Quantifying the role of electronic charge trap states on imprint behavior in ferroelectric poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) thin films

Poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) ferroelectric thin films are a potentially promising material for sensors or non-volatile memories. Imprint, the time-dependent resistance to polarization reversal, is a key material property that limits applications and is poorly understood. Based on experimental time and temperature dependences, we propose and investigate the link between imprint and charge trap states. A novel fast-ramp thermally stimulated current (TSC) measurement was developed to quantify and characterize the traps in an appropriate time-frame. Thin films of P(VDF-TrFE) on oxidized Si substrates were characterized following controlled initialization, fatigue, polarization, and imprint. Trap states were thermally filled/emptied by temperature cycling between 20-100°C, using heating and cooling rates between 1 and 5°C/s. Dynamics of this fast-ramp TSC indicate the presence of not only trap states, but also reversible and non-reversible charge accumulation. The presence of electrically active traps were verified by measurements over 1-10 ⁴ s imprint times. Trapped charge directly correlated with the log of the imprint time, with a rate of ∼0.12μC/ cm ²/decade.