I am planning to use SEM for my research, and I read that FE-SEM is advantageous to the other SEM types. Can anyone give me a brief difference of the two and elaborate advantages of the FE-SEM. Thank you!
As Vladimir already pointed out there are different FE-SEMs. Using cold emitters you can reach better image resolution but for analytical problems thermal FE-SEMs are the better choice despite the slightly lower resolution. Nevertheless, always take into account that the effective resolution is practically always worse than given in the prospects since the environmental conditions are typically not that perfect as demonstrated in the factory. So don't be surprised if the images finally don't look that fantastic as demonstrated in the prospects or during demonstrations. The selected materials and conditions are exactly chosen in order to impress you :-). AND: the major factor is still the operator and not the SEM. You can have the best SEM but if you don't have a "matching" operator with a lot of experience images or any analyses are always questionable. It is the same if you get a Formel 1 car and expect you will win the next race. I will never understand why well-educated scientists don't get this and believe you only need to press a button...or two...
Difference is only quantitative: better resolution (higher magnifications), better imaging at low voltages.
The field emission gun results in a better coherence of the electron beam as compared to a thermal filament. Thus, the you can operate the instrument with a smaller spot size on your sample, i.e. a better resolution. Resolution of FE-SEM goes down to a few nanometers (but strongly depending on your sample, detector, etc.)
Today "a few nanometers" can describe resolution of thermal SEMs. Best FESEMs can have resolution better than 1 nm.
It would help if we knew what sample type you are interested in studying and what you are trying to achieve by using EM. It might be that you don't need to use FE-SEM. Other replies have stated the main differences.
As Vladimir already pointed out there are different FE-SEMs. Using cold emitters you can reach better image resolution but for analytical problems thermal FE-SEMs are the better choice despite the slightly lower resolution. Nevertheless, always take into account that the effective resolution is practically always worse than given in the prospects since the environmental conditions are typically not that perfect as demonstrated in the factory. So don't be surprised if the images finally don't look that fantastic as demonstrated in the prospects or during demonstrations. The selected materials and conditions are exactly chosen in order to impress you :-). AND: the major factor is still the operator and not the SEM. You can have the best SEM but if you don't have a "matching" operator with a lot of experience images or any analyses are always questionable. It is the same if you get a Formel 1 car and expect you will win the next race. I will never understand why well-educated scientists don't get this and believe you only need to press a button...or two...
Fundamental differences are smaller size of virtual electron source, narrower energy spread and higher coherence of as-extracted electron beam in FE as compared to Thermonic Source SEM. Consequently, FE allows for smaller probe size in imaging regime and higher probe currents for the given probe size in analytical regime.
As many mentioned, real-life performance is heavily dependent on operator :)
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