The properties of N-doped diamond-like carbon films prepared by helicon wave plasma chemical vapor deposition

In this paper, N-doped diamond-like carbon (DLC) films were deposited on silicon substrates by using helicon wave plasma chemical vapor deposition (HWP-CVD) with the Ar/CH₄/N₂ mixed gas. The surface morphology, structural and mechanical properties of the N-doped DLC films were investigated in detail by scanning electron microscopy (SEM), x-ray photoelectron spectroscopy (XPS), Raman spectra, and atomic force microscopy (AFM). It can be observed from SEM images that surface morphology of the films become compact and uniform due to the incorporation of N. The maximum of the deposition rate of the films is 143 nmmin^-1, which is related to the high plasma density. The results of XPS show that the N incorporates in the films and the C-C sp³ bond content increases firstly up to the maximum (20%) at 10 sccm of N₂ flow rate, and then decreases with further increase in the N₂ flow rate. The maximum Young’s modulus of the films is obtained by the doping of N and reaches 80 GPa at 10 sccm of N₂ flow rate, which is measured by AFM in the scanning probe microscope mode. Meanwhile, friction characteristic of the N-doped DLC films reaches a minimum value of 0.010.