Asymmetric Response to Electric Field in Nematic Liquid Crystal Cells Containing Vanadium Oxide Thin Films Prepared by Sol-Gel Synthesis

The asymmetric insertion of oxide layers having mixed conduction properties(ionic and electronic) in liquid crystal cells induces various kinds of electro-opticalresponse of the liquid crystals, and this behaviour has been related to the structuraldifferences of the inserted films. In this work, it is reported a structural studyof such oxide films deposited on indium tin oxide (ITO) covered glasses. To havefurther confirmations of the model and a better understanding of the basic mechanismunderlying the rectification effect and the connections with the structuraland electrical properties of the films, Vanadium oxide layers have been studiedbefore and after thermal treatment. Moreover the gelification via spin coatinghas been implemented and the optimisation tests of various relevant parametershave been performed. The chemical, structural and optical evolution has beenextensively investigated as a function of the thermal annealing treatment, by performingvibrational spectroscopy analysis (micro-Raman and IR) and impedancespectroscopy characterization, before testing the films into the NLC cells.