The effect of nitrogen incorporation in DLC films deposited by ECR Microwave Plasma CVD

Highlights: • DLC and DLC:N thin films have been fabricated by the Electron Cyclotron Resonance Microwave Plasma Chemical Vapor Deposition (ECR- MP CVD) System at room temperature. • DLC:N thin films were obtained by nitrogen doping. • Surface of the films was very smooth. • XPS, RAMAN and FT-IR measurements confirmed the formation of sp² C=N and sp³ C-N bonds. • DLC and DLC:N films were found to be very hard. • All the films showed high optical transparency in the IR region. - Abstract: Diamond like carbon (DLC) and nitrogenated diamond like carbon (DLC:N) films have been deposited by electron cyclotron resonance microwave plasma chemical vapor deposition (ECR-MP CVD) on Si (1 1 0), steel and glass substrates, using CH₄ and N₂ as plasma source. The effect of nitrogen doping on the optical, electrical, structural and mechanical properties of films was investigated. X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR) and Raman spectroscopy results showed that sp² bonded carbon phases increased while the sp³ bonded carbon phases decreased by nitrogen doping. Microhardness measurements showed a decrease in hardness (from 75 to 69 GPa) according to nitrogen incorporation. Average transmittance of all the films was over 90% and band gap energy (E_g) of the films decreased due to increasing nitrogen flow rate. The film morphology was studied using the atomic force microscopy (AFM). Electrical properties were characterized by Hall measurement. Undoped DLC was p-type with a conductivity of 9.81 × 10⁻⁶ (Ω cm)⁻¹. DLC films became n-type by nitrogen doping. The best conductivity value for the nitrogen doped DLC films was found 2.77 × 10⁻⁵ (Ω cm)⁻¹. PL spectra of DLC and DLC:N films showed three peaks at 405 nm (3.06 eV), 533 nm (2.32 eV) and 671 nm (1.84 eV)