Quantum confinement

Quantum confinement occurs when a structure restricts charge carriers to dimensions comparable to their quantum-mechanical wavelength, making allowed energy states depend on the structure’s size and shape.

Particle in a box: A quantum-mechanical model in which a particle is confined to a bounded region and has discrete energy levels. Its size-dependent energy levels provide the simplest model of confinement.
de Broglie wavelength: The wavelength associated with a particle’s momentum, given by Planck’s constant divided by that momentum. Confinement becomes significant when a structure’s dimensions approach carrier wavelengths.
Quantum-dot display: A display technology that uses semiconductor quantum dots to produce spectrally narrow colors. Size-dependent emission helps quantum dots generate saturated display colors.
Quantum size effect: A change in material properties caused by quantum confinement as a structure’s dimensions shrink. This effect describes the measurable consequences of confinement, rather than the restriction itself.
Density of states: The number of available quantum states per energy interval in a system. Confinement changes how available electronic states are distributed across energy.
Semiconductor: A material whose electrical conductivity lies between that of a conductor and an insulator and can be controlled by doping or fields. Semiconductors provide the band structure and carriers commonly shaped by confinement.
Quantum-dot solar cell: A photovoltaic device that uses semiconductor quantum dots as light absorbers or charge-generating components. Tunable absorption makes confined nanocrystals candidates for photovoltaic devices.
Quantum tunneling: The passage of a quantum particle through a barrier that classical physics treats as impassable. Tunneling crosses barriers; confinement instead restricts motion and quantizes allowed states.
Band gap: The energy range separating a material’s valence-band states from its conduction-band states. In semiconductor nanostructures, confinement can shift the effective band gap.
Nanostructure: A material structure with at least one dimension on the nanometer scale. Nanostructures can restrict carrier motion along selected dimensions.

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