Electronic structure of a silole derivative-magnesium thin film interface

Abstract

Photoemission spectroscopy of an interface between Mg and a silole derivative, $\text{2,5-}\mathrm{bis}{\text{[6}}^{\prime }{\text{-(2}}^{\prime }{\text{,2}}^{″}-\mathrm{bipyridyl}\text{)]-1,1-}\mathrm{dimethyl}\text{-3,4-}\mathrm{diphenyl}$ silacyclopentadiene (PyPySPyPy) reveals the formation of two gap states both at metal-on-organic (Mg/PyPySPyPy) and organic-on-metal (PyPySPyPy/Mg) interfaces. The appearance of gap states is interpreted as the result of electron transfer from Mg to PyPySPyPy, leading to the formation of a charge transfer complex. A strong correlation found between the metal and organic core level shifts, and the changes in the Fermi level position at the Mg/PyPySPyPy interface further supports the model of charge transfer between the metal and the organic. Despite the similar chemical character of the two interfaces, the binding energy (BE) of the gap states at the PyPySPyPy/Mg interface is 0.2–0.3 eV higher than the gap state BE measured at the reversed interface.