Graphene oxide functionalized with a conjugated polyelectrolyte for a nonvolatile digital-type memristor and encryption applications

Graphene and its derivatives-based molecular computation has ignited a revolution in the global microelectronics industry due to their exceptional electronic quality and transport properties. Current challenges include the optimization of the low-temperature CMOS-compatible processes and the improvement of large-scale production stability; however, the collaborative development of the two-dimensional material family is accelerating technological breakthroughs. To switch graphene oxide (GO) between the ON and OFF states in nanoelectronic memory devices, a novel conjugated polyelectrolyte, poly[9,9-bis(6'-(3-methyl-1-imidazolium-yl)hexyl)-fluorene-<i>alt</i>-1,1,2,2-tetraphenylethene] (PFTPE-NMI⁺Br^-), is non-covalently bonded to the GO surface to give the PFTPE-NMI⁺Br^-:GO blends, in which PFTPE-NMI⁺Br^- acts as the electron donor and GO serves as the electron acceptor. The as-fabricated electronic device with a configuration of Al/PFTPE-NMI⁺Br^-:GO/ITO shows a nonvolatile ternary rewritable memory effect, with a switch-off voltage of +2.29 V and two switch-on voltages of -1.22 and -2.03 V. The observed OFF : ON₁ : ON₂ current ratio reached 1 : 90 : 40000. This result can be attributed to the combination of two kinds of charge transfer processes in the material system: one from PFTPE-NMI⁺Br^- to GO and another from the polymer backbone to the imidazolium moieties. In contrast to PFTPE-NMI⁺Br^-:GO, the PFTPE-NMI⁺Br^--based electronic device only shows write-once-read-many-times (WORM) memory performance, with a switch-on voltage of -1.45 V. By taking advantage of the outstanding ternary memory performance and high OFF : ON₁ : ON₂ current ratio exhibited by the device, a logic gate circuit encryption unit based on OR, XOR and AND logic gates has been constructed.