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Topic: Quantum well

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	Quantum well fires single electrons on demand
		Quantum computers, on the other hand, use the phenomenon of entanglement to operate on quantum bits, or "qubits", which can be both 0 and 1 at the same time.
		By applying a rapidly alternating voltage across the quantum dot and then a static voltage across the tunnel barrier they were able to shift the energy levels of the electrons in the quantum dot such that the electrons could enter or exit the 2DEG.
		Quantum dots have been used as single-electron sources before, but the device made by the French group is the first to be able to emit and absorb electrons over intervals of just a few nanoseconds, which makes the device's speed comparable with present-day electronics.
	www.iop.org /News/news_22376.html (388 words)

	Wireless nanocrystals efficiently radiate visible light
		The efficiency of the energy transfer from the quantum well to the nanocrystals was approximately 55 percent — although in theory nearly 100 percent transfer of the energy is possible and might be achieved with further tweaking.
		quantum dots) can be varied merely by controlling the size of the dot rather than by the standard, cumbersome process of varying the mix of materials, no known theoretical or practical barriers exist to pumping different-sized quantum dots that could individually emit blue, green, or red light, or be combined to generate white light.
		The thin-film quantum well crystal film was grown at Sandia by chemist Daniel Koleske.
	www.sandia.gov /news-center/news-releases/2004/micro-nano/well.html (617 words)

	Quantum well - Biocrawler (Site not responding. Last check: )
		A quantum well is a potential well that confines particles in one dimension, forcing them to occupy a planar region.
		Quantum wells are formed in semiconductors by having a material, like gallium arsenide sandwiched between two layers of a material with a wider bandgap, like aluminum arsenide.
		As a result quantum wells are in wide use in diode lasers.
	www.biocrawler.com /encyclopedia/Quantum_well (184 words)

	Spartanburg SC \| GoUpstate.com \| Spartanburg Herald-Journal (Site not responding. Last check: )
		A quantum well is a potential well that confines particles, which were originally free to move in three dimensions, to two dimensions, forcing them to occupy a planar region.
		Quantum wells are formed in semiconductors by having a material, like gallium arsenide sandwiched between two layers of a material with a wider bandgap, like aluminium arsenide.
		Quantum well infrared photodetectors are also based on quantum wells, and are used for infrared imaging.
	www.goupstate.com /apps/pbcs.dll/section?category=NEWS&template=wiki&text=quantum_well (260 words)

	What is a quantum well?
		A quantum well is analagous and represents the same concept: Energy.
		The laser that reads information of your discs is a quantum well laser and confines electrons by sandwiching materials together: simplistically, like a thin piece of capicolla between thick italian bread (forming the quantum well).
		Quantum weirdness is a reality and verified to unprecedented accuracies and is common place in our technological world.
	www.physlink.com /Education/AskExperts/ae528.cfm (581 words)

	Quantum Well
		A semiconductor quantum well (shown in theillustration in purple) is electrically excited bycurrent from a battery (marked as V).
		A quantum well is a semiconductor structure in which an electron is sandwiched between two barriers so that its motion is confined to two dimensions.
		Quantum dot research at Los Alamos has led to a number of innovations over the past several years, including news ways to observe and manipulate nanodots and methods for making semiconductor nanocrystals respond to photons by producing multiple electrons as a result of impact ionization (http://www.lanl.gov/orgs/pa/newsbulletin/2004/05/03/text02.shtml).
	pearl1.lanl.gov /external/Research/quantum_well.html (619 words)

	Quantum Potential Well Array (Site not responding. Last check: )
		In a classical problem, if a particle is in a well and has a total energy lower than the height of the well, then the particle is trapped with zero probability of begin found outside the potential well.
		The constants for the wave equation inside of the well (region III) now are only dependent of the height of the potential well, the energy of the particle, and the constant for the wave equation used in region II.
		The general reason that the study of multiple potential wells is desirable is that although it is a large simplification, it does approximate the state of electrons in a solid fairly well.
	www.scs.gmu.edu /~phys613c/QWellArrayy.htm (841 words)

