Investigation on the nature of the chemical link between acetylenic organosilane self-assembled monolayers and Au(111) by means of synchrotron radiation photoelectron spectroscopy and scanning tunneling microscopy

Abstract The nature of the chemical link between self-assembled monolayers (SAMs) formed by two polyunsaturated linear organosilanes on Au(1 1 1) are investigated by means of synchrotron radiation induced photoelectron spectroscopy (SR-PES) and scanning tunneling microscopy (STM). The two silane derivatives studied here are 13-trimethylsilyl-1-tridecene-6,12-diyne 1 (R–C C–Si(CH 3 ) 3 ) and 13-dimethylsilyl-1-tridecene-6,12-diyne 2 (R–C C–Si(CH 3 ) 2 H). STM clearly shows that the replacement of one methyl group of 1 by one H atom on the Si atom to give compound 2 , modifying the chemical reactivity versus Au(1 1 1) and hence the adsorption geometry from upright standing (silane 1 ) to horizontal lying (silane 2 ). Analysis of the Au 4f 7/2 and the Si 2p core levels by SR-PES confirms that, as expected, the chemical reactivity with the Au surface increases from 1 to 2 . In terms of the initial state model increased surface-silane electron transfer is correlated with the horizontal surface packing.