Dual-Mechanism-Controlled Ternary Memory Devices Fabricated by Random Copolymers with Pendent Carbazole and Nitro-Azobenzene

In the designed copolymers of poly­(9-(4-vinyl benzyl)-9H-carbazole) (PVCz)-random-poly­(1-(4-nitro-azo-phenyl)-pyrrole-2, 5-dione) (PMIDO3), carbazole donor and nitro-azobenzene acceptor are introduced into the lateral chains to induce charge transfer under an electric field, and the resulting copolymers have a progressive increase in the nitrogen content to induce filamentary conduction. The fabricated devices with a simple sandwich configuration distinctively exhibit three conductivity states when a negative bias is applied which can be encoded as “0”, “1” and “2” for future ternary data storage. The fabricated devices could endure 10⁸ read cycles and showed a long retention time of 10⁴ s. It is worth noting that the switch-OFF voltages and the OFF-currents are significantly affected by the MIDO3 content within the polymers. The experimental results indicate that charge transfer between the donor and acceptor is responsible for the first switching and the second switching can be attributed to the filamentary rupture. This approach of achieving devices with multistable states through combination of different switching mechanisms in one device may provide a framework for the design and selection of multilevel electrical memory materials in future research