Plasma polymerization of fluorine alloyed amorphous carbon coatings

This article reports on the deposition conditions and characterization of plasma polymerized fluorocarbon coatings grown by an inductively coupled radio frequency plasma source, using CH 4 and CF 4 as precursor gases. SiH 4 , H 2 , or Ar were further added to the plasma to investigate their influence on the coating properties. The coatings were characterized by x-ray photoelectron spectroscopy to determine the surface and bulk composition and combined with Fourier-transform infrared spectroscopy to reveal the structure of the coatings. The mechanical properties (hardness and Young’s modulus) were measured by nano-indentation. The surface energy was obtained by contact angle measurements with two different liquids. By varying the deposition conditions, it was possible to adjust separately the polar and dispersive part of the surface energy. With the appropriate feed gases and process parameters, we were able to deposit coatings with surface energies as low as 14 mN/m. A low polar component of the surface energy corresponds to a high fluorine, CF 3 and CF 2 content at the surface of the coatings. The maximum contact angle achieved was 113°. By adding H 2 to the plasma, it is possible to minimize the polar component and maximize the dispersive component of the surface energy to obtain a relatively hard (3 GPa) coating with a hydrophobic nature [contact angle ( H 2 O )=90°].