Paper VT-WeA12
The Cathodic Arc Plasma from Multi-Element Cathodes

Wednesday, November 1, 2017, 6:00 pm, Room 20

Cathodic arc deposition has been established as one of the standard techniques for the physical vapour deposition of thin films and coatings as it allows the synthesis of a wide variety of materials including metallic films, but also nitrides, carbides and oxides if a reactive background gas is used. In addition, the highly ionised plasma and the achievable high deposition rates allow a variety of control mechanisms to influence the film growth while the manufacturing costs remain rather low due to the short deposition times. With the advent of multifunctional thin films and coatings, the use of multi-element cathodes providing the non-gaseous elements during the synthesis has become an industrial standard. However, a detailed understanding of the discharge properties is vital for the further optimisation of the deposition processes to enable synthesising thin films or coatings with improved properties.

In the present work, the cathodic arc plasma from CrAl and NbAl composite cathodes is studied in detail. The ion energies are measured element, charge state and time resolved in vacuum conditions as well as in the presence of an inert and reactive background gas. Differences in the ion energy and charge state distributions between the plasma from the composite cathodes and corresponding single-element cathodes are noticed. Since it is expected that such differences originate from changes on the cathode surface, namely the formation of intermetallic phases, the erosion behaviour of the cathodes is also analysed. The latter is supported by density functional theory calculations providing additional information about the cohesive energy of the elements which includes the influence of surface texture and temperature. The presence of a background gas generally leads to a reduction of ion energies and charge states. Cathode poisoning effects are mainly observed outside of the main erosion zone. All obtained data are discussed on the basis of correlating the material properties of the cathodes and the plasma properties of the established discharges in order to obtain a comprehensive understanding of the cathodic arc discharge from multi-element cathode and to guide the further development of the deposition of thin films and coatings using such discharges.