Relationship between the optical and mechanical properties of fluorinated amorphous carbon thin films

Fluorinated amorphous carbon (a-C:H:F) thin films were grown from CH4/CF4/A r gas mixtures using a 13.56 MHz radiofrequency (RF) plasma source. The eff ect of fluorine incorporation on the mechanical properties of the films was investigated by depth sensing indentation, while Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray reflectivity (XRR) and ellipsometr y measurements were exploited to study their vibrational, structural and op tical properties. While raising fluorine content in the film, visible Raman results show that the sp(2) carbon sites undergo a gradual ordering into g raphitic clusters, which are responsible for a higher optical absorption. N anoindentation measurements showed decreased elasticity of the film, as wel l as decreased hardness upon fluorine incorporation. A clear correlation be tween the mechanical properties and the optical constants was found as a fu nction of fluorine content in the film. (C) 2001 Elsevier Science B.V. All rights reserved.