Iodine penetration and doping of ion-modified polyethylene

Polyethylene (PE) foils, 15 mu m thick, were irradiated with 150 keV Ar+ io ns to the fluences from 1x10(12)-1x10(15) cm(-2) and subsequently doped wit h iodine from gaseous and liquid phases. The modified PE was examined using several analytical techniques with the aim to determine the mechanism of i odine doping of radiation damaged PE. Following techniques were used for th is purpose: Rutherford back-scattering (depth profiles of elements in near surface layer), Cahn-electrobalance (total amount of incorporated iodine), sheet resistance measurement by two-point technique, electron paramagnetic resonance (free radical concentration), X-ray diffraction (identification o f crystalline phase in PE), FTIR and Raman spectroscopy (chemical and struc tural changes, complex detection). A part of iodine atoms introduced from v apours as I-2(0) is bound to the sites on the PE macromolecular chain damag ed by ion impact and it does not affect the sheet resistivity. Other iodine atoms, which act as electron accepters, form polyiodine ions enhancing ele ctrical conductivity. This conclusion is supported by the results obtained on PE doped with polyions from water solution, where no significant change of the electrical conductivity was observed. (C) 1999 Elsevier Science B.V. All rights reserved.