Anisotropic behavior of hydrogen in the formation of pentagonal graphene domains

Jung, Da Hee; Kang, Cheong; Yoon, Duhee; Cheong, Hyeonsik; Lee, Jin Seok

doi:10.1016/j.carbon.2015.03.034

Cited by 17 publications

(18 citation statements)

References 29 publications

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“…As the electronic properties of pristine graphene are strongly dependent on its size, shape, and edge structures 1 , variously shaped graphene domains with defined edge configurations have attracted considerable attention 2 3 4 . They are expected to provide a pathway toward greater insight into the electronic properties of graphene and, hence, toward device performance optimization 5 6 7 .…”

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confidence: 99%

“…Of the various graphene synthesis techniques, Cu-assisted chemical vapor deposition (CVD) is the most reasonable and appropriate method to produce large-scale and low-defect graphene films 10 11 , since it is highly reproducible and yields high-quality films of controllable thickness and domain shapes 12 13 . Hexagonal graphene domains, which are usually synthesized using a CVD method, are believed to exhibit predominantly zigzag edge symmetry 4 14 . But, graphene domains with anisotropic geometries, such as rectangular 15 and two-lobed curvilinear structures 16 , are expected to exhibit both zigzag and armchair edge structures because the edges exhibit the same configuration if the angles between them are 2 n × 30° ( n = 1, 2, 3, …) 4 14 .…”

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Surface Diffusion Directed Growth of Anisotropic Graphene Domains on Different Copper Lattices

Jung

Kang

Nam

et al. 2016

Sci Rep

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Anisotropic graphene domains are of significant interest since the electronic properties of pristine graphene strongly depend on its size, shape, and edge structures. In this work, considering that the growth of graphene domains is governable by the dynamics of the graphene-substrate interface during growth, we investigated the shape and defects of graphene domains grown on copper lattices with different indices by chemical vapor deposition of methane at either low pressure or atmospheric pressure. Computational modeling identified that the crystallographic orientation of copper strongly influences the shape of the graphene at low pressure, yet does not play a critical role at atmospheric pressure. Moreover, the defects that have been previously observed in the center of four-lobed graphene domains grown under low pressure conditions were demonstrated for the first time to be caused by a lattice mismatch between graphene and the copper substrate.As the electronic properties of pristine graphene are strongly dependent on its size, shape, and edge structures 1 , variously shaped graphene domains with defined edge configurations have attracted considerable attention 2-4 . They are expected to provide a pathway toward greater insight into the electronic properties of graphene and, hence, toward device performance optimization [5][6][7] . The edge geometry significantly affects the p-electron structure at the edge 1,8 ; the zigzag edge in a semi-infinite graphene sheet leads to a localized state and the armchair edge, on the other hand, shows no such localized state 8,9 . Consequently, graphene domains with edges of various geometries can be expected to exhibit unique reactivity, since they display unique physical characteristics such as particular electronic structures and magnetic properties 5 . With the consideration that the reactivity of graphene is governable by edges of various geometries, there have been many efforts to grow variously shaped graphene domains and define their edge structures. Of the various graphene synthesis techniques, Cu-assisted chemical vapor deposition (CVD) is the most reasonable and appropriate method to produce large-scale and low-defect graphene films 10,11 , since it is highly reproducible and yields high-quality films of controllable thickness and domain shapes 12,13 . Hexagonal graphene domains, which are usually synthesized using a CVD method, are believed to exhibit predominantly zigzag edge symmetry 4,14 . But, graphene domains with anisotropic geometries, such as rectangular 15 and two-lobed curvilinear structures 16 , are expected to exhibit both zigzag and armchair edge structures because the edges exhibit the same configuration if the angles between them are 2n × 30° (n = 1, 2, 3, …) 4,14 .Most CVD synthesis of graphene to date has been conducted using methane at either low pressure (LPCVD) or atmospheric pressure (APCVD), with these two conditions reported to produce very different results in terms of the domain shape and the growth mechanism. For instance, graphene domain...

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confidence: 99%

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confidence: 99%

Surface Diffusion Directed Growth of Anisotropic Graphene Domains on Different Copper Lattices

Jung

Kang

Nam

et al. 2016

Sci Rep

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“…Here, we demonstrate a controllable H 2 -induced etching process of graphene crystals to fabricate nanoribbons, and Y-junctions structures with pronounced edges. 35 Highly anisotropy etching of graphene can be achieved owing to significant differences in chemical reactivity of the zigzag and armchair edges. The etching behavior of the synthesized graphene was investigated by annealing at 1000 0 C in a gas mixture of H 2 and Ar.…”

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confidence: 99%

“…26,28 In this prospect, exploring the anisotropic etching behavior of high quality CVD graphene is of great interest to fabricate nanoribbons with distinct edge structure. 35 Highly anisotropy etching of graphene can be achieved owing to significant differences in chemical reactivity of the zigzag and armchair edges. Anisotropic etching of graphene basal plane has been explored with metal catalytic nanoparticles in presence of H 2 , selective oxidation, and water vapor at an elevated temperature.…”

