Characterizing trapped charge dynamics in imprinted poly(vinylidene fluoride-trifluoroethylene) ferroelectric thin films using the fast ramp thermally stimulated current technique

Abstract

Poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) ferroelectric thin films are promising materials for sensors, nonvolatile memory applications, and energy harvesting. Imprint, the time-dependent resistance to polarization reversal, is a key material property that limits electronic applications and is poorly understood. In this work, we investigated the link between imprint and charge trap states within the film. A fast ramp rate thermally stimulated current (FR-TSC) measurement was developed to quantify and characterize trapped charge dynamics in imprinted P(VDF-TrFE) thin films in an appropriate time frame. Thin films of P(VDF-TrFE) on oxidized Si substrates were characterized following controlled initialization, polarization, and imprint. Trap states were thermally filled/emptied by temperature cycling between 20 °C and 100 °C using heating and cooling rates of 1 K/s. Dynamics of this fast-ramp TSC indicate the presence of not only trap states but also reversible and irreversible charge accumulation. Results also show an asymmetry with respect to poling orientation, indicating that traps are influenced by processing conditions and contact materials. The development of this FR-TSC technique provides understanding of polarization dynamics and material interactions affecting ferroelectric properties of P(VDF-TrFE).