Spin‐coated organic ferroelectric films for non‐volatile memories

Abstract

AbstractFor low cost memory devices like ferroelectric field‐effect transistors (FeFETs) or cross bar arrays, organic materials are important, due to their processability from solutions at room temperature. The copolymer Poly[vinylidene fluoride trifluoroethylene] (P[VDF/TrFE]) is a candidate for a possible application as a ferroelectric component in such structures. In order to improve the performance of FeFETs with P[VDF/TrFE], we investigate metal–ferroelectric–insulator–semiconductor (MFIS) capacitors. Implementing a method proposed by Miller and McWorther, we simulate the capacitance‐voltage (C–V) characteristics of MFIS stacks and the hysteresis due to the ferroelectric switching of the copolymer. We vary the parameters thickness and permittivity of the insulator as well as the as the thickness of the ferroelectric layer and predict in that way conditions where a saturation of the polarization can be reached. We also report on retention and cycle endurance measurements. Furthermore, we show measurements of the dipole alignment of ultrathin ferroelectric copolymer films, down to 10 nm thickness. No ferroelectric threshold was found, even for this thickness, if an adapted system of electrodes is used. Here, we introduce the near edge X‐ray absorption fine structure (NEXAFS) method as a new tool for the characterization of ferroelectric dipole switching.