University of Huddersfield Repository Jones , Benjamin and Ojeda , J . J . Substrate and material transfer effects on the surface chemistry and texture of diamond - like carbon deposited by plasma - enhanced chemical vapour deposition

Diamond-like carbon (DLC), a thin amorphous carbon film, has many uses in tribological systems. Exploiting alternative substrates and interlayers can enable control of the hardness and modulus of the multi-layer system and improve wear or friction properties. We utilise XPS and AFM to examine DLC concurrently coated on an epoxy interlayer and a steel substrate by plasma enhanced chemical vapour deposition (PECVD). sp 2 /sp 3 ratios were calculated both by deconvolution of the XPS C1s line and analysis of the C KLL Auger spectrum. Altering the substrate causes changes in the carbon bonding configuration, evident with the same trend through both analysis methods, though with differing absolute values, related to hydrogen and oxygen content. There is significant variation in the microscale surface texture, exhibited both by average roughness values and size and uniformity of surface asperities. This suggests that alteration to the film surface structure is a factor to be considered in addition to interface adhesion, hardness and elastic modulus, in investigating substrates and interlayers for tribological coatings. Examination of a DLC film separately produced on a steel substrate, in comparison with that produced concurrently with DLC coating of epoxy, shows the possibility of effects on the chemistry of the film through transfer of material from adjacent samples within the plasma deposition, related to heating, out-gassing or sputtering processes. The possibility of such contamination has implications in coating parameter design and coating of multiple samples with PECVD.