Atomic-Scale Mapping of Oxide Surface Reactivity Udo D. Schwarz, Yale University, DMR 0806893

1. Atomic-Scale Mapping of Oxide Surface ReactivityUdo D. Schwarz, Yale University, DMR 0806893 Mapping surface reactivity at the atomic scale is important for revealing reaction mechanisms of solid state catalysts. Using our low temperature, ultrahigh vacuum probe microscope, we are able to quantify the physical, chemical, and electric interactions between a single atom terminated tip and a surface in three dimensions [1]. The example [Cu3O2 surface phase of Cu(001)] shows how the tip can record the 3D force field of a surface by scanning in a 3D grid. A metallic tip allows quantification of the reactivity of O atoms while the simultaneously recorded tunneling current reveals the Cu sites. Together, the data show how Cu defects (arrows) influence the reactivity of the oxygen atoms. Principle of 3D-AFM: Front atom of a tip probes three-dimensional surface force field of Cu3O2 Force Channel: Surface reactivity of O atoms Current Channel: Charge density at Cu sites [1] M. Z. Baykara, T. C. Schwendemann, E. I. Altman, and U. D. Schwarz, Advanced Materials 22, 2838 (2010)

2. Atomic-Scale Mapping of Oxide Surface Reactivity Udo D. Schwarz, Yale University, DMR 0806893 Tip models used for simulations (selection): • International collaboration broadens impact in research and education: • Through the collaboration with our Spanish partner (Perez group, Madrid), we can identify the nature of the interactions probed • Simulations confirm that a metallic tip explains observed contrasts in both force and current channels • NSF-supported student exchange enables the Yale graduate student doing the experiments to become immersed in simulations in Madrid Force-distance curves calculated with all-metal tip at color-coded symmetry points: Good agreement! Simulation of current map with all-metal tip: Good agreement!