Disorder induced metals

When the doping level is sufficiently high, the electronic structure evolves to that of a metal. The metallic state and the role of disorder (the disorder-induced metal-insulator transition) are discussed in Section VI. 

Bowman and Mattes [65] also showed that the low-temperature (<30 K) transport properties indicate that the reduced activation energy had a positive temperature coefficient, which is indicative of this material lying on the metallic side of a disorder-induced metal-insulator phase boundary. The reduced activation energy for these stretched polyaniline fibers is shown in Figure 2.26. Since the slope is negative for all of the godet-stretched fibers, this indicates that these fibers are on the insulating side of the disorder-induced metal-insulator transition. This is in contrast to that observed for the unstretched polyaniline fiber, which lies on the metal side of the disorder-induced metal-insulator transition. 

Exciton binding energies comparable to the optical gap. Disorder. Dielectric screening of excitons from both solvation and dispersion interactions. Doped conjugated polymers exhibit conductivity close to a disorder-induced metal-insulator transition. Energy spectra are broadened. 9... 

III. RESULTS AND DISCUSSION A. Disorder-Induced Metal-Insulator Transition... 

Knowledge of the intracellular thermodynamics and kinetics of metal metabolism may become useful in the design of compounds that alter intracellular metal ion availability. This in turn may be useful in controlling such biological phenomena as cancer cell proliferation, disorders of metal metabolism, and metal-induced neurotoxicity. 

Motome, Y., Furukawa, N. Nagaosa, N. 2003 Competing orders and disorder-induced insulator to metal transition in manganites. Phys. Rev. Lett. 91,167204. (doi 10.1103/PhysRevLett.91.167204) Pai, G. V., Hassan, S. R., Krishnamurthy, H. R. Ramakrishnan, T. V. 2003 Zero-temperature insulator-metal transition in doped manganites. Europhys. Lett. 64, 696-702. (doi 10.1209/epl/ i2003-00282-0)... 

The most noticeable effect during the in situ Raman studies was the near complete disappearance of the disorder-induced D band after oxidation (Fig. 12.3c). These results show that for the DWCNT sample, the D band originates mainly from amorphous carbon present in the sample and not from defects in the wall structure of the nanotubes. While the concentration of defects probably increases during the oxidation, disordered carbon and the associated D band disappear completely. However, it is well known that only metallic CNTs contribute to the D band intensity [57]. Therefore, the absence of any Raman signal... 

Thus, the data obtained for metallic polymers indicate that they are disordered metals near the disorder-induced M-I transition. There is remarkable consistency between the conclusion obtained from transport studies and from IR reflectance measurements. 

As shown in Section VIC and VID, however, currently available metallic polymers are barely metallic their electronic properties are dominated by disorder with mean free paths close to the loffe-Regel criterion for disorder induced localization k l 1. 

Fournie GJ, Mas M, Cautain B, Savignac M, Subra JF, Pelletier L, Saoudi A, Lagrange D, Calise M, Druet P (2001) Induction of autoimmunity through bystander effects. Lessons from immunological disorders induced by heavy metals. J Autoimmun, 16 319-326. 

In summary, the conductivity and its temperature dependence in doped (CH), PPV, PPy, PANI and PEDOT samples suggests that by reducing the role of disorder-induced localisation in charge transport, it is possible to observe the intrinsic metallic positive TCR in doped conducting polymers. 

Inhomogeneous Disorder-Induced Insulator-Metal Transition Quantum Hopping in Metallic Polymers ... 

Anderson Disorder-Induced Insulator-Metal Transition... 

Typically, electrical conductivity of EAPs is measured in units of S/cm. Both two- and four-point probe techniques are used to measure a in films and pressed pellets (255). Conductivities as high as 10 S/cm have been reported for several EAPs. Values vary depending on synthetic procedures, fabrication techniques, and measurement methods. EAPs are typically only partially crystalline (256-258) amorphous EAPs have been reported (259-261). Therefore, disorder plays a significant role in their electrical conductivities, and the conductivity arises from the metal-insulator transition (262). As an example, PA with the highest conductivity reported so far shows temperature dependence of conductivity (263). Thus, electrical conductivity is limited by the disorder-induced localization of the electrons rather than by the intrinsic conductivity of the delocalized charges on the polymer backbone. Table 2 shows conductivities for several well-known EAPs (26-28). 

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