The Effect of Chromium on the Microstructure and Transparency of Diamond-like Carbon Films

Cr-doped diamond-like carbon (DLC) films were formed on silicon and glass substrates by magnetron sputtering (MS). The surface morphology, elemental composition, bonding structure, and transparency of the as-deposited films were analyzed by atomic force microscopy (AFM), the energy-dispersive X-ray spectroscopy (EDS), multiwavelength micro-Raman spectrometer, and UV-VIS-NIR spectrophotometer. The study revealed that the oxygen concentration in the Cr-DLC films increased as the Cr content increased. The surface roughness of the films was slightly reduced when the Cr content was ~9.2 at.%, and further increase in the Cr content up to 13.1 at.% stimulated the growth of the highest-roughness Cr-DLC films. The micro-Raman analysis showed that the G peak position shifted to a higher wavenumber, and the sp² bond fraction increased as the Cr concentration in the DLC films rose. The optical transmittance of the Cr-DLC films was reduced by up to 30% compared to DLC coatings due to the increased graphitization process caused by chromium addition.