Simultaneous etching and polymerization were studied for a series of perfluoroalkanes in an r.f. plasma system. The incorporation of metal (removed from the excitation electrode) into the fluoropolymer films (formed on the grounded electrode) is demonstrated and the metal content is shown to be related to the relative rates of etching and polymer deposition. Determination of the film structures was achieved by electron spectroscopy for chemical analysis which, coupled with the analysis of the plasma gas phase by direct mass spectrometric sampling, led to the identification of the primary precursors to polymerization. The major precursors can be summarized as (CF2)n (n=1,2,3,4) for all systems studied, although at low power levels their relative importance is shown to be a function of the injected perfluoroalkane. © 1981.