Thin and thick films of iron phthalocyanine （FePc） molecules are deposited on a Ag （110） surface. The nature of the FePc growth and the interaction with the substrate have been studied by X-ray photoelectron spectroscopy （XPS）. All of the core level spectra exhibit rigid shifts towards lower binding energies following the deposition of the organic films, each by a different magnitude. A greater change and a larger shift in the Fe2p level as compared to Cls core level reveals that the adsorbate interacts with the substrate mainly via the Fe atom, located at the center of the molecule. An increase/decrease in the intensity of C1 s/Ag3d level is found to be exponentially linked to the overlayer molecular coverage. Finally, the so- called growth/decay curve indicates that FePc thin films initially develop following the FM growth mode and then transform to SK mode, resulting in 3D island aggregation.
A study of the electronic and structural properties of iron phthalocyanine （FePc） molecules adsorbed on coinage metal surfaces Cu （100） and Cu （110） has been conducted by means of density functional theory calculations. The strength of the molecule-substrate interactions is interpreted in terms of the lateral adsorption geometry and the site specific electronic structure of the molecule. In the case of FePc on a （100）-oriented copper surface, the benzopyrrole leg is found to be oriented at an angle of 9°or 3°from the [01-1] substrate direction. Further, an upward bend in the molecular plane ranging from 7° to 10°is also observed; giving an almost buckled shape to the molecule. However, in the case of FePc on Cu （110）, neither a bend nor a sizable rotation is observed. From the knowledge of the principle structural and electronic properties, it is concluded that FePc-Cu （100） interaction is relatively stronger than FePc-Cu （110） interaction, which is further evidenced by the charge transfer, work function changes, changes in the shape of the adsorbed molecular orbitals, and the orbital shifts. Furthermore, density of states analysis shows that the valence band level shift is surface- and site-dependent.
The energy level alignment of CuPc and FePc on single-layer graphene/Ni（111） （SLG/Ni） substrate was investigated by using ultraviolet and X-ray photoelectron spectroscopy （UPS and XPS）. The highest occupied molecular orbitals （HO- MOs） in a thick layer of CuPc and FePc lie at 1.04 eV and 0.90 eV, respectively, below the Fermi level of the SLG/Ni substrate. Weak adsorbate-substrate interaction leads to negligible interfacial dipole at the CuPc/SLG/Ni interface, while a large interracial dipole （0.20 eV） was observed in the case of FePc/SLG/Ni interface, due to strong adsorbate-substrate coupling. In addition, a new interfacial electronic feature was observed for the first time in the case of FePc on SLG/Ni substrate. This interfacial state can be attributed to a charge transfer from the SLG/Ni substrate to unoccupied orbitals of FePc.
