ABSTRACT
Electron beams are used for many applications. The most well-known example is probably the old-fashioned cathode ray tube (CRT) television, which changed our daily life. And an important step for science and technology was the invention of the electron microscope. Today’s focused electron beam equipment uses electron beams mainly for imaging purposes, elemental characterization, and writing. With respect to imaging or chemical analysis, electron irradiation of a sample produces a wealth of different signals for detection, each with specific information on the sample, for example:
• elastically back-scattered electrons; • secondary electrons (ejected from the sample by inelastic scattering interactions with the beam electrons); • Auger electrons (a beam electron removes an electron from the core of an atom, leaving a vacancy, an electron from a higher energy level falls into the vacancy, and the energy that is released is transferred to another electron, which is ejected from the atom with a characteristic kinetic energy); • characteristic X-rays (a beam electron removes an electron from the core of an atom, leaving a vacancy, an electron from a higher energy level falls into the vacancy, and the energy that is released is transferred to a photon); • light (a beam electron promotes an electron from the valence band to the conduction band (semiconductor sample), leaving a hole, and the electron recombines with a hole and emits a photon); and • whether the sample is thin enough: transmitted electrons, which can be analyzed on changes in amplitude, phase, and/or energy with respect to the primary beam.
