Figure 1972a shows the structure of the electron probe-forming system in STEM mode in JEOL JEM-2010F TEMs. A setup, consisting of electrostatic gun lens and twin condenser lens system, controls the de-magnification of the Schottky field emission source.
Figure 1972a. Schematic illustration of the probe-forming electron optics in STEM mode in JEOL JEM-2010F TEMs.
As en example, Figure 1972b shows the schematic illustration of a field-emission source. the “extraction” field is generated by the first anode, which is charged by several kV of extraction voltage with respect to the tip. The second anode is then used to accelerate the electrons into the EM (electron microscope) column. The combination of two anodes operates like an electrostatic lens, producing a “virtual” gun crossover.
Figure 1972b. Schematic illustration of a field-emission source.