I am using a Fei Quanta 200 equipped with an EDAX detecting unit and the Genesis Software (version 4.52). This behavior seems to appear in a variety of samples. The attached elemental mappings are mapping of Au film stripes on Si substrate (fabricated for testing)
From left to right images are:
Backscattered Electron image, Au elemental mapping, Si elemental mapping.
Contrast in EDS mapping is indicative of compositional change. Also please see the film thickness variations in your case. Or you may provide more detail for discussion.
I think there are two main reasons for the stripes and you should find out if one of these can be found here.
1) Contamination. You could show us the C-map of this region. It should be homogeneous. If you adjust your beam in the middle of the measured area before the EDX measurement you could deposit carbon during this procedure.
2) Instability of the electron beam current. You could quantify the mappings and calculate everything to 100%. This helps often.
A third possibiliy is charging. I think in your case the measured area is conductive. But it can be that you have a nonconductive piece outside of the measured area which is disturbing the EDX mapping.
Not much to add to Martin Arndt answer.
You might want to test mapping at different scanning speeds : scanning quicker should limit beam/charging issues but still be sensitive to Carbon contamination. Depending on whether you still see the horizontal contrast change or not, it will help you pinpoint their source.
This is typically what I get when sample charging, but I'm working mainly on non-conductive samples.
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