During plasma treatment of polymers, etching occurs and functional groups are introduced on their surface. We assumed that controlling the etching rate would enable plasma treatment using a single gas to control the ratio of functional groups generated on a polymer's surface, although previous studies have indicated that several different types of functional groups are formed when the gaseous species are varied. In this study, we selected the base pressure (BP) as a parameter for controlling the etching rate and subjected polytetrafluoroethylene (PTFE) to plasma treatments using only He gas at various BPs. The chemical composition of the surface of the plasma-treated PTFE samples was evaluated by X-ray photoelectron spectroscopy (XPS), and the ratios of fluorine (CF3, CF2, C-F), oxygen (O-C[double bond, length as m-dash]O, C[double bond, length as m-dash]O, C-O), and carbon (C-C, C[double bond, length as m-dash]C) groups were quantified from the C 1s-XPS spectra. The fluorine-group ratio decreased and the oxygen- and carbon-group ratios increased with decreasing BP. The results demonstrated that plasma treatment using a single gas enabled flexible selection of the ratio of functional groups generated on PTFE via control of the BP.
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