The presence of two different sulfur species in self-assembled films of n-alkanethiols on Au and Ag surfaces

High-resolution photoelectron spectroscopy using photon energies of 200 and 1486 eV is used to reveal the presence of two different sulfur species in alkanethiolate films on Au and Ag surfaces. Self-assembly from a solution in ethanol gave similar results to vapour phase deposition onto clean substrates in ultrahigh vacuum. In addition to chemical differences of the two S species as implied by the 1.3 eV difference in the S 2p binding energies angular-resolved measurements revealed intensity variations caused by photoelectron diffraction. This observation indicates also a geometrical inequivalence of the two sulfur species.