Paper charge transport

Motivated by the growing interest in high-order correlation functions, we develop in the present Paper a systematic approach to full statistics of charge transport in Andreev interferometers. We adopt several simplifying assumptions, which enables us to present an analytical solution for the CGF and, without a loss of generality, to clearly demonstrate essential features of coherent effects in the current statistics in NS structures. Our approach is based on the extended Keldysh-Green technique [13, 14], in which the CGF is determined by the equation... 

When charge transport fails to reach a steady state during the time available, the most likely reason is that the transit time is dominated by the time required to escape from the slowest site(s) that a carrier encounters as it crosses the sample. Furthermore, the distribution of release times is such that the carrier continues to encounter slower and slower sites as it crosses a sample. Transport under such conditions is called dispersive, and has been the subject of much study since a seminal paper by Scher and Montroll [73a-e]. The term dispersive alludes to the wide dispersion in release times and/or the fact that carriers that are injected simultaneously spread out, disperse, to an anomalous extent as they cross the sample. The literature has several examples of studies of this subject in amorphous molecular solids [66b, 73f-h]. Some materials undergo a transition from essentially dispersive transport at low temperatures to essentially nondispersive transport at higher temperatures, and this dispersive-to-nondispersive transition has been the subject of significant attention [73i-p]. 

An example of such a series of transient experiments for a sample of paper without conductive additives (softwood Kraft pulp, 450 CSF, 80 g/m2 basis weight, Sample 1), is shown in Fig. 16. This series of transient currents represents the electric field dependence of charge transport associated with mobile ions within the water associated with the fibrous network of the papor. The initial transient current, labeled (a), corresponds to the first application of an electric field (E = 2.5 x 103 Volts/cm) to the new sample. After reversing the polarity of the power supply an electric field of the same magnitude is applied to the sample which leads to the transient current shown by label (b) in Fig. 16. (N.B. the scale of the ordinate is different for... 

In summary, the results which are presented in this section suggest that the charge transport of ions within paper and paperlike structures is essentially the same as that of the transport properties associated with aqueous electrolyte systems. Furthermore, the transient current behaviour which has been observed in these fibrous cellulosic systems show characteristics similar to the ionic transient current conduction exhibited in both dielectric fluids and aqueous ionic systems. 

Hillman and Bruckenstein have used this type of analysis to discuss break-in effects, charge and mass trapping, structural evolution with redox cycling, kinetic decoupling of ion and solvent transfer, and variations in apparent charge transport rate and formal potential with experimental time scales. The reader is referred to the original paper for further details. 

The other aspect is related to the basic studies of the charge-transport processes and mechanisms in the molecular conductive materials. This is because fundamental transport properties such as mobility can be easily defined on these electronic devices. Optical processes can be appropriately dealt with similarly. In this section, we highlight the thin-film electronic devices of FETs and LEDs based on the oligothiophenes in relation to the devices using other organic materials. Details of the fabrication and action characteristics of the devices using those materials can be seen in recent papers and reports. 

A subsequent paper described the photoconductive characteristics of an inorganic-organic hybrid composite, in which PVK serves as a polymeric charge-transporting matrix, and in which QDs composed of surface-passivated cadmium sulfide serve as... 

The important topic of charge transport in organic materials is outside the scope of this chapter, and for that we refer the reader to excellent review papers and book chapters [7-11]. Suffice here to recall a few basic concepts that will help in dealing with the problem of interfaces. 

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