Frequency-dependent capacitance-voltage hysteresis in ferroelectric liquid crystals: An effect of the frequency dependence of dielectric biaxiality

摘要

Using the concept of the Preisach model for a ferroelectric capacitor, we have analyzed the behavior of frequency (f)-dependent polarization reversal in surface-stabilized ferroelectric liquid crystals (SSFLCs) under an external field. At a fixed temperature, the peak height of the capacitance-voltage hysteresis loop is found to be decreasing with an increasing number of polarization cycles up to a certain typical value of frequency (e.g., f_c) being different for different ferroelectric liquid crystals (FLCs). We also observed an inversion (a well instead of a peak) in the hysteresis loops appearing above a typical higher frequency denoted f_i. The values of capacitance of the FLC capacitors became almost independent of the voltage for the frequencies between f_c and f_i. The frequency dependence of dielectric biaxiality in the SSFLCs is directly attributed to the appearance of such behavior.