Berlin 2012 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 34: Poster Session I (Graphene; Plasmonics and nanooptics; Coherence and coherent control in nanophotonics and plasmonics)

O 34.21: Poster

Dienstag, 27. März 2012, 18:15–21:45, Poster E

Interaction of Water Molecules with Graphene — •Sebastian Standop, Thomas Michely, and Carsten Busse — II. Physikalisches Institut, Universität zu Köln

Graphene is a promising candidate as an electrode material in future electronics including ultracapacitors [1] and dye sensitized solar cells [2]. With the potential of graphene to be used in electrochemical applications it is of great interest to understand in detail structure as well as adsorption kinetics and energetics of water on graphene. Therefore we dosed water onto a graphene covered Ir(111) surface and performed both scanning tunneling microscopy (STM) and thermal desorption spectroscopy (TDS). For low coverages adsorbed at 20 K the water layer shows zero order desorption with an high temperature shoulder increasing with coverage, eventually leading to a complete suppression of the initial peak in favor of the high temperature structure. When elevating the adsorption temperature above 100 K the formation of the second structure is preferred over the low coverage phase indicating its metastable character. We presume that this transition corresponds to a reduced number of dangling bonds within the water layer which is due to the hydrophobicity of the graphene substrate [3]. Our real space analysis corroborates these findings by showing heavy manipulation of the low coverage phase even at 20 K. When increasing the coverage the water molecules organize in extended islands aligned to the inherent moiré supercell of epitaxially grown graphene. [1] C. Liu et al., Nano Lett. 10, 4863 (2010); [2] X. Wang et al., Nano Lett. 8, 323 (2008); [3] G. A. Kimmel et al., J. Am. Chem. Soc. 131, 12838 (2009)