Electron microscopy
 
EDS Measurements of Al (Aluminum)
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Figure 1754 shows an Al Kα (1.486 keV) EDS profile obtained with an old HpGe detector. This severe distortion of the peak shape and the large shift of the peak position due to extremely incomplete charge collection make the measurements at energies below ~2 keV (especially just above the energy of Ge L absorption edges from 1.2 to 1.4 keV) impossible.

EDS profile obtained with an old HpGe detector

Figure 1754. Al Kα (1.486 keV) EDS profile obtained with an old HpGe detector.

As discussed on page4650, X-ray absorption is a function of the energy of X-rays. Low energy peaks will be more strongly absorbed than high energies ones. For thick TEM samples, k-factor correction due to X-ray absorption is needed in order to accurately quantify EDS measurements. Table 1754 lists Al-examples of thicknesses at which the thin-film approximation is no longer valid due to X-ray absorption effects in specific materials.

Table 1754. Examples of limits to the thin-film approximation caused by X-ray absorption: Maximum thicknesses of thin specimens for which the absorption correction (or error) is less than ±10% and ±3%.

Material

10% error in kAB
3% error in kAB
Absorbed X-ray lines
Primary X-ray lines
Thickness (nm)
Al-7% Zn
336 94 Al Kα Al Kα (1.486 keV) and Zn Kα(8.63 keV)
CuAl2
40 12 Al Kα Al Kα (1.486 keV) and Cu Kα (8.04 keV)
NiAl
32 9 Al Kα Al Kα (1.486 keV) and Ni Kα (7.471 keV)
Ag2Al
33 10 Al Kα and Ag Lα Al Kα (1.486 keV) and Ag Lα (2.984 keV)
Ag3Al
31 9 Al Kα and Ag Lα Al Kα (1.486 keV) and Ag Lα (2.984 keV)
Al2O3
113 14 Al Kα and O Kα Al Kα (1.486 keV) and O Kα (0.525 keV)

 

 

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