Quantitative in-depth analysis of iron oxide films by glow discharge spectrometry

A method for the quantitative analysis for oxide films on steels with glow discharge emission spectrometry (GDS) was examined. The sputtering rate and the light intensities were measured with standard samples with oxide films of known composition or known composition and thickness, and apparent emission yields (R_n) for elements were determined. By converting the light intensities to the sputtered amount with the R_n's for an interval in a sputtering profile in an unknown sample, the composition can be obtained from the amount ratio of sputtered elements. The sputtering depth can be calculated from the sputtered amount divided by the density of each element for the sputtering time. The apparent density of oxygen for the depth conversion was estimated to be 1.82 from measurements of standard samples with oxide films of known composition and thickness. The results analyzed by the present method were in consistency with those obtained with another method. The present analysis involves little matrix effect, and facilitates the quantification of the sputtering depth which is difficult to obtain in AES, XPS and SIMS.