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144 results on '"Yannick J Dappe"'

1. Molecular-scale dynamics of light-induced spin cross-over in a two-dimensional layer

Author: Kaushik Bairagi, Olga Iasco, Amandine Bellec, Alexey Kartsev, Dongzhe Li, Jérôme Lagoute, Cyril Chacon, Yann Girard, Sylvie Rousset, Frédéric Miserque, Yannick J Dappe, Alexander Smogunov, Cyrille Barreteau, Marie-Laure Boillot, Talal Mallah, and Vincent Repain
Subjects: Science
Abstract: Spin crossover molecules may find applications in ultimately small magnetic devices, given the sensitivity of their spin-states to external stimuli. Here, the authors show a light-induced transition between two ordered dynamic phases in two-dimensional spin crossover layers on a metallic surface.
Published: 2016
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2. Nonuniform STM Contrast of Self-Assembled Tri‑n‑octyl-triazatriangulenium Tetrafluoroborate on HOPG

Author: Sergii Snegir, Yannick J. Dappe, Dmytro Sysoiev, Thomas Huhn, and Elke Scheer
Subjects: Chemistry, QD1-999
Published: 2023
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3. Hybrid molecular graphene transistor as an operando and optoelectronic platform

Author: Jorge Trasobares, Juan Carlos Martín-Romano, Muhammad Waqas Khaliq, Sandra Ruiz-Gómez, Michael Foerster, Miguel Ángel Niño, Patricia Pedraz, Yannick. J. Dappe, Marina Calero de Ory, Julia García-Pérez, María Acebrón, Manuel Rodríguez Osorio, María Teresa Magaz, Alicia Gomez, Rodolfo Miranda, and Daniel Granados
Subjects: Science
Abstract: Molecular electronics represents an avenue to enrich conventional electronics, but its reproducibility and scalability are still challenging. Here, the authors report the realization of multifunctional hybrid molecular graphene field effect transistors enabling operando spectroscopy and the implementation of optoelectronic logic gates.
Published: 2023
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4. Formation of Monolayer Charge Density Waves and Anomalous Edge Doping in Na Doped Bulk VSe2

Author: Ulysse Chazarin, Mahé Lezoualc'h, Jyh‐Ping Chou, Woei Wu Pai, Abhishek Karn, Raman Sankar, Cyril C. Chacon, Yann Girard, Vincent Repain, Amandine Bellec, Sylvie Rousset, Alexander Smogunov, Yannick J. Dappe, and Jérôme Lagoute
Subjects: electrostatic effect, scanning tunneling microscope, transition metal dichalcogenides, VSe 2, Physics, QC1-999, Technology
Abstract: Abstract Alkali atom doping is an efficient way to induce charge transfer and Fermi level tuning in layered materials through intercalation. However, there is a general lack of microscopic understanding of the effect of doping inhomogeneity in geometric and electronic aspects. Here, we report surface doping of a bulk VSe2 crystal by sodium. Na atoms form intercalated subsurface islands that modify the electronic phase of the top layer of VSe2. In addition to n‐doping, the charge density wave of the intercalated VSe2 surface layer changes from the (4 × 4) bulk phase to the (3×7) known in monolayer phase of VSe2. Surprisingly, an electronic state at the edges of Na‐intercalated area shift anomalously upward in energy as detected by scanning tunneling spectroscopy. This is explained by a local gating effect resulting from local dipoles at the edges. The study illustrates a clear example of intercalation effect that should be general in alkali‐intercalated bulk layered materials.
Published: 2023
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5. Quantum Transport in Large-Scale Patterned Nitrogen-Doped Graphene

Author: Aleksander Bach Lorentzen, Mehdi Bouatou, Cyril Chacon, Yannick J. Dappe, Jérôme Lagoute, and Mads Brandbyge
Subjects: graphene, nitrogen doping, patterning, quantum transport calculations, tight-binding model, Chemistry, QD1-999
Abstract: It has recently been demonstrated how the nitrogen dopant concentration in graphene can be controlled spatially on the nano-meter scale using a molecular mask. This technique may be used to create ballistic electron optics-like structures of high/low doping regions; for example, to focus electron beams, harnessing the quantum wave nature of the electronic propagation. Here, we employ large-scale Greens function transport calculations based on a tight-binding approach. We first benchmark different tight-binding models of nitrogen in graphene with parameters based on density functional theory (DFT) and the virtual crystal approximation (VCA). Then, we study theoretically how the random distribution within the masked regions and the discreteness of the nitrogen scattering centers impact the transport behavior of sharp n−p and n−n′ interfaces formed by different, realistic nitrogen concentrations. We investigate how constrictions for the current can be realized by patterned high/low doping regions with experimentally feasible nitrogen concentrations. The constrictions can guide the electronic current, while the quantized conductance is significantly washed out due to the nitrogen scattering. The implications for device design is that a p−n junction with nitrogen corrugation should still be viable for current focusing. Furthermore, a guiding channel with less nitrogen in the conducting canal preserves more features of quantized conductance and, therefore, its low-noise regime.
Published: 2023
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6. Intrinsic defects and mid-gap states in quasi-one-dimensional indium telluride

Author: Meryem Bouaziz, Aymen Mahmoudi, Geoffroy Kremer, Julien Chaste, César González, Yannick J. Dappe, François Bertran, Patrick Le Fèvre, Marco Pala, Fabrice Oehler, Jean-Christophe Girard, and Abdelkarim Ouerghi
Subjects: Physics, QC1-999
Abstract: Recently, intriguing physical properties have been unraveled in anisotropic semiconductors in which the in-plane electronic band structure anisotropy often originates from the low crystallographic symmetry. The atomic chain is the ultimate limit in material downscaling for electronics—a frontier for establishing an entirely new field of one-dimensional quantum materials. Electronic and structural properties of chain-like InTe are essential for a better understanding of device applications such as thermoelectrics. Here, we use scanning tunneling microscopy/scanning tunneling spectroscopy (STS) measurements and density functional theory (DFT) calculations to image the in-plane structural anisotropy directly in tetragonal InTe. As results, we report the direct observation of one-dimensional In^{1+} chains in InTe. We demonstrate that InTe exhibits a bandgap of about 0.40±0.02 eV located at the M point of the Brillouin zone. Additionally, line defects are observed in our sample and were attributed to In^{1+} chain vacancy along the c-axis—a general feature in many other TlSe-like compounds. Our STS and DFT results prove that the presence of In^{1+} induces a localized gap state, located near the valence band maximum. This acceptor state is responsible for the high intrinsic p-type doping of InTe that we also confirm using angle-resolved photoemission spectroscopy.
Published: 2023
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7. Control of the Organization of 4,4′-bis(carbazole)-1,1′-biphenyl (CBP) Molecular Materials through Siloxane Functionalization

Author: Janah Shaya, Jean-Charles Ribierre, Gabriel Correia, Yannick J. Dappe, Fabrice Mathevet, Loïc Mager, Benoît Heinrich, and Stéphane Méry
Subjects: molecular liquid, liquid crystal, siloxane side-chain, siloxane-terminated side chain, hybrid siloxane-based chain, liquid electronics, Organic chemistry, QD241-441
Abstract: We show that through the introduction of short dimethylsiloxane chains, it was possible to suppress the crystalline state of CBP in favor of various types of organization, transitioning from a soft crystal to a fluid liquid crystal mesophase, then to a liquid state. Characterized by X-ray scattering, all organizations reveal a similar layered configuration in which layers of edge-on lying CBP cores alternate with siloxane. The difference between all CBP organizations essentially lay on the regularity of the molecular packing that modulates the interactions of neighboring conjugated cores. As a result, the materials show quite different thin film absorption and emission properties, which could be correlated to the features of the chemical architectures and the molecular organizations.
Published: 2023
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8. Growth and local electronic properties of Cobalt nanodots underneath graphene on SiC(0001)

Author: Yann Girard, Sarah Benbouabdellah, Outhmane Chahib, Cyril Chacon, Amandine Bellec, Vincent Repain, Jérôme Lagoute, Yannick J. Dappe, César González, Wei-Bin Su, Laboratoire Matériaux et Phénomènes Quantiques (MPQ (UMR_7162)), Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Université Paris-Saclay, CEA, CNRS, SPEC, 91191 Gif-sur-Yvette, France, Departamento de Fisica de Materiales, Universidad Complutense de Madrid = Complutense University of Madrid [Madrid] (UCM), and Institute of Physics, Academia Sinica, Nankang, Taipei 11529, Taiwan
Subjects: Scanning tunneling microscopy / spectroscopy, Density functional theory calculations, [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], General Materials Science, General Chemistry, Cobalt, Silicon carbide, Graphene, Field effect resonance
Abstract: International audience; The coupling of graphene with a ferromagnetic material opens opportunities for technological innovations in spintronics. To obtain this coupling it is necessary to control the elaboration of interfaces at the atomic scale. Here, we present results on cobalt intercalation between graphene and a buffer layer supported on a SiC(0001) substrate. As a result, we obtain cobalt islands covered by graphene whose local electronic properties are measured by scanning tunneling microscopy and spectroscopy. These islands reveal two very distinct shapes and properties. Small-islands with atomic height and very narrow size distribution and, more interestingly, flat cobalt nanodots lower than one nanometer high, that are encapsulated by graphene. Compared to a graphene monolayer on SiC, those nanodots exhibit very different spectroscopic signatures. Using dI/dV local differential conductance spectra together with an analysis of image potential surface states measured thanks to dz/dV spectra, we show that graphene on the nanodots is neutrally charged. Moreover, its 4.65 eV work function is surprisingly larger than the predicted value of 3.8 eV for graphene on Co. First principle calculations show that those Co nanodots can be seen as cobalt bilayer sandwiched between two carbon planes.
Published: 2023
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9. Attenuation Factors in Molecular Electronics: Some Theoretical Concepts

Author: Yannick J. Dappe
Subjects: molecular junctions, attenuation factor, density functional theory, graphene, Technology, Engineering (General). Civil engineering (General), TA1-2040, Biology (General), QH301-705.5, Physics, QC1-999, Chemistry, QD1-999
Abstract: Understanding the electronic transport mechanisms in molecular junctions is of paramount importance to design molecular devices and circuits. In particular, the role of the different junction components contributing to the current decay—namely the attenuation factor—is yet to be clarified. In this short review, we discuss the main theoretical approaches to tackle this question in the non-resonant tunneling regime. We illustrate our purpose through standard symmetric junctions and through recent studies on hybrid molecular junctions using graphene electrodes. In each case, we highlight the contribution from the anchoring groups, the molecular backbone and the electrodes, respectively. In this respect, we consider different anchoring groups and asymmetric junctions. In light of these results, we discuss some perspectives to describe accurately the attenuation factors in molecular electronics.
Published: 2020
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10. Electrochemical gating for single-molecule electronics with hybrid Au|graphene contacts

Author: Shuhui Tao, Qian Zhang, Andrea Vezzoli, Cezhou Zhao, Chun Zhao, Simon J. Higgins, Alexander Smogunov, Yannick J. Dappe, Richard J. Nichols, Li Yang, University of Liverpool, Xi'an Jiaotong-Liverpool University [Suzhou], Service de physique de l'état condensé (SPEC - UMR3680), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Groupe Modélisation et Théorie (GMT), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Institut Rayonnement Matière de Saclay (IRAMIS), and Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay
Subjects: [PHYS]Physics [physics], [CHIM]Chemical Sciences, General Physics and Astronomy, Physical and Theoretical Chemistry
Abstract: International audience; The single-molecular conductance of a redox active viologen molecular bridge between Au|graphene electrodes has been studied in an electrochemical gating configuration in an ionic liquid medium. A clear ''off-on-off'' conductance switching behaviour has been achieved through gating of the redox state when the electrochemical potential is swept. The Au|viologen|graphene junctions show singlemolecule conductance maxima centred close to the equilibrium redox potentials for both reduction steps. The peak conductance of Au|viologen|graphene junctions during the first reduction is significantly higher than that of previously measured Au|viologen|Au junctions. This shows that even though the central viologen moiety is not directly linked to the enclosing electrodes, substituting one gold contact for a graphene one nevertheless has a significant impact on junction conductance values. The experimental data was compared against two theoretical models, namely a phase coherent tunnelling and an incoherent ''hopping'' model. The former is a simple gating monoelectronic model within density functional theory (DFT) which discloses the charge state evolution of the molecule with electrode potential. The latter model is the collective Kuznetsov Ulstrup model for 2-step sequential charge transport through the redox centre in the adiabatic limit. The comparison of both models to the experimental data is discussed for the first time. This work opens perspectives for graphene-based molecular transistors with more effective gating and fundamental understanding of electrochemical electron transfer at the single molecular level.
Published: 2022
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11. Dirac Fermions in Blue Phosphorene Monolayer

