LEED CRYSTALLOGRAPHIC INVESTIGATION OF ULTRATHIN FILMS FORMED BY DEPOSITION OF SN ON THE PT(111) SURFACE

Deposition of Sn on the Pt(111) surface followed by annealing at 1000 K leads to the formation of ordered phases showing (2 x 2) and (square -root 3 x square-root 3)R30-degrees LEED patterns, depending on the su rface coverage of Sn. Both these phases were studied by LEED dynamical analysis. The best agreement between experimental and calculated I-V curves was obtained by means of models based on the formation of mixed Pt-Sn layers on the surface where Pt and Sn atoms are nearly coplanar with a slight upward buckling of Sn atoms. The structures of these ph ases are similar to those already observed for the Pt3Sn(111) surface.