A. Verdini - Academia.edu (original) (raw)
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Papers by A. Verdini
Studies of NO decomposition on Pd/catalysts were made. The reaction was investigated at 400 • C u... more Studies of NO decomposition on Pd/catalysts were made. The reaction was investigated at 400 • C using a reactant mixture of 1100 ppm NO in He. Adsorption and dissociation of NO, O 2 and N 2 on Pd(1 1 1), MoO x -Pd(1 1 1) and MoO x -␥Al 2 O 3 surfaces have been investigated using a molecular orbital approach of the extended Hückel (EHMO) type, including repulsion terms.
Thin Solid Films, 2001
NiO ultrathin films have been grown on Ag(001) by Ni deposition in an O atmosphere. The thickness... more NiO ultrathin films have been grown on Ag(001) by Ni deposition in an O atmosphere. The thickness range 5-50 ML has 2 been investigated. X-ray photoelectron spectroscopy has been used to study the stoichiometric composition and chemical purity of the oxide films. We found completely oxidized stoichiometric NiO films. Their contamination has been found to be limited to the topmost layers. Photoelectron diffraction has given information concerning the local crystal structure of the films. The film atomic geometry has been found to be the same independent of thickness in the 0-50 ML range. The films have the expected (001) rock-salt structure with the same in plane orientation as the Ag(001) substrate. Specular X-ray reflectivity has allowed a very accurate thickness evaluation and has given information on the width of the density gradients at the film-substrate and vacuum-film interfaces, found to be of the order of a few atomic layers. ᮊ
Surface Review and Letters, 2002
CoO layers have been grown by exposing to oxygen the (001) body-centered-tetragonal (bct) surface... more CoO layers have been grown by exposing to oxygen the (001) body-centered-tetragonal (bct) surface of a Co ultrathin film epitaxially grown on Fe(001). Different oxide thicknesses in the 2-15 ML range have been investigated by means of synchrotron-radiation-based techniques. X-ray photoelectron spectroscopy has been used to check the formation of the oxide films; X ray photoelectron diffraction has given information
Journal of Electron Spectroscopy and Related Phenomena, 2002
The angular distribution of the intensity in photoemission experiments is affected by electron di... more The angular distribution of the intensity in photoemission experiments is affected by electron diffraction patterns and by a smoothly varying contribution originated by both intrumental details and physical properties of the samples. The peculiar variety of scattering configurations available at the ALOISA beamline experimental station in Trieste stimulated the developement of an analytical description for the smooth angular dependence sustaining the diffraction features. We present here the basic formulae and their application to experimental data taken on the Fe/Cu3Au(001) system in order to highlight the role of the various parameters included in the distribution function. A specific model for the surface illumination has been developed as well as the overlayer thickness and surface roughness have been considered.
The Journal of Chemical Physics, 2005
Core level and valence band photoemission measurements combined with near edge x-ray absorption f... more Core level and valence band photoemission measurements combined with near edge x-ray absorption fine structure measurements were performed on a single C(70) layer adsorbed on polycrystalline Al (1 ML-C(70)/Al) (ML-monolayer), pure and doped with sodium atoms. The data obtained from the pure ML chemisorbed on Al surface show a semiconducting behavior of the system, which is characterized by a covalent bond between the adsorbate and the substrate. The same data show also that the C(70) molecules tend to orient themselves with the C(5v) axis perpendicular to the surface in analogy to what observed for 1 ML-C(70)/Cu(111). By doping the sample with sodium atoms a charge transfer from the alkali atoms to the lowest unoccupied molecular orbital (LUMO) of the C(70) molecules takes place, as underlined by the gradual increasing intensity of the C(70) LUMO peak as a function of doping. Nevertheless, no metallic phases are observed for any doping step.
Surface Science, 2006
Here we demonstrate that a molecular dye film composed by a single layer of C 70 and a single lay... more Here we demonstrate that a molecular dye film composed by a single layer of C 70 and a single layer of Zn-Tetraphenyl-porhyrin (ZnTPP) adsorbed atop can be grown on large substrates using molecular beam epitaxy. The electrostatic interactions between the constituent molecules drive the formation of this ordered donor-acceptor layer. The overlapping between the !* orbitals of ZnTPP and C 70 allows the delocalisation of the excited electrons from the excited molecule on a timescale of ~ 6 fs. Generally, the ZnTPP/C 70 film, acting as a p-n junction, delocalise more efficiently the excited electrons as compared to pure ZnTPP films on a timescale that competes effectively against loss processes, suggesting its application for a more efficient solar energy conversion in organicbased devices.
