Since only the images obtained by a scanning electron microscope (SEM) and a transmission
electron microscope (TEM) were used in this work and since both techniques are well-
established, only a brief introduction is given on the principles and instrumentation of SEM
and TEM aiming to show what kind of information is expressed through the images
obtained by these techniques.
An image is the optical representation of an object illuminated by a radiation source. The
following elements are present in an image formation process: an object, a radiation source
(visible light, X-rays, electrons, etc.) and an image formation system. The mathematical
model which describes the image formation, depends on the radiation source, on the physics
of the radiation-object interaction and on the acquisition system used. A beam of high energy
electrons is the radiation source in SEM and TEM. When it strikes a sample a number of
phenomena occur simultaneously which is taken form shows different signals generated by
the interaction of an electron beam with a solid. Theelectron interaction volume and the
volume from which the different signals are originating.