Author: Youness Kaddar, Wei Zhang, Hanna Enriquez, Yannick J. Dappe, Azzedine Bendounan, Gérald Dujardin, Omar Mounkachi, Abdallah El kenz, Abdelilah Benyoussef, Abdelkader Kara, Hamid Oughaddou, Laboratory of Condensed Matter and Interdisciplinary Sciences (LaMCScI) B.P. 1014 Faculty of Science Mohammed V University Rabat 10100, Institut des Sciences Moléculaires d’Orsay (ISMO) Université Paris-Saclay Bât. 520, Orsay 91405, France (ISMO), Université Paris-Saclay, CEA, CNRS, SPEC, 91191 Gif-sur-Yvette, France, TEMPO Beamline, Synchrotron SOLEIL L’Orme des Merisiers Saint-Aubin B.P.48, Gif-sur-Yvette F-91192, Department of Physics University of Central Florida Orlando, FL 32816, USA, Département de physique CY Cergy Paris Université Cergy-Pontoise Cedex F-95031, France, and Chinese Scholarship Council and CNRS-France
Subjects: [PHYS]Physics [physics], Biomaterials, PES, Phosphorene, Dirac fermions, STM, Electrochemistry, 2D materials, Condensed Matter Physics, DFT, Electronic, Optical and Magnetic Materials
Abstract: International audience; 2D materials beyond graphene and in particular 2D semiconductors haveraised interest due to their unprecedented electronic properties, such as highcarrier mobility or tunable bandgap. Blue phosphorene is an allotrope of blackphosphorene that resembles graphene as it presents a honeycomb structure.However, it is known to have semiconductor character and the crucial pointis to determine whether this hexagonal phase of phosphorene presents Diracfermions as in graphene. Here, the first compelling experimental evidenceof Dirac fermions in blue phosphorene layer grown on Cu(111) surface ispresented. The results highlight the formation of a highly ordered bluephosphorene sheet with a clear Dirac cone at the high symmetry points of theBrillouin Zone. The charge carriers behave as massless relativistic particles.Therefore, all the expectations held for graphene, such as high-speed electronicdevices based on ballistic transport at room temperature, may also beapplied to blue phosphorene.
Published: 2023
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12. Intrinsic photoanode band engineering: enhanced solar water splitting efficiency mediated by surface segregation in Ti-doped hematite nanorods

Author: Stefan Stanescu, Théo Alun, Yannick J. Dappe, Dris Ihiawakrim, Ovidiu Ersen, and Dana Stanescu
Abstract: Band engineering is thoroughly employed nowadays targeting technologically scalable photoanodes for solar water splitting applications. Most often complex and costly recipes are necessary, for average performances. Here we report very simple photoanode growth and thermal annealing, with effective band engineering results. Strongly enhanced photocurrent, of more than 200 %, is measured for Ti-doped hematite nanorods grown from aqueous solutions and annealed under Nitrogen atmosphere, compared to air annealed ones. Oxidized surface states and increased density of charge carriers are found responsible for the enhanced photoelectrochemical activity, as shown by electrochemical impedance spectroscopy and synchrotron X-rays spectromicroscopies. They are found related to oxygen vacancies, acting as n-dopants, and the formation of pseudo-brookite clusters by surface Ti segregation. Spectro-ptychography is used for the first time at Ti L3 absorption edge to isolate Ti chemical coordination arising from pseudo-brookite clusters contribution. Correlated with electron microscopy investigation and Density Functional Theory (DFT) calculations, our data unambiguously prove the origin of the enhanced photoelectrochemical activity of N2-annealed Ti-doped hematite nanorods. Finally, we present here a handy and cheap surface engineering method beyond the known oxygen vacancy doping, allowing a net gain in the photoelectrochemical activity for the hematite-based photoanodes.
Published: 2023
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13. Surface symmetry effect on the charge transfer at the black, blue, and green phosphorene/graphene interfaces

Author: Zineb Kerrami and Yannick J. Dappe
Subjects: Materials Chemistry, Surfaces and Interfaces, Condensed Matter Physics, Surfaces, Coatings and Films
Published: 2023
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14. Hybrid molecular graphene transistor as an operando and optoelectronic platform

Author: Jorge Trasobares, Juan Carlos Martín-Romano, Muhammad Waqas Khaliq, Sandra Ruiz-Gómez, Michael Foerster, Miguel Ángel Niño, Patricia Pedraz, Yannick. J. Dappe, Marina Calero de Ory, Julia García-Pérez, María Acebrón, Manuel Rodríguez Osorio, María Teresa Magaz, Alicia Gomez, Rodolfo Miranda, and Daniel Granados
Subjects: Multidisciplinary, General Physics and Astronomy, General Chemistry, General Biochemistry, Genetics and Molecular Biology
Abstract: Lack of reproducibility hampers molecular devices integration into large-scale circuits. Thus, incorporating operando characterization can facilitate the understanding of multiple features producing disparities in different devices. In this work, we report the realization of hybrid molecular graphene field effect transistors (m-GFETs) based on 11-(Ferrocenyl)undecanethiol (FcC11SH) micro self-assembled monolayers (μSAMs) and high-quality graphene (Gr) in a back-gated configuration. On the one hand, Gr enables redox electron transfer, avoids molecular degradation and permits operando spectroscopy. On the other hand, molecular electrode decoration shifts the Gr Dirac point (VDP) to neutrality and generates a photocurrent in the Gr electron conduction regime. Benefitting from this heterogeneous response, the m-GFETs can implement optoelectronic AND/OR logic functions. Our approach represents a step forward in the field of molecular scale electronics with implications in sensing and computing based on sustainable chemicals.
Published: 2022
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15. Phthalocyanine reactivity and interaction on the 6H-SiC(0001)-(3 × 3) surface investigated by core-level experiments and simulations

Author: Anu Baby, Guillaume Marcaud, Yannick J. Dappe, Marie D’Angelo, Jean-Louis Cantin, Mathieu G. Silly, Guido Fratesi, Università degli Studi di Milano-Bicocca = University of Milano-Bicocca (UNIMIB), Institut des Nanosciences de Paris (INSP), Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Groupe Modélisation et Théorie (GMT), Service de physique de l'état condensé (SPEC - UMR3680), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Institut Rayonnement Matière de Saclay (IRAMIS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Synchrotron SOLEIL (SSOLEIL), Centre National de la Recherche Scientifique (CNRS), Università degli Studi di Milano = University of Milan (UNIMI), and European Project: 654360,H2020,H2020-INFRAIA-2014-2015,NFFA-Europe(2015)
Subjects: [PHYS]Physics [physics], General Physics and Astronomy, Physical and Theoretical Chemistry
Abstract: International audience; The adsorption of phthalocyanine (H$_2$ Pc) on the 6H-SiC(0001)-(3 x 3) surface is investigated using X-ray photoelectron spectroscopy (XPS), near edge X-ray absorption fine structure spectroscopy (NEXAFS), and density functional theory (DFT) calculations. Spectral features are tracked from the submonolayer to the multilayer growth regime, observing a significant modification of spectroscopic signals at low coverage with respect to the multilayer films, where molecules are weakly interacting. Molecules stay nearly flat on the surface at the mono and submonolayers. Previously proposed adsorption models, where the molecule binds by two N atoms to corresponding Si adatoms, do not reproduce the experimental spectra at the submonolayer coverage. We find instead that another adsorption model where the molecule replaces the two central H atoms by a Si adatom, effectively forming Si-phthalocyanine (SiPc), is both energetically more stable and yields in combination a better agreement between the experimental and simulated spectra. This suggests that the 6H-SiC(0001)-(3 Â 3) surface may be a candidate substrate for the on-surface synthesis of SiPc molecules.
Published: 2022
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16. Intraconfigurational Transition due to Surface-Induced Symmetry Breaking in Noncovalently Bonded Molecules

Author: Cyrille Barreteau, Robert Sporken, Rishav Harsh, Yann Girard, Vincent Repain, Alexander Smogunov, Jérôme Lagoute, Cyril Chacon, Frédéric Joucken, Mads Brandbyge, Amandine Bellec, Fei Gao, Sylvie Rousset, Mehdi Bouatou, Yannick J. Dappe, Laboratoire Matériaux et Phénomènes Quantiques (MPQ (UMR_7162)), Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Centre de Recherche en Physique de la Matière et du Rayonnement [Namur] (PMR), Université de Namur [Namur] (UNamur), Center for Nanostructured Graphene, Danmarks Tekniske Universitet (DTU), Groupe Modélisation et Théorie (GMT), Institut Rayonnement Matière de Saclay (IRAMIS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Service de physique de l'état condensé (SPEC - UMR3680), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Danmarks Tekniske Universitet = Technical University of Denmark (DTU), Service de physique de l'état condensé (SPEC - UMR3680), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Institut Rayonnement Matière de Saclay (IRAMIS), and Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay
Subjects: Materials science, Graphene, 02 engineering and technology, Weak interaction, 010402 general chemistry, 021001 nanoscience & nanotechnology, 01 natural sciences, 0104 chemical sciences, law.invention, Atomic orbital, law, Chemical physics, Molecule, General Materials Science, Redistribution (chemistry), Electron configuration, Symmetry breaking, [PHYS.COND]Physics [physics]/Condensed Matter [cond-mat], Physics::Chemical Physics, Physical and Theoretical Chemistry, 0210 nano-technology, Ground state, ComputingMilieux_MISCELLANEOUS
Abstract: The interaction of molecules with surfaces plays a crucial role in the electronic and chemical properties of supported molecules and needs a comprehensive description of interfacial effects. Here, we unveil the effect of the substrate on the electronic configuration of iron porphyrin molecules on Au(111) and graphene, and we provide a physical picture of the molecule-surface interaction. We show that the frontier orbitals derive from different electronic states depending on the substrate. The origin of this difference comes from molecule-substrate orbital selective coupling caused by reduced symmetry and interaction with the substrate. The weak interaction on graphene keeps a ground state configuration close to the gas phase, while the stronger interaction on gold stabilizes another electronic solution. Our findings reveal the origin of the energy redistribution of molecular states for noncovalently bonded molecules on surfaces.
Published: 2020
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17. Effect of bonding and antibonding character of electronic states on their tunneling spectra

Author: Omar Lahrache, Mehdi Bouatou, Cyril Chacon, Yann Girard, Yannick J. Dappe, Jérôme Lagoute, Alexander Smogunov, Service de physique de l'état condensé (SPEC - UMR3680), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Groupe Modélisation et Théorie (GMT), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Institut Rayonnement Matière de Saclay (IRAMIS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, Laboratoire Matériaux et Phénomènes Quantiques (MPQ (UMR_7162)), Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), MOST (No. 110-2923-M-002 -010), and ANR-20-CE09-0023,DEFINE2D,Ingénierie des défauts dans les matériaux 2D: propriétés à l'échelle atomique et interaction avec des molécules(2020)
Subjects: [PHYS]Physics [physics]
Abstract: International audience; We argue that the bonding or antibonding character of electronic states of a substrate can influence significantly the observed scanning tunneling microscopy (STM) spectra. In particular, the antibonding states formed bynonorthogonal orbitals of the substrate present much stronger extension in the vacuum compared to corresponding bonding combinations and are therefore much more visible in STM experiments. A clear example is providedby black phosphorus (BP), which is one of the most interesting two-dimensional layered materials nowadays. The pronounced asymmetry in its conductance spectra, with significant increase at positive voltage, can beattributed to the antibonding nature of the conduction band compared to the bonding valence band, despite the same pz -orbital character. Furthermore, this asymmetry can be at the origin of different broadenings of frontiermolecular orbitals observed experimentally for molecules on BP.
Published: 2022
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18. Revealing conductance variation of molecular junctions based on an unsupervised data analysis approach

Author: Shuhui Tao, Qian Zhang, Sylvain Pitie, Chenguang Liu, Yinqi Fan, Chun Zhao, Mahamadou Seydou, Yannick J. Dappe, Richard J. Nichols, and Li Yang
Subjects: General Chemical Engineering, Electrochemistry
Published: 2023
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19. Structural properties of Bi/Au(110)

Author: Egzona Neziri, Wei Zhang, Alexander Smogunov, Andrew J Mayne, Abdelkader Kara, Yannick J Dappe, and Hamid Oughaddou
Subjects: Mechanics of Materials, Mechanical Engineering, General Materials Science, Bioengineering, General Chemistry, Electrical and Electronic Engineering
Abstract: Atomically thin bismuth films (2D Bi) are becoming a promising research area due to their unique properties and their wide variety of applications in spintronics, electronic and optoelectronic devices. We report on the structural properties of Bi on Au(110), explored by low-energy electron diffraction (LEED), scanning tunneling microscopy (STM) and density functional theory (DFT) calculations. At a Bi coverage lower than one monolayer (1 ML) various reconstructions are observed, we focus on Bi/Au(110)-c(2 × 2) reconstruction (at 0.5 ML) and Bi/Au(110)-(3 × 3) structure (at 0.66 ML). We propose models for both structures based on STM measurements and further confirm by DFT calculations.
Published: 2023
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20. Asymmetric Effect on the Length Dependence of Oligo(Phenylene ethynylene)-Based Molecular Junctions

