AVS 52nd International Symposium
    Electronic Materials and Processing Wednesday Sessions
       Session EM+SS-WeM

Paper EM+SS-WeM5
Modelling Inhomogeneities of Organic Device Contacts: Organic Film Growth on Nanostructured Surfaces

Wednesday, November 2, 2005, 9:40 am, Room 309

Session: Contacts to Organic and Molecular Devices
Presenter: M.G. Ramsey, Karl-Franzens-University Graz, Austria
Authors: M.G. Ramsey, Karl-Franzens-University Graz, Austria
B. Winter, Karl-Franzens-University Graz, Austria
S. Surnev, Karl-Franzens-University Graz, Austria
G. Koller, Karl-Franzens-University Graz, Austria
F.P. Netzer, Karl-Franzens-University Graz, Austria
Correspondent: Click to Email
In this contribution the growth, geometric and electronic structure of sexiphenyl films grown on clean Cu(110) and mesoscopically patterned Cu(110)-(2x1)O will be presented. The results highlight the effects of the atomic and nanometric substrate structure on the growth and electronic level alignment of active organic films. Scanning tunnelling microscopy (STM) reveals that on the clean Cu the molecules align parallel to each other and are highly mobile in one surface direction. By monolayer coverages a complete layer forms reminiscent of a smectic liquid crystal phase. Despite the lack of strict long range order the molecules align in strings with a periodicity determined by intermolecular interactions, while the periodicity between the strings is determined by the substrate periodicity. In contrast when the substrate is covered with a half monolayer of oxygen the molecules appear not to wet the surface and, apart from at defects, are not visible in STM. On the mesoscopically patterned Cu(110)-(2x1)O (stripes of clean and oxygen covered surface with a periodicity of ~ 7 nm) the molecules first appear at the Cu-CuO boundaries and then grow preferentially on the clean Cu stripes. Growth and electronic structure on the three basic substrate situations are also followed by angle resolved ultraviolet photoemission spectroscopy (ARUPS). These results highlight the problems of imaging such wide band gap materials with STM and indicate that the 6P does in fact wet the Cu(110)-(2x1)O and that the visibility of the molecule is dependent on charge transfer states in the gap. These ARUPS results will also be discussed in terms of the electronic level alignment on inhomogeneous surfaces where large band offsets between molecules on different regions occur.