Institut des Sciences Moléculaires d'Orsay - UMR 8214

Depuis 2008

2013-05-24T07:49:14Z

Publication	Records	Show
JOURNAL OF CHEMICAL PHYSICS	44
PHYSICAL REVIEW B	39
PHYSICAL CHEMISTRY CHEMICAL PHYSICS	31
JOURNAL OF PHYSICAL CHEMISTRY A	28
PHYSICAL REVIEW A	28
PHYSICAL REVIEW LETTERS	26
JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS	22
SURFACE SCIENCE	14
JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER	12
APPLIED PHYSICS LETTERS	9
CHEMICAL PHYSICS LETTERS	9
ASTRONOMY & ASTROPHYSICS	8
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY	8
X-RAY LASERS 2008	8
CHEMICAL PHYSICS	7
EUROPEAN PHYSICAL JOURNAL D	7
JOURNAL OF PHYSICAL CHEMISTRY C	7
NANO LETTERS	7
UVX 2008: 9E COLLOQUE SUR LES SOURCES COHERENTES ET INCOHERENTES UV	7
JOURNAL OF PHYSICAL CHEMISTRY B	6
JOURNAL OF PHYSICS-CONDENSED MATTER	6
LANGMUIR	6
NANOTECHNOLOGY	6
24TH SUMMER SCHOOL AND INTERNATIONAL SYMPOSIUM ON THE PHYSICS OF IONIZED GASES	5
X-RAY LASERS AND COHERENT X-RAY SOURCES: DEVELOPMENT AND APPLICATIONS IX	5
ACTUALITE CHIMIQUE	4
APPLIED AND ENVIRONMENTAL MICROBIOLOGY	4
ICARUS	4
NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS	4
COST CHEMISTRY CM0603-MELUSYN JOINT MEETING: DAMAGES INDUCED IN BIOMOLECULES BY LOW AND HIGH ENERGY RADIATIONS	3
INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY	3
JOURNAL OF MOLECULAR SPECTROSCOPY	3
LOW TEMPERATURE PHYSICS	3
MOLECULAR PHYSICS	3
NEW JOURNAL OF PHYSICS	3
PHOTOCHEMICAL & PHOTOBIOLOGICAL SCIENCES	3
PROGRESS IN SURFACE SCIENCE	3
REVIEW OF SCIENTIFIC INSTRUMENTS	3
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION	2
ANTIMICROBIAL AGENTS AND CHEMOTHERAPY	2
APPLIED PHYSICS A-MATERIALS SCIENCE & PROCESSING	2
APPLIED SURFACE SCIENCE	2
CLINICAL AND BIOMEDICAL SPECTROSCOPY AND IMAGING II	2
INTERNATIONAL JOURNAL OF MASS SPECTROMETRY	2
JOURNAL OF APPLIED PHYSICS	2
Journal of physics	2
NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT	2
OPTICS LETTERS	2
Physical Chemistry Chemical Physics : PCCP	2
SURFACE SCIENCE REPORTS	2
The Review of scientific instruments	2
THIN SOLID FILMS	2
WIRMS 2009: 5TH INTERNATIONAL WORKSHOP ON INFRARED MICROSCOPY AND SPECTROSCOPY WITH ACCELERATOR BASED SOURCES	2
XXVII ICPEAC Journal of Physics: Conference Series	2
14TH INTERNATIONAL CONFERENCE ON THE PHYSICS OF HIGHLY CHARGED IONS (HCI 2008)	1
1ST NANO-IBCT CONFERENCE 2011 – RADIATION DAMAGE OF BIOMOLECULAR SYSTEMS: NANOSCALE INSIGHTS INTO ION BEAM CANCER THERAPY	1
2010 23RD ANNUAL MEETING OF THE IEEE PHOTONICS SOCIETY	1
2011 CONFERENCE ON LASERS AND ELECTRO-OPTICS (CLEO)	1
26TH SUMMER SCHOOL AND INTERNATIONAL SYMPOSIUM ON THE PHYSICS OF IONIZED GASES (SPIG 2012)	1
35TH INTERNATIONAL CONFERENCE ON INFRARED	1
AIP Conf. Proc.	1
APPLIED MAGNETIC RESONANCE	1
APPLIED SPECTROSCOPY	1
ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES	1
BACTERIAL ADHESION: CHEMISTRY	1
Balkan Physics Letters	1
BIOMATERIALS	1
CANADIAN JOURNAL OF CHEMISTRY-REVUE CANADIENNE DE CHIMIE	1
CANADIAN JOURNAL OF PHYSICS	1
CELL DEATH & DISEASE	1
CHEMICAL SCIENCE	1
CHEMISTRY IN ASTROPHYSICAL MEDIA	1
CHEMPHYSCHEM	1
CHINESE JOURNAL OF CHEMICAL PHYSICS	1
Chiral Recognition in the Gas Phase	1
COMPUTATIONAL AND THEORETICAL CHEMISTRY	1
CRC Press Taylor & Francis Group	1
DAMAGE TO VUV	1
DIAMOND AND RELATED MATERIALS	1
ELECTRONICS LETTERS	1
EPL	1
EUROPEAN BIOPHYSICS JOURNAL WITH BIOPHYSICS LETTERS	1
EUROPEAN PHYSICAL JOURNAL B	1
EUROPEAN PHYSICAL JOURNAL-SPECIAL TOPICS	1
EUROPEAN UROLOGY SUPPLEMENTS	1
Fortschritte der Physik	1
IAU: ORGANIC MATTER IN SPACE	1
INTENSIVE CARE MEDICINE	1
INTERNATIONAL CONFERENCE ON MANY PARTICLE SPECTROSCOPY OF ATOMS	1
INTERNATIONAL REVIEWS IN PHYSICAL CHEMISTRY	1
INTERNATIONAL SYMPOSIUM ON (E	1
JOURNAL OF BIOPHOTONICS	1
JOURNAL OF CHEMICAL THEORY AND COMPUTATION	1
JOURNAL OF CLINICAL PATHOLOGY	1
JOURNAL OF ELECTRON SPECTROSCOPY AND RELATED PHENOMENA	1
JOURNAL OF LASER MICRO NANOENGINEERING	1
JOURNAL OF MATHEMATICAL PHYSICS	1
Journal of Molecular Modeling	1
JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY A-CHEMISTRY	1
JOURNAL OF PHYSICAL CHEMISTRY LETTERS	1
JOURNAL OF PHYSICS A-MATHEMATICAL AND THEORETICAL	1
JOURNAL OF PHYSICS D-APPLIED PHYSICS	1
JOURNAL OF RADIATION RESEARCH	1
JOURNAL OF SUPERCONDUCTIVITY AND NOVEL MAGNETISM	1
LIGHT AT EXTREME INTENSITIES: OPPORTUNITIES AND TECHNOLOGICAL ISSUES OF THE EXTREME LIGHT INFRASTRUCTURE	1
METEORITICS & PLANETARY SCIENCE	1
MUTATION RESEARCH-REVIEWS IN MUTATION RESEARCH	1
NATURE	1
NATURE COMMUNICATIONS	1
NATURE PHOTONICS	1
NEW JOURNAL OF CHEMISTRY	1
OPTICAL MATERIALS EXPRESS	1
OPTICS COMMUNICATIONS	1
OPTICS EXPRESS	1
PAHS AND THE UNIVERSE: A SYMPOSIUM TO CELEBRATE THE 25TH ANNIVERSARY OF THE PAH HYPOTHESIS	1
PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE	1
Physical and Chemical News	1
PHYSICS AND ASTROPHYSICS OF PLANETARY SYSTEMS	1
PloS one	1
POLISH JOURNAL OF CHEMISTRY	1

Publications

2013-05-22T12:45:16Z

2012
Bulard, E., Fontaine-Aupart, M. - P., Dubost, H., Zheng, W., Bellon-Fontaine, M. - N., Herry, J. - M., et al. (2012). Competition of Bovine Serum Albumin Adsorption and Bacterial Adhesion onto Surface-Grafted ODT: In Situ Study by Vibrational SFG and Fluorescence Confocal Microscopy. LANGMUIR, 28(49), 17001–17010. Résumé: The interaction of hydrophilic and hydrophobic ovococcoid bacteria and bovine serum albumin (BSA) proteins with a well ordered surface of octadecanethiol (ODT) self assembled monolayer (SAM) has been studied in different situations where proteins were either preadsorbed on ODT or adsorbed simultaneously with bacterial adhesion as in life conditions. The two situations lead to very different antimicrobial behavior. Bacterial adhesion on preadsorbed BSA is very limited, while the simultaneous exposure of ODT SAM to proteins and bacteria lead to a markedly weaker antimicrobial effect. The combination of sum frequency generation spectroscopy and fluorescence confocal microscopy experiments allow one to draw conclusions on the factors that govern the ODT SAM or BSA film interaction with bacteria at the molecular level. On the hydrophobic ODT surface, interaction with hydrophobic or hydrophilic biomolecules results in opposite effects on the SAM, namely, a flattening or a raise of the terminal methyl groups of ODT. On an amphiphilic BSA layer, the bacterial adhesion strength is weakened by the negative charges carried by both BSA and bacteria. Surprisingly, preadsorbed BSA that cover part of the bacteria cell walls increase the adhesion strength to the BSA film and reduce hydrophobic interactions with the ODT SAM. Finally, bacterial adhesion on a BSA film is shown to modify the BSA proteins in some way that change their interaction with the ODT SAM. The antimicrobial effect is much stronger in the case of a preadsorbed BSA layer than when BSA and bacteria are in competition to colonize the ODT SAM surface. Permanent link \| Stocker citation: RTF PDF LaTeX \| Exporter enregistrement: BibTeX Endnote ISI RIS Atom XML MODS XML ODF XML Word XML
Bulard, E., Fontaine-Aupart, M. - P., Dubost, H., Zheng, W., Herry, J. - M., Bellon-Fontaine, M. - N., et al. (2012). The Effect of Bacterial Adhesion on Grafted Chains Revealed by the Non-Invasive Sum Frequency Generation Spectroscopy. SPECTROSCOPY-AN INTERNATIONAL JOURNAL, 27(5-6), 571–579. Résumé: In biomedical and food industry, surface colonization by bacteria is harmful: it leads to biofilm formation, a microbial consortia more resistant to antibiotics than planktonic bacteria. In order to design materials able to limit the biofilm formation, the effect of bacteria on materials has to be well characterized. In this work, a well-defined surface composed of a self-assembled monolayer (SAM) of octadecanethiol (ODT) onto a gold surface is probed in situ. The SAM conformation is obtained using the femtosecond vibrational sum frequency generation (SFG) spectroscopy. This technique provides selectively the molecular vibrational signature of the interface. The behaviour of the ODT SAM is studied in different environments: in air, in water, and upon exposure to hydrophilic or hydrophobic Lactococcus lactis bacteria. Modelling the experimental SFG spectra reveals a measurable change of the SAM conformation which depends on the environment, especially on the hydrophilic-hydrophobic character. Permanent link \| Stocker citation: RTF PDF LaTeX \| Exporter enregistrement: BibTeX Endnote ISI RIS Atom XML MODS XML ODF XML Word XML
Fan, C., Poumellec, B., Zeng, H., Desmarchelier, R., Bourguignon, B., Chen, G., et al. (2012). Gold Nanoparticles Reshaped by Ultrafast Laser Irradiation Inside a Silica-Based Glass, Studied Through Optical Properties. JOURNAL OF PHYSICAL CHEMISTRY C, 116(4), 2647–2655. Résumé: Quasi-spherical or quasi-rod gold nanoparticles with an average diameter of 3.8 nm are randomly precipitated in a silica-based glass by a heat-treatment method. After ultrafast laser irradiation at 400 and 620 nm, optical absorption, birefringence, and dichroism measurements are performed to investigate the modification of gold nanoparticles shape. Theoretical simulations have been carried out to interpret the experimental results. We suggest that a small fraction of gold nanospheres are transformed mainly into nanodisks but also into nanorods oriented along the laser polarization for both fs laser wavelength. Absorption simulation suggests that they have an aspect ratio of 1.8 and 0.5, respectively, for fs laser irradiation at 400 nm. For 620 nm, the aspect ratio of the nanorods increases and the one of the nanodisks decreases. In such a way, we demonstrate that reshaping of gold nanoparticles, i.e. a property that was previously found for silver nanoparticles in multicomponent glass is also possible. By imaging the distribution of the birefringence according to the probe wavelength, we show that nanopartides are aligned into nanorods mainly out of irradiated volume and into nanopellets mainly in the irradiated volume. Permanent link \| Stocker citation: RTF PDF LaTeX \| Exporter enregistrement: BibTeX Endnote ISI RIS Atom XML MODS XML ODF XML Word XML
Lancry, M., Poumellec, B., Desmarchelier, R., & Bourguignon, B. (2012). Oriented creation of anisotropic defects by IR femtosecond laser scanning in silica. OPTICAL MATERIALS EXPRESS, 2(12), 1809–1821. Résumé: Irradiation of non-luminescent silica with polarized IR femtosecond laser light produced a significant amount of luminescent defects. We have investigated the properties of luminescence produced by the defects using UV-VUV excitation experiment depending on the relative orientation of the laser polarization and its scanning direction. Silicon Oxygen Deficient Center (SiODC) is identified. SiODC related luminescence is much stronger when the excitation polarization is parallel to the sample scanning direction and moved at low velocity, regardless of the writing polarization direction. This indicates that the creation of this anisotropic defect is oriented by the movement of the femtosecond laser beam. (C)2012 Optical Society of America Permanent link \| Stocker citation: RTF PDF LaTeX \| Exporter enregistrement: BibTeX Endnote ISI RIS Atom XML MODS XML ODF XML Word XML
2011
Bulard, E., Dubost, H., Fontaine-Aupart, M. - P., Zheng, W., Herry, J. - M., Bellon-Fontaine, M. - N., et al. (2011). Non invasive SFG spectroscopy: a tool to reveal the conformational change of grafted chains due to bacterial adhesion (Vol. 8087). Résumé: In many fields such as biomedical or food industry, surface colonization by micro-organisms leads to biofilms formation that are tridimentional biostructures highly resistant to the action of antimicrobials, by mechanisms still unclear. In order to deepen our understanding of the initial interaction of bacteria cells with a solid surface, we analyze by in situ vibrational Sum Frequency Generation (SFG) spectroscopy the effect of the adhesion of hydrophilic Lactoccocus lactis bacteria and its hydrophobic mutants in distilled water on a self-assembled monolayer (SAM) of octadecanethiol (ODT) on a gold film. When a homogeneous bacterial monolayer is deposited on this ordered surface, SFG spectrum of the ODT SAM shows significant intensity changes from that in air or in water. Its modelling as a function of conformation allows to distinguish optical effects due to the water solution surrounding bacteria from conformational changes of the ODT SAM due to the presence of the bacteria cells. Futhermore, bacterial adhesion induces different measurable effects on the ODT SAM conformation, depending on the hydrophobic / hydrophilic character of the bacterial surface. Such a result deserves to be taken into account for the design of new materials with improved properties or to control biofilm formation. Permanent link \| Stocker citation: RTF PDF LaTeX \| Exporter enregistrement: BibTeX Endnote ISI RIS Atom XML MODS XML ODF XML Word XML
Bulard, E., Guo, Z., Zheng, W., Dubost, H., Fontaine-Aupart, M. - P., Bellon-Fontaine, M. - N., et al. (2011). Non-Invasive Vibrational SFG Spectroscopy Reveals That Bacterial Adhesion Can Alter the Conformation of Grafted “Brush” Chains on SAM. LANGMUIR, 27(8), 4928–4935. Résumé: Understanding bacterial adhesion on a surface is a crucial step to design new materials with improved properties or to control biofilm formation and eradication. Sum Frequency Generation (SFG) vibrational spectroscopy has been employed to study in situ the conformational response of a self-assembled monolayer (SAM) of octadecanethiol (ODT) on a gold film to the adhesion of hydrophilic and hydrophobic ovococcoid model bacteria. The present work highlights vibrational SFG spectroscopy as a powerful and unique non-invasive biophysical technique to probe and control bacteria interaction with ordered surfaces. Indeed, the SFG vibrational spectral changes reveal different ODT SAM conformations in air and upon exposure to aqueous solution or bacterial adhesion. Furthermore, this effect depends on the bacterial cell surface properties. The SFG spectral modeling demonstrates that hydrophobic bacteria flatten the ODT SAM alkyl chain terminal part, whereas the hydrophilic ones raise this ODT SAM terminal part. Microorganism-induced alteration of grafted chains can thus affect the desired interfacial functionality, a result that should be considered for the design of new reactive materials. Permanent link \| Stocker citation: RTF PDF LaTeX \| Exporter enregistrement: BibTeX Endnote ISI RIS Atom XML MODS XML ODF XML Word XML
Fan, C., Poumellec, B., Zeng, H., Lancry, M., Yang, W., Bourguignon, B., et al. (2011). Directional Writing Dependence of Birefringence in Multicomponent Silica-based Glasses with Ultrashort Laser Irradiation. JOURNAL OF LASER MICRO NANOENGINEERING, 6(2), 158–163. Résumé: We reveal laser-induced high birefringence in multicomponent silica-based glass by means of ultrashort laser irradiation. It is attributed to the residual stress. A systematic study of birefringence variation is carried out according to laser parameters such as pulse energy, writing speed and direction, and laser polarization. Strong writing directional dependence is clearly observed when the writing direction is perpendicular to the laser polarization at the writing speeds of 20 μm/s – 120 μm/s, which was likely due to an asymmetry of the laser beam or an asymmetry of interaction mechanism. DOI: 10.2961/jlmn.2011.02.0011 Permanent link \| Stocker citation: RTF PDF LaTeX \| Exporter enregistrement: BibTeX Endnote ISI RIS Atom XML MODS XML ODF XML Word XML
Ouvrard, A., Niebauer, J., Ghalgaoui, A., Barth, C., Henry, C. R., & Bourguignon, B. (2011). Characterization of Thin MgO Films on Ag(001) by Low-Energy Electron Diffraction and Scanning Tunneling Microscopy. JOURNAL OF PHYSICAL CHEMISTRY C, 115(16), 8034–8041. Résumé: The evolution of the MgO(001) film morphology on Ag(001) was studied in dependence on the growth temperature (373-673 K) and grown MgO quantity (0.2-2 ML) by low-energy electron diffraction and scanning tunneling microscopy. We evidence an island growth mode of MgO for all temperatures. At 373 K, the MgO film exhibits a high island density, which is due to a too small surface mobility of the film compounds during the film growth. At a growth temperature of 673 K, silver hampers a perfect growth of MgO islands due to its high mobility, which leads to dendrites of MgO. The flattest and. largest MgO islands are obtained at a growth temperature of around 573 K, which is a compromise guaranteeing a sufficiently high Mg or MgO mobility but also an enough low diffusion of silver. Permanent link \| Stocker citation: RTF PDF LaTeX \| Exporter enregistrement: BibTeX Endnote ISI RIS Atom XML MODS XML ODF XML Word XML
2009
Bourguignon, B., Zheng, W., Carrez, S., Ouvrard, A., Fournier, F., & Dubost, H. (2009). Deriving the complete molecular conformation of self-assembled alkanethiol molecules from sum-frequency generation vibrational spectra. PHYSICAL REVIEW B, 79(12). Résumé: The sum frequency generation (SFG) spectrum of CH(2) and CH(3) modes in the self-assembled monolayer of octadecanethiol is modeled in order to understand the reasons of the very low SFG intensity of CH(2) modes and to investigate quantitatively the two types of L-shaped conformations qualitatively suggested in the literature. CH(2) modes are assumed local in order to calculate easily the spectrum of any conformation, and ab initio molecular hyperpolarizabilities are used. It is found that the absence of CH(2) bands does not imply an all-trans conformation and vice versa. Several conformations are compatible with SFG, but only one of them can be arranged on Au(111) and completely agrees with x-ray diffraction. All conformational details of the L-shape molecules are obtained. Permanent link \| Stocker citation: RTF PDF LaTeX \| Exporter enregistrement: BibTeX Endnote ISI RIS Atom XML MODS XML ODF XML Word XML
2008
Guo, Z., Zheng, W., Hamoudi, H., Dablemont, C., Esaulov, V. A., & Bourguignon, B. (2008). On the chain length dependence of CH3 vibrational mode relative intensities in sum frequency generation spectra of self assembled alkanethiols. SURFACE SCIENCE, 602(23), 3551–3559. Résumé: A global modelling of Sum Frequency Generation (SFG) spectra of the self assembly of alkanethiols is presented. All CH modes are modelled together. CH2 modes are assumed local to allow easy calculation of the spectrum as a function of molecular conformation. Ab initio molecular hyperpolarizabilities are used. A phenomenological approach is used to include the Fermi resonance in the model: the calculated intensity of the CH3 symmetric stretch is redistributed according to intensity borrowing by the Fermi resonance. The model is applied to octadecanethiol (ODT) and pentadecanethiol (PDT). The even/odd intensity alternation of SFG CH3 vibrational bands as a function of chainlength is used to test the model. It is found that the relative magnitudes of the hyperpolarizability tensors of the CH3 asymmetric and symmetric modes need to be adjusted. The model provides tilt and twist angles of the alkyl chain in agreement with the literature. It shows that the all trans conformation does not imply the absence of CH2 bands in SFG spectra. In addition, new information is obtained. In particular, if two types of molecular conformations are assumed, the C planes of the two molecules must be perpendicular to each other. (C) 2008 Elsevier B.V. All rights reserved. Permanent link \| Stocker citation: RTF PDF LaTeX \| Exporter enregistrement: BibTeX Endnote ISI RIS Atom XML MODS XML ODF XML Word XML
Hamoudi, H., Guo, Z., Prato, M., Dablemont, C., Zheng, W. Q., Bourguignon, B., et al. (2008). On the self assembly of short chain alkanedithiols. PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 10(45), 6836–6841. Résumé: A study of the self-assembly of nonane-alkanedithiol monolayers on gold in n-hexane and ethanol solvents is presented. Self-assembled monolayers (SAMs) are characterised by reflection-absorption infrared spectroscopy (RAIRS), sum frequency generation (SFG) and spectroscopic ellipsometry (SE) measurements. Data obtained for alkanethiols SAMs are also shown for comparison. The measurements show that nicely organized HSC(9)SH SAMs can be obtained in n-hexane provided that N(2)-degassed solutions are used and all preparation steps are performed in the absence of ambient light. SFG measurements show that these SAMs have free standing SH groups. Use of an un-degassed and/or light-exposed n-hexane solutions leads to a worse layer organization. Preparation in ethanol, even in degassed solutions with processing in the dark, leads to poorly organized layers and no sign of free-SH groups was observed. Permanent link \| Stocker citation: RTF PDF LaTeX \| Exporter enregistrement: BibTeX Endnote ISI RIS Atom XML MODS XML ODF XML Word XML

