The anodic vacuum arc and its application to coating

Abstract

A steady vacuum arc discharge is obtained by a special design of the electrodes. This new type of arc discharge is ignited in vacuum and is sustained by metal vapor produced at a consumable anode. The new discharge generates a gas- and droplet free metal vapor plasma expanding into the ambient vacuum (10−4 mbar) and producing thin metallic films at the surface of substrates. An analysis of the metal–plasma at the position of a possible substrate for different materials (Al, Cu, and Ag) and arc currents >20 A leads to the following results: electron densities, 1015 –1017 /m3 ; electron temperatures, 0.2–1 eV; degree of ionization, 1%–25%; ion energies, 5 eV. Coatings are generated with deposition rates up to 100 nm/s and show the following properties: purity 99.9 %, polycrystalline structure with grain sizes between a few and some 100 nm, within 2% density of the respective bulk material, good optical properties, and an electrical conductivity rather close to that of the bulk material. The coatings show good adhesion, which can be enhanced by accelerating the ions towards the substrate.