Multicomponent Adlayers of Tetraphenylporphyrins on Ag(111)
The identification of porphyrins in two- and three-component adlayers is demonstrated in this section. In that course the voltage-dependent appearance of the individual species was exploited. This method is conducted in Sect. 9.1 for the discrimination of CoTPP and 2HTPP. In this respect also the spectroscopy mode of the STM was applied to interpret the individual appearance in the binary layer. In Sect. 9.2 it is shown in sub-molecularly resolved STM images that different porphyrins can be chemically identified in a multicomponent adlayer (FeTPP/CoTPP/2HTTP), whereupon in particular CoTPP exhibits a distinct bias-dependent appearance. This study was going along with a successful cooperation with the working group of Andreas Görling (embedded in the framework of the SFB 583), calculating STM images with density functional theory (DFT). In this respect, adsorbate–substrate coupling was demonstrated. In the spectroscopy mode, continuous imaging tunneling spectroscopy (CITS) was performed, also enabling to identify FeTPP/CoTPP/2HTPP in energy-selective maps, showing the local variation of density of states (Sect. 9.3).