	Integration of transistors with vertical cavity surface emitting lasers - Patent 5283447
		After the epitaxial formation of the layers, quantum well layer 30, spacer layer 40, and mirror layer 50 are defined by optical lithography and etching to form a plurality of columns 70.
		Advantageously, the active portion of the quantum well region is narrowed by a peripheral confinement region (not shown) similar to confinement region 33 of FIG.
		Again, each of the mirrors, spacers and quantum well of VCSEL 128 is made of several layers; and the active portion of the quantum well region is advantageously circumscribed by a confinement region 163'.
	www.freepatentsonline.com /5283447.html (7055 words)

	Spatial light modulator using charge coupled device with quantum wells - Patent 5105248
		A multiple quantum well structure having quantum well regions associated with the charge wells of said CCD structure, the charges in the CCD charge wells determining the value of the electric fields at said quantum well regions and, hence, the electro-absorption effects at said quantum well regions.
		An electro-optical device in accordance with claim 2 wherein the quantum well regions of said charge-coupled device are formed by alternating layers of materials having dissimilar energy characteristics, at least one of said layers acting as a source of electric charges for said quantum well regions.
		The CCD quantum well charges thereupon control or modulate the value of the electric field which is applied to the MQW structure so as to control the electro-absorption effect of the MQW in accordance with such modulated electric field.
	www.freepatentsonline.com /5105248.html (3001 words)

	The Research Scene - I shrunk my quantum well into a dot
		Actually, it is fortuitous that the quantum well turns out to be that simple since the excited valence electrons in a semiconductor still sense the periodic potentials of the atoms.
		Since many quantum dots are implanted in the insulating matrix and since the quantum dots have a variation in size, the lines are not absolutely sharp, but sharp enough to demonstrate the physics.
		Unlike multiple quantum wells which can be fabricated an atomic layer at a time (since the insulating substrate can be manipulated for deposition) the group at MIT have a much more difficult handling problem.
	www.spie.org /web/oer/october/oct96/quantum.html (632 words)

	Quantum structures
		Here j is the quantum number labeling the levels, and d is the thickness of the quantum well (the thickness of the layer shown in Fig.1a in the y direction).
		With an increase in the well thickness, d, the steps in Fig.2 gradually decrease and merge into an envelope parabolic function, which is equal to the three-dimensional density of states function multiplied by d (as shown by the thin line in Fig.2).
		are quantum numbers related to quantization in the y and z directions, dy and dz are dimensions of the quantum wire in the y and z directions, and where we assume that the dispersion relation for the electron energy in each subband is parabolic.
	www.mtmi.vu.lt /pfk/funkc_dariniai/nanostructures/quant_structures.htm (1295 words)

	Quantum Well Research May Result in Improved Disk-Drive Storage (Site not responding. Last check: )
		They are producing the first high quality images of "quantum wells" – an energy state in which an electron is sandwiched between two layers of atoms so that its motion is confined to a single dimension.
		Quantum well energy states are believed to be the basis for "oscillatory coupling" and giant magnetic resistance (GMR).
		The variation in photemission intensity from a single scan across the sample with ALS light was the result of wave interferences from quantum well states in the two layers.
	www.lbl.gov /Science-Articles/Archive/quantum-well-storage.html (1009 words)

	Chapter 5: Quantum Dot Lasers
		In addition, the use of a quantum well, with discrete transition energy levels dependent on the quantum well dimensions (thickness), provides a means of "tuning" the resulting wavelength of the material.
		The problem that plagued these quantum dot arrays was their exceedingly low optical efficiency: high surface-to-volume ratios of these nanostructures and associated high surface recombination rates, together with damage introduced during the fabrication itself, precluded the successful formation of a quantum dot laser.
		As with the demonstration of the advantages of the quantum well laser that preceded it, the full promise of the quantum dot laser must await advances in the understanding of the materials growth and optimization of the laser structure.
	www.wtec.org /loyola/nano/05_04.htm (845 words)

