Scanning tunneling microscopy of dibutylamino-triazine-dithiol monolayer on Au(111)

We observed molecular resolution images of dibutylamino-triazine-dithiol films on Au(111) with scanning tunneling microscopy. In contrast to the more extensively studied alkanethiols which have only one binding site, the triazine-dithiol has two possible binding sites. The periodic structure of bright spots with different shapes and contrast aligned along the [<(11)over bar> 2] directions with a spacing of 0.75 nm and 1 nm were imaged, The domain size of the film is 15 nm at most, which is considerably smaller than that of alkanethiol films. The structural stability upon annealing indicates a stronger binding energy of the triazine-dithiol as compared with the alkanethiol. We propose models of the molecular arrangement assuming that the two sulfur atoms of the molecule bind to the substrate.