Output

In Physical, in Mechanical quantum, the output is the minimum energy, measured in electronvolt S, necessary to tear off a electron since the level of Fermi of a Métal up to a point located ad infinitum in-outside metal.

The output is roughly half of the energy of ionization of a free atom of the same metal.

Photoelectric output

The photoelectric Effet consists of a release of an electron when a Photon equipped with an energy higher than the output arrives on metal. The difference between energy of the incidental photon and the output is provided to the kinetic electron in the form of energy.

Photoelectric output east:

\ varphi = h.f_0 \,

where H is the Constante of Planck and f0 is the Fréquence minimum photon from which the photoelectric emission occurs.

Thermionic output

The output is also an important concept in the theory of the emission Thermoïonique. In this case, the energy imparted to the electron comes from a heat exchange instead of an interaction with a photon.

Let us take the example of an electron extracted from a filament heated and carried to a negative potential in a Vacuum tube. One then calls sometimes the output “thermionic output”. The Tungstène is a metal very very employed in the technology of the vacuum tubes because of its weak output of about 4,5 eV roughly.

The output depends on the orientation of the crystal. It will be generally weaker for metals whose crystal lattice is open and higher for metals in which the atoms are assembled in way compacts. The practical values of the output are generally in the range 1,5-6 V. They can be higher for the very dense crystals.

Example

For example, the Césium has a energy of ionization of 3,9 eV and an output of 1,9 eV.

W = - E_ {early} (N+1) + \ {E_ {early} (NR) + V (\ infty) \} = - {\ partial E_ {early} \ over {\ partial NR}} + V (\ infty) = - \ driven + V (\ infty)

E_ {early} (N+1) - E_ {early} (NR) = {\ partial E_ {early} \ over {\ partial NR}} = \ driven

\ varepsilon_F = \, \ driven

where V is the energy Niveau Vide and F the Niveau of Fermi.

Applications

In electronic the output is an important size for the design of the junctions Métal - Semi-conducteur of the diodes Schottky and in the design of the electron tubes.

See too

External bonds

  • the structure Metal-Semiconductor - Effects of surface on the site of the University Polytechnic school of Lille;
  • Physics solid state: energy bands;
  • Output of current metals;
  • Output material used for the photoelectric effect;
  • Output of some metals with the temperature necessary to release the electrons by Thermionic emission ;
  • Some output.

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