Polarisation Readout and Determination of Landau Parameters of VDF-TrFE Thin Films from Dielectric Nonlinearities

VDF-TrFE copolymer thin films of different molar compositions have been studied with regard to their application in (all-organic) FeRAMs. Thin films were prepared by spin coating on a metallized glass substrate. Dielectric nonlinearities of poled and unpoled samples were measured and associated with application-relevant properties, namely switching, readout procedure, and temperature dependence. It has been shown that polarisation of films with high fraction of VDF does not change significantly up to 80°C. Furthermore, a non-destructive method for polarisation readout has been demonstrated. The practical considerations and experimental results are discussed on the base of the Landau theory.