Studies of NO decomposition on Pd/catalysts were made. The reaction was investigated at 400 • C u... more Studies of NO decomposition on Pd/catalysts were made. The reaction was investigated at 400 • C using a reactant mixture of 1100 ppm NO in He. Adsorption and dissociation of NO, O 2 and N 2 on Pd(1 1 1), MoO x -Pd(1 1 1) and MoO x -␥Al 2 O 3 surfaces have been investigated using a molecular orbital approach of the extended Hückel (EHMO) type, including repulsion terms.
Thin Solid Films, 2001
NiO ultrathin films have been grown on Ag(001) by Ni deposition in an O atmosphere. The thickness... more NiO ultrathin films have been grown on Ag(001) by Ni deposition in an O atmosphere. The thickness range 5-50 ML has 2 been investigated. X-ray photoelectron spectroscopy has been used to study the stoichiometric composition and chemical purity of the oxide films. We found completely oxidized stoichiometric NiO films. Their contamination has been found to be limited to the topmost layers. Photoelectron diffraction has given information concerning the local crystal structure of the films. The film atomic geometry has been found to be the same independent of thickness in the 0-50 ML range. The films have the expected (001) rock-salt structure with the same in plane orientation as the Ag(001) substrate. Specular X-ray reflectivity has allowed a very accurate thickness evaluation and has given information on the width of the density gradients at the film-substrate and vacuum-film interfaces, found to be of the order of a few atomic layers. ᮊ
Surface Review and Letters, 2002
CoO layers have been grown by exposing to oxygen the (001) body-centered-tetragonal (bct) surface... more CoO layers have been grown by exposing to oxygen the (001) body-centered-tetragonal (bct) surface of a Co ultrathin film epitaxially grown on Fe(001). Different oxide thicknesses in the 2-15 ML range have been investigated by means of synchrotron-radiation-based techniques. X-ray photoelectron spectroscopy has been used to check the formation of the oxide films; X ray photoelectron diffraction has given information
Journal of Electron Spectroscopy and Related Phenomena, 2002
The angular distribution of the intensity in photoemission experiments is affected by electron di... more The angular distribution of the intensity in photoemission experiments is affected by electron diffraction patterns and by a smoothly varying contribution originated by both intrumental details and physical properties of the samples. The peculiar variety of scattering configurations available at the ALOISA beamline experimental station in Trieste stimulated the developement of an analytical description for the smooth angular dependence sustaining the diffraction features. We present here the basic formulae and their application to experimental data taken on the Fe/Cu3Au(001) system in order to highlight the role of the various parameters included in the distribution function. A specific model for the surface illumination has been developed as well as the overlayer thickness and surface roughness have been considered.
The Journal of Chemical Physics, 2005
Core level and valence band photoemission measurements combined with near edge x-ray absorption f... more Core level and valence band photoemission measurements combined with near edge x-ray absorption fine structure measurements were performed on a single C(70) layer adsorbed on polycrystalline Al (1 ML-C(70)/Al) (ML-monolayer), pure and doped with sodium atoms. The data obtained from the pure ML chemisorbed on Al surface show a semiconducting behavior of the system, which is characterized by a covalent bond between the adsorbate and the substrate. The same data show also that the C(70) molecules tend to orient themselves with the C(5v) axis perpendicular to the surface in analogy to what observed for 1 ML-C(70)/Cu(111). By doping the sample with sodium atoms a charge transfer from the alkali atoms to the lowest unoccupied molecular orbital (LUMO) of the C(70) molecules takes place, as underlined by the gradual increasing intensity of the C(70) LUMO peak as a function of doping. Nevertheless, no metallic phases are observed for any doping step.
Surface Science, 2006
Here we demonstrate that a molecular dye film composed by a single layer of C 70 and a single lay... more Here we demonstrate that a molecular dye film composed by a single layer of C 70 and a single layer of Zn-Tetraphenyl-porhyrin (ZnTPP) adsorbed atop can be grown on large substrates using molecular beam epitaxy. The electrostatic interactions between the constituent molecules drive the formation of this ordered donor-acceptor layer. The overlapping between the !* orbitals of ZnTPP and C 70 allows the delocalisation of the excited electrons from the excited molecule on a timescale of ~ 6 fs. Generally, the ZnTPP/C 70 film, acting as a p-n junction, delocalise more efficiently the excited electrons as compared to pure ZnTPP films on a timescale that competes effectively against loss processes, suggesting its application for a more efficient solar energy conversion in organicbased devices.