Slow Charge Dynamics at 2D Material/Dielectric Interfaces Revealed by Multimodal Microscopy.

Area of Science:

• Materials Science
• Nanotechnology
• Surface Science

Background:

• Charge trapping and slow decay dynamics at 2D material-dielectric interfaces impede nanoelectronic performance and stability.
• The underlying physical mechanisms are poorly understood due to challenges in monitoring nanoscale charge evolution and disentangling intrinsic from extrinsic factors.

Purpose of the Study:

• To elucidate the charge decay pathways at 2D material-dielectric interfaces.
• To develop a framework for designing stable 2D nanoelectronic devices.

Main Methods:

• A multimodal microscopy platform combining conductive atomic force microscopy (c-AFM), time-resolved Kelvin probe force microscopy (TR-KPFM), and correlated spectroscopy.
• Investigation of WS₂/SiO₂ and graphene/SiO₂ interfaces.

Main Results:

• WS₂ interfaces exhibit triple-exponential decay, while graphene interfaces show double-exponential decay, correlating decay complexity with intrinsic material properties.
• Three distinct charge decay channels were identified: environmental neutralization, material-specific intrinsic defect pathways (WS₂-unique), and universal substrate trap pathways.
• Hexagonal boron nitride (hBN) encapsulation effectively suppressed extrinsic decay channels, leading to charge retention exceeding 17 days.

Conclusions:

• The study provides a comprehensive model for charge decay dynamics at 2D material interfaces.
• Hexagonal boron nitride encapsulation is a viable strategy for achieving quasi-nonvolatile charge retention in 2D nanoelectronics.
• The developed framework offers a roadmap for engineering stable and high-performance 2D nanoelectronic devices.