If we use a high energy beam (say 30 KeV instead of 10KeV) how will the SEM image be affected by the change ?
Increasing voltage may give charge effect, less surface details and sample damage, and it will also depend on the type of sample you are observing.
If it is metal sample, higher voltage will give better sharpness and resolution.
If it is biological sample, lower voltage will give better surface details.
Instead of increasing the voltage to get better resolution, you may also reduce the probe current or the probe diameter, tilt your specimen (edge effect), reduce the working distance (but reduce the depth of field), or reduce the objective aperture size (increase the depth of field in this case).
Increasing voltage may give charge effect, less surface details and sample damage, and it will also depend on the type of sample you are observing.
If it is metal sample, higher voltage will give better sharpness and resolution.
If it is biological sample, lower voltage will give better surface details.
Instead of increasing the voltage to get better resolution, you may also reduce the probe current or the probe diameter, tilt your specimen (edge effect), reduce the working distance (but reduce the depth of field), or reduce the objective aperture size (increase the depth of field in this case).
Usually image quality suffers significantly at high accelerating voltages. Pronounced edge effect makes almost impossible to choose acceptable level of contrast. Fine specimen features can became transparent/invisible.
As for resolution, it depends on specimen. Yes, beam focusing (means resolution for SEM manufacturers) can be done better at higher voltages. For some specimens, such as gold particles of special test specimens, you will definitely see resolution improvement at 30 kV. But for other specimens increase in volume of interaction (electron/matter) may offset gains in beam focusing and resulting resolution can decrease. For such specimens we need to find optimal voltage for highest resolution.
And it depends on an SEM also. Some old or abused microscopes will give better resolution only with increased voltage, but it will be poor resolution anyway.
Another way to increase resolution is to decrease beam intensity. Result - better beam focusing at the same volume of interaction. Drawback - worse signal/ noise ratio, longer scan times can be needed, quality of live observation may suffer.
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