MeV H+ ion irradiation effect on the stoichiometry of polyethylene terephthalate films

Abstract

Appropriate experimental conditions have been chosen to investigate the influence of main H+ ion irradiation parameters on stoichiometry changes induced in polyethylene terephthalate (PET) thin films. Stacks of six self-supporting identical films were irradiated perpendicularly to the target surface. Thus, the irradiations were realized simultaneously at different values of the target electronic stopping power, ε+. Indeed, the initial H+ ion energy of 1.1MeV incident on the front polymer film was degraded down to 0.48MeV at the entrance of the rear stacked film, which corresponds to an increase of ε+ from ∼0.22 up to ∼0.41MeVcm2mg−1. Ion fluences in the range (0.05–4)×1015cm−2 corresponding to an ion dose interval 1.80–263MGy were used. The (H,O,C) atomic surface densities of the PET polymeric films were quantitatively determined by IBA techniques using a 1.62MeV deuteron beam leading to the following main results:(i)for each target film stacked at a given position thus fixed ε+, the oxygen atomic density decreases linearly versus ion fluence, ϕ;(ii)for the different ε+, the hydrogen impoverishment of the PET target is insignificant below critical fluence ϕc∼1.5×1015cm–2 and becomes substantial above ϕc;(iii)for fixed ϕ, the hydrogen and oxygen atomic densities exhibit linear decreases versus ε+;(iv)all measured such data versus ϕ and ε+ merge together into a unique decreasing curve for each (H,O,C) polymer content element when represented in function of the H+ ion dose, D, tightly correlating the latter two parameters;(v)the O content element release from the PET target appears to be the most important, followed by the H content depletion, while the target C content is least affected under H+ ion irradiation.