Simultaneously Understanding the Geometric and Electronic Structure of Anthraceneselenolate on Au(111): A Combined Theoretical and Experimental Study

Self-assembled monolayers (SAMs) of pi-conjugated organic molecules have attracted significant interest in the field of molecular and organic electronics because of their ability to change electrode work functions combined with a considerable conductivity. Studies simultaneously addressing both their geometrical and morphological structure as well as their electronic properties are, however, scarce. Here, we provide a detailed description of layers consisting of anthracene-2-selenolate on Au(111), which display extraordinarily well and long-range ordered structures. Combining experimental data with the results of slab-type band-structure calculations, we are able to unambiguously determine the alignment of the molecules on the surface. The electronic structure of the SAMs is then determined by ultraviolet photoelectron spectroscopy (UPS) and by density functional theory (DFT) based simulations. For the SAM-induced work-function modification a particularly close agreement between the experimental value of -1.3 eV and the calculated -1.37 eV is found. This supports the notion that the currently available modeling approaches have the potential to quantitatively predict important aspects of the electronic structure of SAMs as long as truly well-ordered monolayers are investigated.