Interaction of Ammonia with Chemically Modified Ru(001) Surfaces

Abstract

The interaction of ammonia with the Ru(001)-(√3×√3)R30°−N, Ru(001)-p(2×2)−0, and Ru(OO1)- p(1×2)−0 surfaces has been investigated by using thermal desorption mass spectrometry and low-energy electron diffraction and compared with the interaction of ammonia with the initially clean Ru(OOl) surface. Ammonia adsorbs and desorbs reversibly on all four surfaces with no detectable decomposition. The ammonia-surface binding energy is increased on the nitrogen-modified surface relative to the clean Ru-(001) surface, and the binding energy is further increased on the oxygen-modified surfaces. On the Ru-(001)-(√3×√3)R30°-N surface at a temperature of 245 K, with a fractional coverage of ammonia of approximately 0.1, the (√3×√3)R30°-N low-energy electron diffraction (LEED) pattern transforms into a (2X2) LEED pattern. Following ammonia desorption the (√3×√3)R30°-N superstructure can be retrieved by annealing the surface. Ammonia forms an ordered p(2×2) overlayer on the clean surface. No ordered overlayers due to the presence of ammonia are observed, however, on any of the chemically modified surfaces. © 1991 American Chemical Society. All rights reserved.