Peer-reviewed Publications |
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Alarcón, L. S., Cristina, L. J., Jia, J., Chen, L., Giglia, A., Pasquali, L., Sánchez, E. A., Esaulov, V. A., & Grizzi, O. (2017). Adsorption and thermal stability of 1,4 benzenedimethanethiol on InP(110). Surface Science, 664, 101–109.
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Cartry G., Kogut D., Achkasov K., Layet J.M., Farley T., Gicquel A., Achard J., Brinza O., Bieber T., Khemliche H., Roncin P., & Simonin A. (2017). Alternative solutions to caesium in negative-ion sources: a study of negative-ion surface production on diamond in H2/D2 plasmas. New J. Phys., 19(2), 025010.
Résumé: This paper deals with a study of H−/D− negative ion surface production on diamond in low pressure
H2/D2 plasmas. A sample placed in the plasma is negatively biased with respect to plasma potential.
Upon positive ion impacts on the sample, some negative ions are formed and detected according to
their mass and energy by a mass spectrometer placed in front of the sample. The experimental
methods developed to study negative ion surface production and obtain negative ion energy and angle
distribution functions are first presented. Different diamond materials ranging from nanocrystalline
to single crystal layers, either doped with boron or intrinsic, are then investigated and compared with
graphite. The negative ion yields obtained are presented as a function of different experimental
parameters such as the exposure time, the sample bias which determines the positive ion impact
energy and the sample surface temperature. It is concluded from these experiments that the electronic
properties of diamond materials, among them the negative electron affinity, seem to be favourable for
negative-ion surface production. However, the negative ion yield decreases with the plasma induced
defect density.
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Correa-Puerta, J., Del Campo, V., Henriquez, R., Esaulov, V. A., Hamoudi, H., Flores, M., & Haberle, P. (2017). Unoccupied Interface and Molecular States in Thiol and Dithiol Monolayers. Langmuir, 33(43), 12056–12064.
Résumé: The electronic structure of self-assembled monolayers (SAMs) formed by thiols of different lengths and dithiol molecules bound to Au(111) has been characterized. Inverse photoemission spectroscopy (IPES) and density functional theory have been used to describe the molecule/Au substrate system. All molecular layers display a clear signal in the IPES data at the edge of the lowest unoccupied system orbital (LUSO), roughly 3 eV above the Fermi level. There is also evidence, in both the experimental data and the calculation, of a finite density of states just below the LUSO edge, which has been recognized as localized at the Au-substrate interface. Regardless of the molecular lengths and in addition to this induced density of interface states, an apparent antibonding Au-S state has been identified in the IPES data for both molecular systems. The main difference between the electronic structures of thiol and dithiol SAMs is a shift in the energy of the antibonding state.
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Debiossac, M., Atkinson, P., Zugarramurdi, A., Eddrief, M., Finocchi, F., Etgens, V. H., Momeni, A., Khemliche, H., Borisov, A. G., & Roncin, P. (2017). Fast atom diffraction inside a molecular beam epitaxy chamber, a rich combination. Appl. Surf. Sci., 391, 53–58.
Résumé: brief oveview of the benefit of having a grazing incidence fast atom diffraction (GIFAD) setup inside a molecular beam eppitaxy setup.
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Houdoux, D., Houplin, J., Amiaud, L., Lafosse, A., & Dablemont, C. (2017). Interfacial water on organic substrates at cryogenic temperatures: hydrogen bonding and quantification in the submonolayer regime. Phys Chem Chem Phys, 19(3), 2304–2312.
Résumé: Water molecules were used to probe the physical and chemical properties of a model hydrophilic organic organized layer. To this end, H2O adsorption on mercaptoundecanoic acid self-assembled monolayers (SAMs) was investigated at the molecular level under ultra-high vacuum by high resolution electron energy loss spectroscopy (HREELS), through the sensitivity of the water OH stretching modes to the molecular environment. The water interfacial layer formation and structure were studied upon deposition at 28 K. A direct sensitive quantification in the submonolayer regime (10-80% of completion) was achieved by the sole measurement of the OH stretching mode frequencies, and the dominant basic (-COO(-))/acidic (-COOH) forms of the terminal functions could be probed. The surface densities of the water interfacial layer and the SAM terminal functions were measured independently, and demonstrated to be comparable. This means that the SAM terminal functions provided anchors for water adsorption through two hydrogen bonds and that the SAM acted as a template even at 28 K. Upon annealing at 110 K, the water molecules were observed to form clusters of higher molecular density, dewetting the supporting substrate. Finally, the vanishing of the supporting substrate vibrational signature, due to the masking effect by the deposited water layer, was used to estimate the depth probed by HREELS through water layers to be 11 +/- 2 A.
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Husseen, A., Le Moal, S., Oughaddou, H., Dujardin, G., Mayne, A., & Le Moal, E. (2017). Reaction kinetics of ultrathin NaCl films on Ag(001) upon electron irradiation. Phys. Rev. B, 96(23), 235418.
Résumé: We report on an electron-induced modification of alkali halides in the ultrathin film regime. The reaction kinetics and products of the modifications are investigated in the case of NaCl films grown on Ag(001). Their structural and chemical modification upon irradiationwith electrons of energy 52–60 eV and 3 keV is studied using low-energy electron diffraction (LEED) and Auger electron spectroscopy (AES), respectively. The irradiation effects on the film geometry and thickness (ranging from between two and five atomic layers) are examined using scanning tunneling microscopy (STM).We observe that Cl depletion follows different reaction kinetics, as compared to previous studies on NaCl thick films and bulk crystals. Na atoms produced from NaCl dissociation diffuse to bare areas of the Ag(001) surface, where they form Na-Ag superstructures that are known for the Na/Ag(001) system. The modification of the film is shown to proceed through two processes, which are interpreted as a fast disordering of the film with removal of NaCl from the island edges and a slow decrease of the structural order in the NaCl with formation of holes due to Cl depletion. The kinetics of the Na-Ag superstructure growth is explained by the limited diffusion on the irradiated surface, due to aggregation of disordered NaCl molecules at the substrate step edges.
