High-Current Pulsed Vacuum-Arc Evaporator for Surface-Alloying Technologies

Plasma sources based on vacuum-arc discharge have a big disadvantage due to the high fraction of droplets in plasma flow produced during the operation of cathode spots. To avoid droplets, various kinds of curved magnetic filters are used. We have suggested one more approach to reduce the droplet content in an arc-discharge plasma basing on the intense evaporation of droplets caused by the ignition of ldquodroplet spotsrdquo in a discharge cell. A Penning-type arc discharge provides favorable conditions for the ignition and operation of droplet spots. In such a cell, a uniform plasma column is formed, whose temperature and density are much higher than those of a usual vacuum arc at the same discharge current. A further increase in energy density in the plasma of a reflective-discharge cell could be achieved by means of both the increase in discharge current and B-field optimization. This paper presents the results of the development and characterization of the pulsed plasma-source model combining a well-known high-current vacuum-arc evaporator with a Penning discharge cell. It has been recognized that the ion-current amplitude at the source output is as high as 800 A, plasma density is as high as 10¹⁴ cm^-3, and electron temperature range is 6-8 eV. Those conditions lead to an intensive evaporation of droplets on the fly. The copper film-deposition rate was measured to be at 1.5 nm/pulse, which corresponds to an instantaneous deposition rate of 2000 nm/s. The first results of the use of the evaporator for surface alloying are also presented.