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The doping mechanism of fully suspended nanoporous graphene with alkali metals unveils the charge redistribution between the donors and graphene. The evolution of the electronic charge induced in the graphene upper Dirac cone has been correlated with the electron–phonon interaction by employing complementary electronic and vibrational spectroscopic techniques in ultra high vacuum ambient. K and Cs doping induces a significant rigid band shift and Dirac cone filling correlated with the neat formation of a π*-plasmon mode and a clear signature of electron–phonon interaction in the Raman spectra, while Na doping slightly influences the graphene electronic and vibrational response, fostered by adatom Na clustering.

We report on the polarization analysis of the Raman spectrum of highly vertically aligned multiwall carbon nanotubes (MWCNTs). A simple model considering the average angle distribution across the MWCNT axes accounts for the observed angular dependent Raman mode intensity. The model fully fits the experimental data, allowing to derive an average waving angle of ∼37° around the MWCNT axes and explaining the apparent discrepancy of previous experiments reported in the literature. Furthermore, we can distinguish two components in the Raman G-band, associated to the longitudinal and transversal optical modes. Their intensity dependence as a function of polarization clearly suggests the metallic nature of these MWCNTs, experimentally verified by the valence band photoemission analysis. The present study provides a simple, effective spectroscopic method to determine physicochemical and specific morphological characteristics of carbon nanotubes.

Surface-assisted polymerization of molecular monomers into extended chains can be used as the seed of graphene nanoribbon (GNR) formation, resulting from a subsequent cyclo-dehydrogenation process. By means of valence-band photoemission and ab initio density-functional theory (DFT) calculations, we investigate the evolution of molecular states from monomer 10,10′-dibromo-9,9′bianthracene (DBBA) precursors to polyanthryl polymers, and eventually to GNRs, as driven by the Au(110) surface. The molecular orbitals and the energy level alignment at the metal–organic interface are studied in depth for the DBBA precursors deposited at room temperature. On this basis, we identify a spectral fingerprint of C–Au interaction in both DBBA single-layer and polymerized chains obtained upon heating. Furthermore, DFT calculations help us by evidencing that GNRs interact more strongly than DBBA and polyanthryl with the Au(110) substrate, as a result of their flatter conformation.

Scanning tunneling microscopy and X-ray spectroscopy measurements are combined to first-principles simulations to investigate the formation of graphene nanoribbons (GNRs) on Au(110), as based on the surface-mediated reaction of 10,10′-dibromo-9,9′-bianthracene (DBBA) molecules. At variance with Au(111), two different pathways are identified for the GNR self-assembly on Au(110), as controlled by both the adsorption temperature and the surface coverage of the DBBA molecular precursors. Room-temperature DBBA deposition on Au(110) leads to the same reaction steps obtained on Au(111), even though with lower activation temperatures. For DBBA deposition at 470 K, the cyclodehydrogenation of the precursors preceds their polymerization, and the GNR formation is fostered by increasing the surface coverage. While the initial stages of the reaction are found to crucially determine the final configuration and orientation of the GNRs, the molecular diffusion is found to limit in both cases the formation of high-density long-range ordered GNRs. Overall, the direct comparison between the Au(110) and Au(111) surfaces unveils the delicate interplay among the different factors driving the growth of GNRs.

Iron-phthalocyanine molecules self-assemble on the moiré pattern of graphene/Ir(111) as a flat and weakly interacting layer, as determined by core-level photoemission and absorption spectroscopy. The graphene buffer layer decouples the FePc two-dimensional structure from the underlying metal; the electronic structure of the FePc molecular macrocycles is preserved; and the Fe-L2,3edges present narrower and slightly modified resonances at the FePc single-layer coverage with respect to a thin film. The FePc layer induces a slight electron doping to the Ir-supported graphene resulting in the Dirac cone position expected for an ideal free-standing-like graphene layer with the standard Fermi velocity.

Iron–phthalocyanine (FePc) molecules deposited on the Au(110) surface self-organize in ordered chains driven by the reconstructed Au channels. The interaction process induces a rehybridization of the electronic states localized on the central metal atom, breaking the 4-fold symmetry of the molecular orbitals of the FePc molecules. The molecular adsorption is controlled by a symmetry-determined mixing between the electronic states of the Fe metal center and of the Au substrate, as deduced by photoemission and absorption spectroscopy exploiting light polarization. DFT calculations rationalize this mixing of the Fe and Au states on the basis of symmetry arguments. The calculated electronic structure reproduces the main experimental spectral features, which are associated to a distorted molecular structure displaying a trigonal bipyramidal geometry of the ligands around the metal center.

