This paper aims to study the effect of low nitrogen doping on the microstructure and mechanical properties of hydrogenated diamond-like carbon films. By using unbalanced magnetron sputtering and plasma enhanced chemical vapor deposition (PECVD) composite technology

tungsten carbide transition layer and hydrogenated diamond-like carbon films with different nitrogen content (a-C:H(N)) were prepared on 316 stainless steel and silicon substrates. The microstructures of the films were characterized by Raman spectroscopy

X-ray diffraction analysis (XRD)

X-ray photoelectron spectroscopy (XPS)

and scanning electron microscope (SEM). The hardness and residual stress of the films were characterized by micro and nano mechanical comprehensive measurement system and film stress measuring instrument. Results show that with nitrogen doping

carbon-nitrogen bond (CN) was formed in the films and mainly existed in the form of C=N bond

and the ratio of C=N/CN decreased with the increase of nitrogen content. When the nitrogen content increased from 0 to 0.12 at%

the ID/IG ratio of the film decreased rapidly

the ratio of sp2C=C/sp3C-C decreased from 0.65 to 0.563

whereas the hardness of the films remained unchanged at about 20.4 GPa

and the residual stress decreased from 3.35 GPa to 1.31 GPa. With the increase of nitrogen content

the ratio of sp2C=C/sp3C-C increased

the hardness of the films decreased rapidly

and the residual stress decreased slowly. The effect of nitrogen doping on the microstructure of DLC films has a critical value of 0.12 at%. When the amount of nitrogen doping is lower than this value

it promotes the formation of sp3 hybridization

and the film has high sp3 hybridization

while the sp3 hybridization of the films decreases with the increase of nitrogen

and the sp3 hybridization decreases. The films with higher hardness and lower residual stress can be obtained with low nitrogen doping.