Structural defects in transition metal dichalcogenide core-shell architectures

Curvature presents a powerful approach to design atomic structure and tailor material properties in atomically thin transition metal dichalcogenides (TMDs). The emerging TMD core-shell architecture, in which a multilayer TMD shell encapsulates a curved nanoparticle core, presents the opportunity to controllably induce defects into a TMD crystal by strategically constructing the shape of the underlying core. However, harnessing this potential platform first requires robust characterization of the unique structural features present in the core-shell architecture. To this end, transmission electron microscopy (TEM) and scanning TEM (STEM) are particularly powerful tools for direct structural characterization of 2D materials with a high spatial resolution and precision. Here, we reveal and describe defects inherently present in the TMD core-shell architecture. We develop a comprehensive framework to classify the observed defects and discuss potential origins and implications of structural variations. We utilize high resolution S/TEM to reveal the relationship between defects and their associated strain fields. Furthermore, we demonstrate that TMD shells often possess a wide range of interlayer spacings with varied spatial distribution. By exploring the rich array of structural defects inherently present in the TMD core-shell architecture, we provide an important foundation to ultimately induce exotic properties in TMDs through sophisticated defect engineering.