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Jia, J., Esaulov, V. A., & Bendounan, A. (2017). Adsorption and desorption kinetics of NTCDA molecules on Ag(111) and Au(111) surfaces studied by ion scattering. Radiation Effects and Defects in Solids, 172(1-2), 39–47.
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Jiang, T., Malone, W., Tong, Y., Dragoe, D., Bendounan, A., Kara, A., & Esaulov, V. A. (2017). Thiophene Derivatives on Gold and Molecular Dissociation Processes. J. Phys. Chem. C, 121(50), 27923–27935.
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Kalashnyk N., R. L. A., Li D., Smogunov, Dappe Y.J., Jones T.S. and Guillemot L. (2017). Unraveling Giant Cu(110) Surface Restructuring Induced by a Non-Planar Phthalocyanine. NanoResearch, , 1–7.
Résumé: The surface stability of coinage metals is paramount when they are used as electrode materials for functional electronic devices incorporating organic semiconductors. In this work, it is shown that the adsorption of non-planar vanadyl phthalocyanine molecules on Cu(110) drastically restructured the metal surface at room temperature, which was further enhanced upon moderate annealing. Scanning tunneling microscopy imaging demonstrated that the surface was restructured at step edges into sawtooth features that gradually replaced the (110) terraces. The edges of the modified steps were preferentially composed of chiral (1×6) kink sites decorated with vanadyl phthalocyanine molecules adsorbed in a tilted configuration with the oxygen atom pointing downwards. These results can have a strong impact on the optimization of the performance of organic devices integrated with phthalocyanine molecules.
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Quertite, K., Lasri, K., Enriquez, H., Mayne, A. J., Bendounan, A., Dujardin, G., Trcera, N., Malone, W., EL Kenz, A., Benyoussef, A., Kara, A., & Oughaddou, H. (2017). Atomic structure of sub-monolayer NaCl grown on Ag(110) surface. JOURNAL OF PHYSICAL CHEMISTRY C, 121, 20272–20278.
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Quertite, K., Zaari, H., Ez-Zahraouy, H., El Kenz, A., Oughaddou, H., & Benyoussef, A. (2017). Theoretical investigation of electronic, magnetic, transport and optical properties of the pure and doped cuprate superconductor HgBa 2 CuO 4+δ. CURRENT APPLIED PHYSICS, 17(10), 1271–1278.
Résumé: We report detailed DFT calculations and Monte Carlo simulations on the pure and doped cuprate superconductor HgBa2CuO4+δ. For the pure compound (δ = 0), we have obtained an insulating behavior with strong antiferromagnetic copper spin correlations in the CuO2 plane. The high value of the calculated Néel temperature TN = 333 K reflects the large in-plane exchange interaction J = -145 meV. The obtained optical properties and critical exponents demonstrate the anisotropic quasi-2D character of this type of materials. As for the doped compound the electronic structure and the transport properties have been investigated for various values of doping. Based on these data, we suggest a prediction of the value of optimum doping for HgBa2CuO4+δ (δoptimal = 0.125).
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Roncin P., & Debiossac M. (2017). Elastic and inelastic diffraction of fast atoms, Debye-Waller factor, and Mössbauer-Lamb-Dicke regime. Phys. Rev. B., 96, 035415.
Résumé: The diffraction of fast atoms at crystal surfaces is ideal for a detailed investigation of the surface electronic
density. However, instead of sharp diffraction spots, most experiments show elongated streaks characteristic
of inelastic diffraction. This paper describes these inelastic profiles in terms of individual inelastic collisions
with surface atoms taking place along the projectile trajectory and leading to vibrational excitation of the local
Debye oscillator. A quasielastic regime where only one inelastic event contributes is identified as well as a
mixed quantum-classical regime where several inelastic collisions are involved. These regimes describe a smooth
evolution of the scattering profiles from sharp spots to elongated streaks merging progressively into the classical
diffusion regime.
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Sadeddine, S., Enriquez, H., Bendounan, A., Das, P. K., Vobornik, I., Mayne, A. J., Dujardin, G., Sirotti, F., & Kara A. & Oughaddou H. (2017). Compelling experimental evidence of a Dirac cone in the electronic structure of a 2D Silicon layer. SCIENTIFIC REPORTS, 7, 44400.
Résumé: The remarkable properties of graphene stem from its two-dimensional (2D) structure, with a linear dispersion of the electronic states at the corners of the Brillouin zone (BZ) forming a Dirac cone. Since then, other 2D materials have been suggested based on boron, silicon, germanium, phosphorus, tin, and metal di-chalcogenides. Here, we present an experimental investigation of a single silicon layer on Au(111) using low energy electron diffraction (LEED), high resolution angle-resolved photoemission spectroscopy (HR-ARPES), and scanning tunneling microscopy (STM). The HR-ARPES data show compelling evidence that the silicon based 2D overlayer is responsible for the observed linear dispersed feature in the valence band, with a Fermi velocity of vF = 10+6 m.s−1 comparable to that of graphene. The STM images show extended and homogeneous domains, offering a viable route to the fabrication of silicene-based opto-electronic devices.
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