Chemisorption, surface structural chemistry, and electron impact properties of carbon monoxide on Ru(101)

The adsorption, desorption, surface crystallography, and behaviour under electron impact of CO on the 'non-unique' Ru(101) surface have been studied by LEED, Auger spectroscopy, and thermal desorption. CO adsorbs on clear Ru(101) at 300 K with an initial sticking probability of 0.6 producing an ordered phase, designated (11,30), which reaches its maximum degree of perfection at saturation coverage. The structure proposed for the (11,30) phase corresponds to a coverage of 2/3 and contains equal populations of two distinct types of chemisorbed CO (α and β); this is consistent with the observed desorption spectra. Both α and β CO undergo desorption and dissociation by electron impact, with desorption playing the major role. Total cross sections for desorption and dissociation are obtained by Auger spectroscopy, and the relationship between the various partial cross sections is deduced from thermal desorption data. Deposition of surface carbon, by electron impact decomposition of CO, blocks the surface to adsorption of both α and β-CO, but the effect on the latter is the most pronounced. The structure of the real Ru(101) surface is discussed in relation to three possibilities, which are examined in the light of the available data. (Auth.)