Factbites
 Where results make sense
About us   |   Why use us?   |   Reviews   |   PR   |   Contact us  

Topic: Electron hole


Related Topics
DVD

  
  Electron hole - Wikipedia, the free encyclopedia
In solid state physics, an electron hole (usually referred to simply as a hole) is the absence of an electron from the otherwise full valence band.
The physicists therefore say that the hole must have positive charge—in fact, they assign a charge of +e—precisely the opposite of the electron charge.
In this scheme, the absence of an electron from a normally-filled state is called a "hole" and is treated as a particle, and the presence of an electron in a normally-empty state is simply called an "electron".
en.wikipedia.org /wiki/Electron_hole   (532 words)

  
 Kids.net.au - Encyclopedia Semiconductor -
Semiconductors are useful for electronic purposes because they can carry an electric current by electron propagation or hole propagation, and because this current is generally uni-directional and the amount of current may be influenced by an external agent (see diode, transistor, amplifier etc.).
Electron propagation is the same sort of current flow seen in a standard copper wire - heavily ionized atoms pass excess electrons down the wire from one atom to another in order to move from a more negatively ionized area to a less negatively ionized area.
"Hole" propagation is a rather different proposition - in the case of a semiconductor experiencing hole propagation, the charge moves from a more positively ionized area to a less positively ionized area by the movement of the electron hole created by the absence of an electron in a nearly-full electron shell.
www.kids.net.au /encyclopedia-wiki/se/Semiconductor   (1272 words)

  
 Electron hole - Encyclopedia.WorldSearch   (Site not responding. Last check: 2007-11-07)
A solid-state hole is seen as a free particle with an effective mass, possibly with incremental improvements on that model.
A physical chemistry hole is analysed by using the Schrödinger equation directly.
The electron-positron theory of the nucleus: And the constructive role of fl holes and of the neutrino and the antineutrino
encyclopedia.worldsearch.com /electron_hole.htm   (654 words)

  
 SAMI2: Electron Hole Formation
The reduction in the electron density occurs in the altitude range 1500 - 2500 km at geomagnetic equatorial latitudes.
The hole is produced by transhemispheric O+ flows that collisionally couple to H+ and transport it to lower altitudes, thereby reducing the electron density at high altitudes.
The reason for this is to focus on the hole formation mechanism; the zonal electric field does not cause the hole to form, although it does affect the time at which the hole forms.
wwwppd.nrl.navy.mil /whatsnew/sami2/SAMI2EHF3.html   (575 words)

  
 hole - a Whatis.com definition   (Site not responding. Last check: 2007-11-07)
In physics, a hole is an electric charge carrier with a positive charge, equal in magnitude but opposite in polarity to the charge on the electron.
Holes and electrons are the two types of charge carriers responsible for current in semiconductor materials.
A hole forms in an atom when an electron moves from the so-called valence band (the shell outside the closed shells that is partially or completely filled with electrons) into the conduction band (the outer "cloud" from which electrons most easily escape from, or are accepted by, the atom).
whatis.techtarget.com /definition/0,,sid9_gci214516,00.html?...   (350 words)

  
 Electron hole -- Facts, Info, and Encyclopedia article   (Site not responding. Last check: 2007-11-07)
In (Click link for more info and facts about solid state physics) solid state physics, an electron hole (usually referred to simply as a hole) is the absence of an (An elementary particle with negative charge) electron from the otherwise full (Click link for more info and facts about valence band) valence band.
The physicists therefore say that the hole must have positive (The price charged for some article or service) charge - in fact, they assign a charge of +e - precisely the opposite of the electron charge.
An alternate meaning for the term electron hole is used in (Click link for more info and facts about computational chemistry) computational chemistry.
www.absoluteastronomy.com /encyclopedia/e/el/electron_hole.htm   (663 words)

  
 Carrier recombination and generation
Recombination of electrons and holes is a process by which both carriers annihilate each other: electrons occupy through one or multiple steps the empty state associated with a hole.
Band-to-band recombination occurs when an electron falls from its state in the conduction band into the empty state in the valence band, which is associated with the hole.
Recombination in a depletion region and in situations where the hole and electron density are close to each other can not be described with the simple model and the more elaborate expressions for the individual recombination mechanisms must be used.
ece-www.colorado.edu /~bart/ecen5355/newbook/chapter2/recomb.htm   (1480 words)

  
 [No title]
The hole moves forward because the incoming nether has the quality of inertia and does not want to move toward the hole, and the only alternative is for the hole to move toward it.
The nether at the sides of the hole began to move inward at 45 degrees from the radial directions from the center of the hole.
The electron and the positron are self-regulating and maintain a particular hole size, "spin" magnitude, and magnitude of forces (charge, sub-atomic gravity, etc.), according to the nether pressure versus the vacuum at their centers.
www.softcom.net /users/greebo/electron.htm   (1868 words)

