Berlin 2012 – scientific programme
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O: Fachverband Oberflächenphysik
O 89: Metal substrates: Adsorption of organic / bio molecules V
O 89.8: Talk
Friday, March 30, 2012, 12:15–12:30, A 053
Structure and Binding of Large Molecules at Metal Surfaces: theoretical NEXAFS for Co-OEP on Ni(100) — •Chunsheng Guo1, Lili Sun1, Klaus Hermann1, Christian Hermanns2, and Wolfgang Kuch2 — 1Theory Department, Fritz-Haber-Institut, Berlin — 2Inst. of Experimental Physics, Free University, Berlin, Germany
Metal octaethylporphyrins (M-OEP), M-N4C20H4(C2H5)8, adsorbed on metallic substrate are promising candidates to provide spin dependent electric transport. While experimental studies on these systems have been performed details of the adsorbate geometry and surface binding are still unclear. We have carried out density-functional theory (DFT) calculations on free Co-OEP and for Co-OEP adsorbed at Ni(100) with periodic surface models. The resulting equilibrium geometries are then applied in StoBe cluster calculations to yield theoretical C and N 1s excitation spectra of free and adsorbed Co-OEP. Experimental carbon K edge NEXAFS spectra of separate Co-OEP show a triple-peak structure which can be explained from theory by differently binding carbon. When adsorbed at Ni(100) substrate the triple-peak structure reduces to a double-peak, not yet confirmed by experiment. The measured nitrogen K edge spectra of Co-OEP, showing a double-peak structure, are also affected by the substrate. This is explained by hybridization of adsorbate final state orbitals near the nitrogen centers with 3d orbitals of the Ni substrate due to adsorbate-substrate binding. Test test Test test Test test Test test Test test Test test
Supported by SFB 658 "Molecular switches at surfaces", Berlin