Characterization and formation of nanocrystalline diamonds in a-C/N films by filtered cathodic vacuum arc plasma

Nitrogen incorporated diamondlike carbon (a-C/N) films were deposited on silicon (111) wafers using a 90°-bend magnetic-filtered cathodic arc plasma system. The structure and properties have been studied by transmission electron microscope (TEM), glancing incident X-ray diffraction (GXRD), scanning electron microscope (SEM), electron spectroscopy for chemical analysis (ESCA), Raman scattering (Raman), and Fourier transform infrared spectrometer (FTIR). For the a-C/N film depositions, a highly ionized energetic plasma was used to produce carbon ions with varying ion energies to form various carbon bonding in the film. Applying a bias voltage to the substrate can enhance the ion energy. In this study, nanocrystalline diamond clusters were observed in the a-C/N film because of the existence of a higher fraction of sp3 bonding contents. Our previous work indicated that the DLC films can have a higher hardness with a negative substrate pulsed bias between −100 and −350 V, and a maximum sp3 bonding content at about −350 V according to the result of ESCA. The sp2 bonding content seems to be related to the Raman ID/IG ratio. The nitrogen content was also found to increase with substrate bias voltage. The maximum incorporation of nitrogen to the a-C/N film is up to N/C=0.38 (ESCA) using the 90°-bend magnetic-filtered cathodic arc plasma system. The hardness rises up to a maximum value of 12.18 GPa at appropriate substrate bias.