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Activated hopping process

In relation to this problem is the fact that as the top of a band is approached the effective mass of a carrier changes and the range of allowed k values is small. Thus, the mobility of a carrier either in a narrow band conductor or at the top of an almost filled band must inevitably be small (9). In these cases it is probably not correct to assume the mass of the carrier and an electron to be the same. Under some circumstances the transfer of charge in a narrow band semiconductor is better described as an activated hopping process. [Pg.323]

Except for these relatively few materials, most transition metal complexes exhibit properties more typical of semiconductors with conductivities usually less than 10" ohm" cm and a thermally activated conductivity behavior. The thermal activation energy, which is derived from plots of log charge carriers (as for example by direct band gap excitation in an intrinsic semiconductor) or from the carrier motion (as in systems where the conduction proceeds by a short range, thermally activated, hopping process). [Pg.3]

This is not sufficient, however. In several cases of practical interest, charge transport has the characteristics of a thermally activated hopping process the importance of the diffusion of localized (soliton or polaron) states is elusive and band conduction seems to be an idealization. The description of transport phenomena in polymer materials will therefore require a thorough characterization of the structure in both crystalline and disordered ( amorphous ) regions, and a detailed picture of how these are dispersed and interconnected. [Pg.77]

Mixed oxides of Ru" and are frequently metallic as are RuOj and Ir02-The more localized electron behavior observed when these cations are located in the pyrochlore structure is presumably due to structural considerations. The M-O-M bond angle in pyrochlores is not the most favorable for delocalization of t2g electrons. The most favorable angle would be 180°, whereas this angle tends to be about 130° in the pyrochlore structure. This is a significant deviation from 180° and is therefore presumably adequate to cause an activated hopping process in the absence of mixing with post-transition metal s or p bands. [Pg.237]

The dependence of the dc conductivities and the parameters derived thereof show that there are distinct differences between the ion dynamics in PDADMAC-rich and PSS-rich PEC. In both cases, however, the Arrhenius dependence of clearly shows that the ion dynamics in PEC materials is determined by the thermally activated hopping processes of the mobile ions. The fact that the isothermal dc conductivity increases continuously with NaPSS content indicates that the chloride ions do not dominate the ion transport, even in PEC materials with an excess of polycations and thus Cl as the most abundant mobile charge carrier. Otherwise, aac as a function of x should pass through a minimum, which is obviously not seen experimentally. The conductivity measured for PEC with x < 0.50 could therefore be either due to residual Na ions or protons. To shed more light on this aspect, PEC in which the sodium ions were replaced by lithium or cesium ions were studied. These results are discussed in the following section. [Pg.111]

Although experiments on molecular glass formers have revealed that the dynamics very close to the transition point is dominated by thermally activated hopping processes, which the described (idealized) MCT cannot account for, MCT has been quite successful in describing the approach to glassy arrest in colloidal dispersions, as mentioned above. [Pg.139]


See other pages where Activated hopping process is mentioned: [Pg.132]    [Pg.116]    [Pg.221]    [Pg.379]    [Pg.14]    [Pg.44]    [Pg.1820]    [Pg.35]    [Pg.5]    [Pg.132]    [Pg.136]    [Pg.366]    [Pg.537]    [Pg.231]    [Pg.166]    [Pg.276]    [Pg.156]    [Pg.106]    [Pg.556]    [Pg.58]   
See also in sourсe #XX -- [ Pg.238 ]




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