Molecular level alignment and work function change of dimethyl-disulfide physisorbed thin films on Au(111)

The formation and the electronic properties of a dimethyl–disulfide (DMDS) thin film adsorbed at low temperature on the Au(111) 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.