits, (3) if module of the skewness or excesses are smaller than 0.1 and at the medial energies, when the nuclear and electronic energy losses are commensurable, the higher semiinvariants can change these fitting parameters several times with respect to true values.