Thermal stability of Cr-doped diamond-like carbon films synthesized by cathodic arc evaporation

Cr-doped diamond-like carbon (DLC) films were synthesized using a cathodic arc evaporation (CAE) process. The thermal oxidation behavior of Cr-doped DLC films was investigated using thermal gravimetric analysis (TGA) and differential thermal analysis (DTA). The phase identification and microstructural examinations were conducted by X-ray diffraction, scanning electron spectroscopy (SEM), transmission electron spectroscopy (TEM), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS) in order to understand the characteristics of Cr-doped DLC films. The as-deposited Cr-doped DLC film exhibits a lamellar structure observed by TEM. A significant weight loss of film results from the thermal oxidation of carbon occurred at 290 to 342 °C. At the temperature higher than 342 °C, slight weight gain of specimen was observed due to the thermal oxidation of the underlying CrCxNy and CrN interlayer. By heat-treated specimens from 200 to 400 °C, Raman spectra reveal the increase of ID/IG value conforming to the graphitiation process of the Cr-doped DLC films. Finally, surface reactions of the annealed films using XPS analysis were discussed.