electron microscopy
 

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RESEARCH: RECENT HIGHLIGHTSEXAMPLES


 

Inelastic Interactions of Electrons with Matter

Ionization

The high-energy electrons of the incident beam can transfer a critical amount of energy to an inner-shell electron of an atom, leading to the ejection of this electron. The ionization energy is provided by the incident electron, reducing its energy. This leads to an ionization edge in the electron energy loss spectrum (EELS). Subsequently, the hole in the inner-shell is filled up by an electron with higher energy from an outer shell. This electron gives away a part of its energy, leading to the emission of characteristic X-rays or Auger electrons.

Secondary electrons

Electrons in the conduction or valence band do not need much energy (low work function) to be transferred into vacuum. Thus, the energy of secondary electrons (SE) is low (>50 eV). The SEs are mainly exploited in SEM.

Phonons

Phonons are lattice vibrations, which are equal to heating the specimen. This effect may lead to a damage of the sample.

Plasmons

Plasmons are longitudinal oscillations of free electrons, which decay either in photons or phonons.

Cathodoluminescence

If semiconductors are hit by high-energy electrons, electron-hole pairs can be formed by promoting an valence electron into the conduction band. Filling this hole with an electron from the conduction band (recombination) leads to the emission of light with a frequency that corresponds to the band gap.

 

Electron-matter interactions
     
ETH Zürich | ETH chemistry department | ETH inorganic chemistry

modified: 6 February, 2015 by F. Krumeich | © ETH Zürich and the authors