They develop due to inelastic primary electron (PE) distribution and are present immediately at the surface area of the impacting primary electron beam. They have an energy value of
Electron probe micro analysis
Energy dispersive x-ray spectrometry
Scanning electron microscopy
Wave-length dispersive x-ray spectrometry
Schröttner H. : Die Elektronenmikroskopie in der Materialforschung / Electron Microscopy in Materials Research.