Stress reduction dependent on incident angles of carbon ions in ultrathin tetrahedral amorphous carbon films

Abstract

We presented the combined experimental and simulation study on stress evolution as a function of incident angles of carbon ions for the ultrathin tetrahedral amorphous carbon films (ta-C). The residual stress was found about 3.6 +/- 0.1 GPa for the incident angle of C ions with range of 0 degrees-30 degrees, while it decreased significantly to 2.8 GPa with the incident angle of 60 degrees. Different with the previous reports, noted that in this case both the sp(3) content and mechanical properties of film were not deteriorated. Taking molecular dynamics simulation, it was in particularly concluded that the critical relaxation of distorted C-sp(3) bond lengths and bond angles played key role on the unusual stress reduction mechanism. The results provide a route to fabricate the ultrathin ta-C films with low stress and high hardness for the precision wear resistant applications. (C) 2014 AIP Publishing LLC.