Practical Electron Microscopy and Database

In EELS measurements, the electron beam current density should be low enough to minimize the beam damage on the materials while still producing a sufficient signal-to-noise ratio. For instance, to minimize the electron-beam-induced chemical reduction of Mn⁴⁺ in Mn-containing minerals [1], the data acquisition can be done by spreading the electron beam for a low irradiation rate, e.g. smaller than 2 × 10⁴ e/nm²/s. At this condition, the acquisition time for each spectrum can be relatively long, e.g. 8^–10 s. If the counts for a single spectrum are not sufficient to produce pronounced sharp peaks, a series of spectra should be summed to improve counting statistics such that the integrated dose for each accumulated spectrum is more than 2 × 10⁶ e/nm².

[1] Garvie, L.A.J. and Craven, A.J., (1994) Electron-beam-induced reduction of Mn4+ in manganese oxides as revealed by parallel EELS. Ultramicroscopy, 54, 83–92.