Practical Electron Microscopy and Database

Detection of electrons is often accomplished through the use of scintillator, a material that emits light when irradiated by incident electrons. Once emitted, the light can be collected by a phototube where the photons are converted into an electrical charge proportional to the electron’s energy. Incident electrons often penetrate into the material to only a shallow depth before deflecting back towards the source. Scattered out of the scintillator, the electrons may not deposit their full energy into the scintillation, shifting the true spectrum. This phenomenon, known as electron backscattering, has been studied for precise spectroscopy of any electron source. Backscattering electrons depends on incident electron beam energy and intensity, and scattering angle.

In some cases in TEM, for fine focusing, a thinner layer of fluorescent screen should be employed to avoid the backscatter of electrons that occur from the solid substrate.