Evidence of the synergetic role of charged species and atomic oxygen in the molecular etching of PTFE surfaces for hydrophobic surface synthesis

The transformation of a poly(tetrafluoroethylene) (PTFE) hydrophobic surface into a superhydrophobic one using a low pressure RF plasma is explored using optical emission spectrometry (OES), X-ray photoelectron spectroscopy (XPS), water contact angle (WCA) measurements, mass measurements, and atomic force microscopy (AFM). It is shown that the increase in contact angle is due to an increase of roughness provoked by a chemical etching of the surface. We propose a molecular mechanism for etching that requires the simultaneous presence of atomic oxygen and negatively charged species (electrons) at the PTFE surface.