AVS 65th International Symposium & Exhibition
    Advanced Surface Engineering Division Tuesday Sessions
       Session SE+PS-TuM

Paper SE+PS-TuM6
Time-resolved Analysis of the Cathodic Arc Plasma from Nb-Al Cathodes

Tuesday, October 23, 2018, 9:40 am, Room 202C

Session: Plasma-assisted Surface Modification and Deposition Processes
Presenter: Robert Franz, Montanuniversität Leoben, Austria
Authors: S. Zöhrer, Montanuniversität Leoben, Austria
A. Anders, Lawrence Berkeley National Laboratory, Leibniz Institute of Surface Engineering (IOM), Leipzig, Germany
D. Holec, Montanuniversität Leoben, Austria
R. Franz, Montanuniversität Leoben, Austria
Correspondent: Click to Email
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.

By using a time-resolved method in combination with pulsed arcs and a comprehensive Nb-Al cathode model system in this work, we investigate the influence of cathode composition on the plasma, while making the influence of neutrals visible for the observed time frame. This model system consists out of three different Nb-Al compositions with the atomic ratios 75/25, 67/33 and 25/75, as well as pure Nb and Al cathodes. The results visualize ion detections of 600 μs plasma pulses, extracted 0.27 m from the cathode, resolved in mass-per-charge, energy-per-charge and time. In addition to high vacuum at a base pressure of 10-4 Pa, the measurements were carried out at three elevated Ar gas pressures: 0.04 Pa, 0.20 Pa and 0.40 Pa. Ion properties were generally found to be strongly dependent on the cathode material in a way that cannot be deduced by simple linear extrapolation. For high vacuum, current hypotheses in cathodic vacuum arc physics applying to multielement cathodes, like the so called “velocity rule” or the “cohesive energy rule”, are tested for early and late stages of the pulse. In addition, the influence of an inert background gas is analysed by comparing the results with those at increased pressure, which show reduced ion charge states, up to a state where mostly Nb2+ and Al1+ ions are detected. Beside Nb and Al ions, time-resolved energy and charge distributions of Ar ions are taken into account, providing further insights on the processes involved.