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The electron affinity of molecules is a complicated function of their electronic structure. For instance the electron affinity for benzene is negative, as is that of naphthalene, while those of anthracene, phenanthrene and pyrene are positive. In silico experiments show that the electron affinity of hexacyanobenzene surpasses that of fullerene. [5]
Electron affinity can be defined in two equivalent ways. First, as the energy that is released by adding an electron to an isolated gaseous atom. The second (reverse) definition is that electron affinity is the energy required to remove an electron from a singly charged gaseous negative ion.
Electrons emitted in this manner are called photoelectrons. The phenomenon is studied in condensed matter physics, solid state, and quantum chemistry to draw inferences about the properties of atoms, molecules and solids. The effect has found use in electronic devices specialized for light detection and precisely timed electron emission.
This spacing is called the electron affinity (note that this has a different meaning than the electron affinity of chemistry); in silicon for example the electron affinity is 4.05 eV. [16] If the electron affinity E EA and the surface's band-referenced Fermi level E F-E C are known, then the work function is given by
The electron affinity (usually given by the symbol in solid state physics) gives the energy difference between the lower edge of the conduction band and the vacuum level of the semiconductor. The band gap (usually given the symbol E g {\displaystyle E_{\rm {g}}} ) gives the energy difference between the lower edge of the conduction band and the ...
One component is the difference in the work function (also called the electron affinity) between the two materials. [48] This can lead to charge transfer as, for instance, analyzed by Harper. [ 49 ] [ 50 ] As has been known since at least 1953, [ 37 ] [ 51 ] [ 52 ] [ 53 ] the contact potential is part of the process but does not explain many ...
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In operation the photocathode requires an electric field with a nearby positive anode to assure electron emission. Molecular beam epitaxy is broadly applied in today's manufacturing of photocathode. By using a substrate with matched lattice parameters, crystalline photocathodes can be made and electron beams can come out from the same position ...