Energy-Dispersive X-Ray Spectroscopy of Atomically Thin Semiconductors and Heterostructures

We report the implementation of energy-dispersive x-ray spectroscopy for high-resolution inspection of layered semiconductors in the form of atomically thin transition metal dichalcogenides down to the monolayer limit. The technique is based on a scanning electron microscope equipped with a silicon drift detector for energy-dispersive x-ray analysis. By optimizing operational parameters in numerical simulations and experiments, we achieve layer-resolving sensitivity for few-layer crystals down to the monolayer, and demonstrate elemental composition profiling in vertical and lateral heterobilayers of transition metal dichalcogenides. The technique can be straightforwardly applied to other layered two-dimensional materials and van der Waals heterostructures, thus expanding the experimental toolbox for quantitative characterization of layer number, atomic composition, or alloy gradients for atomically thin materials and devices.