Degradation of EELS and EFTEM Energy Resolution due to Binning
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For an EFTEM image, combining of both vertical and horizontal binning leads to square (or rectangular) image binning. For example, 4 × 4 binning is a combination of 4× vertical and 4× horizontal binning. After binning, the dimension of each pixel in the image becomes greater.

For an EEL spectrum, horizontal (energy) binning leads to spectrum binning. The energy of each channel in the spectrum becomes greater.

If the TEM specimen is very fragile and is easily damaged during the observation, the experiment must be done with the minimum dose of electron beam. In such cases, the signal acquisition is needed to be compromised by costing some benefits. For instance, the counting efficiency of EELS linescan can be optimized at the cost of energy resolution by binning multiple channels. As an example, the EELS of Si in Figure 2232 shows the binning effects on the energy resolution and the background of the spectra. The two spectra were taken at energy dispersions of 0.44 eV/channel and 3.82 eV/channel, respectively. The full-width at half-maximum (FWHM) of the small peak marked by the red arrow is only 2 eV; however, the energy of each channel (pixel) with energy dispersion of 3.82 eV/channel is 3.82 eV. Therefore, such small peak is invisible even though the same EELS system and electron microscope are used for both spectra. Furthermore, the height of the peak marked by the blue arrow is smaller for the greater energy dispersion (3.82 eV/channel).

EELS binning
(a)
EELS binning
(b)
Figure 2232. EEL spectra of Si taken at energy dispersions of 0.44 eV/channel and 3.82 eV/channel, respectively. The two figures (a) and (b) present the same spectra, but in different format. Binning in a spectrum is performed by using greater energy dispersions. Here, 3.82 eV/channel is binning of 0.44 eV/channel by about 9x.

 

 

 

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