Comparison of atomization and ionization processes in direct current, radiofrequency and microsecond pulse discharges

Abstract

Glow discharge spectrometry has attracted growing interest in using faster pulsed power supplies as a diagnostic tool. In this study, a comparison of dc, rf and microsecond pulse (µs-pulse) GDs was made to determine the relative efficiency of the discharge power. The sputtering rates of the different power modes as evidenced by direct mass loss measurements showed the greatest mass loss for the µs-pulse. Emission spectra of the three sources were also analysed. The emission signal intensity for Cu from the µs-pulse was two orders of magnitude greater than those from the others. It was also noted that the ratios of the atom versus ion emission intensities differed among the three modes. Optical temperature measurements of N₂⁺ rotational and Fe¹ excitation emission spectra were investigated. The N₂⁺ rotational temperatures varied between 400 K for the µs-pulse discharge up to 650 K for the dc power source, whereas a constant Fe¹ excitation temperature of 3600–3900 K for all modes was measured.