AVS 47th International Symposium
    Surface Science Wednesday Sessions
       Session SS2+VT-WeA

Paper SS2+VT-WeA5
Precursor-mediated Dissociation and Trapping Desorption of Oxygen on Cu(001)-2@sr@2x@sr@2-O

Wednesday, October 4, 2000, 3:20 pm, Room 209

Session: Adsorption and Desorption Phenomena I
Presenter: M. Yata, National Research Institute for Metals, Japan
Authors: M. Yata, National Research Institute for Metals, Japan
Y. Saitoh, National Research Institute for Metals, Japan
Correspondent: Click to Email
The adsorption and desorption of oxygen on Cu(001)-2@sr@2x@sr@2-O has been studied by molecular beam method. Angular and time-of flight distributions have been measured for scattering oxygen from the surface. The time-of flight distributions can be fitted by nonshifted Boltzmann distributions. This means that the oxygen molecules are trapped at the surface in a precursor state and subsequently desorb from the surface. The translational temperature of the desorbing oxygen is lower than the surface temperature, which suggests that there is no barrier for desorption from the precursor state. The dissociative sticking probability of oxygen increases as the translational energy of incident oxygen decreases. This probability also increases with increasing surface temperature. These results suggest that the adsorption of oxygen on the Cu(001)-2@sr@2x@sr@2-O surface proceeds via a precursor-mediated dissociation process rather than by a direct activation process. This is contrast to the dissociative adsorption of oxygen on clean Cu(001) in which the dissociation occurs by direct collisional activation. There exists a competition between dissociation reaction and desorption once the oxygen molecule is trapped in the precursor state. We have estimated the difference in activation energies between the dissociation and desorption of 330 meV. The effect of tensile stress on the dissociative adsorption reaction of oxygen on the Cu(001)-2@sr@2x@sr@2-O surface will be also discussed.