Hot refractory anode vacuum arc: A new plasma source for metallic film deposition

A new mode of the vacuum arc, the Hot Refractory Anode Vacuum Arc (HRAVA), was investigated as a plasma source for depositing coatings. Arc currents of 155-340 A were sustained for periods of up to 120 s between a water-cooled Cu source cathode, and a non-consumable refractory anode, which was heated by the arc. Cu coatings were deposited on ground stainless steel and glass substrates. A shutter controlled when and how long the substrate was exposed to the plasma. The coating rates were measured by weighing the substrates, and the macro particles (MPs) presence on the coating surface was examined by optical microscopy. Films that formed in a 30-s exposure at the beginning of a 175-A arc, when it operated in the cathode spot mode, were heavily contaminated with MPs. The density of MPs with diameters of between 3 μm and 50 μm was approximately 10³ mm^-2. However, with a 30-s exposure, which began 30 s after arc initiation, by which time the arc was in the HRAVA mode, the MP density was reduced to approximately 1 mm^-2. The HRAVA deposition rate was approximately 1-2 μm/min onto substrates placed at distances of approximately 110-120 mm from the arc axis. The HRAVA deposition rate is comparable to filtered cathode spot vacuum arc deposition, but over a much larger deposition area.