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

Area of Science:

• Materials Science
• Nanotechnology
• Electrical Engineering

Background:

• Conventional nonvolatile memories (NVMs) face limitations in program/erase speeds due to high tunneling barriers in wide-bandgap dielectrics.
• Data-centric and in-memory computing demand NVMs with submicrosecond switching capabilities.

Purpose of the Study:

• To engineer novel graphene-based nonvolatile memories (NVMs) utilizing core-shell quantum dots for enhanced performance.
• To investigate the impact of shell-bandgap engineering on charge injection and switching dynamics in quantum dot memories.

Main Methods:

• Fabrication of graphene memory devices incorporating InP@ZnS core-shell quantum dots as charge-storage centers.
• Characterization of memory performance, including program/erase speeds, memory window, retention, and endurance.
• Comparative analysis with devices using different quantum dot configurations (Au@SiO2, bare InP) and a PMMA spacer.

Main Results:

• The InP@ZnS quantum dot devices demonstrated ultrafast switching with 150 ns gate pulses and extrapolated ten-year retention.
• Devices exhibited large memory windows, ambipolar storage, and endurance exceeding 10^5 program/erase cycles.
• The ZnS shell was found to significantly enhance charge injection and promote an earlier transition to Fowler-Nordheim tunneling.

Conclusions:

• Shell-bandgap engineering of quantum dots is a viable strategy for developing ultrafast, low-power nonvolatile memories.
• Graphene memories utilizing InP@ZnS core-shell quantum dots offer a promising platform for next-generation computing.
• The study highlights the critical role of the dielectric shell in optimizing charge-transfer mechanisms for memory applications.