J. Martínez-Blanco

Universidad Autónoma de Madrid, Madrid, Madrid, Spain

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Publications (17)35.55 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Using scanning tunneling microscopy, we show that coronene molecules form supramolecular structures upon room-temperature deposition on Ge(111), in full commensurability with the c(2 × 8) reconstruction of the clean surface. The molecules are not adsorbed in a planar manner in the first layer; the balance between lateral intermolecular interactions and directional bonding to the surface forces them into a tilted configuration. Further coronene deposition leads to the formation of large domains of weakly bonded molecules adsorbed on top of the first layer. The ordering of the second layer is dictated by both, the first layer of molecules and the unaltered reconstructed substrate underneath. We provide a detailed analysis of the encountered molecular periodicities and discuss the mechanisms that lead to long-range ordering in these layers.
    The Journal of Physical Chemistry C. 05/2014; 118(22):11699–11703.
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    ABSTRACT: Vicinal Cu(100) surfaces with different miscut angles and terrace widths are studied by angle resolved photoemission spectroscopy. The Tamm M¯-point d-like surface state is strongly affected by the super periodic potential induced by the regular array of steps, as it shifts away from the Fermi level and its bandwidth is reduced. For smaller terraces, several replicas are observed, proving that the Tamm surface state is sensitive to the new superperiodic potential. For the largest terraces, the Tamm state starts splitting into incipient and non-dispersing quantum well states, indicating that a transition into a localized regime takes place as a function of terrace width. The results are rationalized using a Kronig–Penney model to simulate the step superperiodicity.
    Surface Science. 01/2014; 630:144–152.
  • Jesús Martínez-Blanco, Arantzazu Mascaraque, Yuriy S Dedkov, Karsten Horn
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    ABSTRACT: The adsorption of coronene molecules (C(24)H(12)) on the Ge(001) surface has been studied by means of scanning tunnelling microscopy (STM). Upon room temperature deposition, the coronene molecules adsorb in an upright geometry forming compact layers patterned in rows for coverages of one monolayer and less, being the only example investigated so far in which a pure aromatic hydrocarbon forms a well-ordered monolayer on a non-passivated semiconductor surface. At half monolayer, the molecular rows consist of long chains of π-stacked molecules and the distance between molecular planes is 8 Å. This configuration is maintained upon cooling the system below the transition temperature of Ge(001) (~220 K), but the molecular layer experiences also a transition from rows perpendicular to rows parallel to the Ge dimer rows. We interpret our observations in terms of a weak bonging between molecules and substrate, which facilitates the formation of large ordered domains of molecules, revealing Ge(001) as an ideal template for the growth of this and other aromatic hydrocarbons.
    Langmuir 02/2012; 28(8):3840-4. · 4.38 Impact Factor
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    ABSTRACT: We investigate the structural phase transition (3√2×√2)R45°↔(√2×√2)R45° of 0.5 ML Sn/Cu(001) using a combination of scanning tunneling microscopy, time-of-flight direct-recoil spectroscopy, and Monte Carlo simulations. Cu vacancies are observed for both phases. At low temperature, Cu vacancies are ordered in a regular array of lines. At high temperature, Sn atoms occupy similar adsorption sites as at low temperature but Cu vacancies are disordered. We conclude that the atomistic mechanism behind the structural phase transition is an order/disorder transition driven by the Cu-vacancy entropy.
    Physical Review B 07/2010; 82(3). · 3.66 Impact Factor
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    J. Martínez-Blanco, M. Klingsporn, K. Horn
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    ABSTRACT: The adsorption of coronene (C24H12) on the Si(1 1 1)-(7 × 7) surface is studied using scanning tunneling microscopy (STM). Upon room temperature submonolayer deposition, we find that the coronene molecules preferentially adsorb on the unfaulted half of the 7 × 7 unit cell. Molecules adsorbed on different sites can be induced to move to the preferential sites by the action of the tip in repeated image scans. Imaging of the molecules is strongly bias dependent, and also critically depends on the adsorption site. We analyze the results in terms of differential bonding strength for the different adsorption sites and we identify those substrate atoms which participate in the bonding with the molecule.
    Surface Science 01/2010; · 1.84 Impact Factor
  • V Joco, J Martínez-Blanco, P Segovia, I Vobornik, E G Michel
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    ABSTRACT: We report an investigation into the surface electronic structure of Pb/Cu(100) in the submonolayer coverage range. A prominent surface band is detected in the whole coverage range analysed. The band is gradually filled as Pb coverage increases. For a Pb coverage of 0.375 ML, corresponding to the c(4 × 4) phase, a strong c(4 × 4) folding of this state is observed in the valence band. The origin of these results and the nature of the surface electronic structure of Pb/Cu(100)- c(4 × 4) are discussed.
