Layer-by-Layer Connection for Large Area Single Crystal Boron Nitride Multilayer Films

Area of Science:

• Materials Science
• Nanotechnology
• Condensed Matter Physics

Background:

• Boron Nitride (BN) is a promising material for advanced applications like single photon emission and deep UV optoelectronics.
• Existing synthesis methods for multilayer BN films face challenges with semiconductor process compatibility and precise layer-by-layer domain connection.
• The preparation of single-crystal metal foils for BN growth is incompatible with current semiconductor fabrication processes.

Purpose of the Study:

• To demonstrate a novel approach for growing large-area multilayer single-crystal BN films.
• To investigate the influence of Fe content in Fe-Ni alloy substrates on BN film growth and quality.
• To elucidate the layer-by-layer connection mechanism between adjacent multilayer BN domains.

Main Methods:

• Chemical vapor deposition (CVD) of multilayer single-crystal BN films on face-centered cubic Fe-Ni (111) single-crystal alloy thin films.
• Utilized substrates with varying stoichiometric phases of Fe-Ni alloys deposited on Sapphire.
• Employed selected area electron diffraction (SAED), microphotoluminescence (µPL) spectroscopy in the deep UV, and high-resolution transmission electron microscopy (HRTEM) for characterization.

Main Results:

• Demonstrated tunable and improved BN growth by increasing the Fe content in single-crystal Fe-Ni (111) substrates.
• Observed the formation of pyramid-shaped multilayer BN domains with aligned orientation, facilitating continuous connection.
• Unambiguously evidenced a layer-by-layer, 'first-meet-first-connect' mosaic stitching mechanism for domain connection.

Conclusions:

• The study successfully developed a method for growing large-area multilayer single-crystal BN films with controlled stacking.
• The layer-by-layer connection mechanism, driven by domain orientation and composition of the Fe-Ni substrate, was confirmed.
• Verified unidirectional AB (Bernal) and ABC (rhombohedral) stacking orders in the synthesized BN films.