Exploring the atomic-scale dynamics of Fe3O4(001) at catalytically relevant temperatures using FastSTM

• FastSTM movies of a magnetite surface. • Direct observation of atomic-scale surface dynamics. • Point defects jump in distinctive zigzag path. • Step edge propagation in oxygen leads to healing of holes. Surfaces and interfaces of functional nanoscale materials are typically highly dynamic when employed at elevated temperatures. Both, lateral surface and vertical bulk exchange diffusion processes set in, which can be relevant for applications such as heterogeneous catalysis. Time-resolved scanning tunneling microscopy (STM) is being pushed to ever faster measurement modes to follow such dynamic phenomena in situ. Here, we present FastSTM movies monitoring a range of atomic-scale dynamics of a prototypical reducible oxide catalyst support, Fe 3 O 4 (001), at elevated temperatures. Antiphase domain boundaries between two domains of the reconstructed surface exhibit local mobility from around 350 K, while Fe-rich point defects, in a stable equilibrium with the bulk, appear to diffuse in a peculiar zigzag pattern above 500 K. Finally, exploiting the diffusivity of Fe interstitials, we follow the propagation of step edges in the topmost atomic layer of the Fe 3 O 4 (001) surface in an oxygen atmosphere.