The Preparation And Tribological Properties Of Fluorinated Diamond-like Carbon Film

Plasma enhanced chemical vapor deposition （PECVD） system was used toprepare fluorinated diamond like carbon （F-DLC） film.The effects of variousdeposition parameters on the composition, microstructure and properties of thedeposited films were investigated systematically.The relationship of themicrostructure and the mechanical, tribology properties and surface characteristicof the films were discussed. The low fiction properties of F-DLC film in theambient air environment were studied, and set up the tribological model of F-DLCto analyze the low friction mechanism. The Forming conclusions of this thesis weredrawn as following:The influences of the substrate bias frequency, precursor gases and substratetemperature on the microstructure of the films were investigated. The resultsshowed that the the form of fluorine film is CF₃, CF_X（X=1,2,3）, HFC=C<. Thesp³/sp²rate of the films first decreased and then increased in the range of0.86-0.63as substrate bias frequency increased. In addtion, Control precursor gasflow rate and the ratio of CF₄, CH₄and H₂was1:10:20, the fluorine content washighest （2.1at.%）. The sp³/sp²ratio of films first increased and then decreased inthe range of1.03-2.04as substrate temperature increased.These could be attributedto the effects of the ion current densiy, ion energy and doped elements.The influences of the substrate bias frequency, precursor gases and substratetemperature on the mechanical properties of the films were investigated. It is foundthat the film with highest hardness of11.8GPa was obtained at substrate biasfrequency of40kHz, and the film with lowest friction coefficient of0.07wasobtained at substrate bias frequency of60kHz.When flow ratio of CF₄, CH₄and H₂is1:10:20, the film hardness is as high as16.1GPa and show excellent tribological,the fiction coefficent is0.012. The film exhibited the low friction and highhardness in ambient air under substrate temperature of400℃. The temporalfriction coefficinet and hardness was0.015and17.3GPa, resp^ectively.Fluorine-doped hydrogenated amorphous （a-C:H:F） carbon films, then thehydrogenated one was treated in CF₄plasma to make the films surface fluorinemodified. Both films were studied in terms of the thickness, surface morphologyand tribological properies. The results showed that the CF₄etching effect is verystrong, the thickness of F-P-a-C:H film is less half than that of the original a-C:Hfilm. A large CF₄plasmas etch and inject the surface, so the surface of a-C:H:F filmappears many protuberances. As load increased to30N, a-C: H: F film exhiabited excellent tribological properties, the friction coefficient and was0.011and thetemporal wear rate5.64×10^-9mm³/N·m,The wear debris’ microstructure of a-C:H:F and F-P-a-C:H film wereinvestigated. The results show that, compared to film, the wear debris of the a-C: H:F film has higher sp²hybrid carbon content （94at.%）. Body doped F was good forgraphitization and orderliness. the structure, thus improving the tribologicalproperties of amorphous carbon films.A possible mechanism of the role of F in the friction process of F incorporatedamorphous carbon film was proposed that F obstructs the saturation of freehydrogen to dangling δ bond and induced more sp³C transformed to sp²C, so thewear debris of a-C:H:F film are with much higher sp²C content （94at.%）compared to the original a-C:H:F film.