The band gap is the energy difference between the valence band and the conduction band. The dark shading represents electrons in the band. Insulators have a large band gap, and metals have a small band gap. Semiconductors are the intermediate case.

Applying a voltage to a metal tips the bands, resulting in a flow of electrons.

When electrons from the conduction band recombine with holes from the valence band, the energy released is in the form of light.

Exploring the Nanoworld   |   MRSEC Nanostructured Interfaces
Copyright © 2008 The Board of Regents of the University of Wisconsin System.

This page created by George Lisensky, Beloit College.  Last modified July 25, 2008 .