Berlin 2005 – scientific programme

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O: Oberflächenphysik

O 30: Adsorption an Oberfl
ächen III

O 30.8: Talk

Monday, March 7, 2005, 12:30–12:45, TU EB301

XPS study on thiol adsorption on noble metal clusters supported on carbon substrates — •Michael Büttner and Peter Oelhafen — Institute of Physics, University of Basel, Klingelbergstr. 82, 4056 Basel, Switzerland

Submonolayers (0.1A to 1A) of noble metals (Au/Ag) have been deposited onto carbon substrates by means of thermal evaporation. After deposition, thiol vapor was introduced into the vacuum chamber through a leak valve to allow the molecules to adsorb on the metal surfaces. Thiols with long (hexadecanethiol) and short (propanethiol) chains were studied in this work. Additional annealing experiments were performed to investigate thiol desorption as a function of temperature. Between each preparation step the samples were measured with monochromated X-ray Photoelectron Spectroscopy (MXPS) and core-level spectra of the metal and the sulfur were obtained. MXPS valence-band spectra were taken to estimate the metal particle size and to monitor changes in the valence band shape and the Fermi edge upon thiol adsorption.

Shifts towards higher binding energy and changes in the line shape could be observed in the Au 4f core-level spectra after thiol adsorption. We will compare these findings with results for silver particles and comment on the influence of the thiol chain length.