Quantum tunnelling and leakage current across two-dimensional materials.

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Leakage current critically impacts electronic device operation and reliability.
• Two-dimensional (2D) materials are increasingly used in ultrascaled electronics, but leakage current behavior is not fully understood.
• Understanding leakage current is crucial for advancing nano-electronic device design.

Purpose of the Study:

• To analyze and compare leakage current in hexagonal boron nitride (hBN), molybdenum disulfide, tungsten disulfide, and SiO2/n++Si.
• To investigate the influence of material properties and physical dimensions on leakage current.
• To establish predictive models for leakage current in 2D material-based devices.

Main Methods:

• Experimental analysis of 2D materials (hBN, MoS2, WS2) and SiO2/n++Si samples at nanoscale and device levels.
• Computational modeling using technology computer-aided design (TCAD) and density functional theory (DFT).
• Systematic variation of material thickness and electrode surface roughness.

Main Results:

• Bottom electrode surface roughness significantly alters leakage current under electric fields.
• For multilayer 2D materials, bandgap and atomic defect density are primary leakage determinants.
• For monolayer 2D materials, electrode-to-electrode distance (thickness) is the dominant factor, explaining higher leakage in thinner hBN compared to MoS2/WS2.
• An equivalence in leakage current between hBN and SiO2 films was established.

Conclusions:

• Leakage current in 2D materials is governed by distinct factors depending on whether they are monolayers or multilayers.
• Thickness is a critical parameter for leakage in monolayer 2D materials, overriding bandgap differences.
• The established hBN-SiO2 equivalence allows for performance and reliability predictions in 2D nano-electronic devices like transistors and memristors.