Radiation-Induced Conductivity in Polymers: Poly-N-Vinylcarbazoie

Experimental evidence is given which indicates that the yield of charge carriers excited by a given dose of x-rays in thin films of poly-N-vinylcarbazole (PVK) is dominated by geminate (initial) recombination of the ion pairs. The yield as a function of applied field gives a very good fit to the theory of initial recombination developed for gases by Onsager. Two competing mechanisms, the Poole-Frenkel effect and track recombination, may be rejected on the basis of the field dependence. A comparison of the charge transients in PVK with other organic materials is given along with a discussion of the possibility of trap modulation of the mobility in PVK. The role of three different kinds of carrier recombination, bulk, track and geminate, is described in terms of the experimental results expected for each of them.