Dresden 2017 – scientific programme

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O: Fachverband Oberflächenphysik

O 72: Oxide and Insulator Surfaces: Adsorption I

O 72.5: Talk

Wednesday, March 22, 2017, 11:30–11:45, WIL C107

STM study of water adsorption on crystalline Cu2O films — •Christoph Möller and Niklas Nilius — Institute of Physics, Carl von Ossietzky University, 26111 Oldenburg, Germany

A direct band gap of 2.1 eV makes cuprous oxide a promising material for the photocatalytic splitting of water. To explore elementary processes associated with this reaction, we have prepared Cu2O(111) thin films on an Au(111) support and investigated them by low-temperature STM. Water exposure below 100 K gives rise to a weakly-bound, physisorbed state of water that cannot be imaged with STM. After annealing to 200 K, a chemisorbed state is reached and small, magic H2O clusters as well as extended, flat islands appear on the surface at dosages below and above 0.1 ML, respectively. Although water islands seem to be amorphous at first glance, protrusions resolved in the STM exhibit a smeared, hexagonal pair-correlation function. Its periodicity of 6 Å matches the Cu2O(111) lattice parameter, suggesting that the molecules populate characteristic sites on the oxide surface, e.g. low-coordinated Cu ions. Further insight into water binding comes from TDS measurements performed on the same system.