Surface chemistry of organic adsorbates
Michel Kazempoor, Gerhard Pirug, Stefan Tautz
Organic molecules play an important role in various fields such as electrochemistry or more recently in molecular electronics. Applying the surface science approach we try to characterize their physical and chemical properties on surfaces to get a deeper understanding for their functional behavior in possible future applications.
Related to current problems in electrochemistry we studied the adsorption of formic acid and its coadsorption with water. It turned out that the adsorption behavior is not only controlled by adsorbate substrate interactions but also by H bonding within the adsorbed layer. Vibrational spectroscopy using HREELS (high resolution electron energy loss spectroscopy) shows that the chemical interaction between the Au(111) surface and formic acid is rather weak leading to flat lying molecules forming 1 dimensional H bonded chains. Upon water coadsorption these chains could be broken in favor of H bonded formic acid-water complexes. The thermal decay of theses complexes is accompanied by a proton exchange.
Ferrocene is considered as a candidate for metal deposition for nanoelectronics and even as a functional molecule for spintronics, due to its photon sensitivity and magnetic properties, respectively. A combined STM, LEED and HREELS showed that ferrocene is nearly upright standing, rather weakly and reversible molecularly adsorbed in a well ordered surface structure. Intermolecular interaction leads to zig-zag rows with mutual alternating tilt directions in a glide plane symmetry. The resulting (√3x3√3)rect (p2mg) structure could be identified consistently by STM and LEED.
M. Kazempoor and G. Pirug, Complex formation and proton transfer between formic acid and water adsorbed on Au(111) surfaces under UHV conditions, Appl. Phys A 87, 435-441 (2007)
J. Myslivecek, Charles University Prague, Czech Republic.