Nitrogen Substitution Impacts Organic-Metal Interface Energetics

We investigated the structural and electronic properties of vacuum sublimed 7,8,15,16-tetraazaterrylene (TAT) thin films on Au(111), Ag(111), and Cu(111) substrates using inverse photoemission spectroscopy, ultraviolet photoelectron spectroscopy (UPS), x-ray photoelectron spectroscopy (XPS), low energy electron diffraction (LEED), and the x-ray standing wave (XSW) technique. The LEED reveals a flat adsorption geometry of the monolayer TAT on these three substrates, which is in accordance with the XSW results. The molecules are slightly distorted in monolayers on all three substrates with the nitrogen atoms having smaller averaged bonding distances than the carbon atoms. On Ag(111) and Cu(111), chemisorption with a net electron transfer from the substrate to the adsorbate takes place, as evidenced by UPS and XPS. Combining these results, we gain full insight into the correlation between electronic properties and interface geometry.