quantumconfined

Quantumconfined is a descriptor used to refer to systems in which particles such as electrons are restricted to dimensions comparable to their de Broglie wavelength, producing quantized energy levels and altered electronic, optical, and transport properties. The term is often used to describe states or materials that experience quantum confinement.

In nanostructures, confinement occurs in different dimensions: quantum wells (two-dimensional confinement), quantum wires (one-dimensional), and quantum dots (zero-dimensional). The simple particle-in-a-box picture shows energy levels that scale roughly with 1/L^2 as the confinement length L decreases. More realistic models use the effective mass approximation and include band structure, strain, and interfaces.

Consequences include size-dependent spectra: absorption and emission features shift to higher energies (blue shift) as size shrinks, reflecting an increased effective band gap. Excitons and Coulomb interactions, surface states, and nonparabolic bands can modify energies and lifetimes. The onset of quantum confinement typically occurs when the confinement length approaches the exciton Bohr radius.

Materials are diverse, including semiconductor nanocrystals such as colloidal quantum dots, epitaxial quantum wells and nanowires, and atomically thin layers like transition metal dichalcogenides that show confinement in the out-of-plane direction. Synthesis, surface chemistry, and strain influence the degree of confinement.

Applications span optoelectronics, light-emitting diodes, lasers, photodetectors, solar cells, and bio-imaging, where tunable spectra and enhanced quantum efficiencies arise from confinement. The concept underpins quantum size effects in nanoscale materials.

See also: quantum confinement, quantum dot, quantum well, quantum wire, exciton, nanostructure.