Abstract text (incl. figure legends and references)

To design stable, active and selective catalyst materials, an understanding of a system's active sites is necessary. Today, many catalysts are based on materials decorated with either single metal atoms, clusters or nanoparticles, where the metal species act as reaction hubs in the catalytic process. It is known that the catalytic activity of particle based catalysts often correlates with the particle size, structure and morphology [1]. Despite this, there are not many experimental studies showing atomically resolved structural information about supported nanoparticles, and those that do are usually focused on larger particles [2, 3]. This study aims at revealing differences in the particle-support interface and particle structure of small oxide supported metal particles with diameters in the range of 1-3 nm.

Samples were prepared by dropping a dispersion of methanol with grinded catalyst powder onto regular TEM grids. Metal species were then deposited directly onto the grid by sputtering giving rise to a natural particle growth process by diffusion on the support surface. The samples are imaged with sub-Ångström spatial resolution in a probe-corrected FEI Titan Themis S/TEM microscope operated at 300 kV. High-angle annular dark-field (HAADF) STEM was chosen as imaging mode because of the incoherent nature of the signal. The inherent Z-contrast of HAADF-STEM along with the lack of Bragg diffraction contrast makes for easy image interpretation, especially useful for smaller particles with larger atomic number (Z) than the supporting material. Images were formed by aligning and summing a series of fast scans to limit the electron dose and the influence of sample drift.

We observe changes in particle shape from hemispherical to more facetted truncated octahedral-like shapes with increasing particle size, and also report the preferential orientation relations between particle and support. For particles with a favorable orientation in regards to visibility of atomic columns, the analysis was taken further and displacement and strain maps were calculated.

These results lay a foundation for further studies both in situ and ex situ. For example, to investigate electronic states in particles and interfaces by electron energy loss spectroscopy (EELS), but also to study particle behavior in situ in different gas environments and at different temperatures.