In-Plane Adaptive Heteroepitaxy of 2D Cesium Bismuth Halides with Engineered Bandgaps on c-Sapphire

Area of Science:

• Materials Science
• Solid State Physics
• Nanotechnology

Background:

• Engineered bandgaps in 2D materials are vital for advanced optoelectronic devices.
• Integrating 2D materials with diverse lattice constants on a single substrate is challenging due to lattice mismatch.

Purpose of the Study:

• To develop a method for high-oriented heteroepitaxy of multicomponent 2D materials with varying lattice constants.
• To enable the integration of these materials on low-cost dielectric substrates for optoelectronics.

Main Methods:

• In-plane adaptive heteroepitaxy of 2D cesium bismuth halides (Cs3Bi2X9, X = I, Br, Cl) on c-plane sapphire.
• Utilizing a 30° crystal orientation rotation to manage interfacial strain.
• First-principles calculations to assess thermodynamic stability.

Main Results:

• Achieved high-oriented epitaxy of Cs3Bi2X9 single crystals with lattice constants ranging from 8.41 to 7.71 Å on sapphire (4.76 Å).
• Demonstrated thermodynamic stability of the grown phases, attributed to interfacial energy minima.
• Cs3Bi2I9 photodetector exhibited high detectivity (3.7 × 10^12 Jones) due to excellent crystal quality.

Conclusions:

• In-plane adaptive heteroepitaxy offers a viable strategy for integrating 2D materials with varying lattice constants.
• This approach facilitates the development of high-performance integrated optoelectronic devices.
• The findings provide a theoretical and experimental basis for future 2D material integration.