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Supported metal particles probed individually: An STM study Niklas Nilius1 1 Department of Physics, University of Oldenburg, Germany [email protected] Metal deposits on oxide supports are the active chemical elements in most heterogeneous catalysts and therefore in the focus of research for decades. Their characterization is often realized by non-local spectroscopic techniques, which generates problems due to the unavoidable size and shape distribution of particles on surfaces. The scanning tunneling microscope (STM) enables a local view on metal particles and provides a versatile toolbox to probe their atomic structure, electronic properties as well as optical response. In my talk, I survey multiple characterization schemes of metal particles with the STM. Using thin-film oxide supports, e.g. MgO, the nucleation and growth regime of ad-metals is examined, putting special emphasis on the role of oxide defects. I demonstrate how strain patterns arising in oxide films can be exploited to produce self-assembled particle arrays with high quality . Conductance spectroscopy with the STM is the method of choice to probe the electronic structure of metal deposits. In the size limit below 100 atoms, the particles are governed by quantum-well states, the energy and orbital shape of which can be approximated with simple particle-in-a-box models . A particularly interesting class of electronic states develops at the boundary of metal deposits that host excess charges due to electron exchange with the support. The states are highly susceptible to interact with adsorbates and are of relevance for the chemical response of the ad-particles. I will discuss how small shifts in the energy of these states can be used to analyze the nature of molecule-metal interactions, being either of physisorptive or chemisorptive character . A short outlook into possibilities to probe the optical properties of single metal particles with STM luminescence-spectroscopy will conclude my talk. (a) Topographic and (b) conductance maps of an Au particle on MgO/Ag(001), showing the bias evolution of standing-wave patterns inside the island (11×11 nm2).  S. Benedetti , F. Stavale , S. Valeri , C. Noguera, H.-J. Freund , J. Goniakowski, N. Nilius, Adv. Funct. Mat. 23, 75 (2013).  X. Lin, N. Nilius, H.-J. Freund, M. Walter, P. Frondelius, K. Honkala, H. Häkkinen, Phys. Rev. Lett. 102, 206801 (2009).  C. Stiehler, F. Calaza, W.-D. Schneider, N. Nilius, H.-J. Freund, Phys. Rev. Lett. 115, 036804 (2015).