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

Abstract

In the designed copolymers of poly(9-(4-vinyl benzyl)-9H-carbazole) (PVCz)-random-poly(1-(4-nitro-azophenyl)-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 10 8 read cycles and showed a long retention time of 10 4 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.

A low onset voltage WORM type polymer memory based on functional PES

“…And as shown in the DTG curves, the polymers have two main unstable points of 391°C and 446°C because of the degradation of the side chain and the backbone of the polymer respectively, while a tiny weight loss (1%) at a temperature around 150°C was caused by the evaporation of water absorbed on the polymer surface. From all above, the thermal property of CN‐Azo‐PES is comparable with that of polyimides and better than the other polymer materials that have been reported for electrical memory usage . And to the best of our knowledge, in the memory storage processes, the outstanding thermal stabilities will make contributions to the performance of the devices for the absence of thermal decomposition.…”

“…In particular, the high photosensitivity of the azo dye molecules makes azobenzene polymers popular for use as optical and electronic materials. Also according to the literature, some azobenzene derivatives can be induced by an electric field . Kang and his coworkers have demonstrated that polymers bearing pendent azobenzene chromophores with electron‐accepting terminal moieties exhibit write‐once read‐many (WORM) behavior which is attributed to charge trapping at the azobenzene chromophores and that the device has a low onset voltage .…”

Adjusting the Proportion of Electron‐Withdrawing Groups in a Graft Functional Polymer for Multilevel Memory Performance

“…[32,33] These new absorptionp eaks are ascribed to NÀH( nNÀHa t3 666 cm À1 )a nd CÀH( nCÀHa round 2970 cm À1 and 2920 cm À1 )f or all graft polymers. [32][33][34][35] Thus, the presence of DHI or NPH moieties anchored onto the pendant polymers can be confirmed by the changes in the IR spectra line shapes of the polymers.…”

Synthesis of methyl‐substituted azobenzene–carbazole conjugated copolymers with photoinduced structural changes

“…Furthermore, the rod‐like trans isomer can be used as a mesogenic group for liquid crystals. Focusing on such reversible structural changes and its liquid crystallinity, many applications, such as polymer actuators, holographic optical elements (HOEs), light‐responsive elastomers, and polymer memories, are expected for azobenzenes. However, there are few reports on polymers in which azobenzene units are introduced in the main chain.…”