Instructions for Use of
1. To test for stray electrons and x-rays in a TEM column, measure the Ni
K
/MoK
count ratio with the electron beam near the center of the
test specimen and in the center of a grid square. Typical values for this
ratio are in the range of 3 to 7 for modern TEMs. This test should not be
performed if you use a molybdenum condenser aperture.
2. To test for the total contribution of the instrument to the EDS spectrum
background, measure the total integrated counts, P (above background), in
the NiK peak and the flat background B500
integrated over 500 eV
(the average of the two regions on either side of the peak). The
peak/background ratio is P/B = 50 x P/B500. For 100 to 200 kV
accelerating voltage and probe diameters in the range 20 to 200 nm, P/B
should be at least 1000, and more modern instruments may give a value closer
to 3000.
3. Measurement of the full width at half maximum of the NiK peak {FWHM
(Ni)} allows the energy resolution of the EDS detector using MnK
radiation to be estimated as FWHM(Mn) 
0.926 x
FWHM(Ni). For a light-element detector, FWHM(O) should be lower by a factor
of 1.6. Thereference for the assumption of the 0.926 factor is Bennett and
Egerton, J. Microsc. Soc. Amer. 1 (1995) 143-150.
It is based on OK and NiK FWHM's
measured on both Si(Li) and Ge detectors.
4. The collection solid angle of the EDS detector (in sterad) is given by
omega = 4.05 x P/(t x 
x I), where P is the characteristic
NiK
counts recorded in a live time of seconds with a probe
current of I picoamperes, measured using a picoammeter connected to the TEM screen, to a
Faraday cup or if to a spectrometer made by Gatan, Inc., to the flight tube and t
( 50) is the thickness in nm of the NiO film.
5. For windowless and thin-window EDS detectors, the OK
/NiK
count ratio is typically 0.2. The theoretical value is 0.73. If the
measured ratio decreases with time, check for a buildup of ice or
hydrocarbon on the detector or on the window.
6. For E-axis calibration in electron energy loss spectroscopy, the OK edge should appear at 533 eV and the NiLedge at 854 eV if they are measured at the point of maximum slope. A measurement of the areas under these two edges provides a test of the EELS quantification procedure.
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