Berlin 2012 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 14: Adsorption on semiconductors, oxides and insulators II
O 14.11: Vortrag
Montag, 26. März 2012, 18:30–18:45, MA 041
The relevance of surface defects for the adsorption of pyrrole on GaAs(001)-c(4x4) surfaces — •Thomas Bruhn1, Bjørn-Ove Fimland3, Michael Kneissl1, Norbert Esser1,2, and Patrick Vogt1 — 1TU Berlin, Institut für Festkörperphysik, Hardenbergstr.36, 10623 Berlin, Germany — 2Leibniz-Institut für Analytische Wissenschaften, ISAS e.V., Berlin, Albert-Einstein-Str.9, 12489 Berlin, Germany — 3NTNU, NO-7491 Trondheim, Norway
The basic principles that determine the adsorption mechanisms of organic materials on solid surfaces are still not sufficiently understood and represent a key issue for recent semiconductor research. In our work we have investigated the adsorption of the aromatic molecule pyrrole (C4H4NH) on the GaAs(001)-c(4×4) reconstruction. The samples were prepared under UHV conditions and the adsorption process was monitored in-situ with a reflectance anisotropy spectroscopy (RAS) setup operating from 1.5 to 8 eV. At sub-monolayer coverage, single adsorbed pyrrole molecules were investigated by scanning tunneling microscopy (STM), scanning tunneling spectroscopy (STS) and photoelectron spectroscopy (XPS). Our results reveal that pyrrole predominantly physisorbs on As-rich c(4×4) reconstruction and essentially retains its initial electronic structure. Additional, however, we could identify a significant amount of molecules which are chemisorbed at surface defects. Our results demonstrate that the occurence of surface defects plays an important role for the reactivity of the As-rich GaAs c(4×4) surface to the adsorption of pyrrole.