36. Séminaire de Karine Steenkeste (18 juin 2013)

2013-05-22T11:27:53Z

De l'exploration des biofilms bactériens à celle de la matière molle par imagerie de fluorescence multimodale

Au cours de la dernière décennie, l'émergence de techniques de microscopie de fluorescence innovantes combinées à des nanosondes fluorescentes originales a radicalement transformé la recherche en microbiologie permettant ainsi d'étudier de manière non invasive les mécanismes de formation et de réactivité de différents biosystèmes (bactéries, biofilms ...) à l'échelle moléculaire avec une résolution nanoseconde. Notre groupe s'est plus particulièrement attaché à la compréhension des processus de diffusion/réaction d'entités d'intérêt biologique dans les biofilms par des méthodes d'imagerie de fluorescence dynamiques, incluant notamment la spectroscopie de corrélation de fluorescence (FCS) et le retour de la fluorescence après photoblanchiment (FRAP). Ceci a permis de contribuer à une meilleure connaissance des biofilms et notamment de leur tolérance aux agents antimicrobiens.

Sur la base de cette expérience, nous avons étendu nos études vers de nouvelles applications dans le domaine de la biologie végétale pour une meilleure compréhension de la construction d'une paroi végétale. En effet, les propriétés de cette paroi, principalement composée de protéines englobées dans une matrice de pectines, évoluent selon l'état physiologique des cellules grâce à la présence d'enzymes qui remodèlent les polysaccharides. Comprendre l'activité et le mode d'action de ces enzymes permettrait de les utiliser pour contrôler les propriétés des pectines, et pouvoir ainsi modifier la paroi végétale in vivo. Dans cette perspective, des études ont été entreprises sur l'impact de la structure d'un système pectique modèle sur l'activité d'enzymes pectines méthylestérases et sur leur capacité à accéder à leur substrat, notamment via l'étude de leur diffusion.

39. Séminaire d'Alexandre Giuliani (28 mai 2013)

2013-05-22T09:19:42Z

Spectroscopie d'action électronique d'ions isolés en phase gazeuse par absorption du rayonnement synchrotron

La spectroscopie électronique d'action d'espèces formées par electronébulisation (ESI) est actuellement en plein développement. En effet, l'ESI permet de placer en phase gazeuse des espèces moléculaires qui résistent aux autres méthodes de vaporisation. Néanmoins, ce type d'expérience n'est pas trivial car il implique de confiner des densités d'ions suffisamment grandes en interaction avec de hauts flux de photons. Les montages expérimentaux utilisent généralement des lasers, mais la plage de longueur d'onde accessible reste limitée. Le rayonnement synchrotron possède des propriétés de brillance et d'accordabilité en longueur d'onde intéressantes et qui sont utilisées depuis les années 80 en spectroscopie ionique sur des cibles atomiques ou moléculaires de petite taille.

Dans le cas d'ions formés par ESI, la récente utilisation du rayonnement synchrotron apparaît prometteuse. Le couplage d'un piège ionique radiofréquence a été réalisé à SOLEIL en 2009. Les premiers résultats obtenus sur des polypeptides sous forme anionique et cationique seront présentés ainsi que les perspectives offertes par ce montage.

Publications

2013-05-21T07:58:13Z

2013
Hoendervanger, A. L., Clement, D., Aspect, A., Westbrook, C. I., Dowek, D., Picard, Y. J., et al. (2013). Influence of gold coating and interplate voltage on the performance of chevron micro-channel plates for temporally and spatially resolved single particle detection. The Review of scientific instruments, 84(2), 023307. Résumé: We present a study of two different sets of Micro-Channel Plates used for time and space resolved single particle detection. We investigate the effects of the gold coating and that of introducing an interplate voltage between the spatially separated plates. We find that the gold coating increases the count rate of the detector and the pulse amplitude as previously reported for non-spatially resolved setups. The interplate voltage also increases count rates. In addition, we find that a non-zero interplate voltage improves the spatial accuracy in determining the arrival position of incoming single particles (by ~20%) while the gold coating has a negative effect (by ~30%). Permanent link \| Stocker citation: RTF PDF LaTeX \| Exporter enregistrement: BibTeX Endnote ISI RIS Atom XML MODS XML ODF XML Word XML
2012
Billaud, P., Geleoc, M., Picard, Y. J., Veyrinas, K., Hergott, J. F., Poullain, S. M., et al. (2012). Molecular frame photoemission in dissociative ionization of H-2 and D-2 induced by high harmonic generation femtosecond XUV pulses. JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS, 45(19). Résumé: We report the first results of molecular frame photoelectron emission for dissociative photoionization (DPI) of H-2 and D-2 molecules induced by a spectrally filtered single high harmonic of a few femtosecond duration, using coincident electron-ion velocity vector correlation techniques. For the studied photon energies around 32 eV, where the resonant excitation of the Q(1) and Q(2) doubly excited states occurs, autoionization and nuclear dynamics are coupled on a few femtosecond timescale, giving rise to quantum interferences. Molecular frame photoelectron angular distributions (MFPADs), traced as a function of the kinetic energy release of the atomic fragments, provide the most sensitive observables for such complex dynamics. These results compare well with recent spectrally resolved experiments using synchrotron radiation which are also reported. As a novel XUV light source running at multi-kHz repetition rate and synchronized with laser pulses, high-order harmonic generation (HHG) opens new possibilities for extending these investigations to time-resolved studies at the femtosecond scale. Permanent link \| Stocker citation: RTF PDF LaTeX \| Exporter enregistrement: BibTeX Endnote ISI RIS Atom XML MODS XML ODF XML Word XML
Lebech, M., Houver, J. C., Raseev, G., dos Santos, A. S., Dowek, D., & Lucchese, R. R. (2012). Valence and inner-valence shell dissociative photoionization of CO in the 26-33 eV range. II. Molecular-frame and recoil-frame photoelectron angular distributions. JOURNAL OF CHEMICAL PHYSICS, 136(9). Résumé: Experimental and theoretical results for molecular-frame photoemission are presented for inner-valence shell photoionization of the CO molecule induced by linearly and circularly polarized light. The experimental recoil frame photoelectron angular distributions (RFPADs) obtained from dissociative photoionization measurements where the velocities of the ionic fragment and photoelectron were detected in coincidence, are compared to RFPADs computed using the multichannel Schwinger configuration interaction method. The formalism for including a finite lifetime of the predissociative ion state is presented for the case of general elliptically polarized light, to obtain the RFPAD rather than the molecular frame photoelectron angular distribution (MFPAD), which would be obtained with the assumption of instantaneous dissociation. We have considered photoionization of CO for the photon energies of 26.0 eV, 29.5 eV, and 32.5 eV. A comparison of experimental and theoretical RFPADs allows us to identify the ionic states detected in the experimental studies. In addition to previously identified states, we found evidence for the 2 (2)Delta state with an ionization potential of 25.3 eV and (2)Sigma(+) states with ionization potentials near 32.5 eV. A comparison of the experimental and theoretical RFPADs permits us to estimate predissociative lifetimes of 0.25-1 ps for some of the ion states. Consideration of the MFPADs of a series of (2)Pi ion states indicates the importance of inter-channel coupling at low photoelectron kinetic energy and the limitations of a single-channel analysis based on the corresponding Dyson orbitals. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.3681920] Permanent link \| Stocker citation: RTF PDF LaTeX \| Exporter enregistrement: BibTeX Endnote ISI RIS Atom XML MODS XML ODF XML Word XML
2011
Siu, W., Kelkensberg, F., Gademann, G., Rouzee, A., Johnsson, P., Dowek, D., et al. (2011). Attosecond control of dissociative ionization of O-2 molecules. PHYSICAL REVIEW A, 84(6). Résumé: We demonstrate that dissociative ionization of O-2 can be controlled by the relative delay between an attosecond pulse train (APT) and a copropagating infrared (IR) field. Our experiments reveal a dependence of both the branching ratios between a range of electronic states and the fragment angular distributions on the extreme ultraviolet (XUV) to IR time delay. The observations go beyond adiabatic propagation of dissociative wave packets on IR-induced quasistatic potential energy curves and are understood in terms of an IR-induced coupling between electronic states in the molecular ion. Permanent link \| Stocker citation: RTF PDF LaTeX \| Exporter enregistrement: BibTeX Endnote ISI RIS Atom XML MODS XML ODF XML Word XML
2010
Dowek, D., Perez-Torres, J. F., Picard, Y. J., Billaud, P., Elkharrat, C., Houver, J. C., et al. (2010). Circular Dichroism in Photoionization of H-2. PHYSICAL REVIEW LETTERS, 104(23). Résumé: Circular dichroism is a consequence of chirality. However, nonchiral molecules can also exhibit it when the measurement itself introduces chirality, e. g., when measuring molecular-frame photoelectron angular distributions. The few such experiments performed on homonuclear diatomic molecules show that, as expected, circular dichroism vanishes when the molecular-frame photoelectron angular distributions are integrated over the polar electron emission angle. Here we show that this is not the case in resonant dissociative ionization of H-2 for photons of 30-35 eV, which is the consequence of the delayed ionization from molecular doubly excited states into ionic states of different inversion symmetry. Permanent link \| Stocker citation: RTF PDF LaTeX \| Exporter enregistrement: BibTeX Endnote ISI RIS Atom XML MODS XML ODF XML Word XML
Elkharrat, C., Picard, Y. J., Billaud, P., Cornaggia, C., Garzella, D., Perdrix, M., et al. (2010). Ion Pair Formation in Multiphoton Excitation of NO2 Using Linearly and Circularly Polarized Femtosecond Light Pulses: Kinetic Energy Distribution and Fragment Recoil Anisotropy (vol 114A, pg 9902, 2010). JOURNAL OF PHYSICAL CHEMISTRY A, 114(50), 13288. Permanent link \| Stocker citation: RTF PDF LaTeX \| Exporter enregistrement: BibTeX Endnote ISI RIS Atom XML MODS XML ODF XML Word XML
2009
Dowek, D., Haouas, A., Guillemin, R., Elkharrat, C., Houver, J. - C., Li, W. B., et al. (2009). Recoil frame photoemission in inner-shell photoionization of small polyatomic molecules. EUROPEAN PHYSICAL JOURNAL-SPECIAL TOPICS, 169, 85–93. Résumé: Going from a diatomic to a polyatomic linear or non-linear molecule, the description of molecular frame photoemission in photoionization of molecules involves a function of increasing complexity. Using the electron-ion Vector Correlation method, which provides the emission velocity vectors of the emitted charged particles in a dissociative photoionization reaction, generally gives access to Recoil Frame Photoelectron Angular Distributions (RFPADs). We report results for site selected inner-shell photoionization of the N(2)O molecule induced by elliptically polarized light, where the primary ionization reaction leads to the production of several fragmentation channels. Ion fragment kinetic energy release distributions as well as RFPADs are reported for selected two ion-channels containing the complete parent molecule. Experimental results are compared with recent multi-channel Schwinger configuration interaction (MCSCI) ab initio calculations at the level of the RFPADs. The link with the original computed molecular frame photoelectron angular distributions (MFPADs) is discussed. Permanent link \| Stocker citation: RTF PDF LaTeX \| Exporter enregistrement: BibTeX Endnote ISI RIS Atom XML MODS XML ODF XML Word XML
Dowek, D., Picard, Y. J., Billaud, P., Elkharrat, C., & Houver, J. C. (2009). Molecular Frame Photoemission: Probe of the Photoionization Dynamics for Molecules in the Gas Phase. CHINESE JOURNAL OF CHEMICAL PHYSICS, 22(2), 178–186. Résumé: Molecular frame photoemission is a very sensitive probe of the photoionization (PI) dynamics of molecules. This paper reports a comparative study of non-resonant and resonant photoionization of D(2) induced by VUV circularly polarized synchrotron radiation at SOLEIL at the level of the molecular frame photoelectron angular distributions (MFPADs). We use the vector correlation method which combines imaging and time-of-flight resolved electron-ion coincidence techniques, and a generalized formalism for the expression of the I(chi, theta(e), phi(e)) MFPADs, where chi is the orientation of the molecular axis with respect to the light quantization axis and (theta(e), phi(e)) the electron emission direction in the molecular frame. Selected MFPADs for a molecule aligned parallel or perpendicular to linearly polarized light, or perpendicular to the propagation axis of circularly polarized light, are presented for dissociative photoionization (DPI) of D(2) at two photon excitation energies, hv=19 eV, where direct PI is the only channel opened, and hv=32.5 eV, i.e. in the region involving resonant excitation of Q(1) and Q(2) doubly excited state series. We discuss in particular the properties of the circular dichroism characterizing photoemission in the molecular frame for direct and resonant PI. In the latter case, a remarkable behavior is observed which may be attributed to the interference occurring between undistinguishable autoionization decay channels. Permanent link \| Stocker citation: RTF PDF LaTeX \| Exporter enregistrement: BibTeX Endnote ISI RIS Atom XML MODS XML ODF XML Word XML
Lebech, M., Houver, J. C., & Dowek, D. (2009). Valence and inner-valence shell dissociative photoionization of CO in the 26-33 eV range. I. Ion-electron kinetic energy correlation and laboratory frame photoemission. JOURNAL OF CHEMICAL PHYSICS, 130(19), 194307. Résumé: The (V(A+), V(e), e) vector correlation method, combining imaging and time-of-flight resolved electron-ion coincidence techniques, is used to probe dissociative photoionization (DPI) of CO induced by vacuum ultra violet linearly or circularly polarized synchrotron radiation in the 26-33 eV photon excitation energy range. It provides original information about both the photoionization dynamics of the CO molecule and the dissociation dynamics of the CO(+) molecular ions. The explored region corresponds to valence and inner-valence CO(+) ionic states, which involve doubly or multiply excited electronic configurations. In this paper I we identify up to 17 DPI reaction pathways by the position of the intermediate CO(+) molecular states in the Franck-Condon region and the (C(+) + O) or (O(+) + C) dissociation limits to which they correlate. For these processes we report the laboratory frame beta(C+/O+) and beta(e) asymmetry parameters as well as the relative branching ratios in selected binding energy bands. The I(chi,theta(e),phi(e)) molecular frame photoelectron angular distributions for selected PI processes will be reported in a companion paper II and compared with multichannel Schwinger configuration interaction ab initio calculations of these observables. Permanent link \| Stocker citation: RTF PDF LaTeX \| Exporter enregistrement: BibTeX Endnote ISI RIS Atom XML MODS XML ODF XML Word XML
2008
Elkharrat, C., Picard, Y. J., Billaud, P., Houver, J. C., & Dowek, D. (2008). Electron-ion vector correlations for the study of photoionization of molecules in the UVX range: From synchrotron radiation to short light pulses. Résumé: Molecular frame photoemission is a very sensitive probe of the photoionization (PI) dynamics of molecules. The electron-ion vector correlation (VC) method takes advantage of dissociative photoionization (DPI) reactions of small molecules to measure such observables. It relies on the coincident detection of the photoelectron and the ion fragment emitted from the same DPI event and the determination of their velocity vectors. Most of the VC studies so far have been performed using synchrotron radiation (SR) light sources which benefit from a high repetition rate (1-10 MHz) favorable for coincidence experiments. In this paper we discuss the extension of this method to the study of PI processes induced by ultra-short VUV light sources, which provide the capability for investigating processes characterized by femtosecond or subfemtosecond dynamics. We first illustrate the VC method by the report of recent results of a comparative study of resonant photoionization of the H(2) and D(2) molecules induced by VUV circularly polarized synchrotron radiation at SOLEIL in the region involving resonant excitation of Q(1) and Q(2) doubly excited state series. This problem is of particular interest since autoionization and dissociation of selected Q, or Q(2) states occur on a comparable time scale of few femtoseconds, which implies a coupling between the electronic and nuclear motion. The extension of the VC method using femtosecond laser sources is then demonstrated by results for multiphoton PI of the Xe atom induced by 70 fs pulses centered at 400 nm delivered by the SOFOCKLE and PLFA Sources (SLIC, CEA-Saclay) after frequency doubling of a 1 kHz Ti:sapphire laser. Permanent link \| Stocker citation: RTF PDF LaTeX \| Exporter enregistrement: BibTeX Endnote ISI RIS Atom XML MODS XML ODF XML Word XML
Elkharrat, C., Picard, Y. J., Billaud, P., Houver, J. C., & Dowek, D. (2008). Electron-ion vector correlations for the study of photoionization of molecules in the UVX range: From synchrotron radiation to short light pulses. Résumé: Molecular frame photoemission is a very sensitive probe of the photoionization (PI) dynamics of molecules. The electron-ion vector correlation (VC) method takes advantage of dissociative photoionization (DPI) reactions of small molecules to measure such observables. It relies on the coincident detection of the photoelectron and the ion fragment emitted from the same DPI event and the determination of their velocity vectors. Most of the VC studies so far have been performed using synchrotron radiation (SR) light sources which benefit from a high repetition rate (1-10 MHz) favorable for coincidence experiments. In this paper we discuss the extension of this method to the study of PI processes induced by ultra-short VUV light sources, which provide the capability for investigating processes characterized by femtosecond or subfemtosecond dynamics. We first illustrate the VC method by the report of recent results of a comparative study of resonant photoionization of the H(2) and D(2) molecules induced by VUV circularly polarized synchrotron radiation at SOLEIL in the region involving resonant excitation of Q(1) and Q(2) doubly excited state series. This problem is of particular interest since autoionization and dissociation of selected Q, or Q(2) states occur on a comparable time scale of few femtoseconds, which implies a coupling between the electronic and nuclear motion. The extension of the VC method using femtosecond laser sources is then demonstrated by results for multiphoton PI of the Xe atom induced by 70 fs pulses centered at 400 nm delivered by the SOFOCKLE and PLFA Sources (SLIC, CEA-Saclay) after frequency doubling of a 1 kHz Ti:sapphire laser. Permanent link \| Stocker citation: RTF PDF LaTeX \| Exporter enregistrement: BibTeX Endnote ISI RIS Atom XML MODS XML ODF XML Word XML
Journel, L., Guillemin, R., Haouas, A., Lablanquie, P., Penent, F., Palaudoux, J., et al. (2008). Resonant double Auger decay in carbon K-shell excitation of CO. PHYSICAL REVIEW A, 77(4). Résumé: We have studied double Auger decay after C 1s -> 2 pi(*) photoexcitation in gas phase carbon monoxide. Two distinct processes, namely direct double Auger decay and cascade double Auger decay, are identified and studied in detail using multiple coincidence techniques. Cascade Auger decay is shown to be the overall dominant process. Decay channels involving the dissociation of the molecule followed by autoionization of the oxygen fragments are observed. Permanent link \| Stocker citation: RTF PDF LaTeX \| Exporter enregistrement: BibTeX Endnote ISI RIS Atom XML MODS XML ODF XML Word XML

