valence band


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Valence band

The highest electronic energy band in a semiconductor or insulator which can be filled with electrons. The electrons in the valence band correspond to the valence electrons of the constituent atoms. In a semiconductor or insulator, at sufficiently low temperatures, the valence band is completely filled and the conduction band is empty of electrons. Some of the high energy levels in the valence band may become vacant as a result of thermal excitation of electrons to higher energy bands or as a result of the presence of impurities. The net effect of the valence band is then equivalent to that of a few particles which are equal in number and similar in motion to the missing electrons but each of which carries a positive electronic charge. These “particles” are referred to as holes. See Band theory of solids, Conduction band, Electric insulator, Hole states in solids, Semiconductor

McGraw-Hill Concise Encyclopedia of Physics. © 2002 by The McGraw-Hill Companies, Inc.

valence band

[′vā·ləns ‚band]
(solid-state physics)
The highest electronic energy band in a semiconductor or insulator which can be filled with electrons.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
References in periodicals archive ?
The valence band moves to higher energy regions in GaN:[V.sub.Ga].
shows that, in TiO2 valence band holes oxidize water and conduction band electrons cannot reduce CO2 to CO2-[9].
The valence band offset for InBi is found out to be 0.35 eV from Figure 1 (drawn by using the data from [9]) corresponding to its lattice constant of 6.686 [Angstrom] [12].
When the ZnO NWs are irradiated by UV-radiation, the electron-hole pairs were produced generated by excitation of the electron from valence band to conduction band in ZnO NWs.
In another catalyst application, Lehigh researchers Kamil Dlier and Shaoli Hou are using the ESCA 300 to investigate the valence band spectra of sodium-type A-Zeolite catalysts being prepared by ion exchange replacement of sodium with cobalt.
This optical band is known as yellow-green band and is related to crystalline defects like vacancies and interstitial sites which nature is still an interesting and controversial topic in the literature despite emission at 2.5 eV that is attributed to the recombination from oxygen vacancy levels to the valence band [20].
The graphical band structures in Figure 5 as well as the numerical data in Table 10, which lists energy values of the highest valence band and the lowest conduction band at selected high-symmetry k points, confirm that in all phases there are states elsewhere in the Brillouin zone which are nearly degenerate with the valence-band maximum or the conduction-band minimum.
These devices showed a zone for low current densities (0-8 mA) which did not show EL emission; this denies the direct excitation of luminescence centers by accelerated carriers as the principal excitation mechanism of the EL, suggesting that the localized electron-hole pairs were responsible for the emission which was created by trapping an electron and hole from the conduction and the valence band, respectively [22].
The distance between the highest point of the Fermi energy level valence band (EV) and the lowest point of the conduction band (Ec) can be used to determine the energy required for valence electrons to move to the conduction band, which is also known as the forbidden band or the band gap.
Additional evidence of p-type Ti[O.sub.2] is from XPS spectra of the valence band region.