Limitations in the X‐ray microanalysis of thin foils in a scanning transmission electron microscope

SUMMARY The X‐ray microanalysis of thin foils has been investigated using a scanning transmission electron microscope fitted with an energy dispersive spectrometer. Thin foils prepared from an iron‐nickel and an aluminium‐zinc‐magnesium‐copper alloy have been observed and analysed. For foil thicknesses between 200 and 300 nm the X‐ray intenstiy ratios are consistent with X‐ray absorption characteristics. For regions less than 200 nm thickness the measured intensity ratios increase by up to a factor of 5. These results have been explained in terms of a solute enriched or depleted surface layer developed during the preparation procedure.