Molecular electronics

Molecular electronics describes a further development of microelectronics, where the individual devices can be realized by making use of atomic interactions in molecules.

Definition

The definition of " molecular electronics" is so broad in many publications that additionally nanostructures such as carbon nanotubes (eg next to conjugated organic and inorganic molecules such as fullerenes (eg as electromechanical amplifiers) in the function transistors for logic circuits ), or one-dimensional crystalline metallic in the form of semiconductor nanowires (e.g., in the function of transistors, nano- sensors, and nano -emitting diode ) as a so-called " elements at the molecular scale, " can be included. With this convention ( see, for example ) is a classification under the term "molecular electronics" not the molecular character is decisive, but the mere fact that individual nanoscopic elements are present that serve individually as a functional unit. However, the source references and examples in the following overview are limited solely on references to organic molecules in order to clarify their possible uses for electronics.

Classification

Mono -molecular electronics

It is characteristic that each individual molecule acts as a functional element. The development of a mono- molecular electronics is in the context of the trend toward miniaturization in manufacturing electronic semiconductor systems and tracked in this framework, the goal of a highly miniaturized nano-electronics.

To the previously implemented monomolecular functional elements include, in particular molecular wires, switches (for example, as an information storage ), or molecular diodes, spin channels between quantum dots. As prominent techniques for contacting single molecules procedures apply, such as scanning probe microscopy, serve in the functionalized AFM tips or STM tips as a counter electrode, and the breaking points bridging (break junction) or the self-assembly of monolayers between two electrode layers.

Supramolecular electronics

It is characteristic that demarcated, non-covalent associations of molecules each act as individual functional unit. The strategy of self-assembly of molecules to conductive supramolecular units is often in the context of bottom- up approach for the generation of nanoelectronic structures and can be performed by different means. Among these approaches, one beside the direct self-assembly and the co -assembly, the hierarchical self-assembly or self-assembly of different molecules to a mechanically interlocked supramolecular unit.

Several prominent approaches for the generation of electronically active supramolecular units based on the formation of liquid crystals with a columnar phase, in which electrically conductive supramolecular columns ( columns ) can act as a single functional element principle. To these approaches include, for example, the self-assembly of functionalized hexabenzocoronene to conductive columns, which are proposed as isolated from each other supramolecular nanowires. Another approach pursues the generation supramolecular columns over the self-assembly of functionalized dendron molecules. This aromatic molecules in the core of the pillars ensure the mobility of charge carriers. Alternatively, a co -assembly can be achieved by dendron molecules functionalized with functionalized molecules, aromatic polymers such that on the donor-acceptor interactions, the polymer chains are incorporated in the center of the column. Unless they can be addressed independently - for a supramolecular electronics come (eg nanowires ) in question in both cases there is a conductive one-dimensional system, so that individual columns as elements.

An example of hierarchical self-assembly to form supramolecular units provides an approach that in the molecules consisting of two subunits - an oligomer as a semiconductor and a monomer as a coupling element - by hydrogen bonds between the coupling elements dimerize. These dimers in turn form through self-assembly helical columns which are in principle as supramolecular electronic functional elements. Approaches in which interlock mechanically different molecules, thereby forming an electronically active supramolecular structure, based for example on rotaxanes or catenanes. These supramolecular units - prototypes of artificial molecular machines - have the property to be effective as a single electro- mechanical switches - a property that can be used for logic functions or information storages for.