From Growth Surface to Device Interface: Preserving Metallic Fe under Monolayer Hexagonal Boron Nitride

Area of Science:

• Materials Science
• Surface Chemistry
• Nanotechnology

Background:

• Hexagonal boron nitride (h-BN) is a 2D material with potential applications as a tunnel barrier.
• Understanding the interfacial chemistry of h-BN with catalyst materials is critical for its integration into devices.
• Iron (Fe) is a common catalyst and component in magnetic tunnel junctions.

Purpose of the Study:

• To investigate the interfacial chemistry between Fe catalyst foils and monolayer h-BN.
• To determine the protective properties of h-BN against atmospheric oxidation of Fe.
• To explore the recovery of the Fe-h-BN interface after annealing.

Main Methods:

• Scanning electron microscopy (SEM)
• X-ray photoemission spectroscopy (XPS)
• Scanning photoelectron microscopy (SPEM)
• Atmospheric exposure tests
• Vacuum annealing

Main Results:

• Monolayer h-BN effectively protects the underlying Fe surface from oxidation during prolonged atmospheric exposure.
• Fe oxidation is observed on bare Fe regions and near defects in the h-BN film.
• The Fe-h-BN interface can be restored by vacuum annealing at ~600 °C, albeit with induced h-BN defects.

Conclusions:

• The strong interfacial interaction between h-BN and Fe prevents rapid oxidation, highlighting h-BN's protective capabilities.
• Defects in h-BN films act as pathways for oxidation, emphasizing the need for high-quality films.
• Findings are relevant for transfer-free integration of h-BN in electronic devices, such as magnetic tunnel junctions.