Operando atomic-scale study of graphene CVD growth at steps of polycrystalline nickel

Abstract

An operando investigation of graphene growth on (100) grains of polycrystalline nickel (Ni) surfaces was performed by means of variable-temperature scanning tunneling microscopy complemented by density functional theory simulations. A clear description of the atomistic mechanisms ruling the graphene expansion process at the stepped regions of the substrate is provided, showing that different routes can be followed, depending on the height of the steps to be crossed. When a growing graphene flake reaches a monoatomic step, it extends jointly with the underlying Ni layer; for higher Ni edges, a different process, involving step retraction and graphene landing, becomes active. At step bunches, the latter mechanism leads to a peculiar 'staircase formation' behavior, where terraces of equal width form under the overgrowing graphene, driven by a balance in the energy cost between C-Ni bond formation and stress accumulation in the carbon layer. Our results represent a step towards bridging the material gap in searching new strategies and methods for the optimization of chemical vapor deposition graphene production on polycrystalline metal surfaces.

Quantum Confinement in Aligned Zigzag “Pseudo‐Ribbons” Embedded in Graphene on Ni(100)

“…This finding is in agreement with STM topography of graphene grown on the (100) face of polycrystalline Ni foils, where no GPR was observed at high temperature. [ 21 ] Thus, starting from the atomistic model of graphene/Ni(100) with 1D moiré presented in Figure 1e, [ 17 ] we propose to place carbon atoms under two adjacent moiré periods in the form of interfacial surface carbide (Ni 2 C) involving a c (2 × 2) clock reconstruction of the topmost Ni layer. [ 22,23 ] This interfacial carbon deactivates the strong electronic interaction previously existing between the graphene C atoms at the trough of one moiré wiggle and the Ni atoms, breaking the hybridization between carbon p z ‐states and nickel d‐states and locally restoring the quasi‐freestanding nature of graphene.…”

Strain release at the graphene-Ni(100) interface investigated by in-situ and operando scanning tunnelling microscopy

“…Gr was synthesized, on both Ni(100) single crystals and polycrystalline Ni foils exhibiting micro-sized (100) grains, via CVD in a UHV chamber (see Methods and refs. [22,26] for details). Within a temperature range between 400 and 550°C, monolayer Gr growth is accompanied by the decomposition of a surface Ni 2 C phase [27][28].…”

Chemical Vapour Deposition of Graphene—Synthesis, Characterisation, and Applications: A Review

“…Ani et al provided an extensive review of the chemical and physical factors affecting the nucleation sites and argued for the advantage of using single crystalline (both Ni and Cu) to produce higher quality graphene [ 115 ]. However, researchers tend to favour developing the use of polycrystalline Ni for its economic advantage [ 135 , 136 , 137 ]. Mogera et al investigated twisted multilayer graphene growth on polycrystalline Ni [ 136 ].…”

“…The more complex junction shown in the graphene/Ni grain boundaries results from the multi-stacking of graphene layers which induces (111) morphology in the polycrystalline Ni. Zou et al also reported on the effect of CVD graphene grown on the underlying layers of polycrystalline Ni [ 137 ]. By observing the graphene growth on Ni(100) crystal steps, Zou et al reported the possibility of growing single graphene crystals even in the presence of bunch steps in the substrate where the graphene grown smooths the substrates surface by introducing monoatomic steps to overcome the bunch step.…”