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

Paper SS-TuA1
Scanning Tunneling Microscopy Study of the Reduced Fe@sub 3@O@sub 4@(111) Terminated Selvedge on a Natural Single Crystal @alpha@-Fe@sub 2@O@sub 3@(0001) Surface: Termination and Surface Reaction with Carbon Tetrachloride

Tuesday, October 30, 2001, 2:00 pm, Room 121

Session: Metal Oxides: Structure and Photocatalysis
Presenter: K.T. Rim, Columbia University
Authors: K.T. Rim, Columbia University
J.P. Fitts, Columbia University
T. Muller, Columbia University
K. Adib, Columbia University
N. Camillone, Columbia University
R.M. Osgood, Columbia University
S.A. Joyce, Pacific Northwest National Laboratory
G.W. Flynn, Columbia University
Correspondent: Click to Email
Scanning Tunneling Microscopy(STM) and Low Energy Electron Diffraction(LEED) have been used to study the degradation of CCl@sub 4@ on the reduced surface of a natural @alpha@-Fe@sub 2@O@sub 3@(0001) surface. STM and LEED results indicate that repeated cycles of Ar@super +@ sputtering at 2kV and annealing in vacuum and in 10@super -6@Torr of O@sub 2@ partial pressure at 850K reduces the @alpha@-Fe@sub 2@O@sub 3@(0001) surface. Based on STM images approximately 90 % of the reduced surface is terminated by Fe@sub 3@O@sub 4@(111), while the remaining 10 % is terminated by FeO(111) and an unidentified phase. CCl@sub 4@ vapor was dosed on the reduced surface at room temperature. STM images were obtained at room temperature before and after the surface was exposed to CCl@sub 4@. STM images before dosing CCl@sub 4@ reveal a lateral distance of 6.0±0.5Šbetween atoms and a step height of 4.8±0.5Šbetween terraces. A related Temperature Programmed Desorption(TPD) study on the same surface concludes that CC l@sub 4@ is adsorbed dissociatively on the Fe@sub 3@O@sub 4@(111) terminated surface and that only Cl atoms remain on the surface when the dosed surface is flashed up to 590K. STM images after dosing and flashing up to 590K show bright features on the Fe @sub 3@O@sub 4@(111) terminated surface that are identified as individual Cl atoms. These atoms are bound atop Fe atoms, which occupy tetrahedral Fe sites on the Fe@sub 3@O@sub 4@(111) surface, located in three-fold hollow sites of the underlying close-pa cked O plane. STM images before dosing and the chemical reactivity of a Fe@sub 3@O@sub 4@(111) terminated surface with Cl atoms suggest that this Fe@sub 3@O@sub 4@(111) surface is iron-terminated. In contrast, no changes indicating reactivity of the FeO(111) terminated surface were observed. To further clarify the nature of bright features, STM studies are performed where the surface is exposed to Cl@sub 2@ at room temperature.