Interaction between Electrons and Solids

It is also important to know that the interaction volume of electrons with a solid specimen is much larger than the beam size. According to a Monte Carlo simulation, in which the detailed history of an electron trajectory is calculated in a stepwise manner, the interaction volume is a function of the accelerating voltage and properties of the target specimen. 

There are three main formation mechanisms of TEM image contrast massthickness contrast, diffraction contrast and phase contrast. When electrons pass 

Electron radiation is a wave, which can be characterized by two physical terms amplitude A) and phase (6) Ae. Since electron radiation is coherent, when two waves meet, the resulting wave is a sum of the two waves, Ae = Aje -f A2e , and the resultant intensity is not necessarily bigger than any individual wave intensity but depends on the phase difference of the two waves. A phase-object refers to a specimen so thin that when a coherent plane wave passes through it, only the phase of the wave changes but the amplitude keeps its original value. Thus, there 

The overall resolution in HRTEM is governed partly by the electron wavelength and partly by the optical characteristics of the objective lens. The most important effect of the latter arises from spherical aberration. This aberration introduces a phase difference into the individual diffracted beams and when the real image is synthesized by the lens from these diffracted beams this can give rise to considerable confusion in the image contrast. 

Increasing the focal length by an amount AF causes a non-axial ray to be brought to the optic axis further from the specimen. The phase difference between axial and non-axial rays is  

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