X-Ray and Optical Investigations of the Dislocation Domains in Ferroelectric Liquid Crystals

Abstract

In ferroelectric liquid crystals with high enough spontaneous polarization P s ≥50 nC· cm -2 the formation of special periodic structure takes place after switching off the moderate value of the electric field. There are dislocation walls which separate the regions of inclined smectic layers with the opposite signs of inclination angle δ for neighbour regions (domains). We have found that 1) angle δ is proportional to the value of the spontaneous polarization, 2) the period D of the dislocaton walls is inversely proportional to P 2 s , 3) during the electric field treatment the periodicity of domains and the tilt angle δ of the inclination of smectic layers can differ essentially in the bulk of FLC layer and near the electrode surfaces. Complicated character of SSFLC switching can be related with the interference of bulk and surface dislocation walls. The role of the charged dislocation walls in the phenomenon of volume bistability is also discussed.