Partenaires
Menu
- Présentation
- Équipes scientifiques
- Dynamiques et Interactions : Rayonnement, Atomes, Molécules (DIRAM)
- Publications
- Offres de stage, thèses, post-docs
- Dynamique ultra-rapide électron-noyaux sondée par photoionisation des molécules
- Photoionisation des ions atomiques et moléculaires
- Propriétés spectrales et temporelles des lasers XUV générés par plasma
- Cohérence et contrôle de la dynamique quantique
- Processus moléculaires contrôlés par des champs laser intenses
- Capteurs et métrologie quantiques
- Femtochimie en phase gazeuse
- Science attoseconde et attochimie
- Nanomédecine et Biophotonique (NanoBio)
- Publications
- Offres de stage, thèse, postdoc
- Nanoparticules de type "cage" pour lutter contre des maladies sévères
- Nanoparticules pour les radiothérapies innovantes
- Imagerie de fluorescence à l’échelle nanoscopique pour la biologie
- Microfluidique : étude du comportement des fluides à l’échelle microscopique, contrôle et manipulation des microgouttes dans des microcanaux, développement d’outils d’analyse spectroscopique innovants et sensibles
- Nanophysique et Surfaces (Nanophys)
- Structure et dynamique des systèmes complexes isolés photoexcités (SYSIPHE)
- Surfaces, Interfaces, Molecules & 2D Materials (SIM2D)
- Publications
- Offres de stages, thèses, post-docs
- Diffraction d’atomes rapides
- Chimie de surface & électrons lents, 0-50 eV
- New 2D Materials : Silicene, Phosphorene, Bismuthene
- Nano-architecture moléculaires et surfaces nanostructurées
- Graphène : molécules et transport
- Systèmes Fortement Corrélés et Matériaux Quantiques
- Interfaces, nanostructures et Dynamiques des Interactions
- Matériaux à grand gap : Diamant, Carbure de Silicium et Oxydes
- Calculs de structures électriques et dynamique quantique moléculaire sur des surfaces métalliques
- Systèmes Moléculaires, Astrophysique et Environnement (SYSTEMAE)
- Dynamiques et Interactions : Rayonnement, Atomes, Molécules (DIRAM)
- Services techniques
- Administration
- Enseignement
- Stages thèses Post-docs
- Séminaires
- Production Scientifique
- Plates-formes
- Vulgarisation
jeudi 23 janvier
Mise à jour
mercredi 24 juillet 2024
Accueil > Équipes scientifiques > Nanophysique et Surfaces (Nanophys) > Publications > 2012
2012
Brevets |
|
Hocine Khemliche, P. R., Patrick Rousseau. (2012). Device and method for characterizing surfaces.
Résumé: A method of characterizing surfaces comprises the steps of:
directing a beam (2) of neutral atoms or molecules on a surface (3) for characterizing; and detecting in position-sensitive manner the neutral atoms or molecules of said beam that have been diffused forwards by said surface (3) for characterizing; the properties of said beam (2) being selected in such a manner that at least some of said neutral atoms or molecules that are diffused forwards are diffractive by said surface for characterizing. A device for implementing such a method comprises means (1) for generating such a beam (2) of neutral atoms or molecules and position-sensitive detector means (4) for detecting the neutral atoms or molecules that are diffused forwards by said surface (3) for characterizing. date de priorité: 7 juil. 2006 EP2044423A2, US20090250600, WO2008003865A2, WO2008003865A3 |
|
Peer-reviewed Publications |
|
|
Borisov, A. G., Echenique, P. M., & Kazansky, A. K. (2012). Attostreaking with metallic nano-objects. New J. Phys., 14, 023036.
Résumé: The application of atto-second streaking spectroscopy (ASS) to direct time-domain studies of the plasmonic excitations in metallic nano-objects is addressed theoretically. The streaking spectrograms for a rectangular gold nano-antenna and spherical gold clusters are obtained within strong field approximation using classical electron trajectory calculations. The results reported here for spherical clusters are also representative of spherical nano-shells. This study demonstrates that ASS allows for detailed characterization of plasmonic modes, including near-field enhancement, frequency and decay rate. The role of the inhomogeneity of the induced electric fields is also demonstrated.