Publications

2013-05-17T12:26:27Z

2013
Ovramenko, T., Spillebout, F., Bocquet, F. C., Mayne, A. J., Dujardin, G., Sonnet, P., et al. (2013). STM imagery and density functional calculations of C-60 fullerene adsorption on the 6H-SiC(0001)-3x3 surface. PHYSICAL REVIEW B, 87(15), 155421. Résumé: Scanning tunneling microscopy (STM) studies of the fullerene C-60 molecule adsorbed on the silicon carbide SiC(0001)-3 x 3 surface, combined with density functional theory (DFT) calculations, show that chemisorption of individual C-60 molecules occurs through the formation of one bond to one silicon adatom only in contrast to multiple bond formation on other semiconducting surfaces. We observe three stable adsorption sites with respect to the Si adatoms of the surface unit cell. Comprehensive DFT calculations give different adsorption energies for the three most abundant sites showing that van der Waals forces between the C-60 molecule and the neighboring surface atoms need to be considered. The C-60 molecules are observed to form small clusters even at low coverage indicating the presence of a mobile molecular precursor state and nonnegligible intermolecular interactions. DOI: 10.1103/PhysRevB.87.155421 Permanent link \| Stocker citation: RTF PDF LaTeX \| Exporter enregistrement: BibTeX Endnote ISI RIS Atom XML MODS XML ODF XML Word XML
2012
Boudrioua, O., Yang, H., Sonnet, P., Stauffer, L., Mayne, A. J., Comtet, G., et al. (2012). Large organic molecule chemisorption on the SiC(0001) surface. PHYSICAL REVIEW B, 85(3), 035423. Résumé: We present a density-functional theory (DFT) study combined with scanning tunneling microscopy (STM) experiments of the chemisorption of the N,N'-bis(1-hexylheptyl) perylene-3,4:9,10-bis(dicarboximide) molecule, noted here as DHH-PTCDI, on the SiC(0001)-3 x 3 surface. Five possible adsorption configurations have been investigated in which molecular adsorption occurs on two adjacent Si adatoms via different pairs of atoms of the molecule. We have calculated the energies, structures, density of states, local density of states, and a calculated STM image and show that chemisorption via two oxygen atoms located on the same side of the molecule on two adjacent Si adatoms is the most favorable, in agreement with the experimental STM images. A comparison between the PTCDI and the adsorption of another large organic molecule (phthalocyanine) on the SiC(0001) surface completes this work. Permanent link \| Stocker citation: RTF PDF LaTeX \| Exporter enregistrement: BibTeX Endnote ISI RIS Atom XML MODS XML ODF XML Word XML
Westover, J., Enriquez, H., Oughaddou, H., & Kara, A. (2012). Metallization of the beta-SiC(100) 3x2 surface: A DFT investigation. SURFACE SCIENCE, 606(19-20), 1471–1474. Résumé: Using density functional theory (DFT) we report results for the electronic structure and vibrational dynamics of hydrogenated silicon carbide (001) (3 x 2) surfaces with various levels of hydrogenation. These results were obtained using density functional theory with a generalized gradient exchange correlation function. The calculations reveal that metallization can be achieved via hydrogen atoms occupying the second silicon layer. Further increase of hydrogen occupation on the second silicon layer sites results in a loss of this metallization. For the former scenario, where metallization occurs, we found a new vibrational mode at 1870 cm(-1), which is distinct from the mode associated with hydrogen atoms on the first layer. Furthermore, we found the diffusion barrier for a hydrogen atom to move from the second to the third silicon layer to be 258 meV. (c) 2012 Elsevier B.V. All rights reserved. Permanent link \| Stocker citation: RTF PDF LaTeX \| Exporter enregistrement: BibTeX Endnote ISI RIS Atom XML MODS XML ODF XML Word XML
Yang, H., Boudrioua, O., Mayne, A. J., Comtet, G., Dujardin, G., Kuk, Y., et al. (2012). The paradox of an insulating contact between a chemisorbed molecule and a wide band gap semiconductor surface. PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 14(5), 1700–1705. Résumé: Controlling the intrinsic optical and electronic properties of a single molecule adsorbed on a surface requires electronic decoupling of some molecular orbitals from the surface states. Scanning tunneling microscopy experiments and density functional theory calculations are used to study a perylene molecule derivative (DHH-PTCDI), adsorbed on the clean 3 x 3 reconstructed wide band gap silicon carbide surface (SiC(0001)-3 x 3). We find that the LUMO of the adsorbed molecule is invisible in I(V) spectra due to the absence of any surface or bulk states and that the HOMO has a very low saturation current in I(z) spectra. These results present a paradox that the molecular orbitals are electronically isolated from the surface of the wide band gap semiconductor even though strong chemical bonds are formed. Permanent link \| Stocker citation: RTF PDF LaTeX \| Exporter enregistrement: BibTeX Endnote ISI RIS Atom XML MODS XML ODF XML Word XML
2010
El Asri, T., Raissi, M., Vizzini, S., El Maachi, A., Ameziane, E. L., d'Avitaya, F. A., et al. (2010). Inter-diffusion of cobalt and silicon through an ultra thin aluminum oxide layer. APPLIED SURFACE SCIENCE, 256(9), 2731–2734. Résumé: Optical emission spectroscopy of sputtered species during ion bombardment, Auger electron spectroscopy and high-resolution transmission electron microscopy were used to study the cobalt and silicon diffusion through the interfaces of Co/AlO/Si(0 0 1) hetero-structure. The results are discussed as a function of the annealing temperature of sample and show that the diffusion process at the interfaces starts for annealing temperatures above 200 degrees C without detectable modification of the oxide layer. (C) 2009 Elsevier B. V. All rights reserved. Permanent link \| Stocker citation: RTF PDF LaTeX \| Exporter enregistrement: BibTeX Endnote ISI RIS Atom XML MODS XML ODF XML Word XML
2009
Baffou, G., Mayne, A. J., Comtet, G., Dujardin, G., Stauffer, L., & Sonnet, P. (2009). SiC(0001) 3 x 3 Heterochirality Revealed by Single-Molecule STM Imaging. JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 131(9), 3210–3215. Résumé: We report a description of the SiC(0001) 3 x 3 silicon carbide reconstruction based on single-molecule scanning tunneling microscopy (STM) observations and density functional theory calculations. We show that the SiC(0001) 3 x 3 reconstruction can be described as contiguous domains of right and left chirality distributed at the nanoscale, which breaks the to date supposed translational invariance of the surface. While this surface heterochirality remains invisible in STM topographies of clean surfaces, individual metal-free phthalocyanine molecules chemisorbed on the surface act as molecular lenses to reveal the surface chirality in the STM topographies. This original method exemplifies the ability of STM to probe atomic-scale structures in detail and provides a more complete vision of a frequently studied SiC reconstruction. Permanent link \| Stocker citation: RTF PDF LaTeX \| Exporter enregistrement: BibTeX Endnote ISI RIS Atom XML MODS XML ODF XML Word XML
Cranney, M., Chalopin, Y., Mayne, A. J., & Dujardin, G. (2009). Adsorption and organisation of para-hexaphenyl molecules on Si(100). APPLIED PHYSICS A-MATERIALS SCIENCE & PROCESSING, 94(4), 767–773. Résumé: Para-hexaphenyl molecules (p-6P: C(36)H(26)) can be grown as nanofibres on various surfaces having optical properties of technological relevance. We report here the first observations of the initial stages of adsorption of individual p-6P molecules on Si(100)-(2x1) using room temperature Scanning Tunnelling Microscopy (STM). Depending on the substrate temperature, the hexaphenyl molecules adsorb in two configurations; indicating both weak and strong chemisorption. All six phenyl rings are clearly visible and the molecules are found to adsorb with characteristic angles between the long axis of the molecule and the silicon dimer rows. A statistical analysis of the spatial distribution of the molecules suggests that the clustering required for crystallographic nanofibre growth does not occur at the atomic scale under the experimental conditions used here. Permanent link \| Stocker citation: RTF PDF LaTeX \| Exporter enregistrement: BibTeX Endnote ISI RIS Atom XML MODS XML ODF XML Word XML
Riedel, D., Delacour, C., Mayne, A. J., & Dujardin, G. (2009). Very low thermally induced tip expansion by vacuum ultraviolet irradiation in a scanning tunneling microscope junction. PHYSICAL REVIEW B, 80(15), 155451. Résumé: The thermal and photoelectronic processes induced when a vacuum ultraviolet (VUV) laser irradiates the junction of a scanning tunneling microscope (STM) are studied. This is performed by synchronizing the VUV laser shots with the STM scan signal. Compared to other wavelengths, the photoinduced thermal STM-tip expansion is not observed when the VUV radiation is freed from spurious emissions. Furthermore, we demonstrate that the purified VUV photoinduced transient signal detected in the tunnel current is entirely due to photoelectronic emission and not combined with thermionic processes. The ensuing photoelectron emission is shown to be independent of the tip-surface distance while varying linearly with the pure VUV laser intensity. These results illustrate a strong decoupling between phonons and photoelectrons which allows a very weak STM-tip expansion. Permanent link \| Stocker citation: RTF PDF LaTeX \| Exporter enregistrement: BibTeX Endnote ISI RIS Atom XML MODS XML ODF XML Word XML
Vizzini, S., Oughaddou, H., Hoarau, J. Y., Biberian, J. P., & Aufray, B. (2009). Y Growth of ultrathin film aluminum oxide on Ag(111). APPLIED PHYSICS LETTERS, 95(17), 173111. Résumé: Scanning tunneling microscopy (STM) and spectroscopy and electron energy loss spectroscopy were used to characterize ultrathin epitaxial aluminum oxide on Ag(111) which was prepared via a specific deposition and oxidation process. Atomically resolved STM images show self-organized oxide stripes of 4 nm width with excellent homogeneity in depth and chemical composition properties which are crucial for applications of this oxide to magnetic tunnel junctions. We also found that electrons tunnel easily through the oxide film. This oxide has a different spectroscopic signature from that of alumina and has a wide bandgap close to 6.6 eV. (C) 2009 American Institute of Physics. [doi:10.1063/1.3251778] Permanent link \| Stocker citation: RTF PDF LaTeX \| Exporter enregistrement: BibTeX Endnote ISI RIS Atom XML MODS XML ODF XML Word XML
2008
Baffou, G., Mayne, A. J., Comtet, G., & Dujardin, G. (2008). State selective electron transport through electronic surface states of 6H-SiC(0001)-3 x 3. PHYSICAL REVIEW B, 77(16), 165320. Résumé: We investigate charge transport through electronic surface states of the 6H-SiC(0001)-3 x 3 surface. Three intrinsic surface states are located within the wide bulk band gap, in which two (S(1) and U(1)) arise from strongly correlated electronic states and the third (S(2)) has negligible electron correlation effects. Combined conductance and luminescence experiments with the scanning tunneling microscope show that the Mott-Hubbard surface states (S(1) and U(1)) have a high resistance (1.0 G Omega), while the noncorrelated state (S(2)) has a negligible resistance. Consequently, current can be selectively transported through any of these three surface states. Permanent link \| Stocker citation: RTF PDF LaTeX \| Exporter enregistrement: BibTeX Endnote ISI RIS Atom XML MODS XML ODF XML Word XML
Mamatkulov, M., Stauffer, L., Sonnet, P., Mayne, A. J., Comtet, G., & Dujardin, G. (2008). Theoretical simulations of the tip-induced configuration changes of the 4,4 '-diacetyl-p-terphenyl molecule chemisorbed on Si(001). JOURNAL OF CHEMICAL PHYSICS, 128(24), 244710. Résumé: We have investigated from a theoretical point of view modifications of the 4,4'-diacetyl-p-terphenyl molecule chemisorbed on Si(001) induced by the scanning tunneling microscope (STM). In previous experiments, these modifications were observed to occur preferentially at the end of the molecule after a +4.0 V voltage pulse and at the center after a +4.5 V voltage pulse. In the framework of ab initio simulations, we have realized a systematic energetic study of the dissociative chemisorption of one, two, or three phenyl rings of the substituted p-terphenyl molecule. Charge densities were then calculated for the investigated configurations and compared to the STM topographies. Before manipulation with the STM tip, the substituted p-terphenyl molecule is preferentially adsorbed without phenyl ring dissociation, allowing a partial rotation of the central phenyl ring. Our results show that the STM induced modifications observed at the end of the molecule might originate from the dissociation of two phenyl rings (one central and one external ring), while the modifications occurring at the central part of the molecule can be interpreted as a dissociation of the two external rings. (c) 2008 American Institute of Physics. Permanent link \| Stocker citation: RTF PDF LaTeX \| Exporter enregistrement: BibTeX Endnote ISI RIS Atom XML MODS XML ODF XML Word XML

