Similar to EDS spectra, the peak-to-background ratio (P/B ratio) in EELS spectra increase with the accelerating voltages from 100 kV to 400 kV, resulting in an increase in the detection sensitivity of any trace elements.
The spatial resolution for both the EDS and EELS/EFTEM analyses is improved with the accelerating voltages, since the incident electron beam spread decreases with an increase in the accelerating voltage.
Note that low accelerating voltage electron beams can enhance the sensitivities for EELS and EDS because the reduced the acceleration voltage increases the ionization cross-section, which is determined by the overvoltage ratio.
With increasing accelerating voltage:
-- The scattering cross-section for ionization decreases,
-- Signal decreases, but background decreases even quicker,
-- To maximize the signal-to-background ratio, increase the accelerating voltage.