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. plasm a 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, t he effects of residual stress in the film on adherence and the failure mode of silicon-containing diamond-like carbon film deposited on different subs trate materials are investigated. The results show that all the coated film s suffer a compressive stress the magnitude of which depends on coating pro cess parameters. By raising r.f. power for deposition the internal stress i s increased and the scratch critical load is improved. On the other hand, b y raising the substrate temperature the thermal stress is increased and the scratch critical load is decreased slightly. The scratch tests for the fil ms coated on both silicon wafer and Coming 7059 glass reveal tensile failur e mode whereas for the one coated on Ti-6Al-4V alloy reveals chipping failu re mode. From the observation of the results of indentation test for the fi lms coated on Ti-6Al-4V, the sample deposited at higher r.f. power and lowe r substrate temperature exhibits less damage which demonstrates that the fi lm obtained has a better adherence behavior. (C) 1999 Elsevier Science S.A. All rights reserved.