Individual grain boundary characterisation via spectroscopy

Nearly all structural as well as functional materials are crystalline in nature, with individual crystallite (or grain) sizes ranging orders of magnitude from nanometers to millimeters depending on their purpose or use. The intersection of these grains, so-called grain boundaries (GBs) are the origin for a multitude of physical phenomena, such as mechanical response, magnetic coercivity, or thermal-/electrical conductivity, to name just a few. Therefore, altering the local geometrical or chemical structure of these GBs has become one of the go-to pathways to tailor and improve these properties in materials for modern applications. However, the process of such alterations is nearly always empirical, necessitating a large sweep of different synthesis parameter and subsequent experiments, without the fundamental knowledge of what exactly changed at these GBs. The aim of the present project is to establish a framework to determine the actual atomistic characteristics of individual GBs in their native state. This will be addressed by a novel combination of a unique micromechanical spectroscopy technique in conjunction with spatially resolved valence electron energy loss spectroscopy, both capable of probing sub-micrometer sized volumes. Additional ab initio simulations and advanced chemical tomography will complement these experiments and lead to an in-depth understanding of the fundamental physics of GBs.