Fully printed ZnO-based valency-change memories for flexible and transparent applications

Printable and flexible memory devices have attracted a great deal of attention in several emerging technological applications for the development of flexible electronics, such as interconnections/wearables/smart devices for the internet of things (IoT). In this work, we report on the fabrication of flexible, transparent, and fully inkjet-printed resistive random access memory (ReRAM) cells using poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS)/ZnO/PEDOT:PSS structures. The electrical characteristics were studied, including the determination of space charge limited conduction (SCLC) as the dominant charge transport mechanism. In addition, the bending performance and the transparency of the devices was tested in order to confirm the reliable operation and reproducibility of the cells. The switching for the printed structures of PEDOT:PSS/ZnO/PEDOT:PSS was led through the formation and dissolution of a stable oxygen vacancy filament, as confirmed by conductive atomic force microscopy. While the conduction mechanism for the high resistance state (HRS) was attributed to the SCLC mechanism. The switching of the memory cells, their endurance and retention properties were analysed and indicated the stability of the HRS and low resistance state for more than 10(4) cycles and 10(5) s comparable to ZnO-based ReRAM produced by clean-room techniques. The study of the mechanical flexibility of the cells shows that up to 700 bending cycles can be reached without significantly changing the switching characteristics.