ON THE REDISTRIBUTION OF LI-6(+) IONS IMPLANTED INTO POLYPROPYLENE FOILS

Li-6(+) (150 keV) was implanted into thin polypropylene foils at fluen ces of 1 x 10(13) to 1 x 10(14) cm(-2). Subsequent neutron depth profi ling measurements of the Li distributions revealed considerable deviat ions from the expected ballistic range profiles. This Li redistributio n was simulated by a numerical computer calculation. The best fit betw een measurements and simulations was obtained by assuming that (i) Li redistributes immediately after its ballistic slowing-down, (ii) the L i mobility is enhanced in the radiation-damaged polymer region, the lo cal diffusion enhancement being controlled by the target's electronic damage, (iii) mobile Li is readily trapped at radiation-induced defect s, their density being proportional to the target's electronic damage, (iv) these traps are saturable ones, and (v) Li migration is not rest ricted to the ion track region, but proceeds also through the neighbor ing unirradiated bulk, though with slower speed.