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

Abstract

We investigate the interfacial chemistry between Fe catalyst foils and monolayer hexagonal boron nitride (h-BN) following chemical vapor deposition and during subsequent atmospheric exposure, using scanning electron microscopy, X-ray photoemission spectroscopy, and scanning photoelectron microscopy. We show that regions of the Fe surface covered by h-BN remain in a metallic state during exposure to moist air for ∼40 h at room temperature. This protection is attributed to the strong interfacial interaction between h-BN and Fe, which prevents the rapid intercalation of oxidizing species. Local Fe oxidation is observed on bare Fe regions and close to defects in the h-BN film (e.g., domain boundaries, wrinkles, and edges), which over the longer-term provide pathways for slow bulk oxidation of Fe. We further confirm that the interface between h-BN and metallic Fe can be recovered by vacuum annealing at ∼600 °C, although this is accompanied by the creation of defects within the h-BN film. We discuss the importance of these findings in the context of integrated manufacturing and transfer-free device integration of h-BN, particularly for technologically important applications where h-BN has potential as a tunnel barrier such as magnetic tunnel junctions.

Boron-Doped Boron Nitride Photocatalyst for Visible Light-Driven H2 Evolution and CO2 Photoreduction

“…Unlike B-BNO, the porous BNO sample exhibited a prominent shoulder peak in the B 1s spectrum at 193.1 eV after exposure to water, related to boron oxide ( Supplementary Figure 9). [44,[68][69][70] This result is in agreement with the reaction observed and described in the literature, where boron nitride reacts with water to form boron oxide and ammonia. [44,46] Further evidence of the decomposition is shown in Figure 4d, not only by the increase in the oxygen content, but also by the relative percentage of nitrogen decreasing, which is in line with the formation of ammonia.…”

2D Material Membranes for Operando Atmospheric Pressure Photoelectron Spectroscopy

“…Although the choices for membrane support may be limited to materials that can be produced with the required dimensions and strength, these can easily be coated with thin layers of different materials using physical vapor deposition methods in order to eliminate contributions from the underlying material. In this same regard, it is also important to avoid the use of materials that may catalyse the attack of the 2D material under reaction conditions [106,107], which would otherwise undermine the stability of the membrane as discussed further below.…”

Growth andin situcharacterization of 2D materials by chemical vapour deposition on liquid metal catalysts: a review

“…To that end, a series of in situ X-ray characterization studies have been presented, to broaden our knowledge on the key role of substrate engineering for perfect 2DM growth. 30,31,49,[190][191][192][193][194][195] The investigations include alloying, catalyst doping, substrate crystallinity and atom dissolution capabilities. Also, conducting growth under ultra-high vacuum (UHV) conditions, allowed the incorporation of lower temperatures for the observation of surface phenomena.…”