TRANSIENT CHARGING CURRENT IN NEMATIC LIQUID-CRYSTALS

Transient charging currents in nematic liquid crystals have been measured with a single- and a double-voltage pulse technique to elucidate the role of impurity ions incorporated in the materials in the transient charging processes. In the single pulse experiment, a peak in the current transient is observed in the nematic phase. It is shown that occurrence of the peak is due to the alignment of the director of the liquid crystal molecules in the direction of applied electric field. In the double pulse experiment, a voltage pulse (prepulse) is applied to the liquid crystal before the measurement of the transient current. It is observed that the application of the prepulse significantly alters the shape of the current. The changes in the current can be explained by considering the impurity ion distribution, modified by the prepulse, in the nematic liquid crystals. It is concluded that the double pulse experiment is a powerful tool for the examination of the influence of impurity ions in liquid crystals on the current transients.