Electronic junction transport

Molecular Electronic Junction Transport Some Pathways and Some Ideas... 

Me Creery RL (2009) Electron transport and redox reactions in molecular electronic junctions. Chem Phys Chem 10 2387-2391... 

Thieblemont F, Seitz O, Vilan A, Cohen FI, Salomon E, Kahn A, Cahen D (2008) Electronic current transport through molecular monolayers comparison between Hg/alkoxy and alkyl monolayer/Si(100) junctions. Adv Mater 20 3931-3936... 

In an electrochemical context, the situation is somewhat simplified since the value of Ef for an electrode surface can be controlled (with the aid of a stable reference electrode and an electrical double layer, which serves to screen electrons that reside in the electrode such that the energy level of a molecular orbital in solution is not impacted by the applied potential). Thus, in electrochemical studies, the value of 4> can be reduced to zero, enabling electrons to be removed from the HOMO orbital of solution-based molecules (oxidation), or to be added to the LUMO orbital (reduction). However, in the context of a solid-state molecular electronic junction, the value of a nonresonant interfacial barrier remains essentially static at different voltages. We discuss some of the reasons in more detail below that it cannot be assumed that their energy levels in a completed junction are set by the properties of the individual, isolated components. In any case, the presence of an interfacial barrier in a solid-state junction is a critical parameter in determining the electron transport properties of the device, regardless of the specific mechanism in operation. Thus, the appearance of Figure 10.12 needs to be taken in the context of the specific mechanism(s) under study. 

Charge transport in molecular electronic junctions compression of the molecular tunnel barrier in the strong coupling regime. Proc. Natl. Acad. Sci. U.S.A., 109, 11498-11503. 

McCreery, R., Wu, J., and Kalakodimi, R. J. 2006 Electron transport and redox reactions in carbon based molecular electronic junctions. Phys. Chem. Chem. Phys. 8 2572-2590. 

The bipolar junction transistor (BIT) consists of tliree layers doped n-p-n or p-n-p tliat constitute tire emitter, base and collector, respectively. This stmcture can be considered as two back-to-back p-n junctions. Under nonnal operation, tire emitter-base junction is forward biased to inject minority carriers into tire base region. For example, tire n type emitter injects electrons into a p type base. The electrons in tire base, now minority carriers, diffuse tlirough tire base layer. The base-collector junction is reverse biased and its electric field sweeps tire carriers diffusing tlirough tlie base into tlie collector. The BIT operates by transport of minority carriers, but botli electrons and holes contribute to tlie overall current. 

When electrons are injected as minority carriers into a -type semiconductor they may diffuse, drift, or disappear. That is, their electrical behavior is determined by diffusion in concentration gradients, drift in electric fields (potential gradients), or disappearance through recombination with majority carrier holes. Thus, the transport behavior of minority carriers can be described by a continuity equation. To derive the p—n junction equation, steady-state is assumed, so that = 0, and a neutral region outside the depletion region is assumed, so that the electric field is zero. Under these circumstances,... 

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