Trace Impurity Determinations and Element Distribution Measurements in Advanced Coating Systems

The awareness that the quality of many technologically relevant coatings depend on the presence of trace element impurities and their distributions has led to increased demands for analytical techniques for quality and process controls. Common analytical methods in routine use provide valuable, but incomplete, understanding of coating chemistries, and thus cannot fully address the current needs. In addition, due to the basic limitations of techniques for chemical analyses involving sample digestions, element analysis of advanced coatings has becoming a growing domain of direct sampling analytical methods.

Among the currently available direct sampling methods, glow discharge mass spectrometry (GDMS) is one of the best suited techniques for comprehensive measurements on advanced coatings. The exceptionally large dynamic range allows internal standardizations using the main element(s) as the internal standards. This combined with the very low dependency of the calibration factors on the sample composition provides simple and highly universal calibration methods needing no strictly matrix-matched reference values. Although GDMS has been widely used for ultra-low element analysis for the last two decades, its advantages for chemical analysis of coatings and the chemistries between coatings and substrates has not yet been fully utilized. Additionally, the modulated GDMS test methods currently under development, which are based on pulsed GD sources, are very promising for depth dependent distribution measurements of thin films or complex multi-layered coatings with nm range depth resolutions.