Publications

2013-05-17T12:23:18Z

2012
Raseev, G. (2012). Laser fields at flat interfaces: I. Vector potential. EUROPEAN PHYSICAL JOURNAL D, 66(7), 179. Résumé: A model calculating the laser fields at a flat structureless surface taking into account the surface photoelectric effect is presented. The photon is p or transverse magnetic linearly polarized, continuous and its wave length is long, i.e. lambda(vac) >= 12.4 nm. The sharp rise of the electron density at the interface generates an atomic scale spatial dependence of the laser field. In real space and in the temporal gauge, the vector potential A of the laser is obtained as a solution of the classical Ampere-Maxwell and the material equations. The susceptibility is a product of the electron density of the material system with the surface and of the bulk tensor and non-local isotropic (TNLI) polarizability. The electron density is obtained quantum mechanically by solving the Schrodinger equation. The bulk TNLI polarizability including dispersion is calculated from a Drude-Lindhard-Kliewer model. In one dimension perpendicular to the surface the components A(x)(z,omega) and A(z)(z,omega) of the vector potential are solutions of the Ampere-Maxwell system of two coupled integro-differential equations. The model, called vector potential from the electron density-coupled integro-differential equations (VPED-CIDE), is used here to obtain the electron escape probability from the power density absorption, the reflectance, the electron density induced by the laser and Feibelman's parameters d(parallel to) and d(perpendicular to). Some preliminary results on aluminium surfaces are given here and in a companion paper the photoelectron spectra are calculated with results in agreement with the experiment. Permanent link \| Stocker citation: RTF PDF LaTeX \| Exporter enregistrement: BibTeX Endnote ISI RIS Atom XML MODS XML ODF XML Word XML
Raseev, G. (2012). Laser fields at flat interfaces: II. Plasmon resonances in aluminium photoelectron spectra. EUROPEAN PHYSICAL JOURNAL D, 66(7), 180. Résumé: Using the model derived in paper I [G. Raseev, Eur. Phys. J. D 66, 167 (2012)], this work presents calculations of the photoelectron spectrum (PES) of low index aluminium surfaces in the 10-30 eV region. The laser is p or transverse magnetic linearly polarized incident on a flat structureless surface and its fields are modeled in I using the vector potential in the temporal gauge. This model uses a tensor and nonlocal isotropic (TNLI) susceptibility and solves the classical Ampere-Maxwell equation through the use of the vector potential from the electron density-coupled integro-differential equations (VPED-CIDE). The PE cross sections are the squares of the PE transition moments calculated using the VPED-CIDE vector potential function of the penetration coordinate. The PES is obtained in a one step model using either the Fermi golden rule or the Weisskopf-Wigner (WW) expressions. The WW cross section PES compares favorably with the experimental angle and energy resolved photoelectron yield (AERPY) spectrum of Levinson et al. [Phys. Rev. Lett. 43, 952 (1979)], Levinson and Plummer [Phys. Rev. B 24, 628 (1981)] for Al(001) and of Barman et al. [Phys. Rev. B 58, R4285 (1998)], Barman [Curr. Sci. 88, 54 (2005)] for Al(111) surfaces. As in the experiment, our theoretical AERPY displays the multipole surface plasmon resonance at 11.32/12.75 eV for Al(001)/Al(111), mainly due to the surface contribution vertical bar vertical bar(2), the bulk plasmon minimum at 15 eV and the two single particle excitation resonances at about 16 and 22 eV. The nature of the plasmon resonances of the PES is analyzed using the reflectance, the electron density induced by the laser and Feibelman's parameter d(perpendicular to) all introduced in paper I. Permanent link \| Stocker citation: RTF PDF LaTeX \| Exporter enregistrement: BibTeX Endnote ISI RIS Atom XML MODS XML ODF XML Word XML
2010
Raseev, G., & Bejan, D. (2010). Multipole surface plasmon resonance of an aluminium surface. OPTICS COMMUNICATIONS, 283(20), 3976–3984. Résumé: The surface photoelectric effect and the surface plasmon resonances appear when a p/transverse magnetic polarized laser hits a gas-solid interface. We model this effect in the long wave length (LWL) domain (lambda(vac)>10 nm, (h) over cap omega<124 eV) by combining the Ampere-Maxwell equation, written in classical approximation, with the material equation for the susceptibility. The resulting model, called the vector potential from the electron density (VPED), calculates the susceptibility as a product of the bulk susceptibility and the electron density of the actual system. The bulk susceptibility is a sum of the bound electron scalar susceptibility taken from the experiment and of the conduction electron non-local isotropic susceptibility tensor in a jellium metal (Lindhard, 1954 [1]). The electron density is the square of the wave function solution of the Schrodinger equation. The analysis of observables, the reflectance R and the photoelectron yield Y as well as the induced charge density permits to identify and characterize the multipole surface plasmon resonance of Al(111) appearing at omega(m) similar to 0.8 omega(p), or 11-12 eV. (c) 2010 Elsevier B.V. All rights reserved. Permanent link \| Stocker citation: RTF PDF LaTeX \| Exporter enregistrement: BibTeX Endnote ISI RIS Atom XML MODS XML ODF XML Word XML

Publications

2013-05-17T12:14:08Z

2012
Nimmrich, M., Kittelmann, M., Rahe, P., Harneit, W., Mayne, A. J., Dujardin, G., et al. (2012). Influence of charge transfer doping on the morphologies of C-60 islands on hydrogenated diamond C(100)-(2 x 1). PHYSICAL REVIEW B, 85(3), 035420. Résumé: The adsorption and island formation of C-60 fullerenes on the hydrogenated C(100)-(2 x 1):H diamond surface is studied using high-resolution noncontact atomic force microscopy in ultrahigh vacuum. At room temperature, C-60 fullerene molecules assemble into monolayer islands, exhibiting a hexagonally close-packed internal structure. Dewetting is observed when raising the substrate temperature above approximately 505 K, resulting in two-layer high islands. In contrast to the monolayer islands, these double-layer islands form extended wetting layers. This peculiar behavior is explained by an increased molecule-substrate binding energy in the case of double-layer islands, which originates from charge transfer doping. Only upon further increasing the substrate temperature to approximately 615 K, the wetting layer desorbs, corresponding to a binding energy of the charge transfer-stabilized film of 1.7 eV. Permanent link \| Stocker citation: RTF PDF LaTeX \| Exporter enregistrement: BibTeX Endnote ISI RIS Atom XML MODS XML ODF XML Word XML
2011
Rochdi, N., Liudvikouskaya, K., Descoins, M., Raissi, M., Coudreau, C., Lazzari, J. L., et al. (2011). Surface morphology and structure of ultra-thin magnesium oxide grown on (100) silicon by atomic layer deposition oxidation. THIN SOLID FILMS, 519(19), 6302–6306. Résumé: Ultra-thin magnesium oxide layers were elaborated by atomic layer deposition and oxidation process on silicon (100) starting from (2 x 1) thermally-reconstructed or hydrogen-terminated Si surfaces. Low-energy electron diffraction experiments show (2 x 3) and (3 x 3) reconstructions while depositing a magnesium monolayer on Si clean surfaces, and a 3-dimentional growth of the oxide as confirmed by ex-situ atomic force microscopy. For hydrogen-terminated or clean surfaces previously physisorbed by oxygen, uniform cobalt/magnesium-oxide/silicon stacks of layers are observed by transmission electron microscopy. Annealing above 150 degrees C leads to MgO dissolution and formation of an interfacial complex compound by inter-diffusion of Si and Co. (C) 2011 Elsevier B.V. All rights reserved. Permanent link \| Stocker citation: RTF PDF LaTeX \| Exporter enregistrement: BibTeX Endnote ISI RIS Atom XML MODS XML ODF XML Word XML
Wang, T., Boer-Duchemin, E., Tranvouez, E., Cartwright, R., Comtet, G., Dujardin, G., et al. (2011). Low voltage fabrication of sub-nanometer insulating layers on hydrogenated diamond. JOURNAL OF APPLIED PHYSICS, 110(3), 034311. Résumé: A new regime of electrochemical anodic oxidation with an atomic force microscope (AFM) is introduced for producing insulating layers on a hydrogenated diamond surface. In this new regime, when a low surface voltage (V(S) < +2 V) is applied to the sample, an insulating layer is created without any measurable change in the topography. Insulating layers created in this fashion are shown to preserve the high sub-surface conductance of hydrogenated diamond surfaces, contrary to the oxide layers accompanied by a topographic change, which destroy sub-surface conductance. (C) 2011 American Institute of Physics. [doi:10.1063/1.3615956] Permanent link \| Stocker citation: RTF PDF LaTeX \| Exporter enregistrement: BibTeX Endnote ISI RIS Atom XML MODS XML ODF XML Word XML
2010
Boer-Duchemin, E., Tranvouez, E., & Dujardin, G. (2010). The interaction of an atomic force microscope tip with a nano-object: a model for determining the lateral force. NANOTECHNOLOGY, 21(45), 455704. Résumé: A calculation of the lateral force interaction between an atomic force microscope (AFM) tip and a nano-object on a substrate is presented. In particular, the case where the AFM tip is used to manipulate the nano-object is considered; i.e., the tip is displaced across the nano-object with the feedback off. The Hamaker equations are used to calculate the force when the tip and sample are not in contact and the Johnson, Kendall and Roberts (JKR) or Derjaguin, Muller and Toporov (DMT) formalisms are used for the contact force. The effect of the material parameters, the choice of contact theory and the shape of the nano-object on the resulting lateral forces are explored. The calculation is applied to an experimental system consisting of a cadmium selenide nanorod on graphite. Permanent link \| Stocker citation: RTF PDF LaTeX \| Exporter enregistrement: BibTeX Endnote ISI RIS Atom XML MODS XML ODF XML Word XML
Nimmrich, M., Kittelmann, M., Rahe, P., Mayne, A. J., Dujardin, G., von Schmidsfeld, A., et al. (2010). Atomic-resolution imaging of clean and hydrogen-terminated C(100)-(2x1) diamond surfaces using noncontact AFM. PHYSICAL REVIEW B, 81(20), 201403. Résumé: High-purity, type IIa diamond is investigated by noncontact atomic force microscopy (NC-AFM). We present atomic-resolution images of both the electrically conducting hydrogen-terminated C(100)-(2 x 1) : H surface and the insulating C(100)-(2 x 1) surface. For the hydrogen-terminated surface, a nearly square unit cell is imaged. In contrast to previous scanning tunneling microscopy experiments, NC-AFM imaging allows both hydrogen atoms within the unit cell to be resolved individually, indicating a symmetric dimer alignment. Upon removing the surface hydrogen, the diamond sample becomes insulating. We present atomic-resolution images, revealing individual C-C dimers. Our results provide real-space experimental evidence for a (2 x 1) dimer reconstruction of the truly insulating C(100) surface. Permanent link \| Stocker citation: RTF PDF LaTeX \| Exporter enregistrement: BibTeX Endnote ISI RIS Atom XML MODS XML ODF XML Word XML
2009
Tranvouez, E., Boer-Duchemin, E., Mayne, A. J., Vanderbruggen, T., Scheele, M., Cartwright, R., et al. (2009). Influence of morphology on the conductance of single-crystal diamond surfaces measured by atomic force microscopy. JOURNAL OF APPLIED PHYSICS, 106(5), 054301. Résumé: A detailed atomic force microscopy (AFM) study of the conductance of hydrogenated single-crystal diamond (100) surfaces over submicron length scales is presented. The hydrogenation process was found to influence the surface morphology by reducing surface roughness, with the subsequent appearance of small triangular structures (with side lengths of 200 nm). Conducting AFM measurements revealed variations in the current and resistance that were related to the topography. Possible explanations include surface inhomogeneity of the electronic structure or variations in the contact resistance due to the surface roughness. Permanent link \| Stocker citation: RTF PDF LaTeX \| Exporter enregistrement: BibTeX Endnote ISI RIS Atom XML MODS XML ODF XML Word XML
Tranvouez, E., Orieux, A., Boer-Duchemin, E., Devillers, C. H., Huc, V., Comtet, G., et al. (2009). Manipulation of cadmium selenide nanorods with an atomic force microscope. NANOTECHNOLOGY, 20(16), 165304. Résumé: We have used an atomic force microscope (AFM) to manipulate and study ligand-capped cadmium selenide nanorods deposited on highly oriented pyrolitic graphite (HOPG). The AFM tip was used to manipulate (i.e., translate and rotate) the nanorods by applying a force perpendicular to the nanorod axis. The manipulation result was shown to depend on the point of impact of the AFM tip with the nanorod and whether the nanorod had been manipulated previously. Forces applied parallel to the nanorod axis, however, did not give rise to manipulation. These results are interpreted by considering the atomic-scale interactions of the HOPG substrate with the organic ligands surrounding the nanorods. The vertical deflection of the cantilever was recorded during manipulation and was combined with a model in order to estimate the value of the horizontal force between the tip and nanorod during manipulation. This horizontal force is estimated to be on the order of a few tens of nN. Permanent link \| Stocker citation: RTF PDF LaTeX \| Exporter enregistrement: BibTeX Endnote ISI RIS Atom XML MODS XML ODF XML Word XML

