Oxide ferroelectric thin film/nematic liquid crystal devices

Abstract

The visualisation of domains in ferroelectrics by decoration of the surface with nematic liquid crystals (NLC) has been used previously for the study of single crystal ferroelectrics. Until recently there has, however, been no work reported on the coupling between NLC and the polarisation in ferroelectric thin films. Such a coupling would open the possibility of imparting switchable memory to nematic LC displays. This paper reviews work on the fabrication and testing of device structures with the structure: glass/ITO/PZT/LC/ITO/glass (PZT=240nm sol-gel PbZr 0.3Ti 0.7O 3; ITO= sputtered transparent, conductive indium tin oxide). When a voltage pulse is applied to the sandwich via the ITO electrodes, the switched polarisation in the ferroelectric thin film is observed. It has been found that a thin layer of TiO 2, deposited by sol-gel onto the ITO, can be highly beneficial in improving the control of PZT nucleation and grain size/structure, improving the uniformity and quality of the structures. It has also been found possible to measure the poling voltage required to obtain a reorientation in the nematic LC layer and to refer this back to the hysteresis loop obtained from the PZT. The potential of the structure for device applications is discussed. © 2001 Taylor & Francis.