Basic introduction of quantum dots

Quantum Dot is a semiconductor nanostructure that binds conduction band electrons, valence band holes and excitons in three spatial directions. The motion of quantum dots and electrons is limited in three-dimensional space, so they are sometimes called "artificial atoms", "superlattices", "super atoms" or "quantum dot atoms", which is a new concept put forward in the 1990s. Quantum dots are semiconductor nanostructures that bind conduction band electrons, valence band holes and excitons in three spatial directions. This limitation can be attributed to the electrostatic potential (caused by external electrodes, doping, strain and impurities), the interface between two different semiconductor materials (for example, in self-assembled quantum dots), the surface of the semiconductor (for example, semiconductor nanocrystals), or a combination of the above three. Quantum dots have independent quantized energy spectra. The corresponding wave function is located in the quantum dot in space, but it extends in several lattice periods. Quantum dots have a few (1- 100) electron, hole or hole electron pairs, that is, the amount of electricity they carry is an integer multiple of that of elementary charge.

Quantum dots, also known as nanocrystals, are nanoparticles composed of II-VI or II-VI-V elements. The particle size of quantum dots is generally between 1 ~ 10nm. Due to the quantum confinement of electrons and holes, the continuous energy band structure becomes a discrete energy level structure with molecular characteristics, which can emit fluorescence after being excited. Based on quantum effect, quantum dots have a wide application prospect in solar cells, light-emitting devices, optical biomarkers and other fields. Scientists have invented many different methods to make quantum dots, and it is predicted that this nano-material will have great application potential in nanoelectronics in 2 1 century.

Small quantum dots, such as colloidal semiconductor nanocrystals, can be as small as 2 to 10 nanometers, which is equivalent to a diameter of 10 to 50 atoms. A quantum dot volume can contain 100 to100,000 such atoms. The typical size of self-assembled quantum dots is between 10 and 50 nm. The lateral size of quantum dots formed by photoetching gate electrodes or etching two-dimensional electron gas in semiconductor heterojunction can exceed 100 nm. 3 million quantum dots with the size of 10 nanometer are arranged end to end, which can reach the width of human thumb.