Coexisting 1D and 2D wave patterns in graphene
Highly anisotropic substrate induces coesixtence of double corrugation in epitaxial graphene.D. Perco et al., Carbon 147, 215012 (2025)
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One strategy to tailor the electronic properties of graphene is to grow it on different substrates. Depending on lattice mismatch and the strength of the graphene–substrate interaction, this approach can yield either a quasi-freestanding carbon layer, as in graphene on Ir(111) or Pt(111), or strongly corrugated moiré patterns, such as those observed on Ru(0001) and Re(0001). These corrugated moiré structures are widely used as templates for the growth of ordered arrays of single atoms or nanoparticles. In this framework, high-Miller-index surfaces offer an alternative and potentially powerful route for tuning graphene corrugation. To date, however, only spatially isolated one- or two-dimensional corrugation patterns have been reported. In this study, we explore the growth of graphene on Ir(311) (Fig. 1a) by combining complementary surface-sensitive spectroscopies, microscopies, and first-principles theoretical calculations. Graphene was synthesized via thermal decomposition of ethylene. Low-Energy Electron Diffraction (LEED) and Spot Profile Analysis LEED (SPA-LEED) measurements (Fig. 1b,c), performed at the Nanoscale Materials Laboratory of Elettra, revealed diffraction features associated with two distinct superstructures, indicating the presence of different graphene corrugation regimes. Scanning Tunneling Microscopy (STM) images (Fig. 1d) show the coexistence of one-dimensional periodic ripples, with an apparent height of 1.47 Å and a periodicity of 33.7 Å, alongside flatter regions exhibiting a two-dimensional periodic modulation with a much smaller corrugation of approximately 0.4 Å. This dual corrugation morphology is further supported by High-Resolution X-ray Core Level Spectroscopy measurements carried out at the SuperESCA beamline. The C 1s core-level spectrum (Fig. 1e) can be fitted with three components, corresponding to three families of non-equivalent carbon atoms, consistent with variations in the local C–Ir interaction strength. Carbon atoms located on the ripples interact weakly with the substrate and display binding energies comparable to those observed for graphene on Ir(111). In contrast, carbon atoms in the flatter regions experience different interaction strengths depending on their registry with first- or second-layer Ir atoms. Notably, the latter exhibit a shift toward higher binding energies. The pronounced buckling of carbon atoms within the rippled regions leads to the absence of a well-defined π band in the graphene electronic structure. Density Functional Theory (DFT) calculations reproduce the experimentally observed double-corrugation pattern and reveal enhanced electron charge localization beneath carbon atoms positioned directly above first-layer Ir atoms, a feature absent for carbon atoms on the ripples. |
This result, together with the higher C 1s binding energies and the elongation of C–C bonds in the flatter regions, points to a partial rehybridization of carbon orbitals toward sp³ character. Conversely, the reduced C–C bond lengths observed for carbon atoms on the ripples indicate compressive strain within the graphene lattice. Retrieve article Anisotropy-driven double corrugation: Coexistence of one- and two-dimensional wave patterns in epitaxial graphene on iridium Deborah Perco, Monica Pozzo, Marco Bianchi, Paolo Lacovig, Francesco Sammartino, Philip Hofmann, Silvano Lizzit, Dario Alfè and Alessandro Baraldi Carbon 147, 215012 (2025) |
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