Glow Discharge Optical Emission Spectrometry - Activities and Opportunities in the Field of Depth Profile Analysis

Glow discharge optical emission spectroscopy (GD-OES) as a depth profiling technique is briefly reviewed. The quantification technique based on emission yields, defined as the analytical signal per unit weight of the analyte, is described. Current standardisation work on applications to zinc and aluminium based metallic coatings is reviewed. Recent work on non-conductive applications using radio frequency (RF) sources is presented. It is shown that practical possibilities to determine discharge parameters exist, but is more complex to use than for the DC source. Furthermore, the strong influence of hydrogen on emission yields is demonstrated. A "matrix correction" technique to deal with this problem is discussed. It is also shown that in spite of all the corrective measures, there still exist artefacts not completely understood, making it necessary to do "matrix-matched" calibrations for certain applications. For thin film applications, it is demonstrated that state-of-the-art GD-OES systems are capable of a depth resolution similar to e.g. SIMS and AES. For quantification of very thin layers, the hydrogen correction must be considered. In addition, it is shown that short-lived molecular emission can influence the analytical results. A method to deal with this effect is presented and discussed.