Fluoropolymer Films Deposited by Argon Ion-Beam Sputtering of Polytetrafluoroethylene

The FT-IR, XPS and UV spectra of fluoropolymer films (SPTFE-I) by argon ion-beam sputtering of polytetrafluoroethylene (PTFE) were obtained and compared with prior corresponding spectra of fluoropolymer films (SPTFE-P) deposited by argon rf plasma sputtering of PTFE, Although the F/C ratios for SPTFE-I and -P (1.63 and 1.51) were similar, the SPTFE-I structure had a much higher concentration of CF2 groups than the SPTFE-P structure; ca. 61 and 33% of the total carbon contents, respectively. Reflecting that difference, the FT-IR of SPTFE-I showed a distinct doublet at 1210 and 1150 cm-1 whereas SPTFE-P presented a broad, featureless band at ca. 1250 cm-1. The absorbance of the 1210-cm-1 band in SPTFE-I was proportional to film thickness in the of 50-400 nm. SPTFE-I was more transparent in the UV SPTFE-P at comparable thickness. The mechanism for SPTFE-I formation likely involves chopping off of oligomeric segments of PTFE as an accompaniment to plasma polymerization of TFE monomer generated in situ from PTFE on impact with energetic Ar ions. Data are given for SPTFE-I deposits and the associated Ar=-bombarded PTFE targets where a fresh target was for each run or a single target was used for a sequence of runs.