Regensburg 2010 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 71: Metal substrates: Epitaxy and growth
O 71.12: Vortrag
Donnerstag, 25. März 2010, 17:45–18:00, H31
Surface structures of thin silver films on the Re(1010) surface — •Viktor Scherf, Lyria Messahel, Christian Pauls, and Klaus Christmann — Freie Universität Berlin, Takustr. 3, 14195 Berlin
We have studied the growth of silver on the Re(1010) surface in UHV between 300 and 700 K by means of MEED and LEED as well as with TPD. The phenomena depend strongly on coverage and temperature: At 300 K a (1×4) LEED phase exists in the large coverage range 0.1<Θ<2. For T>400 K Ag forms a c(2×2) structure which reversibly transforms to the (1×4) phase upon cooling. In-situ MEED was performed during Ag deposition at various temperatures; grazing incidence (∼2∘) and off-Bragg scattering conditions provided high sensitivity with respect to surface electron reflectivity. At 700 K, we find a pronounced correlation between the (0,0) MEED beam intensity and the growth of the Ag phases which helps to calibrate the (local) Ag coverages. Nominal Ag coverages are obtained from Ag TPD peak areas. Systematic LEED intensity-temperature meassurements at fixed ΘAg reveal optimum values of Θ=1.3 for the c(2×2) and Θ=1.5 for the (1×4) structure, respectively. Near the monolayer saturation a pseudomorphic (1×1) structure forms. According to dynamical LEED calculations, it contains two Ag atoms/unit cell and manifests Θ=2 for this bilayer, in which both troughs and ridges of the Re surface are covered by Ag atoms. The data are discussed and compared with the previously studied Au-on-Re(1010) system.