Conduction band

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The conduction band quantifies the range of energy required to free an electron from its bond to an atom. Once freed from this bond, the electron becomes a 'delocalized electron', moving freely within the atomic lattice of the material to which the atom belongs. Various materials may be classified by their band gap: this is defined as the difference between the valence and conduction bands.

  • In insulators, the conduction band is much higher in energy than the valence band and it takes large energies to delocalize their valence electrons. Insulating materials have wide band gaps.
  • In semiconductors, the band gap is small. This explains why it takes a little energy (in the form of heat or light) to make semiconductors' electrons delocalize and conduct electricity, hence the name, semiconductor.
  • In metals, the Fermi level is inside at least one band. These Fermi-level-crossing bands may be called conduction band, valence band, or something else depending on circumstance.

Electrons within the conduction band are mobile charge carriers in solids, responsible for conduction of electric currents in metals and other good electrical conductors.

The concept has wide applications in the solid-state physics field of semiconductors and insulators.

Semiconductor band structure (lots of bands 2).svg
Semiconductor band structure
See electrical conduction and semiconductor for a more detailed description of band structure.

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