Self-assembly of nanoscale lateral segregation profiles

Stania, Roland; Heckel, Wolfgang; Kalichava, Irakli; Bernard, Carlo; Kerscher, Tobias; Cun, Huanyao; Willmott, P. R.; Schönfeld, B.; Osterwalder, Jürg; Müller, Stefan; Greber, Thomas

doi:10.1103/physrevb.93.161402

Cited by 9 publications

(5 citation statements)

References 43 publications

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“…The intercalation of other metals, such as like Au, was studied [1069]. On the binary transition metal PtRh it was found that the nanomesh unit cell may be tuned from 3.2 to 2.7 nm when increasing the substrate lattice constant from Rh to PtRh [1070].…”

Section: Vii11 Growth Of H-bn On Metal Surfacesmentioning

confidence: 99%

Production and processing of graphene and related materials

et al. 2020

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We present an overview of the main techniques for production and processing of graphene and related materials (GRMs), as well as the key characterization procedures. We adopt a ‘hands-on’ approach, providing practical details and procedures as derived from literature as well as from the authors’ experience, in order to enable the reader to reproduce the results. Section is devoted to ‘bottom up’ approaches, whereby individual constituents are pieced together into more complex structures. We consider graphene nanoribbons (GNRs) produced either by solution processing or by on-surface synthesis in ultra high vacuum (UHV), as well carbon nanomembranes (CNM). Production of a variety of GNRs with tailored band gaps and edge shapes is now possible. CNMs can be tuned in terms of porosity, crystallinity and electronic behaviour. Section covers ‘top down’ techniques. These rely on breaking down of a layered precursor, in the graphene case usually natural crystals like graphite or artificially synthesized materials, such as highly oriented pyrolythic graphite, monolayers or few layers (FL) flakes. The main focus of this section is on various exfoliation techniques in a liquid media, either intercalation or liquid phase exfoliation (LPE). The choice of precursor, exfoliation method, medium as well as the control of parameters such as time or temperature are crucial. A definite choice of parameters and conditions yields a particular material with specific properties that makes it more suitable for a targeted application. We cover protocols for the graphitic precursors to graphene oxide (GO). This is an important material for a range of applications in biomedicine, energy storage, nanocomposites, etc. Hummers’ and modified Hummers’ methods are used to make GO that subsequently can be reduced to obtain reduced graphene oxide (RGO) with a variety of strategies. GO flakes are also employed to prepare three-dimensional (3d) low density structures, such as sponges, foams, hydro- or aerogels. The assembly of flakes into 3d structures can provide improved mechanical properties. Aerogels with a highly open structure, with interconnected hierarchical pores, can enhance the accessibility to the whole surface area, as relevant for a number of applications, such as energy storage. The main recipes to yield graphite intercalation compounds (GICs) are also discussed. GICs are suitable precursors for covalent functionalization of graphene, but can also be used for the synthesis of uncharged graphene in solution. Degradation of the molecules intercalated in GICs can be triggered by high temperature treatment or microwave irradiation, creating a gas pressure surge in graphite and exfoliation. Electrochemical exfoliation by applying a voltage in an electrolyte to a graphite electrode can be tuned by varying precursors, electrolytes and potential. Graphite electrodes can be either negatively or positively intercalated to obtain GICs that are subsequently exfoliated. We also discuss the materials that can be amenable to exfoliation, by ...

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Section: Vii11 Growth Of H-bn On Metal Surfacesmentioning

confidence: 99%

Production and processing of graphene and related materials

et al. 2020

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“…[214] Stania et al, showed the higher interaction of h-BN to Rh (111) persists even when growing h-BN on PtRh (111), resulting in reduced Pt enrichment under the h-BN and these observations were also supported by DFT calculations. [243] Despite the lattice mismatch, a strong crystallographic orientation preference is observed for h-BN domains with minimal rotational misalignment, for example, h-BN domains on a Ru(0001) surface (Figure 10A), [246] and periodic mesh structure of the h-BN is observed consistently across the 0001) (top middle) with periodicity of a few nanometers caused by a corrugation of the h-BN layer to minimize strain caused by the lattice mismatch between substrates. Adapted with permission.…”

Section: H-bn Growth On Noble Metals (Rh Ru Ir)mentioning

confidence: 99%

“…[ 214 ] Stania et al, showed the higher interaction of h ‐BN to Rh(111) persists even when growing h‐ BN on PtRh(111), resulting in reduced Pt enrichment under the h‐ BN and these observations were also supported by DFT calculations. [ 243 ]…”

Section: H‐bn Synthesismentioning

confidence: 99%

A Review of Scalable Hexagonal Boron Nitride (h‐BN) Synthesis for Present and Future Applications

