Abstract
We demonstrate direct epitaxial growth of high-quality hexagonal boron nitride (hBN) layers on graphite using high-temperature plasma-assisted molecular beam epitaxy. Atomic force microscopy reveals mono- and few-layer island growth, while conducting atomic force microscopy shows that the grown hBN has a resistance which increases exponentially with the number of layers, and has electrical properties comparable to exfoliated hBN. X-ray photoelectron spectroscopy, Raman microscopy and spectroscopic ellipsometry measurements on hBN confirm the formation of sp2-bonded hBN and a band gap of 5.9 ± 0.1 eV with no chemical intermixing with graphite. We also observe hexagonal moiré patterns with a period of 15 nm, consistent with the alignment of the hBN lattice and the graphite substrate.
Highlights
To date, most studies of graphene-hexagonal boron nitride (hBN) heterostructures have been carried out on devices which are made by stacking graphene layers exfoliated from highly-ordered pyrolytic graphite (HOPG) and hBN layers exfoliated from high-quality hBN crystals[15]; these structures are stabilised by van der Waals forces
We demonstrate that a van der Waals graphite/hBN heterostructure can be grown using high-temperature plasma-assisted molecular beam epitaxy (MBE) and that this approach provides a promising route to the formation of stacked layered materials with optical and electronic properties comparable with layers exfoliated from bulk hBN
We show that the growth of few-layer crystals of hBN on HOPG is possible and, 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
Summary
Yong-Jin Cho1,†, Alex Summerfield[1], Andrew Davies[1,2], Tin S. We demonstrate that a van der Waals graphite/hBN heterostructure can be grown using high-temperature plasma-assisted molecular beam epitaxy (MBE) and that this approach provides a promising route to the formation of stacked layered materials with optical and electronic properties comparable with layers exfoliated from bulk hBN. We show that the growth of few-layer crystals of hBN on HOPG is possible and, 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 This development, combined with recent successes in growing graphene on hBN16,28,29, including growth by MBE30, offers the prospect for the growth of multilayer graphene-hBN heterostructures to produce a wide variety of quantum well, superlattice and tunnelling devices for future scalable technologies.
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