Regensburg 2010 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 58: Surface chemical reactions II
O 58.1: Vortrag
Mittwoch, 24. März 2010, 15:00–15:15, H42
Photoinduced substrate-mediated N2O reduction on MgO/Ag(001) surfaces — •Harald Kirsch1, Philipp Giese1, Christian Frischkorn1,2, and Martin Wolf1,2 — 1Institut für Experimentalphysik, FU Berlin, Arnimallee 14, 14195 Berlin — 2Fritz-Haber-Institut, Abt. Physikalische Chemie, Faradayweg 4-6, 14195 Berlin
We investigate the photochemistry of N2O on in-situ prepeared thin MgO films, grown on an Ag(001) crystal. Structure and growth of the MgO films were characterized by means of LEED and Auger spectroscopy. Our goal is to study if defects are responsible for the photoinduced decomposition of N2O and the subsequent creation of reactive O− sites. After irradiation with a KrF laser (248 nm), we observe an increasing N2 signal together with a decrease of the N2O mass in postirradiation thermal desorption spectra. From the increase of the N2 signal with photon dose we determine a crossection of 3×10−18 cm2. We propose a mechanism where UV photons create electron-hole pairs at defect sites, which are responsible for the reaction. After several cycles of UV induced N2O reduction without subsequent annealing, the observed N2 formation is dramatically reduced, which we interpret as a passivation of the reactive sites via occupation with oxygen.