Figure 1754 shows an Al K_α (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.

Figure 1754. Al K_α (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 Table 1754 lists Al-examples of thicknesses at which the thin-film approximation is no longer valid due to X-ray absorption effects in specific materials.