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Electronic band structure - Wikipedia, the free encyclopedia (1390 words) |
 | The uppermost occupied band in an insulator or semiconductor is called the valence band by analogy to the valence electrons of individual atoms. |
| Because one of the main mechanisms for electrons to be excited to the conduction band is due to thermal energy, the conductivity of semiconductors is strongly dependent on the temperature of the material. |
| This band gap is one of the most useful aspects of the band structure, as it strongly influences the electrical and optical properties of the material. |
| Band Theory for Solids (623 words) |
| Instead of having discrete energies as in the case of free atoms, the available energy states form bands. |
| In insulators the electrons in the valence band are separated by a large gap from the conduction band, in conductors like metals the valence band overlaps the conduction band, and in semiconductors there is a small enough gap between the valence and conduction bands that thermal or other excitations can bridge the gap. |
| Most solid substances are insulators, and in terms of the band theory of solids this implies that there is a large forbidden gap between the energies of the valence electrons and the energy at which the electrons can move freely through the material (the conduction band). |
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