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Electronic transmission microscopy

The transmission electron microscope (TEM) is an instrument that takes advantage of physical-atomic phenomena that occur when a sufficiently accelerated electron beam collides with a conveniently prepared thin sample. When the electrons collide with the sample, depending on their thickness and the type of atoms that form it, part of them are selectively dispersed, that is, there is a gradation between the electrons that cross it directly and those that are totally deviated. All of them are driven and modulated by lenses to form a final image on a CCD that can have thousands of magnifications with an unreachable definition for any other instrument. The information obtained is an image with different intensities of gray that correspond to the degree of dispersion of the incident electrons.

The TEM image as described provides information on the structure of the sample, whether it is amorphous or crystalline.

In addition, if the sample is crystalline, that is, there is a periodic plane structure, it can happen that several families of these planes meet the Bragg condition and coherently diffract the incident electronic wave. This gives rise to a diffraction diagram, which is an image of different ordered points with respect to a central point (electrons transmitted not deviated) that give us information about the orientation and structure of the crystals present.
Francisco Javier García García
Adrián Gómez Herrero
Esteban Urones Garrote
María Luisa García Gil
Miriam González García
ICTS Microscopy