Peer-reviewed Publications |
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Bobrov, K., & Guillemot, L. (2013). Autocatalytic effect of Cu nano-islands on the reaction of water with the oxygen covered Cu(110) surface. Surface Science, 611, 32–39.
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Canario, A. R., L. Guillemot, J. Diaz-Valdés, J.E. Valdés, P. Vargas, & V.A. Esaulov. (2013). Electron transfer and energy loss processes in fluorine scattering on oxygen covered Ag (110) – crystal azimuthal dependence. NIM B, 315, 36–41.
Résumé: Measurements of energy-losses and electron transfer processes in 1 to 4 keV fluorine ions and atoms scattering on clean and oxygen covered Ag(110) were studied. We report data for surface channeling conditions for different surface azimuths for the clean and oxygen covered O(2×1)–Ag(110) (2x1) reconstructed surface. Adsorption of oxygen results in strong changes in energy losses and a decrease in the negative ion fraction. Energy loss results are discussed in the light of calculations using non-linear models for stopping power, ab initio crystal structure calculations of the electronic density and semi-classical deterministic simulations.
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Canepa M., M. G., Chiara T., Cavalleri O., Prato M., Chaudhari V.R. and Esaulov V.A. (2013). Spectroscopic ellipsometry of Self assembled Monolayers: interface effects. The case of phenyl selenide SAMs on gold. PCCP, 15, 11559–11565.
Résumé: This work focuses on the quantitative application of spectroscopic ellipsometry to the study of optical properties and thickness of self assembled monolayers (SAMs) of phenyl selenide SAMs deposited from the liquid phase on gold. STM, XPS and cyclic voltammetry measurements provide additional chemical and morphological characterization of the SAMs. While routine ellipsometry analysis of SAMs often relies on the film-induced δΔ change of the Δ ellipsometric angle and discard SAM-substrate interface effects, the present data show a distinctive behaviour of the δΨ data that we assign to interface effects, stronger than those previously found for densely packed alkanethiols SAMs. An inaccurate modelling of the variations of Ψ related to the nano-structured SAM-substrate interface leads to a large overestimation of the film thickness. A simple model, accounting effectively for the interface layer between the film and the substrate and for the molecular optical absorptions, provides a good agreement with the data and a reliable thickness estimate of the SAM.
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Datta, D., Shen, J., & Esaulov, V. A. (2013). Hydrogen negative ion formation on a graphite HOPG surface. Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and , 315, 42–44.
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Houplin, J., Amiaud, L., Humblot, V., Martin, I., Matar, E., Azria, R., Pradier, C. M., & Lafosse, A. (2013). Selective terminal function modification of SAMs driven by low-energy electrons (0-15 eV). Phys. Chem. Chem. Phys., 15(19), 7220–7227.
Résumé: Low-energy electron induced degradation of a model self-assembled monolayer (SAM) of acid terminated alkanethiol was studied under ultra-high vacuum (UHV) conditions at room and low (similar to 40 K) temperatures. Low-energy electron induced chemical modifications of 11-mercaptoundecanoic acid (MUA, HS-(CH2)(10)-COOH) SAMs deposited on gold were probed in situ as a function of the irradiation energy (<11 eV) by combining two complementary techniques: High Resolution Electron Energy Loss Spectroscopy (HREELS), a surface sensitive vibrational spectroscopy technique, and Electron Stimulated Desorption (ESD) analysis of neutral fragments. The SAM's terminal functions were observed to be selectively damaged at around 1 eV by a resonant electron attachment mechanism, observed to decay by CO, CO2 and H2O formation and desorption. CO2 and H2O were also directly identified at low temperature by vibrational analysis of the irradiated SAMs. At higher irradiation energy, both terminal functions and spacer alkyl chains are damaged upon electron irradiation, by resonant and non-resonant processes.
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Jia, J., Bendounan, A., Harish M.N.K., Chaouchi, K., Sirotti, F., Sampath, S., & and Esaulov V.A. (2013). Selenium Adsorption on Au(111) and Ag(111) Surfaces: Adsorbed Selenium and Selenide Films. JPhys Chem C, 117(19), 9835–9842.
