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ShareA quantum dot is a semiconductor nanostructure that confines the motion of conduction band electrons, valence band holes, or excitons (bound pairs of conduction band electrons and valence band holes) in all three spatial directions.
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The confinement can be due to electrostatic potentials (generated by external electrodes, doping, strain, impurities), the presence of an interface between different semiconductor materials (e.g.
in core-shell nanocrystal systems), the presence of the semiconductor surface (e.g.
semiconductor nanocrystal), or a combination of these.
A quantum dot has a discrete quantized energy spectrum.
The corresponding wave functions are spatially localized within the quantum dot, but extend over many periods of the crystal lattice.
A quantum dot contains a small finite number (of the order of 1-100) of conduction band electrons, valence band holes, or excitons, i.e., a finite number of elementary electric charges. Small quantum dots, such as colloidal semiconductor nanocrystals, can be as small as 2 to 10 nanometers, corresponding to 10 to 50 atoms in diameter and a total of 100 to 100,000 atoms within the quantum dot volume.
Self-assembled quantum dots are typically between 10 and 50 nm in size.
Quantum dots defined by lithographically patterned gate electrodes, or by etching on two-dimensional electron gases in semiconductor heterostructures can have lateral dimensions exceeding 100 nm.
At 10 nm in diameter, nearly 3 million quantum dots could be lined up end to end and fit within the width of a human thumb.
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