Easy plasma nano-texturing of PTFE surface: From pyramid to unusual spherules-on-pyramid features

Oxygen plasma etching of polytetrafluoroethylene has been investigated as a way to sculpture nano-features on its surface and producing a super-hydrophobic material in one step. It has been found that, depending on the experimental conditions, the shape of the structures engraved in the polymer surface passes from pyramidal to unique pyramids with well-defined spherules on the top. The latter are obtained without any mask/lithographic option. In a previous paper the water repellent character of such etched polytetrafluoroethylene surface has been well documented and explained by some of the authors. In this paper, instead, some insights in the formation mechanism of such unusual morphology are provided. Chemical and morphological characterization indicate in the iron surface contamination the clue for the formation of such complex agglomerates.