Science of nanomaterials by Unknown

Author:Unknown
Language: eng
Format: azw3
Published: 2016-01-19T16:00:00+00:00

Nanowires are wires of a diameter of the order of a nanometer. Nanowires can be defined as structures that have a lateral size restricted to ten or less nanometers in general, even thought Turkish Scientifics in the University of Bilkent of Ankara are achieving creating nanowires of 15 nanometers of diameter and free length. Because of their relationship length-width they have been considered as one-dimensional, that is why they present striking properties that haven’t been seen in materials of 3 dimensions, since in these nanowires second quantic effects are not produced in the borders. It can be conductors or isolators depending on the element of which they are fabricated. Their potential applications are in electronics, optoelectronic devices, also in nanoelectromechanical devices.

4.4. Quantum dots A quantum dot is a crystalline structure of nanometrical dimensions that can present diverse shapes, and is usually made of semiconductor materials. In a quantum dot, the electrons are trapped, confined in the three dimensions. This confinement gives place to a structure well defined of energy levels that depends a lot of the shape and size of the quantum dot. This disposal of electronic levels reminds to the one that has atoms and this is why they are also called “artificial atoms”. Controlling the shape and size of the quantum dot we can control its structure and, therefore, the spectrum of light they emit. This control of optical properties has made that quantum dots are used to fabricate efficient laser diodes (used as CD-DVD players), photovoltaic cells, so as new dyes and optical markers that allow the tracing of biological processes in real time.

Other interesting property of a quantum dot is that its electronic structure changes when it catches an electron. It happens this way because of the confinement of the electrons which is too big and the inclusion of a new electron causes huge forces of repulsion. You can take advantage of this change of the levels so the quantum dot works as a transistor of one only electron (SET, single electron transistor). In these devices the current that circulates through the transistor is “quantified”, because it flows from electron to electron. You can say that electronics has reached an incredible sophistication, dominating the behavior of the electron almost at will. Based in the same phenomenon, the quantum dots are used to storage information (which is why it is also called “qubit” of the expression “quantum bit”). These qubits will allow developing cryptography and quantic computing, being part of quantum computers, holders of a huge capacity that we will be able to use to make unimaginable calculus.

The use of quantum dots in the designing and development of photovoltaic cells is not a new idea. Until the date it hasn’t been able to achieve that these devices work with high levels of efficiency in their process of transforming sunlight into electric energy. Now, it is expected that thanks to a new design made by the researchers of MIT (Massachusetts Institute of Technology), with the incrustation of this quantum dots in a bundle of nanowires, this technology gives the final step.

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