  
 Intrinsic Semiconductors
That is, the electrons which have been freed from their lattice positions into the conduction band can move through the material.
The current flow in an intrinsic semiconductor is influenced by the density of energy states which in turn influences the electron density in the conduction band.
When the electron in pure silicon crosses the gap, it leaves behind an electron vacancy or "hole" in the regular silicon lattice.
hyperphysics.phy-astr.gsu.edu /hbase/solids/intrin.html   (371 words)

  
 Hole superconductivity
A 'hole' is the absence of an electron, and hole carriers exist when an electronic energy band is almost full.
The different mobility of holes and electrons can be illustrated by a garage analogy.
The reason for the increased mobility of holes upon pairing is that they 'undress' when they pair, and turn into electrons.
physics.ucsd.edu /~jorge/hole.html   (1462 words)

  
 Station Information - Electron hole
The concept is of a hole is essentially a simple way to analyse the movement of large numbers of electrons in such substances.
If those people were charged (like electrons), this movement would constitute conduction.
It turns out that effective mass is fairly independent of velocity or direction, which means physicists can (in some cases) pretend that the hole is simply a positive charge moving through a vacuum, with a mass of, say 0.36m
www.stationinformation.com /encyclopedia/e/el/electron_hole.html   (535 words)

  
 Why is an Electron not a Black Hole?   (Site not responding. Last check: 2007-11-07)
Well, all fl holes have a horizon which is the radius where light itself couldn't escape -- or in other words it is where the escape velocity Vesc = C (the speed of light).
Because of the size of the electron it resides in the quantum world, and at present scientific knowledge "We don't know what a horizon means when quantum gets into the act." ~Charles Goebel.
A fl hole's gravitational field causes particle-antiparticle pairs to be produced in the vicinity of the event horizon at the Schwarzschild radius.
cow.physics.wisc.edu /~ogelman/guide/e   (515 words)

  
 [No title]
Less energy is expended in moving the electron toward the inflow than is expended in pulling all of the inflow toward the electron mouth.
Before each reversal the electron is decelerating in its polar direction of movement, and after each reversal the electron is accelerating in its polar direction of movement.
During the reversal, the electron vortex is taking in nether at a constant rate, producing a number of "revolutions" of nether entry equal to "n" which is the effect that creates the half-wave acceleration of light.
www.softcom.net /users/greebo/plncklen.htm   (3720 words)

  
 Exciton   (Site not responding. Last check: 2007-11-07)
An exciton is a bound state of an electron and a mathematically useful imaginary particle called an electron hole in an insulator (or semiconductor), or in other words, a Coulomb correlated electron/hole pair.
The missing electron in the valence band leaves a hole behind, of opposite electric charge, to which it is attracted by the Coulomb force.
As a result, the effect of the lattice potential can be incorporated into the effective masses of the electron and hole, and because of the lower masses and the screened Coulomb interaction, the binding energy is usually much less than a hydrogen atom, typically on the order of 0.1 eV.
www.worldhistory.com /wiki/E/Exciton.htm   (582 words)

  
 Glossary of Electron Microscopy Terms
Detection of Backscattered Electrons is achieved by using a "donut" shaped solid state semiconductor device mounted on the bottom of the objective lens.
An electron probe is tightly focused on a TEM specimen and the resulting pattern of diffracted electrons is observed.
Electrons and their orbits around the nucleus of an atom account for most of the physical properties of the element.
www.unl.edu /CMRAcfem/glossary.htm   (1402 words)

  
 Capturing Excitons in Transition
The electron is moved into the conduction band, up from the valence band where it is tightly bound to the parent atom, and leaves behind a vacancy or "hole" that acts like a positively charged particle.
Electron and hole -- being oppositely charged -- attract each other via the same Coulomb force that stabilizes the shapes of atoms or molecules.
Temporal snapshots of the correlated motion between electrons and holes in a semiconductor nanostructure: terahertz (THz) conductivity sharpens up on a picosecond time scale as excitons take shape.
enews.lbl.gov /Science-Articles/Archive/ALS-capturing-excitons.html   (973 words)

  
 Quantum mechanical semiconductor device with electron/hole diffractive grating - Patent 5191216
An electron wave of energy E and wavevector k' is incident from the input region at an angle.theta.' and is diffracted into forward- and backward-diffracted orders in regions III and I respectively.
is the electron wave amplitude, h is Planck's constant divided by 2.pi., and m* and V are the periodic effective mass and potential energy in the grating (periodic with grating vector K).
In an analogous manner, the diffraction efficiency for electron wave gratings is defined as the ratio of the z-component of the probability current carried by the ith diffracted order to the z-component of the probability current of the incident wave.
www.freepatentsonline.com /5191216.html   (6493 words)

  
 ScienceWeek
In quantum mechanics, electrons, protons, and neutrons have an intrinsic angular momentum known as "spin", and a magnetic moment parallel or antiparallel to that angular momentum.
When electrons are combined together to form an atom or ion, there is a resultant angular momentum which is a combination of the intrinsic spin of the electrons and the angular momentum due to their motion about the nucleus, and this is the "spin" of the atom or ion.
2) The fundamental constituents of atoms (electrons, neutrons, and protons) are fermions.
scienceweek.com /2003/sw030404.htm   (10906 words)

