Hopping conductivity mechanism

The exchange frequency can be related to the "trial time in hopping" for a hopping conduction mechanism (29). 

Surface morphology and electrical conduction in laser beam deposited perylene based thin films were investigated. It is found that the peak-to-peak value of the surface relief significantly increases with an increase of the substrate temperature at the deposition. Measuring of electrical properties by cyclic thermal desorption method shows that the hopping conductivity mechanism is realized in the films. The conductivity is intrinsic or impurity depending on the concentration of the adsorbed oxygen. 

Different mechanisms have been invoked to give a rationale to the charge transport, mainly ascribable to hopping and tunneling phenomena [3, 60, 104-106]. To a first approximation, the Arrhenius equation holds for hopping conduction mechanism ... 

The data of Table 17 show the strong reaction enhancements of the specific catalysts impart under microwave heating to all of reactive systems examined. The gelation and vitrification times were lowered to one-eighth to one-tenth of those under hot-air heating with the same catalyst and its concentration. An ion-hopping conduction mechanism was recognized as the dominant source of the microwave absorption capacities of these catalysts [2]. 

Scheme XXXI. The chain-hopping conduction mechanism in PA.

Riihe et al. [721] electropolymerized various pyrroles substituted in the 3,4-position with a fused alkyl ring. Using four-probe ex situ conductivity measurements as a function of temperature, a decrease in conductivity with an increase in substituent size was found. The temperature dependence implied a variable range hopping conduction mechanism. 

In Greave s equation, conductivity is a function of temperature in terms of hopping conduction mechanism ... 

The introduction of ammonia impurities changed the sensor conductivity by 4-8 orders of magnitude due to the absence of bulk shunt resistance. The conductivity was found to be proportional to the square of ammonia impurity concentration and the 1-V curves of the films were logarithmic, which is typical for the hopping conduction mechanism. By changing the preparative conditions used to produce the films, sensors for the detection of ethanol and water vapors in air were also manufactured. 

Four peaks (a, P, y and 8) are assigned to the oxidised strnctnre, the aromatic form, the quinoid form, and the 2,3-bond structure, of polypyrrole, respectively. The half-width of peak y is a measure of electrical conductivity. Electrical conductivity measurements at room temperature and -23 °C show that the hopping conduction mechanism is the dominant one for polypyrrole. 

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