IMF2017

Ferroelectric polymers such as poly(vinylidenedifluoride–trifluoroethylene) P(VDF-TrFE) are great alternative to conventional ceramics based non-volatile memory (NVM) devices owing to their low temperature and easy processing, compatible with flexible electronics. Despite its excellent properties, large roughness and leakage are the main issues with P(VDF-TrFE). A thin layer of PMMA, an insulating polymer, is introduced to further improve the leakage current and roughness. To study the reliability of flexible ferroelectric capacitors (FeCaps), in this work P(VDF-TrFE)/PMMA bilayer devices were subjected to the individual as well as the combined effect of mechanical and electrical strain cycling. The effect of these strains on ferroelectric behavior was different depending on the way PMMA was incorporated (i.e. either on top of P(VDF-TrFE, or at the bottom of it). FeCaps with PMMA above P(VDF-TrFE) showed better electrical and mechanical endurance. The electrical and mechanical fatigue measurements exhibited that the flexible FeCaps are more likely to suffer from electrical fatigue than mechanical fatigue at moderate strains. The results suggest that increasing the bending strains to ~0.5% results in a slight increase in the coercivity of the samples whilst no severe decrement in polarization after testing up to 30000 bending cycles ( with bending radius of 12 mm) accompanied by a formation of a few black spots and cracking on the top electrode. Moreover, electric field cycling, with or without the mechanical strain, results in a severe drop in the ferroelectric polarization of the devices, manifested in extensive degradation and delamination of the top electrode.