publications

2013-05-17T12:06:08Z

2011
Chiaravalloti, F., Dujardin, G., Riedel, D., Pinto, H. P., & Foster, A. S. (2011). Atomic-scale study of the adsorption of calcium fluoride on Si(100) at low-coverage regime. PHYSICAL REVIEW B, 84(15), 155433. Résumé: We investigate, experimentally and theoretically, the initial stage of the formation of Ca/Si and Si/F structures that occurs during the adsorption of CaF(2) molecules onto a bare Si(100) surface heated to 1000 Kin a low-coverage regime (0.3 monolayer). A low-temperature (5 K) scanning tunneling microscope (STM) is used to observe the topographies and the electronic properties of the exposed silicon surfaces. Our atomic-scale study reveals that several chemical reactions arise during CaF(2) deposition, such as dissociation of the CaF(2) molecules and etching of the surface silicon dimers. The experimental and calculated STM topographies are compared using the density functional theory, and this comparison enables us to identify two types of reacted structures on the Si(100) surface. The first type of observed complex surface structure consists of large islands formed with a semiperiodic sequence of 3 x 2 unit cells. The second one is made of isolated Ca adatoms adsorbed at specific sites on the Si(100)-2 x 1 surface. Permanent link \| Stocker citation: RTF PDF LaTeX \| Exporter enregistrement: BibTeX Endnote ISI RIS Atom XML MODS XML ODF XML Word XML
2010
Bellec, A., Riedel, D., Dujardin, G., Boudrioua, O., Chaput, L., Stauffer, L., et al. (2010). Nonlocal Activation of a Bistable Atom through a Surface State Charge-Transfer Process on Si(100)-(2 x 1):H. PHYSICAL REVIEW LETTERS, 105(4), 048302. Résumé: The reversible hopping of a bistable atom on the Si(100)-(2 x 1):H surface is activated nonlocally by hole injection into Si-Si bond surface states with a low temperature (5 K) scanning tunneling microscope. In the contact region, at short distances (<1.5 nm) between the hole injection site and the bistable atom, the hopping yield of the bistable atom exhibits remarkable variations as a function of the hole injection site. It is explained by the density of state distribution along the silicon bond network that shows charge-transfer pathways between the injection sites and the bistable atom. Permanent link \| Stocker citation: RTF PDF LaTeX \| Exporter enregistrement: BibTeX Endnote ISI RIS Atom XML MODS XML ODF XML Word XML
Riedel, D. (2010). Single molecule manipulation at low temperature and laser scanning tunnelling photo-induced processes analysis through time-resolved studies. JOURNAL OF PHYSICS-CONDENSED MATTER, 22(26), 264009. Résumé: This paper describes, firstly, the statistical analysis used to determine the processes that occur during the manipulation of a single molecule through electronically induced excitations with a low temperature (5 K) scanning tunnelling microscope (STM). Various molecular operation examples are described and the ability to probe the ensuing molecular manipulation dynamics is discussed within the excitation context. It is, in particular, shown that such studies can reveal reversible manipulation for tuning dynamics through variation of the excitation energy. Secondly, the photo-induced process arising from the irradiation of the STM junction is also studied through feedback loop dynamics analysis, allowing us to distinguish between photo-thermally and photo-electronically induced signals. Permanent link \| Stocker citation: RTF PDF LaTeX \| Exporter enregistrement: BibTeX Endnote ISI RIS Atom XML MODS XML ODF XML Word XML
Riedel, D., Delattre, R., Borisov, A. G., & Teperik, T. V. (2010). A Scanning Tunneling Microscope as a Tunable Nanoantenna for Atomic Scale Control of Optical-Field Enhancement. NANO LETTERS, 10(10), 3857–3862. Résumé: The high stability of a low temperature (9 K) scanning tunneling microscope junction is used to precisely adjust the enhancement of an external pulsed vacuum ultraviolet (VUV) laser The ensuing VUV optical-field strength is mapped on an hydrogenated Si(100) surface by imprinting locally one-photon atomic scale hydrogen desorption Subsequent to irradiation, topography of the Si(100) H surface at the reacted area revealed a desorption spot with unprecedented atomic precision Our results show that the shapes. positions. and sizes of the desorption spots are correlated to the calculated optical-field structure, offering real control of the optical-held distribution at molecular scale Permanent link \| Stocker citation: RTF PDF LaTeX \| Exporter enregistrement: BibTeX Endnote ISI RIS Atom XML MODS XML ODF XML Word XML
2009
Bellec, A., Ample, F., Riedel, D., Dujardin, G., & Joachim, C. (2009). Imaging Molecular Orbitals by Scanning Tunneling Microscopy on a Passivated Semiconductor. NANO LETTERS, 9(1), 144–147. Résumé: Decoupling the electronic properties of a molecule from a substrate is of crucial importance for the development of single-molecule electronics. This is achieved here by adsorbing pentacene molecules at low temperature on a hydrogenated Si(100) surface (12 K). The low temperature (5 K) scanning tunneling microscope (STM) topography of the single pentacene molecule at the energy of the highest occupied molecular orbital (HOMO) tunnel resonance clearly resembles the native HOMO of the free molecule. The negligible electronic coupling between the molecule and the substrate is confirmed by theoretical STM topography and diffusion barrier energy calculations. Permanent link \| Stocker citation: RTF PDF LaTeX \| Exporter enregistrement: BibTeX Endnote ISI RIS Atom XML MODS XML ODF XML Word XML
Bellec, A., Riedel, D., Dujardin, G., Boudrioua, O., Chaput, L., Stauffer, L., et al. (2009). Electronic properties of the n-doped hydrogenated silicon (100) surface and dehydrogenated structures at 5 K. PHYSICAL REVIEW B, 80(24), 245434. Résumé: We present a comparative study of the electronic properties of the clean Si(100) and the hydrogenated Si(100):H surfaces performed with a low-temperature (5 K) scanning tunneling microscope. Various surface structures such as single silicon dangling bonds and bare silicon dimers created by local desorption of hydrogen atoms from the Si(100):H surface are also investigated. The experimental scanning tunneling spectroscopy (STS) curves acquired locally on each of these structures are compared with STS measurements performed on the Si(100) and Si(100):H surfaces. First principle density-functional theory calculations of the projected local density of states, taking into account the influence of the dopant atoms (As), enable to assign the observed STS spectra. Permanent link \| Stocker citation: RTF PDF LaTeX \| Exporter enregistrement: BibTeX Endnote ISI RIS Atom XML MODS XML ODF XML Word XML
Chiaravalloti, F., Riedel, D., Dujardin, G., Pinto, H. P., & Foster, A. S. (2009). STM topography and manipulation of single Au atoms on Si(100). PHYSICAL REVIEW B, 79(24), 245431. Résumé: The low-temperature (12 K) adsorption of single Au atoms on Si(100) is studied by scanning tunneling microscopy (STM). Comparison between experimental and calculated STM topographies as well as density-functional-theory calculations of the adsorption energies enable us to identify two adsorption configurations of Au atoms between Si-dimer rows (BDRs) and on top of Si-dimer rows (TDRs). In both adsorption configurations, the Au atoms are covalently bound to two Si atoms through a partial electron transfer from Si to Au. STM manipulation confirms that the TDR adsorption configuration is metastable, whereas the BDR one is the most stable configuration. Permanent link \| Stocker citation: RTF PDF LaTeX \| Exporter enregistrement: BibTeX Endnote ISI RIS Atom XML MODS XML ODF XML Word XML
Riedel, D., Bocquet, M. L., Lesnard, H., Lastapis, M., Lorente, N., Sonnet, P., et al. (2009). Selective Scanning Tunnelling Microscope Electron-induced Reactions of Single Biphenyl Molecules on a Si(100) Surface. JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 131(21), 7344–7352. Résumé: Selective electron-induced reactions of individual biphenyl molecules adsorbed in their weakly chemisorbed configuration on a Si(100) surface are investigated by using the tip of a low-temperature (5 K) scanning tunnelling microscope (STM) as an atomic size source of electrons. Selected types of molecular reactions are produced, depending on the polarity of the surface voltage during STM excitation. At negative surface voltages, the biphenyl molecule diffuses across the surface in its weakly chemisorbed configuration. At positive surface voltages, different types of molecular reactions are activated, which involve the change of adsorption configuration from the weakly chemisorbed to the strongly chemisorbed bistable and quadristable configurations. Calculated reaction pathways of the molecular reactions on the silicon surface, using the nudge elastic band method, provide evidence that the observed selectivity as a function of the surface voltage polarity cannot be ascribed to different activation energies. These results, together with the measured threshold surface voltages and the calculated molecular electronic structures via density functional theory, suggest that the electron-induced molecular reactions are driven by selective electron detachment (oxidation) or attachment (reduction) processes. Permanent link \| Stocker citation: RTF PDF LaTeX \| Exporter enregistrement: BibTeX Endnote ISI RIS Atom XML MODS XML ODF XML Word XML
Riedel, D., Cranney, M., Martin, M., Guillory, R., Dujardin, G., Dubois, M., et al. (2009). Surf ace-Isomerization Dynamics of trans-Stilbene Molecules Adsorbed on Si(100)-2x1. JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 131(15), 5414–5423. Résumé: Photoinduced trans-cis isomerization studies of stilbene molecules in the gas phase have led to a precise understanding of the corresponding molecular dynamics. Yet, when such molecules are adsorbed on surfaces, these reactions are expected to be strongly modified as compared to what is know in the gas phase. In this work, a low temperature (5 K) scanning tunneling microscope (STM) is used to image the trans-stilbene molecules deposited on a Si(100)-2x1 surface at 12 K. trans-Stilbene undergoes conformational changes during the adsorption process such that four different stilbene conformers are observed: trans-stilbene (TS), cis-stilbene (CS), and two new conformers I(1) and I(2). Furthermore, electronic excitation of individual stilbene molecules, by means of tunnel electrons, is shown to activate specific reversible molecular surface isomerization (TS <-> I(1) and CS <-> I(2)) combined with diffusion across the surface. Calculated STM topographies, using the tight binding method, indicate that the CS and TS molecules are physisorbed. The molecular conformations of the surface isomers I(1) and I(2) are suggested to be analogous to transient states conformations of the stilbene molecule when stabilized by the silicon surface. The measurements of the molecular surface isomerization and diffusion reaction yields are used to build a qualitative potential energy surface of the various stilbene reactions. The molecular surface-isomerization dynamics is shown to be influenced by the type of dopant (n or p). This is related to surface charging, which reveals modifications in the stilbene ionization potential. Permanent link \| Stocker citation: RTF PDF LaTeX \| Exporter enregistrement: BibTeX Endnote ISI RIS Atom XML MODS XML ODF XML Word XML
2008
Bellec, A., Riedel, D., Dujardin, G., Rompotis, N., & Kantorovich, L. N. (2008). Dihydride dimer structures on the Si(100):H surface studied by low-temperature scanning tunneling microscopy. PHYSICAL REVIEW B, 78(16), 165302. Résumé: Surface reconstructions on the hydrogenated Si(100):H surface are observed and investigated by using a low-temperature (5 K) scanning tunneling microscope (STM). In addition to the well established 2x1 and 3x1 phases, linear structures extending over one to six silicon dimers along the same dimer row are observed. After a careful analysis of the corresponding STM topographies for both n-type and p-type doped silicon substrates, we conclude that these structures are dihydride dimers. This assignment is supported by ab initio density-functional calculations of the local density of states of dihydride structures of one or two dimers long. Furthermore, the calculation of the free-energy formation of our observed structure shows that their creation is closely linked with the hydrogenation process. These results demonstrate that the previous assignments of “split dimer” and “bow-tie” structures to dihydride dimers and dopant pairs, respectively, need to be reconsidered. Permanent link \| Stocker citation: RTF PDF LaTeX \| Exporter enregistrement: BibTeX Endnote ISI RIS Atom XML MODS XML ODF XML Word XML
Lastapis, M., Martin, M., Riedel, D., & Dujardin, G. (2008). Role of the dopant in silicon on the dynamics of a single adsorbed molecule. PHYSICAL REVIEW B, 77(12), 125316. Résumé: We investigate the role of the dopant in silicon on the dynamics of a single adsorbed molecule. We demonstrate that the dynamics of a single bistable molecule, a biphenyl molecule, adsorbed on a Si (100)-(2x1) surface is markedly dependent on the silicon type of doping (p or n) even though the electronic excitation and relaxation processes are unchanged. Both strongly and weakly chemisorbed individual biphenyl molecules are shown to interact differently with p- or n-doped Si (100) surfaces, thus inducing different stabilities of the adsorption configurations and different molecular dynamics. These effects rely on electrostatic interactions between distributed charges inside the molecule and charged surface states. The described phenomenon, which is a priori general, should be applicable to most of the molecules adsorbed on doped semiconductors having surface states in their band gap. This result is anticipated to have important applications in molecular electronic for positioning individual molecules with precision. Permanent link \| Stocker citation: RTF PDF LaTeX \| Exporter enregistrement: BibTeX Endnote ISI RIS Atom XML MODS XML ODF XML Word XML

Publications

2013-05-17T12:01:10Z

2011
Wang, T., Boer-Duchemin, E., Zhang, Y., Comtet, G., & Dujardin, G. (2011). Excitation of propagating surface plasmons with a scanning tunnelling microscope. NANOTECHNOLOGY, 22(17), 175201. Résumé: Inelastic electron tunnelling excitation of propagating surface plasmon polaritons (SPPs) on a thin gold film is demonstrated. This is done by combining a scanning tunnelling microscope (STM) with an inverted optical microscope. Analysis of the leakage radiation in both the image and Fourier planes unambiguously shows that the majority (up to 99.5%) of the detected photons originate from propagating SPPs with propagation lengths of the order of 10 μm. The remaining photon emission is localized under the STM tip and is attributed to a tip-gold film coupled plasmon resonance as evidenced by the bimodal spectral distribution and enhanced emission intensity observed using a silver STM tip for excitation. Permanent link \| Stocker citation: RTF PDF LaTeX \| Exporter enregistrement: BibTeX Endnote ISI RIS Atom XML MODS XML ODF XML Word XML

