The hydrogen effect as a function of discharge parameters - investigations of the variation of emission yield in glow discharge plasmas

Abstract

It is well known that traces of hydrogen in the glow discharge plasma enhance or suppress the intensities of other spectral lines, in this work termed “the hydrogen effect”. In this work, the focus is on the variation of the hydrogen effect as a function of the discharge parameters, for the purpose of developing effective correction methods in quantitative depth profile analysis. A simple, but effective experimental method was employed: The intrinsic contamination of the source leads to an increased amount of hydrogen in the plasma at the beginning of the discharge, which is rapidly reduced with sputtering time. Thus, by recording the intensity depth profiles of multi-element bulk reference materials, the influence of hydrogen on several emission lines can be observed. The decay or increase in intensity, correlated to the intensity of the hydrogen emission line, gives the desired information. Systematic investigations by varying current and voltage in a considerable range provided a good matrix of data to find a model describing these variations. Furthermore, renewed investigations of the variation of emission yields (EY) with discharge parameters have led to a model which has been used to correct the obtained data for the hydrogen intensities, so as to represent the actual content of hydrogen in the plasma. The information extracted from these studies is expected to be of great importance for routine depth profile analysis, as the hydrogen correction is a relevant tool in software quantification algorithms. Existing correction models for the hydrogen effect do not take variations in the discharge parameters into account. This work clearly shows that it is necessary to implement such variations for accurate correction.