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

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.

Nondestructive Thickness Mapping of Wafer-Scale Hexagonal Boron Nitride Down to a Monolayer

“…No studies on thickness determination of mono-or few-layer hBN by ellipsometry exist to our best knowledge, except for a brief mention with limited experimental details. 25 In this work, we first identify the key steps in the sample preparation phase and in the data analysis phase that are necessary in order to obtain reliable results from ellipsometry measurements on 2D hBN. Then, we demonstrate the ability of the ellipsometry technique to map the thickness and continuity of CVD-grown hBN down to monolayer thickness over regions of about 1 cm 2 , which can in principle be extended to any arbitrary area.…”

Transfer‐Free Synthesis of Lateral Graphene–Hexagonal Boron Nitride Heterostructures from Chemically Converted Epitaxial Graphene

“…However, if the topmost layer is free of defects, one might expect that the reaction terminates after total conversion of the first layer, or proceeds layer by layer. This in itself could be a useful approach for producing large area h‐BN layers on top of graphene, and may be useful as a 2D gate dielectric, tunnel barrier, or for encapsulation of epitaxial graphene devices . Furthermore, based on the higher chemical reactivity of monolayer graphene on SiC, due to the influence of the buffer layer, we speculate that the substitution reaction proceeds faster on graphene monolayers compared to multilayers.…”

High-Temperature Molecular Beam Epitaxy of Hexagonal Boron Nitride with High Active Nitrogen Fluxes

“…It is also attracting much attention as a wide band gap semiconductor material for deep-ultraviolet (DUV) applications [ 4 , 5 , 6 ]. There are now attempts world-wide to develop a reproducible technology for the epitaxial growth of large area high-quality hBN layers by chemical vapour deposition (CVD) [ 7 , 8 , 9 ], metal-organic chemical vapor deposition (MOCVD) [ 4 , 5 , 10 , 11 ], and molecular beam epitaxy (MBE) [ 6 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 ].…”

“…We have recently demonstrated high-temperature (HT) plasma-assisted MBE (PA-MBE) of hBN layers on both sapphire and highly oriented pyrolytic graphite (HOPG) substrates [ 22 , 26 , 28 ]. Our results demonstrated that by growing hBN using PA-MBE at HOPG substrate temperatures of ~1400 °C it is possible to produce monolayer and/or few-layer thick boron nitride with atomically flat hBN surfaces, which are essential for future applications.…”

“…Our previous experiments on PA-MBE of hBN layers used a standard nitrogen Veeco radio-frequency (RF) plasma source, and nitrogen flow rates of up to two standard cubic centimetres per minute (sccm), to produce a flux of active nitrogen [ 22 , 26 , 28 ]. Recently, there have been active efforts from the main MBE companies to increase the efficiency of their nitrogen RF plasma sources and to achieve higher MBE growth rates for AlGaInN-based alloys [ 33 , 34 , 35 , 36 , 37 ].…”