[en] Formed on n-Si layers of p-type conductivity with 0.7 μm thickness and boron concentration to 10¹⁹ cm^-3 were irradiated by Ar⁺ at 135 keV and doses of 10¹⁵ - 10¹⁷ cm^-2 at 900 deg C. Together with appearance of radiation-stimulated diffusion redistribution of boron was found a process of increased with dose accumulation of boron near the surface. The accumulation was accompanied by electric neutralization of acceptors. Boron neutralization effects was kept at annealings to 1100 deg C, moreover thermal stability of the effect was grown with the ion dose. Mechanism of the phenomenon is proposed. 12 refs., 3 figs