Dresden 2009 – scientific programme

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O: Fachverband Oberflächenphysik

O 63: Semiconductor substrates: Adsorption

O 63.4: Talk

Friday, March 27, 2009, 12:00–12:15, SCH A118

STM study of the adsorption of coronene on Si(111)-(7x7) — •Jesus Martinez-Blanco, Max Klingsporn, and Karsten Horn — Fritz Haber Institut, Berlin, Germany

The adsorption of organic molecules on silicon surfaces is of interest in the control of their preparation and processing for applications in device fabrication. The (7x7) reconstructed silicon (111) surface presents a rich array of electronically inequivalent reaction sites, due to its unique electronic properties of reactive adatoms, rest atoms, and corner holes on the surface, which has been investigated with respect to molecular adsorption, and provides a rich playground. Here we report on the adsorption of coronene (C24H12) on the Si(111)-(7x7) surface. Coronene is a polycyclic aromatic hydrocarbon (PAH) consisting of seven peri-fused benzene rings. We use Scanning Tunneling Microscopy (STM) to investigate the local long range structure. Upon room temperature adsorption, we find that the coronene molecules preferentially adsorb on the unfaulted half of the 7x7 unit cell. Molecules adsorbed on different sites can be induced to move to the preferential sites by the action of the tip in repeated image scans. Imaging of the molecules is strongly bias dependent, and also critically depends on the adsorption site. We discuss the structure of coronene on Si(111)-(7x7) on the basis of our data and in comparison with STM studies of coronene on the Si(001)-(2x1) surface where long range order is not observed.