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 N2 and atomic oxygen) is observed between 96 and 200 K. There are two desorption peaks of N2 at 170 and 120 K. The saturated amount of N2 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 N2 is saturated. The desorption peak at 170 K is due to desorption of adsorbed N2 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 N2 by decomposition of molecular N2O at oxygen-modified step sites.