SURFACE AND CORROSION CHARACTERISTICS OF A-C-H FLUOROCARBON FILMS/

Fluorocarbon films were deposited on type 301 stainless steel substrat es from mixtures of hexafluoroetbane (HFE) or hexafluoroacetone (HFA) and acetylene and argon in a radio-frequency (13.56 MHz) plasma discha rge. A 10 nm thick polysilicon interlayer was deposited prior to fluor ocarbon film deposition to obtain good adhesion. To prevent film failu re, a-C:H layer was deposited on the polysilicon layer prior to fluoro carbon film deposition, resulting in a-C:H/fluorocarbon composite film structures. The influence of the feed gas composition on the properti es of the layered structure was investigated. Surface energies of the films were calculated from the film contact angle values obtained with water and diiodomethane. The composition of the surface layer of thes e films was characterized using X-ray photoelectron spectroscopy (XPS) . The resistance offered by these a-C:H/fluorocarbon film structures t o anodic breakdown in an electrolyte containing 0.1 M NaCl and 0.1 M N a2SO4 was studied using a potentiostatic technique. The anodic current density for the coated type 301 stainless steel samples was at least 3 orders of magnitude smaller than that for the bare sample and more t han an order of magnitude smaller than that observed with samples coat ed with only the (equally thick) a-C:H layer. The resistance offered b y the layered coatings to solution penetration increased with increasi ng fluorine content in the films.