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In solid-state physics, the valence band and conduction band are the bands closest to the Fermi level, and thus determine the electrical conductivity of the solid. In nonmetals, the valence band is the highest range of electron energies in which electrons are normally present at absolute zero temperature, while the conduction band is the lowest range of vacant electronic states.
The name "valence band" was coined by analogy to chemistry, since in semiconductors (and insulators) the valence band is built out of the valence orbitals. In a metal or semimetal, the Fermi level is inside of one or more allowed bands. In semimetals the bands are usually referred to as "conduction band" or "valence band" depending on whether ...
Band diagram for semiconductor heterojunction at equilibrium. In solid-state physics of semiconductors, a band diagram is a diagram plotting various key electron energy levels (Fermi level and nearby energy band edges) as a function of some spatial dimension, which is often denoted x. [1] These diagrams help to explain the operation of many ...
In some materials, for example, in graphene and zigzag graphene quantum dot, there exists the energy states having energy eigenvalues exactly equal to zero (E=0) besides the conduction and valence bands. These states are called edge states which modifies the electronic and optical properties of the materials significantly. [3][4][5][6]
Electronic properties of graphene. Sigma and pi bonds in graphene. Sigma bonds result from an overlap of sp 2 hybrid orbitals, whereas pi bonds emerge from tunneling between the protruding p z orbitals. For clarity, only one p z orbital is shown with its three nearest neighbors. Graphene is a semimetal whose conduction and valence bands meet at ...
Direct and indirect band gaps. In semiconductor physics, the band gap of a semiconductor can be of two basic types, a direct band gap or an indirect band gap. The minimal-energy state in the conduction band and the maximal-energy state in the valence band are each characterized by a certain crystal momentum (k-vector) in the Brillouin zone.
In solid-state physics and solid-state chemistry, a band gap, also called a bandgap or energy gap, is an energy range in a solid where no electronic states exist. In graphs of the electronic band structure of solids, the band gap refers to the energy difference (often expressed in electronvolts) between the top of the valence band and the ...
Dangling bond. A schematic illustration of dangling bonds in amorphous silicon. The dangling bonds are depicted as blue-red hybrid sp 3 orbitals. In chemistry, a dangling bond is an unsatisfied valence on an immobilized atom. An atom with a dangling bond is also referred to as an immobilized free radical or an immobilized radical, a reference ...