Atomic Layer Epitaxy of h-BN(0001) Multilayers on Co(0001) and Molecular Beam Epitaxy Growth of Graphene on h-BN(0001)/Co(0001)

Abstract

The direct growth of hexagonal boron nitride (h-BN) by industrially scalable methods is of broad interest for spintronic and nanoelectronic device applications. Such applications often require atomically precise control of film thickness and azimuthal registry between layers and substrate. We report the formation, by atomic layer epitaxy (ALE), of multilayer h-BN(0001) films (up to 7 monolayers) on Co(0001). The ALE process employs BCl3/NH3 cycles at 600 K substrate temperature. X-ray photoelectron spectroscopy (XPS) and low energy electron diffraction (LEED) data show that this process yields an increase in h-BN average film thickness linearly proportional to the number of BCl3/NH3 cycles, with BN layers in azimuthal registry with each other and with the Co(0001) substrate. LEED diffraction spot profile data indicate an average BN domain size of at least 1900 Å. Optical microscopy data indicate the presence of some domains as large as ∼20 μm. Transmission electron microscopy (TEM) and ambient exposure studies demonstrate macroscopic and microscopic continuity of the h-BN film, with the h-BN film highly conformal to the Co substrate. Photoemission data show that the h-BN(0001) film is p-type, with band bending near the Co/h-BN interface. Growth of graphene by molecular beam epitaxy (MBE) is observed on the surface of multilayer h-BN(0001) at temperatures of 800 K. LEED data indicate azimuthal graphene alignment with the h-BN and Co(0001) lattices, with domain size similar to BN. The evidence of multilayer BN and graphene azimuthal alignment with the lattice of the Co(0001) substrate demonstrates that this procedure is suitable for scalable production of heterojunctions for spintronic applications.

Hexagonal Boron Nitride Tunnel Barriers Grown on Graphite by High Temperature Molecular Beam Epitaxy

“…In particular we explore a regime of growth using a much higher substrate temperature than previously been investigated 22 and also employ an elemental boron source. In addition the direct growth of hBN on a two-dimensional material (HOPG) offers an alternative to chemical vapour deposition 23 24 25 26 and atomic layer deposition 27 of hBN on metal substrates; this approach must typically be complemented by complex protocols for the removal and transfer of the grown films. We show that the growth of few-layer crystals of hBN on HOPG is possible and, furthermore, that for the high substrate temperature which we use, the grown layers act as tunnel barriers with a resistance which depends exponentially on layer thickness, and have an optical bandgap of 5.9 eV as determined by ellipsometry, a value which is comparable with bulk material.…”

Site- and spin-dependent coupling at the highly ordered h -BN/Co(0001) interface

“…This may allow formation of an epitaxial (1 × 1) interface with high structural perfection, similarly to the recently studied graphene/Co(0001) interface [39]. Indeed, several works reported formation of h-BN films of different thickness on the Co(0001) surface and confirmed strict orientation of ultrathin h-BN [40][41][42]. However, the crystal structure of the h-BN monolayer on the Co(0001) surface is yet to be studied.…”

Decoupling of graphene from Ni(111) via formation of an interfacial NiO layer

“…For example, implementation of graphene in the present-day scalable semiconducting technology requires its synthesis on insulating or semiconducting substrates. Presently this is only possible on h-BN [7][8][9][10] and Ge [11][12][13][14][15] substrates at the conditions which cannot be easily adapted.…”