Changes in the Structure and Properties of Fluorocarbon Coatings under Irradiation with Accelerated C60 Ions

Abstract

The first results of combined deposition of coatings from a beam of accelerated C₆₀ fullerene ions and fluoroplastic vapor (polymerized tetrafluoroethylene, PTFE) are presented. The coatings were formed by condensation of thermally evaporated PTFE on a Si substrate in vacuum under irradiation with a C₆₀ ion beam with an energy of 5 keV passed through a mass spectrometer. The calculated ratio of C₆₀ ions and molecular fragments condensing on the substrate (–CF₂–CF₂–) was chosen close to 1 : 1. The structure of the coatings and chemical bonds have been studied by Raman scattering and X-ray photoelectron spectroscopy, according to which the coating contains about 8.6 at % fluorine. The coating contains ~35% sp³ bonds, with a sp³/sp² ratio of ~0.76, and the main part (up to 50%) of fluorine–carbon bonds is concentrated in the form of polymer chains –CF₂–CF₂–, which are located in a solid carbon matrix; that is, the coating structure is a nanocomposite. Mechanical tests showed high hardness of the coating H ~ 32 GPa with an H/E ratio of ~0.16 (E is Young’s modulus). The coating is characterized by a high contact angle of wetting with distilled water (CA = 98°). Tribological tests showed a coefficient of friction close to 0.18, with low wear of less than 10^–7 mm³/(N m).