REACTION OF 1,2-ETHANEDITHIOL ON CLEAN, SULFUR-MODIFIED, AND CARBON-MODIFIED MO(110) SURFACES

The reactivity of 1,2-ethanedithiol on the clean Mo (110) and p(4X4)-C /Mo (110) surfaces has been investigated as a function of sulfur cover age using temperature programmed desorption (TPD), Auger electron spec troscopy, and low energy electron diffraction. TPD experiments perform ed on both surfaces produced similar reaction products, although chang es were observed in selectivity. On the clean Mo (110) surface, the ma jor products observed during TPD experiments were acetylene, ethylene, vinyl thiol, and ethanethiol. However, the reaction of ethanedithiol on the p(4X4)-C/Mo (110) surface produced acetylene, ethylene, and eth anedithiol. Product molecules are thought to arise from two distinct t ypes of surface intermediates: (1) a monodentate thiolate species boun d to the surface through only one of the ethanedithiol sulfur atoms, a nd (2) a bidentate organosulfur metallocycle bound to the surface thro ugh both of the ethanedithiol sulfur atoms. We propose that vinyl thio l and ethanethiol are produced via C-S bond scission and subsequent hy dride elimination of the monodentate thiolate intermediate, and that t he bidentate surface metallocycles undergo C-S bond scission to yield acetylene and ethylene. On the carbon-modified surface, complete desul furization of ethanedithiol occurs upon decomposition, yielding only h ydrocarbon products. With increasing sulfur coverage, a decrease in re activity and a shift in desorption features to lower temperatures is o bserved for ethanedithiol on the clean and carbon-modified surfaces. ( C) 1998 American Vacuum Society.