Effect of Carbon Source Incident Angle on Structure and Properties of Ultrathin Tetrahedral Amorphous Carbon Films

The tetrahedral amorphous carbon (ta-C) films were fabricated by 45° double-bent filtered cathodic vacuum arc technique, and the wettability, surface energy, roughness, surface topography, friction coefficient and microstructure evolution of ultrathin ta-C film as functions of incident angles of carbon ions were investigated. The results reveal that as the incident angle of carbon ions increases from 0° to 60°, the water contact angle of films slightly increases from 77.6° to 82.4° and the glycerin contact angle of films slightly increases from 64.7° to 71.2°, indicating that all the films are hydrophilic. The total surface energy decreases from 33.9 mJ/m² to 28.0 mJ/m². The slight increase of observed contact angle is attributed to the decrease of surface energy and increase of surface roughness. Also, the average friction coefficient increases from 0.140 to 0.217. According to the near edge X-ray absorption fine structure data, little change for the hybridized sp³ bond content in the deposited ta-C films appears, regardless of the change of incident angle in a range of 0°–60°.