Effects of traces of oxygen on Grimm-type glow discharges in argon †

We report results of studies using Fourier Transform Optical Emission Spectroscopy (FT-OES) to investigate the effects of added oxygen (0.04–0.8% v/v) on observed spectra from a Grimm-type glow discharge, generated in argon plasma with a pure iron sample. Significant changes in the sputter rate and the intensities of atomic lines of the carrier gas and sample in the presence of oxygen are discussed in detail; these changes are greater than those observed with Ar/H2 and Ar/N2 mixtures. A detailed study of spectral line profiles shows changes in self-absorption of Ar I lines due to O2 and H2 traces. The sputter rate for a given Ar/O2 gas mixture is found not to be proportional to current.