Percolation conductivity

Lyden et al. [92] used in situ electrical impedance measurements to investigate the role of disorder in polysulfide PEC with electrodeposited, polycrystalline CdSe photoanodes. Their results were consistent with disorder-dominated percolation conduction and independent of any CdS formed on the anode surface (as verified by measurements in sulfide-free electrolyte). The source of the observed frequency dispersion was located at the polycrystalline electrode/electrolyte interface. 

S. Harrison, AC and DC Percolative conductivity of single wall carbon nanotube polymer composites,/. Potym.Sci. B, vol. 43, pp. 3273-3287, 2005. 

Due to their high aspect ratio, nanocarbons dispersed in a polymer matrix can form a percolating conductive network at very low volume fractions (< 0.1 %). The conductivity of a composite above the transition from an insulator can be described by the statistical percolation using an excluded volume model [22,23] to yield the following expression ... 

With the U-Type systems (i.e. with the low chain alcohols) the trends in the conductivity - curve are consistent with percolative conduction originally proposed to explain the behaviour of conductance of conductor-insulator composite materials (27). In the latter model, the effective conductivity is practically zero as long as the conductive volume fraction is smaller than a critical value called the percolation threshold, beyond which k suddenly takes a non-zero value and rapidly increases with increase of Under these conditions. 

CMP processes also leave a metallic contamination typically in the 10"-10 at/cm range. These contaminants arise from the outcropping metals, the slurries, and the mechanical environment of the polishers. In front-end applications (STI), these levels are prohibited because they are not compatible with the following hot processes. In the case of back-end steps, these parasitic metals must be removed as well, even if this seems more paradoxical with the use of metallization steps. Indeed a large amount of charges at the interconnection level or the presence of mobile ions such as sodium or potassium can induce disturbances during the electrical information transfer. Furthermore, a superficial conductive metallic contamination can generate shorts between two adjacent lines by percolation conduction mechanism. And last but not least, fast diffusers such as copper can reach... 

Lagourette, B., Peyrelasse, J., Boned, C., and Clausse, M. (1979), Percolative conduction in microemulsion type system, Nature, 281, 60-62. 

Application of percolation conduction model on thermoelectric composite material has been considered using simple numerical model. The possible thermoelectric property enhancement were illustrated on SiGe / PbTe composite and graded structure model. The model, however, does not include composite microstructure geometry explicitly, so far. 

Crystallochemically, it is to be expected that Zn+2 can readily substitute for Cu+2, although some local lattice contraction is to be expected. Currently, it is considered that the square pyramidal sites make a negligible contribution to the superconductivity on the grounds that the substitution of large moment rare earths in their proximity has no effect upon Tc other than that which can be ascribed to size (carrier density) effects (8). These zinc substitution effects support this point of view. Zinc substitutions will act as insulators in the two dimensional network due to the closed shell nature of Zn+2. Even if we assume that there is mixed valence on the plane, the introduction of 5% resistive elements would not be expected to significantly influence the percolation conductivity in this layer, since the percolation threshold is ten times this amount, or 50% in two dimensions (9). In the one dimensional chains, substitution of Zn+2 for the oxygen vacancy induced Cu+2 would result in a loss of charge carriers (carrier density) as well as a loss of delocalization in the chain. The former effect would lead to... 

Bridge, B. Theoretical modeling of the critical volume fiaction for percolation conductivity in Eberloaded conductive polymer composites. J. Mater. Sci. Lett. 1989, 8(2), 102-103. 

Mamunya, E.P., Davidenko, V.V, and Lebedev, E.V. (1995) Percolation conductivity of polymer composites filled with dispersed conductive filler. Polym. Compos., 16, 319-324. 

In the following, after a brief account of the data available in the literature as concerns microemulsion conductive and dielectric properties, results will be reported and analyzed that show how structural transitions in the transparent isotropic water-inoil solubilization area can be put into evidence by means of conductometry and dielectrometry. Mention will be made also of the occurrence, in certain w/o microemulsion systems, of percolative conduction phenomena (30) that appear to depend upon the nature of the alcohol used as the cosurfactant, for a given hydrocarbon (31). 

PMMA, PPy, ethyl cellulose (EC)) (sensing material) Black carbon—percolation conductivity... 

Du F, Fischer J E and Winey K I (2005) Effect of nanotube alignment on percolation conductivity in carbon nanotube/polymer composites, Phys Rev B 72 121404. 

A.N. Maitra, C. Mathew, and M. Varshney 1990 Closed and open structure aggregates in microemulsion and mechanism of percolation conduction, J. Phys. Chem. 94, 5290-5292. 

M. Sahimi, B.D. Hughes, L.E. Scriven, and H.T. Davis 1983 Critical exponent of percolation conductivity by finite-size scaling, J. Phys. Chem. Solid Stat. Phys. 16, 2521-2527. 

Percolation phenomena have also been observed in the case of drug-incorporated nonionic microemulsion system. Electric conductivity has been measured as a function of water content ca for the oleic acid (oil), surfactant (Tween 80/ cosurfactant(ethanol) mixture and variation of <7 as a function of (O has been observed (Figure 3.5A). The behavior exhibits profile characteristic of percolative conductivity [33-38]. The conductivity is initially low in an oil-surfactant nuxture but increases with increase in aqueous phase. The low conductivity below cd suggests that the reverse droplets are discrete (isolated droplets in a nonconducting oleic medium, forming w/o microemulsion) and have little interaction. When the water content is raised above the value of <7 increases linearly and steeply up... 

Maitra, A., Mathew, C., and Varshney, M. (1990). Closed and open structure aggregates in microemulsions and mechanism of percolative conduction. J Phys Chem 94, 5290-5292. 

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