Peculiar decomposition behavior of N2O on Ni(755)

The adsorption and decomposition behavior of N2O on Ni(755) has been investigated by TPD and XPS. Decomposition of N2O (into N-2 and atomic oxygen) is observed between 96 and 200 K. There are two desorption peaks of N-2 at 170 and 120 K. The saturated amount of N-2 produced from N2O is quite close to the step density of Ni(755). The molecular desorption of N2O occurs only for large exposures of N2O where the desorption peak of N-2 is saturated. The desorption peak at 170 K is due to desorption of adsorbed N-2 which is formed at bare step sites from initial dissociation of N2O below 105 K. On the other hand, the peak at 120 K comes from spontaneous desorption of N-2 by decomposition of molecular N2O at oxygen-modified step sites. (C) 1997 Elsevier Science B.V.