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, e + . Indeed, the initial H + ion energy of 1.1 MeV incident on the front polymer film was degraded down to 0.48 MeV at the entrance of the rear stacked film, which corresponds to an increase of e + from ∼0.22 up to ∼0.41 MeV cm 2  mg −1 . Ion fluences in the range (0.05–4) × 10 15  cm −2 corresponding to an ion dose interval 1.80–263 MGy were used. The (H, O, C) atomic surface densities of the PET polymeric films were quantitatively determined by IBA techniques using a 1.62 MeV deuteron beam leading to the following main results: (i) for each target film stacked at a given position thus fixed e + , the oxygen atomic density decreases linearly versus ion fluence, ϕ ; (ii) for the different e + , the hydrogen impoverishment of the PET target is insignificant below critical fluence ϕ c  ∼ 1.5 × 10 15  cm –2 and becomes substantial above ϕ c ; (iii) for fixed ϕ , the hydrogen and oxygen atomic densities exhibit linear decreases versus e + ; (iv) all measured such data versus ϕ and e + 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.