INTERACTIONS OF H2 AND NH3 WITH MO(100) AND MO(100)-C(2X2)N SURFACES

The interactions of H-2 and NH3 With Mo(100) and Mo(100)-c(2 x 2)N surfaces were studied using temperature programmed desorption and Auger electron spectroscopies. For a clean Mo(100) surface, the initial sticking coefficient is 1.0 and the maximum adsorption capacity is 2.0 ML. On the nitrided surface, the sticking coefficient decreases to 0.4 and the maximum capacity decreases to 0.5 ML. The initial sticking coefficient for NH3 on Mo(100) is 0.36, and the saturation adsorption capacity is 0.6 ML. Nitriding the surface reduces the initial sticking coefficient to 0.24 and the saturation capacity to 0.35 ML. Temperature programmed desorption studies show that adsorbed NH3 undergoes desorption and concurrent decomposition, the extent of decomposition being much less significant on the Mo(100)-c(2 x 2)N than on the Mo(100) surface. D2/NH3 coadsorption studies reveal that NH3 decomposition proceeds via a stepwise dehydrogenation process.