Deposition of mechanically hard amorphous carbon nitride films with high [N] / ([N] + [C]) ratio

Mechanically hard amorphous carbon nitride films were prepared by a combination of negative radio frequency (RF) bias voltage (− VRF) applied to a substrate and chemical vapor deposition using a decomposition reaction of BrCN with a microwave discharge flow of Ar. A pulsed operation of − VRF was effective when − VRF > 40 V to avoid excess sputtering of films. The [N] / ([N] + [C]) ratios of films were ≈ 0.5 irrespective of the application of − VRF. The maximum hardness was 36 ± 10 GPa for the film obtained under the conditions of − VRF = 100 V, a pulse period of 1000 s, and a pulse-on time of 800 s. According to the IR spectra, the intensity of the stretching vibration of the CN bond increased by the application of − VRF. The Raman spectra showed increases in the relative intensity and width of the D-band. From these observations, the mechanism of film hardening was discussed.