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	Valence band - Wikipedia, the free encyclopedia
		In solids, the valence band is the highest range of electron energies where electrons are normally present at zero temperature.
		In metals, the conduction band is the valence band.
		Once they are in the conduction band, they can conduct electricity, as can the hole they left behind in the valence band.
	en.wikipedia.org /wiki/Valence_band (326 words)

	Band gap - Wikipedia, the free encyclopedia
		In solid state physics and related applied fields, the band gap is the energy difference between the top of the valence band and the bottom of the conduction band in insulators and semiconductors.
		The only available carriers for conduction are the electrons which have enough thermal energy to be excited across the band gap, which is defined as the energy level difference between the conduction band and the valence band.
		Band gap engineering is the process of controlling or altering the band gap of a material by controlling the composition of certain semiconductor alloys, such as GaAlAs, InGaAs, and InAlAs.
	en.wikipedia.org /wiki/Band_gap (335 words)

	Band Theory for Solids
		In insulators the electrons in the valence band are separated by a large gap from the conduction band, in conductors like metals the valence band overlaps the conduction band, and in semiconductors there is a small enough gap between the valence and conduction bands that thermal or other excitations can bridge the gap.
		Most solid substances are insulators, and in terms of the band theory of solids this implies that there is a large forbidden gap between the energies of the valence electrons and the energy at which the electrons can move freely through the material (the conduction band).
		In the band theory, this is depicted as an overlap of the valence band and the conduction band so that at least a fraction of the valence electrons can move through the material.
	hyperphysics.phy-astr.gsu.edu /hbase/solids/band.html (623 words)

	Valence band -- Facts, Info, and Encyclopedia article (Site not responding. Last check: 2007-11-07)
		In (A three-dimensional shape) solids, the valence band is the highest range of (An elementary particle with negative charge) electron (Click link for more info and facts about energies) energies where electrons are normally present at zero (The degree of hotness or coldness of a body or environment (corresponding to its molecular activity)) temperature.
		Semiconductors and insulators owe their low (The transmission of heat or electricity or sound) conductivity to the properties of the valence band in those materials.
		Once they are in the conduction band, they can conduct electricity, as can the (An opening deliberately made in or through something) hole they left behind in the valence band.
	www.absoluteastronomy.com /encyclopedia/v/va/valence_band.htm (415 words)

	Semiconductor device having a semiconductor region in which either the conduction or valence band remains flat while ...
		However, in that case, the band level of the valence band and that of the conduction band are graded at the same time and because of this, it becomes impossible to unifunctionally and continuously increase or decrease only one of the two band levels and to maintain the remaining band level in a flat state.
		As for the band gap of the second layer region for the resultant sample, it was found that it is 1.7 eV for the amorphous layer region not containing germanium atom and that it is 1.45 eV for the amorphous layer region containing germanium atom.
		As for the band gap of the second layer region for the resultant sample, it was found that it is 1.7 eV for the amorphous layer region not containing carbon atom and that it is 1.45 eV for the amorphous layer region containing carbon atom.
	www.freepatentsonline.com /4887134.html (7478 words)

	Bands, Bonds, and Doping
		As in metal solids, the valence atomic orbitals lose their individual identity in the aggregate of C atoms, and "mix" to form a band of orbitals that are close in energy.
		The lower-energy band consists of filled orbitals (i.e., orbitals containing electrons) and is known as the "valence band"; the higher-energy band consists of unfilled orbitals and is known as the "conduction band".
		The band gap in semimetals is small enough (recall Figure 5) that an electron can be promoted from the filled lower-energy band to the unfilled higher-energy band with a moderate input of energy (such as the thermal energy that dissipates in the solid when electrical current is passed through it).
	www.chemistry.wustl.edu /~edudev/LabTutorials/PeriodicProperties/MetalBonding/MetalBonding.html (4697 words)

	electrical properties of C containing alloys on SI (001) (Site not responding. Last check: 2007-11-07)
		The valence band offset between compressive strained layers and Si is generally much larger than that at the tensile strained layer/Si interface.
		Strain effects on the conduction band are similar to those discussed for the valence band in the previous chapter.
		The degeneracy of the conduction bands in Si and Ge is different in nature from that of the valence bands.
	www.ihp-ffo.de /SiGeC/03_Elect.htm (5404 words)

