Berlin 2015 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 83: Graphene: Adsorption, Intercalation and Doping (organized by O)

TT 83.7: Poster

Mittwoch, 18. März 2015, 18:15–21:00, Poster A

Theoretical NMR signatures of water and ice on graphene — •Achraf Jaadouni, Eva Rauls, Wolf Gero Schmidt, and Uwe Gerstmann — University of Paderborn, Paderborn Germany

Since the discovery of graphene the adsorption of water has been discussed as a possibility for doping [1], while changing the electron mobility surprisingly little. Theoretical studies have shown that the electronic properties of the resulting system strongly depends on the microscopic details of the substrate [2].

In this theoretical work we investigate the influence of thin layers of ice using density functional theory (DFT) whereby van-der-Waals interaction has been taken into account. We demonstrate that an adsorption of at least two layers of ice on free standing graphene results in a charge transfer between the ice and graphene layers and, thus, can lead to a doping of graphene. The sign of the charge transfer and by this the type of doping, however, depends on the orientation of the water molecules. As a consequence, a mixture of two phases can result in a cancellation of the doping effect. Whereas the two configuration differ only slightly in total energies, the NMR chemical shifts calculated for both types of nuclei, O as well as H, are significantly different. Hence, a control of the orientation of the ice layers should be experimentally possible via nuclear magnetic resonance (NMR).

[1] K.S. Novoselov, A.K. Geim, S.V. Morozov, D. Jiang, Y. Zhang, S.V. Dubonos, I.V. Grigorieva, A.A. Firsov, Science 306, 666 (2004).

[2] T.O. Wehling, A.I. Lichtenstein, and M.I. Katsnelson, Appl. Phys. Lett. 93, 202110 (2008).