Atomic scale dynamics of ultrasmall germanium clusters

Starting from the gas phase, small clusters can be produced and deposited with huge flexibility with regard to composition, materials choice and cluster size. Despite many advances in experimental characterization, a detailed morphology of such clusters is still lacking. Here we present an atomic scale observation as well as the dynamical behaviour of ultrasmall germanium clusters. Using quantitative scanning transmission electron microscopy in combination with ab initio calculations, we are able to characterize the transition between different equilibrium geometries of a germanium cluster consisting of less than 25 atoms. Seven-membered rings, trigonal prisms and some smaller subunits are identified as possible building blocks that stabilize the structure. Ultrasmall clusters of atoms form the building blocks of many nanoscale materials. Using a combination of aberration-corrected transmission electron microscopy and numerical simulations, this study uncovers the geometry of these clusters in three dimensions.