Interaction of metastable molecular oxygen with the dangling bonds of a Si(111)-(7X7) surface

We have investigated the interaction between metastable molecular oxygen an d the adatom dangling bonds modified by the adsorption of atomic oxygen int o the back-bonds of a Si(111)-(7X7) surface. Ultraviolet photoelectron spec troscopy shows that the metastable states increase in intensity faster but with a decrease in its saturated intensity as the coverage of atomic oxygen increases. This result suggests that the number of modified dangling bonds is not the only important factor for the adsorption process of metastable oxygen. Taking into account the observation of modified dangling bonds with different density of states in scanning tunneling microscopy, we conclude that the adsorption of the metastable oxygen species correlates closely wit h the density of states of the dangling bond. (C) 2001 Elsevier Science B.V . All rights reserved.