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The thinnest carpet on the smallest atomic staircase

We have grown a single-layer graphene on a stepped Rh(533) surface. The geometry of the substrate leads to an anisotropic moirè cell with the steps playing a key role in improving the structural quality and thermal stability of the carbon layer.

B. Casarin et al.J. Phys. Chem. C  118, 6242 (2014).
The capability of modifying the structure, and hence the electronic properties, of graphene is among the key goals of the scientific community interested in the employment of this material for a variety of nanotechnologically relevant applications. Chemical vapour deposition, which has proven one of the most effective methods for synthesising high-quality epitaxial graphene, has been widely utilised, along with other deposition techniques, to achieve a fine-tuning of the electronic properties of graphene, by exploiting the variable interaction strength developed by graphene with the specific metal support. Methods like the doping of the so-obtained graphene layers with selected elemental species, the intercalation of guest/foreign metal atoms, the growth of interface oxide layers, and the use of bimetallic alloy substrates have proven effective in modifying the structural properties of graphene by altering its interaction with the substrate. Also surfaces characterised by structural anisotropies, like vicinal surfaces or substrates with non-close packed geometries, have been widely used to modify the morphology of the carbon layer, which leads to significant changes in the electronic properties of the system.
In this work we employed the vicinal (533) termination of Rh, which is commonly considered a strongly interacting metal for graphene epitaxy, to grow single graphene layers with a moirè cell whose lattice vector in the direction parallel to the steps is identical to that of GR/Rh(111), while in the other crystallographic direction it is determined by the specific periodicity of the steps. The system was investigated by low energy electron diffraction and high-energy resolution core level photoelectron spectroscopy. 
The measurements were carried out at the Surface Science Laboratory (Physics Department of the University of Trieste and Elettra) and at the SuperESCA beam line of Elettra. Thanks to the particular morphology of the substrate, the so-obtained carbon layer, which forms a single domain on the surface, exhibits a weaker interaction with the metal substrate and an improved thermal stability compared to the C layer grown on the flat Rh(111) surface. Based on our results, we believe the superior structural quality of graphene on the stepped Rh(533) surface is linked to the presence of the steps, which play a crucial role in mediating a thermally-induced defect healing mechanism, so far only predicted by theoretical calculations. Our findings ultimately suggest the possibility of synthesising high-quality, thermally stable GR layers where the periodicity of the moiré cell in the direction orthogonal to the steps can be tailored by selecting a transition metal vicinal surface with the desired morphology.

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The thinnest carpet on the smallest staircase: the growth of graphene on Rh(533);
B. Casarin, A. Cian, Z. Feng, E. Monachino, F. Randi, G. Zamborlini, M. Zonno, E. Miniussi, P. Lacovig, S. Lizzit, and A. Baraldi
J. Phys. Chem. C 118, 6242 (2014)

Ultima modifica il Martedì, 26 Novembre 2019 20:27