Surfaces, Spectroscopies and Modeling group (SUPREME)

(a) Tunnel conductance map (LDOS) measured by STS on a Ag nanopyramid of few nm size enlightening quantum well states

Inner view of the spin-ARPES set-up showing a Ag(111) sample mounted on the helium flux cryo-manipulator, the capillary of the UV lamp extracting the photons and the electrostatic entrance lenz of the photoelectron analyzer

(b) Fermi surface of Ru(0001) measured by ARPES

Fermi surface of Ru(0001) measured on this experimental set-up

(c) DFT calculated potential energy surfaces (color scale) for hydrogen adsorption on complex intermetallic Al13Co4 for monoclinic (-210) (top) and orthorhombic (010) (bottom) orientations

Last publications

Van der Waals epitaxy of Weyl-semimetal Td-WTe2
Alexandre Llopez, Frédéric Leroy, Calvin Tagne-Kaegom, Boris Croes, Adrien Michon, Chiara Mastropasqua, Mohamed Al Khalfioui, Stefano Curiotto, Pierre Müller, Andrés Saùl, Bertrand Kierren, Geoffroy Kremer, Patrick Le Fèvre, François Bertran, Yannick Fagot-Revurat, Fabien Cheynis
ACS Applied Materials & Interfaces, 2024, ⟨10.1021/acsami.4c00676⟩
Gap collapse and flat band induced by uniaxial strain in 1T-TaS2
Christopher W. Nicholson, Francesco Petocchi, Bjoern Salzmann, Catherine Witteveen, Maxime Rumo, Geoffroy Kremer, Oleh Ivashko, Fabian von Rohr, Philipp Werner, Claude Monney
Physical Review B, 2024, 109 (3), pp.035167. ⟨10.1103/physrevb.109.035167⟩
Persistence of structural distortion and bulk band Rashba splitting in SnTe above its ferroelectric critical temperature
Frédéric Chassot, Aki Pulkkinen, Geoffroy Kremer, Tetiana Zakusylo, Gauthier Krizman, Mahdi Hajlaoui, J. Hugo Dil, Juraj Krempaský, Ján Minár, Gunther Springholz, Claude Monney
Nano Letters, 2024, 24 (1), pp.82-88. ⟨10.1021/acs.nanolett.3c03280⟩

Presentation

The group studies the properties of surfaces, interfaces and nanostructures. It is interested in materials with remarkable electronic properties due to their reduced dimensions at the nanometer scale, their original atomic structures, the exotic nature of their ground state, their phase change or their unique spectroscopic properties. These materials are prepared in situ by MBE or ex situ, in collaboration with partner teams. Their atomic and electronic structures are mainly studied by angle-resolved photoemission (ARPES) and microscopy / tunnel spectroscopy (STM / STS), as well as by ab initio methods based on density functional theory (DFT).

Complementary investigations are carry out on the CASSIOPEE and SIXS beamlines of the Synchrotron SOLEIL.

At the experimental level, the two complementary techniques – STM/STS – give access to the Local Density of States (LDOS) in the direct space. ARPES give access to the k-resolved band structure. All the spectroscopic measurements are done at low temperature to reach the ultimate energy resolution.

Owing to its longstanding experience in ultra-high vacuum, we elaborate ultra-thin films and nanostructured interfaces using molecular beam epitaxy (MBE).

The acquisition of a spin-ARPES set-up and a STM/STS one including the possibility to apply a magnetic field, allow probing spin-dependent electronic properties at the nanometric scale.

These materials are in situ synthetized by MBE or ex situ using standard chemical synthesis, or in collaboration with other groups in the laboratory (Intermetallic Compounds and Hybrid Materials; Materials with Thermoelectric Properties; Metallurgy and Surfaces; Materials with Thermoelectric Properties; Nanomaterials for Optics) and through national and international projects.

Besides the experimental approaches, modeling activities are carried out in the team. They are based on density functional theory. They contribute to the determination of the atomic and electronic structures of surfaces and interfaces. They deepen the understanding, at the fundamental level, of the surface properties. The systems of interest include, among other, complex intermetallic surfaces and ultra-thin films grown on a substrate, I.e. surfaces considered by our research group but also by the Metallurgy and Surfaces (203) group at IJL. These activities also benefit from several collaborations at the national and international levels.

Keywords

Scanning tunneling microscopy and spectroscop

Photoémission X et UV résolue en angle et en spin

2D materials

Molecular materials

Corrrelated systems

DFT calculations

Chemical reactivity

Surface and interface structures and properties

Research topics

Elaboration and characterization of electronic properties of 2D materials

As for graphene or hexagonal Boron Nitride, silicon and germanium oxides are synthetized in their monolayer/bilayer forms on a Ru(0001) substrate. As a monolayer it is chemisorbed with a strong electronic coupling to the substrate forming a metal/oxide interface. As a bilayer, the weak Van der Waals interactions involved allow its exfoliation and its use as a large gap insulator in heterostructures. These ultra-thin metal/oxide interfaces can be exfoliated, modified by inserting magnetic atoms or used to built non-volatil memories. In addition, we are studying topological materials or even Rashba ferroelectric materials in collaboration with local or national partners.