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Formation of graphene nanoribbons and Y-junctions by hydrogen induced anisotropic etching

et al. 2015

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Metal nanoparticles and H 2 induced etching of graphene are of significant interest to synthesis graphene nanoribbons and various other structures with crystallographically defined edges. Here, we demonstrate a controllable H 2 -induced etching process of graphene crystals to fabricate nanoribbons, and Y-junctions structures with pronounced edges. Individual graphene crystals and a continuous films were grown on Cu foil by solid source chemical vapor deposition (CVD) technique. The etching behavior of the synthesized graphene was investigated by annealing at 1000 0 C in a gas mixture of H 2 and Ar. A highly anisotropic etching creates hexagonal holes, nanoribbons and Y-junction graphene with clear edge structures. The distinct graphene edges of individual ribbon create 120° to form a Y-shape structure. The finding can be significant to fabricate well-defined graphene structures with controlled edges for electronic device applications as well as creating in-plane heterostructures with other two dimensional (2D) materials.obtain graphene with regular, zigzag or armchair edge structures. 26,28 In this prospect, exploring the anisotropic etching behavior of high quality CVD graphene is of great interest to fabricate nanoribbons with distinct edge structure. 29 Creating holes with defined edge structure also provide a platform to fabricate in-plane heterostructure with other 2D materials. Anisotropic etching of graphene basal plane has been explored with metal catalytic nanoparticles in presence of H 2 , selective oxidation, and water vapor at an elevated temperature. [30][31][32][33][34] Recently, anisotropic behavior of H 2 in the formation of graphene domains has been also observed, thereby obtaining pentagonal graphene domains with anisotropic growth and etching process. 35 Highly anisotropy etching of graphene can be achieved owing to significant differences in chemical reactivity of the zigzag and armchair edges. This has open new opportunities to control the structure of high quality exfoliated and CVD graphene in large-area for device integration. Again, fabrication of Y-shaped graphene nanoribbons with well-ordered edges can be significant, which is not yet addressed considerably. Theoretical analysis predicted specific properties of the Y-shaped zigzag graphene nanoribbons structure. [36][37][38][39][40] Formation of Y-shaped graphene nanoribbons by anisotropic etching process will enable to fabricate multi-terminal graphene-based nanoelectronic and spintronic devices. 41,42 However, synthesis of Y-shaped graphene nanoribbons with clear edges is significant area of graphene on Cu foil. Figure 5(b) shows formation of Y-shape graphene ribbons structure with edge etching from different directions. The perfect edges of individual ribbon create 120° to form an Y-shape structure. Previously, significant efforts have been made to synthesis Y-shape CNTs owing to its unique electrical properties. 45 The three-terminal Y-junction nanotubes exhibits the gating behavior, characteristic of transistors. Similarly, Y-junct...

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“…To this end there still exists significant interest in understanding the synthesis of graphene in great detail, in particular for synthetic graphene grown over Cu by chemical vapor deposition (CVD). [1][2][3][4][5][6][7][8][9][10][11][12][13] This is because CVD can be scaled up and is compatible within current industrial practice. 14 Most synthetic graphene growth approaches include pretreatment steps to the Cu foil to reduce contamination 15,16 , smoothen the surface 17,18 and control the level of oxidation 19,20 which can help improve grain size and density.…”

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confidence: 99%

Oxidation as A Means to Remove Surface Contaminants on Cu Foil Prior to Graphene Growth by Chemical Vapor Deposition

Pang

Bachmatiuk

et al. 2015

J. Phys. Chem. C

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One of the more common routes to fabricate graphene is by chemical vapor deposition (CVD). This is primarily because of its potential to scale up the process and produce large area graphene. For the synthesis of large area monolayer Cu is probably the most popular substrate since it has a low carbon solubility enabling homogenous single-layer sheets of graphene to form. This process requires a very clean substrate. In this work we look at the efficiency of common pre-treatments such as etching or wiping with solvents and compare them to an oxidation treatment at 1025 o C followed by a reducing process by annealing in H 2 . The oxidation/reduction process is shown to be far more efficient allowing large area homogeneous single layer graphene formation without the presence of additional graphene flakes which form from organic contamination on the Cu surface.

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Anisotropic behavior of hydrogen in the formation of pentagonal graphene domains

Cited by 17 publications

References 29 publications

Surface Diffusion Directed Growth of Anisotropic Graphene Domains on Different Copper Lattices

Surface Diffusion Directed Growth of Anisotropic Graphene Domains on Different Copper Lattices

Formation of graphene nanoribbons and Y-junctions by hydrogen induced anisotropic etching

Oxidation as A Means to Remove Surface Contaminants on Cu Foil Prior to Graphene Growth by Chemical Vapor Deposition

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