Relaxation processes and charge transport across liquid crystal-electrode interface

At U<1 V nearly the entire voltage in liquid crystals (LC) and in solutions of dyes in LC is applied to the near-electrode regions. In this range of voltages, the Schottky emission through a dielectric layer is the electric current flow mechanism transport. A thin (several nanometres) dielectric layer is formed through adsorption on the electrode of not only ions, but also neutral impurities. According to estimates, the concentration of such molecules in pure LC may much exceed that of ions. It is demonstrated experimentally that the barrier controlling the charge transport lies at the anode and characterizes the ionization of LC molecules. Similarities and distinctions between the observed tunnel charge transport in dielectric liquids and the Schottky effect in solids are analysed. It is shown that the low-frequency dielectric dispersion is caused by voltage redistribution. Comparison of the parameters characterizing the carrier transport with those of the relaxation processes in the diffusion region of the electric double layer shows that long-term near-electrode processes are controlled by charge transport across the electrode-LC interface. (author)