Interlaboratory comparison of XRF analysis on thin films, including alloys, oxides, multilayers, and a lithium-ion battery material

Abstract

We report on a comprehensive, international interlaboratory comparison of multiple thin film samples, including pure metals, stoichiometric oxides, multilayers consisting of three different metals, non-stoichiometric alloys, and a lithium-ion battery material based on nickel, manganese, and cobalt oxides. The thickness of the layers ranged from a few tens of nanometers to about one micrometer, depending on the type of thin film. The participants of the interlaboratory comparison analyzed the samples using X-ray fluorescence analysis and a relative standard deviation of the results ranging from about 3% to 17% was observed, with thicker alloy samples tending to perform worse. An extensive pre-characterization scheme was used in the form of different complementary analytical techniques such as X-ray reflectometry, time-of-flight secondary ion mass spectrometry, and X-ray tomography. Synchrotron-based reference-free X-ray fluorescence analysis measurements were used to determine physically traceable results. Using such a variety of independent methods ensured a robust overall validation approach. This corroborates that calibration samples for such thin films can be designed, produced, and qualified in a flexible and straightforward manner. These calibration samples can easily be integrated into process control for a variety of application fields, including X-ray fluorescence analysis and other techniques.