On the upper limit of sp³ content in tetrahedral amorphous carbon film

The morphological properties of the tetrahedral amorphous carbon (ta-C) films deposited by the filtered cathodic vacuum arc (FCVA) technique have been studied over the carbon ion energy range 15 to 200 eV. All the films studied are very smooth with a roughness below 0.6 nm. The minimum roughness (∼0.12 nm) occurs at the highest sp³ content. The lateral feature size increases with ion energy. There appear to be two different growth mechanisms before and after the peak sp³ content. The morphological result suggests an upper limit sp³ content of about 89% in the ta-C films deposited by FCVA technique.