The beauty of FE SEM is that it can work with pretty low accelerating voltages on specimens with no coating at all. In that case you need to use 0.5-1.5 kV, looking for sweet spot for each combination of specimen composition/topography.

For most coated specimens 5 kV works fine (for as long as you do not use BSE or EDS), but it can be lower, depending on personal preferences.

Au coating is not the best for FE SEM, capable of high magnification. Au-Pd or Pt are much better, but event these coatings became visible at magnification above x50,000-x100,000; special coatings are recommended for higher magnification.

Voltage for the best resolution (highest magnification) depends on make of your SEM and on specimen and should be chosen during observation along with right working distance and beam current.

The beauty of FE SEM is that it can work with pretty low accelerating voltages on specimens with no coating at all. In that case you need to use 0.5-1.5 kV, looking for sweet spot for each combination of specimen composition/topography.

For most coated specimens 5 kV works fine (for as long as you do not use BSE or EDS), but it can be lower, depending on personal preferences.

Au coating is not the best for FE SEM, capable of high magnification. Au-Pd or Pt are much better, but event these coatings became visible at magnification above x50,000-x100,000; special coatings are recommended for higher magnification.

Voltage for the best resolution (highest magnification) depends on make of your SEM and on specimen and should be chosen during observation along with right working distance and beam current.

@Vladimir Dusevich Thank you for your reply sir, I will surely try to change the coating material and see the result.

It really depends on what sample you want to image and what your goal is.

For higher magnification/resolution you would need to turn up the energy of the beam. If you want more surface sensitivity, I'd keep the beam below 5 keV.

As Vladimir said, if your sample is charging but you do not want to cover it in a metal, you can still probably get decent images at

Polymers,biomaterials ,fine and nanofibers in general not need high accelerated voltage in SEM test,but you can work with low working distance in SEM , while metals ,ceramic and other ( hard materials) can stand with high voltage.

its depend upon details of the sample materials

Generally speaking, the only time there is a specific value for acceleration is when you're working with un-coated samples and need charge balance, which will be highly material dependent. This can also be figured out in an ad-hoc manner by adjusting acceleration and comparing brightness/distortion.

As for your coated samples there is always a trade-off. Higher acceleration gives a lower beam diameter, but a larger interaction volume. The best parameter will greatly depend on the topography and resolution needed.

Another parameter is consider is always working distance. Closer gives finer focus, but worse depth of focus. So if you have a tall topography you're wanting to capture, you might want your sample farther away from the objective lens.