Unravelling the roles of surface chemical composition and geometry for the graphene–metal interaction through C1s core-level spectroscopy

Abstract

We study the interplay between competitive substrate-C interaction processes occurring during chemical vapour deposition (CVD) of ethylene on Re(0001). At T < 500 K dissociative ethylene adsorption leads to the formation of a dimer species, producing an ordered (4 × 2) structure. In the range 500 − 700 K, the formation of a high-quality single-layer of graphene (GR) is strongly opposed by the formation of a surface carbide characterised by C trimer units, and, at higher temperatures, by carbon dissolution into the bulk. Our experimental and theoretical results demonstrate that, under UHV conditions, the formation of a long-range ordered GR layer on * Corresponding author. Tel.(+39)040 375-8719. E-mail:alessandro.baraldi@elettra.eu Preprint submitted to CarbonDecember 12, 2013Re(0001) without carbon bulk saturation is confined to a narrow window of growth parameters: substrate temperature, hydrocarbon gas pressure and exposure time. Our combined experimental and theoretical approach allowed us to validate a concept which had already been anticipated in some earlier works on Rh,Fe and Ni, namely that the epitaxial growth of GR is not necessarily restricted to surfaces where carburisation is precluded, but could take place, under given appropriate conditions, also on other metallic substrates exhibiting a strong C-substrate interaction.

Spectroscopic Fingerprints of Carbon Monomers and Dimers on Ir(111): Experiment and Theory

“…The binding energy of the main peak at 284.1 eV is in agreement with previous findings [37][38][39] , while the shoulder at about 284.6 eV could be assigned to carbon atoms in defective configurations 40 .…”

Translucency of Graphene to van der Waals Forces Applies to Atoms/Molecules with Different Polar Character

“…This C 1s BE shift is actually similar to that of the C 1s core level of Gr, which displays two photoemission components when it is supported on Co/Ir(111), both at higher BE with respect to Gr/Ir(111). 34 We can therefore attribute the different C 1s BE of the CO molecules in the two systems to the fact that they are influenced by the doping or the different geometries of the underlying Gr The fit of the desorption curves of component V yields a pre-exponential factor ν = 10 17±2 s −1 , the same which was found for CO/Gr/Ir, yet the adsorption energy in this system is higher, as reported in Table 2. This analysis yields the same value for both the pre-exponential factor, ν = 10 14.8±0.5 s −1 , and for the desorption energy E DES = 136 ± 4 meV, indicating that the lateral inter-atomic interactions are negligible, unlike the case of CO.…”

“…Furthermore, the higher C 1s BE of the V component with respect to the H component reflects the higher C 1s BE of the graphene atoms closest to the surface in Gr/Co/Ir(111). 34 This similarly explains the overall higher BEs of both the C 1s from CO and Ar 2p3 /2 , in the former system, where the C 1s BE of graphene is higher by more than 500 meV than in Gr/Ir(111). It is also interesting to note that if we take as a threshold the This behaviour has been observed also for Xe adsorption on corrugated Gr.…”

“…In fact, as already reported, this effect could be explained either by a direct interaction of CO with the metal below graphene (direct interaction), which would imply that graphene is translucent or transparent to vdW forces, 11,12 or to an indirect mechanism. 14 This, in turn, could be related either to the altered geometry and bond length of graphene when it is corrugated, or to the charge transfer and redistribution induced by the interaction with the substrate, 8,34,41 which is known to induce doping and changes to the work function and potential energy surface not only of Gr, but also of its substrate. [42][43][44] To decouple these different contributions and identify the mechanisms by which the substrate influences the adsorption properties of graphene, we have performed further theoretical calculations, in addition to the ones performed on the systems experimentally investigated 18 (i.e.…”

Interfacial two-dimensional oxide enhances photocatalytic activity of graphene/titania via electronic structure modification

“…In particular, the supporting substrate plays a fundamental role on the degree of Gr doping and therefore represents an opportunity to adjust the properties of Gr-titania hybrid materials by modifying its structure and composition. A powerful strategy to achieve this goal is the intercalation at the Gr-metal interface of any light atoms [29 -31], molecules [32,33], alkali- [34], noble- [35] or transition-metals [36] and oxides [37,38]. Herein, we discuss the growth, the structural/electronic characterization and the photocatalytic activity trends of a novel nano-architecture, which has been designed with the aim to investigate the role of the substrate below Gr on the electronic band structure and alignment of the supported photoabsorbers.…”