Peer-reviewed Publications |
Canario, A. R., Guillemot, L., Grizzi, O., Bandurin, Y., & Esaulov, V. A. (2009). Scattering of F atoms and anions on a TiO2(110) surface. SURFACE SCIENCE, 603(8), 1099–1105.
Résumé: Results of a study of energy losses and electron transfer processes for grazing scattering of fluorine atoms and anions scattering along different azimuthal orientations of the TiO2 crystal are presented. We observe strong variations in the overall intensity of scattered particles which are due to channelling effects. The energy losses do not show strong variations as a function of crystal azimuth except for the case of scattering along the (001) direction between the bridging oxygen atom rows, where we also observe differences in the energy losses of scattered ions and neutrals. We attribute this to the fact that larger F- survival occurs for trajectories staying farther from the surface, when also the energy losses remain small. The overall characteristics of energy losses are attributed mainly to trajectory effects due to scattering in regions of different electron density. Measurements of the ratio of scattered ions to the total scattered flux, i.e. the ion fractions which reflect electron capture and loss processes, show that these are not the same for incident anions and atoms. A strong difference for scattering along the (001) direction is observed, where at low incident energies a strong survival of incident ions occurs. These results are tentatively discussed in terms of non resonant electron capture at lattice O- sites and electron loss into the conduction band or by collisional detachment with bridging O atoms. (C) 2009 Elsevier B.V. All rights reserved.
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Fillion, J. H., Amiaud, L., Congiu, E., Dulieu, F., Momeni, A., & Lemaire, J. L. (2009). D-2 desorption kinetics on amorphous solid water: from compact to porous ice films. Phys. Chem. Chem. Phys., 11(21), 4396–4402.
Résumé: The desorption kinetics of D-2 from amorphous solid water (ASW) films have been studied by the temperature-programmed desorption (TPD) technique in the 10-30 K temperature range. Compact (and nonporous) films were grown at 120 K over a copper substrate. Ultra-thin porous films were additionally grown at 10 K over the compact base. The TPD spectra from compact and from up to 20 monolayers (ML) porous films were compared. The simulation of the TPD experimental traces provides the corresponding D-2 binding-energy distributions. As compared to the compact case, the binding-energy distribution found for the 10 ML porous film clearly extends to higher energies. To study the transition from compact to porous ice, porous films of intermediate thicknesses (<10 ML), including ultra-thin films (<1 ML), were grown over the compact substrate. The thermal D-2 desorption peak was found to shift to higher temperatures as the porous ice network was progressively formed. This behavior can be explained by the formation of more energetic binding sites related to porous films. TPD spectra were also modelled by using a combination of the two energy distributions, one associated to a bare compact ice and the other associated to a 10 ML porous ice film. This analysis reveals a very fast evolution of the binding-energy distribution towards that of porous ice. Our results show that few ML of additional porous film are sufficient to produce a sample for which the D-2 adsorption can be described by the energy distribution found for the 10 ML porous film. These experiments then provide evidence that the binding energy of D-2 on ASW ice is primarily governed by the topological and morphological disorder of the surface at molecular scale.
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Flores, M., O'Rourke, B. E., Yamazaki, Y., & Esaulov, V. A. (2009). Potential and kinetic sputtering of alkanethiol self-assembled monolayers by impact of highly charged ions. PHYSICAL REVIEW A, 79(2).
Résumé: Highly charged ions have been used to study the sputtering of positive molecular fragments from mercaptoundecanoic acid and dodecanethiol self-assembled monolayers on gold surfaces. The samples were bombarded with Arq+ (4 <= q <= 10) ions with kinetic energies from 2 to 18 keV. The main fragments detected were H+, CnH2n+, and Cn+1O2H2n+1+ from mercaptoundecanoic and H+, CnH2n+, and Cn+1H2n+3+ from dodecanethiol. The proton yields were increased with larger charge state q of the highly charged ion (HCI) in both samples, scaling as q(gamma), with gamma similar to 5. The charge state dependence is discussed in terms of electron transfer to the HCI. The final yield of protons depends on molecular functional group characteristics, orientation on the surface, and reneutralization phenomena.
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Guillemot, L., & Bobrov, K. (2009). Chirality induced by surface strain studied using scanning tunneling microscopy. PHYSICAL REVIEW B, 79(20), 201406.
Résumé: We present a scanning tunneling microscopy study of a thermally annealed oxygen covered Cu(110)-(2x1)-O surface. The thermal annealing results in step bunching followed by formation of strained terraces. The mechanical strain causes local compression of the Cu lattice accompanied with reflection symmetry breaking as measured by comparative analysis of the atomically resolved topographies. On the strained terraces the oblique Cu lattice favors oxygen rearrangement into a chiral adsorption phase. Chiral surface organization is evidenced by formation of enantiomorphic domains on the strained terraces.
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Khemliche, H., Rousseau, P., Roncin, P., Etgens, V. H., & Finocchi, F. (2009). Grazing incidence fast atom diffraction: An innovative approach to surface structure analysis. Appl. Phys. Lett., 95(15), 151901.
