Lateral heterostructures of hexagonal boron nitride and graphene: BCN alloy formation and microstructuring mechanism

Abstract

Integration of individual two-dimensional materials into heterostructures is a crucial step which enables development of new and technologically interesting functional systems of reduced dimensionality. Here, well-defined lateral heterostructures of hexagonal boron nitride and graphene are synthesized on Ir(111) by performing sequential chemical vapor deposition from borazine and ethylene in ultra-high vacuum. Low-energy electron microscopy (LEEM) and selected-area electron diffraction (µ-LEED) show that the heterostructures do not consist only of hexagonal boron nitride (an insulator) and graphene (a conductor), but that also a 2D alloy made up of B, C, and N atoms (a semiconductor) is formed. Composition and spatial extension of the alloy can be tuned by controlling the parameters of the synthesis. A new method for in situ fabrication of micro and nanostructures based on decomposition of hexagonal boron nitride is experimentally demonstrated and modeled analytically, which establishes a new route for production of BCN and graphene elements of various shapes. In this way, atomically-thin conducting and semiconducting components can be fabricated, serving as a basis for manufacturing more complex devices. arXiv:1806.03892v1 [cond-mat.mes-hall]

Broad background in electron diffraction of 2D materials as a signature of their superior quality

“…In order to gain more insight into the origin of the BSC, we synthesize a more complex 2D system composed of laterally extended hBN, hBCN and Gr domains. Such system can be realized by performing sequential CVD with borazine and ethylene precursors, as described in detail in [19]. The resulting structure is shown in a LEEM image in figure 2(a).…”

“…For a correct interpretation of the results related to the heterostructure shown in figures 2 and 3, it is important to understand its electronic and crystal structure. As already elaborated in [19], the heterostructure consists of hBN and Gr regions, each of them with a well-defined crystallography characteristic of epitaxial hBN and Gr on Ir(111). Such crystallography can be inferred from the corresponding μ-LEED patterns in figure 2(c) and (e) (see also figure S1 in the supplementary information).…”

“…Single-layer hBN and lateral hBN-hBCN-Gr heterostructures were grown on a Ir(111) single-crystal surface in an ultra-high vacuum (UHV) LEEM at the University of Duisburg-Essen. The Ir crystal was cleaned by Ar sputtering at 2 keV, oxygen glowing at 1170 K and annealing at 1470 K. Chemical vapor deposition (CVD) from a borazine (B 3 H 6 N 3 ) precursor was used for hBN growth at 1170 K, and two sequential CVD process steps at 1170 K from borazine and ethylene (C 2 H 4 ) precursors were used for the synthesis of heterostructures, as described in detail in [19]. The sample temperature was measured with an infrared pyrometer.…”

Interplay of Kinetic Limitations and Disintegration: Selective Growth of Hexagonal Boron Nitride and Borophene Monolayers on Metal Substrates

“…The pattern exhibits 3-fold symmetry reflecting the underlying symmetry of the Ir(111) substrate and the 3-fold symmetry of the h BN layer . It is well-known that many 2D systems form moiré networks as result of the different lattice spacing and possible rotation of the 2D layer and substrate. ,− For h BN on Ir(111) such moiré pattern has been observed in diffraction ,,− and STM. , In the SPA-LEED images of Figure the unambiguous identifier of such h BN related moiré pattern is a hexagonal network of satellite spots surrounding the (00) spot and all integer order diffraction spots.…”

Spontaneous liquid water dissociation on hybridised boron nitride and graphene atomic layers from ab initio molecular dynamics simulations

“…Indeed, experimental routes to produce hybrid composites of BN and G have been pioneered by Ci and coworkers [3] and recently summarized in a review [4]. Precisely several routes of synthesis have emerged either from bulk copolymerisation [5] or from growing catalytically on a variety of pure and alloy metal substrates, such as Cu [610], Ru [1113], Rh [14], Ir [15,16], Pt [17] or Cu-Ni alloy [18]. The latter fabrication of metal-supported monolayers are being obtained with high levels of control being reported on the nanometer scale thanks to the Scanning Tunneling Microscopy (STM) probe and sometimes real-time Low Energy Electron Microscopy (LEEM).…”