Ultrafast Nonvolatile Graphene Memory Enabled by InP@ZnS Core-Shell Quantum Dots

Nonvolatile memories (NVMs) with submicrosecond program/erase (P/E) speeds are highly desirable for data-centric and in-memory computing, yet conventional floating-gate architectures are fundamentally limited by high tunneling barriers in wide-bandgap dielectrics. Here, we report graphene memories using solution-processed InP@ZnS core-shell quantum dots as charge-storage centers at the graphene interface. The devices exhibit large memory windows, ambipolar storage, reliable switching with 150 ns gate pulses, extrapolated ten-year retention, and endurance over 10⁵ program/erase cycles. Comparisons with Au@SiO₂ core-shell quantum dots, bare InP dots, and a PMMA spacer show that the ZnS shell markedly enhances charge injection. Time-resolved measurements and Fowler-Nordheim analysis reveal an earlier transition to Fowler-Nordheim tunneling in InP@ZnS devices. These results establish shell-bandgap engineering as a practical route to ultrafast, low-power nonvolatile memories.