Regensburg 2016 – scientific programme

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O: Fachverband Oberflächenphysik

O 58: Organic-Inorganic Systems III: Metal-Organics

O 58.2: Talk

Wednesday, March 9, 2016, 15:15–15:30, S054

Molecular adsorption and self-assembled structures of tetra(cyanophenyl)porphyrin on Cu(111) and ultrathin CoO as substrate — •Tobias Schmitt, Marco Raschmann, Lutz Hammer, and M.Alexander Schneider — Solid State Physics, University Erlangen-Nürnberg, 91058 Erlangen, Germany

Molecular self-assembly on surfaces is controlled by a complex balance between molecule-substrate and intermolecular interactions. We report on the adsorption geometry of single molecules and ordered phases of free-base meso-tetra(m-cyanophenyl)porphyrin (TCNPP) on Cu(111) and on CoO(111)/Ir(100) thin films using low-temperature scanning tunneling microscopy in ultrahigh vacuum. The molecules were deposited at different substrate temperatures to activate diffusion and potential self-assembly processes. When depositing TCNPP onto the Cu(111) surface at T=293K intermolecular H-bonding and dipolar coupling are found to be the dominating inter-molecular interactions but extended ordered structures are not formed. Already at slightly higher temperatures 2-fold metal-ligand coordination comes into play and starts dominating the assembly of linear structures on Cu(111). The molecules themselves remain unmetalated. Also on thin CoO(111) films TCNPP molecules cluster into islands with little tendency to form ordered structures when adsorbed at T=293K . When heated to T=420K the TCNPPs surprisingly show a different internal structure in STM images akin to metalated molecules. At this temperature also networks are observed that show a 3- or 4-fold coordination which we interpret as a sign of metal coordination at the CoO surface.