    Journal of Physics Condensed Matter 11/2009; 21(47):474216. · 2.22 Impact Factor
  • J Martínez-Blanco, V Joco, C Quirós, P Segovia, E G Michel
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    ABSTRACT: The application of genetic algorithms to the analysis of surface x-ray diffraction data is discussed and the implementation of a genetic algorithm of evolutionary type is described in detail. The structure of Sn/Cu(100)-[Formula: see text] is determined on the basis of surface x-ray diffraction data analysed using this algorithm. The results are compared to previous findings using other techniques.
    Journal of Physics Condensed Matter 04/2009; 21(13):134011. · 2.22 Impact Factor
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    ABSTRACT: The authors report an investigation on the adsorption of pentacene molecules on Cu(110) in the submonolayer and monolayer ranges using scanning tunneling microscopy and low-energy electron diffraction. They identify and characterize three different phases for increasing pentacene coverage. For very low coverages [ <sup>></sup><sub>~</sub>0.1 ML (monolayer)] pentacene molecules are highly mobile and adsorbed uniaxially oriented along the [1 1 0] substrate direction. For higher coverages the ordering along the [001] direction improves, until a p(7×2) structure with imperfect registry along the [1 1 0] direction is formed at 0.89 ML. In both phases pentacene molecules occupy the Cu(110) troughs along the [1 1 0] direction. For even higher coverage (1.0 ML), a slight rotation of the molecular adsorption site gives rise to a complex ( 6 1 -1 4 ) structure based in a c(12×2) cell. The appearance of two domains generates a long-range wavelike ordering. Annealing of the adlayer results in the formation of supramolecular complexes.
    Journal of vacuum science & technology. B, Microelectronics and nanometer structures: processing, measurement, and phenomena: an official journal of the American Vacuum Society 04/2009; · 1.36 Impact Factor
  • J Martínez-Blanco, V Joco, J Fujii, P Segovia, E G Michel
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    ABSTRACT: We present measurements of the Fermi surface and underlying band structure of Sn/Cu(100)-[Formula: see text]. This phase is observed for a coverage of 0.60-0.65 monolayers. Its electronic structure is characterized by a free-electron-like surface band folded with the reconstruction periodicity. At variance with other surface phases of Sn on Cu(100), no temperature-induced phase transition is observed for this phase from 100 K up to the desorption of Sn.
    Journal of Physics Condensed Matter 02/2009; 21(5):055001. · 2.22 Impact Factor
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    ABSTRACT: The structural and electronic properties of the (3√2×√2)R45° phase of 0.5 monolayers of Sn on Cu(100) have been investigated using a combination of scanning tunneling microscopy experiments and total-energy-minimization calculations. Theory and experiment support the missing-row surface-alloy structure as the ground state for this surface [ K. Pussi, E. Al Shamaileh, E. McLoughin, A. A. Cafolla and M. Lindroos Surf. Sci. 549 24 (2004)]. The calculated electronic structure reproduces almost perfectly both the experimental scanning tunneling microscopy images and the observed electronic bands. Our results conclusively indicate that the creation of Cu vacancies in the top surface layer produces a significant reduction of the total energy. We also report a metastable (3√2×√2)R45° phase coexisting with the ground state at room temperature, which we attribute to a two-missing-row surface-alloy structure.
    Physical Review B 01/2009; 80(11). · 3.66 Impact Factor
  • J. Martínez-Blanco, V. Joco, J. Fujii, P. Segovia, E. G. Michel
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    ABSTRACT: We present measurements of the Fermi surface and underlying band structure of Sn/Cu(100)-(2\sqrt {2}\times 2\sqrt {2})\mathrm {R}45^{\circ } . This phase is observed for a coverage of 0.60-0.65 monolayers. Its electronic structure is characterized by a free-electron-like surface band folded with the reconstruction periodicity. At variance with other surface phases of Sn on Cu(100), no temperature-induced phase transition is observed for this phase from 100 K up to the desorption of Sn.
    Journal of Physics Condensed Matter 01/2009; 21(5). · 2.22 Impact Factor
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    ABSTRACT: PMID: 18205525 [PubMed].-- Original paper: "Electronic structure of C60 on Au(887)" published on 13/10/2006 in J. Chem. Phys. 125, 144719 (2006), available at: http://dx.doi.org/10.1063/1.2354082. Schiessling and Brühwiler question the validity of the results by Schiller et al. and suggested that the throughput correction and the Fermi level placement are erroneous. Below, we rule out both scenarios. This work was financed as part of the European Science Foundation EUROCORES Programme SONS (MAT2002-12241-E and MAT2002-11975-E) and a Marie Curie Intra-European fellowship within the sixth European Community framework programme. Further support was obtained from the Comunidad Autónoma de Madrid (Grant No. GR-MAT/0022/2004). The synchrotron access was supported by the European Community-Research Infrastructure Action under the FP6 “Structuring the European Research Area” Programme (through the key actions (i) Integrated Infrastructure Initiative “Integrating Activity on Synchrotron and Free Electron Laser Science” and (ii) Strengthening the European Research Area, Research Infrastructures Contract No. (RII3-CT-2004-506008)). Peer reviewed
