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Glossary terms about Backscattered Electrons

Backscattered Electrons (BSE)
Produced through an elastic scattering interaction with the atoms in the sample that results in the primary electron being re-emitted from the specimen. The electron is said to have backscattered (or reflected back) from the sample. In backscattering, the electron trajectory is changed by more than 90 deg from the forward direction of motion. This results in the scattered electron propagating back in the general direction of the original beam. Note that between the multiple elastic events (that form Backscattered electrons), the beam electrons may also be involved in inelastic events, and thus reduce the electron's energy. Backscattered electrons usually have energy in the kV range.


13 pages mention Backscattered Electrons

Acceleration voltage vs. specimen type
So there will be a brigher image because the number of backscattered electrons (BSEs) will increase but the resolution will be worse. 
Applications and practical uses - what the SEM can do
view bulk material, coatings, sectioned material, foils, even grids prepared for transmission electron microscopy). Image compositional and some bonding differences (through contrast and using backscattered electrons). 
Conventional (high vacuum) scanning electron microscopy (SEM)
This type of machine is used for routine imaging, using either secondary electrons (SE) or backscattered electrons (BSE). 
Cryo-scanning electron microscope (Cryo-SEM)
It is imaged using either secondary electrons (SE) or backscattered electrons (BSE). 
Detectors
As the specimen surface is scanned by the incident electron beam, backscattered electrons (BSE) are generated, the yield of which is controlled by the topographical, physical and chemical characteristics of the sample. 
Electron column
As the beam is scanned over the specimen in the X- and Y- directions, secondary and backscattered electrons are produced and detected. 
Electron-matter interactions
Some electrons are bounced back out of the sample (backscattered electrons), others knock into atoms and displace electrons that, in turn, come out of the sample (secondary electrons); alternatively X-rays, and light or heat (in the sample) can be the result of these interactions. 
Generating an image
In the image, the left picture is taken using backscattered electrons
High vacuum mode and pump system
Because backscattered electrons and characteristic X-rays are generally of higher energy than secondary electrons, their detection is not critically dependant on a high vacuum being maintained in the specimen chamber. 
Images from electrons
Image from secondary electrons: high-resolution (InLens SE detector) Gold nanoparticles. (Topographical and morphological information.) Image from backscattered electrons Mineral sand: lighter grains have higher average atomic number. 
SEM challenge
What type of electrons are causing this effect? Note: SE1 are a type of secondary electron generated by the primary beam whereas SE2 are generated by backscattered electrons
Troubleshooting: edge effect, charging, sample damage
The solution therefore, for obtaining fine surface structure is to exclude these backscattered electrons by using lower kVs such as 3-10kV. 
Variable Pressure or Low Vacuum scanning electron microscopy (LVSEM)
Imaging uses backscattered electrons (BSE).