Deposition of Ti-Si-C-Ag Nanocomposite Coatings as Electrical Contact Material

This paper is a brief review of our recent work and a follow up study on nanocomposite coatings comprising nanocrystalline TiC embedded in an amorphous SiC matrix (nc-TiC/a-SiC) with and without Ag additions applied as electrical contacts. These coating materials are deposited at very high deposition rates (>10 μm/h), to meet industrial demands of high productivity. Here we consider Ti-Si-C-Ag nanocomposite coatings with Ag content in the range of 0-22 at.% deposited in a pilot-plant or an industrial deposition system by dc magnetron sputtering from compound targets onto Si(100) and SiO₂(100) substrates. The microstructure, electrical, and mechanical properties of the coatings were studied with transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, electrical contact resistance, resistivity, and nanoindentation measurements. Varying the deposition parameters bias and pressure within ranges typical of coating processing had no effect on the structure. A variation was, however, observed for the contact resistance, that was determined to be in the range 400-900 mΩ at a contact force between 1.9-2.65 N. The coatings with highest Ag content had the lowest contact resistance.