Modified glow discharge spectroscopy for surface analysis of steels

Grimm‐type glow discharge spectroscopy (GDS) was installed and evaluated as an emission spectroscopic source for the analysis of steel surfaces and for the determination of in‐depth concentration profiles. In order to restrict the abnormal intensity fluctuation at the surface layer, which was observed during analysis of 300 Å of the sample surface layer, the third electrode was installed in the light source and a preliminary discharge technique was developed. The purpose of this preliminary discharge is to clean the sample surface and inner wall of the anode pipe, and to produce plasma in the discharge chamber in order to start the main discharge smoothly. By using GDS with this technique (modified GDS) the influence of abnormal fluctuation at the first stage of discharge was completely excluded and the unstable region of the intensity profile at the beginning of discharge was restricted to 10 Å or so. This modified GDS was applied to the analysis of the surface of box‐annealed steel sheets and the determination of changes in composition with depth below the surface. The results were confirmed by an investigation of the in‐depth analysis of the same samples previously conducted with an ion microprobe mass analyzer (IMMA), and this fact revealed the usefulness of modified GDS as a surface analyzer.