Extending the Schottky-Mott Rule to Atomic Thickness: Descriptors for Two-Dimensional Semiconductor-Metal Contacts

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Ultralow-resistance Ohmic contacts are crucial for next-generation electronics based on two-dimensional (2D) materials.
• The classical Schottky-Mott rule is inadequate for 2D systems due to quantum confinement and Fermi-level pinning.

Purpose of the Study:

• To develop accurate descriptors for Schottky barrier heights at 2D semiconductor-metal interfaces.
• To identify optimal metal electrodes for creating low-resistance Ohmic contacts in 2D materials.

Main Methods:

• Utilized a combination of domain knowledge and machine learning to derive physically interpretable Schottky-barrier descriptors.
• Applied these descriptors to predict barrier heights based on intrinsic material parameters like work function and electronegativity.
• Screened 1392 heterojunctions involving transition metal dichalcogenides and various metal substrates.

Main Results:

• Developed novel descriptors that accurately predict Schottky barrier heights.
• Identified 12 promising metal electrodes for achieving Ohmic contacts with 2D semiconductors.
• Introduced a new Schottky-barrier factor (δ) and reformulated the Schottky-Mott rule, highlighting the roles of work function difference (ΔWF) and electronegativity mismatch (Δχ).

Conclusions:

• The co-modulation of interfacial work function difference and electronegativity mismatch governs Schottky-barrier formation.
• Extended Schottky-Mott physics to the atomic scale for 2D materials.
• Provided practical design guidelines for engineering low-resistance Ohmic contacts in 2D electronic devices.