Difference Between Valence Band And Conduction Band Pdf
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Basic Electronics - Energy Bands
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Band Theory was developed with some help from the knowledge gained during the quantum revolution in science. In , Felix Bloch had the idea to take the quantum theory and apply it to solids. In , Walter Heitler and Fritz London discovered bands- very closely spaced orbitals with not much difference in energy. In this image, orbitals are represented by the black horizontal lines, and they are being filled with an increasing number of electrons as their amount increases. Eventually, as more orbitals are added, the space in between them decreases to hardly anything, and as a result, a band is formed where the orbitals have been filled. Sodium's bands are shown with the rectangles. Filled bands are colored in blue.
Valence and Conduction band are the two different energy levels separated by a certain amount of energy. The main difference between the valence band and conduction band is that valence band specifies the energy level of electrons present in the valence shell of an atomic structure. As against a conduction band holds those electrons that are responsible for conduction. It is basically defined as the energy band that comprises of valence electrons present in the outermost shell of an atomic structure. These valence electrons, when provided with sufficient energy, get changed into free electrons and moves to conduction band thereby causing conductivity. It is sometimes abbreviated as VB and is at a lower energy level than the conduction band in the energy level diagram.
Conductors are generally substances which have the property to pass different types of energy. In the following, the conductivity of electricity is the value of interest. The conductivity of metals is based on the free electrons so-called Fermi gas due to the metal bonding. Already with low energy electrons become sufficiently detached from the atoms and a conductivity is achieved. The conductivity depends, inter alia, on the temperature. If the temperature rises, the metal atoms swing ever stronger, so that the electrons are constrained in their movements.
It causes a certain number of valence electrons to cross the energy gap and jump into the conduction band, leaving an equal amount of unoccupied energy states, i.e. holes. Difference between Intrinsic and Extrinsic Semiconductors.
Valence and conduction bands
Energy bands consisting of a large number of closely spaced energy levels exist in crystalline materials. The bands can be thought of as the collection of the individual energy levels of electrons surrounding each atom. The wavefunctions of the individual electrons, however, overlap with those of electrons confined to neighboring atoms. The Pauli exclusion principle does not allow the electron energy levels to be the same so that one obtains a set of closely spaced energy levels, forming an energy band. The energy band model is crucial to any detailed treatment of semiconductor devices.
The valence band is the band of electron orbitals that electrons can jump out of, moving into the conduction band when excited.
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