6. Microanalysis in "controlled pressure" mode or in an environmental chamber

Scanning electron microscopes with controlled pressure and environmental chambers are undergoing significant development. Derived from the work of Danilatos, they feature a high pressure in the sample chamber, thanks to a differential vacuum with the column, which can reach several hundred Pa. This makes it possible to observe hydrated, fragile or insulating samples, due to the interactions of the primary and secondary electron beams with the residual gas in the chamber. On the other hand, these interactions cause skirting of the primary electron beam, which greatly affects the spatial resolution of the analysis [25] .

This distribution depends on several factors:

• gas pressure (figure