The electronic structure of cobalt phthalocyanine (CoPc) on Pt(111), graphene/Pt (111), and Au-intercalated graphene/Ni(111) is investigated by photoexcited electron spectroscopies: photoemission (XPS and UPS) and X-ray absorption spectroscopy (XAS or NEXAFS). For CoPc on Pt(111), significant changes of the shape of XPS and XAS spectra indicate a charge transfer from the metal substrate to the Co ion of CoPc. The strong interaction between CoPc and Pt(111) can be completely prevented by the insertion of a graphene buffer layer. For CoPc on graphene/ Ni(111), the charge transfer is only prevented if the graphene on Ni(111) is intercalated by gold. Therefore, the disturbance of the graphene electronic structure by the interaction with underlying substrate and the corresponding charge doping of graphene has been found to affect the electronic properties of adsorbed CoPc considerably.

The influence of graphene interlayers on electronic interface properties of cobalt phthalocyanine on Ni(111) is studied using both photoemission and X-ray absorption spectroscopy. A charge transfer associated with a redistribution of the d-electrons at the Co-atom of the phthalocyanine occurs at the interface to Ni(111). Even a graphene buffer layer cannot prevent the charge transfer at the interface to Ni(111); however, the detailed electronic situation is different.

Heteroepitaxially grown bilayers of ferromagnetic La0.7Ca0.3MnO3 (LCMO) on top of superconducting YBa2Cu3O7 (YBCO) thin films were investigated by focusing on electric transport properties as well as on magnetism and orbital occupation at the interface. Transport measurements on YBCO single layers and on YBCO/LCMO bilayers, with different YBCO thickness dY and constant LCMO thickness dL = 50 nm, show a significant reduction of the superconducting transition temperature Tc only for dY < 10 nm,with only a slightly stronger Tc suppression in the bilayers, as compared to the single layers. X-ray magnetic circular dichroism (XMCD) measurements confirm recently published data of an induced magnetic moment on the interfacial Cu by the ferromagnetically ordered Mn ions, with antiparallel alignment between Cu and Mn moments. However, we observe a significantely larger Cu moment than previously reported, indicating stronger coupling between Cu and Mn at the interface. This in turn could result in an interface with lower transparency, and hence smaller spin diffusion length, that would explain our electric transport data, i.e. smaller Tc suppression. Moreover, linear dichroism measurements did not show any evidence for orbital reconstruction at the interface, indicating that a large change in orbital occupancies through hybridization is not necessary to induce a measurable ferromagnetic moment on the Cu atoms.

The electronic structure of the interface between cobalt phthalocyanine (CoPc) and epitaxially grown manganese oxide (MnO) thin films is studied by means of photoemission (PES) and X-ray absorption spectroscopy (XAS). Our results reveal a flat-lying adsorption geometry of the molecules on the oxide surface which allows a maximal interaction between the π-system and the substrate. A charge transfer from MnO, in particular, to the central metal atom of CoPc is observed by both PES and XAS. The change of the shape of N-K XAS spectra at the interface points, however, to the involvement of the Pc macrocycle in the charge transfer process. As a consequence of the charge transfer, energetic shifts of MnO related core levels were observed, which are discussed in terms of a Fermi level shift in the semiconducting MnO films due to interface charge redistribution.

The alteration of the electronic interface properties of iron phthalocyanine (FePc) on Ni(111) by graphene interlayers is studied using both photoemission techniques (XPS and UPS) and X-ray absorption spectroscopy (XAS). Both XPS and XAS clearly indicate a charge transfer from Ni(111) to the Fe ion of FePc. In contrast to CoPc, this charge transfer can be completely suppressed by the introduction of a graphene buffer layer between FePc and Ni(111). Further UPS measurements indicate that the interfacial charge transfer include also the FePc macrocycle. Surprisingly, for FePc and CoPc the energy level alignment after the formation of the interface dipoles is rather unaffected by both the introduction of a graphene buffer layer and charge transfer processes between the central metal atom of the Pc and the substrates.

The interaction at interfaces between transition-metal phthalocyanines and ultrathin transition-metal oxide films is studied by means of photoemission (PES) and X-ray absorption spectroscopy (XAS). Our results are compared to the recently investigated system CoPc on MnO. A flat-lying adsorption geometry of iron and cobalt phthalocyanines (FePc and CoPc) on the different oxide substrates was observed: ultrathin epitaxially grown MnO films and ultrathin TiO x films. A charge transfer from the MnO, in particular, to the Fe atom of the FePc molecule is observed by both PES and XAS. X-ray absorption spectra of the N K-edge of FePc do not hint at a nitrogen involvement in the interaction process. As a consequence of the charge transfer, a shift of the Fermi level of the semiconducting MnO films is observed, which is visible as a shift of MnO related core levels to lower binding energy. In contrast, CoPc and FePc deposited on TiO x show no hints for a charge transfer, although the flat-lying adsorption geometry allows in principle a maximum interaction between the π-system and the substrate. Increased surface roughness (compared to MnO) and an oxygen termination of the surface of the TiO x films is considered to suppress a possible strong interaction between the organic molecules and the substrate.

Interface properties of iron phthalocyanine (FePc) and perfluorinated iron phthalocyanine (FePcF 16 ) on rutile TiO 2 (100) and TiO 2 (110) surfaces were studied using X-ray photoemission spectroscopy (XPS), X-ray absorption spectroscopy (XAS), and low-energy electron diffraction (LEED). It is demonstrated that the interaction strength at the interfaces is considerably affected by the detailed preparation procedure. Weak interactions were observed for all studied interfaces between FePc or FePcF 16 and rutile, as long as the substrate was exposed to oxygen during the annealing steps of the preparation procedure. The absence of oxygen in the last annealing step only had almost no influence on interface properties. In contrast, repeated substrate cleaning cycles performed in the absence of oxygen resulted in a more reactive, defect-rich substrate surface. On such reactive surfaces, stronger interactions were observed, including the cleavage of some C-F bonds of FePcF 16 .

The influence of graphene as an buffer interlayer on the behavior of MnPc on a Ni(111) single crystal surface has been investigated by means of photoemission and X-ray absorption spectroscopy (XAS). MnPc suffers serious damage to its molecular structure on the Ni(111) surface as evident from photoemission signals, with large impact on the molecular orientation and the electronic structure. The insertion of a graphene buffer layer prevents the chemical reaction and enables highly oriented growth of unaltered molecules. The electronic situation at the interface however is different to the bulk: An interfacial charge transfer is observed involving both nitrogen and manganese atoms of MnPc..