Microstructure and mechanical properties of Al–Si–N transparent hard coatings deposited by magnetron sputtering

✍ Scribed by A. Pélisson; M. Parlinska-Wojtan; H.J. Hug; J. Patscheider

• Publisher: Elsevier Science
• Year: 2007
• Tongue: English
• Weight: 859 KB
• Volume: 202
• Category: Article
• ISSN: 0257-8972
• DOI: 10.1016/j.surfcoat.2007.05.094

✦ Synopsis

Motivated by the success of transition metal nanocomposite hard coatings, a new optically transparent coating based on the Al-Si-N ternary system was developed. Al-Si-N thin films were deposited by reactive DC magnetron co-sputtering of Al and Si targets in an Ar/N 2 atmosphere at 200 °C and 500 °C sample temperature. The structure and mechanical properties of the coatings were investigated by XPS, XRD, TEM, nanoindentation and mechanical profilometry. The chemical composition was varied from pure AlN to Al-Si-N with 23 at.% of Si. The films are crystalline with the hexagonal AlN structure up to 12-16 at.% of Si as found from XRD and TEM analyses. A shift of X-ray diffraction peaks indicates a substitutional incorporation of silicon in the h-AlN lattice up to a solubility limit identified at 6 at.% of Si. By further increasing the silicon content, a nanocomposite nc-Al 0.44 Si 0.06 N 0.5 /a-SiN x is formed. From TEM analysis it follows that the crystalline material consists of columnar grains composed of crystallites with a (002) texture. The mean crystallite size decreases from 60 nm to about 5 nm upon addition of silicon, as revealed by XRD. Hardness measurements show a diffuse hardness maximum exceeding 30 GPa around 10 at.% of Si. At this value a negligible residual stress in the coating is measured.