AVS 45th International Symposium
    Surface Science Division Monday Sessions
       Session SS1-MoM

Paper SS1-MoM10
The Electronic Structure of Nanosized Mg Clusters on MgO Surfaces: Characterization with MIES

Monday, November 2, 1998, 11:20 am, Room 308

Session: Issues in Surface Electronic Structure
Presenter: J. Günster, Texas A&M University
Authors: J. Günster, Texas A&M University
J. Stultz, Texas A&M University
S. Krischok, Texas A&M University
P. Stracke, Technische Universitat Clausthal, Germany
V. Kempter, Technische Universitat Clausthal, Germany
D.W. Goodman, Texas A&M University
Correspondent: Click to Email
MgO films (2nm thick) were grown on Mo and W substrates with "in situ" investigation by MIES and UPS(HeI). Apart from the valence band emission no additional spectral features could be detected with electron spectroscopies. The oxide surface was exposed to Mg atoms (substrate temperature between 100 K and RT). An additional peak, not seen in UPS, located within the bandgap developed in MIES, located about 2.3eV above the top of the valence band with ca. 1.5eV FWHM at the lowest exposures. Both the energetic position and the peak width depended (weakly) on the exposure time. This additional emission could be detected in MIES until its intensity fell below a level of 10 ppm of that from the valence band. We attribute this additional emission to the formation of small, non-metallic Mg clusters. For small exposures these are 2D clusters.@footnote 1@ It is remarkable that the energetic position of the cluster emission closely matches that expected for the ionization of surface Fs+ / Fs- centers.@footnote 2@ Indeed, the existence of Mg-induced F-type centers an MgO has recently been detected by both ESR@footnote 3@ EELS.@footnote 4@ Therefore, we suggest that in the initial phase of Mg exposure F-type point defects are produced when the Mg adsorbs close to extended defects, such as steps, corners etc. These point defects may play an important role as nucleation sites for the cluster formation. @FootnoteText@ @footnote 1@C.T. Campbell: Surf. Sci. Rep. 27 (1997) 1 @footnote 2@L.N. Kantorovich, J.M. Holender, M.J. Gillan: Surf. Sci. 343 (1995) 221 @footnote 3@E. Giamello, A. Ferrero, S. Coluccia, A. Zecchina: J. Phys. Chem. 95 (1991) 9385 @footnote 4@K.-M. Schr@um o@der, D. Peterka, H. Pfn@um u@r: DPG Fr@um o@hjahrstagung Regensburg, and to be published in Surf. Sci.