"Resolution improvement of low-voltage scanning electron microscope by bright and monochromatic electron gun using negative electron affinity photocathode"
https://aip.scitation.org/doi/10.1063/10.0001201
"Resolution improvement of low-voltage scanning electron microscope by bright and monochromatic electron gun using negative electron affinity photocathode"
https://aip.scitation.org/doi/10.1063/10.0001201