Regensburg 2007 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 41: Metal Substrates: Adsorption II

O 41.3: Vortrag

Mittwoch, 28. März 2007, 16:15–16:30, H39

LEED investigations on SAM of biphenylthiols on Au (111) surfaces — •Michel Kazempoor and Gerhard Pirug — Institut für Bio- und Nanosysteme (IBN3) and Center of Nanoelectronic Systems for Informationtechnology (CNI), Forschungszentrum Jülich GmbH, D-52425 Jülich

Organic molecules of 4’-methyl-1,1’-biphenyl-4-alkanethiols (BPn, n = number of alkane spacer) are known to form well ordered so called self assembled monolayer (SAM) structures on metal surfaces. Characterizing the ordering and packing behaviour of BPn is essential for the understanding of the electronic and optical properties. BPn structures are predominantly characterized by STM measurements. In addition a (2√3 x √3) structure has been proposed for BP3, based on a diffuse LEED pattern (Azzam et. al., Langmuir 19 (2003) 8262). However, there is still an ongoing discussion about different unit cells of BPn molecules on Au (111). In principal, LEED should allow a reliable identification of the unit cell and the determination of its lattice vectors. Therefore we studied the adsorption of BP3 and BP4 on Au(111) surfaces using a micro channel plate (MCP) LEED system, which allows a more gentle examination with reduced electron beam current in the pA regime. The samples were exposed at room temperature to BPn molecules by gas phase deposition. After subsequent annealing up to 423 K we observed unit cells corresponding to a c(16 x 2√3) and (5√3 x √3) structure for BP3 and BP4, respectively. Structure models will be discussed under consideration of recent STM findings.