|
|
|
Boudrioua, O., Yang, H., Sonnet, P., Stauffer, L., Mayne, A. J., Comtet, G., Dujardin, G., Kuk, Y., Nagarajan, S., Gourdon, A., & Duverger, E. (2012). Large organic molecule chemisorption on the SiC(0001) surface. Phys. Rev. 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.
|
|
|
Bulard, E., Fontaine-Aupart, M. - P., Dubost, H., Zheng, W., Bellon-Fontaine, M. - N., Herry, J. - M., & Bourguignon, B. (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.
|
|
|
Bulard, E., Fontaine-Aupart, M. - P., Dubost, H., Zheng, W., Herry, J. - M., Bellon-Fontaine, M. - N., Briandet, R., & Bourguignon, B. (2012). The Effect of Bacterial Adhesion on Grafted Chains Revealed by the Non-Invasive Sum Frequency Generation Spectroscopy. Spectrosc.-Int. J., 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.
|
|
|
Cassimi, A., Ikeda, T., Maunoury, L., Zhou, C. L., Guillous, S., Mery, A., Lebius, H., Benyagoub, A., Grygiel, C., Khemliche, H., Roncin, P., Merabet, H., & Tanis, J. A. (2012). Dynamics of charge evolution in glass capillaries for 230-keV Xe23+ ions. Phys. Rev. A, 86(6), 062902.
Résumé: We have measured the transmission of 230-keV (10-keV/q) Xe23+ ions through insulating tapered glass capillaries of microscopic dimensions. The dynamics of charging and discharging processes have been investigated, evidencing an unexpected slow alignment of the beam along the capillary axis. Oscillations of the exiting beam position have been observed during the charging process associated to the formation of charge patches on the capillary inner walls. The emerging ions are guided with a characteristic guiding angle falling on a universal curve proposed for PET polymer nanocapillaries. This result, very similar to the channeling process, is somewhat surprising in view of the significant differences between the straight nanocapillary polymer foils and the tapered microscopic single glass capillary used here. The transmitted ions show no evidence of energy loss or charge changing except for the production of a small neutral fraction that was determined to be due to ions that had become neutralized to form atoms rather than due to photon emission. These results thus test and confirm the validity of transmission and guiding and provide insight into the dynamics of higher-energy ions than have been previously studied in this regard, allowing a determination of the maximum energy for which the guiding process might occur.
|
|
|
Esteban, R., Borisov, A. G., Nordlander, P., & Aizpurua, J. (2012). Bridging quantum and classical plasmonics with a quantum-corrected model. Nat. Commun., 3, 825.
Résumé: Electromagnetic coupling between plasmonic resonances in metallic nanoparticles allows for engineering of the optical response and generation of strong localized near-fields. Classical electrodynamics fails to describe this coupling across sub-nanometer gaps, where quantum effects become important owing to non-local screening and the spill-out of electrons. However, full quantum simulations are not presently feasible for realistically sized systems. Here we present a novel approach, the quantum-corrected model (QCM), that incorporates quantum-mechanical effects within a classical electrodynamic framework. The QCM approach models the junction between adjacent nanoparticles by means of a local dielectric response that includes electron tunnelling and tunnelling resistivity at the gap and can be integrated within a classical electrodynamical description of large and complex structures. The QCM predicts optical properties in excellent agreement with fully quantum mechanical calculations for small interacting systems, opening a new venue for addressing quantum effects in realistic plasmonic systems.
|
|
|
Fan, C., Poumellec, B., Zeng, H., Desmarchelier, R., Bourguignon, B., Chen, G., & Lancry, M. (2012). Gold Nanoparticles Reshaped by Ultrafast Laser Irradiation Inside a Silica-Based Glass, Studied Through Optical Properties. J. Phys. Chem. 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.
|
|
|
Gauyacq, J. - P., Lorente, N., & Dutilh Novaes, F. (2012). Excitation of local magnetic moments by tunneling electrons. Prog. Surf. Sci., 87(5-8), 63–107.