Author: Yinqi Fan, Sylvain Pitie, Chenguang Liu, Cezhou Zhao, Chun Zhao, Mahamadou Seydou, Yannick J. Dappe, Richard J. Nichols, Li Yang, University of Liverpool, Interfaces, Traitements, Organisation et Dynamique des Systèmes (ITODYS (UMR_7086)), Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Shenzhen University [Shenzhen], Xi'an Jiaotong-Liverpool University [Suzhou], Service de physique de l'état condensé (SPEC - UMR3680), and Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)
Subjects: [PHYS]Physics [physics], General Energy, Single molecular electronics, [CHIM]Chemical Sciences, oligo (phenylene ethynylene)s, Physical and Theoretical Chemistry, graphene contacts, density functional theory, Surfaces, Coatings and Films, Electronic, Optical and Magnetic Materials
Abstract: International audience; It is well known that the electrical conductance of molecular junctions in the tunneling regime varies exponentially with the length of the molecular backbone. This behavior is strongly influenced by anchoring groups, which connect the molecular backbone to the electrodes and locate the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) resonances with respect to the Fermi level. Nevertheless, most of the studies have been performed on symmetric junctions, namely, using the same electrodes and anchoring groups at both sides of the junctions. Only recently, there have been some reports detailing the influence of introducing asymmetry into single-molecule junctions, using different contacts or different anchoring groups at either end of the molecular bridge. These studies have revealed that such junction asymmetry strongly impacts electrical characteristics. In this study, Au and graphene electrodes were used to provide asymmetry to a single-molecule junction. The conductance and length dependence of amine and methyl sulfide-terminated oligo(phenylene ethynylene) have been determined experimentally and theoretically. The impact of introducing this asymmetry has been quantified by comparing the conductance and β values of oligo(phenylene ethynylene) (OPE)based molecules within Au/Au electrodes and Au/graphene junctions, respectively. Our results show that the introduction of a graphene electrode leads to lower conductance values and attenuation factors, similar to what has been previously observed in alkane chains. This is attributed to a shift of the electronic molecular levels toward the Fermi level, mainly driven by acetylene groups linking adjacent phenyl groups.
Published: 2022
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21. Negative Differential Resistance in Spin-Crossover Molecular Devices

Author: Dongzhe Li, Yongfeng Tong, Kaushik Bairagi, Massine Kelai, Yannick J. Dappe, Jérôme Lagoute, Yann Girard, Sylvie Rousset, Vincent Repain, Cyrille Barreteau, Mads Brandbyge, Alexander Smogunov, Amandine Bellec, 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)-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)-Centre National de la Recherche Scientifique (CNRS), Laboratoire Matériaux et Phénomènes Quantiques (MPQ (UMR_7162)), Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Service de physique de l'état condensé (SPEC - UMR3680), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), and Danmarks Tekniske Universitet = Technical University of Denmark (DTU)
Subjects: Coulomb blockade, Condensed Matter - Mesoscale and Nanoscale Physics, Negative differential resistance, Landauer-Büttiker scattering theory, Spin-crossover molecule, Mesoscale and Nanoscale Physics (cond-mat.mes-hall), scanning tunneling microscopy, FOS: Physical sciences, General Materials Science, Physical and Theoretical Chemistry, [PHYS.COND]Physics [physics]/Condensed Matter [cond-mat], Condensed Matter::Mesoscopic Systems and Quantum Hall Effect, density functional theory
Abstract: We demonstrate, based on low-temperature scanning tunneling microscopy (STM) and spectroscopy, a pronounced negative differential resistance (NDR) in spin-crossover (SCO) molecular devices, where a Fe$^{\text{II}}$ SCO molecule is deposited on surfaces. The STM measurements reveal that the NDR is robust with respect to substrate materials, temperature, and the number of SCO layers. This indicates that the NDR is intrinsically related to the electronic structure of the SCO molecule. Experimental results are supported by density functional theory (DFT) with non-equilibrium Green's functions (NEGF) calculations and a generic theoretical model. While the DFT+NEGF calculations reproduce NDR for a special atomically-sharp STM tip, the effect is attributed to the energy-dependent tip density of states rather than the molecule itself. We, therefore, propose a Coulomb blockade model involving three molecular orbitals with very different spatial localization as suggested by the molecular electronic structure., Comment: 4 figures
Published: 2022
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22. Visualizing In-Plane Junctions in Nitrogen-Doped Graphene

Author: Mehdi Bouatou, Cyril Chacon, Aleksander Bach Lorentzen, Huu Thoai Ngo, Yann Girard, Vincent Repain, Amandine Bellec, Sylvie Rousset, Mads Brandbyge, Yannick J. Dappe, Jérôme Lagoute, Laboratoire Matériaux et Phénomènes Quantiques (MPQ (UMR_7162)), Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Danmarks Tekniske Universitet = Technical University of Denmark (DTU), Service de physique de l'état condensé (SPEC - UMR3680), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Groupe Modélisation et Théorie (GMT), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Institut Rayonnement Matière de Saclay (IRAMIS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, and ANR-20-CE09-0023,DEFINE2D,Ingénierie des défauts dans les matériaux 2D: propriétés à l'échelle atomique et interaction avec des molécules(2020)
Subjects: Biomaterials, p-n junction, graphene, Electrochemistry, nitrogen doping, scanning tunneling microscopy, scanning tunneling spectroscopy, [PHYS.COND]Physics [physics]/Condensed Matter [cond-mat], Condensed Matter Physics, Electronic, Optical and Magnetic Materials
Abstract: International audience; Controlling the spatial distribution of dopants in graphene is the gateway to the realization of graphene-based electronic components. Here, we show that a submonolayer of self-assembled physisorbed molecules can be used as a resist during a post-synthesis nitrogen doping process to realize a nanopatterning of nitrogen dopants in graphene. The resulting formation of domains with different nitrogen concentrations allows obtaining nn' and pn junctions in graphene. We use scanning tunneling microscopy to measure the electronic properties of the junctions at the atomic scale and reveal their intrinsic width that is found to be around 7 nm corresponding to a sharp junction regime.
Published: 2022
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23. Insights on asymmetric BTB-based molecular junctions: Effect of electrode coupling

Author: Sylvain Pitié, Mahamadou Seydou, Yannick J. Dappe, Pascal Martin, François Maurel, Jean Christophe Lacroix, Interfaces, Traitements, Organisation et Dynamique des Systèmes (ITODYS (UMR_7086)), Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Service de physique de l'état condensé (SPEC - UMR3680), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Groupe Modélisation et Théorie (GMT), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Institut Rayonnement Matière de Saclay (IRAMIS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, ANR-10-LABX-0096,SEAM,Science and Engineering for Advanced Materials and devices(2010), and ANR-18-IDEX-0001,Université de Paris,Université de Paris(2018)
Subjects: [PHYS]Physics [physics], General Physics and Astronomy, [CHIM]Chemical Sciences, Physical and Theoretical Chemistry
Abstract: International audience; NEGF and DFT calculations within Fisher Lee formalism are used to explore the effect of the asymmetry and the strength of coupling with the electrode on transport properties of (1-(2-bisthienyl)benzene) oligomers. Electronic analysis of metal-molecule interactions reveals the ionic nature of Ti-C bonds inducing an interfacial dipole. The Ti d-orbitals are found to be strongly coupled to the lowest unoccupied orbital of BTB, thus facilitating charge transfer from Ti to the molecule. The hole transport mechanism is found in the cases of Au-(BTB)$_n$-Au and Au-(BTB)$_n$-Ti while possible combined hole and electron transport is predicted in the case of Ti-(BTB)$_n$-Ti.
Published: 2021
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24. Oligothiophene molecular wires at graphene-based molecular junctions

Author: Yannick J. Dappe, Tingwei Gao, Yinqi Fan, Weitao Su, Cezhou Zhao, Chenguang Liu, Chun Zhao, Chunhui He, Li Yang, Xi'an Jiaotong-Liverpool University [Suzhou], University of Liverpool, College of Materials and Environmental Engineering, Hangzhou Dianzi University, Hangzhou, Service de physique de l'état condensé (SPEC - UMR3680), and Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)
Subjects: [PHYS]Physics [physics], Materials science, Graphene, General Physics and Astronomy, Conductance, Molecular electronics, law.invention, Molecular wire, Chemical physics, law, Electrode, Molecule, [CHIM]Chemical Sciences, Density functional theory, Symmetry breaking, Physical and Theoretical Chemistry
Abstract: International audience; The use of graphene as a new type of electrode at molecular junctions has led to a renewal of molecular electronics. Indeed, the symmetry breaking induced by the graphene electrode yields different electronic behaviors at the molecular junction and in particular enhanced conductance forlonger molecules. In this respect, several studies involving different molecular backbones and anchoring groups have been performed. Here in the same line, we consider oligopthiophene based hybrid gold– graphene junctions and we measure their electrical properties using the STM-I(s) method in order to determine their attenuation factor and the effect of specific anchoring groups. The results are supported by density functional theory (DFT) calculations, and exhibit a similar behavior to what is observed at alkane-based junctions.
Published: 2021
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25. Electron beam analysis induces Cl vacancy defects in a NaCl thin film

Author: Abdelkader Kara, Azzedine Bendounan, Abdelilah Benyoussef, Khalid Quertite, Hanna Enriquez, Abdallah El Kenz, Nicolas Trcera, Andrew J. Mayne, Yannick J. Dappe, Hamid Oughaddou, Gérald Dujardin, Institut des Sciences Moléculaires d'Orsay (ISMO), Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Université Mohammed V de Rabat [Agdal] (UM5), Synchrotron SOLEIL (SSOLEIL), Centre National de la Recherche Scientifique (CNRS), Service de physique de l'état condensé (SPEC - UMR3680), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Groupe Modélisation et Théorie (GMT), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Institut Rayonnement Matière de Saclay (IRAMIS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, University of Central Florida [Orlando] (UCF), CY Cergy Paris Université (CY), and ANR-10-LABX-0035,Nano-Saclay,Paris-Saclay multidisciplinary Nano-Lab(2010)
Subjects: insulating surfaces, [PHYS]Physics [physics], Auger electron spectroscopy, Materials science, Low-energy electron diffraction, Mechanical Engineering, Analytical chemistry, DFT calculation, Bioengineering, General Chemistry, Substrate (electronics), atomic vacancies, law.invention, Mechanics of Materials, law, Desorption, Vacancy defect, Monolayer, General Materials Science, two-dimensional materials, Electrical and Electronic Engineering, Scanning tunneling microscope, Thin film, low temperature scanning tunneling microscopy
Abstract: This work reports on the electron-induced modification of NaCl thin film grown on Ag(110). We show using low energy electron diffraction that electron beam bombardment leads to desorption and formation of Cl vacancy defects on NaCl surface. The topographic structure of these defects is studied using scanning tunneling microscopy (STM) showing the Cl defects as depressions on the NaCl surface. Most of the observed defects are mono-atomic vacancies and are located on flat NaCl terraces. Auger electron spectroscopy confirms the effect of electron exposure on NaCl thin films showing Cl atoms desorption from the surface. Using density functional theory taken into account the van der Waals dispersion interactions, we confirm the observed experimental STM measurements with STM simulation. Furthermore, comparing the adsorption of defect free NaCl and defective NaCl monolayer on Ag(110) surfaces, we found an increase of the adhesion energy and the charge transfer between the NaCl film and the substrate due to the Cl vacancy. In details, the adhesion energy increases between the NaCl film and the metallic Ag substrate from 30.4 meV Å−2 for the NaCl film without Cl vacancy and from 39.5 meV Å−2 for NaCl film with a single Cl vacancy. The charge transfer from the NaCl film to the Ag substrate is enhanced when the vacancy is created, from 0.63e− to 1.25e−.
Published: 2021
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26. Where do the counterions go? Tip-induced dissociation of self-assembled triazatriangulenium-based molecules on Au(111)

Author: Olivier Pluchery, Yannick J. Dappe, Thomas Huhn, Elke Scheer, Dmytro Sysoiev, S. V. Snegir, Universität Konstanz, Groupe Modélisation et Théorie (GMT), Institut Rayonnement Matière de Saclay (IRAMIS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Service de physique de l'état condensé (SPEC - UMR3680), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences (IOCB / CAS), Czech Academy of Sciences [Prague] (CAS), Institut des Nanosciences de Paris (INSP), Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Service de physique de l'état condensé (SPEC - UMR3680), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Institut Rayonnement Matière de Saclay (IRAMIS), and Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay
Subjects: inorganic chemicals, Materials science, General Physics and Astronomy, 02 engineering and technology, Substrate (electronics), 010402 general chemistry, 01 natural sciences, Dissociation (chemistry), law.invention, Metal, law, Electric field, Monolayer, Molecule, ddc:530, Physical and Theoretical Chemistry, chemistry.chemical_classification, 021001 nanoscience & nanotechnology, 0104 chemical sciences, [CHIM.THEO]Chemical Sciences/Theoretical and/or physical chemistry, self-assembled monolayers, triazatriangulenium (TATA), chemistry, Chemical physics, visual_art, visual_art.visual_art_medium, Counterion, Scanning tunneling microscope, 0210 nano-technology
Abstract: Chemical coupling of functional molecules on top of the so-called platform molecules allows the formation of functional self-assembled monolayers (SAMs). An often-used example of such a platform is triazatriangulenium (TATA), which features an extended aromatic core providing good electronic contact to the underlying metal surface. Here, we present a study of the SAM formation of a TATA platform on Au(111) employing scanning tunneling microscopy (STM) under ambient atmospheric conditions. In solution, the TATA platform is stabilized by BF4 counterions, while after deposition on a gold substrate, the localization of the BF4 counterions remains unknown. We used 1,2,4-trichlorobenzene as a solvent of TATA–BF4 to induce SAM formation on a heated (∼50 °C) Au substrate. We show by STM how to detect and distinguish TATA–BF4 from TATA platforms, which lost their BF4 counterions. Finally, we observe a change of the counterion position on the SAM during the STM scanning, which we explain by an electric-field-induced decrease of the electrostatic interaction in TATA–BF4 on the surface. We applied DFT calculations to reveal the influence of the gold lattice and the electric field of the STM tip on the stability of TATA–BF4 physisorbed on the surface. published
Published: 2021
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27. 0D/2D Heterostructures Vertical Single Electron Transistor

