TEMPERATURE STABILITY OF FLUORINATED AMORPHOUS HYDROGENATED CARBON-FILMS

Amorphous hydrogenated carbon films are of high technological interest as protection coatings owing to their special properties such as high hardness, chemical inertness, and infrared transparency. However, the applications are restricted owing to the poor thermal stability of th ese coatings. Fluorinated amorphous hydrogenated carbon (a-C:H:F) film s are produced by r.f plasma deposition from a mixture of acetylene an d trifluoromethane with a self bias of - 300 V. The structural changes upon annealing in an argon atmosphere of films with fluorine concentr ations varying from 0.1% to 20% are investigated. Raman spectra were m easured on each film for different annealing temperatures. The spectra are decomposed into single Gaussians and the ratio of the intensities of the D peaks to the G peaks is used as a measure of the transition from the amorphous structure to the more graphitic-like structure. Thi s transition temperature can be used as an indication of the structura l stability of these films upon annealing. The transition temperature versus the fluorine concentration is found to decrease for increasing fluorine concentration, showing, therefore, a decreasing temperature s tability upon fluorination. Furthermore, this decrease shows a linear dependence on the fluorine concentration.