Êtes-vous un étudiant de l'EPFL à la recherche d'un projet de semestre?
Travaillez avec nous sur des projets en science des données et en visualisation, et déployez votre projet sous forme d'application sur GraphSearch.
Concept
Valence and conduction bands
Résumé
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. On a graph of the electronic band structure of a semiconducting material, the valence band is located below the Fermi level, while the conduction band is located above it.
The distinction between the valence and conduction bands is meaningless in metals, because conduction occurs in one or more partially filled bands that take on the properties of both the valence and conduction bands.
Band gap
In semiconductors and insulators the two bands are separated by a band gap, while in conductors the bands overlap. A band gap is an energy range in a solid where no electron states can exist due to the quantization of energy. Within the concept of bands, the energy gap between the valence band and the conduction band is the band gap. Electrical conductivity of non-metals is determined by the susceptibility of electrons to be excited from the valence band to the conduction band.
Semiconductor band structureSee electrical conduction and semiconductor for a more detailed description of band structure.
In solids, the ability of electrons to act as charge carriers depends on the availability of vacant electronic states. This allows the electrons to increase their energy (i.e., accelerate) when an electric field is applied. Similarly, holes (empty states) in the almost filled valence band also allow for conductivity.
As such, the electrical conductivity of a solid depends on its capability to flow electrons from the valence to the conduction band. Hence, in the case of a semimetal with an overlap region, the electrical conductivity is high. If there is a small band gap (Eg), then the flow of electrons from valence to conduction band is possible only if an external energy (thermal, etc.
Source officielle
À propos de ce résultat
Cette page est générée automatiquement et peut contenir des informations qui ne sont pas correctes, complètes, à jour ou pertinentes par rapport à votre recherche. Il en va de même pour toutes les autres pages de ce site. Veillez à vérifier les informations auprès des sources officielles de l'EPFL.
Publications associées (6)
From hidden order to antiferromagnetism: Electronic structure changes in Fe-doped URu2Si2
Emmanouil Frantzeskakis, Ji Dai, Kevin Huang
In matter, any spontaneous symmetry breaking induces a phase transition characterized by an order parameter, such as the magnetization vector in ferromagnets, or a macroscopic many electron wave funct
NATL ACAD SCIENCES2021Charge-carrier Dynamics in Metal Oxides and Hybrid Lead Perovskites investigated by Time-Resolved UV and X-ray Spectroscopy
In modern ultrafast optoelectronic technologies based on wide band gap insulators, the non-equilibrium dynamics of photogenerated charges plays a major role. Unravelling the mechanisms of interaction
EPFL2018Oxygen DX center in In0.17Al0.83N: Nonradiative recombination and persistent photoconductivity
Alfredo Pasquarello, Giacomo Francesco Leonardo Miceli, Rocco Meli
Using a hybrid density-functional scheme, we address the O impurity substitutional to N (O-N) in In0.17Al0.83N. Our modelling supports In clustering to account for the strong band-gap bowing observed
American Institute of Physics2017Personnes associées (23)
Unités associées (2)
Concepts associés (27)
Théorie des bandes
redresse=1.5|vignette|Représentation schématique des bandes d'énergie d'un solide. représente le niveau de Fermi. thumb|upright=1.5|Animation sur le point de vue quantique sur les métaux et isolants liée à la théorie des bandes En physique de l'état solide, la théorie des bandes est une modélisation des valeurs d'énergie que peuvent prendre les électrons d'un solide à l'intérieur de celui-ci. De façon générale, ces électrons n'ont la possibilité de prendre que des valeurs d'énergie comprises dans certains intervalles, lesquels sont séparés par des bandes d'énergie interdites (ou bandes interdites).
Physique du solide
La physique du solide est l'étude des propriétés fondamentales des matériaux solides, cristallins – par exemple la plupart des métaux –, ou amorphes – par exemple les verres – en partant autant que possible des propriétés à l'échelle atomique (par exemple la fonction d'onde électronique) pour remonter aux propriétés à l'échelle macroscopique. Bien que celles-ci présentent parfois de fortes réminiscences des propriétés microscopiques (par ex.
Valence and conduction bands
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. On a graph of the electronic band structure of a semiconducting material, the valence band is located below the Fermi level, while the conduction band is located above it.
Cours associés (40)
EE-567: Semiconductor devices II
Students will learn about understanding the fundamentals and applications of emerging nanoscale devices, materials and concepts.
Remark: at least 5 students should be enrolled for the course to be g
MICRO-505: Organic and printed electronics
This course addresses the implementation of organic and printed electronics technologies using large area manufacturing techniques. It will provide knowledge on materials, printing techniques, devices
MSE-484: Properties of semiconductors and related nanostructures
This course explains the origin of optical and electrical properties of semiconductors. The course elaborates how they change when the semiconductors are reduced to sizes of few nanometers. The course
MOOCs associés (4)
Electronique II
Introduction à l’électronique analogique- seconde partie. Fonctions linéaires de base réalisée à l’aide de transistor bipolaire.
Electronique II
Introduction à l’électronique analogique- seconde partie. Fonctions linéaires de base réalisée à l’aide de transistor bipolaire.
Synchrotrons and X-Ray Free Electron Lasers (part 1)
Synchrotrons and X-Ray Free Electron Lasers (part 1)