IUVSTA 15th International Vacuum Congress (IVC-15), AVS 48th International Symposium (AVS-48), 11th International Conference on Solid Surfaces (ICSS-11)
    Surface Science Monday Sessions
       Session SS2-MoA

Paper SS2-MoA10
Synchrotron X-ray Photoelectron Studies of the CCl@sub 4@ Chemistry on Fe@sub 3@O@sub 4@ (111)- 2x2 Surfaces

Monday, October 29, 2001, 5:00 pm, Room 121

Session: Molecular Interactions with Oxide Surfaces
Presenter: K. Adib, Columbia University
Authors: K. Adib, Columbia University
N. Camillone III, Columbia University
J.P. Fitts, Columbia University
Z. Zhu, Columbia University
R.M. Osgood, Jr., Columbia University
S.A. Joyce, Pacific Northwest National Laboratory
D.R. Mullins, Oak Ridge National Laboratory
Correspondent: Click to Email
We have used synchrotron x-ray photoelectron spectroscopy (XPS) and temperature-programmed desorption (TPD) to investigate the reactions of CCl@sub 4@ with Fe@sub 3@O@sub 4@ (111) surfaces. Natural single crystals of @alpha@-Fe@sub 2@O@sub 3@ were cut and polished in the (0001) orientation. They were processed in ultrahigh vacuum to produce a surface selvedge of Fe@sub 3@O@sub 4@ (111)- 2x2 and exposed at ~100 K to CCl@sub 4@. TPD results indicate a highly reactive surface in which the dissociation of CCl@sub 4@ into Cl and CCl@sub 2@ plays an important role. XPS results confirm the presence of three Cl-containing species immediately upon dosing. The data is consistent with presence of unreacted CCl@sub 4@, and chemisorbed CCl@sub 2@ and Cl on the surface. We propose that upon subsequent heating of the surface, the chemisorbed species can (1) abstract an oxygen and desorb as OCCl@sub 2@, (2) associatively desorb as C@sub 2@Cl@sub 4@ or (3) recombinatively desorb as CCl@sub 4@. We have observed differences in the TPD spectra following the initial dosing of the surface as compared to those following subsequent dosings. These marked changes in the surface are explained in terms of incomplete desorption of iron chloride and carbon species upon heating as verified by XPS. At sufficiently high dosages of CCl@sub 4@, the iron chlorides formed on the surface consisted of multiple species, possibly FeCl@sub 2@ and FeCl@sub 3@.