PR-TRMC technique

Measured with the pulse-radiolysis time-resolved microwave conductivity (PR-TRMC) technique... 

In addition to the scavenged hydrocarbon systems, geminate decay kinetics were also studied in pure CCl for which a comparison was made between the decay kinetics observed using the TRMC technique with that found using a DC method. This comparison further substantiated the potential of the PR-TRMC technique for carrying out non-perturbative studies of short-lived, dipolar states. This potential would be extensively applied in later studies of molecular excited states using the flash-photolysis TRMC technique. 

The relaxation times of frozen aqueous media are however sufficiently far removed from the microwave region that application of the PR-TRMC technique to low temperature aqueous systems is possible. 

The possible application of the PR-TRMC technique to the study of thin semiconductor films was illustrated by results obtained on 0.9 micron thick layers of amorphous silicon on glass.These results yielded an electron mobility of 1.5 cm /Vs in good agreement with values determined... 

An interesting aspect of the work on UHMW polyethylene was the possibility of studying the anisotropy of the conductivity since aligned samples of stretch-oriented fibers could be produced and the effect of fiber orientation investigated. These experiments showed charge transport to be favored by a factor of approximately 20 along the direction of the oriented fibers compared with perpendicular to the fibers. This represented the first measurement of anisotropic conduction using the PR-TRMC technique. 

Fig. 1. Backbone structures of some of the conjugated polymers investigated as bulk solids and in dilute solution using the PR-TRMC technique. The position of the solubilizing hydrocarbon substituents is indicated by R.

The most extensive series of experiments using the PR-TRMC technique in recent years has been directed towards an understanding of the charge transport properties of discotic materials. In these materials the individual molecules, consisting of an aromatic core with several peripherally substituted alkyl chains, columnarly stack with the columns packed in a well-organized, two-dimensional lattice. The types of aromatic cores investigated are illustrated in Fig. 5. 

Fig. 5. The molecular structures of discotic cores investigated using the PR-TRMC technique with the position of peripheral hydrocarbon substituents indicated by R.

In the above we have illustrated the wide range of materials and physico-chemical processes to which the PR-TRMC technique has... 

Van de Craats et al. used the pulse-radiolysis time resolved microwave conductivity (PR-TRMC) technique to study the charge-transport properties of [ (Ci2H250)gPc 2Lu]. Their results showed an increase in charge carrier mobility at the crystalline solid to Col mesophase... 

TC/BG BC/BG SC/BG BC/TG PR-TRMC Top contact/bottom gate Bottom contact/bottom gate Sandwich contact/bottom gate Bottom contact/top gate Pulse-radiolysis time-resolved microwave conductivity technique... 

A separate development of the TRMC techniques was their application to the study of dipolar and excitonic species formed on flash-photolysis of dilute solutions and, more recently, to charge transport and charge separation in thin (aligned) solid films. In the present review we restrict ourselves to results that we have obtained on pulse-irradiated materials, for which the method has become known as the pulse-radiolysis time-resolved microwave conductivity or PR-TBAIC technique. 

It should be noted here that while TOF technique is widely used, there is another experimental method to measure conductivities and mobilities, namely pulse radiolysis-time resolved microwave conductivity (PR-TRMC) measurement as shown in Figure 11-8. 

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