ABSTRACT
An X-ray map produced from an electron microscope is nothing more than an image of the sample formed from a selected (and possibly processed) part of the X-ray spectrum. There are several reasons why this is very valuable. A common application is as a qualitative ‘screening’ to identify relatively gross variations in the composition in different parts of a sample, which may then be subjected to more detailed examination. In a large image it can often be difficult to find features of interest; if there is a compositional variation that can be mapped, then the map can show these. Sometimes the map can show an unexpected feature that would not have been found otherwise. In other cases the map provides access to information that would otherwise be hard to determine. A very significant attribute is that the map presents the analytical data in a powerful, easy to interpret way that makes a strong impact on a scientific audience. The saying ‘a picture is worth a thousand words’ applies here. The analyst not only has to determine the composition of the sample, but that information must be transmitted to an audience. Even if all the quantitative data have been acquired by other means, the map can still present this in a simple way, making the time spent recording it worthwhile. Other important applications, which we shall discuss during the course of this chapter, have also been developed.
