AVS 49th International Symposium
    Surface Science Wednesday Sessions
       Session SS-WeP

Paper SS-WeP13
LEED and HREELS Study of Methane Physisorbed on Ag(111)

Wednesday, November 6, 2002, 11:00 am, Room Exhibit Hall B2

Session: Surface Science Poster Session
Presenter: M. Sakurai, Kobe University, Japan
Authors: M. Sakurai, Kobe University, Japan
T. Nanba, Kobe University, Japan
Correspondent: Click to Email
The structure of methane monolayer physisorbed on a Ag(111) surface was observed by LEED. The picture was recorded with suppressed electron current using cooled CCD camera in order to minimize the electron stimulated desorption of adsorbed methane. We have observed that the anomalous feature in the IV curve of very low energy electron scattered from this system at 40K depends on the ambient pressure of methane, with which the physisorbed layer is in equilibrium. By the present measurement, the LEED pattern indicated that the lattice of methane molecules forms hexagonal structure with rotationally commensurate direction with the substrate lattice. The LEED spots were somewhat obscure and had broadened nature in azimuthal direction at the equilibrium conditions; however, they became sharp ones when the substrate was cooled to 25K. We have also performed vibrational spectroscopy of adsorbed methane molecules by HREELS and anomaly in the vibrational excitation cross section (i.e. inelastic IV curve) has been observed. The relation between the IV curve and structure will be discussed.