Amorphous carbon films rich in diamond deposited by magnetron sputtering

In this work evidence is presented that unhydrogenated amorphous carbon films approaching diamond can be deposited by rf magnetron sputtering at room temperature. In situ spectroscopic ellipsometry (SE) studies, performed in the energy range 1.5–5.5 eV, have been used to monitor and characterize the firms during deposition, as well as to define the range of deposition conditions which produce films rich in sp3 C-C bonds. The internal stress developed in these films during deposition was also measured by the cantilever laser technique. A strong dependence was found between the sp3 volume fraction, calculated by analyzing the SE data, and the internal stress in the films. The effects of bias voltage and thickness on the film stress were also examined and are discussed. It was finally observed that films beyond a critical thickness and with an internal stress level above 6–7 GPa became metastable when exposed to air at atmospheric pressure.