Influence of hydrogen on the analytical figures of merit of glow discharge optical emission spectroscopy—friend or foe?

It is well known that the presence of small quantities of hydrogen in an argon glow discharge (GD) causes serious alterations to the excitation and ionisation mechanisms in the GD plasma and hence to the analytical signals. This so-called “hydrogen effect” leads also to a change in the shape of the sputtering crater and its roughness. The present work shows how the manifold effects of hydrogen can be exploited in glow discharge optical emission spectroscopy (GD-OES) in order to improve analytical figures of merit such as analytical sensitivity, detection limits and depth resolution. Other problems caused by the presence of hydrogen, e.g. the occurrence of hydride bands, are demonstrated and discussed. It is shown that start-up phenomena leading to a falsification of the initial part of GD-OES depth profiles can be partially inhibited by controlling the GD source cleanness, and possibly by adding hydrogen.