Characteristics of industrially manufactured amorphous hydrogenated carbon (a-C:H) depositions on high-density polyethylene

Industrially high-density polyethylene (HDPE) was successively covered by two types of amorphous hydrogenated carbon (a-C:H) films, one more flexible (f-type) and the other more robust (r-type). The films have been grown by radio frequency plasma-enhanced chemical vapor deposition (RF-PECVD) technique with acetylene plasma. The surface morphology of both types has been studied by atomic force microscopy (AFM) and scanning electron microscopy (SEM). Contact angle measurements and Raman spectroscopy analysis were done to investigate the surface wettability and carbon chemical composition. Both types display similar morphology and grain growth pattern. Contact angle measurements revealed surface modifications especially at smaller r-depositions with a pronounced hydrophilic behavior. The f-depositions remain almost unchanged. For high r-depositions a rearrangement of the carbon composition is found and related to a growth of sp2 hybridized carbon species, despite of the hydrogen content. The values of the average grain heights are correlated to the values of the average grain areas and are localized in a limited area, indicating a given regularity during the different carbon depositions.