2012
Bulard, E., Fontaine-Aupart, M. - P., Dubost, H., Zheng, W., Bellon-Fontaine, M. - N., Herry, J. - M., et al. (2012). Competition of Bovine Serum Albumin Adsorption and Bacterial Adhesion onto Surface-Grafted ODT: In Situ Study by Vibrational SFG and Fluorescence Confocal Microscopy. LANGMUIR, 28(49), 17001–17010. Résumé: The interaction of hydrophilic and hydrophobic ovococcoid bacteria and bovine serum albumin (BSA) proteins with a well ordered surface of octadecanethiol (ODT) self assembled monolayer (SAM) has been studied in different situations where proteins were either preadsorbed on ODT or adsorbed simultaneously with bacterial adhesion as in life conditions. The two situations lead to very different antimicrobial behavior. Bacterial adhesion on preadsorbed BSA is very limited, while the simultaneous exposure of ODT SAM to proteins and bacteria lead to a markedly weaker antimicrobial effect. The combination of sum frequency generation spectroscopy and fluorescence confocal microscopy experiments allow one to draw conclusions on the factors that govern the ODT SAM or BSA film interaction with bacteria at the molecular level. On the hydrophobic ODT surface, interaction with hydrophobic or hydrophilic biomolecules results in opposite effects on the SAM, namely, a flattening or a raise of the terminal methyl groups of ODT. On an amphiphilic BSA layer, the bacterial adhesion strength is weakened by the negative charges carried by both BSA and bacteria. Surprisingly, preadsorbed BSA that cover part of the bacteria cell walls increase the adhesion strength to the BSA film and reduce hydrophobic interactions with the ODT SAM. Finally, bacterial adhesion on a BSA film is shown to modify the BSA proteins in some way that change their interaction with the ODT SAM. The antimicrobial effect is much stronger in the case of a preadsorbed BSA layer than when BSA and bacteria are in competition to colonize the ODT SAM surface. Permanent link \| Stocker citation: RTF PDF LaTeX \| Exporter enregistrement: BibTeX Endnote ISI RIS Atom XML MODS XML ODF XML Word XML
Bulard, E., Fontaine-Aupart, M. - P., Dubost, H., Zheng, W., Herry, J. - M., Bellon-Fontaine, M. - N., et al. (2012). The Effect of Bacterial Adhesion on Grafted Chains Revealed by the Non-Invasive Sum Frequency Generation Spectroscopy. SPECTROSCOPY-AN INTERNATIONAL JOURNAL, 27(5-6), 571–579. Résumé: In biomedical and food industry, surface colonization by bacteria is harmful: it leads to biofilm formation, a microbial consortia more resistant to antibiotics than planktonic bacteria. In order to design materials able to limit the biofilm formation, the effect of bacteria on materials has to be well characterized. In this work, a well-defined surface composed of a self-assembled monolayer (SAM) of octadecanethiol (ODT) onto a gold surface is probed in situ. The SAM conformation is obtained using the femtosecond vibrational sum frequency generation (SFG) spectroscopy. This technique provides selectively the molecular vibrational signature of the interface. The behaviour of the ODT SAM is studied in different environments: in air, in water, and upon exposure to hydrophilic or hydrophobic Lactococcus lactis bacteria. Modelling the experimental SFG spectra reveals a measurable change of the SAM conformation which depends on the environment, especially on the hydrophilic-hydrophobic character. Permanent link \| Stocker citation: RTF PDF LaTeX \| Exporter enregistrement: BibTeX Endnote ISI RIS Atom XML MODS XML ODF XML Word XML
Fan, C., Poumellec, B., Zeng, H., Desmarchelier, R., Bourguignon, B., Chen, G., et al. (2012). Gold Nanoparticles Reshaped by Ultrafast Laser Irradiation Inside a Silica-Based Glass, Studied Through Optical Properties. JOURNAL OF PHYSICAL CHEMISTRY C, 116(4), 2647–2655. Résumé: Quasi-spherical or quasi-rod gold nanoparticles with an average diameter of 3.8 nm are randomly precipitated in a silica-based glass by a heat-treatment method. After ultrafast laser irradiation at 400 and 620 nm, optical absorption, birefringence, and dichroism measurements are performed to investigate the modification of gold nanoparticles shape. Theoretical simulations have been carried out to interpret the experimental results. We suggest that a small fraction of gold nanospheres are transformed mainly into nanodisks but also into nanorods oriented along the laser polarization for both fs laser wavelength. Absorption simulation suggests that they have an aspect ratio of 1.8 and 0.5, respectively, for fs laser irradiation at 400 nm. For 620 nm, the aspect ratio of the nanorods increases and the one of the nanodisks decreases. In such a way, we demonstrate that reshaping of gold nanoparticles, i.e. a property that was previously found for silver nanoparticles in multicomponent glass is also possible. By imaging the distribution of the birefringence according to the probe wavelength, we show that nanopartides are aligned into nanorods mainly out of irradiated volume and into nanopellets mainly in the irradiated volume. Permanent link \| Stocker citation: RTF PDF LaTeX \| Exporter enregistrement: BibTeX Endnote ISI RIS Atom XML MODS XML ODF XML Word XML
Lancry, M., Poumellec, B., Desmarchelier, R., & Bourguignon, B. (2012). Oriented creation of anisotropic defects by IR femtosecond laser scanning in silica. OPTICAL MATERIALS EXPRESS, 2(12), 1809–1821. Résumé: Irradiation of non-luminescent silica with polarized IR femtosecond laser light produced a significant amount of luminescent defects. We have investigated the properties of luminescence produced by the defects using UV-VUV excitation experiment depending on the relative orientation of the laser polarization and its scanning direction. Silicon Oxygen Deficient Center (SiODC) is identified. SiODC related luminescence is much stronger when the excitation polarization is parallel to the sample scanning direction and moved at low velocity, regardless of the writing polarization direction. This indicates that the creation of this anisotropic defect is oriented by the movement of the femtosecond laser beam. (C)2012 Optical Society of America Permanent link \| Stocker citation: RTF PDF LaTeX \| Exporter enregistrement: BibTeX Endnote ISI RIS Atom XML MODS XML ODF XML Word XML
2011
Bulard, E., Dubost, H., Fontaine-Aupart, M. - P., Zheng, W., Herry, J. - M., Bellon-Fontaine, M. - N., et al. (2011). Non invasive SFG spectroscopy: a tool to reveal the conformational change of grafted chains due to bacterial adhesion (Vol. 8087). Résumé: In many fields such as biomedical or food industry, surface colonization by micro-organisms leads to biofilms formation that are tridimentional biostructures highly resistant to the action of antimicrobials, by mechanisms still unclear. In order to deepen our understanding of the initial interaction of bacteria cells with a solid surface, we analyze by in situ vibrational Sum Frequency Generation (SFG) spectroscopy the effect of the adhesion of hydrophilic Lactoccocus lactis bacteria and its hydrophobic mutants in distilled water on a self-assembled monolayer (SAM) of octadecanethiol (ODT) on a gold film. When a homogeneous bacterial monolayer is deposited on this ordered surface, SFG spectrum of the ODT SAM shows significant intensity changes from that in air or in water. Its modelling as a function of conformation allows to distinguish optical effects due to the water solution surrounding bacteria from conformational changes of the ODT SAM due to the presence of the bacteria cells. Futhermore, bacterial adhesion induces different measurable effects on the ODT SAM conformation, depending on the hydrophobic / hydrophilic character of the bacterial surface. Such a result deserves to be taken into account for the design of new materials with improved properties or to control biofilm formation. Permanent link \| Stocker citation: RTF PDF LaTeX \| Exporter enregistrement: BibTeX Endnote ISI RIS Atom XML MODS XML ODF XML Word XML
Bulard, E., Guo, Z., Zheng, W., Dubost, H., Fontaine-Aupart, M. - P., Bellon-Fontaine, M. - N., et al. (2011). Non-Invasive Vibrational SFG Spectroscopy Reveals That Bacterial Adhesion Can Alter the Conformation of Grafted “Brush” Chains on SAM. LANGMUIR, 27(8), 4928–4935. Résumé: Understanding bacterial adhesion on a surface is a crucial step to design new materials with improved properties or to control biofilm formation and eradication. Sum Frequency Generation (SFG) vibrational spectroscopy has been employed to study in situ the conformational response of a self-assembled monolayer (SAM) of octadecanethiol (ODT) on a gold film to the adhesion of hydrophilic and hydrophobic ovococcoid model bacteria. The present work highlights vibrational SFG spectroscopy as a powerful and unique non-invasive biophysical technique to probe and control bacteria interaction with ordered surfaces. Indeed, the SFG vibrational spectral changes reveal different ODT SAM conformations in air and upon exposure to aqueous solution or bacterial adhesion. Furthermore, this effect depends on the bacterial cell surface properties. The SFG spectral modeling demonstrates that hydrophobic bacteria flatten the ODT SAM alkyl chain terminal part, whereas the hydrophilic ones raise this ODT SAM terminal part. Microorganism-induced alteration of grafted chains can thus affect the desired interfacial functionality, a result that should be considered for the design of new reactive materials. Permanent link \| Stocker citation: RTF PDF LaTeX \| Exporter enregistrement: BibTeX Endnote ISI RIS Atom XML MODS XML ODF XML Word XML
Fan, C., Poumellec, B., Zeng, H., Lancry, M., Yang, W., Bourguignon, B., et al. (2011). Directional Writing Dependence of Birefringence in Multicomponent Silica-based Glasses with Ultrashort Laser Irradiation. JOURNAL OF LASER MICRO NANOENGINEERING, 6(2), 158–163. Résumé: We reveal laser-induced high birefringence in multicomponent silica-based glass by means of ultrashort laser irradiation. It is attributed to the residual stress. A systematic study of birefringence variation is carried out according to laser parameters such as pulse energy, writing speed and direction, and laser polarization. Strong writing directional dependence is clearly observed when the writing direction is perpendicular to the laser polarization at the writing speeds of 20 μm/s – 120 μm/s, which was likely due to an asymmetry of the laser beam or an asymmetry of interaction mechanism. DOI: 10.2961/jlmn.2011.02.0011 Permanent link \| Stocker citation: RTF PDF LaTeX \| Exporter enregistrement: BibTeX Endnote ISI RIS Atom XML MODS XML ODF XML Word XML
Ouvrard, A., Niebauer, J., Ghalgaoui, A., Barth, C., Henry, C. R., & Bourguignon, B. (2011). Characterization of Thin MgO Films on Ag(001) by Low-Energy Electron Diffraction and Scanning Tunneling Microscopy. JOURNAL OF PHYSICAL CHEMISTRY C, 115(16), 8034–8041. Résumé: The evolution of the MgO(001) film morphology on Ag(001) was studied in dependence on the growth temperature (373-673 K) and grown MgO quantity (0.2-2 ML) by low-energy electron diffraction and scanning tunneling microscopy. We evidence an island growth mode of MgO for all temperatures. At 373 K, the MgO film exhibits a high island density, which is due to a too small surface mobility of the film compounds during the film growth. At a growth temperature of 673 K, silver hampers a perfect growth of MgO islands due to its high mobility, which leads to dendrites of MgO. The flattest and. largest MgO islands are obtained at a growth temperature of around 573 K, which is a compromise guaranteeing a sufficiently high Mg or MgO mobility but also an enough low diffusion of silver. Permanent link \| Stocker citation: RTF PDF LaTeX \| Exporter enregistrement: BibTeX Endnote ISI RIS Atom XML MODS XML ODF XML Word XML
2009
Bourguignon, B., Zheng, W., Carrez, S., Ouvrard, A., Fournier, F., & Dubost, H. (2009). Deriving the complete molecular conformation of self-assembled alkanethiol molecules from sum-frequency generation vibrational spectra. PHYSICAL REVIEW B, 79(12). Résumé: The sum frequency generation (SFG) spectrum of CH(2) and CH(3) modes in the self-assembled monolayer of octadecanethiol is modeled in order to understand the reasons of the very low SFG intensity of CH(2) modes and to investigate quantitatively the two types of L-shaped conformations qualitatively suggested in the literature. CH(2) modes are assumed local in order to calculate easily the spectrum of any conformation, and ab initio molecular hyperpolarizabilities are used. It is found that the absence of CH(2) bands does not imply an all-trans conformation and vice versa. Several conformations are compatible with SFG, but only one of them can be arranged on Au(111) and completely agrees with x-ray diffraction. All conformational details of the L-shape molecules are obtained. Permanent link \| Stocker citation: RTF PDF LaTeX \| Exporter enregistrement: BibTeX Endnote ISI RIS Atom XML MODS XML ODF XML Word XML
2008
Guo, Z., Zheng, W., Hamoudi, H., Dablemont, C., Esaulov, V. A., & Bourguignon, B. (2008). On the chain length dependence of CH3 vibrational mode relative intensities in sum frequency generation spectra of self assembled alkanethiols. SURFACE SCIENCE, 602(23), 3551–3559. Résumé: A global modelling of Sum Frequency Generation (SFG) spectra of the self assembly of alkanethiols is presented. All CH modes are modelled together. CH2 modes are assumed local to allow easy calculation of the spectrum as a function of molecular conformation. Ab initio molecular hyperpolarizabilities are used. A phenomenological approach is used to include the Fermi resonance in the model: the calculated intensity of the CH3 symmetric stretch is redistributed according to intensity borrowing by the Fermi resonance. The model is applied to octadecanethiol (ODT) and pentadecanethiol (PDT). The even/odd intensity alternation of SFG CH3 vibrational bands as a function of chainlength is used to test the model. It is found that the relative magnitudes of the hyperpolarizability tensors of the CH3 asymmetric and symmetric modes need to be adjusted. The model provides tilt and twist angles of the alkyl chain in agreement with the literature. It shows that the all trans conformation does not imply the absence of CH2 bands in SFG spectra. In addition, new information is obtained. In particular, if two types of molecular conformations are assumed, the C planes of the two molecules must be perpendicular to each other. (C) 2008 Elsevier B.V. All rights reserved. Permanent link \| Stocker citation: RTF PDF LaTeX \| Exporter enregistrement: BibTeX Endnote ISI RIS Atom XML MODS XML ODF XML Word XML
Hamoudi, H., Guo, Z., Prato, M., Dablemont, C., Zheng, W. Q., Bourguignon, B., et al. (2008). On the self assembly of short chain alkanedithiols. PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 10(45), 6836–6841. Résumé: A study of the self-assembly of nonane-alkanedithiol monolayers on gold in n-hexane and ethanol solvents is presented. Self-assembled monolayers (SAMs) are characterised by reflection-absorption infrared spectroscopy (RAIRS), sum frequency generation (SFG) and spectroscopic ellipsometry (SE) measurements. Data obtained for alkanethiols SAMs are also shown for comparison. The measurements show that nicely organized HSC(9)SH SAMs can be obtained in n-hexane provided that N(2)-degassed solutions are used and all preparation steps are performed in the absence of ambient light. SFG measurements show that these SAMs have free standing SH groups. Use of an un-degassed and/or light-exposed n-hexane solutions leads to a worse layer organization. Preparation in ethanol, even in degassed solutions with processing in the dark, leads to poorly organized layers and no sign of free-SH groups was observed. Permanent link \| Stocker citation: RTF PDF LaTeX \| Exporter enregistrement: BibTeX Endnote ISI RIS Atom XML MODS XML ODF XML Word XML

