A scanning electron microscope (SEM) is a type of electron microscope that produces images of a sample by scanning it with a focused beam of electrons. The electrons interact with atoms in the sample, producing various signals that can be detected and that contain information about the sample's surface topography and composition. The electron beam is generally scanned in a raster scan pattern and the beam's position is combined with the detected signal to produce an image. The most common SEM mode is the detection of secondary electrons (SE) emitted by atoms excited by the electron beam. The number of detected secondary electrons depends, among other things, on the angle at which the beam impinges the surface of the specimen. This produces a straightforward topographic image of the specimen.
FESEM uses a field emission gun as the electron source. Compared to a conventional SEM, it produces clearer, less electrostatically distorted images, with spatial resolution down to 1 nm.
This Tescan Mira3 instrument was designed for high vacuum (HV) operation and is also rigged with detectors allowing electron back-scattering spectroscopy (EBS) and energy dispersion X-ray spectroscopy (EDX) for chemical element mapping of surfaces with sub-micron resolution.
|AV||Resolution in the High Vacuum Mode|
|SE||In-beam SE (option)||BD mode (option)|
|30 kV||1.2 nm||1.0 nm||–|
|15 kV||1.5 nm||1.2 nm||–|
|3 kV||2.5 nm||2.0 nm||1.5 nm|
|1 kV||4.5 nm||3.5 nm||1.8 nm|
|200 V||–||–||2.5 nm|