Résumé: An alternative diffraction technique, based on grazing incidence scattering of high energy atoms, is applied to surface structure determination of crystalline surfaces. This technique, named GIFAD for grazing incidence fast atom diffraction, uses the same geometry as reflection high energy electron diffraction but is less invasive, more surface sensitive, and readily interpretable quantitatively. We present here a demonstration of this approach on a prototypical II-VI compound, ZnSe(001). Besides providing lattice parameter with high accuracy, we show that GIFAD gives straightforward access to the surface valence electron density profile, allowing clear identification of an electron transfer from Zn to Se. (C) 2009 American Institute of Physics. [doi:10.1063/1.3246162]
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Lafosse, A., Bertin, M., & Azria, R. (2009). Electron driven processes in ices: Surface functionalization and synthesis reactions. PROGRESS IN SURFACE SCIENCE, 84(5-6), 177–198.
Résumé: The ability to control and orientate chemical reactivity in the condensed phase is a major challenge of modern research. Upon interaction with condensed molecules electrons drive bond cleavage thus generating a population of very reactive species in the condensed medium. These reactive species may interact either within the volume leading to the synthesis of new molecules or with the substrate surface by forming strong chemical bonds. The former reaction is known as electron induced synthesis and the latter one as electron induced surface functionalization. High-energy electrons achieve only a low chemical specificity due to the large number of dissociating open channels. in contrast, electrons with energies below ionization threshold of the irradiated matter are capable of high selectivity because of the dissociative electron attachment mechanism. In this review recent studies of electron interaction with condensed molecules on hydrogenated diamond substrates will be described. In particular electron induced functionalization of diamond surfaces by CH(2)CN groups, decarboxylation reactions in condensed films of pure organic acids RCOOH (R = H, CH(3), C(2)H(5), CFA carbamic acid formation in CO(2):NH(3), HCOOH:NH(3) and CF(3)COOH:NH(3) binary ice mixtures, and glycine formation in a CH(3)COOD:NH(3) Mixture are presented and discussed. (c) 2009 Elsevier Ltd. All rights reserved.
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Lafosse, A., Bertin, M., Hoffman, A., & Azria, R. (2009). Surface functionalization by low-energy electron processing of molecular ices. SURFACE SCIENCE, 603(10-12), 1873–1877.
Résumé: Low-energy electron processing of condensed molecular films (also called ices) is an efficient method to induce functionalization of a substrate, and thereby to modify and adjust its electronic and chemical properties. This method takes advantage of a resonant mechanism specific to low-energy electrons (by opposition to photons), the dissociative electron attachment (DEA), the key process allowing the chemical selectivity to be directly and easily controlled by the kinetic energy of the processing electrons. The functionalization procedure is described and illustrated by high resolution electron energy loss spectroscopy (HREELS) results on the induced anchoring of CH(2)CN organic chains on synthetic diamond by electron irradiation at 2 eV of condensed acetonitrile. The range of application of the proposed functionalization method is worth to be extended to other organic/inorganic interfaces, such as organic layers on metallic and semiconducting substrates. (C) 2009 Elsevier B.V. All rights reserved.
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Millone, M. A. D., Hamoudi, H., Rodriguez, L., Rubert, A., Benitez, G. A., Vela, M. E., Salvarezza, R. C., Gayone, J. E., Sanchez, E. A., Grizzi, O., Dablemont, C., & Esaulov, V. A. (2009). Self-Assembly of Alkanedithiols on Au(111) from Solution: Effect of Chain Length and Self-Assembly Conditions. LANGMUIR, 25(22), 12945–12953.
Résumé: A comparative study on the adsorption of buthanedithiol (BDT). hexanedithiol (HDT), and nonanedithiol (NDT) oil Au(111) from ethanolic and n-hexane solutions and two different preparation procedures is presented. SAM characterization is based oil reflection-absorption infrared spectroscopy, electrochemistry, X-ray photoelectron spectroscopy, and time of flight direct recoil spectroscopy. Results indicate that one can obtain a standing-Up phase of dithiols and that the amount of the precursor lying-down phase decreases from BDT to NDT, irrespective of the solvent and self-assembly conditions. A good ordering of the hydrocarbon chains in the standing-up configuration is observed for HDT and NDT when the system is prepared in degassed n-hexane with all operations carried out in the dark. Disulfide bridges at the free SH terminal groups are formed for HDT and to a lesser extent for NDT prepared in ethanol in the presence of oxygen, but We found no evidence of ordered multilayer formation in our experiments. No disulfides were observed for BDT that only forms the lying-clown phase. Our results demonstrate the key role of the chain length and the procedure (solvent nature and oxygen presence) in controlling the surface structure and chemistry of SAMs dithiols on Au(111).
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Serkovic Loli, L. N., Hamoudi, H., Esteban Gayone, J., Luz Martiarena, M., Sanchez, E. A., Grizzi, O., Pasquali, L., Nannarone, S., Doyle, B. P., Dablemont, C., & Esaulov, V. A. (2009). Growth of N,N '-Bis(1-ethylpropyl)perylene-3,4,9,10-tetracarboxdiimide Films on Ag (111). JOURNAL OF PHYSICAL CHEMISTRY C, 113(41), 17866–17875.
