Deposition, characterization and applications of nitrogen-rich amorphous carbon nitride films

Nitrogen-rich amorphous carbon nitride films (with relative nitrogen contents in the order of 50-57%) have been deposited by means of inductively coupled plasma CVD utilizing chemical transport reactions from a solid carbon source. A discussion of the deposition process reveals that atomic nitrogen from the plasma reacts with the solid carbon source to yield CN. radicals which are the film forming species, thus guaranteeing a high nitrogen content. The resulting films have been thoroughly characterized with respect to their crystallinity, composition, and bonding structure. It was revealed that they possess a low density of only 1.8 g cm(-3), and are composed mainly of structural units containing C=N double bonds. As a consequence, their mechanical and tribological properties are poor, preventing their application as wear protecting coatings. Optical and electrical investigations revealed among other features an optical Tauc gap of 2.1 eV and a resistivity up to 10(11) Omega cm. As a consequence of their low density, the films are able to incorporate reversibly water and may therefore be suitable as humidity and gas sensors. A comparison of the properties of these nitrogen-rich CN, films with the reported data of layers with lower nitrogen concentrations shows that a number of properties (e.g., density, hardness, extinction coefficient) possess a strong correlation with the nitrogen content. These observations are discussed in view of the search for the synthesis of superhard diamond-like carbon nitride modifications.