What is SEM - scanning electron microscopy ?

What is Scanning Electron Microscopy (SEM)?

Scanning electron microscopy is a type of electron microscopy that produces images by rastering a focused electron beam across the surface of a sample. This technique produces detailed images of a specimen’s surface. Its applications include surface topography and spatially resolved composition using Energy Dispersive Spectroscopy (EDS). SEM produces images with a magnification of 500,000x and a typical resolution power of a few nanometers.


What is the difference between TEM and SEM?

Transmission electron microscopy requires higher electron acceleration voltages and an electron transparent sample, the image is the result of the interaction of the electron as they travel through the sample. Scanning electron microscopy images the surface of the specimen, producing images of the sample surface. TEM has a higher resolution and magnification than SEM.


What are secondary electrons (SE)?

Secondary electrons are low-energy electrons that are ejected from within a few nm of the surface due to the interaction with incident electrons or backscattered electrons.


What are backscattered electrons (BSE)?

A fraction of incident electrons is deflected in the target material through an angle greater than 90°, causing them to emerge from the target surface. This can also result from multiple deflections through smaller angles. The fraction of incident electrons that are backscattered, is strongly dependent on the atomic number of the target material because of the increasing probability of high-angle deflection with increasing atomic number material. Backscattered electrons have energies ranging up to those of the incident electron energy, and the mean of the energy distribution is highest for elements of high atomic number. In contrast, multiple low-angle scattering dominates the backscattering from low atomic number elements, which lose more energy before they emerge from the target surface.


What is cathodoluminescence (CL)?

Under electron bombardment, for some non-metallic materials,  electrons will jump from the valence band to the conduction band. These excited electrons return to their original state and emit the excess energy as photons (light) call CL.