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1. Low-frequency Raman signature of Ag-intercalated few-layer MoS$_2$

Author

Sheremetyeva, Natalya, Niedzielski, Drake, Tristant, Damien, Liang, Liangbo, Kerstetter, Lauren E., Mohney, Suzanne E., and Meunier, Vincent

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics
Abstract

Density functional theory based calculations and experimental analysis on a limited number of real samples are performed to study how the presence of silver intercalated in the van der Waals gap of few-layer MoS$_2$ affects the low-frequency Raman active modes of this material. Silver is found to predominantly affect the breathing-like and shear-like vibrational modes of MoS$_2$. These modes correspond to quasi-rigid movements of each individual layer with a restoring force (and, in turn, frequency) that is determined by modulations in the weak interlayer interactions. Noticeable red-shifts with increasing Ag concentration are found for all low-frequency modes. This finding indicates the potential for low-frequency vibrations as useful gauges for practical determination of silver concentration using low-frequency Raman spectroscopy. This work also describes a semi-classical linear chain model that allows to extrapolate results to a large number of layers. Further, first-principles calculations show how Raman spectroscopy can be used to characterize the quality of the two-dimensional interface between MoS$_2$ and a silver substrate.

Published
2021
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2. Partial Charge Transfer and Absence of Induced Magnetization in EuS(111)/Bi$_2$Se$_3$ Heterostructures

Author

Tristant, Damien, Vekhter, Ilya, Meunier, Vincent, and Shelton, William

Subjects
Condensed Matter - Materials Science, Condensed Matter - Other Condensed Matter
Abstract

Heterostructures made from topological and magnetic insulators promise to form excellent platforms for new electronic and spintronic functionalities mediated by interfacial effects. We report the results of a first-principles density functional theory study of the geometric, electronic structure, and magnetic properties of EuS(111)/Bi$_2$Se$_3$ interface, including van der Waals and relativistic spin-orbit effects. In contrast to previous theoretical studies, we find no appreciable magnetic anisotropy in such a heterostructure. We also do not see additional induced magnetization at the interface or the magnetic proximity effect on the topological states. This is due to the localized nature of Eu moments, and because of a partial charge transfer of $\sim$0.5 electron from Eu to Se. The formation of the surface dipole shifts the Dirac cone about 0.4~eV below the chemical potential, and the associated electrostatic screening moves the topological state from the first to the second quintuple layer of Bi$_2$Se$_3$., Comment: 10 pages, 6 figures

Published
2021
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3. Observation of sixfold degenerate fermions in PdSb$_2$

Author

Yáng, Xiàn, Cochran, Tyler A., Chapai, Ramakanta, Tristant, Damien, Yin, Jia-Xin, Belopolski, Ilya, Chéng, Zǐjiā, Multer, Daniel, Zhang, Songtian S., Shumiya, Nana, Litskevich, Maksim, Jiang, Yuxiao, Chang, Guoqing, Zhang, Qi, Vekhter, Ilya, Shelton, William A., Jin, Rongying, Xu, Su-Yang, and Hasan, M. Zahid

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics, Condensed Matter - Materials Science, Condensed Matter - Strongly Correlated Electrons
Abstract

Three types of fermions have been extensively studied in topological quantum materials: Dirac, Weyl, and Majorana fermions. Beyond the fundamental fermions in high energy physics, exotic fermions are allowed in condensed matter systems residing in three-, six- or eightfold degenerate band crossings. Here, we use angle-resolved photoemission spectroscopy to directly visualize three-doubly-degenerate bands in PdSb$_2$. The ultrahigh energy resolution we are able to achieve allows for the confirmation of all the sixfold degenerate bands at the R point, in remarkable consistency with first-principles calculations. Moreover, we find that this sixfold degenerate crossing has quadratic dispersion as predicted by theory. Finally, we compare sixfold degenerate fermions with previously confirmed fermions to demonstrate the importance of this work: our study indicates a topological fermion beyond the constraints of high energy physics.

