Ultrafast Negative Capacitance Transition for 2D Ferroelectric MoS₂/Graphene Transistor

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Negative capacitance (NC) enables subthreshold swing (SS) below fundamental limits by enhancing surface potential modulation in transistors.
• Previous NC studies in PZT and HZO films showed limitations in low SS persistence over a wide drain current range.
• Existing NC transitions occur on microsecond timescales, insufficient for high-speed electronics.

Purpose of the Study:

• To demonstrate ultrafast (nanosecond) negative capacitance transitions in 2D single-crystal CuInP2S6 (CIPS) flakes.
• To introduce a novel negative capacitance Dirac source-drain field-effect transistor (FET) architecture.
• To achieve ultralow SS and high on-off ratios for advanced electronic devices.

Main Methods:

• Utilized a fast-transient measurement technique to observe nano-second NC transition states in CIPS flakes.
• Integrated CIPS NC transition with Dirac contacts and controlled charge transfer in a CIPS/channel (MoS2/graphene) heterostructure.
• Fabricated and characterized monolayer MoS2-based FETs with the novel device architecture.

Main Results:

• Demonstrated clear nano-second negative capacitance transition states in 2D CIPS flakes.
• Achieved an ultralow SS of 4.8 mV/dec with an average sub-10 SS across five decades.
• Obtained an on-off ratio exceeding 10^7 in the developed negative capacitance Dirac FET.
• Simultaneously improved transport and body factors in monolayer MoS2-based FETs.

Conclusions:

• The developed NC Dirac FET architecture significantly outperforms previous reports in terms of SS and on-off ratio.
• Ultrafast NC transitions in 2D materials are viable for next-generation electronics.
• This approach paves the way for ultralow-SS FETs crucial for high-speed and low-power electronic applications.