Résumé: The advent of milli-kelvin scanning tunneling microscopes (STM) with inbuilt magnetic fields has opened access to the study of magnetic phenomena with atomic resolution at surfaces. In the case of single atoms adsorbed on a surface, the existence of different magnetic energy levels localized on the adsorbate is due to the breaking of the rotational invariance of the adsorbate spin by the interaction with its environment, leading to energy terms in the meV range. These structures were revealed by STM experiments in IBM Almaden in the early 2000s for atomic adsorbates on CuN surfaces. The experiments consisted in the study of the changes in conductance caused by inelastic tunneling of electrons (IETS, inelastic electron tunneling spectroscopy). Manganese and Iron adatoms were shown to have different magnetic anisotropies induced by the substrate. More experiments by other groups followed up, showing that magnetic excitations could be detected in a variety of systems: e.g. complex organic molecules showed that their magnetic anisotropy was dependent on the molecular environment, piles of magnetic molecules showed that they interact via intermolecular exchange interaction, spin waves were excited on ferromagnetic surfaces and in Mn chains, and magnetic impurities have been analyzed on semiconductors. These experiments brought up some intriguing questions: the efficiency of magnetic excitations was very high, the excitations could or could not involve spin flip of the exciting electron and singular-like behavior was sometimes found at the excitation thresholds. These facts called for extended theoretical analysis: perturbation theories, sudden-approximation approaches and a strong coupling scheme successfully explained most of the magnetic inelastic processes. In addition, many-body approaches were also used to decipher the interplay between inelastic processes and the Kondo effect. Spin torque transfer has been shown to be effective in changing spin orientations of an adsorbate in theoretical works, and soon after it was shown experimentally. More recently, the previously mentioned strong coupling approach was extended to treat the excitation of spin waves in atomic chains and the ubiquitous role of electron-hole pair creation in de-exciting spins on surfaces has been analyzed. This review article expounds these works, presenting the theoretical approach by the authors while trying to thoroughly review parallel theoretical and experimental works. (C) 2012 Elsevier Ltd. All rights reserved.
|
|
|
Korytar, R., Lorente, N., & Gauyacq, J. - P. (2012). Many-body effects in magnetic inelastic electron tunneling spectroscopy. Phys. Rev. B, 85(12), 125434.
Résumé: Magnetic inelastic electron tunneling spectroscopy (IETS) shows sharp increases in conductance when a new conductance channel associated with a change in magnetic structure is open. Typically, the magnetic moment carried by an adsorbate can be changed by collision with a tunneling electron; in this process the spin of the electron can flip or not. A previous one-electron theory [Phys. Rev. Lett. 103, 176601 (2009)] successfully explained both the conductance thresholds and the magnitude of the conductance variation. The elastic spin flip of conduction electrons by a magnetic impurity leads to the well-known Kondo effect. In the present work, we compare the theoretical predictions for inelastic magnetic tunneling obtained with a one-electron approach and with a many-body theory including Kondo-like phenomena. We apply our theories to a singlet-triplet transition model system that contains most of the characteristics revealed in magnetic IETS. We use two self-consistent treatments (noncrossing approximation and self-consistent ladder approximation). We show that, although the one-electron limit is properly recovered, new intrinsic many-body features appear. In particular, sharp peaks appear close to the inelastic thresholds; these are not localized exactly at thresholds and could influence the determination of magnetic structures from IETS experiments. Analysis of the evolution with temperature reveals that these many-body features involve an energy scale different from that of the usual Kondo peaks. Indeed, the many-body features perdure at temperatures much larger than the one given by the Kondo energy scale of the system.
|
|
|
Koval, N. E., Sanchez-Portal, D., Borisov, A. G., & Diez Muino, R. (2012). Dynamic screening of a localized hole during photoemission from a metal cluster. Nanoscale Res. Lett., 7(1), 1–9.
Résumé: Recent advances in attosecond spectroscopy techniques have fueled the interest in the theoretical description of electronic processes taking place in the subfemtosecond time scale. Here we study the coupled dynamic screening of a localized hole and a photoelectron emitted from a metal cluster using a semi-classical model. Electron density dynamics in the cluster is calculated with time-dependent density functional theory, and the motion of the photoemitted electron is described classically. We show that the dynamic screening of the hole by the cluster electrons affects the motion of the photoemitted electron. At the very beginning of its trajectory, the photoemitted electron interacts with the cluster electrons that pile up to screen the hole. Within our model, this gives rise to a significant reduction of the energy lost by the photoelectron. Thus, this is a velocity-dependent effect that should be accounted for when calculating the average losses suffered by photoemitted electrons in metals.
|
|
|
Lalmi, B., Khemliche, H., Momeni, A., Soulisse, P., & Roncin, P. (2012). High resolution imaging of superficial mosaicity in single crystals using grazing incidence fast atom diffraction. J. Phys. Condens. Matter., 24(44), 442002.
