TF_Quantif:: a procedure for quantitative mapping of thin films on heterogeneous substrates in electron probe microanalysis (EPMA)

Electron probe microanalysis (EPMA) of stratified specimens has been intensively developed during the last few decades. Several quantification models (PAP, XPP, X- PHI) have led to many commercial software packages being widely used. However, all these software packages require an accurate description of the analysed sample because they are all based on the fundamental assumption that each layer of the sample is uniform in its structure and its composition. This is useful in the case of local analysis but may be problematic in the case of quantitative scanlines or quantitative maps. Indeed, a sample may not be homogeneous in all the analysed areas; this could lead to variations in the detected x-ray intensities and as a consequence to wrong results. Therefore, efforts have been carried out to analyse thin films on heterogeneous substrates. A method based on the measurement of the backscattering coefficient during x-ray microanalysis was developed in our laboratory. This method, called 'Auger formalism', gave good results in the case of thickness determination of pure coating on heterogeneous substrates and was also successfully applied in the case of multi-elements coating for concentration determination. However, in the case of concentration determination, this method requires knowledge of the film thickness. Thus, the aim of this work is to develop a new quantification procedure which is based on the same approach as previously adopted. This procedure allows a complete determination of both concentration and thickness from x-ray intensities of the coating associated with backscattering measurement. This method is called 'TF_Quantif'. The performance of this quantification procedure is illustrated by different examples of application (thickness and composition maps determination of bi-element coatings on heterogeneous substrates).