	Chapter One (Site not responding. Last check: 2007-11-07)
		A semiconductor is a crystalline substance having a band structure in which a filled valence band is separated from an empty conduction band by a narrow bandgap.
		The first process is that the transfer of an electron from a state near the valence band maximum to a state with approximately the same wave vector near the conduction band minimum, usually at the center of the Brillouin zone.
		The second process is that the transfer of an electron from a state near the valence band maximum to a state with a different wave vector near the conduction band minimum.
	www.physics.uc.edu /~thuang/dissertation/chapter_1.html (2255 words)

	Effective mass in semiconductors
		In this section we first describe the different relevant band minima and maxima, present the numeric values for germanium, silicon and gallium arsenide and introduce the effective mass for density of states calculations and the effective mass for conductivity calculations.
		for instance for a single band minimum described by a longitudinal mass and two transverse masses the effective mass for density of states calculations is the geometric mean of the three masses.
		Due to the fact that the heavy hole band does not have a spherical symmetry there is a discrepancy between the actual effective mass for density of states and conductivity calculations (number on the right) and the calculated value (number on the left) which is based on spherical constant-energy surfaces.
	ece-www.colorado.edu /~bart/book/effmass.htm (730 words)

	Britney's Guide to Semiconductor Basics
		Often, we are interested in transitions that occur near the bottom of the conduction band minimum to valence band maximum; In this case, the is useful to draw the bandstructure energy as a function of position, setting the wavevector k =0.
		The valence band maximum is at k =0, is known as the gamma point.
		The bands in a semiconductor material are approximated by parabolic functions of k close to the bandedges.
	britneyspears.ac /physics/basics/basics.htm (2065 words)

	Principles - Some semiconductor physics - Band structure (Site not responding. Last check: 2007-11-07)
		The next higher band is the conduction band which is separated from the valence band by the energy gap, or bandgap.
		Four of the five outer electrons are used to fill the valence band and the one extra electron from each impurity atom is therefore promoted to the conduction band.
		The electrons in the conduction band are mobile, and the crystal becomes a conductor.
	www.soton.ac.uk /~solar/intro/tech3.htm (504 words)

	THE UNIVERSITY OF QUEENSLAND
		The higher energy band which is separated from the valence band is empty and is known as the conduction band.
		It is the distribution of electrons between the valence band and the conduction band which determine the electrical properties of a piece of semiconductor.
		In general we are only interested in the electrons that ae present at or near the top of the valence band and at or near the bottom of the conduction band.
	www.itee.uq.edu.au /~elec3200/lectures/L1.htm (1775 words)

	NSM Archive - Silicon Carbide (SiC) - Band structure
		Important minima of the conduction band and maxima of the valence band.
		is the effective mass of the density of states in one valley of conduction band.
		Due to the small spin-orbit splitting the valence bands are highly non-parabolic, i.e.
	www.ioffe.ru /SVA/NSM/Semicond/SiC/bandstr.html (485 words)

	Semiconductors
		In a semiconductor, increased thermal energy causes electrons to move from the valence band to the _________ ________.
		At absolute zero, all of the outer electrons in a semiconductor are in the valence band and the material acts as an insulator.
		When a semiconductor such as Silicon is heated, electrons jump the energy gap from the valence band to the conduction band, leaving a hole.
	school.discovery.com /quizzes26/ccphysics/semiconductors.html (571 words)

	Conductors, Insulators, and Semi-Conductors (Site not responding. Last check: 2007-11-07)
		The conduction band is composed of the excited energy states of a substance, and it contains electrons that have been thermally or otherwise excited from the valence band.
		In conductors, the valence band and the conduction band overlap.
		However, the energy gap between these two bands is neither as large nor as significant (typically around one electron-volt) as is the band gap in insulators.
	www.tunl.duke.edu /~cosen/phy217/MottScatteringReport/node18.html (523 words)

	2.2.4 Electrons and holes in semiconductors
		A uniform electric field is assumed which causes a constant gradient of the conduction and valence band edges as well as a constant gradient of the vacuum level.
		The electrons in the conduction band are negatively charged particles which therefore move in a direction which opposes the direction of the field.
		This expression can be reformulated by first taking the sum over all the states in the valence band and subtracting the current due to the electrons which are actually missing in the valence band.
	ece-www.colorado.edu /~bart/book/eband4.htm (655 words)

