A Descriptor-Driven Thermodynamic Framework for Achieving Unidirectional Nucleation in 2D Material Epitaxy

Area of Science:

• Materials Science
• Surface Science
• Nanotechnology

Background:

• Wafer-sized single-crystal epitaxy of two-dimensional (2D) materials is essential for advanced applications.
• Multidirectional nucleation, caused by symmetry mismatches, hinders achieving large-scale single-crystal growth.
• Existing methods often lack a universal approach for diverse 2D materials.

Purpose of the Study:

• To develop a universal framework for enabling unidirectional nucleation and epitaxy in diverse 2D materials.
• To overcome the limitations imposed by multidirectional nucleation in 2D material growth.
• To provide guidelines for achieving wafer-scale single-crystal epitaxy.

Main Methods:

• Integrated thermodynamic modeling to classify nucleation regimes (edge-dominated vs. surface-dominated).
• Developed a quantitative epitaxial descriptor based on lattice mismatch and interfacial spacing.
• Employed substrate-step engineering for controlled nucleation.

Main Results:

• The framework successfully predicts nucleation behavior for graphene, hexagonal boron nitride (h-BN), and molybdenum disulfide (MoS2).
• Identified that surface-dominated nucleation requires precise alignment of terrace steps with the epitaxial axis.
• Demonstrated that the epitaxial descriptor eliminates the need for computationally expensive first-principles calculations.

Conclusions:

• Established a universal, hierarchical framework for unidirectional nucleation and epitaxy across various 2D materials.
• Provided a general protocol for substrate-step engineering to promote controlled nucleation.
• Enabled guidelines for achieving wafer-scale single-crystal epitaxy of 2D materials.