Author: L. Simon, Ulrich Nguétchuissi Noumbé, Louis Donald Notemgnou Mouafo, Walid Baaziz, Florian Godel, Bernard Doudin, Ovidiu Ersen, Pierre Seneor, Marie-Blandine Martin, Stéphane Berciaud, Bruno Dlubak, Etienne Lorchat, Jean-Francois Dayen, Yannick J. Dappe, Institut de Physique et Chimie des Matériaux de Strasbourg (IPCMS), Université de Strasbourg (UNISTRA)-Matériaux et nanosciences d'Alsace (FMNGE), Institut de Chimie du CNRS (INC)-Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)-Réseau nanophotonique et optique, Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA), Unité mixte de physique CNRS/Thales (UMPhy CNRS/THALES), THALES-Centre National de la Recherche Scientifique (CNRS), Service de physique de l'état condensé (SPEC - UMR3680), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Institut de chimie et procédés pour l'énergie, l'environnement et la santé (ICPEES), Institut de Chimie du CNRS (INC)-Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Université de Strasbourg (UNISTRA)-Centre National de la Recherche Scientifique (CNRS)-Matériaux et Nanosciences Grand-Est (MNGE), Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut National de la Santé et de la Recherche Médicale (INSERM)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut National de la Santé et de la Recherche Médicale (INSERM)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Réseau nanophotonique et optique, Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA)-Centre National de la Recherche Scientifique (CNRS), THALES [France]-Centre National de la Recherche Scientifique (CNRS), Institut de Science des Matériaux de Mulhouse (IS2M), Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Matériaux et Nanosciences Grand-Est (MNGE), Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut National de la Santé et de la Recherche Médicale (INSERM)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA)-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS)-Réseau nanophotonique et optique, Laboratoire des Matériaux, Surfaces et Procédés pour la Catalyse (LMSPC), Université de Strasbourg (UNISTRA)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Matériaux et Nanosciences Grand-Est (MNGE), Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut National de la Santé et de la Recherche Médicale (INSERM)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Matériaux et Nanosciences Grand-Est (MNGE), Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut National de la Santé et de la Recherche Médicale (INSERM)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS), ANR-19-CE09-0028,MIXES,Hétérostructures de van der Waals à dimensions mixtes pour l'électronique et la spintronique(2019), ANR-19-CE24-0022,COPIN,Détecteur plasmonique à nanoCristaux colloïdaux: une nouvelle filière pour l'OPtoélectronique INfrarouge(2019), ANR-19-CE24-0015,STEM2D,Emetteurs THz de type synchrotron à base de matériaux 2D ondulés(2019), ANR-19-GRF1-0001,SOgraphMEM,Spin Orbit functionalized GRAPHene for resistive-magnetic MEMories(2019), ANR-11-LABX-0058,NIE,Nanostructures en Interaction avec leur Environnement(2011), ANR-10-LABX-0035,Nano-Saclay,Paris-Saclay multidisciplinary Nano-Lab(2010), ANR-10-IDEX-0002,UNISTRA,Par-delà les frontières, l'Université de Strasbourg(2010), univOAK, Archive ouverte, Hétérostructures de van der Waals à dimensions mixtes pour l'électronique et la spintronique - - MIXES2019 - ANR-19-CE09-0028 - AAPG2019 - VALID, Détecteur plasmonique à nanoCristaux colloïdaux: une nouvelle filière pour l'OPtoélectronique INfrarouge - - COPIN2019 - ANR-19-CE24-0022 - AAPG2019 - VALID, Emetteurs THz de type synchrotron à base de matériaux 2D ondulés - - STEM2D2019 - ANR-19-CE24-0015 - AAPG2019 - VALID, Spin Orbit functionalized GRAPHene for resistive-magnetic MEMories - - SOgraphMEM2019 - ANR-19-GRF1-0001 - FLAG-ERA JTC 2019 - VALID, Nanostructures en Interaction avec leur Environnement - - NIE2011 - ANR-11-LABX-0058 - LABX - VALID, Paris-Saclay multidisciplinary Nano-Lab - - Nano-Saclay2010 - ANR-10-LABX-0035 - LABX - VALID, Initiative d'excellence - Par-delà les frontières, l'Université de Strasbourg - - UNISTRA2010 - ANR-10-IDEX-0002 - IDEX - VALID, Centre National de la Recherche Scientifique (CNRS)-Matériaux et nanosciences d'Alsace (FMNGE), Institut de Chimie du CNRS (INC)-Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS)-Réseau nanophotonique et optique, and Institut de Chimie du CNRS (INC)-Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA)-Matériaux et nanosciences d'Alsace (FMNGE)
Subjects: Materials science, 2D heterostructures, single electron transistors, [SPI.NANO] Engineering Sciences [physics]/Micro and nanotechnologies/Microelectronics, 02 engineering and technology, 010402 general chemistry, 01 natural sciences, Nanoclusters, Biomaterials, nanoelectronics, Condensed Matter::Materials Science, Electric field, Electrochemistry, [PHYS.COND]Physics [physics]/Condensed Matter [cond-mat], [SPI.NANO]Engineering Sciences [physics]/Micro and nanotechnologies/Microelectronics, ComputingMilieux_MISCELLANEOUS, [PHYS]Physics [physics], Spintronics, business.industry, Electric potential energy, transition metal dichalcogenides, Coulomb blockade, Heterojunction, 021001 nanoscience & nanotechnology, Condensed Matter Physics, 0104 chemical sciences, Electronic, Optical and Magnetic Materials, Nanoelectronics, Quantum dot, Optoelectronics, nanoparticles, multifunctional materials, 0210 nano-technology, business, [PHYS.COND] Physics [physics]/Condensed Matter [cond-mat]
Abstract: Mixed-dimensional heterostructures formed by the stacking of 2D materials with nanostructures of distinct dimensionality constitute a new class of nanomaterials that offers multifunctionality that goes beyond those of single dimensional systems. An unexplored architecture of single electron transistor (SET) is developed that employs heterostructures made of nanoclusters (0D) grown on a 2D molybdenum disulfide (MoS2) channel. Combining the large Coulomb energy of the nanoclusters with the electronic capabilities of the 2D layer, the concept of 0D–2D vertical SET is unveiled. The MoS2 underneath serves both as a charge tunable channel interconnecting the electrode, and as bottom electrode for each v-SET cell. In addition, its atomic thickness makes it thinner than the Debye screening length, providing electric field transparency functionality that allows for an efficient electric back gate control of the nanoclusters charge state. The Coulomb diamond pattern characteristics of SET are reported, with specific doping dependent nonlinear features arising from the 0D/2D geometry that are elucidated by theoretical modeling. These results hold promise for multifunctional single electron device taking advantage of the versatility of the 2D materials library, with as example envisioned spintronics applications while coupling quantum dots to magnetic 2D material, or to ferroelectric layers for neuromorphic devices.
Published: 2021
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28. Theoretical approach to point defects in a single transition metal dichalcogenide monolayer: conductance and force calculations in MoS 2

Author: Yannick J. Dappe, César González, Departamento de Fisica de Materiales, Universidad Complutense de Madrid = Complutense University of Madrid [Madrid] (UCM), Groupe Modélisation et Théorie (GMT), Service de physique de l'état condensé (SPEC - UMR3680), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Institut Rayonnement Matière de Saclay (IRAMIS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, Institut Rayonnement Matière de Saclay (IRAMIS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Service de physique de l'état condensé (SPEC - UMR3680), and Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)
Subjects: Physics, [PHYS]Physics [physics], 0103 physical sciences, Monolayer, General Physics and Astronomy, Physical chemistry, Conductance, 02 engineering and technology, 021001 nanoscience & nanotechnology, 010306 general physics, 0210 nano-technology, 01 natural sciences
Abstract: International audience; Nous présentons ici une mini-revue de nos différents travaux sur l’étude théorique des défauts dans une monocouche de MoS2. En utilisant la Théorie de la Fonctionnelle de la Densité (DFT), nous avons caractérisé structurellement et électroniquement différents types de défauts à partir de lacunes de S et Mo, ainsi que leurs antisites. En combinaison avec un formalisme de Green–Keldysh, nous avons simulé les images de microscopie à effet tunnel (STM) correspondantes. Également, nous avons déterminé les forces, afin d’interpréter les expériences de microscopie à force atomique (AFM). Nous avons également étudié l’adsorption de molécules sur ces défauts. Finalement, nous présentons de récents résultats sur le calcul de conductance latérale dans des nano-rubans de MoS2 avec défauts. Ces travaux ouvrent la voie à de nouvelles applications en nanoélectronique ou pour les capteurs de gaz, et soulignent la nécessité d’explorer plus avant ces nouveaux systèmes.
Published: 2021
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29. Black Phosphorus for Directed Molecular Assembly with Weak Electronic Coupling

Author: Alexander Smogunov, Cyril Chacon, Mehdi Bouatou, Sylvie Rousset, Rishav Harsh, Vincent Repain, Jérôme Lagoute, Yann Girard, Amandine Bellec, Yannick J. Dappe, Laboratoire Matériaux et Phénomènes Quantiques (MPQ (UMR_7162)), Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Service de physique de l'état condensé (SPEC - UMR3680), and Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)
Subjects: Materials science, Mechanical Engineering, 02 engineering and technology, 010402 general chemistry, 021001 nanoscience & nanotechnology, black phosphorus, 01 natural sciences, Black phosphorus, 0104 chemical sciences, law.invention, Coupling (electronics), Mechanics of Materials, law, Chemical physics, scanning tunneling microscopy, Density functional theory, molecules, Scanning tunneling microscope, [PHYS.COND]Physics [physics]/Condensed Matter [cond-mat], 0210 nano-technology, density functional theory
Abstract: International audience; The combination of two-dimensional materials with organic molecules offers the possibility to obtain low dimensional hybrid materials with tailored properties. Black phosphorus is a monoelemental semiconducting material with a non-planar puckered atomic structure. Here, we study porphyrin molecules on black phosphorus and show that they self-assemble with an epitaxial relationship indicating that the molecule-surface interaction largely dominates the molecule-molecule interaction. The atomic structure of black phosphorus is found to be at the origin of the substrate driven self-assembly. Despite this strong interaction with molecules, the electronic coupling is found to be weak allowing the molecules to maintain the properties of their gas phase, which is the usual behaviour for van der Waals materials. Therefore, the combination of the peculiar puckered structure with the van der Waals nature of black phosphorus provides this material with the ability to interact strongly enough with adsorbed molecules to drive their assembly but weakly enough to keep their electronic properties intact.
Published: 2021
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30. Flat epitaxial quasi-1D phosphorene chains

Author: Azzedine Bendounan, Gérald Dujardin, Alex Smogunov, Abdelkader Kara, Andrew J. Mayne, Hanna Enriquez, Yannick J. Dappe, Hamid Oughaddou, Wei Zhang, Yongfeng Tong, Institut des Sciences Moléculaires d'Orsay (ISMO), Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Synchrotron SOLEIL (SSOLEIL), Centre National de la Recherche Scientifique (CNRS), Service de physique de l'état condensé (SPEC - UMR3680), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Groupe Modélisation et Théorie (GMT), Institut Rayonnement Matière de Saclay (IRAMIS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Service de physique de l'état condensé (SPEC - UMR3680), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), University of Central Florida [Orlando] (UCF), CY Cergy Paris Université (CY), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Institut Rayonnement Matière de Saclay (IRAMIS), and Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay
Subjects: Materials science, Photoemission spectroscopy, Band gap, Science, General Physics and Astronomy, 02 engineering and technology, Substrate (electronics), Epitaxy, 01 natural sciences, General Biochemistry, Genetics and Molecular Biology, Article, law.invention, chemistry.chemical_compound, law, 0103 physical sciences, [PHYS.COND]Physics [physics]/Condensed Matter [cond-mat], 010306 general physics, Multidisciplinary, Condensed matter physics, Graphene, Synthesis and processing, General Chemistry, 021001 nanoscience & nanotechnology, Surface chemistry, Phosphorene, chemistry, Scanning tunneling microscope, 0210 nano-technology, Molecular beam epitaxy
Abstract: The emergence of peculiar phenomena in 1D phosphorene chains (P chains) has been proposed in theoretical studies, notably the Stark and Seebeck effects, room temperature magnetism, and topological phase transitions. Attempts so far to fabricate P chains, using the top-down approach starting from a few layers of bulk black phosphorus, have failed to produce reliably precise control of P chains. We show that molecular beam epitaxy gives a controllable bottom-up approach to grow atomically thin, crystalline 1D flat P chains on a Ag(111) substrate. Scanning tunneling microscopy, angle-resolved photoemission spectroscopy, and density functional theory calculations reveal that the armchair-shaped chains are semiconducting with an intrinsic 1.80 ± 0.20 eV band gap. This could make these P chains an ideal material for opto-electronic devices., Similarly to graphene, attempts to fabricate phosphorene by epitaxy or starting from a few layers of bulk black phosphorus have failed so far. Here, the authors present a controllable bottom-up approach to grow atomically thin, crystalline 1D flat phosphorus chains on a Ag(111) substrate.
Published: 2020
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31. Structural and electronic transitions in few layers of isotopically pure hexagonal boron nitride

