The adsorption process of metastable molecular oxygen on a Si(111)-(7×7) surface is studied by ultraviolet photoelectron spectroscopy. At 120 K, three metastable states at 2.1, 3.8, and 5.1 eV grow up simultaneously following the decrease of the back-bond state as the dosage increases. After annealing at 600 K, we observed an unusual state attributed to the dangling bond. These results and the symmetries of the molecular orbitals lead to a conclusion that the metastable molecular species is adsorbed on top of an adatom stabilized by a coadsorbed atomic oxygen into the back bond.
|Physical Review B - Condensed Matter and Materials Physics
|Published - 1999