Boronated tetrahedral amorphous carbon (ta-C:B)

We have deposited boronated highly tetrahedral amorphous carbon (ta-C:B) films with low stress using a filtered cathodic vacuum arc (FCVA). The sp³ fraction, hardness and resistivity were measured as a function of the ion energy and were found to reach a maximum above 50 eV for B concentrations of 2 and 4%. The most significant result we found was that highly tetrahedral a-C:B film (sp³≈80%) with low stress (1-3 GPa) with B concentrations up to 4% could be obtained. The B in the films was found to be predominantly (∼75%) sp² bonded. The bond length and angle of ta-C:B found using the radial distribution function were similar to ta-C, confirming its tetrahedral nature. Additionally, the stress in the films did not vary with the ion energy or sp³ fraction unlike in undoped ta-C films. The ta-C:B films also exhibited higher resistivity than ta-C. This is believed to be related to the reduction of defect density measured by electron spin resonance, although the optical band gap was similar to ta-C (2.0-2.4 eV).