Isabelle Braems

Abstract:

Supported nanomaterials are mainly studied for the modifications of electronic structure induced by their low dimension: Rashba effect, topological insulators, interface-induced gaps in graphene, bias/exchange effect, magnetic anisotropies... But the simultaneous control of composition, size, morphologies and chemical configurations raise many questions of thermodynamical order.<br />In this talk, we shall illustrate the equilibrium thermodynamics of pure or alloyed thin films, and supported nanowires and nanoparticles, built from transition metals, on a metallic surface. None of these objects forms a phase in the thermodynamical sense, - now widely named complexions- as their thermodynamic properties strongly rely on their environment (i.e. the underlying substrate and their companion particles for 1D and 2D systems). They can either be obtained in the monolayer or submonolayer regime, at equilibrium by gas deposition due to a strong segregation of one component (Ag/Cu, Ag/Ni...) or observed in situ via electrochemical co-deposition (Ni-Pd/Au(111)). Atomic-scale computations (Monte Carlo simulations, Quenched Molecular Dynamics) can be carried out to predict or comprehend their size, shape and composition, as a complement to Scanning Tunneling Microscopy studies. We shall in particular focus on the equilibrium size and composition distribution of a collection of finite supported particles. Statistics on a particle distribution will be linked to the much more studied characteristics of an isolated cluster, may it be free or isolated while experimentally investigated. The role of strain will be underlined via a comparison with experiments on heteroepitaxial systems (Ag/Cu, Ni-Pd/Au), and highly strained nanoislands (Ag/Ni(100)).<br />Keywords: Nanoislands; Thin Films; Atomic-Scale Simulations;