Résumé: We have studied the self-assembly characteristics, the electronic structure, and the thermal stability of thin N,N'-bis(1-ethylpropyl)perylene-3,4,9,10-tetracarboxdiimide (EP-PTCDI) films grown on Ag (111) by a broad set of surface science analysis techniques. The deposition of single molecules to the formation of very thin films performed at room temperature under ultrahigh-vacuum (UHV) conditions was followed by atomic force microscopy (AFM), scanning tunneling microscopy (STM), ultraviolet photoemission spectroscopy (UPS), X-ray photoemission spectroscopy (XPS), and near edge X-ray absorption fine structure (NEXAFS), and was modeled by density functional theory (DFT) calculations. STM pictures show that substrate step edges are the starting point for molecule adsorption, which is followed by formation of islands and eventually a monolayer. The monolayer is composed of large domains with ordered molecules with their perylene-3,4,9,10-tetracarboxdiimide (PTCDI) core lying almost parallel to the surface. For further exposure, multilayer stacked domains are formed. For thicker films molecular order could not be established. Upon heating it is found that the multilayer is stable up to 150 degrees C where a rapid desorption takes place, followed by the dissociation of the molecules, leaving an ordered monolayer of presumably perylene core type molecules.
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Serkovic Loli, L. N., Sanchez, E. A., Gayone, E., Grizzi, O., & Esaulov, V. A. (2009). Assembly and thermal stability of thin EP-PTCDI films on Ag(111). PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 11(20), 3849–3853.
Résumé: We report a multi-technique study of the adsorption kinetics and self-assembly characteristics of EP-PTCDI grown on Ag(111) at UHV conditions and room temperature. Changes in the valence band characteristics for the mono and the multilayer film and the stability as a function of the annealing temperature are discussed. The results show that the molecules start to adsorb on the step edges forming ordered islands that grow to fully cover a monolayer. Further exposure results in the stacking of similarly ordered islands of several layers. The desorption experiment shows that the film is stable up to 150 degrees C where a rapid desorption of the multilayer takes place, followed by a decomposition of the molecules for temperatures higher than 170 degrees C.
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Actes de Conférences |
Bundaleski, N., Khemliche, H., Rousseau, P., Cassimi, A., Maunoury, L., & Roncin, P. (2009). Discharging dynamics of insulator surfaces irradiated by highly charged ions. In 14TH INTERNATIONAL CONFERENCE ON THE PHYSICS OF HIGHLY CHARGED IONS (HCI 2008) (Vol. 163, 012091).
Résumé: Guiding and focusing of keV to MeV ions by insulator micro-capillaries offer exciting perspectives for the production of low divergence micro-sized beams and the spatial control over the irradiated zone. These effects result from the local charging of the capillary inner wall and depend strongly on the charging/discharging dynamics of the insulating material. This dynamics has been studied on various glass insulator surfaces (borosilicate, fused silica and quartz) by grazing incidence highly charged ion beams. We propose simple experimental methods to derive the relevant time constant and study the influence of temperature and different material properties to the charging process.
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Cassimi, A., Maunoury, L., Muranaka, T., Huber, B., Dey, K. R., Lebius, H., Lelievre, D., Ramillon, J. M., Been, T., Ikeda, T., Kanai, Y., Kojima, T. M., Iwai, Y., Yamazaki, Y., Khemliche, H., Bundaleski, N., & Roncin, P. (2009). Imaging dynamics of charge-auto-organisation in glass capillaries. In NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS (Vol. 267, pp. 674–677).
Résumé: Multiply charged ion beam transmission through insulating capillaries is today a very active field of research. Thanks to the work of several groups during the last five years, several features of this unexpected process have been evidenced. The open challenge is to understand and control the self-organized charging-up of the capillary walls, which leads finally to the ion transmission. Up to now, the specific charge distribution on the inner surface, as well as the dynamics of the build-up, are still to be understood. While capillaries usually studied are microscopic pore networks etched in different materials, our concern is in macroscopic single capillaries made of glass. With a length of several centimeters and a diameter of a few micrometers at the exit, these capillaries have nevertheless the same aspect ratio as the etched pores (length/diameter approximate to 100). One of the leading goals of this research on single capillaries is to produce multi-charged ion beams with diameters smaller than a micrometer (nano-beams). These glass capillaries offer the opportunity to be used as an ion funnel due to their amazing proper-ties of guiding and focusing highly charged ion beams without altering neither their initial charge state nor the beam emittance (<10(-3) pi mm mrad). However, the understanding of the underlying process is not complete and relies on models assuming charge patches distributed along the capillary and which still need to be tested. We present the first observation imaging the dynamics of the charging-up process in single glass capillaries. During the build-up of the self-organized charge deposition on the capillary walls, the 230 keV Xe(23+) transmitted beam is deflected back and forth several times as the outgoing current increases. This is in agreement with the picture of charge patches created sequentially along the capillary and thus deflecting the beam until a stationary state is reached. (C) 2008 Elsevier B.V. All rights reserved.
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