The influence of Cr and Ni doping on the microstructure of oxygen containing diamond-like carbon films

Non-hydrogenated diamond-like carbon (DLC) films doped with metals and oxygen were deposited by direct current magnetron sputtering. The influence of chromium and nickel on the surface morphology, elemental composition, bonding structure, adhesion force, optical transmittance and nanohardness of the films was characterized by atomic force microscopy (AFM), energy dispersive X-ray spectroscopy (EDX), multi-wavelength Raman spectroscopy, UV–VIS–NIR spectrophotometry and nanoindenter. The surface roughness was reduced with the addition of Cr (7.4 at. %) or Ni (8.9 at. %) into DLC films. The EDX measurements indicated that the addition of Cr increased the oxygen content by ~37%, while Ni reduced it by ~50%, compared to the oxygen doped DLC film. The microRaman analysis indicated that the G band shifted to a higher wavenumbers range, became narrower and the sp³/sp² sites fraction ratio decreased for the metals doped DLC films. The nanohardness values of the sputtered doped DLC films varied in the range of 4.5–7.6 GPa. It was observed that the Ni-DLC film showed the highest adhesion force value and was optically opaque.