Comparative study of electron beam-gas interaction in an SEM operating at pressures up to 300 Pa

The effects of three different gas environments formed by pure argon, helium and nitrogen with variable pressures up to 300 Pa inside the specimen chamber of a scanning electron microscope on the electron beam parameters were investigated and compared using Monte Carlo calculations. The calculations show that the skirt of the electron beam probe is nearly independent of pressure in the case of helium, which is also supported by experimental evidence. Both theoretical simulation and experimental facts indicate helium as the environment of choice in specimen chambers for minimizing the effect of beam-gas interactions.