Author: Bernard Gil, Hugo Henck, Fabrice Oehler, Julien Chaste, José Avila, Abdelkarim Ouerghi, Debora Pierucci, James H. Edgar, Guillaume Cassabois, Lama Khalil, Yannick J. Dappe, Jihene Zribi, Christine Giorgetti, Song Liu, Emmanuel Lhuillier, Centre de Nanosciences et de Nanotechnologies (C2N), Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Synchrotron SOLEIL (SSOLEIL), Centre National de la Recherche Scientifique (CNRS), Laboratoire Charles Coulomb (L2C), Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Columbia University [New York], Kansas State University, Laboratoire des Solides Irradiés (LSI), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS)-École polytechnique (X), Groupe Modélisation et Théorie (GMT), Institut Rayonnement Matière de Saclay (IRAMIS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Service de physique de l'état condensé (SPEC - UMR3680), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Physico-chimie et dynamique des surfaces (INSP-E6), Institut des Nanosciences de Paris (INSP), Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), ALBA Synchrotron light source [Barcelone], ANR-17-CE24-0030,RhomboG,Propriétés electroniques de couches minces de graphite rhombohedrique(2017), ANR-11-IDEX-0003,IPS,Idex Paris-Saclay(2011), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-École polytechnique (X)-Centre National de la Recherche Scientifique (CNRS), Service de physique de l'état condensé (SPEC - UMR3680), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Institut Rayonnement Matière de Saclay (IRAMIS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, and Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)
Subjects: Materials science, Yield (engineering), Photoemission spectroscopy, Band gap, Stacking, Hexagonal boron nitride, 02 engineering and technology, 021001 nanoscience & nanotechnology, nano-ARPES, Few layer hBN, 01 natural sciences, Electronic band structure, Atomic electron transition, Chemical physics, 0103 physical sciences, [PHYS.COND]Physics [physics]/Condensed Matter [cond-mat], 010306 general physics, 0210 nano-technology, Stacking order, Nanoscopic scale, ComputingMilieux_MISCELLANEOUS
Abstract: International audience; Hexagonal boron nitride (hBN) is attracting tremendous interest as an essential component in van der Waals heterostructures due to its ability to provide weakly interacting interfaces and because of its large bandgap. Although most of theoretical calculations yield the standard AA′ stacking for few-layer hBN, the exact determination of its structural and electronic properties remains unrevealed to date. Here, we provide the direct observation of structural and electronic transitions in few layers of isotopically pure exfoliated h11BN flakes. Our nanoscopic angle-resolved photoemission spectroscopy measurements combined with density-functional theory calculations indicate that the stacking and the band structure can be strongly affected by the thickness of h11BN. Hence, we show that hBN presents an AA′ stacking in its bulk form and another more exotic stacking for three and four layers. Our findings open perspectives in understanding and controlling the stackings in hBN, which could be of great interest for optoelectronic applications.
Published: 2020
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32. Direct Observation of the Reduction of a Molecule on Nitrogen Pairs in Doped Graphene

Author: Jérôme Lagoute, Mehdi Bouatou, Sourav Mondal, Yann Girard, Vincent Repain, Amandine Bellec, Shobhana Narasimhan, Frédéric Joucken, Robert Sporken, Cyril Chacon, Sylvie Rousset, Yannick J. Dappe, Laboratoire Matériaux et Phénomènes Quantiques (MPQ (UMR_7162)), Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Jawaharlal Nehru Centre for Advanced Scientific Research (JNCASR), Centre de Recherche en Physique de la Matière et du Rayonnement [Namur] (PMR), Université de Namur [Namur] (UNamur), Groupe Modélisation et Théorie (GMT), Service de physique de l'état condensé (SPEC - UMR3680), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Institut Rayonnement Matière de Saclay (IRAMIS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), Institut Rayonnement Matière de Saclay (IRAMIS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Service de physique de l'état condensé (SPEC - UMR3680), and Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)
Subjects: Materials science, Bioengineering, 02 engineering and technology, 01 natural sciences, Redox, Atomic units, law.invention, Doped graphene, Charge transfer, law, 0103 physical sciences, Molecule, General Materials Science, Redistribution (chemistry), [PHYS.COND]Physics [physics]/Condensed Matter [cond-mat], 010306 general physics, Scanning tunneling microscopy, ComputingMilieux_MISCELLANEOUS, Dopant, Graphene, Mechanical Engineering, Doping, General Chemistry, 021001 nanoscience & nanotechnology, Condensed Matter Physics, Chemical physics, Scanning tunneling microscope, 0210 nano-technology
Abstract: Incorporating functional atomic sites in graphene is essential for realizing advanced two-dimensional materials. Doping graphene with nitrogen offers the opportunity to tune its chemical activity with significant charge redistribution occurring between molecules and substrate. The necessary atomic scale understanding of how this depends on the spatial distribution of dopants, as well as their positions relative to the molecule, can be provided by scanning tunneling microscopy. Here we show that a noncovalently bonded molecule such as CoPc undergoes a variable charge transfer when placed on N-doped graphene; on a nitrogen pair, it undergoes a redox reaction with an integral charge transfer whereas a lower fractional charge transfer occurs over a single nitrogen. Thus, the charge state of molecules can be tuned by suitably tailoring the conformation of dopant atoms.
Published: 2020
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33. Control of Dipolar Switches on Graphene by a Local Electric Field

Author: Yannick J. Dappe, Jérôme Lagoute, Yann Girard, Cyril Chacon, Sylvie Rousset, Robert Sporken, César González, Mehdi Bouatou, Amandine Bellec, Vincent Repain, Frédéric Joucken, Laboratoire Matériaux et Phénomènes Quantiques (MPQ (UMR_7162)), Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Centre de Recherche en Physique de la Matière et du Rayonnement [Namur] (PMR), Université de Namur [Namur] (UNamur), Universidad Autónoma de Madrid (UAM), Groupe Modélisation et Théorie (GMT), Service de physique de l'état condensé (SPEC - UMR3680), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Institut Rayonnement Matière de Saclay (IRAMIS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), Universidad Autonoma de Madrid (UAM), Institut Rayonnement Matière de Saclay (IRAMIS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Service de physique de l'état condensé (SPEC - UMR3680), and Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)
Subjects: Materials science, 02 engineering and technology, 010402 general chemistry, 01 natural sciences, law.invention, law, Electric field, Molecule, Electronics, Physical and Theoretical Chemistry, [PHYS.COND]Physics [physics]/Condensed Matter [cond-mat], ComputingMilieux_MISCELLANEOUS, Molecular switch, business.industry, Graphene, 021001 nanoscience & nanotechnology, 0104 chemical sciences, Surfaces, Coatings and Films, Electronic, Optical and Magnetic Materials, Dipole, General Energy, Optoelectronics, Scanning tunneling microscope, 0210 nano-technology, business, Realization (systems)
Abstract: The realization of molecular electronic devices relies on the ability to perform elementary operations with functional molecules. Molecular switches are established candidates to realize basic electronic functions and data storage. Macrocyclic molecules such as phthalocyanines and their derivatives provide a family of compounds that can be switched by external stimuli between two stable states. Using scanning tunneling microscopy, we investigated tin phthalocyanine on graphene. We show that these molecules can be reversibly switched between two states and that the interaction of their electric dipole with a local electric field drives the switching yield and direction. The control at the single-molecule level of the molecular conformation in a bidimensional lattice is then used to achieve high-density data storage.
Published: 2020
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34. Charge transfers and charged defects in WSe 2 /graphene-SiC interfaces

Author: Benjamin Grévin, Y. Almadori, Pascal Pochet, C. Vergnaud, Bérangère Hyot, C Paillet, Timotée Journot, M.-T. Dau, Yannick J. Dappe, Matthieu Jamet, Service de physique de l'état condensé (SPEC - UMR3680), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), SYstèmes Moléculaires et nanoMatériaux pour l’Energie et la Santé (SYMMES), Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes (UGA), Département Interfaces pour l'énergie, la Santé et l'Environnement (DIESE), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), SPINtronique et TEchnologie des Composants (SPINTEC), Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Commissariat à l'énergie atomique et aux énergies alternatives - Laboratoire d'Electronique et de Technologie de l'Information (CEA-LETI), Direction de Recherche Technologique (CEA) (DRT (CEA)), Modélisation et Exploration des Matériaux (MEM), Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Synthèse, Structure et Propriétés de Matériaux Fonctionnels (STEP ), and Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes (UGA)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche Interdisciplinaire de Grenoble (IRIG)
Subjects: Materials science, Bioengineering, 02 engineering and technology, 010402 general chemistry, Kelvin probe force microscopy, 01 natural sciences, law.invention, charge defect, chemistry.chemical_compound, non-contact atomic force microscopy, law, Monolayer, Tungsten diselenide, General Materials Science, Schottky-Mott model, Electrical and Electronic Engineering, Kelvin probe force microscope, [PHYS]Physics [physics], Graphene, Mechanical Engineering, graphene, charge transfer, General Chemistry, transition metal dichalcogenide, 021001 nanoscience & nanotechnology, Electrostatics, 0104 chemical sciences, chemistry, Mechanics of Materials, Chemical physics, Density functional theory, van der Waals heterostructures, 0210 nano-technology, Bilayer graphene, Non-contact atomic force microscopy
Abstract: International audience; We report on Kelvin Probe Force Microscopy (KPFM) and Density Functional Theory (DFT) investigations of charge transfers in vertical heterojunctions between tungsten diselenide (WSe2) layers and graphene on silicon carbide substrates. The experimental data reveal the existence of an interface dipole, which is shown by DFT to originate from the neutralization of the graphene n-doping by an electron transfer towards the transition metal dichalcogenide (TMD) layer. The relative vacuum level shift probed by KPFM between the TMD and the substrate stays constant when passing from monolayer to bilayer graphene, which confirms that the Schottky-Mott model can be rigorously applied to these interfaces by taking into account the charge transfer from the substrate to the TMD. DFT calculations show that the first TMD layer absorbs almost all the excess charges contained in the graphene, and that the second TMD layer shall not play a significant role in the electrostatics of the system. Negatively charged defect at the TMD edges contribute however to the electrostatic landscape probed by KPFM on both TMD layers.
Published: 2020
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35. Decoupling Molybdenum Disulfide from Its Substrate by Cesium Intercalation

Author: Simone Lisi, Marco Bianchi, Olivier Geaymond, Valérie Guisset, Johann Coraux, Estelle Mazaleyrat, Ana Cristina Gómez Herrero, Van-Dung Nguyen, Gilles Renaud, Claude Chapelier, Roberto Sant, Matthieu Jamet, Philip Hofmann, Laurence Magaud, Philippe David, Yannick J. Dappe, Alain Marty, Systèmes hybrides de basse dimensionnalité (HYBRID), Institut Néel (NEEL), Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), Université Grenoble Alpes (UGA), PHotonique, ELectronique et Ingénierie QuantiqueS (PHELIQS), Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes (UGA), CRG et Grands Instruments (CRG), Epitaxie et couches minces (EpiCM), SPINtronique et TEchnologie des Composants (SPINTEC), Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Laboratoire de Transport Electronique Quantique et Supraconductivité (LaTEQS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes (UGA)-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Groupe Modélisation et Théorie (GMT), Institut Rayonnement Matière de Saclay (IRAMIS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Service de physique de l'état condensé (SPEC - UMR3680), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Interdisciplinary Nanoscience Center (iNANO), Aarhus University [Aarhus], Nanostructures et Rayonnement Synchrotron (NRS ), Modélisation et Exploration des Matériaux (MEM), Systèmes hybrides de basse dimensionnalité (NEEL - HYBRID), CRG & Grands instruments (NEEL - CRG), Epitaxie et couches minces (NEEL- EpiCM), Service de physique de l'état condensé (SPEC - UMR3680), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Institut Rayonnement Matière de Saclay (IRAMIS), and Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay
Subjects: Materials science, Intercalation (chemistry), Surface X-ray Diffraction, chemistry.chemical_element, FOS: Physical sciences, 02 engineering and technology, 010402 general chemistry, 01 natural sciences, chemistry.chemical_compound, Molybdenum Disulfide, Transition metal, Intercalation, Lamellar structure, Physical and Theoretical Chemistry, Molybdenum disulfide, Condensed Matter - Materials Science, Substrate (chemistry), Materials Science (cond-mat.mtrl-sci), 021001 nanoscience & nanotechnology, 0104 chemical sciences, Surfaces, Coatings and Films, Electronic, Optical and Magnetic Materials, Crystallography, General Energy, chemistry, Scanning Tunneling Microscopy, Caesium, Density functional theory, [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], 0210 nano-technology, Decoupling (electronics)
Abstract: Intercalation of alkali atoms within the lamellar transition metal dichalcogenides is a possible route toward a new generation of batteries. It is also a way to induce structural phase transitions authorizing the realization of optical and electrical switches in this class of materials. The process of intercalation has been mostly studied in three-dimensional dichalcogenide films. Here, we address the case of a single-layer of molybdenum disulfide (MoS$_2$), deposited on a gold substrate, and intercalated with cesium (Cs) in ultra-clean conditions (ultrahigh vacuum). We show that intercalation decouples MoS$_2$ from its substrate. We reveal electron transfer from Cs to MoS$_2$, relative changes in the energy of the valence band maxima, and electronic disorder induced by structural disorder in the intercalated Cs layer. Besides, we find an abnormal lattice expansion of MoS$_2$, which we relate to immediate vicinity of Cs. Intercalation is thermally activated, and so is the reverse process of de-intercalation. Our work opens the route to a microscopic understanding of a process of relevance in several possible future technologies, and shows a way to manipulate the properties of two-dimensional dichalcogenides by "under-cover" functionalization., Comment: 6 figures
Published: 2020
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36. Order and disorder at the C-face of SiC: A hybrid surface reconstruction

