ABSTRACT Thin films of titanium oxide TiO2 have been grown on Fe(001) substrates by means of reac... more ABSTRACT Thin films of titanium oxide TiO2 have been grown on Fe(001) substrates by means of reactive deposition at different temperatures. X-ray photoemission spectroscopy and low-energy electron diffraction have been employed to investigate the electronic and structural properties of the TiO2/Fe interfaces. We observe that perfectly stoichiometric TiO2 films can be obtained, at a growth temperature of 300 °C, only at the expense of a great interfacial mixing, eventually leading to the formation of a thick Fe oxide layer on top of the deposited TiO2. The interfacial reactions are significantly reduced when the growth is performed at room temperature, where more defective films develop.
ABSTRACT http://onlinelibrary.wiley.com/doi/10.1002/adfm.201301892/abstract A major challenge in ... more ABSTRACT http://onlinelibrary.wiley.com/doi/10.1002/adfm.201301892/abstract A major challenge in molecular electronics is to develop logic devices based on a truly intramolecular switching mechanism. Recently, a new type of molecular device has been proposed where the switching characteristic is mediated by the bistability in the position of the two hydrogen atoms which can occupy different, energetically equivalent positions (tautomeriza- tion) in the inner cavity of porphyrins and naphthalocyanines. Up to now, such a reaction has only been exploited at low temperatures and induced or detected through atomic scale manipulation. In addition, the unpredict- ability of the tautomer orientation currently excludes molecular intercon- nection to functional electronic circuits. Here, full evidence is provided that, following a newly proposed growth strategy, 2D layers of metal-free tetraphenylporphyrins (H2TPP) show frozen tautomerization even at room temperature on macroscopic domains, with the H atoms aligned along a direction settled a priori. This behavior is ascribed to the buckling of the molecule, anchored to the substrate, which removes the degeneracy between the two tautomer alignments. On this basis, a new way to exploit uniaxially oriented H2TPP tautomers in a first elementary logic device is proposed.
ABSTRACT In an ordered porphyrin molecular array, the tautomerism reaction is frozen at room temp... more ABSTRACT In an ordered porphyrin molecular array, the tautomerism reaction is frozen at room temperature. In particular, G. Bussetti et al. use the H‐H tautomer alignment as a logic device (1/0 states) on page 958 by perturbing the inner cavity of the molecule. The state flip is readable by an optical probe.
We have investigated the formation of scanning tunneling microscopy (STM) atomically resolved ima... more We have investigated the formation of scanning tunneling microscopy (STM) atomically resolved images of the Fe(001)-p(1×1)O surface. The latter is characterized by a high in-plane symmetry for both oxygen and iron atoms, thus representing a very appealing template for understanding how to distinguish between oxygen and metal atoms in STM images of an oxidized metal surface. We report on the
ABSTRACT Nickel-iron interfacial intermixing, resulting from annealing ultrathin Ni films grown o... more ABSTRACT Nickel-iron interfacial intermixing, resulting from annealing ultrathin Ni films grown on Fe(001), has been investigated by low-energy electron diffraction, Auger electron spectroscopy and scanning tunnelling microscopy. The Ni/Fe interface has been found to be highly unstable at relatively low annealing temperatures, with dramatic thermal effects on the surface morphology of the Ni/Fe(001) epitaxial films.
ABSTRACT Thin films of titanium oxide TiO2 have been grown on Fe(001) substrates by means of reac... more ABSTRACT Thin films of titanium oxide TiO2 have been grown on Fe(001) substrates by means of reactive deposition at different temperatures. X-ray photoemission spectroscopy and low-energy electron diffraction have been employed to investigate the electronic and structural properties of the TiO2/Fe interfaces. We observe that perfectly stoichiometric TiO2 films can be obtained, at a growth temperature of 300 °C, only at the expense of a great interfacial mixing, eventually leading to the formation of a thick Fe oxide layer on top of the deposited TiO2. The interfacial reactions are significantly reduced when the growth is performed at room temperature, where more defective films develop.
Journal of physics. Condensed matter : an Institute of Physics journal, Jan 5, 2014
We investigated the room temperature oxidation of ultra-thin Ni and Cr films grown on Fe(0 0 1). ... more We investigated the room temperature oxidation of ultra-thin Ni and Cr films grown on Fe(0 0 1). In particular, we characterized the degree of crystallinity and the stoichiometry of the oxide layers and addressed the chemical stability of the interface with the highly reactive Fe substrate by means of low-energy electron diffraction and x-ray and UV photoemission spectroscopy. In the Ni case we detected, upon oxidation, the formation of a Fe(3)O(4) layer covering the Ni oxide, due to the diffusion of Fe cations towards the surface. At high temperature and in ultra-high vacuum conditions, the Ni oxide dissolved and the Fe oxide layer was reduced to FeO. In the Cr case, we observed the formation of a thin Cr(2)O(3) oxide layer, showing a diffraction pattern compatible with a defective γ-Cr(2)O(3) phase. A thicker Cr oxide layer could be produced by oxidizing the sample at 300 °C, at the expense of the incorporation of trace amounts of Fe cations.
