AVS 47th International Symposium
    Thin Films Wednesday Sessions
       Session TF+EL-WeA

Paper TF+EL-WeA1
Monitoring of Thin Film Metallization by Metastable He Atom Scattering

Wednesday, October 4, 2000, 2:00 pm, Room 203

Session: In-situ Characterization of Thin Film Growth
Presenter: G. Witte, Lehrstuhl fuer Physikalische Chemie I, Germany
Authors: G. Witte, Lehrstuhl fuer Physikalische Chemie I, Germany
P. Fouquet, Physikalische Chemie I, RUB, Germany
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Here we introduce metastable helium atom scattering (MHAS) to characterize metallization transitions occuring during the growth of ultrathin alkali metal (AM) films on metal and semiconductor surfaces. This technique combines the high sensitivity of HAS for measuring coverage and geometrical structure of the adlayer and the extreme surface sensitivity of the metastable atom deexcitation rate to detect modifications of the electronic surface structure.@footnote 1@ In case of Na, K and Cs on Cu(100) an onset of metallization was found at coverages of about half a monolayer. On the other hand for GaAs(110) somewhat larger coverages are required to produce metallic AM films, which are found to grow only below room temperature. These results are in good agreement with previous MDS experiments. Further experiments were carried out for alkali earth metal (AEM) films, where a particular attention is drawn to the comparison of Cs and Ba on Cu(100). It is shown that the onset of metallization for both systems is very similar and can be well described by a 2D Herzfeld model. Finally, MHAS can also be applied to characterize the demetallization of ultrathin AM and AEM films upon adsorption of CO or oxygen.@footnote 2@ @FootnoteText@ @footnote 1@ P.Fouquet and G. Witte, Phys. Rev. Lett. 83, 360 (1999). @footnote 2@ P.Fouquet and G. Witte, Surf. Sci. 454-456, 256 (2000).