Surface Directed Phase Separation of Semiconductor Ferroelectric Polymer Blends and their Use in Non‐Volatile Memories

Abstract

The polymer phase separation of P(VDF‐TrFE):F8BT blends is studied in detail. Its morphology is key to the operation and performance of memory diodes. In this study, it is demonstrated that it is possible to direct the semiconducting domains of a phase‐separating mixture of P(VDF‐TrFE) and F8BT in a thin film into a highly ordered 2D lattice by means of surface directed phase separation. Numerical simulation of the surface‐controlled de‐mixing process provides insight in the ability of the substrate pattern to direct the phase separation, and hence the regularity of the domain pattern in the final dry blend layer. By optimizing the ratio of the blend components, the number of electrically active semiconductor domains is maximized. Pattern replication on a cm‐scale is achieved, and improved functional device performance is demonstrated in the form of a 10‐fold increase of the ON‐current and a sixfold increase in current modulation. This approach therefore provides a simple and scalable means to higher density integration, the ultimate target being a single semiconducting domain per memory cell.

Microstructured organic ferroelectric thin film capacitors by solution micromolding

“…In order to obtain more regular structures diodes were fabricated by nanomolding the P(VDF-TrFE) followed by filling the resulting open spaces with a semiconductor 28,29 or by surface directed phase separation. 30 Reports on the physics of devices comprising patterned organic ferroelectric materials are however limited. Ferroelectric properties are typically investigated locally by e.g.…”

Data retention in organic ferroelectric resistive switches

“…Figure 3 illustrates the proposed depolarization mechanism in the device. The mechanism is tightly related to the (well-established) morphology of these devices; [5][6][7][8] see SI for Atomic Force Microscopy images of our devices ( Figure S2). We will consider the system's total energy to argue that the polarization of the ferroelectric in close vicinity to the semiconductor is inherently unstable.…”

“…It is not surprising that such a small injection barrier leads to a low ION/IOFF ratio, in this case of about 2.5; [9,31] at the same time, it is not unlikely that this ratio can be significantly improved by proper morphology and composition control. [8] It has to be noted that the difference between ION and IOFF currents originates truly from the injection barrier modulation and not from spurious effects associated e.g. ionic impurities in the semiconductor.…”

“…The phase separation in the blend is driven by a spinodal decomposition process which results in sub-micron sized semiconductor domains embedded in an insulating ferroelectric matrix. [5][6][7][8] Thus, transport of charge carriers, which is needed for the resistive read out, is possible only via the semiconducting phase. The working principle of the resistive switch relies on a modulation of the barrier for charge injection from the metal electrode into the semiconductor by the polarization charges in the ferroelectric.…”

Thin film thermistor with positive temperature coefficient of resistance based on phase separated blends of ferroelectric and semiconducting polymers

“…As the bistable diode can reversibly be switched between the On-state and the Off-state it has been used as a non-volatile bistable memory. 22,[37][38][39][40][41][42][43][44][45] Here, in order to realize a PTC thermistor, we make use of the temperature dependence of the On-state current density. We first poled the thermistor at ambient temperature in the On-state.…”