Published
2020
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5. Some Electronic Properties of Metals through q-Deformed Algebras

Author

Tristant, Damien and Brito, Francisco A.

Subjects
Condensed Matter - Statistical Mechanics, High Energy Physics - Theory
Abstract

We study the thermodynamics of metals by applying q-deformed algebras. We shall mainly focus our attention on q-deformed Sommerfeld parameter as a function of q-deformed electronic specific heat. The results revealed that q-deformation acts as a factor of disorder or impurity, modifying the characteristics of a crystalline structure and thereby controlling the number of electrons per unit volume., Comment: 18 pages, 7 figures, 1 table, Latex. Version to appear in Physica A

Published
2013
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12. Observation of sixfold degenerate fermions in PdSb2

Author

Yáng, Xiàn, primary, Cochran, Tyler A., additional, Chapai, Ramakanta, additional, Tristant, Damien, additional, Yin, Jia-Xin, additional, Belopolski, Ilya, additional, Chéng, Zĭjiā, additional, Multer, Daniel, additional, Zhang, Songtian S., additional, Shumiya, Nana, additional, Litskevich, Maksim, additional, Jiang, Yuxiao, additional, Chang, Guoqing, additional, Zhang, Qi, additional, Vekhter, Ilya, additional, Shelton, William A., additional, Jin, Rongying, additional, Xu, Su-Yang, additional, and Hasan, M. Zahid, additional

Published
2020
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13. Optical signatures of bulk and solutions of KC8 and KC24.

Author

Tristant, Damien, Yu Wang, Gerber, Iann, Monthioux, Marc, Pénicaud, Alain, and Puech, Pascal

Subjects
*GRAPHITE intercalation compounds, *PYRROLIDINONES, *EXCITATION energy (In situ microanalysis), *FERMI level, *RAMAN scattering
Abstract

We first performed an analysis of the shape of the Raman features of potassium-intercalated graphite at stage 1 (KC8 GIC) and 2 (KC24 GIC), respectively. By varying the excitation energy from ultraviolet to infrared, we observed a sign change of the Fano coupling factor below and above the optical transition related to the shift of the Fermi level which was determined from first principle calculations. This behavior is explained by a sign change in the Raman scattering amplitude of the electronic continuum. The GICs were then dissolved in two different solvents (N-Methyl-2-pyrrolidone and tetrahydrofuran), and the absorbance of the graphenide solutions obtained was measured in the UV range. Two peaks were observed which correspond to the maximum of the computed imaginary part of the optical index. [ABSTRACT FROM AUTHOR]

Published
2015
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14. Optical signatures of bulk and solutions of KC8 and KC24.

Author

Tristant, Damien, Yu Wang, Gerber, Iann, Monthioux, Marc, Pénicaud, Alain, and Puech, Pascal

Subjects
GRAPHITE intercalation compounds, PYRROLIDINONES, EXCITATION energy (In situ microanalysis), FERMI level, RAMAN scattering
Abstract

We first performed an analysis of the shape of the Raman features of potassium-intercalated graphite at stage 1 (KC8 GIC) and 2 (KC24 GIC), respectively. By varying the excitation energy from ultraviolet to infrared, we observed a sign change of the Fano coupling factor below and above the optical transition related to the shift of the Fermi level which was determined from first principle calculations. This behavior is explained by a sign change in the Raman scattering amplitude of the electronic continuum. The GICs were then dissolved in two different solvents (N-Methyl-2-pyrrolidone and tetrahydrofuran), and the absorbance of the graphenide solutions obtained was measured in the UV range. Two peaks were observed which correspond to the maximum of the computed imaginary part of the optical index. [ABSTRACT FROM AUTHOR]

Published
2015
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17. An unexpected organometallic intermediate in surface-confined Ullmann coupling

