Quantum dot

A Quantum Dot is a region in a semiconductor crystal that confines electrons, holes, or electron-hole pairs (so-called excitons) in three dimensions. The confinement to a region of a few nanometers up to a few hundred nanometers in size, which is on the order of the electrons' de Broglie wavelength, leads to quantized energy levels and to the quantization of charge in units of the elementary electric charge e. Compare to quantum wires (confined in 2D) and quantum wells (confined in 1D). Quantum Dots are particularly significant for optical applications due to their high quantum yield. Quantum Dots have also been suggested as implementations of a qubit for quantum information processing.

Related Topics:
Semiconductor - Crystal - Electrons - Holes - Excitons - De Broglie wavelength - Elementary electric charge - Quantum wire - Quantum well - Quantum yield - Qubit - Quantum information processing

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Because of the confinement, electrons in the Quantum Dot have quantized, discrete energy levels, much like an atom. For this reason, Quantum Dots are sometimes called "artificial atoms". The energy levels can be controlled by changing the size and shape of the Quantum Dot, and the depth of the potential. Like in atoms, the energy levels of small Quantum Dots can be probed by optical spectroscopy techniques. In contrast to atoms it is relatively easy to connect Quantum Dots by tunnel barriers to conducting leads, which allows the application of the techniques of tunneling spectroscopy for their investigation.

Related Topics:
Quantized - Atom

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One of the optical features of small excitonic Quantum Dots immediately noticeable to the unaided eye is coloration. While the material which makes up a Quantum Dot is significant, more significant in terms of coloration is the size. The larger the dot, the more towards the red end of the spectrum the fluorescence is. The smaller the dot, the bluer. Recent articles in Nanotechnology and other journals have begun to suggest that the shape of the Quantum Dot may well also be a factor in the colorization, but as yet not enough information has become available.

Related Topics:
Spectrum - Fluorescence - Nanotechnology

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The abilitiy to tune the size of Quantum Dots is advantageous, as the larger and more red-shifted the Quantum Dots is, the less the quantum properties are. The small size of the quantum dot allows us to take advantage of these quantum properties.

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