Characterization of a 1 kA vacuum arc plasma gun for use as a metal vapour deposition source

Abstract

The deposition characteristics of a magnetically collimated plasma jet produced by a 1 kA vacuum arc plasma gun were determined. The ion current flux was determined by measuring probe and wall currents, and the spatial distribution of the deposition rate was determined by measuring the coating thickness distribution along sample coupons. The heat flux carried by the plasma jet was determined by measuring the temperature rise of a thermally isolated probe. The various measurements were compared with each other and with published measurements of cathode-spot-emitted ion currents and ion energies. Ion current fluxes up to 0.3 A cm -2 and 0.6 A cm -2 were obtained for copper and aluminium respectively, with arc currents in the 400–600 A range. Continuous deposition rates of up to 0.3 μm s -1 were obtained. The average enregy per deposited particle ranged between 130 and 170 eV. Comparison of the deposition rate with the ion current, and published measurements of the average degree of ionization, suggests that the sticking coefficient of impinging ions is in the range 0.3–0.7.