2013
Hoendervanger, A. L., Clement, D., Aspect, A., Westbrook, C. I., Dowek, D., Picard, Y. J., et al. (2013). Influence of gold coating and interplate voltage on the performance of chevron micro-channel plates for temporally and spatially resolved single particle detection. The Review of scientific instruments, 84(2), 023307. Résumé: We present a study of two different sets of Micro-Channel Plates used for time and space resolved single particle detection. We investigate the effects of the gold coating and that of introducing an interplate voltage between the spatially separated plates. We find that the gold coating increases the count rate of the detector and the pulse amplitude as previously reported for non-spatially resolved setups. The interplate voltage also increases count rates. In addition, we find that a non-zero interplate voltage improves the spatial accuracy in determining the arrival position of incoming single particles (by ~20%) while the gold coating has a negative effect (by ~30%). Permanent link \| Stocker citation: RTF PDF LaTeX \| Exporter enregistrement: BibTeX Endnote ISI RIS Atom XML MODS XML ODF XML Word XML
2012
Billaud, P., Geleoc, M., Picard, Y. J., Veyrinas, K., Hergott, J. F., Poullain, S. M., et al. (2012). Molecular frame photoemission in dissociative ionization of H-2 and D-2 induced by high harmonic generation femtosecond XUV pulses. JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS, 45(19). Résumé: We report the first results of molecular frame photoelectron emission for dissociative photoionization (DPI) of H-2 and D-2 molecules induced by a spectrally filtered single high harmonic of a few femtosecond duration, using coincident electron-ion velocity vector correlation techniques. For the studied photon energies around 32 eV, where the resonant excitation of the Q(1) and Q(2) doubly excited states occurs, autoionization and nuclear dynamics are coupled on a few femtosecond timescale, giving rise to quantum interferences. Molecular frame photoelectron angular distributions (MFPADs), traced as a function of the kinetic energy release of the atomic fragments, provide the most sensitive observables for such complex dynamics. These results compare well with recent spectrally resolved experiments using synchrotron radiation which are also reported. As a novel XUV light source running at multi-kHz repetition rate and synchronized with laser pulses, high-order harmonic generation (HHG) opens new possibilities for extending these investigations to time-resolved studies at the femtosecond scale. Permanent link \| Stocker citation: RTF PDF LaTeX \| Exporter enregistrement: BibTeX Endnote ISI RIS Atom XML MODS XML ODF XML Word XML
Lebech, M., Houver, J. C., Raseev, G., dos Santos, A. S., Dowek, D., & Lucchese, R. R. (2012). Valence and inner-valence shell dissociative photoionization of CO in the 26-33 eV range. II. Molecular-frame and recoil-frame photoelectron angular distributions. JOURNAL OF CHEMICAL PHYSICS, 136(9). Résumé: Experimental and theoretical results for molecular-frame photoemission are presented for inner-valence shell photoionization of the CO molecule induced by linearly and circularly polarized light. The experimental recoil frame photoelectron angular distributions (RFPADs) obtained from dissociative photoionization measurements where the velocities of the ionic fragment and photoelectron were detected in coincidence, are compared to RFPADs computed using the multichannel Schwinger configuration interaction method. The formalism for including a finite lifetime of the predissociative ion state is presented for the case of general elliptically polarized light, to obtain the RFPAD rather than the molecular frame photoelectron angular distribution (MFPAD), which would be obtained with the assumption of instantaneous dissociation. We have considered photoionization of CO for the photon energies of 26.0 eV, 29.5 eV, and 32.5 eV. A comparison of experimental and theoretical RFPADs allows us to identify the ionic states detected in the experimental studies. In addition to previously identified states, we found evidence for the 2 (2)Delta state with an ionization potential of 25.3 eV and (2)Sigma(+) states with ionization potentials near 32.5 eV. A comparison of the experimental and theoretical RFPADs permits us to estimate predissociative lifetimes of 0.25-1 ps for some of the ion states. Consideration of the MFPADs of a series of (2)Pi ion states indicates the importance of inter-channel coupling at low photoelectron kinetic energy and the limitations of a single-channel analysis based on the corresponding Dyson orbitals. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.3681920] Permanent link \| Stocker citation: RTF PDF LaTeX \| Exporter enregistrement: BibTeX Endnote ISI RIS Atom XML MODS XML ODF XML Word XML
2011
Siu, W., Kelkensberg, F., Gademann, G., Rouzee, A., Johnsson, P., Dowek, D., et al. (2011). Attosecond control of dissociative ionization of O-2 molecules. PHYSICAL REVIEW A, 84(6). Résumé: We demonstrate that dissociative ionization of O-2 can be controlled by the relative delay between an attosecond pulse train (APT) and a copropagating infrared (IR) field. Our experiments reveal a dependence of both the branching ratios between a range of electronic states and the fragment angular distributions on the extreme ultraviolet (XUV) to IR time delay. The observations go beyond adiabatic propagation of dissociative wave packets on IR-induced quasistatic potential energy curves and are understood in terms of an IR-induced coupling between electronic states in the molecular ion. Permanent link \| Stocker citation: RTF PDF LaTeX \| Exporter enregistrement: BibTeX Endnote ISI RIS Atom XML MODS XML ODF XML Word XML
2010
Dowek, D., Perez-Torres, J. F., Picard, Y. J., Billaud, P., Elkharrat, C., Houver, J. C., et al. (2010). Circular Dichroism in Photoionization of H-2. PHYSICAL REVIEW LETTERS, 104(23). Résumé: Circular dichroism is a consequence of chirality. However, nonchiral molecules can also exhibit it when the measurement itself introduces chirality, e. g., when measuring molecular-frame photoelectron angular distributions. The few such experiments performed on homonuclear diatomic molecules show that, as expected, circular dichroism vanishes when the molecular-frame photoelectron angular distributions are integrated over the polar electron emission angle. Here we show that this is not the case in resonant dissociative ionization of H-2 for photons of 30-35 eV, which is the consequence of the delayed ionization from molecular doubly excited states into ionic states of different inversion symmetry. Permanent link \| Stocker citation: RTF PDF LaTeX \| Exporter enregistrement: BibTeX Endnote ISI RIS Atom XML MODS XML ODF XML Word XML
Elkharrat, C., Picard, Y. J., Billaud, P., Cornaggia, C., Garzella, D., Perdrix, M., et al. (2010). Ion Pair Formation in Multiphoton Excitation of NO2 Using Linearly and Circularly Polarized Femtosecond Light Pulses: Kinetic Energy Distribution and Fragment Recoil Anisotropy (vol 114A, pg 9902, 2010). JOURNAL OF PHYSICAL CHEMISTRY A, 114(50), 13288. Permanent link \| Stocker citation: RTF PDF LaTeX \| Exporter enregistrement: BibTeX Endnote ISI RIS Atom XML MODS XML ODF XML Word XML
2009
Dowek, D., Haouas, A., Guillemin, R., Elkharrat, C., Houver, J. - C., Li, W. B., et al. (2009). Recoil frame photoemission in inner-shell photoionization of small polyatomic molecules. EUROPEAN PHYSICAL JOURNAL-SPECIAL TOPICS, 169, 85–93. Résumé: Going from a diatomic to a polyatomic linear or non-linear molecule, the description of molecular frame photoemission in photoionization of molecules involves a function of increasing complexity. Using the electron-ion Vector Correlation method, which provides the emission velocity vectors of the emitted charged particles in a dissociative photoionization reaction, generally gives access to Recoil Frame Photoelectron Angular Distributions (RFPADs). We report results for site selected inner-shell photoionization of the N(2)O molecule induced by elliptically polarized light, where the primary ionization reaction leads to the production of several fragmentation channels. Ion fragment kinetic energy release distributions as well as RFPADs are reported for selected two ion-channels containing the complete parent molecule. Experimental results are compared with recent multi-channel Schwinger configuration interaction (MCSCI) ab initio calculations at the level of the RFPADs. The link with the original computed molecular frame photoelectron angular distributions (MFPADs) is discussed. Permanent link \| Stocker citation: RTF PDF LaTeX \| Exporter enregistrement: BibTeX Endnote ISI RIS Atom XML MODS XML ODF XML Word XML
Dowek, D., Picard, Y. J., Billaud, P., Elkharrat, C., & Houver, J. C. (2009). Molecular Frame Photoemission: Probe of the Photoionization Dynamics for Molecules in the Gas Phase. CHINESE JOURNAL OF CHEMICAL PHYSICS, 22(2), 178–186. Résumé: Molecular frame photoemission is a very sensitive probe of the photoionization (PI) dynamics of molecules. This paper reports a comparative study of non-resonant and resonant photoionization of D(2) induced by VUV circularly polarized synchrotron radiation at SOLEIL at the level of the molecular frame photoelectron angular distributions (MFPADs). We use the vector correlation method which combines imaging and time-of-flight resolved electron-ion coincidence techniques, and a generalized formalism for the expression of the I(chi, theta(e), phi(e)) MFPADs, where chi is the orientation of the molecular axis with respect to the light quantization axis and (theta(e), phi(e)) the electron emission direction in the molecular frame. Selected MFPADs for a molecule aligned parallel or perpendicular to linearly polarized light, or perpendicular to the propagation axis of circularly polarized light, are presented for dissociative photoionization (DPI) of D(2) at two photon excitation energies, hv=19 eV, where direct PI is the only channel opened, and hv=32.5 eV, i.e. in the region involving resonant excitation of Q(1) and Q(2) doubly excited state series. We discuss in particular the properties of the circular dichroism characterizing photoemission in the molecular frame for direct and resonant PI. In the latter case, a remarkable behavior is observed which may be attributed to the interference occurring between undistinguishable autoionization decay channels. Permanent link \| Stocker citation: RTF PDF LaTeX \| Exporter enregistrement: BibTeX Endnote ISI RIS Atom XML MODS XML ODF XML Word XML
Lebech, M., Houver, J. C., & Dowek, D. (2009). Valence and inner-valence shell dissociative photoionization of CO in the 26-33 eV range. I. Ion-electron kinetic energy correlation and laboratory frame photoemission. JOURNAL OF CHEMICAL PHYSICS, 130(19), 194307. Résumé: The (V(A+), V(e), e) vector correlation method, combining imaging and time-of-flight resolved electron-ion coincidence techniques, is used to probe dissociative photoionization (DPI) of CO induced by vacuum ultra violet linearly or circularly polarized synchrotron radiation in the 26-33 eV photon excitation energy range. It provides original information about both the photoionization dynamics of the CO molecule and the dissociation dynamics of the CO(+) molecular ions. The explored region corresponds to valence and inner-valence CO(+) ionic states, which involve doubly or multiply excited electronic configurations. In this paper I we identify up to 17 DPI reaction pathways by the position of the intermediate CO(+) molecular states in the Franck-Condon region and the (C(+) + O) or (O(+) + C) dissociation limits to which they correlate. For these processes we report the laboratory frame beta(C+/O+) and beta(e) asymmetry parameters as well as the relative branching ratios in selected binding energy bands. The I(chi,theta(e),phi(e)) molecular frame photoelectron angular distributions for selected PI processes will be reported in a companion paper II and compared with multichannel Schwinger configuration interaction ab initio calculations of these observables. Permanent link \| Stocker citation: RTF PDF LaTeX \| Exporter enregistrement: BibTeX Endnote ISI RIS Atom XML MODS XML ODF XML Word XML
2008
Elkharrat, C., Picard, Y. J., Billaud, P., Houver, J. C., & Dowek, D. (2008). Electron-ion vector correlations for the study of photoionization of molecules in the UVX range: From synchrotron radiation to short light pulses. Résumé: Molecular frame photoemission is a very sensitive probe of the photoionization (PI) dynamics of molecules. The electron-ion vector correlation (VC) method takes advantage of dissociative photoionization (DPI) reactions of small molecules to measure such observables. It relies on the coincident detection of the photoelectron and the ion fragment emitted from the same DPI event and the determination of their velocity vectors. Most of the VC studies so far have been performed using synchrotron radiation (SR) light sources which benefit from a high repetition rate (1-10 MHz) favorable for coincidence experiments. In this paper we discuss the extension of this method to the study of PI processes induced by ultra-short VUV light sources, which provide the capability for investigating processes characterized by femtosecond or subfemtosecond dynamics. We first illustrate the VC method by the report of recent results of a comparative study of resonant photoionization of the H(2) and D(2) molecules induced by VUV circularly polarized synchrotron radiation at SOLEIL in the region involving resonant excitation of Q(1) and Q(2) doubly excited state series. This problem is of particular interest since autoionization and dissociation of selected Q, or Q(2) states occur on a comparable time scale of few femtoseconds, which implies a coupling between the electronic and nuclear motion. The extension of the VC method using femtosecond laser sources is then demonstrated by results for multiphoton PI of the Xe atom induced by 70 fs pulses centered at 400 nm delivered by the SOFOCKLE and PLFA Sources (SLIC, CEA-Saclay) after frequency doubling of a 1 kHz Ti:sapphire laser. Permanent link \| Stocker citation: RTF PDF LaTeX \| Exporter enregistrement: BibTeX Endnote ISI RIS Atom XML MODS XML ODF XML Word XML
Elkharrat, C., Picard, Y. J., Billaud, P., Houver, J. C., & Dowek, D. (2008). Electron-ion vector correlations for the study of photoionization of molecules in the UVX range: From synchrotron radiation to short light pulses. Résumé: Molecular frame photoemission is a very sensitive probe of the photoionization (PI) dynamics of molecules. The electron-ion vector correlation (VC) method takes advantage of dissociative photoionization (DPI) reactions of small molecules to measure such observables. It relies on the coincident detection of the photoelectron and the ion fragment emitted from the same DPI event and the determination of their velocity vectors. Most of the VC studies so far have been performed using synchrotron radiation (SR) light sources which benefit from a high repetition rate (1-10 MHz) favorable for coincidence experiments. In this paper we discuss the extension of this method to the study of PI processes induced by ultra-short VUV light sources, which provide the capability for investigating processes characterized by femtosecond or subfemtosecond dynamics. We first illustrate the VC method by the report of recent results of a comparative study of resonant photoionization of the H(2) and D(2) molecules induced by VUV circularly polarized synchrotron radiation at SOLEIL in the region involving resonant excitation of Q(1) and Q(2) doubly excited state series. This problem is of particular interest since autoionization and dissociation of selected Q, or Q(2) states occur on a comparable time scale of few femtoseconds, which implies a coupling between the electronic and nuclear motion. The extension of the VC method using femtosecond laser sources is then demonstrated by results for multiphoton PI of the Xe atom induced by 70 fs pulses centered at 400 nm delivered by the SOFOCKLE and PLFA Sources (SLIC, CEA-Saclay) after frequency doubling of a 1 kHz Ti:sapphire laser. Permanent link \| Stocker citation: RTF PDF LaTeX \| Exporter enregistrement: BibTeX Endnote ISI RIS Atom XML MODS XML ODF XML Word XML
Journel, L., Guillemin, R., Haouas, A., Lablanquie, P., Penent, F., Palaudoux, J., et al. (2008). Resonant double Auger decay in carbon K-shell excitation of CO. PHYSICAL REVIEW A, 77(4). Résumé: We have studied double Auger decay after C 1s -> 2 pi(*) photoexcitation in gas phase carbon monoxide. Two distinct processes, namely direct double Auger decay and cascade double Auger decay, are identified and studied in detail using multiple coincidence techniques. Cascade Auger decay is shown to be the overall dominant process. Decay channels involving the dissociation of the molecule followed by autoionization of the oxygen fragments are observed. Permanent link \| Stocker citation: RTF PDF LaTeX \| Exporter enregistrement: BibTeX Endnote ISI RIS Atom XML MODS XML ODF XML Word XML

2013
Ovramenko, T., Spillebout, F., Bocquet, F. C., Mayne, A. J., Dujardin, G., Sonnet, P., et al. (2013). STM imagery and density functional calculations of C-60 fullerene adsorption on the 6H-SiC(0001)-3x3 surface. PHYSICAL REVIEW B, 87(15), 155421. Résumé: Scanning tunneling microscopy (STM) studies of the fullerene C-60 molecule adsorbed on the silicon carbide SiC(0001)-3 x 3 surface, combined with density functional theory (DFT) calculations, show that chemisorption of individual C-60 molecules occurs through the formation of one bond to one silicon adatom only in contrast to multiple bond formation on other semiconducting surfaces. We observe three stable adsorption sites with respect to the Si adatoms of the surface unit cell. Comprehensive DFT calculations give different adsorption energies for the three most abundant sites showing that van der Waals forces between the C-60 molecule and the neighboring surface atoms need to be considered. The C-60 molecules are observed to form small clusters even at low coverage indicating the presence of a mobile molecular precursor state and nonnegligible intermolecular interactions. DOI: 10.1103/PhysRevB.87.155421 Permanent link \| Stocker citation: RTF PDF LaTeX \| Exporter enregistrement: BibTeX Endnote ISI RIS Atom XML MODS XML ODF XML Word XML
2012
Boudrioua, O., Yang, H., Sonnet, P., Stauffer, L., Mayne, A. J., Comtet, G., et al. (2012). Large organic molecule chemisorption on the SiC(0001) surface. PHYSICAL REVIEW B, 85(3), 035423. Résumé: We present a density-functional theory (DFT) study combined with scanning tunneling microscopy (STM) experiments of the chemisorption of the N,N'-bis(1-hexylheptyl) perylene-3,4:9,10-bis(dicarboximide) molecule, noted here as DHH-PTCDI, on the SiC(0001)-3 x 3 surface. Five possible adsorption configurations have been investigated in which molecular adsorption occurs on two adjacent Si adatoms via different pairs of atoms of the molecule. We have calculated the energies, structures, density of states, local density of states, and a calculated STM image and show that chemisorption via two oxygen atoms located on the same side of the molecule on two adjacent Si adatoms is the most favorable, in agreement with the experimental STM images. A comparison between the PTCDI and the adsorption of another large organic molecule (phthalocyanine) on the SiC(0001) surface completes this work. Permanent link \| Stocker citation: RTF PDF LaTeX \| Exporter enregistrement: BibTeX Endnote ISI RIS Atom XML MODS XML ODF XML Word XML
Westover, J., Enriquez, H., Oughaddou, H., & Kara, A. (2012). Metallization of the beta-SiC(100) 3x2 surface: A DFT investigation. SURFACE SCIENCE, 606(19-20), 1471–1474. Résumé: Using density functional theory (DFT) we report results for the electronic structure and vibrational dynamics of hydrogenated silicon carbide (001) (3 x 2) surfaces with various levels of hydrogenation. These results were obtained using density functional theory with a generalized gradient exchange correlation function. The calculations reveal that metallization can be achieved via hydrogen atoms occupying the second silicon layer. Further increase of hydrogen occupation on the second silicon layer sites results in a loss of this metallization. For the former scenario, where metallization occurs, we found a new vibrational mode at 1870 cm(-1), which is distinct from the mode associated with hydrogen atoms on the first layer. Furthermore, we found the diffusion barrier for a hydrogen atom to move from the second to the third silicon layer to be 258 meV. (c) 2012 Elsevier B.V. All rights reserved. Permanent link \| Stocker citation: RTF PDF LaTeX \| Exporter enregistrement: BibTeX Endnote ISI RIS Atom XML MODS XML ODF XML Word XML
Yang, H., Boudrioua, O., Mayne, A. J., Comtet, G., Dujardin, G., Kuk, Y., et al. (2012). The paradox of an insulating contact between a chemisorbed molecule and a wide band gap semiconductor surface. PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 14(5), 1700–1705. Résumé: Controlling the intrinsic optical and electronic properties of a single molecule adsorbed on a surface requires electronic decoupling of some molecular orbitals from the surface states. Scanning tunneling microscopy experiments and density functional theory calculations are used to study a perylene molecule derivative (DHH-PTCDI), adsorbed on the clean 3 x 3 reconstructed wide band gap silicon carbide surface (SiC(0001)-3 x 3). We find that the LUMO of the adsorbed molecule is invisible in I(V) spectra due to the absence of any surface or bulk states and that the HOMO has a very low saturation current in I(z) spectra. These results present a paradox that the molecular orbitals are electronically isolated from the surface of the wide band gap semiconductor even though strong chemical bonds are formed. Permanent link \| Stocker citation: RTF PDF LaTeX \| Exporter enregistrement: BibTeX Endnote ISI RIS Atom XML MODS XML ODF XML Word XML
2010
El Asri, T., Raissi, M., Vizzini, S., El Maachi, A., Ameziane, E. L., d'Avitaya, F. A., et al. (2010). Inter-diffusion of cobalt and silicon through an ultra thin aluminum oxide layer. APPLIED SURFACE SCIENCE, 256(9), 2731–2734. Résumé: Optical emission spectroscopy of sputtered species during ion bombardment, Auger electron spectroscopy and high-resolution transmission electron microscopy were used to study the cobalt and silicon diffusion through the interfaces of Co/AlO/Si(0 0 1) hetero-structure. The results are discussed as a function of the annealing temperature of sample and show that the diffusion process at the interfaces starts for annealing temperatures above 200 degrees C without detectable modification of the oxide layer. (C) 2009 Elsevier B. V. All rights reserved. Permanent link \| Stocker citation: RTF PDF LaTeX \| Exporter enregistrement: BibTeX Endnote ISI RIS Atom XML MODS XML ODF XML Word XML
2009
Baffou, G., Mayne, A. J., Comtet, G., Dujardin, G., Stauffer, L., & Sonnet, P. (2009). SiC(0001) 3 x 3 Heterochirality Revealed by Single-Molecule STM Imaging. JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 131(9), 3210–3215. Résumé: We report a description of the SiC(0001) 3 x 3 silicon carbide reconstruction based on single-molecule scanning tunneling microscopy (STM) observations and density functional theory calculations. We show that the SiC(0001) 3 x 3 reconstruction can be described as contiguous domains of right and left chirality distributed at the nanoscale, which breaks the to date supposed translational invariance of the surface. While this surface heterochirality remains invisible in STM topographies of clean surfaces, individual metal-free phthalocyanine molecules chemisorbed on the surface act as molecular lenses to reveal the surface chirality in the STM topographies. This original method exemplifies the ability of STM to probe atomic-scale structures in detail and provides a more complete vision of a frequently studied SiC reconstruction. Permanent link \| Stocker citation: RTF PDF LaTeX \| Exporter enregistrement: BibTeX Endnote ISI RIS Atom XML MODS XML ODF XML Word XML
Cranney, M., Chalopin, Y., Mayne, A. J., & Dujardin, G. (2009). Adsorption and organisation of para-hexaphenyl molecules on Si(100). APPLIED PHYSICS A-MATERIALS SCIENCE & PROCESSING, 94(4), 767–773. Résumé: Para-hexaphenyl molecules (p-6P: C(36)H(26)) can be grown as nanofibres on various surfaces having optical properties of technological relevance. We report here the first observations of the initial stages of adsorption of individual p-6P molecules on Si(100)-(2x1) using room temperature Scanning Tunnelling Microscopy (STM). Depending on the substrate temperature, the hexaphenyl molecules adsorb in two configurations; indicating both weak and strong chemisorption. All six phenyl rings are clearly visible and the molecules are found to adsorb with characteristic angles between the long axis of the molecule and the silicon dimer rows. A statistical analysis of the spatial distribution of the molecules suggests that the clustering required for crystallographic nanofibre growth does not occur at the atomic scale under the experimental conditions used here. Permanent link \| Stocker citation: RTF PDF LaTeX \| Exporter enregistrement: BibTeX Endnote ISI RIS Atom XML MODS XML ODF XML Word XML
Riedel, D., Delacour, C., Mayne, A. J., & Dujardin, G. (2009). Very low thermally induced tip expansion by vacuum ultraviolet irradiation in a scanning tunneling microscope junction. PHYSICAL REVIEW B, 80(15), 155451. Résumé: The thermal and photoelectronic processes induced when a vacuum ultraviolet (VUV) laser irradiates the junction of a scanning tunneling microscope (STM) are studied. This is performed by synchronizing the VUV laser shots with the STM scan signal. Compared to other wavelengths, the photoinduced thermal STM-tip expansion is not observed when the VUV radiation is freed from spurious emissions. Furthermore, we demonstrate that the purified VUV photoinduced transient signal detected in the tunnel current is entirely due to photoelectronic emission and not combined with thermionic processes. The ensuing photoelectron emission is shown to be independent of the tip-surface distance while varying linearly with the pure VUV laser intensity. These results illustrate a strong decoupling between phonons and photoelectrons which allows a very weak STM-tip expansion. Permanent link \| Stocker citation: RTF PDF LaTeX \| Exporter enregistrement: BibTeX Endnote ISI RIS Atom XML MODS XML ODF XML Word XML
Vizzini, S., Oughaddou, H., Hoarau, J. Y., Biberian, J. P., & Aufray, B. (2009). Y Growth of ultrathin film aluminum oxide on Ag(111). APPLIED PHYSICS LETTERS, 95(17), 173111. Résumé: Scanning tunneling microscopy (STM) and spectroscopy and electron energy loss spectroscopy were used to characterize ultrathin epitaxial aluminum oxide on Ag(111) which was prepared via a specific deposition and oxidation process. Atomically resolved STM images show self-organized oxide stripes of 4 nm width with excellent homogeneity in depth and chemical composition properties which are crucial for applications of this oxide to magnetic tunnel junctions. We also found that electrons tunnel easily through the oxide film. This oxide has a different spectroscopic signature from that of alumina and has a wide bandgap close to 6.6 eV. (C) 2009 American Institute of Physics. [doi:10.1063/1.3251778] Permanent link \| Stocker citation: RTF PDF LaTeX \| Exporter enregistrement: BibTeX Endnote ISI RIS Atom XML MODS XML ODF XML Word XML
2008
Baffou, G., Mayne, A. J., Comtet, G., & Dujardin, G. (2008). State selective electron transport through electronic surface states of 6H-SiC(0001)-3 x 3. PHYSICAL REVIEW B, 77(16), 165320. Résumé: We investigate charge transport through electronic surface states of the 6H-SiC(0001)-3 x 3 surface. Three intrinsic surface states are located within the wide bulk band gap, in which two (S(1) and U(1)) arise from strongly correlated electronic states and the third (S(2)) has negligible electron correlation effects. Combined conductance and luminescence experiments with the scanning tunneling microscope show that the Mott-Hubbard surface states (S(1) and U(1)) have a high resistance (1.0 G Omega), while the noncorrelated state (S(2)) has a negligible resistance. Consequently, current can be selectively transported through any of these three surface states. Permanent link \| Stocker citation: RTF PDF LaTeX \| Exporter enregistrement: BibTeX Endnote ISI RIS Atom XML MODS XML ODF XML Word XML
Mamatkulov, M., Stauffer, L., Sonnet, P., Mayne, A. J., Comtet, G., & Dujardin, G. (2008). Theoretical simulations of the tip-induced configuration changes of the 4,4 '-diacetyl-p-terphenyl molecule chemisorbed on Si(001). JOURNAL OF CHEMICAL PHYSICS, 128(24), 244710. Résumé: We have investigated from a theoretical point of view modifications of the 4,4'-diacetyl-p-terphenyl molecule chemisorbed on Si(001) induced by the scanning tunneling microscope (STM). In previous experiments, these modifications were observed to occur preferentially at the end of the molecule after a +4.0 V voltage pulse and at the center after a +4.5 V voltage pulse. In the framework of ab initio simulations, we have realized a systematic energetic study of the dissociative chemisorption of one, two, or three phenyl rings of the substituted p-terphenyl molecule. Charge densities were then calculated for the investigated configurations and compared to the STM topographies. Before manipulation with the STM tip, the substituted p-terphenyl molecule is preferentially adsorbed without phenyl ring dissociation, allowing a partial rotation of the central phenyl ring. Our results show that the STM induced modifications observed at the end of the molecule might originate from the dissociation of two phenyl rings (one central and one external ring), while the modifications occurring at the central part of the molecule can be interpreted as a dissociation of the two external rings. (c) 2008 American Institute of Physics. Permanent link \| Stocker citation: RTF PDF LaTeX \| Exporter enregistrement: BibTeX Endnote ISI RIS Atom XML MODS XML ODF XML Word XML