  
 APS - 2005 APS March Meeting PostDeadline - Event - Electron-hole excitations in CaMnO$_{3}$ and LaMnO$_{3}$(*)   (Site not responding. Last check: 2007-11-07)
The electron dynamics is handled within the random-phase approximation (RPA).
The loss spectrum in both materials is dominated by a striking “collective” excitation; the same is directly related to the underlying electronic structure, as its energy is a signature of the relative location of the upper and lower Hubbard bands.
The physics of the dynamical screening (the spectral weight of the leading excitation, its remarkable dependence on wave vector (both on the magnitude and direction of q, etc.) is controlled by d-d transitions and the microscopic crystal local fields.
meetings.aps.org /Meeting/MAR05/Event/27262   (224 words)

  
 Electron hole: Definition and Links by Encyclopedian.com - All about Electron hole   (Site not responding. Last check: 2007-11-07)
Electron hole: Definition and Links by Encyclopedian.com - All about Electron hole
In semiconductors and insulators, an electron hole (usually referred to simply as a hole) is the absence of an electron from the otherwise full valence band.
It is essentially a simple way to analyse the movement of large numbers of electrons.
www.encyclopedian.com /el/Electron-hole.html   (396 words)

  
 5.2 Auger Electron Spectroscopy
It is a surface specific technique utilising the emission of low energy electrons in the Auger process and is one of the most commonly employed surface analytical techniques for determining the composition of the surface layers of a sample.
Such electrons have sufficient energy to ionise all levels of the lighter elements, and higher core levels of the heavier elements.
When describing the transition, the initial hole location is given first, followed by the locations of the final two holes in order of decreasing binding energy.
www.chem.qmw.ac.uk /surfaces/scc/scat5_2.htm   (1110 words)

  
 SPACE.com -- Natural Electron Beam Carves Hole in Ionosphere, Leaves Clues of Aurora
Electrons flung earthward by the Sun strike a few atoms in the planet's very thin upper atmosphere.
The electrons spotted by Cluster were evacuated into space, the researchers say, leaving a hole in the ionosphere.
Marklund and his colleagues suggest that the electron beam allowed a corresponding downward beam to develop, which led to visible aurora.
www.space.com /scienceastronomy/planetearth/aurora_agu_011210.html   (707 words)

  
 Journal of Theoretics
Besides, it would be highly desirable to define the fl hole with the Planck time and mass only and have all the electron properties of charge, mass, etc, without introducing any additional parameters.
The remaining difference in the electron mass could be explained as the energy necessary to set up the polarization of the vacuum: calculations indicate that this will account for about 80% of the difference.
The electron mass can be calculated by means of other quantum constants and its gravitational force can be related directly to the electron charge and permittivity.
www.journaloftheoretics.com /Articles/2-5/bh-DiMario/DiMario.htm   (4221 words)

  
 Jakyoung song :: Electron-hole pair processes via semiempirical methodology.   (Site not responding. Last check: 2007-11-07)
Moreover, a time-dependent propagation method is adapted to propagate the excited electron and the valence hole states in a lattice.
The coupling of the electron and hole states with phonons is calculated as a force contribution of the electron-hole pair to the ion, and a molecular dynamics simulation is performed by using this.
The electronic and geometric structural properties corresponding to the relaxation processes of exciton in the networked systems are described.
www.emsl.pnl.gov /docs/wctcc98/abstracted/Jakyoung_song_abstract.html   (209 words)

  
 Electron-hole symmetry in a semiconducting carbon nanotube quantum dot : Nature   (Site not responding. Last check: 2007-11-07)
Optical and electronic phenomena in solids arise from the behaviour of electrons and holes (unoccupied states in a filled electron sea).
By applying a voltage to a gate electrode, an individual nanotube is filled controllably with a precise number of either electrons or holes, starting from one.
The discrete excitation spectrum for a nanotube with N holes is strikingly similar to the corresponding spectrum for N electrons.
dx.doi.org /10.1038/Nature02568   (307 words)

  
 Beam Up an Electron
Such entangled particles should arise from splitting isolated electron pairs [1], but this effect hasn't been clearly observed yet, in part because the structures are hard to make.
The annihilated electron would then disappear into the electron sea, but its quantum state would be preserved in the surviving electron because of the entanglement.
Daniel Loss of the University of Basel in Switzerland questions whether electrons can survive even the short time needed for annihilation without forgetting the orbital part of their quantum state, which is essential to entanglement.
focus.aps.org /story/v13/st6   (643 words)

Try your search on: Qwika (all wikis)

Factbites
  About us   |   Why use us?   |   Reviews   |   Press   |   Contact us  
Copyright © 2005-2007 www.factbites.com Usage implies agreement with terms.