Conduction mechanism films

Manometric and volumetric methods (kinetics) Thermogravimetry (kinetics from very thin films to thick scales stoichiometry) Electrical conductivity of oxides and allied methods (defect structures conduction mechanisms transport numbers) Radioactive tracers and allied methods (kinetics self diffusion markers)... 

Diaz and colleagues (1979) sought to identify the nature of the conduction mechanism by performing a range of ex situ experiments on the free-standing, as-grown film. They measured the conductivity, er, of the film as a function of temperature and found that it varies as ... 

The work of Christensen and Hamnett (1991) provided the first positive evidence for bipolarons and showed, for the first time, that the oxidation of polypyrrole was accompanied by a dramatic decrease in the film thickness, linking this with the generation of these carriers. Taken in addition to all the work discussed above their work provided some of the final pieces in a workable theory of the conduction mechanism in polypyrrole. 

H.S. Kwok, X.W. Sun, and D.H. Kim, Pulsed laser deposited crystalline ultrathin indium tin oxide films and their conduction mechanisms, Thin Solid Films, 335 299-302, 1998. 

Another conductivity mechanism could be suggested for LB films of this polymer with Ag+ cations. Such cations can accept or release electrons easily, so in the layer of such cations the conductivity could be caused by electron transitions between the ions with different degrees of oxidation. With tunneling microscopy an anomaly in the dl/dV(V) curves near zero bias was discovered for the LB films in Ag form with an odd number of layers there was a conductivity peak some 150-200 mV wide (Figure 7.4, Curves 1, 3) but no anomaly for these same films with an even number of layers (Figure 7.4, Curve 2). For LB films with an odd number of layers the ordered superstructure of the scale 11.5 x 11.5 x lO cm has been found in a conductivity dl/dV (x,y) measurement regime. The scale of such a structure corresponds to 3 x 2 surface reconstruction (Figure 7.5). 

There are five possible physical phases in the current path in which the current conduction mechanisms are different as illustrated in Figure 19. They are substrate, space charge layer, Helmholtz layer, surface oxide film, and electrolyte. The overall change in the applied potential due to a change of current density in the current path is the sum of the potential drops in these phases ... 

Asahi Chemical Industry carried out an exploratory investigation to determine the requirements for cellulose based separators for lithium-ion batteries. In an attempt to obtain an acceptable balance of lithium-ion conductivity, mechanical strength, and resistance to pinhole formation, they fabricated a composite separator (39—85 /cellulosic fibers (diameter 0.5—5.0 /pore diameter 10—200 nm) film. The fibers can reduce the possibility of separator meltdown under exposure to heat generated by overcharging or internal short-circuiting. The resistance of these films was equal to or lower than the conventional polyolefin-based microporous separators. The long-term cycling performance was also very comparable. 

Polypyrrole has the potential to provide an effective method for reagentless transduction by immobilization of the ssDNA probe within the polymer matrix. Significant differences in the impedance profile of ssDNA and dsDNA have been demonstrated [59]. The differences in the impedance profile are purportedly based on intercalation differences of the polymer with ssDNA compared to dsDNA. The exact mechanism for impedimetric change resulting from conducting polymer films has not been identified, although it is likely linked, much like the impedimetric response of pure DNA, to the change in ion density that accompanies the double strand compared to the... 

Sato K, Yamaura M, Hagiwara T, Murata K, Tokumoto M (1991) Study on the electrical conduction mechanism of polypyrrole films. Synth Met 40 35 8... 

The resistivity of the films increased from 10 O-cm for very low Cd content to a maximum of ca. 10 U-cm at 6% Cd and then slowly dropped again with increasing Cd. This maximum correlates with the minimum crystal size, suggesting a dominant role of grain boundaries in the conduction mechanism. The spectral response of the photoconductivity blue-shifted with increase Cd content up to a peak response at 1.35 p,m for 8.4% Cd. 

Pyrolyzed polyimide films at 480-530 °C can change the conductivity from 10-18 to 10 2 Scm-1 and mobility from 10-11 to 10 7m 2 V-1 s 1 (Fig. 55) [318], It has been shown that carrier density increases at the initial stage of the pyrolysis and then the increase of the mobility becomes predominant as the pyrolysis progresses. Hopping charge transfer is the main conductive mechanism. 

Dc conductivity erac as a function of reciprocal temperature for the spin-coated film of compound 8 in Fig. 2 was found tobe2.60x 10-12 and 1.80x 10-8 S/cmat room temperature and 425 K, respectively. It was seen from the Arrhenius plot that there is more than one slope in the conductivity, which indicates the presence of different levels in the film for the conduction mechanism [41], The activation energies obtained for the low and high temperature regions were found to be 0.36 and 1.02 eV,... 

The conductivity measurements of the films of 39, 40, 39a, and 40a in Fig. 10, which were carried out in the temperature range 290 176 K, suggested the presence of only one conduction mechanism. The conduction behavior of 39 and 40 could be interpreted as the usual Arrhenius type. It was observed that the insertion of alkali metals increased the dc conductivity. The order of conductivities observed for these... 

B. Conductance Mechanisms in Surface Films on Active Metal Electrodes... 

For a classical SEI electrode such as lithium, the surface films formed on it in most of the commonly used polar aprotic systems conduct Li ions, with a transference number (t+) close to unity. As stated earlier the surface films on active metals are reduction products of atmospheric and solution species by the active metal. Hence, these layers comprise ionic species that are inorganic and/or organic salts of the active metal. Conducting mechanisms in solid state ionics have been dealt with thoroughly in the past [36-44], Conductance in solid ionics is based on defects in the medium s lattice. Figure 8 illustrates the two common defects in ionic lattices interstitial (Frenkel-type) defects [37] and hole (Schottky-type) defects [38],... 

There are two general interpretations for the admittance characteristics of barrier anodic films (98). The first interpretation is based on film conduction mechanisms, either electronic or ionic, and the influence of solution ions on the oxide film lattice defect structure on conduction behavior. The second is based on the behavior of preexisting defects in anodic films and the effects of attacking or passivating solutions. 

Organic conductors could be categorized in terms of the conduction mechanism. One-dimensional conductors seem to be sensitive to defects and disorders and become insulators at low temperatures due to the metal-insulator transitions even when the materials are metals at room temperature. On the other hand, more-than-one-dimensional conductors seem to be relatively insensitive to defects and disorders. Superconductors are found in this class of compounds. Taking the foregoing features into account, more-than-one-dimensional conductors have an advantage over one-dimensional conductors when they are to be used as the active elements of the conductive LB films. Actually, the active parts of the two metallic LB films belong to the more-than-one-dimensional conductors. 

Several kinds of conduction mechanisms are operative in ceramic thermistors, resistors, varistors, and chemical sensors. Negative temperature coefficient (NTC) thermistors make use of the semiconducting properties of heavily doped transition metal oxides such as tf-type Fe2 Ty03 and type Ni1 LyO. Thick film resistors are also made from transition-metal oxide solid solutions. Glass-bonded By 2 Pb2yRu207 having the pyrochlore [12174-36-6] structure is typical. 

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