Nanometer scale switche

This experiment confirmed the fact that photochromic materials are beginning to find a broad range of applications that goes beyond their familiar use in sunglasses, windows, and other everyday devices. As researchers develop abetter understanding of the fundamental principles involved in the way photochromic materials operate, advanced applications in molecular switches, nanocomputers, and other nanometer-scale devices are likely to become much more common. 

Nanocomposites in the form of superlattice structures have been fabricated with metallic, " semiconductor,and ceramic materials " " for semiconductor-based devices. " The material is abruptly modulated with respect to composition and/or structure. Semiconductor superlattice devices are usually multiple quantum structures, in which nanometer-scale layers of a lower band gap material such as GaAs are sandwiched between layers of a larger band gap material such as GaAlAs. " Quantum effects such as enhanced carrier mobility (two-dimensional electron gas) and bound states in the optical absorption spectrum, and nonlinear optical effects, such as intensity-dependent refractive indices, have been observed in nanomodulated semiconductor multiple quantum wells. " Examples of devices based on these structures include fast optical switches, high electron mobility transistors, and quantum well lasers. " Room-temperature electrochemical... 

The first oxidation-reduction V " " V is completely reversible in bulk solutions as well as immobilized on various surfaces. The redox-active unit has been incorporated as a backbone component in self-assembled monolayers [289-292], or in a nanometer scale electronic switch [293] and various functional materials [294,295]. For a detailed characterization of the macroscopic electrochemical and structure properties of the various viologen-type adlayers on solid electrodes we refer to [231,296] and the literature cited therein. 

Fig. 1.18 A SEM image composed of a nanometer-scale molecular switch crossbar circuit.

Conventional photonic components are at the micrometer scale, while electronic elements have reached the nanometer scale in size. Nanoscale photonic circuits due to size-compatibility are crucial. Plasmonic switch is a novel example which takes the advantage of resonance coupling between single gold nanorods and photochromic dye molecules, and by controlling the plasmon resonance properties of the gold nanorods, the objective of a Plasmonic switch is achieved [29]. 

A polyaniline nanojunction switch has been bricated by creating a bridge across gaps between nanometer scale polyaniline electrodes. When briging is indicated by a short circuit, the junction can be characterized as a function of applied potential. Abrupt switching fi om insulator to conductor is seen at about 0.15 V vs Ag/AgCl that is explained on the bases of st changes in domains of strands (35). 

One area that is surely set to benefit from research aimed at developing the self-assembly of mechanical systems is molecular electronics. Initially, one can look with considerable interest towards the development of chemical sensors and molecular switches of a quite novel design. Furthermore, the ability to store and manipulate information at a molecular level and on the nanometer-scale is clearly on the horizon. It will open the way for the development of molecular electronics and, ultimately perhaps, the molecular-scale computer. The objective at present is to be able to control die assembly, the form, and the function of synthetic nanometer-scale structures with the same degree of precision that is displayed by nature, so as to make it possible to achieve these ambitious goals. Only now are chemists beginning to learn how to construct molecular assemblies and supramolecular arrays such that information might ultimately be written into them, processed by them, stored in them, and eventually read back out of them. 

The greatest progress has been made in the research of the components that may make up nanoelectronics. Researchers have been able to fabricate molecules that have two states, such that the molecules can be switched on and off . Some of these molecules have shown the functionality of diodes or variable resistors. Scientists have also been able to fabricate silicon nanowires and carbon nanomaterials such as one-dimensional (ID) carbon nanotubes (CNT) or two-dimensional (2D) graphene layers. Both of these technologies can be used as wires or devices, and in some cases both. Nanoimprint lithography, probably the most promising wire fabrication technique, has been used to produce working memories on the nanometer scale. While all of these... 

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