It is known that in Transmission electron microscope, the electrons are diffuse through films less than 300 nm. However, Scanning electron microscope coupled with Electron diffraction X-ray analysis, it is not diffused through the sample. So we can get only the surface elemental composition. Why is it so. Is the energy of electrons are not sufficient to pass through the thick samples.
Electrons being charged particles can not penetrate deep into the solid and therefore gives information of surface only when electron diffraction is used. Due to the same reason they can be transmitted through very thin films only as you have mentioned in your question itself.
Let us compare the size of the electron and the thickness of the film.
It is the possibility of finding electron wave on the other side.
Are they comparable or of the same order?
It is the Schrodinger equation tells us the condition of electron tunneling,
it is tunneling and not crossing over the activation energy barrier. it is the applied voltage gives energy for electrons to tunnel
There are some very useful books. They can help you to compose questions in a better way.
i also written in my book on nano science and technology but not at length
First of all, it strongly depends on the electron energy - electrons of say 100 eV kinetic enrgy have a very short mean free path in condensed matter (in the order of some few nm) and will therefore not be able to penetrate through a thin film of severall 100 nm. As the kinetic energy increases, the mean free path will also increase, and for electrons of say 10 keV energy, the penetration depth may be of the order of 1000 nm depending of the investigated material. For even higher energies, the penetration may further increase!
As Vladimir mentioned above, I strongly recomment to consider textbooks of electron microscopy, transmission electron microscopy, or surface analysis with electrons!
All the best, Dirk
As Dirk correctly remarked, please see the universal curve of the Inelastic mean free path of electron in solids (Tanuma-Powell-Penn):
http://xdb.lbl.gov/Section3/Sec_3-2.html.
And as the other colleages suggest, study more the books.
You are right. Thick samples cannto be penetrated by electrons. In SEM, the X-ray detector is placed above the sample, so that the electron donot ned to penetrate the sample and its excited X-ray signal can be reflected back to the detector. In TEM, we want to see the strucure ratheer than elemental information, so it is required for the beam to penetrate thin sample.
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