Résumé: A new table top technique is used to simultaneously analyze the local morphology of crystalline surfaces as well as the misalignment of large scale domains at the topmost surface layer. The approach is based on fast atom diffraction at grazing incidence (GIFAD); the diffraction pattern yields the structural characteristics and the topology of the surface electronic density with atomic resolution. If superficial mosaicity is present, diffraction patterns arising from each mosaic domain can be distinguished, providing high sensitivity to the properties of each of the domains. Taking NaCl(001) as an example, we observe a discrete tilt angle distribution of the mosaic domains following an arithmetic progression with a 0.025 degrees +/- 0.005 degrees difference; a twist mosaic angle of 0.09 degrees +/- 0.01 degrees is also observed.
|
|
|
Lancry, M., Poumellec, B., Desmarchelier, R., & Bourguignon, B. (2012). Oriented creation of anisotropic defects by IR femtosecond laser scanning in silica. Opt. Mater. 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
|
|
|
Marinica, D. C., Kazansky, A. K., Nordlander, P., Aizpurua, J., & Borisov, A. G. (2012). Quantum Plasmonics: Nonlinear Effects in the Field Enhancement of a Plasmonic Nanoparticle Dimer. Nano Lett., 12(3), 1333–1339.
Résumé: A fully quantum mechanical investigation using time-dependent density functional theory reveals that the field enhancement in a coupled nanoparticle dimer can be strongly affected by nonlinear effects. We show that both classical as well as linear quantum mechanical descriptions of the system fail even for moderate incident light intensities. An interparticle current resulting from the strong field photo emission tends to neutralize the plasmon-induced surface charge densities on the opposite sides of the nanoparticle junction. Thus, the coupling between the two nanoparticles and the field enhancement is reduced as compared to linear theory. A substantial nonlinear effect is revealed already at incident powers of 10(9) W/cm(2) for interparticle separation distances as large as 1 nm and down to the touching limit.
|
|
|
Nimmrich, M., Kittelmann, M., Rahe, P., Harneit, W., Mayne, A. J., Dujardin, G., & Kuhnle, A. (2012). Influence of charge transfer doping on the morphologies of C-60 islands on hydrogenated diamond C(100)-(2 x 1). Phys. Rev. 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.
|
|
|
Raseev, G. (2012). Laser fields at flat interfaces: I. Vector potential. Eur. Phys. J. 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.
|
|
|
Raseev, G. (2012). Laser fields at flat interfaces: II. Plasmon resonances in aluminium photoelectron spectra. Eur. Phys. J. 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 <psi(f)vertical bar p . A vertical bar psi(i)>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.
|
|
|
Savage, K. J., Hawkeye, M. M., Esteban, R., Borisov, A. G., Aizpurua, J., & Baumberg, J. J. (2012). Revealing the quantum regime in tunnelling plasmonics. Nature, 491(7425), 574–577.
Résumé: When two metal nanostructures are placed nanometres apart, their optically driven free electrons couple electrically across the gap. The resulting plasmons have enhanced optical fields of a specific colour tightly confined inside the gap. Many emerging nanophotonic technologies depend on the careful control of this plasmonic coupling, including optical nanoantennas for high-sensitivity chemical and biological sensors(1), nanoscale control of active devices(2-4), and improved photovoltaic devices(5). But for subnanometre gaps, coherent quantum tunnelling becomes possible and the system enters a regime of extreme non-locality in which previous classical treatments(6-14) fail. Electron correlations across the gap that are driven by quantum tunnelling require a new description of non-local transport, which is crucial in nanoscale optoelectronics and single-molecule electronics. Here, by simultaneously measuring both the electrical and optical properties of two gold nanostructures with controllable subnanometre separation, we reveal the quantum regime of tunnelling plasmonics in unprecedented detail. All observed phenomena are in good agreement with recent quantum-based models of plasmonic systems(15), which eliminate the singularities predicted by classical theories. These findings imply that tunnelling establishes a quantum limit for plasmonic field confinement of about 10(-8) lambda(3) for visible light (of wavelength lambda). Our work thus prompts new theoretical and experimental investigations into quantum-domain plasmonic systems, and will affect the future of nanoplasmonic device engineering and nanoscale photochemistry.
|
|
|
Schubert, K., Damm, A., Eremeev, S. V., Marks, M., Shibuta, M., Berthold, W., Guedde, J., Borisov, A. G., Tsirkin, S. S., Chulkov, E. V., & Hoefer, U. (2012). Momentum-resolved electron dynamics of image-potential states on Cu and Ag surfaces. Phys. Rev. B, 85(20), 205431.
