The effect of nitrogen concentration on the properties of N-DLC prepared by helicon wave plasma chemical vapor deposition

Abstract

Nitrogen-doped diamond-like carbon (N-DLC) films were synthesized by helicon wave plasma chemical vapor deposition (HWP-CVD). The mechanism of the plasma influence on the N-DLC structure and properties was revealed by the diagnosis of plasma. The effects of nitrogen doping on the mechanical and hydrophobicity properties of DLC films were studied. The change of the ratio of precursor gas flow reduces the concentration of film-forming groups, resulting in the decrease of growth rate with the increase of nitrogen flow rate. The morphology and structure of N-DLC films were characterized by scanning probe microscopy (SEM), Raman spectroscopy (Raman), X-ray photoemission spectroscopy (XPS). The mechanical properties and wettability of N-DLC were analyzed by ultra-microhardness tester and JC2000DM system. The results show that the content ratio of N+ and N2+ is positively correlated with the mechanical properties and wettability of N-DLC films. The enhancement hardness and elastic modulus of N-DLC are attributed to the increase of sp3 C-N bond content in the film, reaching 26.5 GPa and 160 GPa respectively. Water contact measurement shows that the increase of the N-bond structure in N-DLC makes the film have excellent hydrophobic properties, and the optimal water contact angle has reached 111.2 degree. It is shown that the HWP technology has unique advantages in the modulation of functional nanomaterials.