Author: Normand Mousseau, Laurence Magaud, César González, Pascal Pochet, Yannick J. Dappe, Eduardo Machado-Charry, Graz University of Technology [Graz] (TU Graz), Universidad Autónoma de Madrid (UAM), Service de physique de l'état condensé (SPEC - UMR3680), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Systèmes hybrides de basse dimensionnalité (NEEL - HYBRID), Institut Néel (NEEL), Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), Université Grenoble Alpes (UGA), Université de Montréal (UdeM), Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Universidad Autonoma de Madrid (UAM), and Systèmes hybrides de basse dimensionnalité (HYBRID)
Subjects: 010302 applied physics, [PHYS]Physics [physics], Physics and Astronomy (miscellaneous), Silicon, Passivation, Dangling bond, chemistry.chemical_element, Conductance, 02 engineering and technology, 021001 nanoscience & nanotechnology, 01 natural sciences, law.invention, chemistry, law, Chemical physics, 0103 physical sciences, Potential energy surface, Density functional theory, Scanning tunneling microscope, 0210 nano-technology, Surface reconstruction
Abstract: In this Letter, we explore the potential energy surface (PES) of the 3 × 3 C-face of SiC by means of the density functional theory. Following an extensive and intuitive exploration, we propose a model for this surface reconstruction based on an all-silicon over-layer forming an ordered honeycomb-Kagome network. This model is compared to the available scanning tunneling microscope (STM) topographies and conductance maps. Our STM simulations reproduce the three main characteristics observed in the measurements, revealing the underlying complex and hybrid passivation scheme. Indeed, below the ordered over-layer, the competition between two incompatible properties of silicon induces a strong disorder in the charge transfer between unpassivated dangling bonds of different chemistry. This effect in conjunction with the glassy-like character of the PES explains why it has taken decades to provide an accurate atomistic representation for this structure.
Published: 2020
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37. Symmetry Effects on Attenuation Factors in Graphene-Based Molecular Junctions

Author: Li Yang, Qian Zhang, Chunhui He, Alexander Smogunov, Yannick J. Dappe, Ruowei Yi, Cezhou Zhao, Shuhui Tao, Weitao Su, Richard J. Nichols, University of Liverpool, Department of Chemistry, Suzhou, Jiangsu, 215123 China, Department of Electrical Engineering and Electronics, Xi'an Jiaotong University (Xjtu), Hangzhou Dianzi University (HDU), Groupe Modélisation et Théorie (GMT), Service de physique de l'état condensé (SPEC - UMR3680), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Institut Rayonnement Matière de Saclay (IRAMIS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, Institut Rayonnement Matière de Saclay (IRAMIS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Service de physique de l'état condensé (SPEC - UMR3680), and Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)
Subjects: [PHYS]Physics [physics], Condensed matter physics, Chemistry, Graphene, Conductance, 02 engineering and technology, 010402 general chemistry, 021001 nanoscience & nanotechnology, 01 natural sciences, 0104 chemical sciences, law.invention, Coupling (electronics), symbols.namesake, Electrical resistance and conductance, law, Chemisorption, Chemical physics, Electrode, symbols, General Materials Science, Density functional theory, Physical and Theoretical Chemistry, van der Waals force, 0210 nano-technology
Abstract: International audience; Unique structural and electronic characteristics of graphene make it an attractive contact for fundamental single-molecule electrical studies. With this in mind, we have probed here the electrical conductance of a molecular junction basedon $\alpha$,$\omega$-diaminoalkane chains sandwiched between a gold and a graphene electrode.Using an STM based I(s) method combined with density functional theory-based transport calculations, we demonstrate that the resulting attenuation factor turns out to be much lower when compared to the standard molecular junction between twogold electrodes. This effect is attributed to asymmetric coupling of the molecule through strong chemisorption at the gold electrode and weaker van der Waals contact at graphene. Moreover, this asymmetric coupling induces higher conductance than that in the same hybrid metal−graphene molecular junction using standard thiol anchoring groups.
Published: 2017
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38. Ultrafast electron dynamics in twisted graphene by femtosecond photoemission electron microscopy

Author: Ken Onda, Keiki Fukumoto, Hakim Arezki, Daniela Felice, Mohamed Boutchich, Ken Sakurai, Yannick J. Dappe, Shin-ya Koshihara, KEK (High energy accelerator research organization), Laboratoire Génie électrique et électronique de Paris (GeePs), Université Paris-Sud - Paris 11 (UP11)-Université Pierre et Marie Curie - Paris 6 (UPMC)-CentraleSupélec-Centre National de la Recherche Scientifique (CNRS), Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo, 152-8550, Japan, Service de physique de l'état condensé (SPEC - UMR3680), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Kyushu University, 744 Motooka, Nishi-ku, Fukuoka, 819-0395, Japan, and Kyushu University
Subjects: Materials science, Band gap, Physics::Optics, Nanotechnology, 02 engineering and technology, Rotation, 01 natural sciences, law.invention, [SPI]Engineering Sciences [physics], Condensed Matter::Materials Science, law, 0103 physical sciences, General Materials Science, 010306 general physics, ComputingMilieux_MISCELLANEOUS, Graphene, business.industry, General Chemistry, 021001 nanoscience & nanotechnology, Photoemission electron microscopy, Femtosecond, Optoelectronics, Photonics, 0210 nano-technology, business, Ultrashort pulse, Excitation
Abstract: Twisted multilayer graphene (tMLG) present electronic properties that depend on the relative misalignment and interaction between layers. These interactions affect the band structures and the carrier dynamics upon photonic excitation. These structures are being under scrutiny and recent work high-lighted the strong potential they offer for optoelectronic devices. However, the ultrafast carrier dynamics is still at an early stage, often due to the instrumental limitations. Here, we investigated the carrier dynamics by femtosecond photoemission electron microscopy of chemical vapor deposited (CVD) twisted graphene super lattices presenting different interlayer rotation angles. The photo-generated carrier lifetimes in these selected regions show a longer lifetime compared to monolayer graphene (1 ML). This observation is assigned to the presence of band gap and sub bands in the trilayer graphene and has been supported by DFT calculations.
Published: 2017
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39. Weakly Trapped, Charged, and Free Excitons in Single-Layer MoS2 in the Presence of Defects, Strain, and Charged Impurities

Author: Sudipta Dubey, Felix Herziger, Raul Arenal, Kenji Watanabe, Julien Renard, Johann Coraux, César González, Pierre Mallet, Vincent Bouchiat, Takashi Taniguchi, Laurence Magaud, Yannick J. Dappe, V. Cherkez, Goutham Nayak, Laëtitia Marty, Toai Le Quang, Nedjma Bendiab, Simone Lisi, Jean-Yves Veuillen, Van-Dung Nguyen, Systèmes hybrides de basse dimensionnalité (NEEL - HYBRID), Institut Néel (NEEL), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Nano-Electronique Quantique et Spectroscopie (NEEL - QuNES), Departamento de Fisica, Universidad de Oviedo, 33006 Oviedo, Spain, Universidad de Oviedo [Oviedo], Groupe Modélisation et Théorie (GMT), Service de physique de l'état condensé (SPEC - UMR3680), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Institut Rayonnement Matière de Saclay (IRAMIS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, National Institute for Materials Science (NIMS), University of Zaragoza - Universidad de Zaragoza [Zaragoza], Systèmes hybrides de basse dimensionnalité (HYBRID), Nano-Electronique Quantique et Spectroscopie (QuNES), Institut Rayonnement Matière de Saclay (IRAMIS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Service de physique de l'état condensé (SPEC - UMR3680), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), and National Institute for Materials Science
Subjects: inorganic chemicals, Photoluminescence, Materials science, Exciton, Binding energy, FOS: Physical sciences, General Physics and Astronomy, 02 engineering and technology, 01 natural sciences, law.invention, Condensed Matter::Materials Science, symbols.namesake, law, Impurity, 0103 physical sciences, General Materials Science, 010306 general physics, Condensed Matter - Materials Science, [PHYS.PHYS.PHYS-OPTICS]Physics [physics]/Physics [physics]/Optics [physics.optics], Doping, technology, industry, and agriculture, General Engineering, Materials Science (cond-mat.mtrl-sci), 021001 nanoscience & nanotechnology, Chemical physics, [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], symbols, Density functional theory, Scanning tunneling microscope, Atomic physics, 0210 nano-technology, Raman spectroscopy
Abstract: International audience; Few- and single-layer MoS2 host substantial densities of defects. They are thought to influence the doping level, the crystal structure, and the binding of electron-hole pairs. We disentangle the concomitant spectroscopic expression of all three effects, and identify to which extent they are intrinsic to the material or extrinsic to it, \textit{i.e.} related to its local environment. We do so by using different sources of MoS2 --- a natural one and one prepared at high pressure and high temperature --- and different substrates bringing varying amounts of charged impurities, and by separating the contributions of internal strain and doping in Raman spectra. Photoluminescence unveils various optically-active excitonic complexes. We discover a defect-bound state having a low binding energy of 20 meV, that does not appear sensitive to strain and doping, unlike charged excitons. Conversely, the defect does not significantly dope or strain MoS2. Scanning tunneling microscopy and density functional theory simulations point to substitutional atoms, presumably individual nitrogen atoms at the sulfur site. Our work shows the way to a systematic understanding of the effect of external and internal fields on the optical properties of two-dimensional materials.
Published: 2017
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40. Kinked row-induced chirality driven by molecule-substrate interactions

Author: Emmanuelle Lacaze, Oleksiy L. Kapitanchuk, Yannick J. Dappe, Delphine Coursault, S. V. Snegir, Chuiko Institute of Surface Chemistry, National Academy of Sciences of Ukraine (NASU), Service de physique de l'état condensé (SPEC - UMR3680), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Groupe Modélisation et Théorie (GMT), Institut Rayonnement Matière de Saclay (IRAMIS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Service de physique de l'état condensé (SPEC - UMR3680), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Bogolyubov Institute for Theoretical Physics, Laboratoire Ondes et Matière d'Aquitaine (LOMA), Université de Bordeaux (UB)-Centre National de la Recherche Scientifique (CNRS), Physico-chimie et dynamique des surfaces (INSP-E6), Institut des Nanosciences de Paris (INSP), Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Institut Rayonnement Matière de Saclay (IRAMIS), and Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay
Subjects: chemistry.chemical_classification, Steric effects, Substrate Interaction, Materials science, Intermolecular force, General Physics and Astronomy, Substrate (chemistry), 02 engineering and technology, 010402 general chemistry, 021001 nanoscience & nanotechnology, 01 natural sciences, 0104 chemical sciences, Crystallography, chemistry, Phenomenological model, [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], Molecule, ddc:530, Physical and Theoretical Chemistry, 0210 nano-technology, Chirality (chemistry), Alkyl
Abstract: Combining STM measurements on three different substrates (HOPG, MoS2, and Au[111]) together with DFT calculations allow for analysis of the origin of the self-assembly of 4-cyano-4′-n-decylbiphenyl (10CB) molecules into kinked row structures using a previously developed phenomenological model. This molecule has an alkyl chain with 10 carbons and a cyanobiphenyl group with a particularly large dipole moment. 10CB represents a toy model that we use here to unravel the relationship between the induced kinked structure, in particular the corresponding chirality expression, and the balanced intermolecular/molecule–substrate interaction. We show that the local ordered structure is driven by the typical alkyl chain/substrate interaction for HOPG and Au[111] and the cyanobiphenyl group/substrate interaction for MoS2. The strongest molecule/substrate interactions are observed for MoS2 and Au[111]. These strong interactions should have led to non-kinked, commensurate adsorbed structures. However, this latter appears impossible due to steric interactions between the neighboring cyanobiphenyl groups that lead to a fan-shape structure of the cyanobiphenyl packing on the three substrates. As a result, the kink-induced chirality is particularly large on MoS2 and Au[111]. A further breaking of symmetry is observed on Au[111] due to an asymmetry of the facing molecules in the rows induced by similar interactions with the substrate of both the alkyl chain and the cyanobiphenyl group. We calculate that the overall 10CB/Au[111] interaction is of the order of 2 eV per molecule. The close 10CB/MoS2 interaction, in contrast, is dominated by the cyanobiphenyl group, being particularly large possibly due to dipole–dipole interactions between the cyanobiphenyl groups and the MoS2 substrate.
Published: 2020
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41. Charge transport in hybrid platinum/molecule/graphene single molecule junctions

