Anomalous capacitance bounces and bumps of liquid crystal cells in DC electric fields

Abstract

We have studied the time response of the capacitance of nematic liquid crystal cells by applying electric fields. When AC fields are applied, the capacitance exhibited a normal behavior: it first increased monotonically with time, and then reached a saturating value, With sufficient high DC fields, capacitance bounces and bumps were observed during the rising time for 100-mu m thick cells with low and high impurity concentrations, respectively. We believe that these anomalous capacitance characteristics of liquid crystal cells are resulted from the coupling effects between induced polarization from liquid crystal molecules and space-charge polarization from fast ions.