2022

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Ga-N, In-P, etc. Crystalline BN has typically been perceived as a purely synthetic material, [1] however geological findings provide evidence of structures similar to BN in rocks. [2] BN exhibits several stable crystal forms (see Figure 1A), for example, i) sp 3 bonded cubic and wurtzite forms; and ii) sp 2 bonded hexagonal and rhombohedral forms. [3] The cubic BN (c-BN) form has "zincblende" type crystal structure consisting of overlapping fcc cubic lattices consisting of B and N atoms. The c-BN crystal structure is analogous to that of diamond. The wurtzite form of BN (w-BN) is also sp 3 bonded like c-BN, however the wurtzite form consists of a hexagonal lattice with each ring sitting in a boat configuration. The w-BN crystal structure is analogous to that of the rare lonsdaleite, a carbon allotrope formed from graphite under immense heat and pressure. [4] Hexagonal boron nitride (h-BN) is a layered hexagonal crystal (a = 2.505 Å and c = 6.653 Å) belonging to the P6 3 /mmc space group with a structure analogous to that of graphite. [11,12] Alternating B and N atoms are sp 2 bonded in-plane to form a hexagonal lattice and several such layers are stacked to form the bulk h-BN crystal (Figure 1B). [11,12] The BN sp 2 bonding results in strong in-plane σ bonds leading to high in-plane thermal conductivity, chemical stability and strength, while empty π orbitals make h-BN electrically insulating (bandgap ≈ 5.955 eV). [3,13] The in-plane BN bonds exhibit ionic behavior due to the stronger electronegativity of the N atoms and results in layer to layer interactions between h-BN layers leading to AA′ stacking configuration, that is, each N atom in one layer is directly above the B atoms of the next layer (Figure 1B). [14] In addition to AA′ stacking, AB stacking (Bernal stacking) has also been occasionally observed in thin h-BN films even though this is a higher energy configuration. [15,5] Finally, BN is also observed in rhombohedral form (r-BN). Each layer of r-BN is the same crystal structure as that of h-BN (Figure 1A), however r-BN follows an ABC stacking configuration whereby boron still sits atop nitrogen atoms, except layers are offset such that the 1 and 3 atoms (N and N for example) sit atop the 4 and 6 atoms (B and B in this example) of the ring below. [3] Hexagonal boron nitride (h-BN) is a layered inorganic synthetic crystal exhibiting high temperature stability and high thermal conductivity. As a ceramic material it has been widely used for thermal management, heat shielding, lubrication, and as a filler material for structural composites. Recent scientific advances in isolating atomically thin monolayers from layered van der Waals crystals to study their unique properties has propelled research interest in mono/few layered h-BN as a wide bandgap insulating support for nanoscale electronics, tunnel barriers, communications, neutron detectors, optics, sensing, novel separations, quantum emission from defects, among others. Realizing these futuristic applications hinges on scalable cost-effective high-qual...

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“…h-BN monolayers can conveniently be grown by chemical vapour deposition using borazine H 3 (BN) 3 H 3 as precursor on various metal surfaces [67,68]. Depending on the lattice constants and surface atomic structure of the substrate, one obtains epitaxial growth [53,99], moiré structures [57], or mesh-like, strongly corrugated films [13,58,59,61,64,100,101]. Most measurements presented in this work were taken from h-BN/Ni (111).…”

Section: Sample Preparation and Characterisationmentioning

confidence: 99%

“…Therefore, it has been successfully employed to study monolayers and thin films of h − BN on all kinds of surfaces since the pioneering work of the group of Oshima in the 1990s [53][54][55]. During the past few decades, h-BN has been studied as single layers on a large variety of transition metals [56][57][58][59], alloys [60,61], and even insulating substrates like germanium [62] and sapphire [63]. On many surfaces, the lattice mismatch between h-BN and the substrate is not negligible leading to surface reconstructions with large unit cells, the most famous probably being the so-called nanomesh [64][65][66].…”

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confidence: 99%

Dynamics of excited interlayer states in hexagonal boron nitride monolayers

Hengsberger¹,

Leuenberger²,

Schuler³

et al. 2020

J. Phys. D: Appl. Phys.

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Hexagonal boron nitride () is the isoelectronic but insulating counterpart of graphene. Like graphene it can easily be grown as high-quality nanotubes or as single layers on metal surfaces. Both materials can be exfoliated or transferred after single-layer growth from suitable substrates onto new surfaces. In view of electronic devices or optical sensors, for instance, the carrier dynamics in the conduction bands determine the device properties. The band edge of the unoccupied band structure of is dominated by two kinds of states, free-electron-like interlayer or interface states and a flat conduction band valley derived from -states. The measurement of excited states and excited-state lifetimes in is the main topic of the present article with a special focus on the dynamics close to the -point. While the conduction band minimum is strongly localised at the boron sites, the charge density of free-electron-like states is outside the planes and is likely to be important for interactions like charge transfer with adjacent layers and substrates. We will review previous efforts to determine the nature of the bandgap and the band structure of unoccupied states with particular emphasis on but not restricted to single-layer epitaxially grown on a Ni(1 1 1) surface.

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Self-assembly of nanoscale lateral segregation profiles

Cited by 9 publications

References 43 publications

Production and processing of graphene and related materials

Production and processing of graphene and related materials

A Review of Scalable Hexagonal Boron Nitride (h‐BN) Synthesis for Present and Future Applications

Dynamics of excited interlayer states in hexagonal boron nitride monolayers

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