Iron metalization of fluorinated organic films: A combined X-ray photoelectron spectroscopy and atomic force microscopy study

The evolution of the metal-organic interface during iron-mediated metalization of fluorinated organic surfaces has been studied using X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). Poly(tetrafluoroethylene) (PTFE) and a semifluorinated self-assembled monolayer (CF3(CF2)(7)(CH2)(2)SH, CF-SAM) formed on Au were used as substrates, the latter serving as a model for the interfacial region of a fluorinated polymer. Reaction of Fe with both surfaces resulted in defluorination of the organic film, production of a carbonaceous overlayer, and exclusive formation of-iron(II) fluoride. A metallic iron overlayer was formed concurrently with FeF2 during deposition on CF-SAMs and following extended iron exposures with PTFE substrates. Terminal CS groups produced during metalization of PTFE are postulated to arise from a chain rearrangement reaction involving transient -CF-radicals. X-ray treatment of metalized PTFE was found to represent an effective means to increase the FeF2 content in the metal-organic interface. Ex situ AFM measurements revealed that the frictional characteristics of the surface increased during the initial stages of metalization associated with defluorination and FeF2 formation. At higher Fe exposures the surface friction decreased as a metallic overlayer evolved.