PEELS COMPOSITIONAL PROFILING AND MAPPING AT NANOMETER SPATIAL-RESOLUTION

Elemental analysis of inhomogeneous materials can now routinely be per formed at the nanometer level, using characteristic EELS signals. Majo r progress in spatial resolution and accuracy in quantification has re cently been fostered by the practical implementation of the spectrum-i mage mode in a FEG-STEM environment. The required hardware and softwar e have been elaborated to record, store and process these large amount s of data. In the present contribution we describe the routines which have been implemented for extracting quantitative elemental maps from spectrum-images: (i) the standard background subtraction method for wh ich the availability of several hundreds of energy loss channels acros s the edge to be quantified reduces the errors and bias in background modelling and extrapolation; (ii) a non-negative multiple-least-square s routine for fitting the experimental spectrum acquired for each pixe l with a linear combination of reference edges, if possible recorded d uring the same scan. The impact of these new tools is demonstrated in a series of situations encountered in materials science (composite mat erials, metallic multilayers) which all require nanometer resolution a nd accurate data processing of complex spectra with overlapping edges.