Dresden 2011 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 78: Surface chemical reactions
O 78.3: Vortrag
Donnerstag, 17. März 2011, 15:30–15:45, WIL B122
Photoinduced generation of defect bound atomic oxygen by N2O dissociation on thin MgO films — •Philipp Giese, Harald Kirsch, Christian Frischkorn, and Martin Wolf — Fritz-Haber-Institut, Abt. Physikalische Chemie, Faradayweg 4-6, 14195 Berlin
Photoinduced dissociation of N2O adsorbed on thin MgO films (4 - 30 monolayers) grown on Ag(100) has been studied with temperature programmed desorption spectroscopy (TPD). After irradiation with 248 nm light from a KrF laser four processes can be identified by postirradiation TPD: Depletion of the initial N2O coverage, generation of molecular nitrogen desorbing at 55 K, tightly bound atomic oxygen desorbing associatively at 550 K and a shift of the N2O and N2 desorption peaks towards higher temperatures. Analysis of the reaction yield as a function of photon exposure confirms a defect driven reaction. However, since the amount of generated atomic oxygen exceeds the amount of generated nitrogen significantly, a second reaction channel with a high nitrogen desorption cross section needs to be incorporated. Our results are interpreted as a reaction mediated by electron hole pair generation at edges of the MgO film followed by electron trapping at defects leading to the N2O dissociation. This interpretation is corroborated by a saturation of the oxygen generation with increasing N2O adsorption on edges.