Quantum dots have a small, countable number of electrons confined in a small space. Their electrons are confined by having a tiny bit of conducting material surrounded on all sides by an insulating material. If the insulator is strong enough, and the conducting volume is small enough, then the confinement will force the electrons to have discrete (quantized) energy levels. These energy levels can influence the device behavior at a macroscopic scale, showing up, for example, as peaks in the conductance. Because of the quantized energy levels, quantum dots have been called "artificial atoms." Neighboring, weakly-coupled quantum dots have been called "artificial molecules."
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