Jérôme Lagoute

Bio: Jérôme Lagoute is an academic researcher from University of Paris. The author has contributed to research in topics: Scanning tunneling microscope & Graphene. The author has an hindex of 23, co-authored 83 publications receiving 1803 citations. Previous affiliations of Jérôme Lagoute include Centre national de la recherche scientifique & Paris Diderot University.

Localized state and charge transfer in nitrogen-doped graphene

Abstract: Nitrogen-doped epitaxial graphene grown on SiC(0001) was prepared by exposing the surface to an atomic nitrogen flux Using scanning tunneling microscopy and scanning tunneling spectroscopy (STS), supported by density functional theory (DFT) calculations, the simple substitution of carbon with nitrogen atoms has been identified as the most common doping configuration High-resolution images reveal a reduction of local charge density on top of the nitrogen atoms, indicating a charge transfer to the neighboring carbon atoms Local STS spectra clearly evidenced the energy levels associated with the chemical doping by nitrogen, localized in the conduction band Various other nitrogen-related defects have been observed The bias dependence of their topographic signatures demonstrates the presence of structural configurations more complex than substitution as well as hole doping © 2012 American Physical Society

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

Abstract: Spin cross-over molecules show the unique ability to switch between two spin states when submitted to external stimuli such as temperature, light or voltage. If controlled at the molecular scale, such switches would be of great interest for the development of genuine molecular devices in spintronics, sensing and for nanomechanics. Unfortunately, up to now, little is known on the behaviour of spin cross-over molecules organized in two dimensions and their ability to show cooperative transformation. Here we demonstrate that a combination of scanning tunnelling microscopy measurements and ab initio calculations allows discriminating unambiguously between both states by local vibrational spectroscopy. We also show that a single layer of spin cross-over molecules in contact with a metallic surface displays light-induced collective processes between two ordered mixed spin-state phases with two distinct timescale dynamics. These results open a way to molecular scale control of two-dimensional spin cross-over layers.

Tuning the Magnetic Anisotropy at a Molecule-Metal Interface.

Abstract: We demonstrate that a C(60) overlayer enhances the perpendicular magnetic anisotropy of a Co thin film, inducing an inverse spin reorientation transition from in plane to out of plane. The driving force is the (60)/Co interfacial magnetic anisotropy that we have measured quantitatively in situ as a function of the (60) coverage. Comparison with state-of-the-art ab initio calculations show that this interfacial anisotropy mainly arises from the local hybridization between (60) p(z) and Co d(z(2)) orbitals. By generalizing these arguments, we also demonstrate that the hybridization of (60) with a Fe(110) surface decreases the perpendicular magnetic anisotropy. These results open the way to tailor the interfacial magnetic anisotropy in organic-material-ferromagnet systems.

Manipulation and adsorption-site mapping of single pentacene molecules on Cu(111)

Abstract: Low-temperature scanning tunneling microscopy at $7\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ is used to study the adsorption and manipulation of single pentacene molecules on Cu(111). Controlled lateral translations of the molecule are performed along different high-symmetry directions of the substrate via attractive tip-molecule interactions. By means of a detailed site-mapping technique combining lateral manipulations of the molecule and of native substrate adatoms we determine the adsorptive configuration of the aromatic molecule. We find a planar adsorption geometry with the long molecular axis aligned with the close-packed Cu atom rows and the benzene units centered over hexagonal close-packed hollow sites of the substrate.

Large magnetoresistance through a single molecule due to a spin-split hybridized orbital.

Abstract: Using organic materials in spintronic devices raises a lot of expectation for future applications due to their flexibility, low cost, long spin lifetime, and easy functionalization. However, the interfacial hybridization and spin polarization between the organic layer and the ferromagnetic electrodes still has to be understood at the molecular scale. Coupling state-of-the-art spin-polarized scanning tunneling spectroscopy and spin-resolved ab initio calculations, we give the first experimental evidence of the spin splitting of a molecular orbital on a single non magnetic C(60) molecule in contact with a magnetic material, namely, the Cr(001) surface. This hybridized molecular state is responsible for an inversion of sign of the tunneling magnetoresistance depending on energy. This result opens the way to spin filtering through molecular orbitals.

