Analysis of Static Imprint Phenomenon in Ferroelectric VDF-TrFE Copolymer Film for Nonvolatile Memory Devices

This work shows that the coercive voltage or coercive electric field, which is the voltage or electric field to make the net polarization zero in a ferroelectric capacitor, depends on the direction of the sweep voltage applied externally. The difference in the coercive fields is shown in a metal-ferroelectric polymer-metal as an imprint phenomenon after the polymer, poly(vinylidene fluoride-co-trifluoroethylene), P(VDF-TrFE), was prepared by using a spin coating method. This imprint can induce a read/write failure in ferroelectric memory devices; hence, it is important to study the imprint for reliability. The difference in the coercive voltages increases as the thickness of the capacitors increases while the difference in the coercive fields, the coercive voltage normalized for thickness remains nearly constant for all thicknesses. In conclusion, the imprint phenomenon is derived not from inside the ferroelectric polymer but from charge injection into the electrode.