Abstract.

         A new experimental equipment called NANOPLAST was developed few years ago. It consists in three UHV chambers interconnected together and allows to investigate by scanning tunnelling　microscopy the evolution at the atomic scale of crystalline surfaces submitted to compressive strains (or stresses).For details,seenanoplast.pprime.fr/en/.The strain/strain curve can be acquiredsimultaneously and the temperature can be tuned from　approximately 50 to 650 K forin situ(i.e.scanning STM tip　always in contact with the surface) investigations or up to 1200 K forex situobservations.

        Two current fields of research pay our attention. (1) The first one is related to understand the elementary plastic mechanisms taking place in crystals. When plastically strained, interesting signatures appear at the free surface of crystals, called slip traces, those height is only about a few hundreds of picometers.The slip traces allow to investigate at the atomic scale the pathway of single dislocations (the structural defaults that are responsible of plasticity) gliding in their slip planes. These experimentalresults are of great interest to compare with what can be routinely obtained at the same scale by atomistic simulations　such as molecular dynamics or functional density theory^1,2. (2) The second one concerns the stress-induced evolution of surface atomicstructures to reach some surface patterns that could be of great interest for specific functional properties in the future. It can be for instance how does the chevron-like　Au(111) reconstruction evolve depending on the intensity and direction of stress inthe elastic regime^3,4 or how vicinal surfaces characterized by successive elementary atomic steps are destabilized by the gliding dislocations^5,6. In this case, the dislocations are using as nano-engineering tools to put the surface out of equilibrium.　

¹Douat et al.,Scripta Materialia 183 (2020)81

²Bonneville et al.,Modelling Simul. Mater. Sci. Eng.32 (2024)065021

³Chauraud et al., Surface Science 714 (2021) 121908.

⁴Chauraud et al.,Phys. Rev. B99(2019) 195404.

⁵Coupeau et al., Phys. Review B 93(2016) 041405.

⁶Coupeau et al., Acta Materialia 175 (2019) 206

Biography.

        Christophe COUPEAUis Professor in Materials Science at University of Poitiers, France.His research activity is related to a variety of problems in materials science concerned with plasticity, mechanical properties and stability, and failure phenomena in engineered-material systems. Our approach is based on the development of scanning probe microscopy enabling nano-scale surface features to be routinely analyzed,even under in situ deformation conditions. The investigation of the surface evolution under stress and the characterization at a nanometre scale of the surface effects allow a betterunderstanding of basic deformation mechanisms controlling deformation kinetics and may establish the foundation to propose and/or develop more reliable models for describing the elastic or plastic response of crystalline materials under stress. The worksextend from the mechanical properties of thin films and coatings to the study of variable temperature deformation of advanced bulk materials.