Nonvolatile Memory Action Due to Hot-Carrier Charge Injection in Graphene-on-Parylene Transistors

We fabricated graphene field-effect transistors (GFETs) with hybrid organic/inorganic gate dielectrics, in which parylene C is used as the organic component. The HOMO-LUMO gap of parylene is large enough to provide effective gate insulation, yet significantly smaller than that of the inorganic component (SiO2) of the dielectric. This allows this polymeric material to serve as an effective "floating node" that may be programmed by applying large voltage pulses to the GFET drain. We identify the role of two types of trapping in these devices: the first is mediated by short-lived interfacial states at the graphene parylene interface, while the second, which is responsible for the nonvolatile memory function, involves hot-carrier injection into long-lived trap states deep in the parylene layer. Retention measurements demonstrate that charge injected into the parylene interior may be retained over long decay times (months), thereby confirming the potential of graphene-on-parylene for nonvolatile memory implementations.