Al and Zn film deposition using a vacuum arc plasma source with a refractory anode

The radially expanding plasma plume generated in a Hot Refractory Anode Vacuum Arc was used to deposit thin Al and Zn films on glass substrates. The electrode separation was 10 mm, arc time varied up to 165 s, and current (I) was 100–225 A. The cathode was a water-cooled Al or Zn cylinder. A graphite anode with 9 or 30 mm height was used with the Al cathode, and 10 or 30 mm height Mo anode was used with the Zn cathode. A mechanical shutter controlled the substrate exposure onset and duration (15 s) to the anodic plasma. The distance from the arc axis to the substrate (L) was varied between 80 and 165 mm. The film thickness was measured with a profilometer, and macroparticle (MP) presence on the coating surface was examined by optical microscopy. found that the deposition rate increased as a function of time to a peak, and then decreased to a steady-state value. The peak occurred sooner using the 9 mm anode than with the 30 mm anode. The peak deposition rate increased and the peak time decreased with I. The steady-state deposition rate was larger for Zn (~ 2 μm/min) than for Al cathodes (~ 1 μm/min) at I = 225 A and L = 110 mm. The arc voltage for Al was ~ 20–22 V and for Zn it was 11 V. The deposition rate peak appeared due to MPs evaporating from the hot anode, where they had initially condensed during the conventional arc stage when the anode was still cold. This effect was significant with low melting temperature Al and Zn cathodes, and negligible with Cu and Ti cathodes studied previously.