Author

Galeotti, Gianluca, Di Giovannantonio, Marco, Cupo, Andrew, Xing, Sarah, Lipton-Duffin, Josh, Ebrahimi, Maryam, Vasseur, Guillaume, Kierren, Bertrand, Fagot-Revurat, Yannick, Tristant, Damien, Meunier, Vincent, Perepichka, Dmitrii F., Rosei, Federico, Contini, Giorgio, Galeotti, Gianluca, Di Giovannantonio, Marco, Cupo, Andrew, Xing, Sarah, Lipton-Duffin, Josh, Ebrahimi, Maryam, Vasseur, Guillaume, Kierren, Bertrand, Fagot-Revurat, Yannick, Tristant, Damien, Meunier, Vincent, Perepichka, Dmitrii F., Rosei, Federico, and Contini, Giorgio

Abstract

Ullmann coupling or, more generally, dehalogenative aryl-aryl coupling, is one of the most widely exploited chemical reactions to obtain one- and two-dimensional polymers on metal surfaces. It is generally described as a two-step reaction: (i) dehalogenation, resulting in the formation of a stable intermediate organometallic phase and subsequent (ii) C-C coupling. The topology of the resulting polymer depends on the number and positions of the halogen atoms in the haloaromatic precursor, although its orientation and order are determined by the structure of the intermediate phase. Hitherto, only one intermediate structure, identified as an organometallic (OM) phase, has been reported for such a reaction. Here we demonstrate the formation of two distinct OM phases during the temperature-induced growth of poly(para-phenylene) from 1,4-dibromobenzene precursors on Cu(110). Beyond the already known linear-OM chains, we show that a phase reorganization to a chessboard-like 2D-OM can be activated in a well-defined temperature range. This new intermediate phase, revealed only when the reaction is carried out at low molecular coverages, was characterized by X-ray photoelectron spectroscopy, scanning tunneling microscopy and near-edge X-ray absorption fine structure spectroscopy, and modeled by density functional theory calculations. Our data show that the 2D-OM remains stable after cooling down the sample and is stabilized by four-Cu clusters at each node. The observation of such unexpected intermediate phase shows the complexity of the mechanisms underlying on-surface synthesis and broadens the understanding of Ullmann coupling, which continues to be astonishing despite its extensive use.

Published
2019

19. New insights on doping effect of (single-, double-wall-) carbon nanotubes by iodine

Author

Nie, Chunyang, Ahmed, Zubair, Tristant, Damien, Puech, Pascal, Dmitri E., Tsentalovich, Headrick, Robert J., Pasquali, Matteo, Kono, Junichiro, Gerber, I.C., Meunier, Vincent, Flahaut, Emmanuel, Datas, Lucien, Monthioux, Marc, Centre interuniversitaire de recherche et d'ingenierie des matériaux (CIRIMAT), Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie du CNRS (INC), Matériaux Multi-fonctionnels et Multi-échelles (CEMES-M3), Centre d'élaboration de matériaux et d'études structurales (CEMES), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie de Toulouse (ICT-FR 2599), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Institut de Recherche pour le Développement (IRD)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université Toulouse III - Paul Sabatier (UT3), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA), Rice University [Houston], Université Fédérale Toulouse Midi-Pyrénées, Department of Chemical and Biomolecular Engineering, Laboratoire de physique et chimie des nano-objets (LPCNO), Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie de Toulouse (ICT-FR 2599), Rensselaer Polytechnic Institute (RPI), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université de Toulouse (UT), Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut de Chimie de Toulouse (ICT), Université de Toulouse (UT)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS), Université de Toulouse (UT)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie du CNRS (INC)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut de Chimie du CNRS (INC)-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), and Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut de Chimie du CNRS (INC)

Subjects
[PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], ComputingMilieux_MISCELLANEOUS
Abstract

International audience

Published
2017

20. Filling mechanisms, composition, structure, and properties of halide-filled DWCNTs

Author

Nie, Chunyang, Zubair, A., Tristant, Damien, Monthioux, Marc, Puech, Pascal, Centre interuniversitaire de recherche et d'ingenierie des matériaux (CIRIMAT), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université de Toulouse (UT), Matériaux Multi-fonctionnels et Multi-échelles (CEMES-M3), Centre d'élaboration de matériaux et d'études structurales (CEMES), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut de Chimie de Toulouse (ICT), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS), Rice University [Houston], Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie du CNRS (INC), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie de Toulouse (ICT-FR 2599), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Institut de Recherche pour le Développement (IRD)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université Toulouse III - Paul Sabatier (UT3), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA), Université Fédérale Toulouse Midi-Pyrénées, Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie du CNRS (INC)-Institut National Polytechnique (Toulouse) (Toulouse INP), and Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut de Chimie du CNRS (INC)-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse)

