TIME-OF-FLIGHT SECONDARY-ION MASS-SPECTROMETRY INVESTIGATIONS OF SELF-ASSEMBLED MONOLAYERS OF ORGANIC THIOLS, SULFIDES, AND DISULFIDES ON GOLD SURFACES

The adsorption behavior of organic thiols, sulfides, and disulfides on gold substrates is investigated by the sensitive surface mass spectrometric technique time-of-flight secondary ion mass spectrometry (TOF-SIMS). Three different preparation techniques, solution deposition, adsorption from solution without rinsing, and the self-assembly (SA) process are compared. Whereas physisorbed molecules (solution deposition, adsorption from solution) can be detected intact independent of their chemical structure, chemisorbed disulfides (SA monolayers) adsorb to the gold as monomers after cleavage of the S-S bond. An influence of the ion bombardment on this result can be excluded due to the intact detection of the molecules from SA monolayers of sulfides.