Optical Modulation of Interfacial Coupling Drives a Transition from Free-Epitaxy to Locked-Epitaxy

Area of Science:

• Materials Science
• Surface Science
• Thin Film Growth

Background:

• Controlling epitaxial states in quasi-van der Waals (vdW) heterostructures is difficult due to weak interfacial guidance favoring free epitaxy.
• Achieving specific interfacial coupling is crucial for tailoring heterostructure properties.

Purpose of the Study:

• To investigate the effect of light irradiation on the epitaxial growth of Fe4N/mica quasi-vdW heterostructures.
• To demonstrate optical control over the transition from free epitaxy to locked epitaxy.

Main Methods:

• Thin film deposition via sputtering under controlled light conditions (dark vs. illumination).
• Characterization of film structure, including lattice constants and in-plane alignment.
• Density functional theory (DFT) calculations to analyze interfacial bonding.

Main Results:

• Under dark growth, Fe4N/mica exhibits free epitaxy with Fe4N(001) and bulk-like lattice constant.
• Illumination during sputtering induces locked epitaxy, forming Fe4N(111)/mica with specific registry and strain.
• Experiments reveal the transition occurs early in the growth process.
• DFT calculations show vdW-dominated interface for free epitaxy and stronger non-vdW interactions for locked epitaxy.

Conclusions:

• Optical modulation of interfacial coupling provides a practical method to control epitaxy in quasi-vdW heterostructures.
• This approach enables the transition from free to locked epitaxy, offering new possibilities for materials engineering.