12 Differences between Scanning Electron Microscope and Transmission Electron Microscope (SEM vs TEM)

There are two categories of microscopes based on the principle on which magnification is achieved, Light microscopes and Electron microscopes (EM). In Light or optical microscopes, magnification is obtained by a system of optical lenses using light waves. Electron microscope (EM) uses beams of electrons to produce images. In overall design, EM is similar to light microscopes with some differences (Refer: Electron Microscope  vs Light Microscope)

Electron microscope was designed by Knoll and Ruska of Germany in 1932. There are two types of electron microscopes: TEM (Transmission Electron Microscope) and SEM (Scanning Electron Microscope) 

 Scanning Electron Microscope (SEM) vs Transmission Electron Microscope (TEM)

Scanning Electron Microscope (SEM)	Transmission Electron Microscope (TEM)
Used to produce excellent images of the surfaces of cells and small organisms. Excellent for studying surface morphology of the organisms, cells or any suitable material under study	Used to study the ultra structure of the cell and its components. It can see objects as small as a protein molecule or even at nano level. Provides details about internal composition of cells or any suitable material under study
Electron beam scans over the surface of the sample	Electron beam pass through the sample
Based on scattered electrons or produces images by detecting secondary electrons which are emitted from the surface due to excitation by the primary electron beam	Based on transmitted electrons or produces images by detecting primary electrons transmitted from the sample
Comparatively low resolution than TEM; Resolution: 2nm(Average), 0.2nm (Special)	High Resolution; Resolution: 10 nm (Average), 0.5nm (Special)
Depth of field: High	Depth of field: Moderate
Magnifying power: 100,000X	Magnifying power: 5,000,000X
Specimen contrast:  by electron adsorption	By electron scattering
Produces three-dimensional black and white images	Produces two-dimensional black and white images
Preparation technique: easy	Skilled, very thin sample is required
Preparation thickness: variable	Very thin
Specimen mounting: Aluminium stubs	Thin films on copper grids
Field of view:  Large	Limited
Similarities between SEM and TEM
·         Type of object : Non living
·         Source of radiation: Electron
·         Medium: High vacuum
·         Nature of lenses: one electrostsastic and a few electromagnetic lenses
·         Magnification Adjustment: Current in the projector lens coil
·         Focusing: Current in the objective lens coil
Image credit:1) http://remf.dartmouth.edu/imagesindex.html  2) https://www.paldat.org/pub/Tilia_platyphyllos/109978

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