Scanning Electron Microscopy and X-Ray Microanalysis

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24

X-ray continuum background, as well as artifacts such as

coincidence peaks and Si-escape peaks. The SUM spectrum in

. Fig. 24.6 was calculated from the same Raney nickel XSI
datacube used for. Fig. 24.4. Note that the count axis now
extends to more than 3 million counts, much higher than the
count axes of the individual pixel spectra in. Fig. 24.4 because
of the large number of pixels that have been added together to
construct the SUM spectrum. The characteristic peaks that
can be recognized in the SUM spectrum (scaled to the highest
intensity) represent the dominant, most abundant elemental
features contained in the XSI.  The analyst can select a peak

channel and view the corresponding energy card to reveal the

elemental map for that peak, as shown in. Fig. 24.7. By select-

ing a band of adjacent channels that spans the peak and aver-

aging the counts for each x-y pixel in the set of energy cards,

an elemental image with reduced noise is obtained, as also

shown in. Fig. 24.7. Systematically selecting each of the

prominent characteristic X-ray peaks, total intensity maps for

all of the major elemental constituents can be obtained. The

SUM spectrum can be treated just like a normally recorded

spectrum. By expanding the vertical scale or changing from a

linear display to a logarithmic display, lower relative intensity

Sum Spectrum:

Add the counts from

every pixel in each

energy plane; the

SUM from a plane

becomes the intensity

in the corresponding

energy channel of the

derived spectrum.

X

Y

Counts

Channel (X-ray Energy)

Ni K-L2,3

Al K-L2,3

Ni L-M

Ni K-M2,3

X-ray Energy

100

3000000

2000000

1000000

0

200 300 400 500 600700 800900 1000

. Fig. 24.6 Concept of the SUM spectrum derived from an X-ray spectrum image by adding the counts from all pixels on an individual image at
a specific photon energy, Ep

Chapter 24 · Compositional Mapping