Depth profiles of defects in C-ion-irradiated steel determined by a least-squares fit of S parameters from variable-energy positron annihilation.

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A method for reconstructing the depth profile of defects in ion-irradiated samples with use of slow positrons is presented. The depth profiles of vacancy-type defects in the 316 stainless-steel sample irradiated with 250-keV carbon ions to a dose of 9.2\ifmmode\times\else\texttimes\fi{}${10}^{18}$/${\mathrm{m}}^{2}$ at room temperature has been calculated from Doppler-broadening S parameters measured as a function of the positron energy. Without assuming any specific shape for the defect profiles, the defect profiling is made by a least-squares fitting method. The resulting profile shows that the defect distribution peaks at a depth smaller than that for the predicted damage peak, suggesting that the implanted carbon atoms enhance the defect annihilation by recombinations.