Conduction Sheng Model

Figure 3.12 illustrates the Sheng model explaining the interruption (barriers) between highly conducting areas. 

Where Tq and are known as Mott parameters and depend on the type of counterion used. To understand the conduction mechanism below 100 K, the Sheng model can be applied to the analysis of the temperature dependence of polypyrrole conductivity [234]. This model takes into consideration both hopping and... 

Neither of the above theories takes the macrostructure of carbon black into account in any quantitative way, although in practice this is crucial in selecting a material for a particular application. Sheng (1980) was, however, able to develop the first of these theories and extend its range of applicability. He noted the well-established model for hopping conduction by tunnelling... 

Figure 3.12. Sheng s model considers the effect of fluctuation-induced tunneling through potential barriers between extended highly conducting regions. In a model circuit the barriers can be treated as capacitances with charging resistances [22b].

A model on a different basis more in consideration of CPs was proposed by Sheng [178], found to apply to highly doped CPs. It assumes conduction between the "metallic islands" within CPs discussed above, and yields the following temperature relation ... 

Delineate the salient points of each of the following conduction models Mott VRH Sheng Paasch Kivelson electronic. Identify which temperature and doping ranges each model is most correctly applicable to. 

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