Evolution of Structural, Morphological, Mechanical and Optical properties of TiAlN coatings by Variation of N and Al amount

TiAlN thin films deposited on silicon and glass substrates using a reactive DC magnetron sputtering system with different mixture volume of pure nitrogen and argon gases. Phase formation, phase transition, elemental composition, hardness and optical properties are mostly affected by the nitrogen amount in reactive gas. The concentration of Al causes large effects to both the intensity of X ray diffraction and the position of preferred growth orientation. Depending on the Al content, the films either have a single phase cubic TiAlN structure or consist of a mixture of cubic TiN and hexagonal AlN phases with a decrease in the degree of crystallinity. With increasing N-2 amount, the amorphous films with a denser and smoother microstructure similar to the zone T structure developed. AFM results indicated that an increase in Al content resulted in an increase of surface roughness. Experimental data indicates that the hardness is affected not only by microstructure but also by the existence of Al content. The UV-Vis absorbance and transmittance spectra depend on N content. We have also found that the films prepared at lower nitrogen amount have high optical transparent at UV range. The absorption spectra exhibit redshift characteristic with increasing particle size.