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29th European conference on Surface Science - 1,4-benzenedimethanethiol self assembled monolayers on Au(111) and Ag(111) from vapour phase: stability with surface temperature

Congreso

Autoría
J.C. Moreno López, L. Salazar-Alarcón, O. Grizzi, V.A. Esaulov, M.L. Martiarena, E.A. Sánchez
Fecha
2012
Editorial y Lugar de Edición
29th European conference on Surface Science
Resumen Información suministrada por el agente en SIGEVA
We present results of a vacuum evaporative absorption method of assembly of the conjugated dithiol molecule 1,4-benzenedimethanethiol on the surfaces of Au(111) and Ag(111). Direct recoil spectroscopy with time-of-flight analysis shows in both cases formation of a standing up self-assembled monolayer (SAM) with S atoms available at the SAM-vacuum interface. Investigation of the adsorption kinetics shows that a lying down phase is formed at low exposures, which precedes the SAM phase. At room te... We present results of a vacuum evaporative absorption method of assembly of the conjugated dithiol molecule 1,4-benzenedimethanethiol on the surfaces of Au(111) and Ag(111). Direct recoil spectroscopy with time-of-flight analysis shows in both cases formation of a standing up self-assembled monolayer (SAM) with S atoms available at the SAM-vacuum interface. Investigation of the adsorption kinetics shows that a lying down phase is formed at low exposures, which precedes the SAM phase. At room temperature, optimal conditions for standing up SAM formation require exposures of the order of a mega Langmuir, while around 250 K, a few kilo Langmuir are sufficient to form the dense layer. Multilayer formation is observed when the adsorption is performed below 250 K. A study of the SAM stability with temperature shows: i) the multilayer desorbs around 265 K, ii) the S terminated layer survives up to ~370 K, above this temperature a reordering of the layer takes place where S atoms are no longer available at the vacuum interface, iii) final desorption occurs around 500K. Analysis of the products remaining after surface annealing reveals C and S for the SAM phase and only S for the lying down phase. The C content left at the Ag surface is higher than that left at the Au surface. The scattering features are discussed in terms of DFT calculations that show the changes occurring in the molecule geometry during both phases.
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Palabras Clave
SURFACESELFASSEMBLYBENZENEDIMETHANETHIOL