Low-energy electron reflectivity of graphene on copper and other substrates

Abstract

The reflectivity of low energy electrons from graphene on copper substrates is studied both experimentally and theoretically. Well-known oscillations in the reflectivity of electrons with energies 0 -8 eV above the vacuum level are observed in the experiment. These oscillations are reproduced in theory, based on a first-principles density functional description of interlayer states forming for various thicknesses of multilayer graphene. It is demonstrated that n layers of graphene produce a regular series of 1  n minima in the reflectance spectra, together with a possible additional minimum associated with an interlayer state forming between the graphene and the substrate. Both (111) and (001) orientations of the copper substrates are studied. Similarities in their reflectivity spectra arise from the interlayer states, whereas differences are found because of the different Cu band structures along those orientations. Results for graphene on other substrates, including Pt(111) and Ir(111), are also discussed.

Buffer layer free graphene on SiC(0001) via interface oxidation in water vapor

“…LEEM, PEEM and reflectivity curves also give evidence for the intercalation and decoupling of the 6√3. Our observations support a recent re-interpretation of LEEM reflectivity spectra by Feenstra et al [25][26] and Srivastava et al [27].…”

“…The explanation, which is discussed in detail in ref. [27] is that decoupling of the 6√3 allows inter-layer states to form between the substrate and the former 6√3. In the case of water-treated 6√3, the distance between the substrate and the graphene layer seems to be large enough that two inter-layer states are seen in the energy range of the reflectivity spectrum, leading to two dips.…”

“…Here, a commonly accepted explanation of the dips in the reflectivity spectra [24] was recently challenged by Feenstra, Srivastava et al [25][26][27]. The accepted interpretation was that the dips of reflectivity spectra between 0-8 eV are due to the graphite band structure in ΓA direction [24].…”

Modification of electronic surface states by graphene islands on Cu(111)

“…Overall, the change we report qualitatively agrees with theoretical expectations 1 and low energy electron reflectivity results, 28 which report a 0.9 eV and 0.82 eV decrease in work function on gr/Cu, respectively. A priori, the reduction in work function due to the graphene island seems at odds with the n-doping indicated by photoemission, 15,17 but may highlight the distinction between the overall charge transfer and the interfacial dipole responsible for the work function change.…”

Layered Two-Dimensional Heterostructures and Their Tunneling Characteristics

“…As rst discussed by Hibino et al [43,64] and extensively analyzed in our prior work, [48,58,59,65] the occurrence of minima in low-energy electron re ectivity spectra is associated with interlayer states that occur between the 2D planes of van der Waals (vdW) bonded materials. Such interlayer states arise from the image-potential states that exist on either side of a single 2D layer, [66,67] i.e.…”