Defect profiling in elemental and multilayer systems: correlations of fitted defect concentrations with positron implantation profiles

The results of several positron annihilation (Doppler broadening) experiments have been analyzed using the BNL Monte Carlo implantation profiles and the program VEPFIT. The program VEPFIT has been modified so that scaled, parameterized multilayer profiles can also be used as the initial condition for the diffusion equation solution. We have looked at both elemental (e.g. amorphous silicon) and multilayer (e.g. PdSi) systems. Strong correlations between the input implantation profile parameters and the fitted values obtained for the diffusion lengths and overlayer thicknesses for the multilayer systems have been found. The effect of uncertainties in the mean depth on the value of the diffusion length and hence the defect concentrations will be discussed. The impact of reimplanting backscattered positrons on both the implantation profiles and the fitted diffusion lengths will also be presented.