Improving mechanical properties of amorphous carbon nitride films by titanium doping
Xu P., Li JJ., Wang Q., Wang ZL., Gu CZ., Cui Z.
Titanium doped amorphous carbon nitride (a-C Nx) films with a nitrogen content of ∼24 at. % were synthesized by radio frequency magnetron sputtering method. The effects of incorporating Ti on the mechanical properties of a-C Nx films were investigated by nanoindentation, scanning electron microscope, x-ray diffraction spectra, and x-ray photoelectron spectroscopy, respectively. It was found that nanometer sized TiN crystallites were formed and embedded in the a-C Nx matrix, causing an enhancement of hardness from ∼28 to ∼40 GPa in the a-C Nx films. The improved mechanical properties with addition of Ti are attributed to the densified microstructure due to the development of fine grain size of TiN and s p3 C-N bonds. These TiN nanocrystal grains are separated by an amorphous phase, preventing dislocation movement and hence enhancing the hardness of the film. The increased s p3 C-N bond fraction induced by incorporation of Ti also plays an important role in the enhancement of hardness. © 2007 American Institute of Physics.