DIFFUSE OF IODINE INTO POLYETHYLENE IMPLANTED WITH 150 KEV AS+ IONS

The iodine depth profiles and the sheet resistivity were studied on po lyethylene implanted with 150 keV As+ ions to the doses of 1 x 10(12)- 1 x 10(15) cm-2 and then exposed to iodine vapours for 4 hours at the temperature of 90-degrees-C. For lower implanted doses the iodine cont ent in the radiation damaged layer increases with the dose, it achieve s a maximum for the dose of 1 x 10(14) cm-2, and for still higher dose s it decreases significantly. The iodine depth profiles change dramati cally from ''bumpy'' ones for the doses below 1 x 10(14) cm-2 to ''dep leted'' ones, exhibiting a pronounced concentration maximum at the dep th of 300 nm, for higher implanted doses. The iodine depth profiles di ffer strongly from those expected from classical Fickian diffusion. Th e iodine doping leads to an immediate decrease of the sheet resistivit y of radiation damaged polyethylene by about three orders of magnitude . A spontaneous increase of the sheet resistivity as a function of the time elapsed from the diffusion was observed together with iodine inw ard migration. The data obtained seem to support a concept of enhanced mobility of iodine atoms in the radiation damaged surface layer and t heir trapping on defects produced by ion impact.