Unimolecular electronic device

Use of heterocycles, in particular tetrathiafulvalenes andpyridinium zwitterions, in unimolecular electronic devices 99ACR950. 

Keywords Bottom-up Carbon nanomaterials Molecular conductance Molecular electronics Unimolecular electronic devices... 

For now, unimolecular electronic devices must be tested with inorganic electrodes, thinned out to atomic or oligoatomic sharp tips. Molecules either singly, or in parallel as a monolayer array (one molecule thick), have been shown to be either passive or active electronic components. There are two ways to connect a molecule to an inorganic metal electrode physisorption, and chemisorption. 

Tungsten nitride shows extreme hardness, high chemical stability and high electrical conductivity [172]. The compound is a promising candidate for diffusion barriers and gate electrodes in electronic devices [173-175]. This material has been prepared by the CVD of a mixture of tungsten hexachloride, NH3 and H2 at 500-900 °C [172], from a mixture of WF6/NH3/H2 at 450-650°C [176] and from the unimolecular precursor (t-BuN)2 V(NH-/-Bu)2 at 450-650°C ]177]. 

Metzger R.M. Electrical rectification by a molecule The advent of unimolecular electronic devices. Acc. Chem. Res. 1999, 32. 950-957. 

HOW TO CONNECT TO A UNIMOLECULAR ELECTRONIC DEVICE Proposed Molecular Wires... 

In principle, molecules can be either passive or active electronic components, either singly or in parallel as a one-molecule-thick monolayer array. This may lead to electronic devices with dimensions of 1-3 nm. Unimolecular electronics (UE) or molecular electronics sensu stricto, or molecular-scale electronics evolved from studies of organic crystalline metals, superconductors, and conducting polymers the idea is to exploit the electronic energy levels of a single molecule, and most importantly its HOMO (highest occupied molecular orbital) and LUMO (lowest unoccupied molecular orbital), which can be tuned, or modified by incorporation of electron-donating... 

R. M. Metzger, Unimolecular electronic devices, in Intelligent Materials, eds. M. Shahinpoor and H. J. Schneider, Royal Society of Chemistry Publishing, Cambridge, UK, 2008, pp. 205-230. 

R. M. MetzgCT and D. L. Matton, Unimolecular electronic devices, in Unimolecular and Supramolecular Electronics, ed. R. M. MetzgCT, Springer Topics in Current Chemistry, Springer, Bra-Un Heidelberg, New York, in press. 

Metzger RM (1991) Prospects for truly unimolecular devices. In Metzger RM, Day P, Papavassiliou GC (eds) Lower-dimensional systems and molecular electronics. NATO ASI Series B248. Plenum press, New York, pp 659-666... 

The carry-home messages are as follows (1) The difference (Id — Aa) is important and, to first order, should be minimized (2) in a device and under bias, (Ip — Aa) becomes smaller than in the gas phase (3) if (fD — Aa) is too large, then the rate of electron transfer may become unacceptably slow because of the Franck-Condon factor becoming small It is a waste of time to make super-small but super-slow unimolecular devices. 

---