Fabrication And Research On CNx Films

Since Liu and Cohen predicted thatβ-C₃N₄ has the hardness and bulk modulus, which is comparable to diamond or higher than diamond after theoretic calculation, carbon nitride films have attracted a lot of attention around the world for their excellent properties. In this dissertation, CH_X films were deposited on hard alloy YG8 by DC or RF magnetron sputtering. The composition, bonding structure, adhesion, and tribological behavior of CH_X films were researched. The influence of substrates corrosion, middle layer and high press post-treatment on structure and properties of CH_X was studied. Moreover, the influence of substrate kinds on structure and properties of CH_X was studied by apply W₁₈Cr₄V and Si (100) substrates.To discuss physical mechanism of thin film growth and improve the thin film quality, the microstructures of carbon nitride was simulated by the method of molecular dynamics and deposition dynamics of C, N atoms and C2, N2, CN clusters were studied by the first-principle method.Fourier transform infrared spectroscopy ( FTIR ) and X-ray Photoelectron spectroscopy (XPS) results showed that C-N, C=N, C=N, C-H and N-H bond existed in CH_X films. RF magnetron sputtering is in favor of the bonding of C and N, the adhesion of film and substrate and the wear resistance of CH_X films. DC magnetron sputtering is in favor of lubricating ability of CH_X films. Substrate bias has some effect on the bonding of C and N, the adhesion of film and substrate, decrease of adhesive wear and decrease the roughness of films.It is also indicated that the deposition of TiN and Si₃N₄ middle layers is in favor of the adhesion of film and substrate. TiN layer has better effect on adhesion and bonding of C and N. It is also concluded that TiN middle layers can reduce the friction and raise the wear resistance of CH_X films. High press post-treatment can reduce the friction of CH_X films evidently.CH_X films were also deposited on W₁₈Cr₄V substrate. The adhesion of CH_X/TiN film on W₁₈Cr₄V substrate is lower than that on YG8 substrate. Substrate bias or Ti transition layer can improve the adhesion and raise the wear resistance of CH_X films. When CH_X films were deposited on Si(100) substrate,α,βphases of carbon nitride can be found in CH_X films. Higher deposition power is in favor of the crystallization of C₃N₄ and decrease the roughness of films.Discover module in Materials Studio has been applied to study microstructures of carbon nitride. The simulated results indicate that the coordination polyhedron of C crystal state of C₃N₄ is tetrahedron. In the liquid state of C₃N₄, the coordination number of C and N decreases. The distribution of bond angle and bond length widens remarkably and the structure is disordered for liquid C₃N₄. The distribution of bond angle and bond length in amorphous phase C₃N₄ is similar to that in crystal C₃N₄. It indicates that the coordination polyhedron in crystal C₃N₄ is the same as that in amorphous phase C₃N₄. The coordination number of C and N in amorphous phase C₃N₄ decreases respectively and graphite type structure increases.The deposition courses of C, N atom and C2, N2, CN on different surface were simulated by molecular dynamics and the first-principle method. The results show that C and N atoms can be attracted chemically by WC (100),Si(100) and W₁₈Cr₄V (110) surfaces. C and N atoms adsorbing on W₁₈Cr₄V (110) are most stable. The adsorbing behavior of C2, N2, CN clusters is different from that of C, N single atoms. C2 and CN clusters can be attracted chemically by WC (100), Si(100) and W₁₈Cr₄V (110) surfaces while CN cluster cannot be attracted chemically by WC (100) and Si (100) surfaces. Chemical adsorbing energy of CN cluster on Si (100) surface is higher than that on WC (100) and W₁₈Cr₄V (100) (110) surfaces sufficiently. Si (100) surface is most fit for the growth of CH_X film. It is presumed that in the sputtering process C and N are both under cluster state when they combined with substrate surface.