Role of negative ions in the RF plasma deposition of fluoropolymer films from perfluoropropane

RF plasma‐deposited fluoropolymer films prepared from perfluoropropane were examined on a variety of metallic, glass, and polymeric substrates using electron spectroscopy for chemical analysis (ESCA) and Fourier transform infrared spectroscopy (FTIR). The F1s ESCA spectra of thin (< 100 Å) depositions on some substrates exhibited a peak suggestive of ionic fluoride species. FTIR studies demonstrated the presence of bifluoride ion in some films. Angular‐dependent ESCA studies indicated that these ionic species were not located at the outermost surface of the deposition but rather near the fluoropolymer‐substrate interface. By depositing these fluoropolymer films on a large number of different metallic substrates, and comparing the results of thermal stability studies and solubility studies with literature descriptions of the properties of each of the respective fluoride salts, additional support for the identification of ionic fluoride species at the fluoropolymer‐substrate interface was generated. The implications of this interfacial ionic zone for the adhesion of plasma‐deposited fluoropolymer films to substrates are considered.