Electron diffraction refers to the wave nature of electrons. However,
from a technical or practical point of view, it may be regarded as a
technique used to study matter by firing electrons at a sample and
observing the resulting interference pattern. This phenomenon is
commonly known as the wave-particle duality, which states that the
behavior of a particle of matter (in this case the incident electron)
can be described by a wave. For this reason, an electron can be regarded
as a wave much like sound or water waves. This technique is similar to
X-ray and neutron diffraction.
Electron diffraction is most frequently used in solid state physics and chemistry to study the crystal structure of solids. Experiments are usually performed in a transmission electron microscope (TEM), or a scanning electron microscope (SEM) as electron backscatter diffraction. In these instruments, electrons are accelerated by an electrostatic potential in order to gain the desired energy and determine their wavelength before they interact with the sample to be studied.
Most electron diffraction is performed with high energy electrons whose wavelengths are orders of magnitude smaller than the interplanar spacings in most crystals. For example, for 100 keV electrons l < 3.7 x 10-12 m. Typical lattice parameters for crystals are around 0.3 nm.
Electrons are charged, light particles and their penetration into solids is very limited.LEED and RHEED are therefore considered to be surface science techniques, while transmission electron diffraction is limited to specimens less than 1 mm thick. Transmission electron diffraction is usually carried out in a transmission electron microscope (TEM).
Features of electron diffraction
There are three particularly important features of diffraction using high energy electrons:
(1) Since l is very small, Bragg angles are also small, so the Bragg Law can be simplified to:
l = 2dqB
(2) The diameter of the Ewald sphere is very large compared to the size of the unit cell in the reciprocal lattice.
(3) Lenses are able to focus the diffraction pattern and to change the camera length, which is equivalent to moving the film in an x-ray experiment.
Electron diffraction is most frequently used in solid state physics and chemistry to study the crystal structure of solids. Experiments are usually performed in a transmission electron microscope (TEM), or a scanning electron microscope (SEM) as electron backscatter diffraction. In these instruments, electrons are accelerated by an electrostatic potential in order to gain the desired energy and determine their wavelength before they interact with the sample to be studied.
Most electron diffraction is performed with high energy electrons whose wavelengths are orders of magnitude smaller than the interplanar spacings in most crystals. For example, for 100 keV electrons l < 3.7 x 10-12 m. Typical lattice parameters for crystals are around 0.3 nm.
Electrons are charged, light particles and their penetration into solids is very limited.LEED and RHEED are therefore considered to be surface science techniques, while transmission electron diffraction is limited to specimens less than 1 mm thick. Transmission electron diffraction is usually carried out in a transmission electron microscope (TEM).
Features of electron diffraction
There are three particularly important features of diffraction using high energy electrons:
(1) Since l is very small, Bragg angles are also small, so the Bragg Law can be simplified to:
l = 2dqB
(2) The diameter of the Ewald sphere is very large compared to the size of the unit cell in the reciprocal lattice.
(3) Lenses are able to focus the diffraction pattern and to change the camera length, which is equivalent to moving the film in an x-ray experiment.
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