The structural patterns formed by molecular self-assembly at surfaces are usually controlled by the relative strengths of the intermolecular and molecule–substrate interactions. An additional steering effect is present when the substrate can easily reconstruct upon molecular adsorption, which therefore drives a self-templating effect on the metal support. This is here demonstrated for the model case of Fe-phthalocyanine molecules adsorbed on the Au(110) surface. Scanning tunneling microscopy shows that molecular adsorption promotes a local (1 × 5) surface reconstruction, which drives the assembly of molecular chains along the [11̅0] direction. The order and periodicity of the molecular assemblies are determined with low energy electron diffraction patterns. Density functional theory calculations reveal the energetic origins of the molecule-driven substrate reconstruction. Since the function of molecular overlayers at surfaces is strongly correlated to their structure, these results have implications in the design of new metal/molecular interfaces.

Iron and cobalt phthalocyanines assemble on the Au(110) surface lying parallel to the surface, as deduced by near-edge X-ray absorption fine structure (NEXAFS) taken with linearly polarized radiation at the C and N K edges. The molecular chains, firmly anchored to the underlying metal surface, arrange into long-range ordered rows with a (5 × 3) symmetry along the [001] azimuthal direction at completion of the first single layer. The interaction process is mainly determined by the d orbitals associated with the central Fe and Co atoms, as observed by valence band photoemission and NEXAFS at the Fe and Co L2,3edges. The spin and orbital configuration of the FePc and CoPc molecules is strongly influenced by the interface with a charge transfer from the underlying metal to the out-of-plane empty states located at the Fe and Co centers of the molecules. This interaction process induces electronic states located at the interface, localized on the central metal atoms and close to the Fermi level (0.2 eV binding energy for FePc and 0.7 eV for CoPc) without energy dispersion, as deduced by angular-resolved photoemission. On the contrary, a delocalized state has been observed with dispersion along the molecular chains, mainly due to the overlapping of the π charge of the macrocycles ligands mediated by the Au substrate.

Metal phthalocyanine (MPc, with M = Fe, Co, Ni, Cu, Zn) thin-films grown on Au(110) have been electron-doped by exposition to alkali metal (potassium). Progressive occupation of the former lowest unoccupied molecular orbital (LUMO) up to the filling of the 2-fold degenerate LUMO with 2egsymmetry has been observed in photoemission spectra for the NiPc, CuPc, and ZnPc films. The evolution of the electron filling induces a different process for FePc and CoPc, whose empty electronic states localized on the central metal atoms are involved in the electron donation process by the alkali metal. Electron filling is accompanied by a sudden decrease of the work function mainly due to a variation of the surface dipole. The molecular films remain semiconducting, with the hole injection barrier strongly reduced at saturation of the electron filling. The selective influence of the electron donation process on the molecular states (ligands, metal-related) is discussed.

The energetic, the morphology, the interface dipole formation, and the electronic states of pentacene grown on a self-assembled monolayer (SAM) of benzenethiolate on the Cu(100) surface are investigated by complementary structural and spectroscopic techniques. The growth morphology of the heterostructure has been investigated by atomic force microscopy (AFM), low-energy electron diffraction (LEED), Auger electron spectroscopy (AES), and photoemission spectroscopy, inferring tightly packed arrangement of grains constituted of pentacene molecules with nearly perpendicular orientation, when a single-layer is deposited on top of the benzenethiolate-SAM. The adsorption energy of the pentacene single layer on the benzenethiolate buffer layer (Ea1.16 eV = 112 kJ/mol) is found much weaker than for pentacene on the copper surface, as estimated by thermal desorption spectroscopy (TDS). The evolution of the spectral density of electronic states in the valence band, obtained by high-resolution ultraviolet photoelectron spectroscopy (HR-UPS), confirms the weak interaction of the pentacene molecules with the benzenethiolate-SAM and the formation of a semiconducting heterostructure, with a hole injection barrier reduced to 0.95 eV with respect to the pentacene/Cu interface.