	[No title]
		Now apply degenerate perturbation theory to describe the splittings of the valence states of the spherical ions.\cite{ballhausen:1962} The splitting of the O $2p$ states is dominated by the Coulomb attraction of the electron to the nearest neighbor B$^{+\beta}$ ion.
		Contour levels corresponding to the occupied electron density in the valence band are indicated on this plane with lowest contour level at 0.1~e/\AA$^3$ and with a spacing of 0.25~e/\AA$^3$ between contours.} \label{cryst} \end{figure} \begin{figure} \caption{Plot of total densities of states per unit cell for the four ABO$_4$ scheelite materials, evaluated using Eq.
		The bands are plotted along the ${\bf{\hat{z}}}$ (c) axis from $\Gamma$ to Z and within the a plane from its boundary at $\frac{\pi}{a}(1 + \left(\frac{a}{c} \right)^2)$ along the $\Sigma$ direction to the $\Gamma$ point and from the $\Gamma$ point along the $\Delta$ direction to the X point, where the labels correspond to Fig.
	users.wfu.edu /natalie/papers/cmo/submit.txt (4703 words)

	Home Page
		A band gap is formed between these two bands due to forbidden zones in which the wave functions are not allowed.
		The lowest state band is commonly referred to as the valence band, and this band is usually full.
		For small band gaps (on the order of a few eVs), it is possible for a modest voltage to provide enough energy to place electrons in the conduction band, thus allowing for a modest current through the semiconductor.
	webphysics.davidson.edu /students/papriestley/semiconductor/myweb/semiconductor.htm (760 words)

	The Physics of Photovoltaic Cells
		The valence electrons move in the space between the two atoms with energies in a band of energies known as the valence band (Fig.
		Their energies are in another band known as the conduction band at a higher energy level than the valence band.
		Between the highest energy level in the valence band and the lowest energy level in the conduction band there may be a forbidden band of energies.
	www.jgsee.kmutt.ac.th /exell/Solar/PVCells.html (2297 words)

	Doped Semiconductors (Site not responding. Last check: 2007-11-07)
		The application of band theory to n-type and p-type semiconductors shows that extra levels have been added by the impurities.
		In p-type material, extra holes in the band gap allow excitation of valence band electrons, leaving mobile holes in the valence band.
		The addition of acceptor impurities contributes hole levels low in the semiconductor band gap so that electrons can be easily excited from the valence band into these levels, leaving mobile holes in the valence band.
	hyperphysics.phy-astr.gsu.edu /hbase/solids/dsem.html (258 words)

	[No title]
		The lowest energy of CB is called the conduction band edge, denoted as Ec, and is equal to the top of energy gap; and the highest energy of VB is called the valence band egde, denoted as Ev, and is equal to the bottom of energy gap.
		This situation, in the energy band terms, is that the CB is completely empty of electrons, and the VB is fully occupied by the valence electrons (and therefore no empty states which are by definition the holes).
		This, in the energy band terms, means that a valence electron (in VB, localized and not mobile) is thermally excited into the CB (where the electron is mobile), leaving behind an unoccupied state in the valence band.
	jas.eng.buffalo.edu /education/semicon/fermi/bandAndLevel/intro.html (814 words)

	Heterojunction Band Alignment
		As with all semiconductor devices, the key to understanding the behavior of heterojunctions is the energy-band profile which graphs the energy of the conduction and valence band edges versus position.
		The topology of the band alignments are classified according to the relative ordering of the band-edge energies [29].
		The conduction band of the smaller-gap material might lie above that of the larger-gap material, or its valence band might lie below that of the larger-gap material.
	www.utdallas.edu /dept/ee/frensley/technical/hetphys/node7.html (677 words)

	Selected Publications--Professor Peter M.A. Sherwood (Site not responding. Last check: 2007-11-07)
		Peter M.A. Sherwood, “Valence Band Photoelectron Spectroscopy as a Probe of the Surface Chemistry Associated with Corrosion and its Prevention, Proceedings of the Electrochemical Society, PV 2001-5 (State-of-the-Art Application of Surface and Interface Analysis Methods to Environmental Material Interactions: In Honor of James E. Castle’s 65
		Temesghen and P.M.A. Sherwood, “Valence Band X-ray Photoelectron Spectroscopic Studies of Iron and its Oxides interpreted by Cluster and Band Structure Calculations”, Analytical and Bioanalytical Chemistry - in press.
		Xie and P.M.A. Sherwood, "X-ray Photoelectron Spectroscopic Study of Kevlar Fiber and the Valence Band Interpretation by Xa Calculations",Chem.
	www.k-state.edu /chem/faculty/grad/pmas/sherwood_pub.html (678 words)

	Valence - Wikipedia, the free encyclopedia
		In psychology and neuroscience, valence refers to the emotional value associated with a stimulus; e.g., a familiar face can have positive valence.
		Valence is the name of several communes of France:
		This is a disambiguation page, a list of pages that otherwise might share the same title.
	en.wikipedia.org /wiki/Valence (96 words)

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