Characterization of fluoropolymer films deposited by magnetron sputtering of poly(tetrafluoroethylene) and plasma polymerization of heptadecafluoro-1-decene (HDFD) on (100)-oriented single-crystal silicon substrates

Fluoropolymer thin films have been deposited on (100)-oriented single-crystal silicon substrates via argon plasma sputtering of a poly(tetrafluoroethylene) (PTFE) target and plasma polymerization of 1H,1H,2H-heptadecafluoro-1-decene (HDFD). The surface composition and molecular structure of the deposited fluoropolymer films were analysed by x-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (ToF-SIMS) and Fourier transform infrared (FTIR) spectroscopy. The ToF-SIMS spectrum of the sputter-deposited PTFE (s-PTFE) surface revealed a high concentration of oligomeric -(CF₂)- segments, resembling that of the pristine PTFE surface. However, the ToF-SIMS spectra of the plasma-polymerized HDFD (pp-HDFD) films showed the presence of oligomeric -(CF₂)- segments with much shorter repeat units, in comparison with those of the pristine PTFE and s-PTFE film. The XPS and FTIR results suggested that the surface composition and chemical structure of the pp-HDFD film deposited at a high r.f. power were closer to those of the s-PTFE film. Water contact angle and atomic force microscopy measurements indicated that both sputtering deposition and plasma polymerization could give rise to highly hydrophobic surfaces with good uniformity. Peel adhesion test results suggested that both the s-PTFE and pp-HDFD films were strongly tethered to the surface of Si substrates.