The conduction band is the range of electron energies enough to free an electron from binding with its atom to move freely within the atomic lattice of the material as a 'delocalised electron'. Various materials may be classified by their band gap: this is defined as the difference between the valence and conduction bands.
- In non-conductors, aka insulators, the conduction band is higher than that of the valence band, so it takes infeasibly high energies to delocalise their valence electrons. They are said to have a non-zero band gap.
- In conductors, such as metals, that have many free electrons under normal circumstances, the conduction band overlaps with the valence band--there is no band gap.
- 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 delocalise and conduct electricity, hence the name, semiconductor.
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
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