Nitrogen substitution impacts organic-metal interface energetics

Abstract

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.

Orientation-Dependent Work-Function Modification Using Substituted Pyrene-Based Acceptors

“…The values are summarized in Table 1 . Note that the averaged Ag–C distance is much shorter than for weakly interacting monolayers on the same substrate, e.g., DIP (3.01 Å), 70 7,8,15,16-tetraazaterrylene (2.99 Å), 71 pentacene (2.98 Å to 3.12 Å), 72 or P2O (3.32 Å). 16 Moreover, also strongly interacting systems like P4O (2.69 Å) or PTCDA (2.81 Å to 2.86 Å) 38 , 73 , 74 have longer averaged Ag–C bonding distances, and the difference between averaged carbon and oxygen distances (0.15 Å) is smaller than that of P4O/Ag(111) (0.26 Å).…”

“…Unfortunately, an experimental determination of bonding distances of nitrogen atoms on Ag(111) was not possible, as the N 1s signal too strongly overlaps with a Ag 3d plasmon. 71 Nevertheless, the position of the −NO 2 group could be determined relying on the substantial chemical shift between carbonyl and nitro O 1s levels. Following ref ( 38 ) we fitted each of the two O 1s components with a separate peak and used its area as input for the photoelectron yield in the further analysis.…”

Metal-organic interface functionalization via acceptor end groups: PTCDI on coinage metals

“…XSW and high-resolution XPS of PTCDI (sub)monolayers were measured at beamline I09 at the Diamond Light Source, where (sub)monolayer coverages were prepared in situ and measured in a similar configuration as in Refs. [15,16]. The UPS and multilayer XPS as well as the LEED measurements were carried out at Soochow University following the same procedure as discussed in Refs.…”

“…The UPS and multilayer XPS as well as the LEED measurements were carried out at Soochow University following the same procedure as discussed in Refs. [16,17]. Further details can be found in Ref.…”

Stoichiometric and Oxygen-Deficient VO2 as Versatile Hole Injection Electrode for Organic Semiconductors

“…Temperature-dependent resistivity measurements show the MI transition at 335 K. The corresponding X-ray diffraction patterns and resistivity traces are shown in the Supporting Information, as well as the surface morphology obtained by scanning force microscopy (Figure S1). The photoemission experiments were carried out in an ultrahigh vacuum (UHV) in a customized SPECS photoelectron spectroscopy system consisting of interconnected load-lock chamber, preparation and evaporation chambers (base pressure: 3 × 10 –10 mbar), and analysis chamber (base pressure: 2 × 10 –10 mbar). The XPS spectra were recorded using a monochromatized Al Kα source (1486.7 eV) and UPS spectra were recorded using the monochromatized He Iα excitation line (21.22 eV).…”