Dresden 2014 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 50: Oxide and Insulator Surfaces I
O 50.2: Vortrag
Mittwoch, 2. April 2014, 10:45–11:00, WIL A317
Optical Characterization of α-Al2O3(0001) Surface Structure and Reactivity in Ambient Conditions — •Yujin Tong, Harald Kirsch, and R. Kramer Campen — Fritz-Haber-Institut, Abt. Physikalische Chemie, 14195 Berlin, Germany
The surface chemistry of alumina is important in fields such as heterogeneous catalysis, geo- and environmental chemistry. Often these surfaces are not merely passive participants in interfacial chemistry: reaction between species present in adjoining phases at the surface can lead to correlated changes in surface structure and reactivity. While much important chemistry at alumina surfaces occurs in ambient conditions, simultaneously probing surface reconstruction and reactivity in these environments is challenging. In this study, we employ surface specific vibrational sum frequency (VSF) spectroscopy to characterize the reaction of water with the the α-Al2O3(0001) surface in ambient conditions. Starting with a Al-terminated surface prepared under UHV in the absence of water, we use the evolution of the interfacial OH stretch spectral response to track the presence of dissociatively adsorbed water and that of the surface phonon spectral response to track the accompanying surface reconstruction. All changes in spectral observables are clearly shown to be reversible on heating. We demonstrate that the observed phonon modes are surface specific by their frequencies and symmetry and assign them based on comparison to computation.