	Quantum Future Physics
		Well, the only thing that can happen to a wave in a wavy word is that the wave changes its shape.
		Well, unless the state is already known to us, then we can try to be clever and not disturb it.
		Quantum theory is so difficult, and there is so much brainwashing, that the student, after learning some of its abstract mathematics, after being discouraged so many times to ask questions that are said to make no sense - every student, no exception starts to believe that he now knows the secret of secrets.
	quantumfuture.net /quantum_future/qf-phys.htm (3516 words)

	Quantum Well-Being
		Quantum Well-Being works with creative, successful people living dynamic lives to facilitate your attainment of optimal Well-being.
		Quantum Well-Being has been working with people like you for 10 years, to increase their alignment of body-mind-spirit to well-being.
		The links to Clients, Services, and Testimonials show you some of the life situations that respond well to this approach, as well as the benefits of quantum biofeedback for well-being.
	www.quantumwellbeing.org (390 words)

	Silvaco - Products - Quantum
		Quantum provides a set of models for simulation of various effects of quantum confinement of carriers in semiconductor devices.
		Quantum gives you freedom to solve Schrodinger equations in either in 1D slices or full 2D of the device in order to find eigen bound state energies and wave functions.
		The gate bias is 0.5 V, the drain bias is 0.5 V and the carrier temperature at the position of the cross section is approximately 630 K. Quantum confinement effects are pronounced.
	www.silvaco.com /products/vwf/atlas/quantum3d/quantum_br.html (1229 words)

	Quantum well energizes nanocrystals (July 2004) - News - nanotechweb.org
		In real-life, however, they say they could also pump the quantum well electrically, in the same way that a common quantum-well light-emitting diode is pumped.
		Klimov and colleagues pumped the quantum well by shining laser light with a wavelength of 266 nm on the device.
		What's more, the researchers believe they may be able to achieve efficiencies of nearly 100% by improving the quality of the quantum wells to reduce non-radiative losses, and by optimizing the geometry of the nanocrystal/quantum-well structure.
	www.nanotechweb.org /articles/news/3/7/2/1 (429 words)

	Physics Today May 2001
		Fabrication of self-assembled quantum dots begins with some form of atomic deposition onto the surface of a semiconductor substrate, where the deposited material is chosen to have a smaller bandgap than the substrate.
		The exact shape and composition of the islands are not well known and depend on the growth procedure; in addition, complications are introduced by the complex band structure of the strained material and the effect of piezoelectric forces.
		The nonvanishing angular momentum of quantum rings in the presence of a magnetic field is closely related to the fascinating physics of the so-called persistent currents in mesoscopic rings.
	www.physicstoday.org /pt/vol-54/iss-5/p46.html (3213 words)

	Pumping energy to nanocrystals from a quantum well
		A quantum well is a semiconductor structure in which an electron is sandwiched between two barriers so that its motion is confined to two dimensions.
		In a real-life device, the quantum well would be pumped electrically in the same way a common quantum-well light-emitting diode is pumped.
		Quantum dot research at Los Alamos has led to a number of innovations over the past several years, including news ways to observe and manipulate nanodots and methods for making semiconductor nanocrystals respond to photons by producing multiple electrons as a result of impact ionization (http://www.lanl.gov/orgs/pa/newsbulletin/2004/05/03/text02.shtml).
	www.eurekalert.org /pub_releases/2004-06/danl-pet061104.php (533 words)

	Influence of Transit-Time and Quantum Well Negative Resistances on Quantum Well Oscillators
		Experimentally, the quantum well diode with the highest reported frequency of oscillation has required the use of moderately doped spacer layers approximately 0.5 micron thick on either side of the quantum well region [11, 13].
		The quantum well is treated as an injecting cathode whose small-signal equivalent circuit is the 'cold' (geometric) capacitance of the well, in parallel with a conductivity which represents the tunneling current (see Fig.
		For purposes of analysis we decouple the semi-classical transport occurring in the drift region from the quantum interference effects occurring in the quantum well [36].
	weewave.mer.utexas.edu /MED_files/MED_research/RTDs_QWITTs/QWITT_sml_sig/qwitt_sml_sig.html (4005 words)