    The Journal of Chemical Physics 02/2008; 128(3):037101. · 3.12 Impact Factor
  • J. Martínez-Blanco, V. Joco, J. Fujii, P. Segovia, E. G. Michel
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    ABSTRACT: The surface phase Sn∕Cu(100)-(3√2×√2)R45° exhibits a temperature induced phase transition to a (√2×√2)R45° phase above 360 K. We report an angle-resolved photoemission study of the two-dimensional Fermi surface of the low-temperature phase. The Fermi surface is formed by folding of a quasi-two-dimensional surface band and presents three contours. It is characterized by gaps appearing in optimally nested regions of one of the contours, whereas other sections remain ungapped. We address the origin of the folding and of the surface phase transition, which is attributed to the formation of a surface charge density wave.
    Phys. Rev. B. 01/2008; 77(19).
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    ABSTRACT: We present an analysis of the electronic structure of C60 adsorbed on a vicinal Au(111) surface at different fullerene coverages using photoemission, x-ray absorption, and scanning tunneling microscopy/spectroscopy (STS). STS provides a straightforward determination of the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) levels with respect to the Fermi energy. At C60 coverages of 0.5 and 1 ML a 2.7 eV wide HOMO-LUMO gap is found. The near-edge x-ray absorption fine structure (NEXAFS) spectrum for the 0.5 ML C60 nanomesh structure displays a significant intensity at the low energy side of the LUMO exciton peak, which is explained as due to absorption into HOMO-LUMO gap states localized at individual C60 cluster edges. From 0.5 to 1 ML we observe a rigid shift of the HOMO-LUMO peaks in the STS spectra and an almost complete quenching of the gap states feature in NEXAFS.
    The Journal of Chemical Physics 11/2006; 125(14):144719. · 3.12 Impact Factor
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    ABSTRACT: The c(5√2×√2)R45°-Pb/Cu(100) surface phase is investigated by means of angle resolved ultraviolet photoemission and low energy electron diffraction in the temperature range between 300 and 550K. We identify and characterize a temperature-induced surface phase transition at 440K from the room temperature c(5√2×√2) R45° phase to a (√2×√2)R45° structure with split superstructure spots. The phase transition is fully reversible and takes place before the two-dimensional melting of the structure at 520K. The electronic structure of the split (√2×√2)R45° phase is characterized by a metallic free-electron like surface band. This surface band is backfolded with c(5√2×√2)R45° periodicity phase at room temperature, giving rise to a surface band gap at the Fermi energy. We propose that a gain in electronic energy explains in part the stability of the c(5√2×√2)R45° phase.
    Surface Science 01/2006; 600(18):3851-3855. · 1.84 Impact Factor
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    ABSTRACT: Room temperature deposition of Sn on Cu(100) gives rise to a rich variety of surface reconstructions in the submonolayer coverage range. In this work, we report a detailed investigation on the phases appearing and their temperature stability range by using low-energy electron diffraction and surface X-ray diffraction. Previously reported reconstructions in the submonolayer range are p(2×2) (for 0.2ML), p(2×6) (for 0.33ML), (32×2)R45° (for 0.5ML), and c(4×4) (for 0.65ML). We find a new phase with a −4204 structure for a coverage of 0.45ML. Furthermore, we analyze the temperature stability of all phases. We find that two phases exhibit a temperature induced reversible phase transition: the (32×2)R45° phase becomes (2×2)R45° phase above 360K, and the new −4204 phase becomes p(2×2) also above 360K. The origin of these two-phase transitions is discussed.
    Applied Surface Science - APPL SURF SCI. 01/2006; 252(15):5331-5334.
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    ABSTRACT: We identify and characterize a two-dimensional phase transition in a layer of Sn on Cu(100). The stable phase at room temperature has a (3√2×√2)R45° structure. Above ∼360 K, a new phase with (√2×√2)R45° structure is formed. The high-temperature phase exhibits a quasi-two-dimensional free-electron surface band, with Fermi surface nesting in excellent agreement with the three-times larger periodicity of the low-temperature phase. A momentum-dependent band gap opens along the nested areas of the Fermi surface in the low-temperature phase. The phase transition is a clear experimental confirmation of the role of Fermi-surface gapping and nesting in the stabilization of a commensurate two-dimensional phase, which is interpreted as a charge-density wave.
    Physical Review B 01/2005; 72(4). · 3.66 Impact Factor

Publication Stats

47 Citations
35.55 Total Impact Points

Institutions

  • 2005–2014
    • Universidad Autónoma de Madrid
      • Department of Condensed Matter Physics
      Madrid, Madrid, Spain
  • 2010–2012
    • Fritz Haber Institute of the Max Planck Society
      Berlín, Berlin, Germany