Influence of bonding environment on nano-mechanical properties of nitrogen containing hydrogenated amorphous carbon thin films

High quality nitrogen incorporated hydrogenated amorphous carbon (a-C:N:H) thin films have been grown, using radio frequency-plasma enhanced chemical vapor deposition technique, under varied self biases from −25 to −400 V. Presence of nitrogen in carbon–nitrogen network and their bondings with carbon and hydrogen is confirmed by time of flight-secondary ion mass spectroscopy, energy dispersive X-ray analysis, and Fourier transform infrared spectroscopy measurements, respectively. By deconvoluting FTIR spectra, the various sp3CHn and sp2CHn bonding as well as % sp3 and sp2 fractions are estimated, which further correlated with nano-mechanical properties of a-C:N:H films. Observed maximum hardness and elastic modulus as 42 and 430 GPa, respectively in a-C:N:H film deposited at −100 V reveal superhard behaviour of coating. Residual stress in a-C:H:N films is found to be lower due to nitrogen incorporation that further decreases with increasing self bias. In addition, load versus displacement curves have also been employed to calculate various other nano-mechanical parameters, which further correlated with self bias as well as estimated % sp3 and sp2 fractions.