Paper SE-TuM4
Al-Si-N Thin Films: Nanocomposites and Solid Solutions

Tuesday, November 10, 2009, 9:00 am, Room C4

Thin films consisting of Al-Si-N were prepared by reactive magnetron sputtering from elemental targets in an Ar/N₂ reactive atmosphere at 200°C. The system shows a solubility limit for silicon at around 6 atomic %. Correspondingly the Al-Si-N system forms, as a function of the silicon content, either a solid solution or a two phase nanocomposite structure,. To understand the the properties and formation of the nanocomposite nanoscaled multilayers were used as a simplified model system. Coatings with a total thickness of about 1 micron and consisting of alternating layers of h-AlN or h-Al_1-xSi_xN (5 nm) and a-Si₃N₄ (from 0.25 nm to 2.0 nm) were prepared. The hardness as well as the residual stress state are strongly influenced by the thickness of the Si₃N₄ layer and the silicon content of the crystallineAl-Si-N layer. Maximum hardness values of 33 GPa are reached for a Si₃N₄ layer thickness of 0.35 nm, whereas the stress state can be tuned between – 1.5 and + 1.5 GPa. Both High Resolution TEM and XRD showed that, for Si₃N₄ layer thicknesses below 1 nm, the Si₃N₄ layers grow heteroepitaxially on AlN. The implication for the hardness of isotropically deposited solid solution and nanocomposite thin films of Al-Si-N will be discussed.