Molecular reorientation processes and dynamics of polarization reversal in thin surface stabilized ferroelectric liquid crystal dobambc

Abstract

Molecular reorientation processes in thin (3 μm) surface stabilized ferroelectric liquid crystal (SSFLC) DOBAMBC have been studied by applying symmetric and asymmetric triangular voltage pulses. For symmetric (-5V-OV-+5 V) triangular pulse a non-linear behaviour and two peaks of polarization reversal current and for asymmetric [(+ or -) 10 V-0 V] pulse four peaks of polarization change near 0 V region have been observed. For symmetric pulse two peaks originate due to composite effect of molecular change initially in the bulk and then at the surface under the influence of depolarization field. The non-linear current response to a linearly varying triangular pulse have been qualitatively explained by considering an intrinsic depolarization field. Dynamics of polarization reversal amongst the two uniform states and also amongst the twisted intermediate state to either of the two uniform states have been studied by applying symmetric and asymmetric square wave pulses. Switching response time corresponding to the change amongst uniform states have an intermediate value between the rise and decay time for the changes from twisted intermediate to uniform state and for the uniform state to twisted intermediate state. The switching amongst the two stable states takes place without actually attaining the twisted intermediate state of FLC.