	7th Int. Conf. on Narrow Gap Semiconductors
		A quantum well infrared photodetector which transform long wavelength infrared radiation into short wavelength or visible radiation are proposed and considered.
		The quantum well infrared photodetectors under concideration utilize the intraband absorption of infrared radiation in a quantum well and interband emission in either classical or quantum well in the collector.
		The absorption spectrum is defined by the energy separation in the quantum well and spectrum of emitted radiation is defined by the energy gap of narrow gap material of the collector well.
	www.u-aizu.ac.jp /labs/hw-cm/conf_reports/santafe.html (188 words)

	Spartanburg SC \| GoUpstate.com \| Spartanburg Herald-Journal (Site not responding. Last check: )
		The efficiency of a quantum well laser is greater than that of a bulk laser because the density of states function of electrons in the quantum well system has an abrupt edge that concentrates electrons in energy states that contribute to laser action.
		Further improvements in the laser efficiency have also been demonstrated by reducing the quantum well layer to a quantum wire or to a "sea" of quantum dots.
		In a quantum cascade laser, the difference between quantum well energy levels is used for the laser transition instead of the bandgap.
	www.goupstate.com /apps/pbcs.dll/section?category=NEWS&template=wiki&text=laser_diode (2983 words)

	Quantum well lasers target defence, printing - optics.org
		The compact, flexible units are based on Intense's Quantum Well Intermixing (QWI) process.
		This process increases the quantum well band-gap of a semiconductor laser in a controlled, precise manner, such that active and passive sections can be created in the same laser cavity.
		This produces a well controlled single mode beam in terms of spot size and pointing stability.
	www.optics.org /cws/Articles/ViewArticle.do?channel=technology&articleId=26647 (488 words)

	Quantum Physics: Finite Barrier Quantum Well, Britney Spears guide to Semiconductor Physics
		Quatum wells are important in semiconductor lasers because they allow some degree of freedom in the design of the emitted wavelength through adjustment of the energy levels within the well by careful consideration of the well width.
		In the case where the mass of the particle in the barrier differs from the mass of the particle in the well, then we introduce a scaling factor to account for this.
		The energy levels in the well are found from the intersection of the tangent and cotangent relationships with the circle within the positive quarter.
	britneyspears.ac /physics/fbarr/fbarr.html (394 words)

	Quantum Leaps News and Events
		Quantum Leaps, LLC released today its Quantum Platform (QP) family of frameworks to the SourceForge.net code repository.
		Quantum Platform Nano™ (QP-nano) has been released under the terms of the GPL open source license as well as traditional commercial licenses (dual licensing).
		Quantum Leaps provides an industry-strength implementation of the single-stack kernel, called Quantum Kernel (QK) that works exactly like SST and only differs in the way it is integrated with the state-machine event processor (QEP) and the state machine framework (QF).
	www.quantum-leaps.com /news/index.htm (857 words)

	Introduction to Quantum Well Devices (Site not responding. Last check: )
		When an electric field is applied perpendicular to the surface of a quantum well (or, equivalently, a voltage is applied between one side of the quantum well and the other), the optical absorption of the quantum well can be changed.
		The important point about quantum well materials is that this change in absorption is relatively large.
		In practice, speed is limited only by the time taken to apply voltage to the quantum wells, which is typically limited by resistor-capacitance limits of the external circuit.
	www.bell-labs.com /project/oevlsi/tutorial (768 words)

	Physics News Graphics: Photon Conveyor Belt in a Quantum Well
		Animation depicting a "photon conveyor belt" in a quantum well, an ultrathin layer of semiconductor material in which submicroscopic particles such as electrons are confined to move in two dimensions.
		Researchers at the University of Munich in Germany constructed a 10-nanometer-thick indium gallium arsenide (InGaAs) quantum well which is sandwiched by a 20-nanometer thick GaAs layer on the top and a 1-micron thick gallium arsenide (GaAs) substrate on the bottom.
		The energy of this light (or its color) is given by the effective bandgap of the given quantum well structure and thus can be largely chosen at will, as is the case for semiconductor lasers and light emitting diodes.
	www.aip.org /png/html/conveyor.htm (1159 words)

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