How are the secondary electrons detected?
Electrons from the electron beam impact and unbind outer-shell electrons from atoms in the sample. These outer-shell electrons are called the secondary electrons. These electrons hit a detector called a scintillator-multiplier device. the scintillator portion of the device absorbs the secondary electron and fluoresces photons. The photomultiplier portion of the device absorbs the photon and converts it into a largely amplified electrical signal. The intensity of this signal is proportional to the brightness seen on the screen. The detector is mounted at an angle to the sample and electron beam, this creates the shadowing effect seen in the images.
