| AVS 62nd International Symposium & Exhibition | |
| Surface Science | Tuesday Sessions |
| Session SS+AS+EN-TuA |
| Session: | Mechanistic Insight of Surface Reactions: Catalysis, ALD, etc. - II |
| Presenter: | Barbara Lechner, Lawrence Berkeley National Laboratory |
| Authors: | B.A.J. Lechner, Lawrence Berkeley National Laboratory S. Maier, Lawrence Berkeley National Laboratory M.B. Salmeron, Lawrence Berkeley National Laboratory |
| Correspondent: | Click to Email |
The growth of water layers on model substrates has been studied intensively, yet many questions still remain [1,2]. After many years of research, the structure of the first wetting layer on metal surfaces has been determined in comprehensive experimental and theoretical studies [3-5]. A surprisingly complex behavior was revealed, showing that the strain caused by the mismatch of the hexagonal planes in the ice crystal structure and the lattice of the substrate is released by forming structures that include rotated hexagons, pentagons and heptagons of molecules, in addition to strongly bound hexagonal rings commensurate with the substrate. A range of experimental and theoretical investigations showed that, on many substrates, the water monolayer does not expose any dangling hydrogen bonds as all water molecules adsorb either flat-lying or with a hydrogen atom pointing towards the surface [1,6]. Growth of multilayer water films that preserve the “down-pointing” average dipole orientation of water has been proposed to occur in some cases, resulting in the formation of “ferroelectric ice” [7]. However, the growth of the entropically more favorable, proton-disordered ice requires flipping some of the molecules in the first layer to expose dangling hydrogen bonds. Such molecular reorientation may be kinetically hindered, and has been invoked to be the reason for the hydrophobic character of many water monolayer films at low temperatures [6].
Here, we present high-resolution scanning tunneling microscopy (STM) measurements of water layers adsorbed on Pt(111) and Ru(0001) to study the transition from the first layer to multilayers. We observe that a second water layer initially grows in an amorphous structure when grown on the crystalline monolayer containing pentagons, hexagons and heptagons of water molecules. To facilitate the growth of ice in a bulk-like hexagonal arrangement, the first wetting layer needs to rearrange into a hexagonal structure commensurate with the surface.
[1] Hodgson, A.; Haq, S. Surf. Sci. Rep.2009, 64, 381–451.
[2] Carrasco, J.; Hodgson, A.; Michaelides, A. Nat. Mater.2012, 11, 667–674.
[3] Maier, S.; Stass, I.; Cerdá, J. I.; Salmeron, M. Phys. Rev. Lett.2014, 112, 126101.
[4] Tatarkhanov, M.; Ogletree, D. F.; Rose, F.; Mitsui, T.; Fomin, E.; Maier, S.; Rose, M.; Cerdá, J. I. J. Am. Chem. Soc.2009, 131, 18425–18434.
[5] Nie, S.; Feibelman, P. J.; Bartelt, N. C.; Thürmer, K. Phys. Rev. Lett.2010, 105, 026102.
[6] Kimmel, G. A.; Petrik, N. G.; Dohnálek, Z.; Kay, B. D.; Kimmel, G. A.; Petrik, N. G.; Dohnálek, Z.; Kay, B. D. J. Chem. Phys.2007, 126, 114702.
[7] Su, X.; Lianos, L.; Shen, Y. R.; Somorjai, G. A. 1998, 1533–1536.