Insulation metal interaction

Since the discovery of the first organic conductors based on TTF, [TTF]C1 in 1972 [38] and TTF - TCNQ in 1973 [39], TTF has been the elementary building block of hundreds of conducting salts [40] (1) charge-transfer salts if an electron acceptor such as TCNQ is used, and (2) cation radical salts when an innocent anion is introduced by electrocrystallization [41]. In both cases, a mixed-valence state of the TTF is required to allow for a metallic conductivity (Scheme 5), as the fully oxidized salts of TTF+ cation radicals most often either behave as Mott insulators (weakly interacting spins) or associate into... 

The electrons in a solid interact both with one another and with the lattice vibrations. A theme of this book is the effect of the interaction between electrons in inducing magnetic moments and metal-insulator transitions. Interaction with phonons also has an important effect, particularly in some transitional-metal oxides. In this chapter both kinds of interaction are introduced. 

In the case of conventional (i.e. non-superconductive) metals, the inter pretation of the results of experimental studies on electron tunneling through the "metal-insulator metal junction becomes possible within the framework of the simplest model of non-interacting electrons. Here, the interaction between electrons and between electrons and phonons both inside the barrier and in the bulk of metals are neglected. 

Interestingly also the electron-hole interaction can scale with such a distance law. The pre-melting corresponds then to what is called level narrowing,90 and the transition to a superionic state (degenerate situation) corresponds to the insulator-metal transition expected in such a case. 

We have described how a molecule which has an internal electronic asymmetry should exhibit rectifying properties. However, since we are interested in current flow rather than simply charge separation within the molecule, we must characterize the molecule as part of a circuit. It is important to realize that the measurements being made are of the junction as a whole rather than just the molecular properties. That is to say, the electrical response is a convolution of the molecular properties, the external circuit and, in particular, the contacts between the molecule and the electrodes. The interactions at the interfaces are responsible for many of the effeets that are observed in metal-insulator-metal devices. 

Winkler and Mayer (420) have attempted to prepare derivatives of the type IrL(CO)2(Cl) which contain highly polarizable ligands, L — 9,10, and 11, in an attempt to experimentally realize Little s excitonic superconductor (268, 269, 429). These materials, [IrL(CO)2Cl] (L = 9-11), were shown via two-probe measurements on pressed pellets to have conductivities in the range of insulators, metal-metal interaction in the solid state because the ligands used were are bulky and hinder close approach. In addition, the single crystal conductivities of Ir(CO)2(PrNH2)X (X = Cl, Br, I) have been measured as 0.2-10 x 10 cm i(24,313,314), while Ir(CO)2-Cl(p-toluidine) has a conductivity of 10 Q cm (313, 314). 

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