A Resonant X-Ray Scattering Study of the Antiferroelectric and Ferrielectric Phases in Liquid Crystal Devices

Resonant x-ray scattering has been used to investigate the interlayer ordering of the antiferrolectric and ferrielectric smectic C* sub-phases in a device geometry. The liquid crystalline materials studied contain a selenium atom and the experiments were carried out at the selenium K-edge allowing x-ray transmission through glass. The resonant scattering peaks associated with the antiferroelectric phase were observed in two devices containing different materials. It was observed that the electric-field-induced antiferroelectric to ferroelectric transition coincides with the chevron to bookshelf transition in one of the devices. Observation of the splitting of the resonant peaks as a function of applied field also confirmed that no helical unwinding occurs at fields lower than the chevron to bookshelf threshold. Resonant features associated with the 4-layer ferrielectric liquid crystal phase were observed for the first time in a device geometry. Monitoring the electric field dependence of these ferrielectric resonant peaks showed that the chevron to bookshelf transition occurs at a lower applied field than the ferrielectric to ferroelectric switching transition.