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M. De Santis:
"Surface crystallography with X-rays: Ni(110)-c(2x2)Mn and Pt_{90}Co_{10}(110)-(1x3)";
Vortrag: Seminar Institut für Allgemeine Physik (IAP), TU Wien; 02.11.2004.

X-ray diffraction (XRD) is a powerful tool to investigate the structure of crystal surfaces. Two XRD studies of crystal surfaces will be presented.
Deposition of about 0.5 monolayer of Mn on Ni(110) results in a c(2¥2) superstructure. XRD analysis shows that a two-dimensional surface alloy is formed. Mn occupies substitutional sites at the surface following a chessboard arrangement. A large corrugation is observed, with Mn atoms shifted outward by ~0.3 Å. For a similar surface alloy, such a corrugation was associated with a high spin state for Mn.
Deconstruction and roughening of Me(110)-(1¥n) surfaces has attracted considerable interest. Here the phase transition of Pt90Co10(110)-(1¥3) is observed by XRD. The data, analyzed jointly with previous LEIS measurements, show that at 800°C the Pt90Co10(110) surface is paved with (dominant) small (1¥2) missing-row areas separated by (1¥3) walls. An average strong contraction of the first interlayer spacing is found (~10%), in agreement with the general trend on both reconstructed and unreconstructed fcc(110) surfaces.