Study Of Structure And Properties Of DLC:Si:F Films With Si And F Co-doping

DLC films with Si and F co-doping（DLC:Si:F films） were deposited on 316 L stainless steel substrates with radio frequency reactive magnetron sputtering by using trifluromethane（CHF₃） and argon as source gases and SiC crystal target.At First, the effect of film thickness on adhesion was studied. The results show that under different powers, both thicker film and thinner film have poor adhesion, the film with thickness of 800 nm or so shows the best adhesion. Then by keeping the film thickness around 800 nm, the relations between the RF input powers and adhesion behavior, friction coefficient, hardness and surface contact angle of prepared DLC:Si:F films with similar thickness were investigated. On the basis of the analysis of the infrared and Raman spectra of the films, the modulation effects of RF input powers on the films structure and properties and modulation mechanism were studied from physical factors（mainly hardness and surface roughness） and chemical factors（mainly structure of the films and content of each group）.The results show that the hardness and surface roughness of the samples are not significantly different, but the difference of adhesion is obvious. The adhesion of DLC:Si:F thin films prepared by 190 W input power is close to the best（about 11N）, which is significantly higher than that of fluorinated diamond like carbon film（F-DLC）. The water contact angle of films prepared at 190 W input power was also close to the maximum, and the hydrophobicity was slightly less than that of the F-DLC film, but the hydrophobic property was not changed. It can be speculated that the main factors affecting the adhesion and hydrophobic properties of the films are chemical factors, namely, the bonding way of each atom（Group） in the film and the content of each group.The mechanism of input power on the structure and properties of DLC:Si:F thin films was revealed by the Raman and IR spectra of the films. On the one hand, the input power will directly affect the energy of space Ar ion and the sputtering yield of SiC ceramic target;On the other hand, the input power will result in the decomposition of the source gas CHF₃,which makes the concentration of Si, C,-CF,-CF₂, F* and other groups different obviously.F* will modulate the content of Si-C bond and C network correlation degree in the films.The F content(I_C-F/IC-C), especially HFC=C< vibration and F₂C=C< intensity ratio(I_HFC=C</I_F2C=C<) had a direct impact on the films properties. The increase of C=C and Si-C bond is helpful to improve the adhesion of the film, while the decrease of F content will lower the surface hydrophobicity of the film.Controlling of RF input power can achieve effective modulation on the structure and properties of DLC:Si:F thin films prepared by radio frequency reactive magnetron sputtering. These conclusions can provide theoretical basis and technical support for the further development and application of thin films.