Anisotropic Etching of Hexagonal Boron Nitride and Graphene: Question of Edge Terminations

Stehle, Yijing; Sang, Xiahan; Unocic, Raymond R.; Voylov, Dmitry; Jackson, Roderick; Smirnov, Sergei; Vlassiouk, Ivan

doi:10.1021/acs.nanolett.7b02841

Cited by 62 publications

(66 citation statements)

References 41 publications

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“…In principle, functional hierarchical structures can be formed by repeated growth and templating as the grown adlayer can also be used as templates. Finally, it is worth mentioning that our etching experiments of as‐grown samples further demonstrate the correlation between crystal geometry and structure . For example, Figure S11 (Supporting Information) shows three cases of etching.…”

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confidence: 55%

Epitaxial Growth of h‐BN on Templates of Various Dimensionalities in h‐BN–Graphene Material Systems

Chen

et al. 2019

Advanced Materials

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2D in-plane and vertical heterostructures such as graphene and hexagonal boron nitride (h-BN) have drawn wide attention owing to their unique structure and properties over the past years. [1][2][3][4][5][6] Previous studies have explored their controlled growth, detailed interface microstructure, properties, and device applications. [7] For example, the interface of in-plane or vertical heterostructures can be controlled to be atomically sharp or clean at a proper growth condition, and the intriguing properties such as half-metallicity, [8] magnetism, [9] or peculiar boundary states [3,10] have been theoretically predicted or partly confirmed by experiments. On the other hand, the in-plane heterostructure system is also an ideal system for deeply studying related epitaxy behavior and kinetic process beyond conventional A-A or A-B material systems. For example, grapheneh-BN system provides a rich possibility of epitaxial templates with various dimensionalities and interface, such as 2D crystal surfaces, 1D edges, inner 1D grain boundaries (GBs), and 1D interface of graphene-h-BN. Among these possibilities, 1D graphene zigzag (ZZ) edges were previously studied in depth for the epitaxial growth of h-BN. [11,12] While h-BN growth along other various graphene edges fabricated by top-down etching was also demonstrated, graphene edge configurations are essentially unknown. [13,14] However, much less is known about the related kinetic growth of complex epitaxial systems. To date, it is not clear whether the growth of 2D materials on templates of various dimensionalities is allowed in practice, and no effective idea or model is available for describing the complex epitaxial growth kinetics.Here, using a 2D A-B (A: graphene and B: h-BN) system with the freedom of in-and out-of-plane epitaxial growth, we discover a set of new epitaxial growth patterns, spanning from edge-configuration-dependent growth along 1D graphene ZZ to armchair (AC) edges, GB formation by merging materials, 1D GB-or A-B interface-templated growth of adlayer, to adlayer growth on 2D surface template. We further provide, for the first time, a framework that allows the description of various kinetic growths of epitaxial structures by combined geometric and structural modeling. This work provides a general viewpoint for understanding epitaxial growth in complex systems.We started the growth of single crystal hexagonal graphene flakes (HGFs) with desired sizes and densities on liquid Cu surface by modulating experimental parameters such as methane, H 2 , and Ar flow rates. [15] The formed regular monolayer HGFs Epitaxy traditionally refers to the growth of a crystalline adlayer on a crystalline surface, and has been demonstrated in several simple material systems over decades. Beyond this, it is not clear whether the growth of 2D materials on templates of various dimensionalities is possible, and no effective theory or model is available for describing the complex epitaxial growth kinetics. Here a library of hexagonal boron nitride epitaxy is presented on ...

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confidence: 55%

Epitaxial Growth of h‐BN on Templates of Various Dimensionalities in h‐BN–Graphene Material Systems

Chen

et al. 2019

Advanced Materials

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“…However, the actual role of H 2 in CVD process could be more complex than we expected. For instance, H 2 has a great impact on the growth speed and morphology of h-BN domains, and even has etching effect to h-BN edges [54][55][56]. Thus, tuning the GB structures by either tuning H 2 or other methods should be systematically studied further.…”

Section: Discussionmentioning

confidence: 99%

Grain boundaries in chemical-vapor-deposited atomically thin hexagonal boron nitride

Ren

Dong

Yang

et al. 2019

Phys. Rev. Materials

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Large-area two-dimensional (2D) materials for technical applications can now be produced by chemical vapor deposition (CVD). Unfortunately, grain boundaries (GBs) are ubiquitously introduced as a result of the coalescence of grains with different crystallographic orientations. It is well known that the properties of materials largely depend on GB structures. Here, we carried out a systematic study on the GB structures in CVD-grown polycrystalline h-BN monolayer films by transmission electron microscope. Interestingly, most of these GBs are revealed to be formed via overlapping between neighboring grains, which are distinct from the covalently bonded GBs as commonly observed in other 2D materials. Further density functional theory (DFT) calculations show that the hydrogen plays an essential role in overlapping GB formation. This work provides an in-depth understanding of the microstructures and formation mechanisms of GBs in CVD-grown h-BN films, which should be informative in guiding the precisely controlled synthesis of large area single crystalline h-BN and other 2D materials.

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“…The kinetic single crystal Wulff construction allows for shapes beyond the thermodynamic equilibrium by taking into account the growth-directing effects of surfactants, underpotential deposition, or other reaction additives and conditions [ 37 – 42 ]. For instance, Ag underpotential deposition on Au nanoparticles blocks the growth of low-index facets, allowing for rather exotic shapes such as {310}-bound truncated ditetragonal prisms and {720}-bound concave cubes, while poly(vinyl pyrrolidone) (PVP) directs the growth of Ag to preferentially form nanocubes with {100} facets rather than the thermodynamically expected cuboctahedra [ 43 , 44 ].…”

Section: Wulff and Wulff-related Constructionsmentioning

confidence: 99%

Approaches to modelling the shape of nanocrystals

2021

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Unlike in the bulk, at the nanoscale shape dictates properties. The imperative to understand and predict nanocrystal shape led to the development, over several decades, of a large number of mathematical models and, later, their software implementations. In this review, the various mathematical approaches used to model crystal shapes are first overviewed, from the century-old Wulff construction to the year-old (2020) approach to describe supported twinned nanocrystals, together with a discussion and disambiguation of the terminology. Then, the multitude of published software implementations of these Wulff-based shape models are described in detail, describing their technical aspects, advantages and limitations. Finally, a discussion of the scientific applications of shape models to either predict shape or use shape to deduce thermodynamic and/or kinetic parameters is offered, followed by a conclusion. This review provides a guide for scientists looking to model crystal shape in a field where ever-increasingly complex crystal shapes and compositions are required to fulfil the exciting promises of nanotechnology.

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Anisotropic Etching of Hexagonal Boron Nitride and Graphene: Question of Edge Terminations

Cited by 62 publications

References 41 publications

Epitaxial Growth of h‐BN on Templates of Various Dimensionalities in h‐BN–Graphene Material Systems

Epitaxial Growth of h‐BN on Templates of Various Dimensionalities in h‐BN–Graphene Material Systems

Grain boundaries in chemical-vapor-deposited atomically thin hexagonal boron nitride

Approaches to modelling the shape of nanocrystals

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