The Chemical Structure of a Molecule Resolved by Atomic Force Microscopy

Abstract: Resolving individual atoms has always been the ultimate goal of surface microscopy. The scanning tunneling microscope images atomic-scale features on surfaces, but resolving single atoms within an adsorbed molecule remains a great challenge because the tunneling current is primarily sensitive to the local electron density of states close to the Fermi level. We demonstrate imaging of molecules with unprecedented atomic resolution by probing the short-range chemical forces with use of noncontact atomic force microscopy. The key step is functionalizing the microscope’s tip apex with suitable, atomically well-defined terminations, such as CO molecules. Our experimental findings are corroborated by ab initio density functional theory calculations. Comparison with theory shows that Pauli repulsion is the source of the atomic resolution, whereas van der Waals and electrostatic forces only add a diffuse attractive background.

Nano-architectures by covalent assembly of molecular building blocks

Abstract: The construction of electronic devices from single molecular building blocks, which possess certain functions such as switching or rectifying and are connected by atomic-scale wires on a supporting surface, is an essential goal of molecular electronics1. A key challenge is the controlled assembly of molecules into desired architectures by strong, that is, covalent, intermolecular connections2, enabling efficient electron transport3 between the molecules and providing high stability4. However, no molecular networks on surfaces ‘locked’ by covalent interactions have been reported so far. Here, we show that such covalently bound molecular nanostructures can be formed on a gold surface upon thermal activation of porphyrin building blocks and their subsequent chemical reaction at predefined connection points. We demonstrate that the topology of these nanostructures can be precisely engineered by controlling the chemical structure of the building blocks. Our results represent a versatile route for future bottom-up construction of sophisticated electronic circuits and devices, based on individual functionalized molecules.

Molecular architectonic on metal surfaces.

Abstract: The engineering of highly organized systems from instructed molecular building blocks opens up new vistas for the control of matter and the exploration of nanodevice concepts. Recent investigations demonstrate that well-defined surfaces provide versatile platforms for steering and monitoring the assembly of molecular nanoarchitectures in exquisite detail. This review delineates the principles of noncovalent synthesis on metal substrates under ultrahigh vacuum conditions and briefly assesses the pertaining terminology-self-assembly, self-organization, and self-organized growth. It presents exemplary scanning-tunneling-microscopy observations, providing atomistic insight into the self-assembly of organic clusters, chains, and superlattices, and the metal-directed assembly of low-dimensional coordination architectures. This review also describes hierarchic-assembly protocols leading to intricate multilevel order. Molecular architectonic on metal surfaces represents a versatile rationale to realize structurally complex nanosystems with specific shape, composition, and functional properties, which bear promise for technological applications.

Single-molecule junctions beyond electronic transport

Abstract: This Review describes emerging techniques for characterizing the fundamental properties of molecular junctions besides electronic transport. The idea of using individual molecules as active electronic components provided the impetus to develop a variety of experimental platforms to probe their electronic transport properties. Among these, single-molecule junctions in a metal–molecule–metal motif have contributed significantly to our fundamental understanding of the principles required to realize molecular-scale electronic components from resistive wires to reversible switches. The success of these techniques and the growing interest of other disciplines in single-molecule-level characterization are prompting new approaches to investigate metal–molecule–metal junctions with multiple probes. Going beyond electronic transport characterization, these new studies are highlighting both the fundamental and applied aspects of mechanical, optical and thermoelectric properties at the atomic and molecular scales. Furthermore, experimental demonstrations of quantum interference and manipulation of electronic and nuclear spins in single-molecule circuits are heralding new device concepts with no classical analogues. In this Review, we present the emerging methods being used to interrogate multiple properties in single molecule-based devices, detail how these measurements have advanced our understanding of the structure–function relationships in molecular junctions, and discuss the potential for future research and applications.