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Quantum dots are nano-meter-scale "boxes" for selectively holding or releasing electrons.  Quantum Interference In the last 14 years they've been transformed from laboratory curiosities to the building blocks for the next computer industry. Quantum dots are small metal or semiconductor boxes that hold a well-defined quantity of electrons. The amount of electrons in a dot may be adjusted by changing the dot's electrostatic environment. Dots have already been made which range from 30nm to 1 micron in proportions, and holding from zero to countless electrons.

Brief History

During the1980's ideas regarding the Quantum Dot surfaced when researchers in the field of computing were wanting to construct something near "nano-scale" in the field of computing.

The Mechanism of Quantum Dot

By utilizing an external light (e.g. Ultraviolet) on nano-crystals (e.g. produced from semiconductor materials such as zinc sulphide, cadmium selenide, indium phosphide or lead sulphide), the nano-crystal will absorb the light and then, as a result of the crystal being stimulated by the absorbed light, it'll re-emit the light, usually of a specific colour, with regards to the size of the quantum dot.

It has been observed in experiments and shown theoretically that reducing the dimensions of a quantum dot raises the effective operating temperature of the electron confinement device. Current quantum dots are big enough (approximately 1-10 microns long and wide) that they might require cooling with liquid helium or, at least, liquid nitrogen, to cryogenic temperatures. However, for a functional technology with widespread applications in relation to such quantum-effect devices, it will be necessary to attain room temperature operation. This requirement implies that it is essential to invent and manufacture molecular-scale quantum dots that are only approximately 1 to 10 nanometers in linear dimension. This type of quantum dot could possibly be constructed as just one molecule i.e. a molecular quantum dot. Molecular quantum dots are one of these of the next-generation technology called Molecular-scale electronics.

Professor James Tour of the University of South Carolina and Professor Mark Reed of Rale University are collaborating on the chemical synthesis and testing of molecular wires. These operate by allowing electrons to maneuver nearly ballistically along along a string of ring-like chemical structures with conjugated pi-orbitals.

It has been suggested by Tour and by others, that it may be possible to insert chemical categories of lower conductance into this kind of molecular wire, creating paired barriers to electron migration through the chain. Such barriers might develop a molecular quantum-effect device that could function in a manner similar to solid-state resonance tunnelling devices that already have already been fabricated, tested, and applied in prototype quantum-effect logic.

Work in your community of quantum-based devices for nano-scale metrology will be directed to fabricating an ultra-small SQUID (Superconducting Quantum Interference Device) for applications in single-particle detection. The fabrication of this kind of device is a significant achievement, and should prove important in areas such as future nano-scale frequency standards, emerging quantum computer and single-particle sensor technologies and in the study of adatom-surface interactions.

Many researchers in nano-electronics are talking of a possible architecture for computer logic predicated on quantum dots. As mentioned previously, a quantum dot is a box that holds a discrete quantity of electrons. Adjusting electric fields in the neighbourhood of the dot, as an example by making use of a voltage to a nearby metal gate, can change this number. Needless to say, since quantum dots are fabricated in solids, not in vacuum, there are numerous electrons in them. However, the vast majority of they are tightly bound to atoms in the solid. The few electrons spoken of are extra ones beyond those who are tightly bound. These extra electrons could roam free in a good were they're not confined in a quantum dot.

In nano-structures, the electrical properties can be markedly different from their macroscopic equivalents thereby revealing many novel effects. "Progress in the field has been hampered by two problems," said Arizona State University Chemistry Professor Devens Gust. "The first has been around making robust, reproducible electrical connections to both ends of molecules. After it has been achieved, another problem is knowing how many molecules there actually are between the electrical contacts."