Résumé: Results of a high resolution photoemission and electrochemistry study of Se adsorption on Au(111) and Ag(111) surfaces performed by immersion of pristine samples into an aqeuous solution of Na2Se are presented. Cyclic voltammetry on Au shows formation of selenium adsorbed species and the structures observed in reductive desorption are related to the atomic and polymeric species observed in XPS. In the case of Au(111) XPS spectra in the Se(3d) region indeed show two main features attributed to Se chemisorbed atomically and polymeric Se8 features. Smaller structures due to other types of Se conformations were also observed. The Au(4f) peak line shape does not show core level shifts indicative of Au selenide formation. In the case of silver, XPS spectra for the Ag(3d) show a broadening of the peak and a deconvolution into AgB bulk like and AgSe components shows that the AgSe is located at a lower binding energy, an effect similar to oxidation and sulfidation of Ag. The Se(3d) XPS spectrum is found to be substantially different from the Au case and dominated by atomic type Se due to the selenide, though a smaller intensity Se structure at an energy similar to the Se8 structure for Au is also observed. Changes in the valence band region related to Se adsorption are reported.
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Jia, J., Mukherjee, S., Hamoudi, H., Nannarone, S., Pasquali, L., & Esaulov, V. A. (2013). Lying-Down to Standing-Up Transitions in Self Assembly of Butanedithiol Monolayers on Gold and Substitutional Assembly by Octanethiols. J. Phys. Chem. C, 117(9), 4625–4631.
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O’Rourke, B. E., Flores, M., Esaulov, V. A., & Yamazaki, Y. (2013). Modification of self assembled monolayers by highly charged ions. Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and , 299, 68–70.
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Rios Rubiano, C. A., Bocan, G. A., Gravielle, M. S., Bundaleski, N., Khemliche, H., & Roncin, P. (2013). Ab initio potential for the He-Ag(110) interaction investigated using grazing-incidence fast-atom diffraction. Phys. Rev. B, 87(1), 012903.
Résumé: Experimental diffraction patterns produced by grazing scattering of fast helium atoms from a Ag(110) surface are used as a sensitive tool to test an ab initio potential model derived from accurate density-functional theory (DFT) calculations. The scattering process is described by means of the surface eikonal approximation, which is a distorted-wave method that includes the quantum interference between contributions coming from different projectile paths, taking into account the complete corrugation of the three-dimensional projectile-surface potential. A fairly good agreement between the theoretical and experimental momentum distributions is found for incidence along different low-indexed crystallographic directions. This agreement is indicative of the quality of the DFT potential. The effective corrugation of the interaction potential across the incidence channel is also investigated. DOI: 10.1103/PhysRevA.87.012903
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Salazar Alarcón, L., Cristina, L. J., Shen, J., Jia, J., Esaulov, V. A., Sánchez, E. A., & Grizzi, O. (2013). Growth of 1,4-Benzenedimethanethiol Films on Au, Ag, and Cu: Effect of Surface Temperature on the Adsorption Kinetics and on the Single versus Multilayer Formation. J. Phys. Chem. C, 117(34), 17521–17530.
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Shen, J., Jia, J., Bobrov, K., Guillemot, L., & Esaulov, V. A. (2013). Electron transfer processes on Au nanoclusters supported on graphite. Gold Bull, 46(4), 343–347.
Résumé: Electron transfer processes play an important role in surface chemistry. This paper presents results of a study of changes in resonant electron transfer processes, as a function of gold cluster sizes, on the example of electron transfer between Li+ ions scattered on Au clusters on highly oriented pyrolytic graphite (HOPG). The gold nanoclusters were grown on lightly sputtered HOPG surface in order to obtain a wide coverage distribution of clusters. The growth of clusters was monitored by scanning tunneling microscopy. We found that electron transfer is much more probable on small clusters, whose lateral size is of the order of 2 to 3 nm and height in the 1-nm range, than on bulk Au or thin Au films. A comparison with Au clusters grown on the semiconducting titania did not reveal significant differences with HOPG.
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Zugarramurdi, A., Debiossac, M., Lunca-Popa, P., Alarcon, L. S., Momeni, A., Khemliche, H., Roncin, P., & Borisov, A. G. (2013). Surface-grating deflection of fast atom beams. Phys. Rev. A, 88(1), 0129074.
Résumé: For energetic atomic beams grazingly incident at the surface along the low index directions, fast motion parallel to the surface and slow motion perpendicular to the surface lead to the quantum diffraction pattern in the scattered beam. In this experimental and theoretical joint study we show that when the incident beam is misaligned with respect to an axial channel, the characteristic deformation of the diffraction pattern reflects an overall deflection of the scattered beam from the specular direction. The deflection is maximum for the azimuthal misalignment angles close to the rainbow angle and we show how this effect can be explained with the detailed balance principle relating diffraction of misaligned and perfectly aligned beams. We also demonstrate that using the detailed balance principle the diffraction charts for the incident beams aligned along the axial channel can be reconstructed from the azimuthal incidence angle dependence of the data obtained with misaligned beams.
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