Author: Zhenyu Chen, Richard J. Nichols, Chunhui He, Cezhou Zhao, Chenguang Liu, Chun Zhao, Li Yang, Qian Zhang, Yannick J. Dappe, Tingwei Gao, Xi'an Jiaotong-Liverpool University [Suzhou], University of Liverpool, Groupe Modélisation et Théorie (GMT), Service de physique de l'état condensé (SPEC - UMR3680), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Institut Rayonnement Matière de Saclay (IRAMIS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, Institut Rayonnement Matière de Saclay (IRAMIS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Service de physique de l'état condensé (SPEC - UMR3680), and Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)
Subjects: molecule-electrode contact, Materials science, General Physics and Astronomy, chemistry.chemical_element, 02 engineering and technology, 010402 general chemistry, 01 natural sciences, Molecular physics, law.invention, symbols.namesake, law, Rectangular potential barrier, Physical and Theoretical Chemistry, HOMO/LUMO, Quantum tunnelling, density functional theory, Pt-graphene electrode, alkanedithiol, Graphene, Conductance, 021001 nanoscience & nanotechnology, 0104 chemical sciences, chemistry, Single-molecule junctions, symbols, [PHYS.PHYS.PHYS-CHEM-PH]Physics [physics]/Physics [physics]/Chemical Physics [physics.chem-ph], Scanning tunneling microscope, van der Waals force, 0210 nano-technology, Platinum
Abstract: International audience; The single molecule conductance of hybrid platinum/alkanedithiol/graphene junctions has been investigated with a focus on understanding the influence of employing two very different contact types. We call this an ''anti-symmetric'' configuration, with the two different contacts here being platinum and graphene, which respectively provide very different electronic coupling to the alkanedithiol bridge. The conductance of these junctions is experimentally investigated by using a non-contact scanning tunneling microscopy (STM) based method called the I(s) technique. These experimental determinations are supported by density functional theory (DFT) calculations. These alkanedithiol bridging molecules conduct electric current through the highest occupied molecular orbital (HOMO), and junctions formed with Pt/graphene electrode pairs are slightly more conductive than those formed with Au/graphene electrodes which we previously investigated. This is consistent with the lower work function of gold than that of platinum. The measured conductance decays exponentially with the length of the molecular bridge with a low tunneling decay constant, which has a similar value for Pt/graphene and Au/graphene electrode pairs, respectively. These new results underline the importance of the coupling asymmetry between the two electrodes, more than the type of the metal electrode itself. Importantly, the tunneling decay constant is much lower than that of alkanedithiols with the symmetrical equivalent, i.e. identical metal electrodes. We attribute this difference to the relatively weak van der Waals coupling at the graphene interface and the strong bond dipole at the Pt-S interface, resulting in a decrease in the potential barrier at the interface.
Published: 2020
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42. Dispersing and semi-flat bands in the wide band gap two-dimensional semiconductor bilayer silicon oxide

Author: Pascal Pochet, Yannick J. Dappe, Johann Coraux, Patrick Le Fèvre, Luc Moreau, J. C. Alvarez-Quiceno, François Bertran, César González, Muriel Sicot, Bertrand Kierren, Julien E. Rault, Thomas Pierron, Geoffroy Kremer, Yannick Fagot-Revurat, Institut Jean Lamour (IJL), Université de Lorraine (UL)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Fribourg Center for Nanomaterials, Département de Physique, Albert-Ludwigs-Universität Freiburg, Laboratory of Atomistic Simulation (LSIM), Modélisation et Exploration des Matériaux (MEM), Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes (UGA)-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes (UGA), Departamento de Fisica de Materiales, Universidad Complutense de Madrid = Complutense University of Madrid [Madrid] (UCM), Synchrotron SOLEIL (SSOLEIL), Centre National de la Recherche Scientifique (CNRS), Service de physique de l'état condensé (SPEC - UMR3680), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Systèmes hybrides de basse dimensionnalité (HYBRID), Institut Néel (NEEL), Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), Université Grenoble Alpes (UGA), Department of Physics [Fribourg], Université de Fribourg = University of Fribourg (UNIFR), Institut de Chimie du CNRS (INC)-Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Departamento de Física de Materiales [Madrid], Universidad Autónoma de Madrid (UAM), Instituto de Magnetismo Aplicado, Groupe Modélisation et Théorie (GMT), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Institut Rayonnement Matière de Saclay (IRAMIS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, Systèmes hybrides de basse dimensionnalité (NEEL - HYBRID), G. K. acknowledges financial support from the Swiss National Science Foundation (SNSF) Grant No. P00P2 170597. The DFT calculations were done using French supercomputers (GENCI, # 6194) and the Predictive Simulation Center facility that gathers in Grenoble SPINTEC, L Sim and Leti. We thanks Professor N. Mousseau for useful discussions. C. G. acknowledges finantial support from the Community of Madrid through the project NANOMAGCOST CM-S2018/NMT-4321., and ANR-14-OHRI-0004,2DTransformers,Matériaux bidimensionnels à changement de phase(2014)
Subjects: bilayer, Materials science, Band gap, FOS: Physical sciences, 02 engineering and technology, 01 natural sciences, Molecular physics, law.invention, law, 0103 physical sciences, Photoemission spectroscopy, General Materials Science, 010306 general physics, Electronic band structure, Silicon oxide, Condensed Matter - Materials Science, business.industry, Graphene, Mechanical Engineering, Bilayer, Wide-bandgap semiconductor, Materials Science (cond-mat.mtrl-sci), General Chemistry, 021001 nanoscience & nanotechnology, Condensed Matter Physics, Semiconductor, Mechanics of Materials, Density functional theory calculations, 2D silicon oxide film, [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], Density functional theory, 0210 nano-technology, business
Abstract: Epitaxial bilayer silicon oxide is a transferable two-dimensional material predicted to be a wide band gap semiconductor, with potential applications for deep UV optoelectronics, or as a building block of van der Waals heterostructures. The prerequisite to any sort of such applications is the knowledge of the electronic band structure, which we unveil using angle-resolved photoemission spectroscopy and rationalize with the help of density functional theory (DFT) calculations. We discover dispersing bands related to electronic delocalization within the top and bottom planes of the material, with two linear crossings reminiscent of those predicted in bilayer AA-stacked graphene, and semi-flat bands stemming from the chemical bridges between the two planes. This band structure is robust against exposure to air, and can be controlled by exposure to oxygen. We provide an experimental lower-estimate of the band gap size of 5 eV and predict a full gap of 7.36 eV using DFT calculations.
Published: 2020
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43. Silicene Nanoribbons on an Insulating Thin Film

Author: Hamid Oughaddou, Nicolas Trcera, Yannick J. Dappe, Abdelilah Benyoussef, Pierre Lagarde, Gérald Dujardin, Andrew J. Mayne, Abdallah El Kenz, Azzedine Bendounan, Abdelkader Kara, Hanna Enriquez, Khalid Quertite, Yongfeng Tong, Institut des Sciences Moléculaires d'Orsay (ISMO), Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Synchrotron SOLEIL (SSOLEIL), Centre National de la Recherche Scientifique (CNRS), Université Mohammed V de Rabat [Agdal], Service de physique de l'état condensé (SPEC - UMR3680), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Groupe Modélisation et Théorie (GMT), Institut Rayonnement Matière de Saclay (IRAMIS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Service de physique de l'état condensé (SPEC - UMR3680), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), University of Central Florida [Orlando] (UCF), University of Mohammed V, CY Cergy Paris Université (CY), Université Mohammed V de Rabat [Agdal] (UM5), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Institut Rayonnement Matière de Saclay (IRAMIS), and Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay
Subjects: Materials science, Silicon, FOS: Physical sciences, chemistry.chemical_element, Nanotechnology, 02 engineering and technology, 010402 general chemistry, 01 natural sciences, Biomaterials, Metal, Electrochemistry, Metal substrate, Thin film, Electronic properties, Condensed Matter - Materials Science, Silicene, Materials Science (cond-mat.mtrl-sci), 021001 nanoscience & nanotechnology, Condensed Matter Physics, 0104 chemical sciences, Electronic, Optical and Magnetic Materials, chemistry, visual_art, visual_art.visual_art_medium, [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], 0210 nano-technology
Abstract: International audience; Silicene, a new 2D material has attracted intense research because of the ubiquitous use of silicon in modern technology. However, producing free‐standing silicene has proved to be a huge challenge. Until now, silicene could be synthesized only on metal surfaces where it naturally forms strong interactions with the metal substrate that modify its electronic properties. Here, the authors report the first experimental evidence of silicene nanoribbons on an insulating NaCl thin film. This work represents a major breakthrough, for the study of the intrinsic properties of silicene, and by extension to other 2D materials that have so far only been grown on metal surfaces.
Published: 2020
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44. Phosphorus Pentamers: Floating Nanoflowers form a 2D Network

Author: Yannick J. Dappe, Hamid Oughaddou, Azzedine Bendounan, Yongfeng Tong, Andrew J. Mayne, Wei Zhang, Hanna Enriquez, Gérald Dujardin, Abdelkader Kara, Institut des Sciences Moléculaires d'Orsay (ISMO), Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Synchrotron SOLEIL (SSOLEIL), Centre National de la Recherche Scientifique (CNRS), Service de physique de l'état condensé (SPEC - UMR3680), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), University of Central Florida [Orlando] (UCF), and CY Cergy Paris Université (CY)
Subjects: X-ray photoelectron spectroscopy, Materials science, Band gap, Scanning tunneling spectroscopy, FOS: Physical sciences, 02 engineering and technology, Substrate (electronics), 010402 general chemistry, 01 natural sciences, law.invention, Biomaterials, chemistry.chemical_compound, law, Electrochemistry, Surface diffusion, Condensed Matter - Materials Science, Materials Science (cond-mat.mtrl-sci), 021001 nanoscience & nanotechnology, Condensed Matter Physics, 2D materials, phosphorene, 0104 chemical sciences, Electronic, Optical and Magnetic Materials, Phosphorene, chemistry, Chemical physics, [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], Density functional theory, Scanning tunneling microscope, 0210 nano-technology, low temperature scanning tunneling microscopy
Abstract: International audience; We present an experimental investigation of a new polymorphic 2D single layer of phosphorus on Ag(111). The atomically-resolved scanning tunneling microscopy (STM) images show a new 2D material composed of freely-floating phosphorus pentamers organized into a 2D layer, where the pentamers are aligned in close-packed rows. The scanning tunneling spectroscopy (STS) measurements reveal a semiconducting character with a band gap of 1.20 eV. This work presents the formation at low temperature (LT) of a new polymorphic 2D phosphorus layer composed of a floating 2D pentamer structure. The smooth curved terrace edges and a lack of any clear crystallographic orientation with respect to the Ag(111) substrate at room temperature indicates a smooth potential energy surface that is reminiscent of a liquid-like growth phase. This is confirmed by density functional theory (DFT) calculations that find a small energy barrier of only 0.17 eV to surface diffusion of the pentamers (see Supplemental Material). The formation of extended, homogeneous domains is 2 a key ingredient to opening a new avenue to integrate this new 2D material into electronic devices.
Published: 2020
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45. Blue phosphorene reactivity on the Au(111) surface

Author: Yannick J. Dappe, Hamid Oughaddou, Abdelkader Kara, Azzedine Bendounan, Gérald Dujardin, Hanna Enriquez, Wei Zhang, Xuan Zhang, Andrew J. Mayne, Institut des Sciences Moléculaires d'Orsay (ISMO), Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), China University of Mining and Technology (CUMT), Synchrotron SOLEIL (SSOLEIL), Centre National de la Recherche Scientifique (CNRS), Service de physique de l'état condensé (SPEC - UMR3680), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), University of Central Florida [Orlando] (UCF), and CY Cergy Paris Université (CY)
Subjects: Materials science, DFT calculation, Bioengineering, 02 engineering and technology, 010402 general chemistry, 01 natural sciences, chemistry.chemical_compound, Lattice (order), Thermal, Atom, General Materials Science, Electrical and Electronic Engineering, two-dimensional materials, [PHYS.COND]Physics [physics]/Condensed Matter [cond-mat], Surface reactivity, Mechanical Engineering, General Chemistry, 021001 nanoscience & nanotechnology, phosphorene, 0104 chemical sciences, [CHIM.THEO]Chemical Sciences/Theoretical and/or physical chemistry, Crystallography, Phosphorene, chemistry, Mechanics of Materials, Step edges, 0210 nano-technology, low temperature scanning tunneling microscopy, Molecular beam epitaxy
Abstract: The synthesis of blue phosphorene by molecular beam epitaxy (MBE) has recently come under the spotlight due to its potential applications in electronic and optoelectronic devices. However, this synthesis remains a significant challenge. The surface reactivity between the P atoms and the Au atoms should be considered for the P/Au(111) system. In the MBE process, the temperature of the substrate is a key parameter for the growth of blue phosphorene. During the initial growth stage, irregularly shaped Phosphorus clusters grow on top of Au(111) surface at room temperature. When the substrate temperature is increased, these clusters transform into a phosphorene-like structure with a honeycomb lattice. An atom exchange reaction is observed between the P and first layer Au atoms under thermal activation at higher temperature, where the P atoms replace Au atoms to form a blue phosphorene structure within the top Au layer and at the step edges.
Published: 2020
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46. Selective control of molecule charge state on graphene using tip-induced electric field and nitrogen doping

