Quantitative analysis of the electronic decoupling of an organic semiconductor molecule at a metal interface by a monolayer of hexagonal boron nitride

The influence of an interfacial hBN layer on the fluorescence of an organic molecule

“…The HOMO of PTCDA is found at ca. 2.6 eV [32]. Hence, we can expect that both the LUMO and the HOMO are placed within the bandgap of hBN, as indicated in Figure 1b.…”

“…After every experiment, the exact coverage was determined by a thermally programmed desorption (TPD) experiment with a margin of error of ±0.05 ML. The calibration for PTCDA/hBN/Cu(111) was derived from the TPD data shown in [32]. Since the packing densities of PTCDA on hBN/Cu(111) and on Cu(111) are within a few percent of each other (see Appendix A), this calibration is also valid for PTCDA/Cu(111) within the noted margin of error.…”

“…We have previously shown that the bonding situation between PTCDA and hBN/Cu(111) is weak and physisorptive [32] as opposed to the chemisorptive bond between PTCDA and Cu(111) [33]. Ultraviolet photoelectron spectroscopy (UPS) experiments showed that on the Cu(111) surface the chemical bonding leads to a filling of the LUMO [33].…”

“…Ultraviolet photoelectron spectroscopy (UPS) experiments showed that on the Cu(111) surface the chemical bonding leads to a filling of the LUMO [33]. In contrast, on hBN/Cu(111), the differential energies of the PTCDA orbitals remain unaltered in comparison to those of PTCDA in the gas phase, which points to a more physisorptive bonding to the hBN/Cu(111) surface [32]. The HOMO of PTCDA is found at ca.…”

“…The hybridization of the electronic states of PTCDA and Cu leads to a distortion of the molecule where the oxygen atoms are pushed away from the substrate and out of the molecular plane [35]. On hBN/Cu(111), the molecule remains essentially flat and at a very large vertical distance from the hBN layer of 3.37 Å [32]. In contrast, on Cu(111) the vertical distance of the perylene core from the Cu(111) surface is only 2.66 Å [35].…”