Structural and optical properties of doped amorphous carbon films deposited by magnetron sputtering

Abstract Amorphous carbon films containing oxygen and bismuth were deposited by direct current magnetron sputtering. The microstructure and optical properties of the films were measured as a function of magnetron sputtering power by atomic force microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, UV–VIS–NIR spectrophotometry, and null-ellipsometry. The oxygen concentration in the films was in the range of 19–21 at.%. It was determined that the deposition rate of amorphous carbon films increased and the surface roughness of the films changed from 1.2 nm to 1.7 nm with the increase of magnetron sputtering power. The microRaman analysis demonstrated that the D band shifted to a lower wavenumbers range and the fraction of the sp 2 carbon sites decreased as the power increased. X-ray photoelectron spectroscopy revealed that sp 3 /sp 2 ratio in the films varied between 0.74 and 0.98. The optical transmission of the films in the visible region was in the range of 60–90%. The optical band gap and the refractive index of the films depend on the dopant concentration and the sp 2 site fraction.