ABSTRACT Thin films of titanium oxide TiO2 have been grown on Fe(001) substrates by means of reac... more ABSTRACT Thin films of titanium oxide TiO2 have been grown on Fe(001) substrates by means of reactive deposition at different temperatures. X-ray photoemission spectroscopy and low-energy electron diffraction have been employed to investigate the electronic and structural properties of the TiO2/Fe interfaces. We observe that perfectly stoichiometric TiO2 films can be obtained, at a growth temperature of 300 °C, only at the expense of a great interfacial mixing, eventually leading to the formation of a thick Fe oxide layer on top of the deposited TiO2. The interfacial reactions are significantly reduced when the growth is performed at room temperature, where more defective films develop.
ABSTRACT http://onlinelibrary.wiley.com/doi/10.1002/adfm.201301892/abstract A major challenge in ... more ABSTRACT http://onlinelibrary.wiley.com/doi/10.1002/adfm.201301892/abstract A major challenge in molecular electronics is to develop logic devices based on a truly intramolecular switching mechanism. Recently, a new type of molecular device has been proposed where the switching characteristic is mediated by the bistability in the position of the two hydrogen atoms which can occupy different, energetically equivalent positions (tautomeriza- tion) in the inner cavity of porphyrins and naphthalocyanines. Up to now, such a reaction has only been exploited at low temperatures and induced or detected through atomic scale manipulation. In addition, the unpredict- ability of the tautomer orientation currently excludes molecular intercon- nection to functional electronic circuits. Here, full evidence is provided that, following a newly proposed growth strategy, 2D layers of metal-free tetraphenylporphyrins (H2TPP) show frozen tautomerization even at room temperature on macroscopic domains, with the H atoms aligned along a direction settled a priori. This behavior is ascribed to the buckling of the molecule, anchored to the substrate, which removes the degeneracy between the two tautomer alignments. On this basis, a new way to exploit uniaxially oriented H2TPP tautomers in a first elementary logic device is proposed.
ABSTRACT In an ordered porphyrin molecular array, the tautomerism reaction is frozen at room temp... more ABSTRACT In an ordered porphyrin molecular array, the tautomerism reaction is frozen at room temperature. In particular, G. Bussetti et al. use the H‐H tautomer alignment as a logic device (1/0 states) on page 958 by perturbing the inner cavity of the molecule. The state flip is readable by an optical probe.
We have investigated the formation of scanning tunneling microscopy (STM) atomically resolved ima... more We have investigated the formation of scanning tunneling microscopy (STM) atomically resolved images of the Fe(001)-p(1×1)O surface. The latter is characterized by a high in-plane symmetry for both oxygen and iron atoms, thus representing a very appealing template for understanding how to distinguish between oxygen and metal atoms in STM images of an oxidized metal surface. We report on the
ABSTRACT Nickel-iron interfacial intermixing, resulting from annealing ultrathin Ni films grown o... more ABSTRACT Nickel-iron interfacial intermixing, resulting from annealing ultrathin Ni films grown on Fe(001), has been investigated by low-energy electron diffraction, Auger electron spectroscopy and scanning tunnelling microscopy. The Ni/Fe interface has been found to be highly unstable at relatively low annealing temperatures, with dramatic thermal effects on the surface morphology of the Ni/Fe(001) epitaxial films.
ABSTRACT Thin films of titanium oxide TiO2 have been grown on Fe(001) substrates by means of reac... more ABSTRACT Thin films of titanium oxide TiO2 have been grown on Fe(001) substrates by means of reactive deposition at different temperatures. X-ray photoemission spectroscopy and low-energy electron diffraction have been employed to investigate the electronic and structural properties of the TiO2/Fe interfaces. We observe that perfectly stoichiometric TiO2 films can be obtained, at a growth temperature of 300 °C, only at the expense of a great interfacial mixing, eventually leading to the formation of a thick Fe oxide layer on top of the deposited TiO2. The interfacial reactions are significantly reduced when the growth is performed at room temperature, where more defective films develop.
Journal of physics. Condensed matter : an Institute of Physics journal, Jan 5, 2014
We investigated the room temperature oxidation of ultra-thin Ni and Cr films grown on Fe(0 0 1). ... more We investigated the room temperature oxidation of ultra-thin Ni and Cr films grown on Fe(0 0 1). In particular, we characterized the degree of crystallinity and the stoichiometry of the oxide layers and addressed the chemical stability of the interface with the highly reactive Fe substrate by means of low-energy electron diffraction and x-ray and UV photoemission spectroscopy. In the Ni case we detected, upon oxidation, the formation of a Fe(3)O(4) layer covering the Ni oxide, due to the diffusion of Fe cations towards the surface. At high temperature and in ultra-high vacuum conditions, the Ni oxide dissolved and the Fe oxide layer was reduced to FeO. In the Cr case, we observed the formation of a thin Cr(2)O(3) oxide layer, showing a diffraction pattern compatible with a defective γ-Cr(2)O(3) phase. A thicker Cr oxide layer could be produced by oxidizing the sample at 300 °C, at the expense of the incorporation of trace amounts of Fe cations.
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Papers by A. Brambilla