Operation/Measurements of EDS
- Practical Electron Microscopy and Database -
- An Online Book -
This book (Practical Electron Microscopy and Database) is a reference for TEM and SEM students, operators, engineers, technicians, managers, and researchers.
The operation procedure of EDS measurement is relatively simple. Basically, it includes:
i) Withdraw any objective aperture;
ii) Select an incident beam energy which is higher than twice the highest peak energy;
iii) Ensure that the beam current is not too high in order to avoid saturation and destruction of the detector;
iv) Insert EDS aperture (if there is any);
v) Position the incident electron beam;
vi) Insert the EDS detector.
On the other hand, in EDS measurements (especially for quantification), other potential problems which mostly need to be taken care of are:
i) Energy calibration.
ii) Identification of characteristic X-rays. When an element is identified, all X-ray peaks in its possible family, especially the members with relatively low intensities, must be marked off.
iii) Identification of artifactual peaks, including Si escape peak, sum peaks and the peaks arising from stray excitation in the specimen chamber.
iv) The peak overlap.
v) The X-ray absorption.
vi) The fluorescence.
vii) The EDS signal counts should be high enough to recognize peaks, but should not be too high (e.g. <3000 counts/sec, or alternatively dead time < 30~50%) to minimize sum and escape peaks.
viii) Applicable X-ray lines to identify the elements from beryllium to uranium are in the energy range of 0.1 keV to 20 keV. In order to provide a proper over-voltage to excite the X-ray lines in the upper half of this range, the energy of the incident electron beam should be in the range 20-30 keV.
ix) Long spectrum accumulation times should be used to acquire high-energy X-ray lines.
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