Subjects
[PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], ComputingMilieux_MISCELLANEOUS
Abstract

International audience

Published
2017

22. An unexpected organometallic intermediate in surface-confined Ullmann coupling

Author

Galeotti, Gianluca, primary, Di Giovannantonio, Marco, additional, Cupo, Andrew, additional, Xing, Sarah, additional, Lipton-Duffin, Josh, additional, Ebrahimi, Maryam, additional, Vasseur, Guillaume, additional, Kierren, Bertrand, additional, Fagot-Revurat, Yannick, additional, Tristant, Damien, additional, Meunier, Vincent, additional, Perepichka, Dmitrii F., additional, Rosei, Federico, additional, and Contini, Giorgio, additional

Published
2019
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24. Analysis of the improvements in the electronic properties of carbon materials by interaction with chemical species : Computational approach combined with Raman spectroscopy

Author

Tristant, Damien, Laboratoire de physique et chimie des nano-objets (LPCNO), Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie de Toulouse (ICT-FR 2599), Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie du CNRS (INC)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut de Chimie du CNRS (INC), Centre d'élaboration de matériaux et d'études structurales (CEMES), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie de Toulouse (ICT-FR 2599), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut de Chimie du CNRS (INC)-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA), INSA de Toulouse, Iann Gerber, Pascal Puech, Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut de Chimie de Toulouse (ICT), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université de Toulouse (UT)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université de Toulouse (UT)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), and Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Conductivité électrique, Spectroscopie Raman, Carbon nanotube, Fibre, Dopage, Graphène, Raman spectroscopy, Doping, Electrical conductivity, Density functional theory, Théorie de la fonctionnelle de la densité, Fiber, [PHYS.PHYS.PHYS-CHEM-PH]Physics [physics]/Physics [physics]/Chemical Physics [physics.chem-ph], Graphene, Nanotube de carbone
Abstract

