Peer-reviewed Publications |
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. Phys. Rev. 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.
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De Padova, P., Leandri, C., Vizzini, S., Quaresima, C., Perfetti, P., Olivieri, B., Oughaddou, H., Aufray, B., & Le Lay, G. (2008). Burning match oxidation process of silicon nanowires screened at the atomic scale. NANO LETTERS, 8(8), 2299–2304.
Résumé: Silicon oxide nanowires hold great promise for functional nanoscale electronics. Here, we investigate the oxidation of straight, massively parallel, metallic Si nanowires. We show that the oxidation process starts at the Si NW terminations and develops like a burning match. While the spectroscopic signatures on the virgin, metallic part, are unaltered we identify four new oxidation states on the oxidized part, which show a gap opening, thus revealing the formation of a transverse internal nanojunction.
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Lastapis, M., Martin, M., Riedel, D., & Dujardin, G. (2008). Role of the dopant in silicon on the dynamics of a single adsorbed molecule. Phys. Rev. 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.
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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). J. Chem. Phys., 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.
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Oughaddou, H., Aufray, B., Biberian, J. P., Ealet, B., Le Lay, G., Treglia, G., Kara, A., & Rahman, T. S. (2008). Self-organization of Ge tetramers on Ag(001) surface: A 2D realization of unusual substrate mediated interactions. SURFACE SCIENCE, 602(2), 506–510.
Résumé: Scanning tunneling microscopy (STM) images recorded during dissolution of a half-monolayer Ge on a Ag(0 0 1) show that it proceeds by the disappearance of tetramer entities. Moreover, they reveal that the successive slowing down in the kinetics, observed during this dissolution, correspond to the formation of ordered 2D arrangements of tetramer vacancies. A lattice gas analysis of the latter predicts a very unusual sequence of pair interactions between these vacancies, probably mediated by the substrate. (C) 2007 Elsevier B.V. All rights reserved.
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Yang, H., Baffou, G., Mayne, A. J., Comtet, G., Dujardin, G., & Kuk, Y. (2008). Topology and electron scattering properties of the electronic interfaces in epitaxial graphene probed by resonant tunneling spectroscopy. Phys. Rev. B, 78(4), 041408.
Résumé: Z-V scanning tunneling spectroscopy is used to probe the topology and electron scattering properties of the electronic interfaces of monolayer and bilayer graphenes, expitaxially grown on SiC(0001). The dZ/dV spectra validate existing calculations of the interface topology and provide evidence for new electron scattering properties due to changes in the electronic character of the bonding. Two sharp boundaries are observed: between the vacuum and the graphene pi state lying above the graphene atom plane and a subsurface barrier between the carbon-rich layer and the bulk SiC.
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Chapitres de Livres |
Mayne, A. J., & Dujardin, G. (2008). STM manipulation and Dynamics. In Dynamics (Vol. 3, pp. 681–759). Handbook of Surface Science. E. Hasselbrink and B.I. Lundqvist.
Résumé: This volume of the Handbook of Surface Science covers all aspects of the dynamics of surface processes. Two dozen world leading experts in this field address the subjects of energy exchange in gas atoms, surface collisions, the rules governing dissociative adsorption on surfaces, the formation of nanostructures on surfaces by self-assembly, and the study of surface phenomena using ultra-fast lasers. The chapters are written for both newcomers to the field as well as researchers.
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