In this work, we provide new insight on the influence of the precursor (CH4 vs. C2H2) on the mechanical properties of a-C:H coatings synthesized in a hybrid PECVD/PVD process. For a given set of plasma parameters, the films synthesized in CH4/Ar gas mixture are found harder than the ones prepared in C2H2/Ar atmosphere despite their lower sp3 density and similar hydrogen content. This unusual behavior is attributed to different molecular organization of the polymeric network constituting the films. The latter is explained considering the influence of the chemical nature of the film-forming species on the cross-linking and branching degree of the films. The whole set of our results unambiguously demonstrates that additional factors than the sp3 and hydrogen content have to be considered for explaining the mechanical properties of a-C:H layers. The purpose of this work is to enlarge the comprehension about the influence of the chemical precursor (CH4 vs. C2H2) on the mechanical properties of amorphous hydrogenated carbon film (a-C:H) synthesized by a PECVD/PVD hybrid method. The whole set of our results enables to highlight the influence of other factors (e.g., cross-linking degree, branching character) than the sp3 and hydrogen content for determining the hardness of the a-C:H layers.
- a-C:H coatings
- branching character
- cross-linking degree
Technological Platform Synthesis, Irradiation and Analysis of Materials
Facility/equipment: Technological Platform