Abstract
Morphological stability of the atomically rough Ru(1121) surface upon annealing in NO2, O2, and NH3 at elevated temperatures has been studied using scanning tunneling microscopy (STM), low energy electron diffraction (LEED), and Auger electron spectroscopy. The surface becomes fully faceted and covered by oxygen after annealing at T ≥ 600 K in NO2 (10(-8) Torr) or O2 (10(-6) Torr). The LEED and STM studies reveal that the faceted surface consists of nanoscale ridges, exposing four facets (1011), (0111), (1010), and (0110) on the ridges, and the ridge size grows as the annealing temperature increases. Details of the facet structures and reconstructions have been observed. However, no evidence is found for faceting of Ru(1121) to occur upon annealing in NH3. Our findings should be important for development of Ru-based catalysts under oxygen-rich conditions.