AbstractSputter‐coated polymeric fluorocarbon films (PFCF) on poly(ethylene terephthalate) (PET) are prepared under conditions of various power and pressure levels. By analysis of X‐ray photoelectron spectroscopy (XPS) and infrared spectroscopy (IR), low fluorine‐to‐carbon (F/C) ratios, 1.02–0.61, indicate that the deposited films are highly crosslinked‐unsaturated and the F/C ratio is found to be remarkably influenced by the power and slightly affected by the pressure due to the change in various structure components in the film molecules. The nonwettable properties of the PFCF are consistent with the results obtained by XPS‐IR analysis. The cleavage of the sharp peak assigned to CO stretch in the FTIR spectra of the PFCF‐PET film can be thought to be an evidence related to the newly formed FC bond on a certain site of ester group next to benzene ring in PET macromolecules. Therefore, the chemical bond at the interface between FCPF and PET can be expected to enhance the joint strength of the interface. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1843–1850, 2002