Scanning Electron Microscopy and X-Ray Microanalysis

50

4

4.3.3 Range of X-ray Production

As the beam electrons scatter inelastically within the tar-

get and lose energy, inner shell ionization events can be

produced from U 0 down to U = 1, so that depending on E 0

and the value(s) of Ec represented by the various elements

in the target, X-rays will be generated over a substantial

portion of the interaction volume. The “X-ray range,” a

crude estimate of the limiting range of X-ray generation,

can be obtained from a simple modification of the

Kanaya–Okayama range equation (IV-5) to compensate

for the portion of the electron range beyond which the

energy of beam electrons has deceased below a specific

value of Ec:

RAKO− ()nm=−27.6()/ZE0.89ρ  016 ..^71 Ec^67 

(4.12)

As-generated electron-excited X-ray spectrum of carbon

X-ray photon energy (keV)

Intensit

y

1e+7

1e+6

1e+5

1e+4

1e+3

1e+2

1e+1

1e+0

0510 15 20

. Fig. 4.12 Spectrum of pure carbon
as-generated within the target calcu-
lated for E 0 = 20 keV with the spectrum
simulator in Desktop Spectrum Ana-
lyzer

1e+8

1e+7

1e+6

1e+5

1e+4

1e+3

1e+2

1e+1

1e+0

C

Cu

Au

0510

X-ray photon energy (keV)

As-generated electron-excited X-ray spectra

15 20

Intensit

y

. Fig. 4.13 Spectra of pure carbon,
copper, and gold as-generated within
the target calculated for E 0 = 20 keV with
the spectrum simulator in Desktop Spec-
trum Analyzer (Fiori et al. 1992 )

Chapter 4 · X-Rays