The conversion of semimetallic suspended graphene (Gr) to a large-gap semiconducting phase is here realized by controlled adsorption of atomic hydrogen (deuterium) on free-standing nanoporous Gr veils. This approach allows to achieve a very clean and neat adsorption, overcoming any spurious influence associated to the presence of substrates. The effects of local rehybridization from sp2 to sp3 chemical bonding are investigated by combining X-ray photoelectron spectroscopy and high-resolution electron energy-loss spectroscopy (HREELS) with ab-initio based modelling. We find that the hydrogen adatoms on the C sites induce a stretching frequency, clearly identified in the vibrational spectra thanks to the use of the D isotope. Overall, the results are compatible with the predicted fingerprints of adsorption on both sides of Gr corresponding to the graphane configuration. Moreover, HREELS of the deuterated samples shows a sizeable opening of the optical band gap, i.e. 3.25 eV, consistent with the modified spectral density observed in the valence band photoemission. The results are in agreement with ab-initio calculations by GW and Bethe–Salpeter equation approaches, predicting a large quasiparticle gap opening and huge exciton binding energy.
M. G. Betti a, D. Marchiani, A. Tonelli, M. Sbroscia, E. Blundo, M. De Luca, A. Polimeni, R. Frisenda, C. Mariani, S. Jeong, Y. Ito, N. Cavani, R. Biagi, P. N.O. Gillespie, M. A. Hernandez Bertran, M. Bonacci, E. Molinari, V. De Renzi, and D. Prezzi, Dielectric response and excitations of hydrogenated free-standing graphene, Carbon Trends, 12, 100274 (2023).
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