Superposition of two plasma beams produced in a vacuum arc deposition apparatus

Two plasma beams of different materials were produced from Ti, Zr, or Nb cathodes in a triple-cathode vacuum arc deposition apparatus. The cathodes were arranged in a circle centered on the system axis. The plasma produced by the cathode spots was transported through a straight plasma duct with an axial magnetic field, into a sample chamber, in which a single Langmuir probe, an array of probes, or a substrate could be mounted 560 mm from the cathode plane. The saturation ion current produced by one cathode, or by the simultaneous operation of two different cathodes, was measured in vacuum and in a 0.13-2.7 Pa nitrogen background. The spatial distribution of the composition of coatings deposited during simultaneous operation of different cathodes in nitrogen was also studied. It was shown that the ion current produced by each single cathode decreased by a factor of 20-100, and by a factor of ten during simultaneous operation of two cathodes, when the nitrogen pressure was increased from vacuum to P=2.7 Pa. During simultaneous operation of two cathodes, the ion saturation current was less than the sum of the ion currents produced by each cathode individually when P<0.4 Pa, while the simultaneous ion current was larger than the sum of the individual ion currents when P/spl ges/0.4 Pa.