Institut Néel, CNRS & Université Grenoble Alpes, France
johann.coraux AT neel.cnrs.fr
Research areas: surface science; 2D materials; structural, electronic and magnetic properties of low-dimensional systems
Tools: UHV growth, STM, LEEM/PEEM, synchrotron X-ray diffraction, XMCD
Polycyclic carbon structures shaped with atomic precision
We explore various strategies for structuring sp2 carbon in 2D. Graphene for instance is a membrane which naturally forms ordered nanoripples when prepared on metallics substrate. 2D nanoporous networks are also targeted, by resorting to bottom-up synthesis with well-chosen molecular precursors. Small, flat polycyclic molecules with controllable structure can also be formed via pyrolysis reactions on metal surfaces. Our efforts focus on the understanding of the structural and collective excitations (electronic, vibrational) of these objects.
2D materials preparation on metals
There are countless possibilities for synthesizing 2D materials on substrates. We focus on the use of metal substrates, which have proven fruitful platforms for achieving high quality 2D materials, addressing their properties with the help of surface science tools, and manipulating these properties. Iridium, ruthenium, cobalt, copper, platinum, rhenium, are for instance used in our lab to prepare graphene, 2D silica, and transition metal dichalcogenides.
Hybrid systems based on graphene and transition metals
Graphene prepared on a metal is a platform for assembling a variety of hybrid systems where interface effect play prominent role. The mere situation of graphene on its substrate already yields numerous possibilities, to control the charge carrier density in graphene and create transparent-like or van der Waals-like electronic contacts. Depositing species on top of graphene further broadens the scope of properties within reach - we devote peculiar attention on catalytic and magnetic properties brought by organised metal nanoclusters. Finally, intercalation between graphene and its substrate makes it possible stabilise ultrathin layers, for instance to fully decouple graphene from its substrate, to achieve unconventional magnetic properties, or implement sizeable spin-orbit interactions in graphene-based systems.
Structural phase transitions in 2D materials
The 2D geometry stands out as a unique configuration in the study of phase transitions. Dimensionality effects indeed yield intriguing behaviours, and imaging of the surface in principle gives direct access to the evolution of all atoms in the material; besides control of the phase transition by external excitations is here optimum. We address two kinds of phase transitions, involving the competition of two atomic-scale characteristic lengths (the substrate and 2D material lattice parameters), or involving the intrinsic polymorphism of the material. We are especially interested in the formation and evolution of topological defects which accompany phase transitions.