The important part here is the FE, the "field emission". If you look at the physics behind it, it requires that both ends are sufficiently conducting so that the band structures of emitter and receiver don't bend additionally - and charging would cause such bending and thus disturb your image.
For that reason, an insulating or at least poorly conducting sample is commonly coated in metal to ensure that and gold, due to its low corrosion affinity, is a common choice.
While conductive coating is a must for conventional SEM, FESEM may (just may) help you to work without coating. FESEM can work with low voltages, like 1 kV. Most materials would not charge when electron beam energy is about 1-1.5 kV (precise value depends on material). You may want to start observation at 1 kV and look for best image while changing accelerating voltage.
You can operate FESEM at a low accelerating voltage (1-2 kV) to avoid the charging effect without coating. However, with the low accelerating voltage, you won't be able to take high-resolution images. If you are focusing on high-resolution images, coating is unavoidable.
Alternatively, you can opt for variable pressure mode, If you don't want to coat your samples.
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