=================================================================================
For EELS analysis, the final energy resolution of the system is limited by the energy spreads of the beam at the electron source and due to the spectrometer optics. The resulting “degraded” spectrum is given by,
 [2637]
where,
H  The acquired spectrum,
W  The true (nondegraded) spectrum,
p  The Point Spread Function (PSF) of the system.
Note that a monochromator for the electron source or data deconvolution is necessary in the frontiers of TEMEELS if the energy spread of the available electron source in TEM is larger than the intrinsic fine structures of spectra.
Comparing to using monochromation system, a less costly method to improve energy resolution is mathematical deconvolution. This process utilizes an experimentally determined function which represents the inherent energy spread of the electron optics system in the EM.
For instance, Nelayah et al [1] have demonstrated the successful application of the RichardsonLucy deconvolution algorithm to improve the energy solution acquired from silver nanoprisms. More examples in Figure 2637 shows the effects of energy resolution enhanced by energydrift correction and deconvolutions in the EEL spectrum of hBN. The EEL spectra are acquired with an exposure time of 80 ms, a probe current of 100 pA and a high energydispersion (0.021 eV ch^{–1}). Figure 2637 (a) shows a blindsum spectrum with a wide energy spread of 0.48 eV in FWHM (full width at half maximum) due to the energy drift during data acquisition. Figures 2637 (b) shows the improvement by the energydrift correction, reflecting the inherent high energyresolution of a cold field emission electron gun (CFEEG). Figures 2637 (c) and (d) show the boron Kedge spectra before and after drift correction, respectively, with π* peak reduced from 1 to 0.52 eV. Figures 2637 (e) and (f) shows further improvement by RL (RichardsonLucy) and ME (maximumentropy) deconvolution, respectively.
Figure 2637. Lowloss and coreloss spectra of hBN. (a) and (c) raw spectrum, (b) and (d) spectra after drift correction, and (e) and (f) deconvoluted B Kedge ELNES using RL algorithm and ME algorithm, respectively.
Adapted from [2]
[1] Nelayah, J. et al. Mapping surface plasmons on a single metallic nanoparticle. Nature Phys. 3, 348353 (2007).
[2] Koji Kimoto, Kazuo Ishizuka, Teruyasu Mizoguchi, Isao Tanaka and Yoshio Matsui, The study of AlL23 ELNES with resolutionenhancement software and firstprinciples calculation, Journal of Electron Microscopy 52(3): 299–303 (2003).
