Effect of electric charge accumulation on the modification of surface properties by means of low energy ion implantation

Low energy ion implantation produces an accumulation of electric charge on the surface of insulators. This phenomenon can be used as a complementary tool to improve the efficacy of polymer surface treatments. Samples of polyethylene (PE) were implanted with 2.2 keV ions to a fluence of 3.9 × 1016D+ cm−2 with and without the use of charge neutralization. The physical and physicochemical properties of the surface were characterized by elastic recoil detection −E × B, Rutherford backscattered spectroscopy (RBS), x-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). AFM characterization showed that the roughness of the PE surface decreases after ion beam bombardment with neutralization, but increases during the implantation with charge accumulation. The surface wettability increases after implantation with both methods and this effect is enhanced with non-neutralized implantation. RBS analysis showed a physical trapping of oxygen following both treatments, the oxygen adsorption being more pronounced without neutralization of the sample surface. XPS characterization confirmed this result and revealed the formation of C–O, C=O and O–C=O molecular bonds, especially in samples implanted without neutralization. Our results show that the level of surface charging affects the topography and the kind of damage at the surface, providing a complementary tool to adjust the properties of polymer surfaces.