Résumé: The dependence of the inelastic lifetime of electrons in the first n = 1 image-potential state of clean and rare-gas covered Ag(111), Cu(111), and Cu(100) surfaces on their momentum parallel to the surface has been studied experimentally by means of time-and angle-resolved two-photon photoemission spectroscopy (2PPE) and theoretically by calculations based on the many-body theory within the self-energy formalism. Similar to the previously studied clean Cu(100) surface, the theoretical results are in excellent agreement with the experiment findings for Cu(111). For Ag(111), the theory overestimates the decay rate and its momentum dependence, which is attributed to the neglect of surface plasmon excitations. With increasing parallel momentum, the n = 1 state shifts out of the projected bulk band gap on both surfaces and turns into an image-potential resonance. This opens an additional decay channel by resonant electron transfer into the bulk, which is theoretically treated by the application of the wave packet propagation approach. The expected stronger increase of the decay rate upon crossing the edge of the band gap, however, is not observed in the experiment. The decoupling of the image-potential states from the metal surface upon adsorption of rare-gas layers results in a decrease of the decay rate as well as of its momentum dependence by a similar factor, which can be successfully explained by the change of interband and intraband contributions to the total decay rate.
|
|
|
Yang, H., Boudrioua, O., Mayne, A. J., Comtet, G., Dujardin, G., Kuk, Y., Sonnet, P., Stauffer, L., Nagarajan, S., & Gourdon, A. (2012). The paradox of an insulating contact between a chemisorbed molecule and a wide band gap semiconductor surface. Phys. Chem. Chem. Phys., 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.
|
|
|
Zugarramurdi, A., & Borisov, A. G. (2012). Transition from fast to slow atom diffraction. Phys. Rev. A, 86(6), 062903.
Résumé: For energetic atomic beams grazingly incident at a surface along low-index directions, the fast motion of the projectile in the surface plane and the slow motion in the direction perpendicular to the surface appear nearly decoupled. Fast-atom diffraction (FAD) experiments reveal two-dimensional (2D) diffraction patterns associated with exchange of the reciprocal vector perpendicular to the low-index direction of fast motion. These results are usually interpreted within the axial-channeling approximation, where the effective 2D potential experienced by the projectile is set as an average of the 3D surface potential along the atomic strings forming the channel. In this work, using the example of grazing scattering of He atoms at a LiF(001) surface, we address theoretically the range of validity of the axial-channeling approximation. Full quantum wave-packet-propagation calculations are used to study the transition from the 2D (fast atom) to the 3D diffraction pattern characteristic for low-energy atomic and molecular projectiles scattered from surfaces. Along with exact calculations, a semianalytical perturbative treatment based on the Lippmann-Schwinger equation allows an explanation of why the diffraction processes involving the exchange of reciprocal-lattice vectors along the fast-motion direction are exponentially small in typical FAD conditions.
|
|
|
Zugarramurdi, A., Zabala, N., Silkin, V. M., Chulkov, E. V., & Borisov, A. G. (2012). Quantum-well states with image state character for Pb overlayers on Cu(111). Phys. Rev. B, 86(7), 075434.
Résumé: We study theoretically the quantum well states (QWSs) localized in Pb overlayers on Cu(111) surface. Particular emphasis is given to the states with energies close to the vacuum level. Inclusion of the long-range image potential tail into the model potential description of the system allows us to show the effect of hybridization between QWSs and image potential states (ISs). The particle-in-a-box energy sequence characteristic for QWSs evolves into the Rydberg series converging towards the vacuum level. The electron density of the corresponding states is partially moved from inside the metal overlayer into the vacuum. The decay rates due to the inelastic electron-electron scattering decrease with increasing energy, opposite to “conventional” QWSs and similar to the ISs. Many-body and wave packet propagation calculations of the inelastic decay rates are supplemented by simple analysis based on the phase accumulation model and wave-function penetration approximation. This allows an analytical description of the dependence of the QWS/ISs hybridization on different parameters and, in particular, on the overlayer thickness.
|
|