To analyze the improvements in electronic properties of carbon-based materials, an approach based on the density functional theory supported by Raman spectroscopy was used. The heart of this work is the study of doping in order to open up new paths for the design of innovative materials from nanodevices. These new structures are fibers whose the main component is a carbon nanotube or nanocarbon loaded polymers with molecules, optimizing electrical conduction. A brief introduction is presented on non-covalent species, leading to the best results reported in the literature, namely potassium, iodine and super acids. The graphite intercalation compounds by potassium atoms are analyzed first. The large charge transfer of the alkali directly influences the optical properties of graphene, resulting in a unique Raman signature with a shape change when the excitation energy is twice the shift of the Fermi level due to doping. Then, an exhaustive theoretical study of iodine doping is performed on a monolayer of graphene. Analysis of thermodynamic properties shows that a gradual increase in the recovery rate of the molecules, initially generates a phase transition of iodine adsorption mode, and ends with the formation of polyiodide complexes. These complexes, via a strong electron transfer, lead to the increase of the density of states at the Fermi level. This study is extended to carbon nanotubes, where a very large charge transfer is obtained after interacting either with chlorosulfonic acid molecules by redox reaction, or with iodine molecules. When there is a flow of a large electric current in these fibers, the Joule effect produces a desorption of dopants and reduces the electrical conductivity. This phenomenon is explained by the available number of conduction channels deducted from combined Raman signatures and electronic transport calculations. The local and average temperatures are extracted from Raman and transport data respectively. This work constitutes a coherent set of results as a basis for improving the transport properties.; Pour analyser les améliorations des propriétés électroniques des matériaux carbonés, une approche par la théorie de la fonctionnelle de la densité appuyée par la spectroscopie Raman a été utilisée. Le cœur de ce travail est l’étude du dopage dans le but d’ouvrir de nouvelles voies pour la conception de matériaux à nanocomposants innovants. Ces nouvelles structures sont des fibres dont la brique élémentaire est un nanotube de carbone ou des polymères chargés en nanocarbone avec des molécules optimisant la conduction électrique. Une brève introduction est présentée sur les espèces non-covalentes, conduisant aux meilleurs résultats reportés dans la littérature, à savoir : le potassium, l’iode et les super acides. Les composés d’intercalation du graphite par des atomes de potassium sont analysés en premier. Le fort transfert de charge de l’alcalin influence directement les propriétés optiques du graphène conduisant à une signature Raman singulière avec un changement de forme lorsque l’énergie d’excitation est le double du déplacement du niveau de Fermi dû au dopage. Ensuite, une étude théorique exhaustive du dopage à l’iode est réalisée sur une monocouche de graphène. L’analyse des propriétés thermodynamiques montre qu’une augmentation progressive du taux de recouvrement des molécules engendre d’abord une transition de phase du mode d’adsorption de l’iode et se termine par la formation de complexes polyiodure. Ces complexes, via un fort transfert d’électrons, conduisent à l’augmentation de la densité d’états électronique au niveau de Fermi. Cette étude est étendue aux nanotubes de carbone, où un transfert de charge très important est obtenu après interaction soit avec des molécules d’acide chlorosulfonique par réaction d’oxydo-réduction, soit avec des molécules d’iode. Lors de la circulation d’un fort courant électrique dans ces fibres, l’effet Joule produit une désorption des dopants et réduit la conductivité électrique. Ce phénomène s’explique par le nombre de canaux de conduction disponibles déduit des signatures Raman combinée à des calculs de transport électronique. Les températures locale et moyenne sont extraites des données Raman et de transport respectivement. Ce travail constitue un ensemble cohérent de résultats pouvant servir de base pour améliorer les propriétés de transport.

Published
2016

25. Charged iodide in chains behind the highly efficient iodine doping in carbon nanotubes

Author

Zubair, Ahmed, primary, Tristant, Damien, additional, Nie, Chunyang, additional, Tsentalovich, Dmitri E., additional, Headrick, Robert J., additional, Pasquali, Matteo, additional, Kono, Junichiro, additional, Meunier, Vincent, additional, Flahaut, Emmanuel, additional, Monthioux, Marc, additional, Gerber, Iann C., additional, and Puech, Pascal, additional

Published
2017
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28. Enlightening the ultrahigh electrical conductivities of doped double-wall carbon nanotube fibers by Raman spectroscopy and first-principles calculations

Author

Tristant, Damien, primary, Zubair, Ahmed, additional, Puech, Pascal, additional, Neumayer, Frédéric, additional, Moyano, Sébastien, additional, Headrick, Robert J., additional, Tsentalovich, Dmitri E., additional, Young, Colin C., additional, Gerber, Iann C., additional, Pasquali, Matteo, additional, Kono, Junichiro, additional, and Leotin, Jean, additional

Published
2016
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33. Shell model extension to the valence force field: application to single-layer black phosphorus.

Author

Hackney NW, Tristant D, Cupo A, Daniels C, and Meunier V

Abstract

We propose an extension of the traditional valence force field model to allow for the effect of electronic polarization to be included in the inter-atomic potential. Using density functional theory as a reference, this model is parameterized for the specific case of single-layer black phosphorus by fitting the phonon dispersion relation over the entire Brillouin zone. The model is designed to account for the effect of induced dipole interaction on the long-wavelength (|q[combining right harpoon above]| → 0) modes for the case of homopolar covalent crystals. We demonstrate that the near Γ-point frequencies of the IR-active modes are substantially damped by the inclusion of the induced dipole interaction, in agreement with experiment. The fitting procedure outlined here allows for this model to be adapted to other materials, including but not limited to two-dimensional crystals.

Published
2018
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