Quantum Dots Essay

QUANTUM DOTS

Essay 1 Chemistry and Society (2012/2013) Z0937341

1. INTRODUCTION: REVOLUTION.

THE

NANOTECHNOLOGY

Nanotechnology refers, in general terms, the control of matter on the atomic and molecular scale (from 1 to 100 nm) in applied science and technology. It also refers to the manufacture of such devices nanometer size. Therefore it part from design and characterization, toproduction and application of these nanoscale components. It is considered interdisciplinary, so it is usual scientific collaboration among researchers from different disciplines, such as Physics, Chemistry, Engineering, Biochemistry, and Medicine, among others. Economy Analysts observe the revolutionary role that nanotechnology can have in the future, and they consider the nanotechnology likethe future strategic piece key to competitiveness of an economic system. The growth is estimated in the market up 3.7 billion dollars by 2015. 1 Nanomaterial is known as a material that at least one of their dimensions below 100 nm. So they are divided into three types of nanomaterials according to the number of nanoscale dimensions: layer, with one nanometer dimension, nanowire with two nanoscaledimensions, or quantum dot with its three dimensions with the three nanometers dimensions. The interesting properties of these nanomaterials are mainly two: increased relative surface area and quantum effects. These two properties affect the magnetic, optical and electrical properties of nanomaterials. I did a research project in Spain last year on this topic. I worked making Langmuir-Blodgettmonolayers within the research group Platón. I really enjoyed working as a highly topical area. This year I am working in the research group of Professor Paul Low, synthesizing new molecules that serve to fabricate Langmuir-Blodgett layers.

2. QUANTUM DOTS
Society demands ever smaller electronic devices and better than today. It is the investigation of quantum dots in this lawsuit, in themanufacture of electronic devices (quantum computing, single electron transistors ..) and optoelectronic (fotodetectores..).
2, 3

The research of semiconductor nanostructures started in the decade of 1960. Superlattices start to build during the 70s. Research has to wait until the technology is developed. In 1982 Arakawa and Sakaki suggested dimensional confinement structures used to improvesemiconductor lasers. 4. In 1992 D. Leonard with growing the first sample of quantum dots those are free of defects. He used the technique of Molecular Beam Epitaxy (MBE). 5

The reduction of the three-dimensional space to values nanoscale (quantum dots), leads to charge localization in these dimensions. therefore it discarded the classical model of band structure. Small changes in the size ofnanomaterials cause profound changes in material properties. Because of this, the homogeneity of the devices must be extreme for the proper functioning of the devices. 2 As other nanomaterials, most of the atoms on its surface, so that the surface to volume ratio of the quantum dots is very high, which, next to the quantum confinement influences their properties are very different from macroscopicmaterials. The quantum confinement occurs when electrons are constrained to move in a very small region, as is the case of the quantum dots less than 10 nm. This effect causes the electronic and optical properties of quantum dots are determined by their size. A semiconductor has a band full of energetic electrons (valence band) and an empty energy band (conduction band) separated by an energy gap(bandgap). This energy difference is greater than for a less conductive material and that an insulating material. A luminescence process basically consists in the excitation of an electron from the valence band to the conduction band and the return of the electron from the valence band to the subsequent emission of a photon with energy equal to the bandgap. As in the bandgap quantum dots varies with the...