The adsorption of CO on the (110) plane of tungsten; LEED, XPS, and Auger measurements

Abstract

Adsorption of CO on W(110) at 100 K produces a number of ordered LEED patterns as coverage increases, culminating in a p(5 × 1) pattern for a full virgin CO layer. The beta-1 layer obtained by heating a virgin layer to 400 K has a p(2 × 1) structure. Absolute coverages, obtained by comparison of XPS intensities (and Auger intensities where feasible) with those of oxygen on tungsten at O/ W = 0.5 indicate that CO/W ≅ 0.8 for the full virgin layer and ≅ 0.3 for beta-1. These results, together with the LEED data, indicate that low temperature adsorption of virgin CO is not very site specific, and that beta-1 must be dissociated with C and O lying along alternate closepacked rows of W. XPS results for the oxygen 1s peak show that the latter shifts in beta and beta-1 from its position in virgin CO to an energy equal to that seen for pure oxygen on tungsten. A number of electron impact desorption results are also presented, and the nature of the various binding states of CO on this plane is discussed.