Dresden 2006 – scientific programme

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O: Oberflächenphysik

O 47: Organic films IV

O 47.3: Talk

Friday, March 31, 2006, 11:45–12:00, PHY C213

Structural investigation of SnPc on Ag(111) using NIXSW — •C. Stadler, F. Pollinger, S. Hansen, C. Kumpf, and E. Umbach — Exp. Physik II, Univ. Würzburg

The investigation of the interaction of organic molecules with inorganic substrates is a key issue for understanding interface effects. We report on NIXSW measurements of two different superstructures of flat-lying tin-phthalocyanine (SnPc) molecules on Ag(111): an incommensurate monolayer at room temperature with one molecule per unit cell and a commensurate submonolayer (at 150K) with two molecules per unit cell. Precise information about the vertical bonding distance of different atomic species in the molecule with respect to the substrate is obtained. This results in a model for the RT structure with the Sn atom 0.75Å below the plane of carbon and nitrogen atoms, i.e., the molecules lie "tin-down" on the surface. The Sn-Ag distance is 2.44Å, which is very close to the Ag-Ag layer distance. In contrast, for the 150K phase a mixture of "tin-down" and "tin-up" orientations is formed. This is based on a strongly reduced coherent fraction of 0.42 for the Sn3d signal, which can be explained by two Sn-adsorption sites with a height of 2.37Å and 3.91Å respectively.