Effect of W-doping on the structure and properties of DLC films prepared by combining physical and chemical vapor deposition

High power impulse magnetron sputtering (HiPIMS) has received extensive attention in the field of preparing diamond-like carbon (DLC) films due to the stable discharge, the high ionization rate and the large plasma density. However, the low deposition rate and poor adhesion to substrate of the DLC have always been a challenge for its application. In this paper, the physical and chemical vapor deposition (PVD & CVD) are combined to fabricate W doped DLC (W-DLC), in which W is sputtered from the target through HiPIMS (PVD) and DLC is synthesized by plasma enhanced CVD (PECVD) in the atmosphere of Ar/C2H2. The characteristics, mechanical and tribological properties of DLC/W-DLC films are explored using SEM, EDS, Raman, XPS, nanoindentation and nanoscratch, respectively. It exhibits that the W-DLC films encompass a smooth surface and a composite structure with W2C or WC1-x embedded in sp3-rich DLC. The adhesion and hardness of DLC film improved significantly by W doping, i.e., the hardness increases from 6.59 GPa to 22.44 GPa. Besides, the deposition rate and wear resistance also improved. It is also found that the W content decreased from 19.81 to 10.19 at.% and the sp3/sp2 ratio increased from 0.39 to 0.75 with increasing C2H2 flow rate.