Abstract
Copper foil is the most promising catalyst for the synthesis of large-area, high-quality monolayer graphene. Experimentally, it has been found that the Cu substrate is semi-molten at graphene growth temperatures. In this study, based on a self-developed C–Cu empirical potential and density functional theory (DFT) methods, we performed systematic molecular dynamics simulations to explore the stability of graphene nanostructures, i.e., carbon nanoclusters and graphene nanoribbons, on semi-molten Cu substrates. Many atomic details observed in the classical MD simulations agree well with those seen in DFT-MD simulations, confirming the high accuracy of the C–Cu potential. Depending on the size of the graphene island, two different sunken-modes are observed: (i) graphene island sinks into the first layer of the metal substrate and (ii) many metal atoms surround the graphene island. Further study reveals that the sinking graphene leads to the unidirectional alignment and seamless stitching of the graphene islands, which explains the growth of large single-crystal graphene on Cu foil. This study deepens our physical insights into the CVD growth of graphene on semi-molten Cu substrate with multiple experimental mysteries well explained and provides theoretic references for the controlled synthesis of large-area single-crystalline monolayer graphene.
Highlights
Following its first preparation by exfoliation from graphite in 2004, graphene has attracted much attention both for fundamental studies and technological applications, owing to its unique morphology and excellent mechanical, electronic and optical properties
Great efforts have been made to synthesize large single-crystalline graphene (SCG) monolayers[2,3,4] on transition metal catalyst through chemical vapor deposition (CVD) growth —the most promising, cheap and readily accessible synthetic approach so far reported for graphene[5]
In our molecular dynamics (MD) simulations, only the top layer Cu atoms melt while other layers of the substrate remains in a crystalline shape even at 1450 K owning to the approach of semi-infinite surface adopted in our model
Summary
Following its first preparation by exfoliation from graphite in 2004, graphene has attracted much attention both for fundamental studies and technological applications, owing to its unique morphology and excellent mechanical, electronic and optical properties. To circumvent the formation of these detrimental defects created during the initial stages of growth, defect-free polycyclic aromatic hydrocarbons (PAHs consisting of six-membered carbon rings) have been proposed as ideal precursors for the fabrication of graphene with low defect concentration, on Au (111)[24], Pt (111)[25] and Cu (111)[26] Among these different carbonaceous motifs, the coronene-like cluster, C24, is widely regarded as the ideal carbon precursor for the growth of high-quality graphene by selfassembly on a Cu (111) surface[27,28] due to its six-fold rotation symmetry and dome-shaped structure, a result of the interaction of the peripheral atoms of the carbon cluster with the substrate metal[29,30,31]. The embedded graphene tends to be unidirectionally aligned and the seamless stitching of the adjacent graphene grains is preferred
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