Electron microscopy
 
Coherence in EM Measurements
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Table 1218. Coherency of scattered electrons from a specimen in EM (electron microscope) measurements.

Coherency
Property
Coherent In phase: preserves the relative phases of the wavelets scattered from different locations in a material; namely, well-defined phase relationship between incident and scattered radiation
Fixed wavelength
The resolution for coherent imaging is much worse than that for incoherent imaging
Useful for diffraction experiments
Incoherent No phase relationship: does not preserve a phase relationship between the incident wave and the scattered wavelets
Not useful for diffraction experiments
The spatial distribution of the scattered intensity is obtained by summing up the intensities from independent scattering events
Incoherent elastic scattering follows the Rutherford scattering law
The resolution for incoherent imaging is much greater than that for coherent imaging due to squaring an amplitude distribution
Incoherent cases: e.g. difference in wavelength
More coherent beam Sharper diffraction pattern can be obtained
* When the electrons are treated as waves, their coherency becomes important.

 

 

 

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