2012
Raseev, G. (2012). Laser fields at flat interfaces: I. Vector potential. EUROPEAN PHYSICAL JOURNAL D, 66(7), 179. Résumé: A model calculating the laser fields at a flat structureless surface taking into account the surface photoelectric effect is presented. The photon is p or transverse magnetic linearly polarized, continuous and its wave length is long, i.e. lambda(vac) >= 12.4 nm. The sharp rise of the electron density at the interface generates an atomic scale spatial dependence of the laser field. In real space and in the temporal gauge, the vector potential A of the laser is obtained as a solution of the classical Ampere-Maxwell and the material equations. The susceptibility is a product of the electron density of the material system with the surface and of the bulk tensor and non-local isotropic (TNLI) polarizability. The electron density is obtained quantum mechanically by solving the Schrodinger equation. The bulk TNLI polarizability including dispersion is calculated from a Drude-Lindhard-Kliewer model. In one dimension perpendicular to the surface the components A(x)(z,omega) and A(z)(z,omega) of the vector potential are solutions of the Ampere-Maxwell system of two coupled integro-differential equations. The model, called vector potential from the electron density-coupled integro-differential equations (VPED-CIDE), is used here to obtain the electron escape probability from the power density absorption, the reflectance, the electron density induced by the laser and Feibelman's parameters d(parallel to) and d(perpendicular to). Some preliminary results on aluminium surfaces are given here and in a companion paper the photoelectron spectra are calculated with results in agreement with the experiment. Permanent link \| Stocker citation: RTF PDF LaTeX \| Exporter enregistrement: BibTeX Endnote ISI RIS Atom XML MODS XML ODF XML Word XML
Raseev, G. (2012). Laser fields at flat interfaces: II. Plasmon resonances in aluminium photoelectron spectra. EUROPEAN PHYSICAL JOURNAL D, 66(7), 180. Résumé: Using the model derived in paper I [G. Raseev, Eur. Phys. J. D 66, 167 (2012)], this work presents calculations of the photoelectron spectrum (PES) of low index aluminium surfaces in the 10-30 eV region. The laser is p or transverse magnetic linearly polarized incident on a flat structureless surface and its fields are modeled in I using the vector potential in the temporal gauge. This model uses a tensor and nonlocal isotropic (TNLI) susceptibility and solves the classical Ampere-Maxwell equation through the use of the vector potential from the electron density-coupled integro-differential equations (VPED-CIDE). The PE cross sections are the squares of the PE transition moments calculated using the VPED-CIDE vector potential function of the penetration coordinate. The PES is obtained in a one step model using either the Fermi golden rule or the Weisskopf-Wigner (WW) expressions. The WW cross section PES compares favorably with the experimental angle and energy resolved photoelectron yield (AERPY) spectrum of Levinson et al. [Phys. Rev. Lett. 43, 952 (1979)], Levinson and Plummer [Phys. Rev. B 24, 628 (1981)] for Al(001) and of Barman et al. [Phys. Rev. B 58, R4285 (1998)], Barman [Curr. Sci. 88, 54 (2005)] for Al(111) surfaces. As in the experiment, our theoretical AERPY displays the multipole surface plasmon resonance at 11.32/12.75 eV for Al(001)/Al(111), mainly due to the surface contribution vertical bar vertical bar(2), the bulk plasmon minimum at 15 eV and the two single particle excitation resonances at about 16 and 22 eV. The nature of the plasmon resonances of the PES is analyzed using the reflectance, the electron density induced by the laser and Feibelman's parameter d(perpendicular to) all introduced in paper I. Permanent link \| Stocker citation: RTF PDF LaTeX \| Exporter enregistrement: BibTeX Endnote ISI RIS Atom XML MODS XML ODF XML Word XML
2010
Raseev, G., & Bejan, D. (2010). Multipole surface plasmon resonance of an aluminium surface. OPTICS COMMUNICATIONS, 283(20), 3976–3984. Résumé: The surface photoelectric effect and the surface plasmon resonances appear when a p/transverse magnetic polarized laser hits a gas-solid interface. We model this effect in the long wave length (LWL) domain (lambda(vac)>10 nm, (h) over cap omega<124 eV) by combining the Ampere-Maxwell equation, written in classical approximation, with the material equation for the susceptibility. The resulting model, called the vector potential from the electron density (VPED), calculates the susceptibility as a product of the bulk susceptibility and the electron density of the actual system. The bulk susceptibility is a sum of the bound electron scalar susceptibility taken from the experiment and of the conduction electron non-local isotropic susceptibility tensor in a jellium metal (Lindhard, 1954 [1]). The electron density is the square of the wave function solution of the Schrodinger equation. The analysis of observables, the reflectance R and the photoelectron yield Y as well as the induced charge density permits to identify and characterize the multipole surface plasmon resonance of Al(111) appearing at omega(m) similar to 0.8 omega(p), or 11-12 eV. (c) 2010 Elsevier B.V. All rights reserved. Permanent link \| Stocker citation: RTF PDF LaTeX \| Exporter enregistrement: BibTeX Endnote ISI RIS Atom XML MODS XML ODF XML Word XML

2012
Nimmrich, M., Kittelmann, M., Rahe, P., Harneit, W., Mayne, A. J., Dujardin, G., et al. (2012). Influence of charge transfer doping on the morphologies of C-60 islands on hydrogenated diamond C(100)-(2 x 1). PHYSICAL REVIEW B, 85(3), 035420. Résumé: The adsorption and island formation of C-60 fullerenes on the hydrogenated C(100)-(2 x 1):H diamond surface is studied using high-resolution noncontact atomic force microscopy in ultrahigh vacuum. At room temperature, C-60 fullerene molecules assemble into monolayer islands, exhibiting a hexagonally close-packed internal structure. Dewetting is observed when raising the substrate temperature above approximately 505 K, resulting in two-layer high islands. In contrast to the monolayer islands, these double-layer islands form extended wetting layers. This peculiar behavior is explained by an increased molecule-substrate binding energy in the case of double-layer islands, which originates from charge transfer doping. Only upon further increasing the substrate temperature to approximately 615 K, the wetting layer desorbs, corresponding to a binding energy of the charge transfer-stabilized film of 1.7 eV. Permanent link \| Stocker citation: RTF PDF LaTeX \| Exporter enregistrement: BibTeX Endnote ISI RIS Atom XML MODS XML ODF XML Word XML
2011
Rochdi, N., Liudvikouskaya, K., Descoins, M., Raissi, M., Coudreau, C., Lazzari, J. L., et al. (2011). Surface morphology and structure of ultra-thin magnesium oxide grown on (100) silicon by atomic layer deposition oxidation. THIN SOLID FILMS, 519(19), 6302–6306. Résumé: Ultra-thin magnesium oxide layers were elaborated by atomic layer deposition and oxidation process on silicon (100) starting from (2 x 1) thermally-reconstructed or hydrogen-terminated Si surfaces. Low-energy electron diffraction experiments show (2 x 3) and (3 x 3) reconstructions while depositing a magnesium monolayer on Si clean surfaces, and a 3-dimentional growth of the oxide as confirmed by ex-situ atomic force microscopy. For hydrogen-terminated or clean surfaces previously physisorbed by oxygen, uniform cobalt/magnesium-oxide/silicon stacks of layers are observed by transmission electron microscopy. Annealing above 150 degrees C leads to MgO dissolution and formation of an interfacial complex compound by inter-diffusion of Si and Co. (C) 2011 Elsevier B.V. All rights reserved. Permanent link \| Stocker citation: RTF PDF LaTeX \| Exporter enregistrement: BibTeX Endnote ISI RIS Atom XML MODS XML ODF XML Word XML
Wang, T., Boer-Duchemin, E., Tranvouez, E., Cartwright, R., Comtet, G., Dujardin, G., et al. (2011). Low voltage fabrication of sub-nanometer insulating layers on hydrogenated diamond. JOURNAL OF APPLIED PHYSICS, 110(3), 034311. Résumé: A new regime of electrochemical anodic oxidation with an atomic force microscope (AFM) is introduced for producing insulating layers on a hydrogenated diamond surface. In this new regime, when a low surface voltage (V(S) < +2 V) is applied to the sample, an insulating layer is created without any measurable change in the topography. Insulating layers created in this fashion are shown to preserve the high sub-surface conductance of hydrogenated diamond surfaces, contrary to the oxide layers accompanied by a topographic change, which destroy sub-surface conductance. (C) 2011 American Institute of Physics. [doi:10.1063/1.3615956] Permanent link \| Stocker citation: RTF PDF LaTeX \| Exporter enregistrement: BibTeX Endnote ISI RIS Atom XML MODS XML ODF XML Word XML
2010
Boer-Duchemin, E., Tranvouez, E., & Dujardin, G. (2010). The interaction of an atomic force microscope tip with a nano-object: a model for determining the lateral force. NANOTECHNOLOGY, 21(45), 455704. Résumé: A calculation of the lateral force interaction between an atomic force microscope (AFM) tip and a nano-object on a substrate is presented. In particular, the case where the AFM tip is used to manipulate the nano-object is considered; i.e., the tip is displaced across the nano-object with the feedback off. The Hamaker equations are used to calculate the force when the tip and sample are not in contact and the Johnson, Kendall and Roberts (JKR) or Derjaguin, Muller and Toporov (DMT) formalisms are used for the contact force. The effect of the material parameters, the choice of contact theory and the shape of the nano-object on the resulting lateral forces are explored. The calculation is applied to an experimental system consisting of a cadmium selenide nanorod on graphite. Permanent link \| Stocker citation: RTF PDF LaTeX \| Exporter enregistrement: BibTeX Endnote ISI RIS Atom XML MODS XML ODF XML Word XML
Nimmrich, M., Kittelmann, M., Rahe, P., Mayne, A. J., Dujardin, G., von Schmidsfeld, A., et al. (2010). Atomic-resolution imaging of clean and hydrogen-terminated C(100)-(2x1) diamond surfaces using noncontact AFM. PHYSICAL REVIEW B, 81(20), 201403. Résumé: High-purity, type IIa diamond is investigated by noncontact atomic force microscopy (NC-AFM). We present atomic-resolution images of both the electrically conducting hydrogen-terminated C(100)-(2 x 1) : H surface and the insulating C(100)-(2 x 1) surface. For the hydrogen-terminated surface, a nearly square unit cell is imaged. In contrast to previous scanning tunneling microscopy experiments, NC-AFM imaging allows both hydrogen atoms within the unit cell to be resolved individually, indicating a symmetric dimer alignment. Upon removing the surface hydrogen, the diamond sample becomes insulating. We present atomic-resolution images, revealing individual C-C dimers. Our results provide real-space experimental evidence for a (2 x 1) dimer reconstruction of the truly insulating C(100) surface. Permanent link \| Stocker citation: RTF PDF LaTeX \| Exporter enregistrement: BibTeX Endnote ISI RIS Atom XML MODS XML ODF XML Word XML
2009
Tranvouez, E., Boer-Duchemin, E., Mayne, A. J., Vanderbruggen, T., Scheele, M., Cartwright, R., et al. (2009). Influence of morphology on the conductance of single-crystal diamond surfaces measured by atomic force microscopy. JOURNAL OF APPLIED PHYSICS, 106(5), 054301. Résumé: A detailed atomic force microscopy (AFM) study of the conductance of hydrogenated single-crystal diamond (100) surfaces over submicron length scales is presented. The hydrogenation process was found to influence the surface morphology by reducing surface roughness, with the subsequent appearance of small triangular structures (with side lengths of 200 nm). Conducting AFM measurements revealed variations in the current and resistance that were related to the topography. Possible explanations include surface inhomogeneity of the electronic structure or variations in the contact resistance due to the surface roughness. Permanent link \| Stocker citation: RTF PDF LaTeX \| Exporter enregistrement: BibTeX Endnote ISI RIS Atom XML MODS XML ODF XML Word XML
Tranvouez, E., Orieux, A., Boer-Duchemin, E., Devillers, C. H., Huc, V., Comtet, G., et al. (2009). Manipulation of cadmium selenide nanorods with an atomic force microscope. NANOTECHNOLOGY, 20(16), 165304. Résumé: We have used an atomic force microscope (AFM) to manipulate and study ligand-capped cadmium selenide nanorods deposited on highly oriented pyrolitic graphite (HOPG). The AFM tip was used to manipulate (i.e., translate and rotate) the nanorods by applying a force perpendicular to the nanorod axis. The manipulation result was shown to depend on the point of impact of the AFM tip with the nanorod and whether the nanorod had been manipulated previously. Forces applied parallel to the nanorod axis, however, did not give rise to manipulation. These results are interpreted by considering the atomic-scale interactions of the HOPG substrate with the organic ligands surrounding the nanorods. The vertical deflection of the cantilever was recorded during manipulation and was combined with a model in order to estimate the value of the horizontal force between the tip and nanorod during manipulation. This horizontal force is estimated to be on the order of a few tens of nN. Permanent link \| Stocker citation: RTF PDF LaTeX \| Exporter enregistrement: BibTeX Endnote ISI RIS Atom XML MODS XML ODF XML Word XML

Institut des Sciences Moléculaires d'Orsay - UMR 8214

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36. Séminaire de Karine Steenkeste (18 juin 2013)

39. Séminaire d'Alexandre Giuliani (28 mai 2013)

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