Molecular level alignment and work function change of dimethyl-disulfide physisorbed thin films on Au(1 1 1)

The formation and the electronic properties of a dimethyl-disulfide (DMDS) thin film adsorbed at low temperature on the Au(1 1 1) surface has been studied by means of Ultraviolet Photoemission Spectroscopy. The dependence of the binding energy of the molecular states as a function of coverage has been analyzed and compared to the corresponding work function change. A deviation from the expected rule for the molecular level alignment is observed and attributed to the differences between local and average work function. The effect of a buffer thiolated monolayer, obtained by dosing DMDS at room temperature, on the evolution of the interface electronic properties is also analyzed and discussed.