The effect of residual stress on adhesion of silicon-containing diamond-like carbon coatings

The silicon-containing diamond-like carbon film was deposited by r.f. plasma CVD with reactant gases of CH4, SiH4 and Ar on the substrates of silicon wafer, Coming 7059 glass and Ti-6Al-4V alloy respectively. In this study, the effects of residual stress in the film on adherence and the failure mode of silicon-containing diamond-like carbon film deposited on different substrate materials are investigated. The results show that all the coated films suffer a compressive stress the magnitude of which depends on coating process parameters. By raising r.f. power for deposition the internal stress is increased and the scratch critical load is improved. On the other hand, by raising the substrate temperature the thermal stress is increased and the scratch critical load is decreased slightly. The scratch tests for the films coated on both silicon wafer and Coming 7059 glass reveal tensile failure mode whereas for the one coated on Ti-6Al-4V alloy reveals chipping failure mode. From the observation of the results of indentation test for the films coated on Ti-6Al-4V, the sample deposited at higher r.f. power and lower substrate temperature exhibits less damage which demonstrates that the film obtained has a better adherence behavior. (C) 1999 Elsevier Science S.A. All rights reserved.