Author: Sylvie Rousset, Van Dong Pham, Shobhana Narasimhan, Yann Girard, Amandine Bellec, Yannick J. Dappe, Mario Pelaez-Fernandez, Cyril Chacon, Vincent Repain, Sukanya Ghosh, Robert Sporken, Jérôme Lagoute, Frédéric Joucken, Laboratoire Matériaux et Phénomènes Quantiques (MPQ (UMR_7162)), Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Paul-Drude-Institut für Festkörperelektronik (PDI), Jawaharlal Nehru Centre for Advanced Scientific Research (JNCASR), Abdus Salam International Centre for Theoretical Physics [Trieste] (ICTP), Centre de Recherche en Physique de la Matière et du Rayonnement [Namur] (PMR), Université de Namur [Namur] (UNamur), Laboratoire de Photophysique Moléculaire (PPM), Université Paris-Sud - Paris 11 (UP11)-Centre National de la Recherche Scientifique (CNRS), Groupe Modélisation et Théorie (GMT), Institut Rayonnement Matière de Saclay (IRAMIS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Service de physique de l'état condensé (SPEC - UMR3680), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Paul-Drude-Institut für Festkörperelektronik, Université de Namur [Namur], Service de physique de l'état condensé (SPEC - UMR3680), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Institut Rayonnement Matière de Saclay (IRAMIS), and Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay
Subjects: Materials science, Ab initio, 02 engineering and technology, 01 natural sciences, law.invention, lcsh:Chemistry, law, Ab initio quantum chemistry methods, Electric field, 0103 physical sciences, Physics::Atomic and Molecular Clusters, lcsh:TA401-492, [CHIM]Chemical Sciences, General Materials Science, Physics::Chemical Physics, 010306 general physics, Graphene, Mechanical Engineering, Charge (physics), General Chemistry, 021001 nanoscience & nanotechnology, Condensed Matter Physics, Dipole, lcsh:QD1-999, Mechanics of Materials, Chemical physics, Density functional theory, lcsh:Materials of engineering and construction. Mechanics of materials, 0210 nano-technology, Voltage
Abstract: The combination of graphene with molecules offers promising opportunities to achieve new functionalities. In these hybrid structures, interfacial charge transfer plays a key role in the electronic properties and thus has to be understood and mastered. Using scanning tunneling microscopy and ab initio density functional theory calculations, we show that combining nitrogen doping of graphene with an electric field allows for a selective control of the charge state in a molecular layer on graphene. On pristine graphene, the local gating applied by the tip induces a shift of the molecular levels of adsorbed molecules and can be used to control their charge state. Ab initio calculations show that under the application of an electric field, the hybrid molecule/graphene system behaves like an electrostatic dipole with opposite charges in the molecule and graphene sub-units that are found to be proportional to the electric field amplitude, which thereby controls the charge transfer. When local gating is combined with nitrogen doping of graphene, the charging voltage of molecules on nitrogen is greatly lowered. Consequently, applying the proper electric field allows one to obtain a molecular layer with a mixed charge state, where a selective reduction is performed on single molecules at nitrogen sites.
Published: 2019
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47. Controlling Hydrogen-Transfer Rate in Molecules on Graphene by Tunable Molecular Orbital Levels

Author: Jérôme Lagoute, Amandine Bellec, Sylvie Rousset, Yann Girard, Alexander Smogunov, Rishav Harsh, Vincent Repain, Robert Sporken, Frédéric Joucken, Cyril Chacon, Yannick J. Dappe, Laboratoire Matériaux et Phénomènes Quantiques (MPQ (UMR_7162)), Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Centre de Recherche en Physique de la Matière et du Rayonnement [Namur] (PMR), Université de Namur [Namur] (UNamur), Laboratoire de Photophysique Moléculaire (PPM), Université Paris-Sud - Paris 11 (UP11)-Centre National de la Recherche Scientifique (CNRS), Service de physique de l'état condensé (SPEC - UMR3680), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Groupe Modélisation et Théorie (GMT), Institut Rayonnement Matière de Saclay (IRAMIS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Service de physique de l'état condensé (SPEC - UMR3680), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Institut Rayonnement Matière de Saclay (IRAMIS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, and Université de Namur [Namur]
Subjects: Molecular switch, Materials science, Dopant, Graphene, 02 engineering and technology, 010402 general chemistry, 021001 nanoscience & nanotechnology, 01 natural sciences, 0104 chemical sciences, law.invention, law, Chemical physics, [PHYS.COND.CM-GEN]Physics [physics]/Condensed Matter [cond-mat]/Other [cond-mat.other], Molecule, General Materials Science, Molecular orbital, Physical and Theoretical Chemistry, Scanning tunneling microscope, 0210 nano-technology, Excitation, Quantum tunnelling
Abstract: International audience; Molecular switches are building blocks of potential interest to store binary information, especially when they can be organized in periodic lattices. Among the variety of possible systems, switches based on hydrogen transfer are of special importance because they allow the switching operation to occur without severe conformational change that may interfere with neighboring molecular units. We have studied the excitation process of hydrogen transfer inside porphyrin molecules assembled on a graphene surface, using a low-temperature scanning tunneling microscope. We show that this hydrogen transfer is induced by an electronic resonant tunneling process through the molecular orbitals. Using nitrogen doping of graphene, we tune the rate of hydrogen transfer by shifting the molecular orbital energies owing to the charge transfer at nitrogen dopant sites in the graphene lattice. The control of the switching process allows the storage of information inside a molecular lattice, which is demonstrated by writing an artificial pattern inside a molecular island.
Published: 2019
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48. Importance of Epitaxial Strain at a Spin-Crossover Molecule–Metal Interface

Author: Yannick J. Dappe, Talal Mallah, Cynthia Fourmental, Jérôme Lagoute, Cristian Enachescu, Cyrille Barreteau, Sourav Mondal, Shobhana Narasimhan, Marie-Laure Boillot, Rajdeep Banerjee, Sylvie Rousset, Alessandro Coati, Amandine Bellec, Yann Girard, Vincent Repain, Cyril Chacon, Alexander Smogunov, Yves Garreau, Laboratoire Matériaux et Phénomènes Quantiques (MPQ (UMR_7162)), Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Jawaharlal Nehru Centre for Advanced Scientific Research (JNCASR), Synchrotron SOLEIL (SSOLEIL), Centre National de la Recherche Scientifique (CNRS), Institut de Chimie Moléculaire et des Matériaux d'Orsay (ICMMO), Université Paris-Sud - Paris 11 (UP11)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC), Laboratoire de chimie inorganique (LCI), Université Paris-Sud - Paris 11 (UP11)-Centre National de la Recherche Scientifique (CNRS), Department of Solid State and Theoretical Physics, Alexandru Ioan Cuza University of Iași [Romania], Groupe Modélisation et Théorie (GMT), Institut Rayonnement Matière de Saclay (IRAMIS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Service de physique de l'état condensé (SPEC - UMR3680), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Theoretical Sciences Unit, European Project: 766726,211587,COSMICS(2017), Université Paris-Sud - Paris 11 (UP11)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Service de physique de l'état condensé (SPEC - UMR3680), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Institut Rayonnement Matière de Saclay (IRAMIS), and Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay
Subjects: Diffraction, Materials science, Spin states, Spintronics, 02 engineering and technology, Substrate (electronics), 010402 general chemistry, 021001 nanoscience & nanotechnology, Epitaxy, 01 natural sciences, 0104 chemical sciences, Chemical physics, Spin crossover, [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], Molecule, General Materials Science, Physical and Theoretical Chemistry, 0210 nano-technology, Spin-½
Abstract: International audience; Spin-crossover molecules are very appealing for use in multifunctional spintronic devices because of their ability to switch between high-spin and low-spin states with external stimuli such as voltage and light. In actual devices, the molecules are deposited on a substrate, which can modify their properties. However, surprisingly little is known about such molecule–substrate effects. Here we show for the first time, by grazing incidence X-ray diffraction, that an FeII spin-crossover molecular layer displays a well-defined epitaxial relationship with a metal substrate. Then we show, by both density functional calculations and a mechanoelastic model, that the resulting epitaxial strain and the related internal pressure can induce a partial spin conversion at low temperatures, which has indeed been observed experimentally. Our results emphasize the importance of substrate-induced spin state transitions and raise the possibility of exploiting them.
Published: 2019
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49. Tuning spin filtering by anchoring groups in benzene derivative molecular junctions

Author: Yannick J. Dappe, Dongzhe Li, Alexander Smogunov, Service de Physique et de Chimie des Surfaces et Interfaces (SPCSI), Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Groupe Modélisation et Théorie (GMT), Institut Rayonnement Matière de Saclay (IRAMIS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Service de physique de l'état condensé (SPEC - UMR3680), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Service de physique de l'état condensé (SPEC - UMR3680), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Institut Rayonnement Matière de Saclay (IRAMIS), and Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay
Subjects: Molecular spintronics, Materials science, FOS: Physical sciences, Giant magnetoresistance, 02 engineering and technology, 01 natural sciences, Ab initio quantum chemistry methods, Mesoscale and Nanoscale Physics (cond-mat.mes-hall), 0103 physical sciences, General Materials Science, Molecular orbital, 010306 general physics, [PHYS]Physics [physics], Spin filtering, Spin polarization, Spintronics, Condensed Matter - Mesoscale and Nanoscale Physics, Conductance, Charge (physics), 021001 nanoscience & nanotechnology, Condensed Matter Physics, 3. Good health, NEGF-DFT calculations, Chemical physics, Electric current, 0210 nano-technology, Single
Abstract: One of the important issues of molecular spintronics is the control and manipulation of charge transport and, in particular, its spin polarization through single-molecule junctions. Using $ab$ $initio$ calculations, we explore spin-polarized electron transport across single benzene derivatives attached with six different anchoring groups (S, CH$_3$S, COOH, CNH$_2$NH, NC and NO$_2$) to Ni(111) electrodes. We find that molecule-electrode coupling, conductance and spin polarization (SP) of electric current can be modified significantly by anchoring groups. In particular, a high spin polarization (SP $>$ 80%) and a giant magnetoresistance (MR $>$ 140%) can be achieved for NO$_2$ terminations and, more interestingly, SP can be further enhanced (up to 90%) by a small voltage. The S and CH$_3$S systems, on the contrary, exhibit rather low SP while intermediate values are found for COOH and CNH$_2$NH groups. The results are analyzed in detail and explained by orbital symmetry arguments, hybridization and spatial localization of frontier molecular orbitals. We hope that our comparative and systematic studies will provide valuable quantitative information for future experimental measurements on that kind of systems and will be useful for designing high-performance spintronics devices., accpeted in J. Phys. Condens. Matter (2019)
Published: 2019
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50. Effect of Asymmetric Anchoring Groups on Electronic Transport in Hybrid Metal/Molecule/Graphene Single Molecule Junctions

Author: Yannick J. Dappe, Qian Zhang, Jingyao Ye, Cezhou Zhao, Chun Zhao, Yinqi Fan, Li Yang, Richard J. Nichols, Chunhui He, Department of Engineering Sciences and Applied Mathematics, Northwestern University, University of Liverpool, Department of Electrical Engineering and Electronics, Groupe Modélisation et Théorie (GMT), Institut Rayonnement Matière de Saclay (IRAMIS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Service de physique de l'état condensé (SPEC - UMR3680), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Sch Biol & Chem Sci, Queen Mary University of London (QMUL), Beijing University of Agriculture, Service de physique de l'état condensé (SPEC - UMR3680), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Institut Rayonnement Matière de Saclay (IRAMIS), and Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay
Subjects: [PHYS]Physics [physics], Materials science, Graphene, Conductance, Molecular electronics, 02 engineering and technology, 010402 general chemistry, 021001 nanoscience & nanotechnology, 01 natural sciences, Molecular physics, Atomic and Molecular Physics, and Optics, 0104 chemical sciences, law.invention, Electrical resistance and conductance, law, Electrode, Density functional theory, Physical and Theoretical Chemistry, Scanning tunneling microscope, [PHYS.COND]Physics [physics]/Condensed Matter [cond-mat], 0210 nano-technology, Quantum tunnelling
Abstract: International audience; A combined experimental and theoretical study on molecular junctions with asymmetry in both the electrode type and in the anchoring group type is presented. A scanning tunnelling microscope is used to create the "asymmetric" Au-S-(CH 2)n-COOH-graphene molecular junctions and determine their conductance. The measurements are combined with electron transport calculations based on density functional theory (DFT) to analyze the electrical conductance and its length attenuation factor from a series of junctions of different molecular length (n). These results show an unexpected trend with a rather high conductance and a smaller attenuation factor for the Au-S-(CH 2) n-COOH-graphene configuration compared to the equivalent junction with the "symmetrical" COOH contacting using the HOOC-(CH 2) n-COOH series. Owing to the effect of the graphene electrode, the attenuation factor is also smaller than the one obtained for Au/Au electrodes. These results are interpreted through the relative molecule/electrode couplings and molecular level alignments as determined with DFT calculations. In an asymmetric junction, the electrical current flows through the less resistive conductance channel, similarly to what is observed in the macroscopic regime.
Published: 2019
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