Radiation-induced trapping and charge transport in a smectic liquid crystal

We have studied changes in the hole transport properties of a smectic liquid crystalline semiconductor resulting from high-energy electron irradiation. The 'radiation doping' results in sharply increased shallow trap densities and the onset of nearly trap-limited hopping conduction. A simple semiquantitative model provides estimates of the trap lifetime and the irradiation energy required to create a single trap. Experimental techniques to overcome parasitic effects due to increased molecular ion densities in irradiated samples are also discussed