Correlation between the chemical bonding and the physical properties of the CNx films obtained by pulsed laser deposition from C targets in low-pressure N2

Carbon–nitride thin films were deposited by XeCl* (λ=308 nm, τFWHM≅30 ns) multipulse excimer laser irradiation of graphite targets in low-pressure (1–100 Pa) nitrogen atmosphere. We investigated the chemical bonding formation between the C and N atoms, and its influence upon the optical and mechanical properties of the obtained structures. We found that these properties strongly depend on the deposition parameters. These in turn determine the nitrogen content and the sp3/sp2/sp carbon atoms hybridization ratio of the synthesized material. According to our results, the increase of the nitrogen pressure or laser fluence in an attempt to obtain CNx thin films with higher N/C ratio does not lead to the formation of the theoretically predicted low-compressibility, high density, extremely hard β-C3N4 structure with the C atoms in the sp3 hybridization state.