Description
Cathodic arcs are a powerful technique for depositing a wide range of thin films, from diamond-like carbon to refractory materials such as tantalum. The University of Sydney’s filtered cathodic arc (SPArc) thin-film deposition system is driven by a high-current pulse that ejects material from cathode spots as they move across the cathode surface. The resulting highly ionized arc plasma is guided through a curved magnetic filter and directed onto a substrate, where energetic ions deposit to tailor thin films for a range of materials.
A key feature of the SPArc is the retrograde motion of the cathode spots—their movement in a direction opposite to that expected from the Lorentz force. The cathode consists of a 50 mm diameter disk of the material to be deposited with a trigger pin at its centre. A high-voltage trigger pulse initiates several cathode spots near a trigger pin, after which the current-carrying spots separate and move across the cathode surface due to retrograde motion. Ideally, the spots reach the cathode edge as the pulse terminates, producing near-uniform erosion of the cathode. This erosion pattern maximizes cathode utilization and minimizes downtime associated with cathode replacement.
Understanding the trajectories of the cathode spots for different cathode materials is therefore essential for optimizing SPArc operation. In this study, high-speed photography was used to characterize spot trajectories on carbon (C), aluminium (Al), copper (Cu), and titanium (Ti) cathodes. For Al and Ti, the spots move to the cathode edge in a manner consistent with a simple model developed to describe their motion. In contrast, Cu spots exhibit a tendency to “stick” before reaching the cathode edge. For the C cathode, the spots remain localized near the trigger pin, indicating markedly different behaviour from that observed for the metallic cathodes.
| I am the presenting author | Yes |
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