Oxidising and carburising catalyst conditioning for the controlled growth and transfer of large crystal monolayer hexagonal boron nitride

Abstract

Hexagonal boron nitride (h-BN) is well-established as a requisite support, encapsulant and barrier for 2D material technologies, but also recently as an active material for applications ranging from hyperbolic metasurfaces to room temperature single-photon sources. Costeffective, scalable and high quality growth techniques for h-BN layers are critically required. We utilise widely-available iron foils for the catalytic chemical vapour deposition (CVD) of h-BN and report on the significant role of bulk dissolved species in h-BN CVD, and specifically, the balance between dissolved oxygen and carbon. A simple pre-growth conditioning step of the iron foils enables us to tailor an error-tolerant scalable CVD process to give exceptionally large h-BN monolayer domains. We also develop a facile method for the improved transfer of as-grown h-BN away from the iron surface by means of the controlled humidity oxidation and subsequent rapid etching of a thin interfacial iron oxide; thus, avoiding the impurities from the bulk of the foil. We demonstrate wafer-scale (2") production and utilise this h-BN as a protective layer for graphene towards integrated (opto-)electronic device fabrication.

Quantum Emitter Localization in Layer-Engineered Hexagonal Boron Nitride

“…This highlights that for the given conditions the hBN is sufficient to protect the underlying graphene from excessive damage, in line with previous reports on excellent graphene protection by ML hBN from remote oxygen plasma. 41 The improved stability of the designed trilayer increases the cumulative intensity of the emission sites and therefore their probability of being identified. However, the intensities of each individual emitter and the background are not significantly different from the monolayer to the trilayer sample (see SI, Figure S9).…”

“…Here, we report a bottom-up assembly approach based on individually processed monolayers (ML) to achieve scalable, planar emitter localization in hBN in all three dimensions. We thereby build on recent progress in the chemical vapor deposition (CVD) of large-area, highly crystalline graphene and hBN MLs and matched transfer approaches. − We establish pretreatment processes for CVD hBN MLs to either fully suppress or activate emission, to be able to utilize such differently treated MLs as select building blocks. We show that known emitter bleaching in air of ML hBN , can be suppressed by sandwiching between two protecting hBN MLs.…”

Plasma‐Enhanced Atomic Layer Deposition of Al2O3 on Graphene Using Monolayer hBN as Interfacial Layer

“…Graphene was grown by introducing a CH 4 /H 2 /Ar mixture (1.2 × 10 -2 , 9, and 41 mbar, respectively) for 6 h. Monolayer hBN was grown by CVD on Fe foils as described in prior work. [47][48][49] Briefly, 0.1 mm Fe foils (99.8% purity) were oxidized in air at 350 °C for 5 min, followed by annealing in 1 × 10 -2 mbar Ar at 980 °C for 20 min to remove localized impurities in the foil and create a minute oxygen reservoir. A brief reducing treatment of 3 × 10 −3 mbar acetylene was applied for 5 min, followed by a 20 min dose of ammonia at 1 × 10 -2 mbar.…”

“…It was confirmed in previous works using Raman spectroscopy, X‐ray photoelectron spectroscopy, and transmission electron microscopy that these films are monolayer films of hexagonal boron nitride. [ 48,49,52 ]…”

“…It was confirmed in previous works using Raman spectroscopy, X-ray photoelectron spectroscopy, and transmission electron microscopy that these films are monolayer films of hexagonal boron nitride. [48,49,52] Electrical Measurements: The electrical properties of the graphene film and of the dielectric were measured in double-gated graphene…”