Tetrahedral amorphous carbon films prepared by magnetron sputtering and dc ion plating

Highly tetrahedral, dense amorphous carbon (ta‐C) films have been deposited using rf sputtering of graphite by an unbalanced magnetron with intense dc Ar‐ion plating at low temperatures (<70 °C). The ratio of the argon ion flux to neutral carbon flux Φi/Φn is about 5. The film density and compressive stress are found to pass through a maximum of 2.7 g/cm3 and 16 GPa, respectively, at an ion plating energy of about 100 eV. Experiments with higher ion flux ratios of Φi/Φn=10 show that it is possible to deposit carbon films with densities up to 3.1 g/cm3 and sp3 contents up to 87%. Deposition of ta‐C in this experiment when the energetic species is Ar appears to require a minimum stress of 14 GPa to create significant sp3 bonding, which contrasts with the continuous increase in sp3 content with stress when the energetic species is C ions themselves. These results are used to discuss possible deposition mechanisms.