Projects:

ANR 2D Transformers, 2016-2020, MAT2D, 2019-2021 (IJL)

Thesis:

Ministery / Land 2017-2020, Thomas Pierron, Ministery 2020-2023, Calvin Tagne-Kaegom

Article :

Electronic Band Structure of Ultimately Thin Silicon Oxide on Ru(0001), Kremer et al., ACS Nano 2019, 13, 4720.

Elaboration and characterization of electronic properties of molecular network self-organized on metallic surfaces

Ullmann catalytic process is used to synthetize molecular covalent networks on noble metals. One or two-dimensional polymeric architectures involving covalent bonding are characterized and are shown to behave as metallic/insulating nanowires for « all carbone » electronics. A part of this work is carried out in collaboration with the Giorgio Contini’s group (CNR-ISM,Rome, Italie) and Federico Rosei (INRS-Montréal, Canada). Kondo effect, in particular in molecular system is also a part of the research topic.

Project:

CFQCU, 2013-2015; PICS, 2015-2017; LUE (N4S), 2019-2020

Articles:

Quasi one-dimensional band dispersion and surface metallization in long-range ordered polymeric wires, Vasseur et al., Nat. Commun. 2016, 7, 10235.
Adsorption-Induced Kondo Effect in Metal-Free Phthalocyanine on 2HPc/Ag(111), Granet et al., J. Phys. Chem. C 2020, 124, 19, 10441–10452.

Charge and spin excitations, phase transitions in correlated materials

Electronic correlations, symmetry and topology are responsible for numerous singular electronic properties of exotic materials. Competition/coexistence of electronic correlations, Kondo physics and magnetism in correlated systems with d and f electrons are studied to reveal their singular properties (charge or spin ordering, superconductivity, Mott-Hubbard vs charge transfer insulators, heavy fermions, etc.). Several spectroscopic technics (ARPES, resonant PES, XMCD and high energy X-Rays PES) are combined to reveal in collaboration with Ashish Chainani (National Synchrotron Radiation Research Center, Taïwan)

Project:

PHC CNRS France/Taïwan 2019-2022

Thesis:

International Lorraine Université d’Excellence (LUE) program, 2019-2022, Bodry Tegomo

Articles:

Evidence for Weakly Correlated Oxygen Holes in the Highest-Tc Cuprate Superconductor Cuprate Superconductor HgBa2Ca2Cu3O8+δ, Chainani et al., Phys. Rev. Lett. 2017, 119, 057001.
Band structure and Fermi surfaces of the reentrant ferromagnetic superconductor Eu(Fe 0.86Ir0.14)2As2, Xing et al., Phys. Rev. B 2017, 96, 174513.

Modeling : from surface structures to properties

The theoretical modeling of surface structures and properties are carried out at the atomic scale, by methods based on the density functional theory and sometimes coupled with other methods. Our approach aims to identify the mechanisms leading to the selection of specific termination planes, as well as the role of chemical bonds and the possible effects of segregation, etc. Modeling also provides a fundamental knowledge on the origin of the surface properties. For instance, the electronic structure has been shown to play a non negligible role on the weak wetting of complex intermetallic surfaces. Overall, our research acitivities include surface reactivity, oxidation, heterogeneous catalysis, with the aim to develop new materials for sustainable applications.

Projects:

ECMETAC
LIA-PACS2
COMETE (FEDER-FSE)
OXYQUASI (IJL)
IRN Aperiodic

Thesis:

IJL-Synchrotron Soleil co-tutelle, 2017-2020, Corentin Chatelier
International Lorraine Université d’Excellence (LUE) program in collaboration with the Josef Stefan Institute (Slovenia), 2019-2022, Thiago Trevizam-Dorini

Articles:

Pseudo-2-Fold Surface of the Al13Co4 Catalyst: Structure, Stability, and Hydrogen Adsorption, Corentin Chatelier et al., ACS Appl. Mater. Interfaces 2020, 12, 35, 39787–39797.
Catalytic activation of a non-noble intermetallic surface through nanostructuration under hydro-genation conditions revealed by atomistic thermodynamics, E. Gaudry et al., J. Mater. Chem. A, 2020,8, 7422-7431.

Know-how

Elaboration

Preparation of metallic/semiconducting substrates by ion bombardment/annealing cycles and/or direct current heating
Elaboration by molecular beam epitaxy (MBE): metallic nanostructures, alkaline or halogen doping, semiconducting surfaces, CVD/MBE combined graphene synthesis and metal insertion, self-assembled molecular architectures and polymers, reactive evaporation of molecular/atomic oxygen

Characterization

Surface structure determination using electron diffraction (RHEED, LEED) and chemical surface analysis by high resolution x-rays photoelectron spectroscopy (XPS)
Surface structure at the atomic scale and morphology by scanning tunneling microscopy (STM) and electronic properties by scanning tunneling spectroscopy (STS)
Band structure determination by angle-resolved photoemission spectroscopy (ARPES)
Modeling of electronic properties and spectroscopy (impurity models)
UHV instrumentation and set-up: combined MBE-STM / STS-Photoemission, combined micro-MBE/spin-ARPES in the framework of the D.A.U.M. Tube
Cryogenics