Quantum oscillation in carrier transport in two-dimensional junctions.

Area of Science:

• Condensed matter physics
• Materials science
• Nanotechnology

Background:

• Two-dimensional (2D) junction devices are gaining attention for electronic applications.
• Existing literature often assumes vertical operation for these devices.

Purpose of the Study:

• To clarify the operational mechanism of 2D junction devices.
• To investigate the role of monolayer-bilayer interfaces in device function.
• To challenge the prevailing understanding of vertical 2D junction operation.

Main Methods:

• Theoretical modeling using non-equilibrium Green function (NEGF) formalism.
• First-principles calculations employing density functional theory (DFT).
• Analysis of quantum transport phenomena in prototypical devices.

Main Results:

• Demonstrated that most 2D junctions function as lateral monolayer-bilayer-monolayer structures.
• Identified that bilayer regions exhibit smaller bandgaps than monolayer regions due to electrostatic screening.
• Observed the formation of a potential well, in addition to a potential barrier, in the bilayer region.
• Calculated distinct oscillations in the transmission coefficient for black phosphorus devices.

Conclusions:

• Vertical 2D junction operation is not feasible as widely believed.
• The monolayer-bilayer-monolayer configuration dictates device behavior.
• Potential wells in bilayer regions significantly influence electron and hole quantum transport.
• A simple quantum well model can qualitatively explain the observed transport characteristics.