Quantitative compositional mapping by electron probe microanalysis with digital imaging

Since the first demonstration of x-ray area scans obtained with the scanning electron microprobe, the production of two-dimensional elemental distribution maps has become a popular adjunct to conventional fixed-beam microanalysis (Cosslett and Duncumb, 1956). In the past, these maps have been generated exclusively by analog signal processing of x-ray signals detected with either wavelength-dispersive spectrometry (WDS) or energy-dispersive spectrometry (EDS). The advent of laboratory computer dedicated to controlling electron microprobes has made possible the quantitative digital compositional map. In the digital method, the beam is stepped over the surface of the specimen, pausing at each step to integrate x-rays for each element or to accumulate an EDS spectrum. An x-y grid of counts is stored and may be displayed as an image or processed into quantitative compositional maps. The EDS and WDS methods each have particular advantages and disadvantages when used for digital mapping. Applications to a variety or problems in materials science are presented to illustrate the capabilities of quantitative compositional mapping by electron microprobe