Consideration of the chemical reactivity of trace impurities present in a glow discharge

Abstract

Optical and mass spectrometric diagnostics were applied in a study of the chemical reactivity of the plasma impurity species in an r.f. glow discharge source. Copper, Fe and Ta metals and Ta powder-based compacted discs were chosen as test cathodes. A cryogenic coil incorporated within the discharge source was used in the investigations of the potential interactions. Significant increases were observed in the sputtering gas and cathode matrix ion signals, as well as the ground- and excited-state populations of these species with cryogenic cooling. The relative reactivities of the matrix-element species with water-related species in the plasma and the significance for glow discharge-based analytical techniques are discussed.