Advancements in X-ray photoemission electron microscopy applied to thin film magnetism, 2D materials and molecular interfaces

Photoemission Electron Microscopy (PEEM) is a powerful and versatile full-field imaging technique based on the cathode lens, achieving lateral resolution down to ten nanometre range at the state of the art. In modern times, it has flourished at synchrotrons, where it has become one of the most sought-after microscopy tools, often referred to as XPEEM. By employing high-intensity, tunable sources of polarised soft X-ray radiation, PEEM enables absorption and photoemission spectroscopy at high lateral and elemental resolution, while also offering sensitivity to the local chemical, electronic, and magnetic structure. To date, surface and thin film magnetism has been one of the most prominent applications of synchrotron PEEM, with current research focusing on domain morphology in nanowires and nanostructures, exotic spin configurations, as well as spin manipulation and transport. On the other hand, the area where this technique has made the most remarkable progress is that of two-dimensional materials, beginning with graphene and rapidly expanding to the broader class of transition metal dichalcogenides. A rich variety of XPEEM applications is reviewed here, emphasising the usefulness of a multimodal experimental approach involving its parent technique, low-energy electron microscopy. XPEEM's ability to perform angle- and spin-resolved photoemission is highlighted as key to providing direct access to the electronic structure, with significant potential for studying a wide range of materials exhibiting quantum or topological properties. Finally, photoemission orbital tomography is introduced, with a focus on its capability to access the electronic structure of complex molecular interfaces at surfaces.