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Why effective mass of electron is negative at the top of valence band?
Wiki User
∙ 13y ago
Because of holes
Wiki User
∙ 13y ago
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Electrons that are held most loosely in an atom are called what?
The electrons in the valence band, this can be 1 to 8 electrons (in the s and p orbitals of the outer shell) depending on the element.
What type of elements form negative ions?
Elements with nearly full valence band orbitals. These elements are on the right side of the periodic table.
Which electrons are responsible for current in a material?
The conduction band electrons. These are valence electrons that become delocalized in conductors and form an "electron gas" that fills the bulk of the conductor and can flow as a fluid in response to electric fields applied across the conductor.
What makes silicon a semiconductor?
Elements have two bands. One is Valence band and other is Conduction band. Valence band contains electrons whereas the conduction band is empty. The energy gap between them is called the forbidden gap. In case of metals, this gap is very small or the bands overlap. Therefore, the electrons are able to jump from the valence band to the conduction band and hence metal are able to conduct electricity and they are generally conductors. In case of Non-Metals, the energy gap is very large and hence hence electrons are not able to move from valence band to conduction band. Hence they are insulators. But in case of elements like Silicon, Germanium this gap is between Metals and Non-Metals, hence few electrons are able to move from valence band to conduction band. Therefore they have some conductivity but it is low and hence they are called semiconductors.
What is uses of organic semiconductor materials?
semiconductor materials are crystals created by atomic bonds through which the valence band of the atoms are ¯lled with 8 electrons through sharing of an electron from each of four nearest neighbor atoms. These materials include semiconductors composed of a single atomic species, with the basic atom having four electrons in its valence band (supplemented by covalent bonds to four neighboring atoms to complete the valence band). These elemental semiconductors therefore use atoms from group IV of the atomic chart. Other semiconductor materials are composed of two atoms, one from group N (N < 4) and the other from group M (M >4) with N + M = 8, ¯lling the valence bands with 8 electrons.
Why are Monovalent metal so conductive?
The single valence band electron can easily escape and become a conduction band electron.
Are free electron in valence band or conduction band?
In semiconductors free electrons are in conduction bands.
What is valence band?
It is the band of energy of an electron in outer most orbit
What electron flow is difficult between atoms?
valence band current flow.
what is the negative ion?
an atom with one or more extra electron(s) in its valence band. There are also molecular ions but they are more complicated to explain than simple atomic ions.
Possibility of holes in conduction band?
hoes are vacancies left by the electron in the valence band. hence there cannot be holes in the conduction band
What is the working principle of Light Emitting Diode and their commercial types?
when electron is excited from valence band to conduction band
How does the energy of core electron compare with the energy of valence electron?
valence electrons are bound to atoms and are used to bind atoms into molecules. free electron are free, either they are in the conduction band "electron gas" of a metal or they are in a vacuum (perhaps in a vacuum tube).
Effective density of states in conduction band?
All of the distributed electron states in the conduction band is represented by an effective density of states (NC)
What is recombination in electronics?
Process by which a conduction band electron gives up energy (in the form of heat or light) and falls into a valence band hole.
Are having eight valence electrons makes atoms very reactive?
No, eight valence electrons completely fills the valence band and makes the atom inert. The most reactive atoms have either one valence electron or seven valence electrons.
What is the difference between direct and indirect energy?
The band gap represents the minimum energy difference between the top of the valence band and the bottom of the conduction band, However, the top of the valence band and the bottom of the conduction band are not generally at the same value of the electron momentum. In a direct band gap semiconductor, the top of the valence band and the bottom of the conduction band occur at the same value of momentum.In an indirect band gap semiconductor, the maximum energy of the valence band occurs at a different value of momentum to the minimum in the conduction band energy
